Thirty-one Acinetobacter baumannii strains, comprising 14 strains from 14 outbreaks in different northwestern European cities and 17 sporadic strains, were compared by investigating various properties of the strains including biotype, antibiogram, cell envelope protein electrophoretic profile, ribotype pattern, and the band pattern generated by a novel genomic fingerprinting method, named AFLP, which is based on the selective amplification of restriction fragments. Results showed that 12 strains from unrelated outbreaks were linked together in two clusters according to their similarities by these typing methods, whereas sporadic strains were more heterogeneous. Outbreak strains appeared to be markedly more resistant to antibiotics than nonoutbreak strains. The uniformity of typing characters in two sets of outbreak strains suggests that strains in each cluster have a common clonal origin.
Extended-spectrum beta-lactamases (ESBLs) are an increasing cause of resistance to oxyimino-aminothiazolyl cephalosporins, especially in klebsiellae. In a recent survey we detected ESBLs in 220 (23%) of 966 consecutive klebsiellae from 35 intensive care units (ICUs) in southern and western Europe. The present study examined the extent to which this distribution reflected epidemic strain spread, as against the distribution of ESBL genes into unrelated strains. All 220 ESBL producers were subjected to capsular serotyping and pulsed-field gel DNA electrophoresis (PFGE). Beta-Lactamases were typed for strains isolated on three or more occasions, with the emphasis on SHV enzymes, as these were commoner than TEM variants. Serotyping and PFGE typing defined 85 distinct strains, from 23 of the 35 participating centres. Of 14 centres that contributed five or more ESBL producers, all sent representatives of more than one strain, and two centres sent members of ten or more different strains in contributions of 17-21 ESBL-producing isolates. Nevertheless, epidemic strains-defined as those represented by three or more isolates-accounted for a majority (61%) of the collection. Fifty-two isolates of the same serotype K25 (occasionally acapsular) strain with SHV-4 beta-lactamase were recovered at two French hospitals and one in Belgium. This strain has been found by others in France, and has become particularly widespread. Another single strain was found in two separate Portuguese centres, and many individual hospitals had one or more epidemic strain(s), as well as a scatter of diverse ESBL producers. Major variation in antibiogram and plasmid profile was apparent within strains, with some intra-strain variation in beta-lactamase type. These data imply a fluid situation, with resistance determinants being gained, modified or lost. The endemicity of ESBL producers is disturbing since it limits the potential for control by blocking strain spread, while the diversity within strains is disturbing because it complicates the design of antibiotic policies even during 'single strain' outbreaks.
Klebsiella pneumoniae and Klebsiella oxytoca are the two most frequently encountered Klebsiella species giving rise to infections in humans, but other Klebsiella species can also be found in clinical specimens: Klebsiella ozaenae, Klebsiella rhinoscleromatis, Klebsiella terrigena, Klebsiella planticola, Klebsiella ornithinolytica, and Enterobacter aerogenes (Klebsiella mobilis). However, many of these species are indistinguishable by the conventional methods employed routinely in the clinical microbiological laboratory. Several investigators have suggested various additional tests, but as yet there is no standardized test panel for identifying all Klebsiella species and subspecies. In the present study, performed in three national Klebsiella reference laboratories, we have evaluated a test panel consisting of 18 biochemical tests on 242 strains comprising all Klebsiella species and subspecies. The test panel was designed to identify organisms preliminarily identified as belonging to the genus Klebsiella on the basis of conventional methods or automated identification systems. With the described test panel it is possible to find one or more positive test results differentiating any Klebsiella species, except Klebsiella rhinoscleromatis, from its closest relative.
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