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2.  Population Structure of KPC-Producing Klebsiella pneumoniae Isolates from Midwestern U.S. Hospitals 
Genome sequencing of carbapenem-resistant Klebsiella pneumoniae isolates from regional U.S. hospitals was used to characterize strain diversity and the blaKPC genetic context. A phylogeny based on core single-nucleotide variants (SNVs) supports a division of sequence type 258 (ST258) into two distinct groups. The primary differences between the groups are in the capsular polysaccharide locus (cps) and their plasmid contents. A strict association between clade and KPC variant was found. The blaKPC gene was found on variants of two plasmid backbones. This study indicates that highly similar K. pneumoniae subpopulations coexist within the same hospitals over time.
PMCID: PMC4136011  PMID: 24913165
3.  Surveillance of Carbapenem-Resistant Klebsiella pneumoniae: Tracking Molecular Epidemiology and Outcomes through a Regional Network 
Carbapenem resistance in Gram-negative bacteria is on the rise in the United States. A regional network was established to study microbiological and genetic determinants of clinical outcomes in hospitalized patients with carbapenem-resistant (CR) Klebsiella pneumoniae in a prospective, multicenter, observational study. To this end, predefined clinical characteristics and outcomes were recorded and K. pneumoniae isolates were analyzed for strain typing and resistance mechanism determination. In a 14-month period, 251 patients were included. While most of the patients were admitted from long-term care settings, 28% of them were admitted from home. Hospitalizations were prolonged and complicated. Nonsusceptibility to colistin and tigecycline occurred in isolates from 7 and 45% of the patients, respectively. Most of the CR K. pneumoniae isolates belonged to repetitive extragenic palindromic PCR (rep-PCR) types A and B (both sequence type 258) and carried either blaKPC-2 (48%) or blaKPC-3 (51%). One isolate tested positive for blaNDM-1, a sentinel discovery in this region. Important differences between strain types were noted; rep-PCR type B strains were associated with blaKPC-3 (odds ratio [OR], 294; 95% confidence interval [CI], 58 to 2,552; P < 0.001), gentamicin nonsusceptibility (OR, 24; 95% CI, 8.39 to 79.38; P < 0.001), amikacin susceptibility (OR, 11.0; 95% CI, 3.21 to 42.42; P < 0.001), tigecycline nonsusceptibility (OR, 5.34; 95% CI, 1.30 to 36.41; P = 0.018), a shorter length of stay (OR, 0.98; 95% CI, 0.95 to 1.00; P = 0.043), and admission from a skilled-nursing facility (OR, 3.09; 95% CI, 1.26 to 8.08; P = 0.013). Our analysis shows that (i) CR K. pneumoniae is seen primarily in the elderly long-term care population and that (ii) regional monitoring of CR K. pneumoniae reveals insights into molecular characteristics. This work highlights the crucial role of ongoing surveillance of carbapenem resistance determinants.
PMCID: PMC4068524  PMID: 24798270
4.  Novel Bis-Indole Agents Active Against Multidrug-Resistant Acinetobacter baumannii 
The in vitro activity of five novel Microbiotix bis-indole agents (MBXs) against 30 multidrug-resistant (MDR) A. baumannii (including 18 resistant to carbapenems) was evaluated. Overall, MIC90s ranged from 1-8 μg/ml, whereas those for imipenem were > 64 μg/ml. MBX 1196 was the most potent (MIC90 1 μg/ml). MBXs are compounds that are highly effective against MDR A. baumannii.
PMCID: PMC3725720  PMID: 21146724
bis-indole; multidrug-resistant; MBX; susceptibility; in vitro
5.  Comparative Genomic Analysis of KPC-Encoding pKpQIL-Like Plasmids and Their Distribution in New Jersey and New York Hospitals 
The global spread of Klebsiella pneumoniae carbapenemase (KPC) is predominately associated with K. pneumoniae strains genotyped as sequence type 258 (ST258). The first ST258-associated plasmid, pKpQIL, was described in Israel in 2006, but its history in the northeastern United States remains unknown. Six pKpQIL-like plasmids from four K. pneumoniae isolates (three ST258 and one ST234), one Escherichia coli isolate, and one Enterobacter aerogenes isolate, collected from 2003 to 2010 in New York (NY) and New Jersey (NJ) hospitals, were completely sequenced. The sequences and overall sizes of the six plasmids are highly similar to those of pKpQIL; the major difference is that five of six NJ/NY strains harbor blaKPC-2, while pKpQIL contains blaKPC-3. Moreover, a 26.7-kb fragment was inverted in pKpQIL-234 (from ST234 K. pneumoniae), while a 14.5-kb region was deleted in pKpQIL-Ec (from ST131 E. coli). PCR screening of 284 other clinical K. pneumoniae isolates identified 101 (35.6%) harboring pKpQIL-like plasmids from 9 of 10 surveyed hospitals, demonstrating the wide dissemination of pKpQIL in this region of endemicity. Among the positive isolates, 87.1% were typed as ST258 and 88.1% carried blaKPC-2. The finding of pKpQIL-like plasmid in this study from strains that predate the initial report of KPC in Israel provides evidence that pKpQIL may have originated in the United States. Our findings demonstrate that pKpQIL plasmids are both spreading clonally in ST258 strains and spreading horizontally to different sequence types and species, further highlighting the clinical and public health concerns associated with carbapenem resistance.
PMCID: PMC3993205  PMID: 24614371
6.  Molecular Survey of the Dissemination of Two blaKPC-Harboring IncFIA Plasmids in New Jersey and New York Hospitals 
Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae strains have spread worldwide and become a major threat in health care facilities. Transmission of blaKPC, the plasmid-borne KPC gene, can be mediated by clonal spread and horizontal transfer. Here, we report the complete nucleotide sequences of two novel blaKPC-3-harboring IncFIA plasmids, pBK30661 and pBK30683. pBK30661 is 74 kb in length, with a mosaic plasmid structure; it exhibits homologies to several other plasmids but lacks the plasmid transfer operon (tra) and the origin of transfer (oriT) that are required for plasmid transfer. pBK30683 is a conjugative plasmid with a cointegrated plasmid structure, comprising a 72-kb element that highly resembles pBK30661 (>99.9% nucleotide identities) and an extra 68-kb element that harbors tra and oriT. A PCR scheme was designed to detect the distribution of blaKPC-harboring IncFIA (pBK30661-like and pBK30683-like) plasmids in a collection of clinical Enterobacteriaceae isolates from 10 hospitals in New Jersey and New York. KPC-harboring IncFIA plasmids were found in 20% of 491 K. pneumoniae isolates, and all carried blaKPC-3. pBK30661-like plasmids were identified mainly in the epidemic sequence type 258 (ST258) K. pneumoniae clone, while pBK30683-like plasmids were widely distributed in ST258 and other K. pneumoniae sequence types and among non-K. pneumoniae Enterobacteriaceae species. This suggests that both clonal spread and horizontal plasmid transfer contributed to the dissemination of blaKPC-harboring IncFIA plasmids in our area. Further studies are needed to understand the distribution of this plasmid group in other health care regions and to decipher the origins of pBK30661-like and pBK30683-like plasmids.
PMCID: PMC4023724  PMID: 24492370
7.  Complete Sequence of a KPC-Producing IncN Multidrug-Resistant Plasmid from an Epidemic Escherichia coli Sequence Type 131 Strain in China 
We report here the nucleotide sequence of a novel blaKPC-2-harboring incompatibility group N (IncN) plasmid, pECN580, from a multidrug-resistant Escherichia coli sequence type 131 (ST131) isolate recovered from Beijing, China. pECN580 harbors β-lactam resistance genes blaKPC-2, blaCTX-M-3, and blaTEM-1; aminoglycoside acetyltransferase gene aac(6′)-Ib-cr; quinolone resistance gene qnrS1; rifampin resistance gene arr-3; and trimethoprim resistance gene dfrA14. The emergence of a blaKPC-2-harboring multidrug-resistant plasmid in an epidemic E. coli ST131 clone poses a significant potential threat in community and hospital settings.
PMCID: PMC4023777  PMID: 24395232
8.  Coccidioides Thyroiditis in an HIV-Infected Patient 
Journal of Clinical Microbiology  2012;50(7):2535-2537.
We report a case of Coccidioides thyroiditis in an HIV-infected patient with a history of recent Coccidioides pneumonia but with negative Coccidioides serology determined by enzyme immunoassay at presentation. Diagnosis of Coccidioides thyroiditis was made based on histopathologic examination and culture of thyroid abscess material obtained by fine-needle aspiration biopsy.
PMCID: PMC3405633  PMID: 22518870
9.  Disseminated Mycobacterium chelonae Infection in a Patient Receiving an Epidermal Growth Factor Receptor Inhibitor for Advanced Head and Neck Cancer 
Journal of Clinical Microbiology  2012;50(1):194-195.
We report a case of disseminated cutaneous Mycobacterium chelonae infection in a patient with head and neck cancer on salvage chemotherapy, including the epidermal growth factor receptor inhibitor cetuximab. Mycobacterium chelonae should be considered in the differential diagnosis of cutaneous infections in cancer patients receiving epidermal growth factor receptor inhibitors.
PMCID: PMC3256709  PMID: 22031707
10.  Complete Nucleotide Sequence of a blaKPC-Harboring IncI2 Plasmid and Its Dissemination in New Jersey and New York Hospitals 
Antimicrobial Agents and Chemotherapy  2013;57(10):5019-5025.
Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae strains have spread worldwide and become a significant public health threat. blaKPC, the plasmid-borne KPC gene, was frequently identified on numerous transferable plasmids in different incompatibility replicon groups. Here we report the complete nucleotide sequence of a novel blaKPC-3-harboring IncI2 plasmid, pBK15692, isolated from a multidrug-resistant K. pneumoniae ST258 strain isolated from a New Jersey hospital in 2005. pBK15692 is 78 kb in length and carries a backbone that is similar to those of other IncI2 plasmids (pR721, pChi7122-3, pHN1122-1, and pSH146-65), including the genes encoding type IV pili and shufflon regions. Comparative genomics analysis of IncI2 plasmids reveals that they possess a conserved plasmid backbone but are divergent with respect to the integration sites of resistance genes. In pBK15692, the blaKPC-3-harboring Tn4401 was inserted into a Tn1331 element and formed a nested transposon. A PCR scheme was designed to detect the prevalence of IncI2 and pBK15692-like plasmids from a collection of clinical strains from six New Jersey and New York hospitals isolated between 2007 and 2011. IncI2 plasmids were found in 46.2% isolates from 318 clinical K. pneumoniae strains. Notably, 59 pBK15692-like plasmids (23%) have been identified in 256 KPC-bearing K. pneumoniae strains, and all carried KPC-3 and belong to the epidemic ST258 clone. Our study revealed that the prevalence of IncI2 plasmids has been considerably underestimated. Further studies are needed to understand the distribution of this plasmid group in other health care regions and decipher the association between IncI2 plasmids and blaKPC-3-bearing ST258 strains.
PMCID: PMC3811408  PMID: 23896467
12.  Pneumococcal Capsular Switching: A Historical Perspective 
The Journal of Infectious Diseases  2012;207(3):439-449.
Background. Changes in serotype prevalence among pneumococcal populations result from both serotype replacement and serotype (capsular) switching. Temporal changes in serotype distributions are well documented, but the contribution of capsular switching to such changes is unknown. Furthermore, it is unclear to what extent vaccine-induced selective pressures drive capsular switching.
Methods. Serotype and multilocus sequence typing data for 426 pneumococci dated from 1937 through 2007 were analyzed. Whole-genome sequence data for a subset of isolates were used to investigate capsular switching events.
Results. We identified 36 independent capsular switch events, 18 of which were explored in detail with whole-genome sequence data. Recombination fragment lengths were estimated for 11 events and ranged from approximately 19.0 kb to ≥58.2 kb. Two events took place no later than 1960, and the imported DNA included the capsular locus and the nearby penicillin-binding protein genes pbp2x and pbp1a.
Conclusions. Capsular switching has been a regular occurrence among pneumococcal populations throughout the past 7 decades. Recombination of large DNA fragments (>30 kb), sometimes including the capsular locus and penicillin-binding protein genes, predated both vaccine introduction and widespread antibiotic use. This type of recombination has likely been an intrinsic feature throughout the history of pneumococcal evolution.
PMCID: PMC3537446  PMID: 23175765
Capsule; serotype; switching; pneumococcus
14.  Answer to August 2013 Photo Quiz 
PMCID: PMC3719610
15.  Diversity of Virulence Phenotypes among Type III Secretion Negative Pseudomonas aeruginosa Clinical Isolates 
PLoS ONE  2014;9(1):e86829.
Pseudomonas aeruginosa is a frequent cause of acute infections. The primary virulence factor that has been linked to clinical disease is the type III secretion system, a molecular syringe that delivers effector proteins directly into host cells. Despite the importance of type III secretion in dictating clinical outcomes and promoting disease in animal models of infections, clinical isolates often do not express the type III secretion system in vitro. Here we screened 81 clinical P. aeruginosa isolates for secretion of type III secretion system substrates by western blot. Non-expressing strains were also subjected to a functional test assaying the ability to intoxicate epithelial cells in vitro, and to survive and cause disease in a murine model of corneal infection. 26 of 81 clinical isolates were found to be type III secretion negative by western blot. 17 of these 26 non-expressing strains were tested for their ability to cause epithelial cell rounding. Of these, three isolates caused epithelial cell rounding in a type III secretion system dependent manner, and one strain was cytotoxic in a T3SS-independent manner. Five T3SS-negative isolates were also tested for their ability to cause disease in a murine model of corneal infection. Of these isolates, two strains caused severe corneal disease in a T3SS-independent manner. Interestingly, one of these strains caused significant disease (inflammation) despite being cleared. Our data therefore show that P. aeruginosa clinical isolates can cause disease in a T3SS-independent manner, demonstrating the existence of novel modifiers of clinical disease.
PMCID: PMC3900666  PMID: 24466261
16.  New Insights into Dissemination and Variation of the Health Care-Associated Pathogen Acinetobacter baumannii from Genomic Analysis 
mBio  2014;5(1):e00963-13.
Acinetobacter baumannii is a globally important nosocomial pathogen characterized by an increasing incidence of multidrug resistance. Routes of dissemination and gene flow among health care facilities are poorly resolved and are important for understanding the epidemiology of A. baumannii, minimizing disease transmission, and improving patient outcomes. We used whole-genome sequencing to assess diversity and genome dynamics in 49 isolates from one United States hospital system during one year from 2007 to 2008. Core single-nucleotide-variant-based phylogenetic analysis revealed multiple founder strains and multiple independent strains recovered from the same patient yet was insufficient to fully resolve strain relationships, where gene content and insertion sequence patterns added additional discriminatory power. Gene content comparisons illustrated extensive and redundant antibiotic resistance gene carriage and direct evidence of gene transfer, recombination, gene loss, and mutation. Evidence of barriers to gene flow among hospital components was not found, suggesting complex mixing of strains and a large reservoir of A. baumannii strains capable of colonizing patients.
Genome sequencing was used to characterize multidrug-resistant Acinetobacter baumannii strains from one United States hospital system during a 1-year period to better understand how A. baumannii strains that cause infection are related to one another. Extensive variation in gene content was found, even among strains that were very closely related phylogenetically and epidemiologically. Several mechanisms contributed to this diversity, including transfer of mobile genetic elements, mobilization of insertion sequences, insertion sequence-mediated deletions, and genome-wide homologous recombination. Variation in gene content, however, lacked clear spatial or temporal patterns, suggesting a diverse pool of circulating strains with considerable interaction between strains and hospital locations. Widespread genetic variation among strains from the same hospital and even the same patient, particularly involving antibiotic resistance genes, reinforces the need for molecular diagnostic testing and genomic analysis to determine resistance profiles, rather than a reliance primarily on strain typing and antimicrobial resistance phenotypes for epidemiological studies.
PMCID: PMC3903280  PMID: 24449752
17.  Complete Sequence of a blaKPC-2-Harboring IncFIIK1 Plasmid from a Klebsiella pneumoniae Sequence Type 258 Strain 
We report the nucleotide sequence of a novel blaKPC-2-harboring IncFIIK1 plasmid, pBK32179, isolated from a carbapenem-resistant Klebsiella pneumoniae ST258 strain from a New York City patient. pBK32179 is 165 kb long, consists of a large backbone of pKPN3-like plasmid, and carries an 18.5-kb blaKPC-2-containing element that is highly similar to plasmid pKpQIL. pBK32179-like plasmids were identified in 8.3% of strains in a collection of 96 K. pneumoniae isolates from hospitals in the New York City area.
PMCID: PMC3591897  PMID: 23295924
18.  Use of Vaporized Hydrogen Peroxide Decontamination during an Outbreak of Multidrug-Resistant Acinetobacter baumannii Infection at a Long-Term Acute Care Hospital 
To describe vaporized hydrogen peroxide (VHP) as an adjuvant in the control of multidrug-resistant (MDR) Acinetobacter baumannii infection in a long-term acute care hospital (LTACH) and to describe the risk factors for acquisition of MDR A. baumannii infection in the LTACH population.
Outbreak investigation, case-control study, and before-after intervention trial.
A 54-bed LTACH affiliated with a tertiary care center in northeastern Ohio.
Investigation of outbreak with clinical and environmental cultures, antimicrobial susceptibility testing, polymerase chain reaction assay of repetitive chromosomal elements to type strains, and case-control study; and intervention consisting of comprehensive infection control measures and VHP environmental decontamination.
Thirteen patients infected or colonized with MDR A. baumannii were identified from January 2008 through June 2008. By susceptibility testing, 10 (77%) of the 13 isolates were carbapenem-resistant. MDR A. baumannii was found in wound samples, blood, sputum, and urine. Wounds were identified as a risk factor for MDR A. baumannii colonization. Ventilator–associated pneumonia was the most common clinical syndrome caused by the pathogen, and the associated mortality was 14% (2 of the 13 case patients died). MDR A. baumannii was found in 8 of 93 environmental samples, including patient rooms and a wound care cart; environmental and clinical cultures were genetically related. Environmental cultures were negative immediately after VHP decontamination and both 24 hours and 1 week after VHP decontamination. Nosocomial acquisition of the pathogen in the LTACH ceased after VHP intervention. When patients colonized with MDR A. baumannii reoccupied rooms, environmental contamination recurred.
Environmental decontamination using VHP combined with comprehensive infection control measures interrupted nosocomial transmission of MDR A. baumannii in an LTACH. The application of this novel approach to halt the transmission of MDR A. baumannii warrants further investigation.
PMCID: PMC3731999  PMID: 20973723
19.  Complete Nucleotide Sequences of blaKPC-4- and blaKPC-5-Harboring IncN and IncX Plasmids from Klebsiella pneumoniae Strains Isolated in New Jersey 
Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae have emerged as major nosocomial pathogens. blaKPC, commonly located on Tn4401, is found in Gram-negative bacterial strains, with the two most common variants, blaKPC-2 and blaKPC-3, identified in plasmids with diverse genetic backgrounds. In this study, we examined blaKPC-4- and blaKPC-5-bearing plasmids recovered from two K. pneumoniae strains, which were isolated from a single New Jersey hospital in 2005 and 2006, respectively. IncN plasmid pBK31551 is 84 kb in length and harbors blaKPC-4, blaTEM-1, qnrB2, aac(3)-Ib, aph(3′)-I, qacF, qacEΔ1, sul1, and dfrA14, which confer resistance to β-lactams, quinolones, aminoglycosides, quaternary ammonium compounds, and co-trimoxazole. The conserved regions within pBK31551 are similar to those of other IncN plasmids. Surprisingly, analysis of the Tn4401 sequence revealed a large IS110- and Tn6901-carrying element (8.3 kb) inserted into the istA gene, encoding glyoxalase/bleomycin resistance, alcohol dehydrogenase, and S-formylglutathione hydrolase. Plasmid pBK31567 is 47 kb in length and harbors blaKPC-5, dfrA5, qacEΔ1, and sul1. pBK31567 belongs to a novel IncX subgroup (IncX5) and possesses a highly syntenic plasmid backbone like other IncX plasmids; however, sequence similarity at the nucleotide level is divergent. The blaKPC-5 gene is carried on a Tn4401 element and differs from the genetic environment of blaKPC-5 described in Pseudomonas aeruginosa strain P28 from Puerto Rico. This study underscores the genetic diversity of multidrug-resistant plasmids involved in the spread of blaKPC genes and highlights the mobility and plasticity of Tn4401. Comparative genomic analysis provides new insights into the evolution and dissemination of KPC plasmids belonging to different incompatibility groups.
PMCID: PMC3535970  PMID: 23114770
20.  “Silent” Dissemination of Klebsiella pneumoniae Isolates Bearing K. pneumoniae Carbapenemase in a Long-term Care Facility for Children and Young Adults in Northeast Ohio 
Our findings reveal that in 2004 the blaKPC-3 gene was present in a children’s long-term healthcare facility. This suggests pockets of Klebsiella pneumoniae carbapenemase–producing K. pneumoniae independent from sequence type 258 existing in locations not identified at that time.
Background. Klebsiella pneumoniae isolates harboring the K. pneumoniae carbapenemase gene (blaKPC) are creating a significant healthcare threat in both acute and long-term care facilities (LTCFs). As part of a study conducted in 2004 to determine the risk of stool colonization with extended-spectrum cephalosporin-resistant gram-negative bacteria, 12 isolates of K. pneumoniae that exhibited nonsusceptibility to extended-spectrum cephalosporins were detected. All were gastrointestinal carriage isolates that were not associated with infection.
Methods. Reassessment of the carbapenem minimum inhibitory concentrations using revised 2011 Clinical Laboratory Standards Institute breakpoints uncovered carbapenem resistance. To further investigate, a DNA microarray assay, PCR-sequencing of bla genes, immunoblotting, repetitive-sequence-based PCR (rep-PCR) and multilocus sequence typing (MLST) were performed.
Results. The DNA microarray detected blaKPC in all 12 isolates, and blaKPC-3 was identified by PCR amplification and sequencing of the amplicon. In addition, a blaSHV-11 gene was detected in all isolates. Immunoblotting revealed “low-level” production of the K. pneumoniae carbapenemase, and rep-PCR indicated that all blaKPC-3-positive K. pneumoniae strains were genetically related (≥98% similar). According to MLST, all isolates belonged to sequence type 36. This sequence type has not been previously linked with blaKPC carriage. Plasmids from 3 representative isolates readily transferred the blaKPC-3 to Escherichia coli J-53 recipients.
Conclusions. Our findings reveal the “silent” dissemination of blaKPC-3 as part of Tn4401b on a mobile plasmid in Northeast Ohio nearly a decade ago and establish the first report, to our knowledge, of K. pneumoniae containing blaKPC-3 in an LTCF caring for neurologically impaired children and young adults.
PMCID: PMC3404693  PMID: 22492318
21.  The multidrug-resistant PMEN1 pneumococcus is a paradigm for genetic success 
Genome Biology  2012;13(11):R103.
Streptococcus pneumoniae, also called the pneumococcus, is a major bacterial pathogen. Since its introduction in the 1940s, penicillin has been the primary treatment for pneumococcal diseases. Penicillin resistance rapidly increased among pneumococci over the past 30 years, and one particular multidrug-resistant clone, PMEN1, became highly prevalent globally. We studied a collection of 426 pneumococci isolated between 1937 and 2007 to better understand the evolution of penicillin resistance within this species.
We discovered that one of the earliest known penicillin-nonsusceptible pneumococci, recovered in 1967 from Australia, was the likely ancestor of PMEN1, since approximately 95% of coding sequences identified within its genome were highly similar to those of PMEN1. The regions of the PMEN1 genome that differed from the ancestor contained genes associated with antibiotic resistance, transmission and virulence. We also revealed that PMEN1 was uniquely promiscuous with its DNA, donating penicillin-resistance genes and sometimes many other genes associated with antibiotic resistance, virulence and cell adherence to many genotypically diverse pneumococci. In particular, we describe two strains in which up to 10% of the PMEN1 genome was acquired in multiple fragments, some as long as 32 kb, distributed around the recipient genomes. This type of directional genetic promiscuity from a single clone to numerous unrelated clones has, to our knowledge, never before been described.
These findings suggest that PMEN1 is a paradigm of genetic success both through its epidemiology and promiscuity. These findings also challenge the existing views about horizontal gene transfer among pneumococci.
PMCID: PMC3580495  PMID: 23158461
22.  Partial Excision of blaKPC from Tn4401 in Carbapenem-Resistant Klebsiella pneumoniae 
We describe a novel Tn4401 variant (Tn4401d) in epidemic Klebsiella pneumoniae clone ST258, from which a partial blaKPC fragment has been excised along with ISKpn7 and a partial tnpA fragment. Nested-PCR experiments confirmed that this region can be removed from distinct Tn4401 isoforms in both K. pneumoniae and Escherichia coli. This study highlights that the region surrounding blaKPC is undergoing recombination and that Tn4401 itself is heterogeneous and highly plastic.
PMCID: PMC3294926  PMID: 22203593
23.  Cefotaxime-Resistant Bacteria Colonizing Older People Admitted to an Acute Care Hospital 
To determine the frequency of fecal colonization by cefotaxime-resistant gram-negative bacilli in older patients living in the community and in long-term care facilities (LTCFs) admitted to an acute care hospital.
Case-control, point prevalence study.
One hundred forty-three patients aged 65 and older.
Rectal swab cultures, antibiotic drug sensitivity, beta lactamase isolation, and clonal identity.
Of the 190 surveillance cultures obtained from 143 patients, 26 cefotaxime-resistant gram-negative isolates from 22 patients were recovered. The prevalence rate of cefotaxime-resistant isolates on admission was 13.3% (19/143). A logistic regression model using cefotaxime colonization as the dependent variable found that multiple comorbidities, admission to a surgical service, and having a diagnosis of infection on presentation and a transfusion history were factors associated with the presence of colonization. These four clinical items accurately classified 74% of patients colonized. Antibiotic use and nursing home residence were not associated with the presence of colonization by cefotaxime-resistant organisms. Twelve of the cefotaxime-resistant isolates (46%) were identified as Pseudomonas aeruginosa, and 14 (54%) were other gram-negative bacilli. In six of the 14 isolates that were not P. aeruginosa (36%), it was possible to demonstrate the presence of an AmpC β-lactamase related to the CMY-2 β-lactamase, a plasmid-borne cephalosporinase.
These data raise awareness that there are community- and LTCF-dwelling older patients colonized with gram-negative enteric bacilli resistant to third-generation cephalosporins on admission to the hospital. The “reservoir of resistant bacteria” in older people is no longer confined to LTCFs.
PMCID: PMC3419475  PMID: 12657072
cefotaxime; cephalosporinase; long-term care facilities; antibiotic resistance
24.  Are We Ready for Novel Detection Methods to Treat Respiratory Pathogens in Hospital-Acquired Pneumonia? 
Hospital-acquired pneumonia represents one of the most difficult treatment challenges in infectious diseases. Many studies suggest that the timely administration of appropriate, pathogen-directed therapy can be lifesaving. Because results of culture and antimicrobial susceptibility testing can take 48 h or longer, physicians currently rely on clinical, epidemiological, and demographic factors to assist with the choice of empiric therapy for antibiotic-resistant pathogens. At present, a number of rapid molecular tests are being developed that identify pathogens and the presence of genetic determinants of antimicrobial resistance (eg, GeneXpert [Cepheid], ResPlex [Qiagen], FilmArray [Idaho Technologies], and Microarray [Check-Points]). In this review, the potential impact that molecular diagnostics has to identify and characterize pathogens that cause hospital-acquired bacterial pneumonia at an early stage is examined. In addition, a perspective on a novel technology, polymerase chain reaction followed by electrospray ionization mass spectrometry, is presented, and its prospective use in the diagnosis of pneumonia is also discussed. The complexities of the pulmonary microbiome represent a novel challenge to clinicians, but many questions still remain even as these technologies improve.
PMCID: PMC3106236  PMID: 21460299
25.  Longitudinal Analysis of the Temporal Evolution of Acinetobacter baumannii Strains in Ohio, USA, by Using Rapid Automated Typing Methods 
PLoS ONE  2012;7(4):e33443.
Genotyping methods are essential to understand the transmission dynamics of Acinetobacter baumannii. We examined the representative genotypes of A. baumannii at different time periods in select locations in Ohio, using two rapid automated typing methods: PCR coupled with electrospray ionization mass spectrometry (PCR/ESI-MS), a form of multi-locus sequence typing (MLST), and repetitive-sequence-based-PCR (rep-PCR). Our analysis included 122 isolates from 4 referral hospital systems, in 2 urban areas of Ohio. These isolates were associated with outbreaks at 3 different time periods (1996, 2000 and 2005–2007). Type assignments of PCR/ESI-MS and rep-PCR were compared to each other and to worldwide (WW) clone types. The discriminatory power of each method was determined using the Simpson's index of diversity (DI). We observed that PCR/ESI-MS sequence type (ST) 14, corresponding to WW clone 3, predominated in 1996, whereas ST 12 and 14 co-existed in the intermediate period (2000) and ST 10 and 12, belonging to WW clone 2, predominated more recently in 2007. The shift from WW clone 3 to WW clone 2 was accompanied by an increase in carbapenem resistance. The DI was approximately 0.74 for PCR/ESI-MS, 0.88 for rep-PCR and 0.90 for the combination of both typing methods. We conclude that combining rapid automated typing methods such as PCR/ESI-MS and rep-PCR serves to optimally characterize the regional molecular epidemiology of A. baumannii. Our data also sheds light on the changing sequence types in an 11 year period in Northeast Ohio.
PMCID: PMC3325217  PMID: 22511922

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