Search tips
Search criteria

Results 1-25 (73)

Clipboard (0)

Select a Filter Below

Year of Publication
1.  Suppressor of cytokine signalling protein SOCS1 and UBP43 regulate the expression of type I interferon-stimulated genes in human microvascular endothelial cells infected with Rickettsia conorii 
Journal of Medical Microbiology  2013;62(Pt 7):968-979.
Rickettsia conorii, the causative agent of Mediterranean spotted fever, preferentially infects human microvascular endothelium and activates pro-inflammatory innate immune responses as evidenced by enhanced expression and secretion of cytokines and chemokines. Our recent studies reveal that human microvascular endothelial cells (HMECs) infected with R. conorii also launch ‘antiviral’ host defence mechanisms typically governed by type I interferons. To summarize, infected HMECs secrete IFN-β to activate STAT1 in an autocrine/paracrine manner and display increased expression of IFN-stimulated genes, for example ISG15, which in turn activate innate responses to interfere with intracellular replication of rickettsiae. We now present evidence that UBP43 and SOCS1, known negative regulators of JAK/STAT signalling, are also induced in R. conorii-infected HMECs, of which UBP43 but not SOCS1 functions to negatively regulate STAT1 activation. Interestingly, UBP43 induction is almost completely abolished in the presence of IFN-β-neutralizing antibody, implicating an important role for UBP43 as a feedback inhibitor for IFN-β-mediated STAT1 activation. In contrast, SOCS1 expression is only partially affected by IFN-β neutralization, implicating potential involvement of as-yet-unidentified IFN-independent mechanism(s) in SOCS1 induction during R. conorii infection. A number of IFN-stimulated genes, including ISG15, OAS1, MX1, IRF1, IRF9 and TAP1 are also induced in an IFN-β-dependent manner, whereas GBP1 remains unaffected by IFN-β neutralization. Increased STAT1 phosphorylation in HMECs subjected to UBP43 knockdown led to transcriptional activation of OAS1, MX1 and GBP1, confirming the negative regulatory role of UBP43. Although IRF1, IRF9 and TAP1 were induced by IFN-β, siRNA-mediated silencing of UBP43 or SOCS1 did not significantly affect their transcriptional activation. Expression of ISG15 was, however, increased in HMECs transfected with siRNA for UBP43 and SOCS1. Thus, unique regulatory patterns of induced expression of UBP43, SOCS1 and IFN-stimulated genes represent pathogen-specific responses underlying IFN-β-mediated host endothelial signalling during the pathogenesis of spotted fever group rickettsiosis.
PMCID: PMC3709555  PMID: 23558133
2.  Enteroaggregative Escherichia coli strain in a novel weaned mouse model: exacerbation by malnutrition, biofilm as a virulence factor and treatment by nitazoxanide 
Journal of Medical Microbiology  2013;62(Pt 6):896-905.
Enteroaggregative Escherichia coli (EAEC) is increasingly recognized as a common cause of diarrhoea in healthy, malnourished and immune-deficient adults and children. There is no reproducible non-neonatal animal model for longitudinal studies of disease mechanism or therapy. Using two strains of human-derived EAEC to challenge weaned C57BL/6 mice, we explored an in vivo model of EAEC infection in mice, in which disease was monitored quantitatively as the growth rate, stool shedding and tissue burden of organisms; nutritional status was varied, and a new class of therapeutics was assessed. A single oral challenge of EAEC strain 042 resulted in significant growth shortfalls (5–8 % of body weight in 12 days), persistent shedding of micro-organisms in stools [>103.2 c.f.u. (10 mg stool)−1 for at least 14 days] and intestinal tissue burden [~103 c.f.u. (10 mg tissue)−1 detectable up to 14 days post-challenge]. Moderate malnourishment of mice using a ‘regional basic diet’ containing 7 % protein and reduced fat and micronutrients heightened all parameters of infection. Nitazoxanide in subMIC doses, administered for 3 days at the time of EAEC challenge, lessened growth shortfalls (by >10 % of body weight), stool shedding [by 2–3 logs (10 mg stool)−1] and tissue burden of organisms (by >75 % in the jejunum and colon). Thus, weaned C57BL/6 mice challenged with EAEC is a convenient, readily inducible model of EAEC infection with three highly quantifiable outcomes in which disease severity is dependent on the nutritional status of the host, and which is modifiable in the presence of inhibitors of pyruvate ferredoxin oxidoreductase such as nitazoxanide.
PMCID: PMC3709553  PMID: 23475903
3.  Late acyltransferase genes lpxX and lpxL jointly contribute to the biological activities of Moraxella catarrhalis 
Journal of Medical Microbiology  2013;62(Pt 6):807-812.
Lipo-oligosaccharide (LOS) is a major surface component and virulence factor of the human respiratory pathogen Moraxella catarrhalis. Two late acyltransferase genes, lpxX and lpxL, have been identified involved in the incorporation of acyloxyacyl-linked secondary acyl chains into lipid A during M. catarrhalis LOS biosynthesis. In this study, a double mutant with a deletion of both the lpxX and lpxL genes in M. catarrhalis strain O35E was constructed and named O35ElpxXL. Structural analysis of lipid A showed that the O35ElpxXL mutant lacked two decanoic acids (10 : 0) and one dodecanoic (lauric) acid (12 : 0). In comparison with the O35E parental strain and the single mutants O35ElpxX and O35ElpxL, the double mutant O35ElpxXL displayed prominently decreased endotoxin content, reduced resistance to normal human serum and accelerated bacterial clearance at 0, 3 and 6 h after an aerosol challenge in a mouse model of bacterial pulmonary clearance. These results indicate that these two genes encoding late acyltransferases responsible for lipid A biosynthesis jointly contribute to the biological activities and pathogenicity of M. catarrhalis. The double mutant O35ElpxXL with dramatically reduced toxicity is proposed as a potential vaccine candidate against M. catarrhalis infections for further investigation.
PMCID: PMC3709554  PMID: 23475908
4.  Effects of ciprofloxacin on the expression and production of exotoxins by Clostridium difficile 
Journal of Medical Microbiology  2013;62(Pt 5):741-747.
Hypervirulent BI/NAP1/027 strains of Clostridium difficile have been associated with increased mortality of C. difficile infection (CDI). The emergence of highly fluoroquinolone (FLQ)-resistant BI/NAP1/027 strains suggests that FLQ exposure may be a risk factor for CDI development. However, the mechanism for this is not clear. We compared the effects of subinhibitory concentrations of ciprofloxacin on Toxin A and B gene expression and protein production in recent (strain 039) and historical (strain 5325) BI/NAP1/027 clinical isolates with high- and low-level ciprofloxacin resistance, respectively. In the highly ciprofloxacin-resistant isolate (strain 039), ciprofloxacin significantly and dose-dependently increased Toxin A gene expression and shifted its expression to earlier in its growth cycle; TcdB gene expression also increased but was less sensitive to low-dose ciprofloxacin. Maximal Toxin A/B production (4 ng ml−1) was increased twofold and occurred significantly earlier than in the untreated control. In strain 5325, ciprofloxacin at 0.25×MIC markedly increased both tcdA and tcdB expression but their temporal dynamics were unchanged. Maximal toxin production (250 ng ml−1) was reduced approximately threefold compared with that of the untreated control. These results demonstrate significant differences in ciprofloxacin-induced toxin gene expression and protein production among BI/NAP1/027 isolates, and offer a new paradigm for FLQ-associated CDI caused by recent, highly antibiotic-resistant strains.
PMCID: PMC3910449  PMID: 23429695
5.  Prevalence of enteroaggregative Escherichia coli and its virulence-related genes in a case–control study among children from north-eastern Brazil 
Journal of Medical Microbiology  2013;62(Pt 5):683-693.
Enteroaggregative Escherichia coli (EAEC) is an important agent that causes endemic and epidemic diarrhoeal diseases worldwide. Several EAEC virulence-related genes (VRGs) have been described but their role in the clinical outcome of infection is not completely defined. This study investigated the prevalence of EAEC and potential associations of its VRGs with risk of or protection from diarrhoeal diseases in children from urban communities in north-eastern Brazil. The case–control study included 166 children, who had their stools evaluated for the EAEC diagnostic genes (aaiC and aatA) using PCR. Positive samples were further analysed by multiplex PCR and identified 18 VRGs. EAEC was found in the same proportion in both groups (41 %). The plasmid-borne gene encoding a hexosyltransferase homologue (capU) was the most frequently detected (89.6 %), followed by dispersin protein (aap, 58.2 %) and EAEC HilA homologue (eilA, 57.8 %). The AAF/III fimbrial subunit (agg3A) gene was observed at lower frequency (1.5 %). Plasmid-encoded toxin (pet) or AAF/II fimbrial subunit (aafA) was associated significantly with disease. AAF/IV fimbrial subunit (agg4A) or hypothetical plasmid-encoded haemolysin (orf61) was detected significantly more in controls than in children with diarrhoea. In addition, one set of genes in combination, aaiC and agg3/4C but lacking agg4A and orf61, was associated with diarrhoea cases; and another one, orf61 in the absence of pet and aafA, was correlated with control children. These data confirm a high prevalence, endemicity and heterogeneity of EAEC strains in the developing urban areas of north-eastern Brazil. Statistical correlation between cases and controls was seen with either isolated or combined sets of genes, suggesting that the pathophysiology of EAEC infection involves a complex and dynamic modulation of several VRGs.
PMCID: PMC3709657  PMID: 23429698
6.  Analysis of gene expression changes in Trichophyton rubrum after skin interaction 
Journal of Medical Microbiology  2014;63(Pt 5):642-648.
Trichophyton rubrum, an anthropophilic and cosmopolitan fungus, is the most common agent of superficial mycoses. In this study, T. rubrum infection was modelled by adding human skin sections to a limited medium containing glucose and cDNA microarrays were used to monitor T. rubrum gene expression patterns on a global level. We observed that exposure to human skin resulted in upregulation of the expression levels of T. rubrum genes related to many cellular and biological processes, including transcription and translation, metabolism and secondary transport, the stress response, and signalling pathways. These results provide a reference set of T. rubrum genes whose expression patterns change upon infection and reveal previously unknown genes that most likely correspond to proteins that should be considered as virulence factor candidates and potential new drug targets for T. rubrum infection.
PMCID: PMC4042497  PMID: 24586032
7.  Drug response and genetic properties of Vibrio cholerae associated with endemic cholera in north-eastern Thailand, 2003–2011 
Journal of Medical Microbiology  2013;62(Pt 4):599-609.
Cholera, caused by Vibrio cholerae, results in significant morbidity and mortality worldwide, including Thailand. Representative V. cholerae strains associated with endemic cholera (n = 32), including strains (n = 3) from surface water sources, in Khon Kaen, Thailand (2003–2011), were subjected to microbiological, molecular and phylogenetic analyses. According to phenotypic and related genetic data, all tested V. cholerae strains belonged to serogroup O1, biotype El Tor (ET), Inaba (IN) or Ogawa (OG). All of the strains were sensitive to gentamicin and ciprofloxacin, while multidrug-resistant (MDR) strains showing resistance to erythromycin, tetracycline, trimethoprim/sulfamethoxazole and ampicillin were predominant in 2007. V. cholerae strains isolated before and after 2007 were non-MDR. All except six diarrhoeal strains possessed ctxA and ctxB genes and were toxigenic altered ET, confirmed by MAMA-PCR and DNA sequencing. Year-wise data revealed that V. cholerae INET strains isolated between 2003 and 2004, plus one strain isolated in 2007, lacked the RS1 sequence (rstC) and toxin-linked cryptic plasmid (TLC)-specific genetic marker, but possessed CTXCL prophage genes ctxBCL and rstRCL. A sharp genetic transition was noted, namely the majority of V. cholerae strains in 2007 and all in 2010 and 2011 were not repressor genotype rstRCL but instead were rstRET, and all ctx+ strains possessed RS1 and TLC-specific genetic markers. DNA sequencing data revealed that strains isolated since 2007 had a mutation in the tcpA gene at amino acid position 64 (N→S). Four clonal types, mostly of environmental origin, including subtypes, reflected genetic diversity, while distinct signatures were observed for clonally related, altered ET from Thailand, Vietnam and Bangladesh, confirmed by distinct subclustering patterns observed in the PFGE (NotI)-based dendrogram, suggesting that endemic cholera is caused by V. cholerae indigenous to Khon Kaen.
PMCID: PMC3709540  PMID: 23319310
8.  Adhesin genes and serum resistance in Haemophilus influenzae type f isolates 
Journal of Medical Microbiology  2013;62(Pt 4):514-524.
The incidence of invasive infections due to Haemophilus influenzae has decreased significantly in developed countries with high rates of vaccination against H. influenzae serotype b (Hib). This vaccine provides no protection against H. influenzae serotype f (Hif), typically associated with invasive infections in adults with chronic disease and/or immunodeficiency, and rarely in otherwise healthy adults and children. The specific properties of Hif associated with virulence remain largely uncharacterized. A panel of 26 Hif strains consisting of both invasive disease-associated and mucosal surface non-invasive disease-associated isolates was surveyed by DNA fingerprinting, biotyping and PCR detection of hmw1, hmw2, hsf, the hif fimbrial locus and the lipo-oligosaccharide (LOS) biosynthetic island, and assessment of β-lactamase expression and determination of resistance to the bactericidal activity of normal adult human serum. Repetitive sequence-based PCR fingerprinting differentiated the 26 strains into three clusters, with the majority of isolates (22/26, 84.6 %) clustered into a single indistinguishable group. Most isolates (24/26, 92.3 %) were of biotype I and two isolates produced β-lactamase with detection of a conjugative plasmid, and the isolates displayed a range of resistances to the bactericidal activity of human serum. All 26 isolates carried the adhesin hsf, 21 carried a partial hif fimbrial operon and 4 had the adhesin genes hmw1/2. A LOS biosynthetic island was detected in 20 isolates consisting of the genes lic2BC. It was concluded that Hif has many recognized virulence properties and comprises a relatively homogeneous group independent of the anatomical source from which it was isolated.
PMCID: PMC3709541  PMID: 23242639
9.  Streptococcus equi subsp. zooepidemicus meningitis in Peru 
Journal of Medical Microbiology  2013;62(Pt 2):335-337.
A 59-year-old man with a history of fever, unsteadiness, hemiparesis, motor aphasia and consciousness disturbance was hospitalized for Streptococcus equi subsp. zooepidemicus meningitis. He denied contact with farm animals, but had a practice of consuming unpasteurized goats’ cheese from an uncertain source.
PMCID: PMC3709539  PMID: 23105024
10.  Human impact on the microbiological water quality of the rivers 
Journal of Medical Microbiology  2013;62(Pt 11):1635-1640.
Microbiological contamination is an important water-quality problem worldwide. Human impact on this category of contamination is significant and several human-related activities, and also the population explosion, have affected and are still affecting dramatically the aquatic environment. Extensive industrialization and agriculture have led to increased pollution and hydromorphological changes in many river basins. The Danube river is one of the most affected by these changes where human involvement is undeniable, and subsequently, the Danube Delta Biosphere Reserve became one of the most vulnerable ecosystems. This review is an attempt to analyse the microbiological contamination and to identify the major role human activities play in altering the water quality of the rivers.
PMCID: PMC3809112  PMID: 23813274
11.  Characterization of a multi-component anthrax vaccine designed to target the initial stages of infection as well as toxaemia 
Journal of Medical Microbiology  2012;61(Pt 10):1380-1392.
Current vaccine approaches to combat anthrax are effective; however, they target only a single protein [the protective antigen (PA) toxin component] that is produced after spore germination. PA production is subsequently increased during later vegetative cell proliferation. Accordingly, several aspects of the vaccine strategy could be improved. The inclusion of spore-specific antigens with PA could potentially induce protection to initial stages of the disease. Moreover, adding other epitopes to the current vaccine strategy will decrease the likelihood of encountering a strain of Bacillus anthracis (emerging or engineered) that is refractory to the vaccine. Adding recombinant spore-surface antigens (e.g. BclA, ExsFA/BxpB and p5303) to PA has been shown to augment protection afforded by the latter using a challenge model employing immunosuppressed mice challenged with spores derived from the attenuated Sterne strain of B. anthracis. This report demonstrated similar augmentation utilizing guinea pigs or mice challenged with spores of the fully virulent Ames strain or a non-toxigenic but encapsulated ΔAmes strain of B. anthracis, respectively. Additionally, it was shown that immune interference did not occur if optimal amounts of antigen were administered. By administering the toxin and spore-based immunogens simultaneously, a significant adjuvant effect was also observed in some cases. Thus, these data further support the inclusion of recombinant spore antigens in next-generation anthrax vaccine strategies.
PMCID: PMC3541767  PMID: 22767539
12.  Characterization of Corynebacterium species in macaques 
Journal of Medical Microbiology  2012;61(Pt 10):1401-1408.
Bacteria of the genus Corynebacterium are important primary and opportunistic pathogens. Many are zoonotic agents. In this report, phenotypic (API Coryne analysis), genetic (rpoB and 16S rRNA gene sequencing), and physical methods (MS) were used to distinguish the closely related diphtheroid species Corynebacterium ulcerans and Corynebacterium pseudotuberculosis, and to definitively diagnose Corynebacterium renale from cephalic implants of rhesus (Macaca mulatta) and cynomolgus (Macaca fascicularis) macaques used in cognitive neuroscience research. Throat and cephalic implant cultures yielded 85 isolates from 43 macaques. Identification by API Coryne yielded C. ulcerans (n = 74), Corynebacterium pseudotuberculosis (n = 2), C. renale or most closely related to C. renale (n = 3), and commensals and opportunists (n = 6). The two isolates identified as C. pseudotuberculosis by API Coryne required genetic and MS analysis for accurate characterization as C. ulcerans. Of three isolates identified as C. renale by 16S rRNA gene sequencing, only one could be confirmed as such by API Coryne, rpoB gene sequencing and MS. This study emphasizes the importance of adjunct methods in identification of coryneforms and is the first isolation of C. renale from cephalic implants in macaques.
PMCID: PMC3541768  PMID: 22723254
13.  Natural and experimental Helicobacter pullorum infection in Brown Norway rats 
Journal of Medical Microbiology  2012;61(Pt 9):1319-1323.
Helicobacter pullorum is an enterohepatic Helicobacter species (EHS) that was recently reported as a naturally acquired infection in mice. Faecal samples from 18 out of 20 Brown Norway (BN) rats, housed in the same barrier as the H. pullorum-infected mice, were positive for H. pullorum using species-specific PCR. In addition, we determined whether H. pullorum was able to persistently colonize the gastrointestinal tract and/or biliary tree and elicit tissue inflammation as well as a serum IgG response in BN rats. Six (four male, two female) 6-week-old, H. pullorum-negative BN rats were orally dosed with 4×108 c.f.u. of H. pullorum every other day for a total of three doses. At 2 weeks post-infection, all rats were H. pullorum-positive by faecal PCR. Five out of the six BN rats remained H. pullorum-positive for the entire 30 week study. PCR analysis of tissue collected at necropsy confirmed that the colon and caecum were the primary sites of H. pullorum colonization. Rats that were persistently colonized by H. pullorum had a sustained H. pullorum-specific IgG response measured by ELISA. Intestinal or hepatic pathology associated with H. pullorum infection was not noted. To our knowledge, this is the first report documenting that rats can be persistently colonized with an EHS that also infects humans.
PMCID: PMC3541769  PMID: 22580914
14.  Genetic diversity of locus of enterocyte effacement genes of enteropathogenic Escherichia coli isolated from Peruvian children 
Journal of Medical Microbiology  2012;61(Pt 8):1114-1120.
The aim of this study was to determine the frequency and allele associations of locus of enterocyte effacement encoded esp and tir genes among 181 enteropathogenic Escherichia coli (EPEC) strains (90 diarrhoea-associated and 91 controls) isolated from Peruvian children under 18 months of age. We analysed espA, espB, espD and tir alleles by PCR-RFLP. EPEC strains were isolated with higher frequency from healthy controls (91/424, 21.7 %) than from diarrhoeal samples (90/936, 9.6 %) (P<0.001); 28.9 % of diarrhoeal and 17.6 % of control samples were typical EPEC (tEPEC). The distribution of espA alleles (alpha, beta, beta2 and gamma) and espD alleles (alpha, beta, gamma and a new variant, espD-N1) between tEPEC and atypical EPEC (aEPEC) was significantly different (P<0.05). espD-alpha was more common among acute episodes (P<0.05). espB typing resulted in five alleles (alpha, beta, gamma and two new sub-alleles, espB-alpha2 and espB-alpha3), while tir-beta and tir-gamma2 were the most common intimin receptor subtypes. Seventy-two combinations of espA, espB, espD and tir alleles were found; the most prevalent combination was espA-beta, espB-beta, espD-beta, tir-beta (34/181 strains), which was more frequent among tEPEC strains (P<0.05). Our findings indicate that there is a high degree of heterogeneity among EPEC strains isolated from Peruvian children and that aEPEC and tEPEC variants cluster.
PMCID: PMC3542133  PMID: 22493278
15.  Chelating agents exert distinct effects on biofilm formation in Staphylococcus aureus depending on strain background: role for clumping factor B 
Journal of Medical Microbiology  2012;61(Pt 8):1062-1070.
Staphylococcus aureus is a leading cause of catheter infections, and biofilm formation plays a key role in the pathogenesis. Metal ion chelators inhibit bacterial biofilm formation and viability, making them attractive candidates as components in catheter lock solutions. The goal of this study was to characterize further the effect of chelators on biofilm formation. The effect of the calcium chelators ethylene glycol tetraacetic acid (EGTA) and trisodium citrate (TSC) on biofilm formation by 30 S. aureus strains was tested. The response to subinhibitory doses of EGTA and TSC varied dramatically depending on strain variation. In some strains, the chelators prevented biofilm formation, in others they had no effect, and they actually enhanced biofilm formation in others. The molecular basis for this phenotypic variability was investigated using two related strains: Newman, in which biofilm formation was inhibited by chelators, and 10833, which formed strong biofilms in the presence of chelators. It was found that deletion of the gene encoding the surface adhesin clumping factor B (clfB) completely eliminated chelator-induced biofilm formation in strain 10833. The role of ClfB in biofilm formation activity in chelators was confirmed in additional strains. It was concluded that biofilm-forming ability varies strikingly depending on strain background, and that ClfB is involved in biofilm formation in the presence EGTA and citrate. These results suggest that subinhibitory doses of chelating agents in catheter lock solutions may actually augment biofilm formation in certain strains of S. aureus, and emphasize the importance of using these agents appropriately so that inhibitory doses are achieved consistently.
PMCID: PMC3542134  PMID: 22516131
16.  Globally dispersed mobile drug-resistance genes in Gram-negative bacterial isolates from patients with bloodstream infections in a US urban general hospital 
Journal of Medical Microbiology  2012;61(Pt 7):968-974.
Mobile drug-resistance genes with identical nucleic acid sequences carried by multidrug-resistant Escherichia coli strains that cause community-acquired infections are becomingly increasingly dispersed worldwide. Over a 2-year period, we analysed Gram-negative bacterial (GNB) pathogens from the blood of inpatients at an urban public hospital to determine what proportion of these isolates carried such globally dispersed drug-resistance genes. Of 376 GNB isolates, 167 (44 %) were Escherichia coli, 50 (13 %) were Klebsiella pneumoniae, 25 (7 %) were Pseudomonas aeruginosa, 25 (7 %) were Proteus mirabilis and 20 (5 %) were Enterobacter cloacae; the remainder (24 %) comprised 26 different GNB species. Among E. coli isolates, class 1 integrons were detected in 64 (38 %). The most common integron gene cassette configuration was dfrA17-aadA5, found in 30 (25 %) of 119 drug-resistant E. coli isolates and in one isolate of Moraxella morganii. Extended-spectrum β-lactamase (ESBL) genes were found in 16 E. coli isolates (10 %). These genes with identical sequences were found in nearly 40 % of bloodstream E. coli isolates in the study hospital, as well as in a variety of bacterial species from clinical and non-clinical sources worldwide. Thus, a substantial proportion of bloodstream infections among hospitalized patients were caused by E. coli strains carrying drug-resistance genes that are dispersed globally in a wide variety of bacterial species.
PMCID: PMC3542709  PMID: 22493279
17.  Fungal cell wall vaccines: an update 
Journal of Medical Microbiology  2012;61(Pt 7):895-903.
This discussion is intended to be an overview of current advances in the development of fungal cell wall vaccines with an emphasis on Candida; it is not a comprehensive historical review of all fungal cell wall vaccines. Selected, more recent, innovative strategies for developing fungal vaccines will be highlighted. Both scientific and logistical obstacles related to the development of, and clinical use of, fungal vaccines will be discussed.
PMCID: PMC3542710  PMID: 22267544
18.  Persistent Helicobacter pullorum colonization in C57BL/6NTac mice: a new mouse model for an emerging zoonosis 
Journal of Medical Microbiology  2012;61(Pt 5):720-728.
Helicobacter pullorum, an enterohepatic Helicobacter species, is associated with gastroenteritis and hepatobiliary disease in humans and chickens. Recently, a novel H. pullorum outbreak in barrier-maintained rats and mice was described. In this study, persistence of infection and serological responses were further evaluated in H. pullorum-infected female C57BL/6NTac and C3H/HeNTac mice obtained from the barrier outbreak. C57BL/6NTac mice (n = 36) aged 10–58 weeks were confirmed to be chronically infected with H. pullorum by PCR or culture of caecum, colon and faeces, with no evidence of hepatic infection; two of three C3H/HeNTac mice cleared H. pullorum infection by 26 weeks of age. A quantitative PCR (qPCR) assay based on the cdtB gene specific to H. pullorum demonstrated that colonization was high in the caecum and colon at 104–106 c.f.u. equivalents per µg host DNA, and decreased by several logs from 32 to 58 weeks of age. Infected mice were seropositive by ELISA, and H. pullorum-specific IgG levels decreased as colonization was lost over time in selected mice. Consistent with the lack of pathology associated with chronic infection of C57BL/6 mice with other murine enteric helicobacters, C57BL/6NTac and C3H/HeNTac mice infected with H. pullorum did not develop gross or histological lesions of the liver or gastrointestinal tract. The cdtB-based qPCR assay can be used in screening animals, food sources and environmental samples for H. pullorum, as this food-borne pathogen has zoonotic potential. These findings will also allow future studies in murine models to dissect potential pathogenic mechanisms for this emerging pathogen.
PMCID: PMC3542706  PMID: 22301616
19.  Molecular epidemiological investigation to determine the source of a fatal case of serotype 22F pneumococcal meningitis 
Journal of Medical Microbiology  2012;61(Pt 5):686-692.
A child’s death due to pneumococcal meningitis after contracting the disease in an after-school programme prompted an investigation to assess nasopharyngeal (NP) carriage among her contacts. The serotype of the meningitis case isolate was determined, together with the serotypes of the NP specimens of contacts, comprising the case patient’s brother, the case patient’s after-school programme contacts and the brother’s day-care centre (DCC) contacts. NP swabs from 155 children and 69 adults were obtained. Real-time PCR and conventional multiplex PCR (CM-PCR) assays were used to detect pneumococcal carriage and determine serotypes. Broth-enriched culture of NP specimens followed by pneumococcal isolation and Quellung-based serotyping were also performed. DNA extracts prepared from cerebrospinal fluid of the index case and from the NP strain isolated from the brother and from one attendee of the brother’s DCC were subjected to genotyping. Pneumococcal carriage assessed by real-time PCR and culture was 49.6 and 36.6 %, respectively (P<0.05). Twenty-three serotypes were detected using CM-PCR, with serotypes 6A/6B, 14, 19F, 6C/6D, 22F/22A, 23F and 11A/11D being the most frequent. All eight serotype 22F/22A NP specimens recovered were from children attending the brother’s DCC. The meningitis case isolate and the NP carriage isolate from the patient’s brother were both serotype 22F and shared the same new multilocus sequence type (ST6403) with the attendee of the brother’s DCC. CM-PCR proved to be useful for assessing carriage serotype distribution in a setting of high-risk pneumococcal transmission. The causal serotype appeared to be linked to the brother of the case patient and attendees of his DCC.
PMCID: PMC3542707  PMID: 22286925
20.  Development of monoclonal antibodies to recombinant terrelysin and characterization of expression in Aspergillus terreus 
Journal of Medical Microbiology  2012;61(Pt 4):489-499.
Aspergillus terreus is an emerging pathogen that mostly affects immunocompromised patients, causing infections that are often difficult to manage therapeutically. Current diagnostic strategies are limited to the detection of fungal growth using radiological methods or biopsy, which often does not enable species-specific identification. There is thus a critical need for diagnostic techniques to enable early and specific identification of the causative agent. In this study, we describe monoclonal antibodies (mAbs) developed to a previously described recombinant form of the haemolysin terrelysin. Sixteen hybridomas of various IgG isotypes were generated to the recombinant protein, of which seven demonstrated reactivity to the native protein in hyphal extracts. Cross-reactivity analysis using hyphal extracts from 29 fungal species, including 12 Aspergillus species and five strains of A. terreus, showed that three mAbs (13G10, 15B5 and 10G4) were A. terreus-specific. Epitope analysis demonstrated mAbs 13G10 and 10G4 recognize the same epitope, PSNEFE, while mAb 15B5 recognizes the epitope LYEGQFHS. Time-course studies showed that terrelysin expression was highest during early hyphal growth and dramatically decreased after mycelial expansion. Immunolocalization studies demonstrated that terrelysin was not only localized within the cytoplasm of hyphae but appeared to be more abundant at the hyphal tip. These findings were confirmed in cultures grown at room temperature as well as at 37 °C. Additionally, terrelysin was detected in the supernatant of A. terreus cultures. These observations suggest that terrelysin may be a candidate biomarker for A. terreus infection.
PMCID: PMC3348537  PMID: 22160315
21.  Molecular characterization reveals distinct genospecies of Anaplasma phagocytophilum from diverse North American hosts 
Journal of Medical Microbiology  2012;61(Pt 2):204-212.
Anaplasma phagocytophilum is an emerging tick-borne pathogen that infects humans, domestic animals and wildlife throughout the Holarctic. In the far-western United States, multiple rodent species have been implicated as natural reservoirs for A. phagocytophilum. However, the presence of multiple A. phagocytophilum strains has made it difficult to determine which reservoir hosts pose the greatest risk to humans and domestic animals. Here we characterized three genetic markers (23S–5S rRNA intergenic spacer, ank and groESL) from 73 real-time TaqMan PCR-positive A. phagocytophilum strains infecting multiple rodent and reptile species, as well as a dog and a horse, from California. Bayesian and maximum-likelihood phylogenetic analyses of all three genetic markers consistently identified two major clades, one of which consisted of A. phagocytophilum strains infecting woodrats and the other consisting of strains infecting sciurids (chipmunks and squirrels) as well as the dog and horse strains. In addition, analysis of the 23S–5S rRNA spacer region identified two unique and highly dissimilar clades of A. phagocytophilum strains infecting several lizard species. Our findings indicate that multiple unique strains of A. phagocytophilum with distinct host tropisms exist in California. Future epidemiological studies evaluating human and domestic animal risk should incorporate these distinctions.
PMCID: PMC3352158  PMID: 21921109
22.  Variability of trinucleotide tandem repeats in the MgPa operon and its repetitive chromosomal elements in Mycoplasma genitalium 
Journal of Medical Microbiology  2012;61(Pt 2):191-197.
Mycoplasma genitalium, a human pathogen associated with sexually transmitted diseases, is unique in that it has the smallest genome of any known free-living organism. Despite its small genome, 4.7 % of the total genomic sequence is devoted to making the MgPa adhesin operon (containing the MG190, MG191 and MG192 genes) and its repetitive chromosomal sequences (known as MgPars). The goals of this study were to investigate the location, organization and variability of trinucleotide tandem repeats (TTRs) in the MgPa operon and MgPars and to explore the possible mechanisms and role of TTR variations. By analysing the complete MgPa operon and complete or partial MgPar sequences in a collection of 15 geographically diverse clinical strains of M. genitalium, TTR sequences were identified in four regions in MG191, one region in MG192, and two or three regions in each of all nine MgPars except for MgPar 3. These TTRs were variable not only in the repeat copy number but also in the repeat unit sequence among or within strains. The key mechanisms for the TTR variations likely include recombination between MgPa and MgPars, and slipped-strand mispairing. TTR variation may represent a mechanism to maximize the variation of the MgPa operon, which is complementary to genetic variation involving segmental recombination between MgPa and MgPars, thus enhancing the organism’s ability to adhere to and colonize host cells as well as evasion of the host immune system.
PMCID: PMC3352159  PMID: 21997874
23.  Structure of rrn operons in pathogenic non-cultivable treponemes: sequence but not genomic position of intergenic spacers correlates with classification of Treponema pallidum and Treponema paraluiscuniculi strains 
Journal of Medical Microbiology  2013;62(Pt 2):196-207.
This study examined the sequences of the two rRNA (rrn) operons of pathogenic non-cultivable treponemes, comprising 11 strains of T. pallidum ssp. pallidum (TPA), five strains of T. pallidum ssp. pertenue (TPE), two strains of T. pallidum ssp. endemicum (TEN), a simian Fribourg-Blanc strain and a rabbit T. paraluiscuniculi (TPc) strain. PCR was used to determine the type of 16S–23S ribosomal intergenic spacers in the rrn operons from 30 clinical samples belonging to five different genotypes. When compared with the TPA strains, TPc Cuniculi A strain had a 17 bp deletion, and the TPE, TEN and Fribourg-Blanc isolates had a deletion of 33 bp. Other than these deletions, only 17 heterogeneous sites were found within the entire region (excluding the 16S–23S intergenic spacer region encoding tRNA-Ile or tRNA-Ala). The pattern of nucleotide changes in the rrn operons corresponded to the classification of treponemal strains, whilst two different rrn spacer patterns (Ile/Ala and Ala/Ile) appeared to be distributed randomly across species/subspecies classification, time and geographical source of the treponemal strains. It is suggested that the random distribution of tRNA genes is caused by reciprocal translocation between repetitive sequences mediated by a recBCD-like system.
PMCID: PMC3755535  PMID: 23082031
24.  Interlaboratory reproducibility of DiversiLab rep-PCR typing and clustering of Acinetobacter baumannii isolates 
Journal of Medical Microbiology  2012;61(Pt 1):137-141.
We have investigated the reproducibility of DiversiLab rep-PCR fingerprints between two laboratories with the aim of determining if the fingerprints and clustering are laboratory-specific or portable. One-hundred non-duplicate Acinetobacter baumannii isolates were used in this study. DNA isolation and rep-PCR were each performed separately in two laboratories and rep-PCR patterns generated in laboratory A were compared with those from laboratory B. Twelve A. baumannii isolates processed in laboratory A showed ≥98 % pattern similarity with the corresponding 12 isolates tested in laboratory B and were considered identical. Sixty-four isolates showed 95–97.9 % similarity with their corresponding isolates. Twenty-three isolates showed 90–94 % similarity with the corresponding isolates, while one isolate showed only 87.4 % similarity. However, intra-laboratory clustering was conserved: isolates that clustered in laboratory A also clustered in laboratory B. While clustering was conserved and reproducible at two different laboratories, demonstrating the robustness of rep-PCR, interlaboratory comparison of individual isolate fingerprints showed more variability. This comparison allows conclusions regarding clonality to be reached independent of the laboratory where the analysis is performed.
PMCID: PMC3347881  PMID: 21903821
25.  Microsatellite typing of Aspergillus flavus from clinical and environmental avian isolates 
Journal of Medical Microbiology  2013;62(Pt 1):121-125.
Aspergillosis is one of the most common causes of death in captive birds. Aspergillus fumigatus accounts for approximately 95 % of aspergillosis cases and Aspergillus flavus is the second most frequent organism associated with avian infections. In the present study, the fungi were grown from avian clinical samples (post-mortem lung material) and environmental samples (eggs, food and litter). Microsatellite markers were used to type seven clinical avian isolates and 22 environmental isolates of A. flavus. A. flavus was the only species (28 % prevalence) detected in the avian clinical isolates, whereas this species ranked third (19 %) after members of the genera Penicillium (39 %) and Cladosporium (21 %) in the environmental samples. Upon microsatellite analysis, five to eight distinct alleles were detected for each marker. The marker with the highest discriminatory power had eight alleles and a 0.852 D value. The combination of all six markers yielded a 0.991 D value with 25 distinct genotypes. One clinical avian isolate (lung biopsy) and one environmental isolate (egg) shared the same genotype. Microsatellite typing of A. flavus grown from avian and environmental samples displayed an excellent discriminatory power and 100 % reproducibility. This study showed a clustering of clinical and environmental isolates, which were clearly separated. Based upon these results, aspergillosis in birds may be induced by a great diversity of isolates.
PMCID: PMC3541757  PMID: 22977077

Results 1-25 (73)