Twelve consecutive carbapenem-resistant Escherichia coli isolates were recovered from patients (infection or colonization) hospitalized between March and September 2012 in different units at a hospital in Bulgaria. They all produced the carbapenemase NDM-1 and the extended-spectrum--lactamase CTX-M-15, together with the 16S rRNA methylase RmtB, conferring high-level resistance to all aminoglycosides. All those isolates were clonally related and belonged to the same sequence type, ST101. In addition to being the first to identify NDM-producing isolates in Bulgaria, this is the very first study reporting an outbreak of NDM-1-producing E. coli in the world. W orldwide occurrence of carbapenemase producers amongEnterobacteriaceae is now well recognized (1, 2). In Europe, there are distinct epidemiological situations corresponding mainly to the diffusion of OXA-48 producers in France, Belgium, The Netherlands, and Turkey (3, 4) and KPC-producing isolates in Italy and Greece (5), while some countries show more diverse distributions, such as in the United Kingdom, where KPC, OXA-48, VIM, and NDM-1 producers are being found (6). The recent emergence of NDM-1 producers (mostly Klebsiella pneumoniae isolates) is often related to imported cases, with a link to the Indian subcontinent (7). In addition, there are sporadic reports of NDM-1 producers (Enterobacteriaceae, Acinetobacter baumannii, and Pseudomonas aeruginosa) originating from countries of the Middle East or the Balkan region, including Croatia, Kosovo, and Serbia (7,8). Very little information is available regarding the diffusion of carbapenemase producers in Eastern Europe. Therefore, our study aimed to characterize the mechanisms responsible for carbapenem resistance by investigating a collection of enterobacterial isolates recovered in Bulgaria. From March to September 2012, 12 Escherichia coli isolates being resistant to carbapenems were recovered at the Military Medical Academy hospital of Sofia, Bulgaria. Susceptibility testing was performed by disk diffusion on solid agar plates following the CLSI recommendations (9). Those isolates had been recovered from urine (n ϭ 4), blood (n ϭ 1), respiratory specimens (n ϭ 2), wound (n ϭ 1), catheter (n ϭ 1), abdominal exudate (n ϭ 1), and rectal swabs (n ϭ 2). The MICs of carbapenems were determined by Etest (AB bioMérieux, La Balme-les-Grottes, France) on Mueller-Hinton agar plates at 37°C, and results of susceptibility testing were interpreted according to the CLSI guidelines (10). The MICs of imipenem, meropenem, and ertapenem were 32, Ͼ32, and Ͼ32 g/ml for all the E. coli isolates, respectively. They were resistant to all -lactams, including broad-spectrum cephalosporins (MICs of ceftazidime and cefotaxime being Ͼ32 g/ml) ( Table 1). In addition, they were resistant to all tested aminoglycosides (amikacin, gentamicin, netilmicin, kanamycin) and to fluoroquinolones and sulfonamides. Using the Etest, the MIC of rifampin was elevated (128 g/ml), and that of colistin was found to be 0.5 g/ml.Carbapenemase detecti...
The aim of the study was to decipher the mechanisms and associated genetic determinants responsible for increased carbapenem resistance among Proteus mirabilis clinical isolates. Methods: The entire genetic structure surrounding the b-lactam resistance genes was characterized by PCR, gene walking, and DNA sequencing. Results: A series of clinical P. mirabilis isolates were consecutively recovered from different patients at the Military hospital of Sofia, Bulgaria. They showed variable levels of resistance to carbapenems. All isolates produced the same carbapenemase VIM-1 that was chromosomally encoded. We showed that increased resistance to carbapenems was related to an increased number of bla VIM-1 gene copies. Conclusion: We showed here that increased carbapenem resistance in P. mirabilis may result from increased expression of the bla VIM-1 carbapenemase gene through multiplication of its copy number.
We characterized 72 isolates with reduced susceptibility to carbapenems (50 Acinetobacter spp., 13 Proteus mirabilis, five Escherichia coli, one Morganella morganii, one Enterobacter cloacae, one Providencia rettgeri, and one Pseudomonas aeruginosa) from a hospital in Sofia, Bulgaria. Different β-lactamase genes were identified by polymerase chain reaction and sequencing. Bacterial strain typing was performed by enzymatic macrorestriction and pulsed-field gel electrophoresis (PFGE) typing as well as multilocus sequence typing for selected isolates. The majority of Acinetobacter baumannii (46/50) and one Acinetobacter pittii isolate harbored carbapenemase genes bla or bla; two A. baumannii contained both genes. PFGE typing of all A. baumannii showed the presence of nine different clones belonging to eight sequence types ST350, ST208, ST436, ST437, ST449, ST231, ST502, and ST579. Molecular characterization of the remaining isolates confirmed the presence of one NDM-1-producing E. coli-ST101 clone (five isolates) and one P. mirabilis clone (13 isolates) with VIM-1 and CMY-99. Furthermore, NDM-1 was identified in P. rettgeri and M. morganii and VIM-2 in the P. aeruginosa isolate. The permanent introduction of OXA-23/72 carbapenemase-producing A. baumannii clones into the hospital and the repeated occurrence of one VIM-1-producing P. mirabilis and one NDM-1-producing E. coli-ST101 clone over a period of more than 1 year is of concern and requires intensified investigations.
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