High prevalence of acquired antimicrobial resistance unrelated to heavy antimicrobial consumption.

In a very remote rural Bolivian community where the use of antimicrobials has been minimal and where exchanges with the exterior are very limited, 67% of subjects were found to be carriers of fecal Escherichia coli with acquired resistance to >/=1 antimicrobial agent(s); the highest rates were observed for tetracycline (64%), ampicillin (58%), trimethoprim-sulfamethoxazole (50%), and chloramphenicol (41%). The most relevant implication of these findings is that, in certain settings, the spread and maintenance of antimicrobial resistance can occur, regardless of whether selective pressure generated by the use of antimicrobials is present.

Multiple CTX-M-type extended-spectrum beta-lactamases in nosocomial isolates of Enterobacteriaceae from a hospital in northern Italy.

Twelve isolates of Enterobacteriaceae (1 of Klebsiella pneumoniae, 8 of Escherichia coli, 1 of Proteus mirabilis, and 2 of Proteus vulgaris) classified as extended-spectrum beta-lactamase (ESBL) producers according to the ESBL screen flow application of the BD-Phoenix automatic system and for which the cefotaxime MICs were higher than those of ceftazidime were collected between January 2001 and July 2002 at the Laboratory of Clinical Microbiology of the San Matteo University Hospital of Pavia (northern Italy). By PCR and sequencing, a CTX-M-type determinant was detected in six isolates, including three of E. coli (carrying bla(CTX-M-1)), two of P. vulgaris (carrying bla(CTX-M-2)), and one of K. pneumoniae (carrying bla(CTX-M-15)). The three CTX-M-1-producing E. coli isolates were from different wards, and genotyping by pulsed-field gel electrophoresis (PFGE) revealed that they were clonally unrelated to each other. The two CTX-M-2-producing P. vulgaris isolates were from the same ward (although isolated several months apart), and PFGE analysis revealed probable clonal relatedness. The bla(CTX-M-1) and bla(CTX-M-2) determinants were transferable to E. coli by conjugation, while conjugative transfer of the bla(CTX-M-15) determinant from K. pneumoniae was not detectable. Present findings indicate that CTX-M enzymes of various types are present also in Italy and underscore that different CTX-M determinants can be found in a single hospital and can show different dissemination patterns. This is also the first report of CTX-M-2 in P. vulgaris.

Novel 3-N-aminoglycoside acetyltransferase gene, aac(3)-Ic, from a Pseudomonas aeruginosa integron.

A novel gene, aac(3)-Ic, encoding an AAC(3)-I aminoglycoside 3-N-acetyltransferase, was identified on a gene cassette inserted into a Pseudomonas aeruginosa integron that also carries a bla(VIM-2) and a cmlA7 gene cassette. The aac(3)-Ic gene product is 59 and 57% identical to AAC(3)-Ia and AAC(3)-Ib, respectively, and confers resistance to gentamicin and sisomicin.

Molecular characterization of extended-spectrum beta-lactamases produced by nosocomial isolates of Enterobacteriaceae from an Italian nationwide survey.

Extended-spectrum beta-lactamases (ESBLs) are widespread in hospital settings worldwide. The present investigation was undertaken to assess the distribution and prevalence of ESBLs belonging to the TEM and SHV families in 448 ESBL-producing clinical isolates of Enterobacteriaceae collected from 10 different Italian hospitals. The natures of TEM and SHV determinants were identified by direct sequencing of PCR-amplified genes. TEM-52 and SHV-12 were the most common variants, and they were found in most hospitals and in several different species. Other less frequent variants included TEM-5, TEM-12, TEM-15, TEM-19, TEM-20, TEM-24, TEM-26, TEM-43, TEM-60, TEM-72, TEM-87, SHV-2a, SHV-5, and SHV-11. Proteus mirabilis was the most common producer of TEM-type ESBLs, while Klebsiella pneumoniae was the most common producer of SHV-type ESBLs. The distribution of TEM- and SHV-type ESBL variants in Enterobacteriaceae from Italian hospitals exhibited notable differences from those from other geographical settings.