Klebsiella pneumoniae carbapenemase (KPC)-producing

In this investigation, exposure to duodenoscopes with bacterial contamination was associated with apparent transmission of NDM-producing E coli among patients at 1 hospital. Bacterial contamination of duodenoscopes appeared to persist despite the absence of recognized reprocessing lapses. Facilities should be aware of the potential for transmission of bacteria including antimicrobial-resistant organisms via this route and should conduct regular reviews of their duodenoscope reprocessing procedures to ensure optimal manual cleaning and disinfection.

In this population- and laboratory-based active surveillance system in 7 states, the incidence of CRE was 2.93 per 100<000 population. Most CRE cases were isolated from a urine source, and were associated with high prevalence of prior hospitalizations or indwelling devices, and discharge to long-term care settings.

The Klebsiella pneumoniae carbapenem (KPC) β-lactamase occurs in Enterobacteriaceae and can confer resistance to all β-lactam agents including carbapenems. The enzyme may confer low-level carbapenem resistance, and the failure of susceptibility methods to identify this resistance has been reported. Automated and nonautomated methods for carbapenem susceptibility were evaluated for identification of KPC-mediated resistance. Ertapenem was a more sensitive indicator of KPC resistance than meropenem and imipenem independently of the method used. Carbapenemase production could be confirmed with the modified Hodge test.

Multidrug-resistant Klebsiella pneumoniae producing the KPC carbapenemase have rapidly spread throughout the world, causing severe healthcare-associated infections with limited antimicrobial treatment options. Dissemination of KPC-producing K. pneumoniae is largely attributed to expansion of a single dominant strain, ST258. In this study, we explore phylogenetic relationships and evolution within ST258 and its clonal group, CG258, using whole genome sequence analysis of 167 isolates from 20 countries collected over 17 years. Our results show a common ST258 ancestor emerged from its diverse parental clonal group around 1995 and likely acquired bla KPC prior to dissemination. Over the past two decades, ST258 has remained highly clonal despite diversity in accessory elements and divergence in the capsule polysaccharide synthesis locus. Apart from the large recombination event that gave rise to ST258, few mutations set it apart from its clonal group. However, one mutation occurs in a global transcription regulator. Characterization of outer membrane protein sequences revealed a profile in ST258 that includes a truncated OmpK35 and modified OmpK37. Our work illuminates potential genomic contributors to the pathogenic success of ST258, helps us better understand the global dissemination of this strain, and identifies genetic markers unique to ST258.

Charcoal-yeast extract agar is a new bacteriological medium that supports excellent growth of the Legionella pneumophila. It results from modifications made in an existing L. pneumophila medium, F-G agar. Yeast extract, instead of an acid hydrolysate of casein, serves as the protein source. Beef extractives and starch are not added. Activated charcoal (Norit A or Norit SG) is included at 0.20% (wt/vol). Comparison of charcoal-yeast extract and F-G agars showed that a greater number of colony-forming units of L. pneumophila was recovered from a standardized tissue inoculum on charcoal-yeast extract agar (4.35 x 106 colonyforning units) than on F-G agar (4.85 x 104 colony-forming units). Macroscopic colonies of L. pneumophila were visible on the new medium within 3 days, whereas 4 days of growth was required on F-G agar. McDade et al. initially isolated the Legionnaires disease bacterium, now named Legionella pneumophila, by using guinea pigs and embryonated chicken eggs (2, 9). For the purpose of growing L. pneumophila on artificial media, Weaver inoculated 17 different bacteriological agars with an L. pneumophila-infected yolk sac suspension. Mueller-Hinton agar supplemented with 1% hemoglobin and 1% IsoVitaleX (BBL

Domestically acquired ceftriaxone-resistant Salmonella has emerged in the United States. Most ceftriaxone-resistant Salmonella isolates had similar AmpC plasmid-mediated resistance.

We investigated a Klebsiella oxytoca isolate demonstrating resistance to imipenem, meropenem, extendedspectrum cephalosporins, and aztreonam. The MICs of both imipenem and meropenem were 32 g/ml. The ␤-lactamase activity against imipenem and meropenem was inhibited in the presence of clavulanic acid. Isoelectric focusing studies demonstrated five ␤-lactamases with pIs of 8.2 (SHV-46), 6.7 (KPC-2), 6.5 (unknown), 6.4 (probable OXY-2), and 5.4 (TEM-1). The presence of the bla SHV and bla TEM genes was confirmed by specific PCR assays and DNA sequence analysis. Transformation and conjugation studies with Escherichia coli showed that the ␤-lactamase with a pI of 6.7, Klebsiella pneumoniae carbapenemase-2 (KPC-2), was encoded on an approximately 70-kb conjugative plasmid that also carried SHV-46, TEM-1, and the ␤-lactamase with a pI of 6.5. The bla KPC-2 determinant was cloned in E. coli and conferred resistance to imipenem, meropenem, extended-spectrum cephalosporins, and aztreonam. The amino acid sequence of KPC-2 showed a single amino acid difference, S174G, when compared with KPC-1, another carbapenem-hydrolyzing ␤-lactamase from K. pneumoniae 1534. Hydrolysis studies showed that purified KPC-2 hydrolyzed not only carbapenems but also penicillins, cephalosporins, and aztreonam. KPC-2 had the highest affinity for meropenem. The kinetic studies revealed that KPC-2 was inhibited by clavulanic acid and tazobactam. An examination of the outer membrane proteins of the parent K. oxytoca strain demonstrated that it expressed detectable levels of OmpK36 (the homolog of OmpC) and a higher-molecular-weight OmpK35 (the homolog of OmpF). Thus, carbapenem resistance in K. oxytoca 3127 is due to production of the Bush group 2f, class A, carbapenem-hydrolyzing ␤-lactamase KPC-2. This ␤-lactamase is likely located on a transposon that is part of a conjugative plasmid and thus has a very high potential for dissemination.