Prevalence, Antimicrobial Resistance, and Extended-Spectrum β -Lactamases Characterization of Salmonella Isolates in Apulia, Southern Italy (2001–2005)

The prevalence, antimicrobial susceptibility, and production of extended-spectrum beta-lactamases (ESBLs) of Salmonella collected from several hospitals in Apulia (southern Italy) were evaluated. The most common Salmonella isolates were Salmonella enterica serovar Typhimurium (44.6%), S. enterica serovar Enteritidis (33.4 %), S. enterica serovar Infantis (3.2 %), S. enterica serovar Typhi (1.5%), and S. enterica serovar Bovismorbificans (1.5%). The other serovars accounted for less than 1% each. Our data show a high resistance to ampicillin, tetracycline, and chloramphenicol. The isolates were pansensitive (53.5%), resistant to one antimicrobial agent (10.5%), resistant to two antimicrobial agents (22.1%), resistant to three antimicrobial agents (10.8%), and to four antimicrobial agents (2.7%). Resistance to more than four antibiotics was observed in 0.5% of strains. The presence of ESBL was found in only one strain of S. enterica serovar Bovismorbificans. The CTX-M-1 type-producing strain was identified by isoelectric focusing and molecular analysis. Results were consistent with the presence of a pI 8.6 ESBL active on cefotaxime, ceftazidime, cefepime, and aztreonam. Mating experiments showed that the CTX-M-1 determinant was transferable. To the best of our knowledge, this is the first report of CTX-M-1 type ESBL in Salmonella serovar Bovismorbificans.