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1.  Decline of Salmonella enterica Serotype Choleraesuis Infections, Taiwan 
Emerging Infectious Diseases  2014;20(4):715-716.
PMCID: PMC3966396  PMID: 24655558
Salmonella enterica serotype Choleraesuis; invasive infection; antimicrobial resistance; bacteria; Taiwan; zoonoses
2.  Differential Genomic Variation between Short- and Long-Term Bacterial Evolution Revealed by Ultradeep Sequencing 
Genome Biology and Evolution  2013;5(3):572-577.
Mutation and selection are both thought to impact significantly the nucleotide composition of bacterial genomes. Earlier studies have compared closely related strains to obtain mutation patterns based on the hypothesis that these bacterial strains had diverged so recently that selection will not have had enough time to play its role. In this study, we used a SOLiD autosequencer that was based on a dual-base encoding scheme to sequence the genome of Staphylococcus aureus with a mapping coverage of over 5,000×. By directly counting the variation obtained from these ultradeep sequencing reads, we found that A → G was the predominant single-base substitution and 1 bp deletions were the major small indel. These patterns are completely different from those obtained by comparison of closely related S. aureus strains, where C → T accounted for a larger proportion of mutations and deletions were shown to occur at an almost equal frequency to insertion. These findings suggest that the genomic differences between closely related bacterial strains have already undergone selection and are therefore not representative of spontaneous mutation.
PMCID: PMC3622303  PMID: 23531725
bacterial genome; mutation; next-generation sequencing; selection
3.  Fish Tank Granuloma Caused by Mycobacterium marinum 
PLoS ONE  2012;7(7):e41296.
Mycobacterium marinum causes skin and soft tissue, bone and joint, and rare disseminated infections. In this study, we aimed to investigate the relationship between treatment outcome and antimicrobial susceptibility patterns. A total of 27 patients with M. marinum infections were enrolled.
Data on clinical characteristics and therapeutic methods were collected and analyzed. We also determined the minimum inhibitory concentrations of 7 antibiotics against 30 isolates from these patients.
Twenty-seven patients received antimycobacterial agents with or without surgical debridement. Eighteen patients were cured, 8 failed to respond to treatment, and one was lost to follow-up. The duration of clarithromycin (147 vs. 28; p = 0.0297), and rifampicin (201 vs. 91; p = 0.0266) treatment in the cured patients was longer than that in the others. Surgical debridement was performed in 10 out of the 18 cured patients, and in 1 of another group (p = 0.0417). All the 30 isolates were susceptible to clarithromycin, amikacin, and linezolid; 29 (96.7%) were susceptible to ethambutol; 28 (93.3%) were susceptible to sulfamethoxazole; and 26 (86.7%) were susceptible to rifampicin. However, only 1 (3.3%) isolate was susceptible to doxycycline.
Early diagnosis of the infection and appropriate antimicrobial therapy with surgical debridement are the mainstays of successful treatment. Clarithromycin and rifampin are supposed to be more effective agents.
PMCID: PMC3401166  PMID: 22911774
4.  Complete Genome and Transcriptomes of Streptococcus parasanguinis FW213: Phylogenic Relations and Potential Virulence Mechanisms 
PLoS ONE  2012;7(4):e34769.
Streptococcus parasanguinis, a primary colonizer of the tooth surface, is also an opportunistic pathogen for subacute endocarditis. The complete genome of strain FW213 was determined using the traditional shotgun sequencing approach and further refined by the transcriptomes of cells in early exponential and early stationary growth phases in this study. The transcriptomes also discovered 10 transcripts encoding known hypothetical proteins, one pseudogene, five transcripts matched to the Rfam and additional 87 putative small RNAs within the intergenic regions defined by the GLIMMER analysis. The genome contains five acquired genomic islands (GIs) encoding proteins which potentially contribute to the overall pathogenic capacity and fitness of this microbe. The differential expression of the GIs and various open reading frames outside the GIs at the two growth phases suggested that FW213 possess a range of mechanisms to avoid host immune clearance, to colonize host tissues, to survive within oral biofilms and to overcome various environmental insults. Furthermore, the comparative genome analysis of five S. parasanguinis strains indicates that albeit S. parasanguinis strains are highly conserved, variations in the genome content exist. These variations may reflect differences in pathogenic potential between the strains.
PMCID: PMC3329508  PMID: 22529932
5.  Effect of Probiotics Lactobacillus acidophilus on Citrobacter rodentium Colitis: The Role of Dendritic Cells 
Pediatric research  2009;65(2):169-175.
Modulation of the intestinal immune response early in life by administration of probiotic bacteria may be an effective strategy for preventing or attenuating infectious diarrhea. We preinoculated the mice early in life with the probiotic bacteria Lactobacillus acidophilus NCFM (La) at age 2 wk. Dendritic cells (DCs) were collected and purified from mesenteric lymph nodes (MLN) and spleens of the BalbC/ByJ mice. DC isolation and adoptive transfer was used to examine the function of probiotics. We demonstrated that when mice were adoptively transferred with La-primed DCs (t-LaDC) instead of oral consumption with La, there was a similar effect on fecal bacteria counts, IgA levels, and colonic histopathology, as well as cytokine levels in MLN when there was intestinal bacterial infection. The above findings suggest that DCs play a key role in probiotics attenuating Citrobacter rodentium (Cr) colitis. Moreover, the location of La-primed DC hints that there is interaction of DCs and T cells in the digestive system of the host. Up-regulated expression of a surface marker on DCs indicated that inoculation with probiotics will stimulate the function of DCs, thereby further increasing immune response triggered by DC.
PMCID: PMC3206789  PMID: 19262293
6.  Seroprevalence and Severity of 2009 Pandemic Influenza A H1N1 in Taiwan 
PLoS ONE  2011;6(9):e24440.
This study is to determine the seroprevalence of the pandemic influenza A H1N1 virus (pH1N1) in Taiwan before and after the 2009 pandemic, and to estimate the relative severity of pH1N1 infections among different age groups.
Methodology/Principal Findings
A total of 1544 and 1558 random serum samples were collected from the general population in Taiwan in 2007 and 2010, respectively. Seropositivity was defined by a hemagglutination inhibition titer to pH1N1 (A/Taiwan/126/09) ≥1:40. The seropositivity rate of pH1N1 among the unvaccinated subjects and national surveillance data were used to compare the proportion of infections that led to severe diseases and fatalities among different age groups. The overall seroprevalence of pH1N1 was 0.91% (95% confidence interval [CI] 0.43–1.38) in 2007 and significantly increased to 29.9% (95% CI 27.6–32.2) in 2010 (p<0.0001), with the peak attack rate (55.4%) in 10–17 year-old adolescents, the lowest in elderly ≥65 years (14.1%). The overall attack rates were 20.6% (188/912) in unvaccinated subjects. Among the unvaccinated but infected populations, the estimated attack rates of severe cases per 100,000 infections were significantly higher in children aged 0–5 years (54.9 cases, odds ratio [OR] 4.23, 95% CI 3.04–5.90) and elderly ≥ 65years (22.4 cases, OR 2.76, 95% CI 1.99–3.83) compared to adolescents aged 10–17 years (13.0 cases). The overall case-fatality rate was 0.98 per 100,000 infections without a significant difference in different age groups.
Pre-existing immunity against pH1N1 was rarely identified in Taiwanese at any age in 2007. Young children and elderly – the two most lower seroprotection groups showed the greatest vulnerability to clinical severity after the pH1N1 infections. These results imply that both age groups should have higher priority for immunization in the coming flu season.
PMCID: PMC3164718  PMID: 21909433
7.  Increasing Ceftriaxone Resistance in Salmonellae, Taiwan 
Emerging Infectious Diseases  2011;17(6):1086-1090.
In Taiwan, despite a substantial decline of Salmonella enterica serotype Choleraesuis infections, strains resistant to ciprofloxacin and ceftriaxone persist. A self-transferable blaCMY-2-harboring IncI1 plasmid was identified in S. enterica serotypes Choleraesuis, Typhimurium, Agona, and Enteritidis and contributed to the overall increase of ceftriaxone resistance in salmonellae.
PMCID: PMC3358216  PMID: 21749777
Salmonella enterica serotype Choleraesuis; nontyphoidal Salmonella; antimicrobial resistance; salmonellae; CMY-2; Tn6092; conjugative resistance plasmid; bacteria; Taiwan; letter
8.  Group B Streptococcal Disease in Nonpregnant Patients: Emergence of Highly Resistant Strains of Serotype Ib in Taiwan in 2006 to 2008 ▿  
Journal of Clinical Microbiology  2010;48(7):2571-2574.
Among the 228 group B Streptococcus (GBS) isolates recovered in 2006 to 2008, higher resistance to erythromycin (58.3%) and clindamycin (57.9%) was found in isolates with certain resistance phenotypes. Serotype Ib isolates (24.6%) were the second most prevalent serotype, next to serotype V (29.4%), and showed the highest resistance rates to erythromycin (91.0%) and clindamycin (82.1%).
PMCID: PMC2897481  PMID: 20444969
9.  Multidrug Resistant Acinetobacter baumannii: Risk Factors for Appearance of Imipenem Resistant Strains on Patients Formerly with Susceptible Strains 
PLoS ONE  2010;5(4):e9947.
Multidrug resistant Acinetobacter baumannii (MDRAB) is an important nosocomial pathogen usually susceptible to carbapenems; however, growing number of imipenem resistant MDRAB (IR-MDRAB) poses further clinical challenge. The study was designed to identify the risk factors for appearance of IR-MDRAB on patients formerly with imipenem susceptible MDRAB (IS-MDRAB) and the impact on clinical outcomes.
Methodology/Principal Findings
A retrospective case control study was carried out for 209 consecutive episodes of IS-MDRAB infection or colonization from August 2001 to March 2005. Forty-nine (23.4%) episodes with succeeding clinical isolates of IR-MDRAB were defined as the cases and 160 (76.6%) with all subsequent clinical isolates of IS-MDRAB were defined as the controls. Quantified antimicrobial selective pressure, “time at risk”, severity of illness, comorbidity, and demographic data were incorporated for multivariate analysis, which revealed imipenem or meropenem as the only significant independent risk factor for the appearance of IR-MDRAB (adjusted OR, 1.18; 95% CI, 1.09 to 1.27). With selected cases and controls matched to exclude exogenous source of IR-MDRAB, multivariate analysis still identified carbapenem as the only independent risk factor (adjusted OR, 1.48; 95% CI, 1.14 to 1.92). Case patients had a higher crude mortality rate compared to control patients (57.1% vs. 31.3%, p = 0.001), and the mortality of case patients was associated with shorter duration of “time at risk”, i.e., faster appearance of IR-MDRAB (adjusted OR, 0.9; 95% CI, 0.83 to 0.98).
Judicious use of carbapenem with deployment of antibiotics stewardship measures is critical for reducing IR-MDRAB and the associated unfavorable outcome.
PMCID: PMC2846922  PMID: 20369056
10.  Characterization of 13 multi-drug resistant Salmonella serovars from different broiler chickens associated with those of human isolates 
BMC Microbiology  2010;10:86.
Salmonella are frequently isolated from chickens and their products. Prevalent serogroups and serovars of Salmonella as well as their genotypes and antibiograms were determined for cloacal samples from 1595 chickens. To understand the possible serovar and H antigens for transmission between chicken and human, serovars and their H antigens of 164 chicken and 5314 human isolates were compared.
Prevalence of Salmonella differed among chicken lines and ages. Chicken and human isolates belonged mainly to serogroup B, C1, C2-C3, D, and E. 13 serovars and 66 serovars were identified for chicken and human isolates respectively. The common serovars for chicken and human isolates were S. Typhimurium, S. Enteritidis, S. Albany, S. Derby, and S. Anatum and shared common H1 antigens "g complex; i; e,h; and z4,z24" and H2 antigens "1 complex and -". In human isolates, H1 antigen "i" and H2 antigen "-" were common in all serogroups. In chicken, antimicrobial susceptibility differed among serogroups, serovars and three counties. All isolates were susceptible to cefazolin and ceftriaxone, but highly resistant to ampicillin, chloramphenicol, flumequine, streptomycin, sulfamethoxazole-trimethoprim, and tetracycline. Except those isolates of serogroup C1 of Chick group and serogroup G, all isolates were multi-drug resistance. Only S. Kubacha, S. Typhimurium, S. Grampian, and S. Mons were resistant to ciprofloxacin and/or enrofloxacin.
In chicken, prevalent serogroups and serovars were associated with chicken ages, lines and regions; and flouroquinolone-resistant and MDR isolates emerged. H1 antigens "g complex and i" and H2 antigens "1 complex and -" might be important for transmission of Salmonella between chicken and human.
PMCID: PMC2859872  PMID: 20307324
11.  Clonal dissemination of the multi-drug resistant Salmonella enterica serovar Braenderup, but not the serovar Bareilly, of prevalent serogroup C1 Salmonella from Taiwan 
BMC Microbiology  2009;9:264.
Nontyphoidal Salmonella is the main cause of human salmonellosis. In order to study the prevalent serogroups and serovars of clinical isolates in Taiwan, 8931 Salmonellae isolates were collected from 19 medical centers and district hospitals throughout the country from 2004 to 2007. The pulsed-field eletrophoresis types (PFGE) and antibiotic resistance profiles of Salmonella enterica serovars Bareilly (S. Bareilly) and Braenderup (S. Braenderup) were compared, and multi-drug resistance (MDR) plasmids were characterized.
Over 95% of human salmonellosis in Taiwan was caused by five Salmonella serogroups: B, C1, C2-C3, D1, and E1. S. Typhymurium, S. Enteritidis, S. Stanley and S. Newport were the four most prevalent serovars, accounting for about 64% of isolates. While only one or two major serovars from four of the most prevalent serogroups were represented, four predominant serovars were found in serogroup C1 Salmonellae. The prevalence was decreasing for S. Choleraeuis and S. Braenderup, and S. Virchow and increasing for S. Bareilly. S. Braenderup mainly caused gastroenteritis in children; in contrast, S. Bareiley infected children and elderly people. Both serovars differed by XbaI-PFGE patterns. Almost all S. Bareilly isolates were susceptible to antibiotics of interest, while all lacked plasmids and belonged to one clone. Two distinct major clones in S. Braenderup were cluster A, mainly including MDR isolates with large MDR plasmid from North Taiwan, and cluster B, mainly containing susceptible isolates without R plasmid from South Taiwan. In cluster A, there were two types of conjugative R plasmids with sizes ranging from 75 to 130 kb. Type 1 plasmids consisted of replicons F1A/F1B, blaTEM, IS26, and a class 1 integron with the genes dfrA12-orfF-aadA2-qacEΔ1-sulI. Type 2 plasmids belonged to incompatibility group IncI, contained tnpA-blaCMY-2-blc-sugE genetic structures and lacked both IS26 and class 1 integrons. Although type 2 plasmids showed higher conjugation capability, type 1 plasmids were the predominant plasmid.
Serogroups B, C1, C2-C3, D1, and E1 of Salmonella caused over 95% of human salmonellosis. Two prevalent serovars within serogroup C1, S. Bareilly and cluster B of S. Braenderup, were clonal and drug-susceptible. However, cluster A of S. Braenderup was MDR and probably derived from susceptible isolates by acquiring one of two distinct conjugative R plasmids.
PMCID: PMC2806260  PMID: 20017951
12.  Truncated tni Module Adjacent to the Complex Integron of Salmonella Genomic Island 1 in Salmonella enterica Serovar Virchow ▿  
Salmonella genomic island 1 was identified for the first time in Salmonella enterica serovar Virchow isolated from humans in Taiwan. The complex class 1 integron conferring multidrug resistance was shown to be inserted within open reading frame (ORF) S023 and contains for the first time a partial transpositional module. The 5-bp target duplication flanking the complex integron suggests that its insertion in ORF S023 was by transposition.
PMCID: PMC2630650  PMID: 19015337
13.  Genome evolution driven by host adaptations results in a more virulent and antimicrobial-resistant Streptococcus pneumoniae serotype 14 
BMC Genomics  2009;10:158.
Streptococcus pneumoniae serotype 14 is one of the most common pneumococcal serotypes that cause invasive pneumococcal diseases worldwide. Serotype 14 often expresses resistance to a variety of antimicrobial agents, resulting in difficulties in treatment. To gain insight into the evolution of virulence and antimicrobial resistance traits in S. pneumoniae from the genome level, we sequenced the entire genome of a serotype 14 isolate (CGSP14), and carried out comprehensive comparison with other pneumococcal genomes. Multiple serotype 14 clinical isolates were also genotyped by multilocus sequence typing (MLST).
Comparative genomic analysis revealed that the CGSP14 acquired a number of new genes by horizontal gene transfer (HGT), most of which were associated with virulence and antimicrobial resistance and clustered in mobile genetic elements. The most remarkable feature is the acquisition of two conjugative transposons and one resistance island encoding eight resistance genes. Results of MLST suggested that the major driving force for the genome evolution is the environmental drug pressure.
The genome sequence of S. pneumoniae serotype 14 shows a bacterium with rapid adaptations to its lifecycle in human community. These include a versatile genome content, with a wide range of mobile elements, and chromosomal rearrangement; the latter re-balanced the genome after events of HGT.
PMCID: PMC2678160  PMID: 19361343
14.  Prevalence and Characterization of Multidrug-Resistant (Type ACSSuT) Salmonella enterica Serovar Typhimurium Strains in Isolates from Four Gosling Farms and a Hatchery Farm▿  
Journal of Clinical Microbiology  2007;46(2):522-526.
Salmonella enterica serovar Typhimurium strains of phage types DT104 and U302 are often resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline (the ACSSuT resistance type) and are major zoonotic pathogens. Increased consumption of goose meat may enhance the risk of transferring S. enterica serovar Typhimurium and other enteric pathogens from geese to human due to the consumption of meats from infected geese or improper preparation of meats. Therefore, we characterized S. enterica serovar Typhimurium strains isolated from four goose farms (farms A, B, C, and D) and one hatchery farm (farm E) to determine the epidemic and genetic differences among them. Antibiotic susceptibility tests and multiplex PCR confirmed that 77.6% (52/67) of strains were ACSSuT strains isolated from farms A, C, and E. Antibiotic-susceptible strains were isolated mostly from farm B, and no strain was observed in farm D. All ACSSuT strains harbored a 94.7-kb virulence plasmid and contained one 1.1-kb conserved segment identical to that of Salmonella genomic island 1. Four genotypes were determined among these S. enterica serovar Typhimurium isolates by pulsed-field gel electrophoresis analysis of XbaI-digested DNA fragments. Most isolates (85.29%; 29/34) of major genotype Ib were ACSSuT strains isolated mainly from goslings of farm C and egg membranes of farm E, a hatchery farm, suggesting that S. enterica serovar Typhimurium strains in isolates from goslings might originate from its hatchery, from the egg membranes to the gosling fluff after hatching. Multiple phage types, types 8, 12, U283, DT104, and U302, were identified. In conclusion, geese were a reservoir of diverse multidrug-resistant (type ACSSuT) S. enterica serovar Typhimurium strains, and each farm was colonized with genetically closely related S. enterica serovar Typhimurium strains.
PMCID: PMC2238140  PMID: 18077649
15.  Increasing Ceftriaxone Resistance and Multiple Alterations of Penicillin-Binding Proteins among Penicillin-Resistant Streptococcus pneumoniae Isolates in Taiwan▿  
The rate of nonsusceptibility of penicillin-resistant Streptococcus pneumoniae strains to ceftriaxone increased significantly in Taiwan in 2005. Approximately 90% of the ceftriaxone-nonsusceptible isolates were found to be of four major serotypes (serotypes 6B, 14, 19F, and 23F). Seven amino acid alterations in the penicillin-binding protein 2B transpeptidase-encoding region specifically contributed to the resistance.
PMCID: PMC2043203  PMID: 17591850
16.  Molecular Epidemiology and Clinical Manifestations of Viral Gastroenteritis in Hospitalized Pediatric Patients in Northern Taiwan▿  
Journal of Clinical Microbiology  2007;45(6):2054-2057.
By reverse transcription-PCR or PCR, among 257 children with nonbacterial acute gastroenteritis (AGE), rotavirus, norovirus, astrovirus, enteric adenovirus, and multiple viruses were identified in 78 (30.4%), 21 (8.2%), 7 (2.7%), 51 (19.8%), and 53 (20.6%) patients, respectively. Higher disease severity was found for AGE caused by multiple viruses and by rotavirus alone. The majority of rotaviruses isolated from 2004 to 2006 belonged to genotypes G1 (20.4%), G2 (16.5%), G3 (27.2%), and G9 (21.4%).
PMCID: PMC1933068  PMID: 17442805
17.  Detection of Multidrug-Resistant Salmonella enterica Serovar Typhimurium Phage Types DT102, DT104, and U302 by Multiplex PCR 
Journal of Clinical Microbiology  2006;44(7):2354-2358.
Salmonella enterica serovar Typhimurium is a common cause of nontyphoidal salmonellosis in humans and animals. Multidrug-resistant serovar Typhimurium phage type DT104, which emerged in the 1990s, has become widely distributed in many countries. A total of 104 clinical isolates of Salmonella serogroup B were collected from three major hospitals in Taiwan during 1997 to 2003 and were examined by a multiplex PCR targeting the resistance genes and the spv gene of the virulence plasmid. A total of 51 isolates (49%) were resistant to all drugs (ACSSuT [resistance to ampicillin, chloramphenicol, streptomycin, sulfonamide, and tetracycline]), and all contained a 1.25-kb PCR fragment of integron that is part of the 43-kb Salmonella genomic island 1 (SGI1). The second group was resistant to SSu (28%), and the third was susceptible to all five drugs (13%). Fifty-nine isolates were serotyped to be serovar Typhimurium by the tube agglutination method using H antisera. The virulence plasmid was found in 54 (91.5%) of the 59 serovar Typhimurium isolates. A majority (94.1%) of the Salmonella serogroup B isolates with the ACSSuT resistance pattern harbored a virulence plasmid. Phage typing identified three major phage types: DT104, DT120, and U302. Analysis of the isolates by pulsed-field gel electrophoresis showed six genotypes. We found two genotypes in DT104 strains, two in DT120, and the other two in U302. The presence of a monophasic serovar (4,5,12:i:−) has added difficulty in the determination of the serovars of multidrug-resistant Salmonella serogroup B isolates. Nevertheless, the multiplex PCR devised in the present study appears to be efficient and useful in the rapid identification of ACSSuT-type serovar Typhimurium with SGI1, irrespective of their phage types.
PMCID: PMC1489530  PMID: 16825349
18.  Development of a Multiplex PCR and SHV Melting-Curve Mutation Detection System for Detection of Some SHV and CTX-M β-Lactamases of Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae in Taiwan 
Journal of Clinical Microbiology  2005;43(9):4486-4491.
Infection by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae has been increasing in Taiwan. Accurate identification of the ESBL genes is necessary for surveillance and for epidemiological studies of the mode of transmission in the hospital setting. We describe herein the development of a novel system, which consists of a multiplex PCR to identify blaSHV, blaCTX-M-3-like, and blaCTX-M-14-like genes and a modified SHV melting-curve mutation detection method to rapidly distinguish six prevalent blaSHV genes (blaSHV-1, blaSHV-2, blaSHV-2a, blaSHV-5, blaSHV-11, and blaSHV-12) in Taiwan. Sixty-five clinical isolates, which had been characterized by nucleotide sequencing of the blaSHV and blaCTX-M genes, were identified by the system. The system was then used to genotype the ESBLs from 199 clinical isolates, including 40 Enterobacter cloacae, 68 Escherichia coli, and 91 Klebsiella pneumoniae, collected between August 2002 and March 2003. SHV-12 (80 isolates) was the most prevalent type of ESBL identified, followed in order of frequency by CTX-M-3 (65 isolates) and CTX-M-14 (36 isolates). Seventeen (9%) of the 199 clinical isolates harbored both SHV- and CTX-M-type ESBLs. In contrast to Enterobacter cloacae, the majority of which produced SHV-type ESBLs, E. coli and K. pneumoniae were more likely to possess CTX-M-type ESBLs. Three rare CTX-M types were identified through sequencing of the blaCTX-M-3-like (CTX-M-15) and blaCTX-M-14-like (CTX-M-9 and CTX-M-13) genes. The system appears to provide an efficient differentiation of ESBLs among E. coli, K. pneumoniae, and Enterobacter cloacae in Taiwan. Moreover, the design of the system can be easily adapted for similar purposes in areas where different ESBLs are prevalent.
PMCID: PMC1234143  PMID: 16145096
19.  Epidemiologic Relationship between Fluoroquinolone-Resistant Salmonella enterica Serovar Choleraesuis Strains Isolated from Humans and Pigs in Taiwan (1997 to 2002) 
Journal of Clinical Microbiology  2005;43(6):2798-2804.
The emergence of ciprofloxacin-resistant Salmonella enterica serovar Choleraesuis in recent years has become an important public health issue in Taiwan. The resistant strains that cause human infections are considered to be from pigs. In this study, we characterized 157 swine and 42 human Salmonella serovar Choleraesuis isolates by pulsed-field gel electrophoresis (PFGE) and drug susceptibility testing to investigate the epidemiologic relationship among the isolates. By PFGE analyses, two major clusters (clusters GA and GB) were identified. Isolates in cluster GA were of both human and swine origins, while those in cluster GB were from pigs only. Among the various genotypes identified, genotype gt-1a was the most prevalent, which was found in 71% (30 of 42) and 48% (76 of 157) of human and swine isolates, respectively. The susceptibility tests for the 106 gt-1a isolates identified 44 susceptibility profiles and showed that 73% of human isolates and 34% of swine isolates were resistant to three fluoroquinolones (ciprofloxacin, enrofloxacin, and norfloxacin). Our findings indicate that a clonal group of Salmonella serovar Choleraesuis may have been circulating in human and swine populations in Taiwan for years and that the fluoroquinolone-resistant Salmonella serovar Choleraesuis strains most likely evolved from a gt-1a clone that emerged in 2000 and that then caused widespread infections in humans and pigs. Nevertheless, it is still debatable whether those Salmonella infections in humans are caused by isolates derived from pigs, on the basis of the higher fluoroquinolone and other antimicrobial resistance percentages in human isolates than in pig isolates.
PMCID: PMC1151913  PMID: 15956400
20.  Outbreak of Dysentery Associated with Ceftriaxone-Resistant Shigella sonnei: First Report of Plasmid-Mediated CMY-2-Type AmpC β-Lactamase Resistance in S. sonnei 
Journal of Clinical Microbiology  2005;43(6):2608-2612.
We document the first report of plasmid-encoded CMY-2-type AmpC β-lactamase identified among Shigella sonnei isolates resistant to ceftriaxone and obtained after an outbreak of bacillary dysentery in Taiwan. One hundred eighty-two children in two elementary schools in Yu-Li, Taiwan, where an outbreak occurred after a typhoon hit this area in 2001, were enrolled in this study. Clinical and epidemiologic data on the infected children were collected. Pulsed-field gel electrophoresis (PFGE) was performed on the isolates to determine the genetic relatedness of outbreak strains. Plasmid analysis and PCR were performed to identify β-lactamase genes responsible for ceftriaxone resistance. Forty-seven children from the two elementary schools were culture positive for S. sonnei in this outbreak. Twenty-three children were asymptomatic. Of the total isolates 55.3% were resistant to ampicillin. One hundred percent of the isolates obtained from children in school A were initially susceptible to both ampicillin and ceftriaxone. Of isolates obtained from school B 96.2% were nonsusceptible to ceftriaxone. However, two isolates from school A developed resistance to ampicillin during the course of treatment. All 18 available isolates showed closely related PFGE patterns (4, 4a, 4b, and 4c). CMY-2-type AmpC β-lactamase was responsible for ceftriaxone resistance in ceftriaxone-nonsusceptible isolates; Southern blot hybridization confirmed that such a resistance gene was located on the plasmid. This is the first report of plasmid-mediated CMY-2-type AmpC β-lactamase in S. sonnei. Ampicillin-resistant isolates can develop during the course of antibiotic treatment.
PMCID: PMC1151904  PMID: 15956372
22.  The genome sequence of Salmonella enterica serovar Choleraesuis, a highly invasive and resistant zoonotic pathogen 
Nucleic Acids Research  2005;33(5):1690-1698.
Salmonella enterica serovar Choleraesuis (S.Choleraesuis), a highly invasive serovar among non-typhoidal Salmonella, usually causes sepsis or extra-intestinal focal infections in humans. S.Choleraesuis infections have now become particularly difficult to treat because of the emergence of resistance to multiple antimicrobial agents. The 4.7 Mb genome sequence of a multidrug-resistant S.Choleraesuis strain SC-B67 was determined. Genome wide comparison of three sequenced Salmonella genomes revealed that more deletion events occurred in S.Choleraesuis SC-B67 and S.Typhi CT18 relative to S.Typhimurium LT2. S.Choleraesuis has 151 pseudogenes, which, among the three Salmonella genomes, include the highest percentage of pseudogenes arising from the genes involved in bacterial chemotaxis signal-transduction pathways. Mutations in these genes may increase smooth swimming of the bacteria, potentially allowing more effective interactions with and invasion of host cells to occur. A key regulatory gene of TetR/AcrR family, acrR, was inactivated through the introduction of an internal stop codon resulting in overexpression of AcrAB that appears to be associated with ciprofloxacin resistance. While lateral gene transfer providing basic functions to allow niche expansion in the host and environment is maintained during the evolution of different serovars of Salmonella, genes providing little overall selective benefit may be lost rapidly. Our findings suggest that the formation of pseudogenes may provide a simple evolutionary pathway that complements gene acquisition to enhance virulence and antimicrobial resistance in S.Choleraesuis.
PMCID: PMC1069006  PMID: 15781495
24.  Fluoroquinolone Resistance in Salmonella enterica Serotype Choleraesuis, Taiwan, 2000–2003 
Emerging Infectious Diseases  2004;10(9):1674-1676.
Salmonella enterica serotype Choleraesuis is a highly invasive pathogen that infects humans and causes systemic infections that require antimicrobial therapy. Surveillance in Taiwan showed that fluoroquinolone resistance in S. Choleraesuis markedly increased from 2000 to 2003, reaching approximately 70% in 2003.
PMCID: PMC3320291  PMID: 15498176
dispatch; Salmonella enterica serotype Choleraesuis; fluoroquinolone resistance; Taiwan
25.  Clinical and Microbiological Analysis of Bloodstream Infections Caused by Chryseobacterium meningosepticum in Nonneonatal Patients 
Journal of Clinical Microbiology  2004;42(7):3353-3355.
Chryseobacterium meningosepticum bloodstream infections in 11 nonneonatal patients were reported. More than half of the infections were community acquired. PCR assays indicated that the organisms produced extended-spectrum β-lactamases as well as metallo-β-lactamases. Genotyping showed diverse fingerprints among the isolates. Six patients survived without appropriate antibiotic treatment. Host factors are the major determinant of the outcomes of C. meningosepticum infections.
PMCID: PMC446307  PMID: 15243115

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