Acquired carbapenemases are emerging resistance determinants in Gram-negative pathogens, including Enterobacteriaceae, Pseudomonas aeruginosa and other Gram-negative non-fermenters. A consistent number of acquired carbapenemases have been identified during the past few years, belonging to either molecular class B (metallo-beta-lactamases) or molecular classes A and D (serine carbapenemases), and genes encoding these enzymes are associated with mobile genetic elements that allow their rapid dissemination in the clinical setting. Therefore, detection and surveillance of carbapenemase-producing organisms have become matters of major importance for the selection of appropriate therapeutic schemes and the implementation of infection control measures. As carbapenemase production cannot be simply inferred from the resistance profile, criteria must be established for which isolates should be suspected and screened for carbapenemase production, and for which tests (phenotypic and/or genotypic) should be adopted for confirmation of the resistance mechanism. Moreover, strategies should be devised for surveillance of carbapenemase producers in order to enable the implementation of effective surveillance programmes. The above issues are addressed in this article, as a follow-up to an expert meeting on acquired carbapenemases that was recently organized by the ESCMID Study Group for Antibiotic Resistance Surveillance.

A total of 904 consecutive nosocomial isolates of Escherichia coli and Klebsiella pneumoniae collected from 28 Russian hospitals were screened for production of extended-spectrum ␤-lactamases (ESBLs). The ESBL phenotype was detected in 78 (15.8%) E. coli and 248 (60.8%) K. pneumoniae isolates. One hundred fifteen isolates carried the genes for CTX-M-type ␤-lactamases, which, as shown by PCR-restriction fragment length polymorphism analysis, were distributed into the two genetic groups of CTX-M-1 (93%)-and CTX-M-2 (7%)-related enzymes. Isolates producing the enzymes of the first group were found in 20 hospitals from geographically distant regions of the country and were characterized by considerable diversity of genetic types, as was demonstrated by enterobacterial repetitive consensus PCR typing. Within this group the CTX-M-3 and the CTX-M-15 ␤-lactamases were identified. In contrast, the enzymes of the CTX-M-2 group (namely, CTX-M-5) were detected only in eight clonally related E. coli isolates from a single hospital. Notably, the levels of resistance to ceftazidime were remarkably variable among the CTX-M producers. This study provides further evidence of the global dissemination of CTX-M type ESBLs and emphasizes the need for their epidemiological monitoring.During the past decade extended-spectrum ␤-lactamases (ESBLs) of the CTX-M type emerged in many countries of the world. The first organisms producing ␤-lactamases of this type were identified both as single and epidemic clinical isolates in very distant geographic regions (Germany and France and Argentina) in the early 1990s (3, 5, 7). More recently, a rapid increase in the proportion of multiple CTX-M variants to the TEM-and SHV-derived ESBLs has been reported in many hospitals in Spain (9,12,15,35) (14), and Korea (28). Furthermore, CTX-M ␤-lactamases, mainly types CTX-M-2 and CTX-M-3, were found to be widespread or even predominant ESBL types in several countries, including Argentina (31, 34; M. Galas, F. Pasteran, R. Melano, A. Petroni, G. Lopez, A. Corso, A. Rossi, et al., Abstr. 38th Intersci. Conf. Antimicrob. Agents Chemother., abstr. E-109, 1998), Japan (41), and Poland (1).Currently the CTX-M family includes more than 20 ␤-lactamases, which may be grouped on the basis of sequence similarity into four distinct clusters (subtypes) epitomized by CTX-M-1, CTX-M-2, CTX-M-8, and CTX-M-9 (26, 37; http: //www.lahey.org/studies/webt.htm). Within each cluster there is a high degree of bla CTX-M gene sequence identity (Ͼ95%), although members of different subtypes share only 70 to 77% similarity at the nucleotide level. The recent finding of Kluyvera ascorbata species-specific ␤-lactamases (KluA) which share 98.6 to 100% identity with CTX-M-2 and CTX-M-5 and analysis of DNA sequences adjacent to the KluA-and CTX-Mcoding genes provide strong evidence of the direct evolution of the CTX-M-2 cluster from the chromosomal enzyme of K. ascorbata (20,36). Likewise, the chromosomal KLUG-1 enzyme of Kluyvera georgiana was found to be the most-probable progenitor of ...

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Acinetobacter baumannii is a gram-negative, non-fermenting aerobic bacterium which is often associated with hospital-acquired infections and known for its ability to develop resistance to antibiotics, form biofilms, and survive for long periods in hospital environments. In this study, we present two novel viruses, vB_AbaP_AS11 and vB_AbaP_AS12, specifically infecting and lysing distinct multidrug-resistant clinical A. baumannii strains with K19 and K27 capsular polysaccharide structures, respectively. Both phages demonstrate rapid adsorption, short latent periods, and high burst sizes in one-step growth experiments. The AS11 and AS12 linear double-stranded DNA genomes of 41,642 base pairs (bp) and 41,402 bp share 86% nucleotide sequence identity with the most variable regions falling in host receptor–recognition genes. These genes encode tail spikes possessing depolymerizing activities towards corresponding capsular polysaccharides which are the primary bacterial receptors. We described AS11 and AS12 genome organization and discuss the possible regulation of transcription. The overall genomic architecture and gene homology analyses showed that the phages are new representatives of the recently designated Fri1virus genus of the Autographivirinae subfamily within the Podoviridae family.