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Posters from 45th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC)
(December 16-19, 2005, Washington, DC Convention Center)
- Rapid Country-Wide Dissemination of Nosocomial CTX-M-14-β-Lactamase-Producing Strains in Russia
M. Stepanova, E. Ryabkova, M. Edelstein, L. Stratchounski
Over the last years, the CTX-M-type extended-spectrum β-lactamases (ESBLs) have become widespread in many parts of the world. β-Lactamases of the CTX-M-9 genetic cluster, especially the CTX-M-9 and CTX-M-14, have been reported as one of the prevailing ESBL types in Spain, Korea, China and Canada, and have been identified in many other countries.
During the late 1990's, CTX-M ESBLs were already common among nosocomial Enterobacteriaceae in Russia. However, only the members of the CTX-M-1 and CTX-M-2 clusters were detected in the national survey at that time. The more recent epidemiological surveillance confirmed the predominance of the CTX-M-1-cluster ESBLs, namely the CTX-M-3 and CTX-M-15, and also revealed for the first time the production of CTX-M-9-related enzymes in nosocomial strains from various cities of Russia. This study was focused on the molecular analysis of the latter group of strains.
- In Vivo Evolution and Emergence of a New CTX-M β-Lactamase with “Ceftazidimase” Activity in a Hypermutable Clinical Strain
M. Stepanova, M. Edelstein, L. Stratchounski
The family of CTX-M β-lactamases is rapidly growing and currently includes at least 50 enzymes. CTX-Ms generally have higher activity against cefotaxime (CTX) than against ceftazidime (CAZ). Recently, twelve CTX-M variants have been reported to contain point mutations at positions 167 or 240 associated with increased CAZ hydrolyzing activity. These include six enzymes of the CTX-M-1 cluster: CTX-M-15, -23, -28, -29, -32, -33; two enzymes of the CTX-M-2 cluster: CTX-M-35, -43; three enzymes of the CTX-M-9 cluster: CTX-M-16, -19, -27; and CTX-M-25. The CTX-Ms containing mutations at position 167 have been shown to confer higher levels of resistance to CAZ than to CTX, and thus could be defined as “ceftazidimases”.
During a survey of ESBL producers, an E.coli clinical isolate (Irk2320) was identified that produced a single CTX-M β-lactamase and expressed an unusual resistance phenotype being moderately resistant to cefotaxime (MIC 8 mg/L) but highly resistant to ceftazidime (MIC 128 mg/L). Notably, this isolate was obtained from a patient who had been treated with CAZ. The second E.coli isolate (Irk2322) with identical phenotype of resistance was isolated from another patient in the same ward one month later.
In this study we aimed to investigate whether resistance to CAZ arose in vivo as a result of mutation(s) in a CTX-M β-lactamase.
- Molecular Characterization of Metallo-β-Lactamase (MBL)-Producing Pseudomonas aeruginosa Strains from Russia
O. Shevchenko, V. Kretchikov, M. Edelstein, L. Stratchounski
Carbapenems have potent antibacterial activity and are mainly reserved for the treatment of infections caused by multiresistant nosocomial pathogens, including Pseudomonas aeruginosa. However, isolates of this species can develop resistance to carbapenems through alteration of outer membrane permeability, activation of efflux systems or acquisition of carbapenem-hydrolyzing β-lactamases. Production of acquired metallo-β-lactamases (MBLs) is probably the most important mechanism of resistance to carbapenems both in terms of its effectiveness and epidemiological significance. The MBL-producing P.aeruginosa strains have been reported worldwide but predominantly in South East Asia and Europe. This study aimed to determine the types of MBLs produced by Russian P.aeruginosa strains and to assess their possible genetic relationship.
- Continuous Spread of ESBL-Producing Salmonellae in Russian Hospitals
A. Narezkina, M. Stepanova, M. Edelstein, L. Stratchounski
Emergence of multi-drug resistant salmonellae is an important chemotherapeutic problem worldwide. Severe salmonellosis, especially in children, is often treated empirically with expanded-spectrum cephalosporins (ESCs). Therefore, the spread of ESC-resistant salmonellae is of particular concern in terms of possible therapeutic setback. Several plasmid mediated extended-spectrum β-lactamases (ESBLs), in particular, the enzymes of the CTX-M group, are known to confer ESC-resistance phenotype in Salmonella spp.
In our previous study we revealed the clonal origin of 34 ESC-resistant Salmonella serovar Typhimurium (ST) isolates from multiple nosocomial outbreaks of gastroenteritis in Russia and Belarus in 1994-2003. All the isolates were found to produce the CTX-M-5 ESBL encoded by small non-self-transferable plasmid.
In the years 2003-2004 an active surveillance program was initiated by the Institute of Antimicrobial Chemotherapy with the aim to trace the possible dissemination of ESC-resistant salmonellae in the hospitals throughout Russia. A total of eleven ESC-resistant nosocomial isolates of ST and one strain of Salmonella serovar Infantis (SInf) were collected in six hospitals, including five newly surveyed centers, of four geographically distant Russian cities. In the present study we explored the mechanisms of ESC resistance in these strains and their potential relation to the previously characterized ST clone.
- Antimicrobial Resistance of Nosocomial Strains of Enterococcus spp. in Russian ICUs: Results of Multicenter Study
A.V. Dekhnitch, E.L. Ryabkova, O.I. Kretchikova, M.V. Sukhorukova, L.S. Stratchounski
Enterococci are the well-recognised cause of infections in human, especially in inpatients with corresponding risk factors. E.faecalis is a predominant pathogen that accounts for more than 75% of all cases of enterococcal infections, followed by E.faecium. Other enterococci are usually isolated from clinical specimens. The most important problem in enterococcal infections is the resistance to antimicrobials, especially in ICUs. At the same time there are limited data on epidemiology of antibimicrobial resistance of enterococci in ICUs in Russia. So, the aim of our study was to determine the rates of antimicrobial resistance in nosocomial strains of Enterococcus spp. in Russian ICUs.
- Antimicrobial Resistance among Nosocomial Klebsiella pneumoniae from Russian Intensive Care Units (ICUs)
G. Reshedko, E. Ryabkova, O. Kretchikova, M. Sukhorukova, M. Edelstein, RosNet Group
Despite implementation of infection control measures, hospitalacquired or nosocomial infections remain a serious problem for healthcare, especially for ICUs where risk for nosocomial infections is up to 10 times greater than in other wards. Gram-negative pathogens, namely Enterobacteriaceae are responsible for a large number of nosocomial infection in ICUs with K.pneumoniae being one the most important pathogen accounted for. Since emergence of extended spectrum β-lactamases (ESBL) therapeutic options for this nosocomial disaster became limited. The situation is worsened due to wide spread of co-resistance to other antimicrobial classes (e.g. fluoroquinolones, aminoglycosides) among ESBL-producing K.pneumoniae.
Data about current state of antimicrobial resistance in nosocomial K.pneumoniae in Russian ICUs are scarce and the objective of our study was to clarify this issue.
The last modification date: December 21, 2005
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