Emergence of blaCTX-M-15, blaTEM-169 and blaPER-1 extended-spectrum β-lactamase genes among different Salmonella enterica serovars from human faecal samples.
BACKGROUND
Broad-spectrum β-lactams are used for empirical therapy of severe infections with non-typhoid Salmonella serotypes; however, activities of these drugs against the strains producing different β-lactamase is not so clear. This study investigated the prevalence of β-lactamase genes among isolates of S. enterica serovars from human faecal samples and determined their diversity in activity against different β-lactams.


METHODS
Antimicrobial resistance of faecal isolates of S. enterica to extended-spectrum cephalosporins was analysed and MIC values were determined for the strains presenting extended-spectrum β-lactamases (ESBLs) phenotypes. The β-lactamase genes were identified by PCR and sequencing. β-lactamase activity of the Salmonella strains exhibiting ESBL phenotype was detected by biological, iodometric, spectrophotometry and nitrocefin assays.


RESULTS
Out of 202 S. enterica isolates, ESBLs phenotype was detected among 3.4% (7/202) of the strains. blaTEM-1 and blaCTX-M-15 were among the frequent β-lactamase genes. Detection of blaTEM-169 in S. enterica serovar Typhimurium and S. enterica serovar Bredeney and blaPER-1 in S. enterica serovar Infantis was a new finding in this experiment. Location of blaCTX-M-15/blaTEM-169/blaPER-1 genes on plasmid was confirmed in a transformation experiment. While crude extracts of the enzymes from each strain showed higher activity against cephalothin and cefotaxime, the lowest activity was detected against ceftazidime. The greatest synergistic activity was seen in a strain of S. enterica that carried blaCTX-M-15 and blaPER-1 genes compared with those presenting blaCTX-M-15/blaTEM-169 or blaCTX-M-15/blaTEM-1 genotypes.


CONCLUSIONS
The results show dissemination of ESBLs encoding genes and their combined activity among different serovars of S. enterica that are a threat for future treatment options.
a Foodborne and Waterborne Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences , Tehran , Iran ;|b Gastroenterology and Liver Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences , Tehran , Iran ;
Mercedeh
M
Tajbakhsh
a Foodborne and Waterborne Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences , Tehran , Iran ;
Mohammad Yaghoobi
MY
Avini
c Department of Physiology and Cellular Biophysics , Columbia University Medical Center , New York , NY , USA ;
Jahan
J
Alikhajeh
a Foodborne and Waterborne Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences , Tehran , Iran ;
Elahe
E
Tajeddin
d Department of Microbiology , Iranian Reference Health Laboratory Research Center, Ministry of Health and Medical Education , Tehran , Iran ;|e Department of Microbiology , Central Laboratory, Milad Hospital , Tehran , Iran.
Mohammad
M
Rahbar
e Department of Microbiology , Central Laboratory, Milad Hospital , Tehran , Iran.
Parisa
P
Eslami
a Foodborne and Waterborne Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences , Tehran , Iran ;|b Gastroenterology and Liver Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences , Tehran , Iran ;
Masoud
M
Alebouyeh
a Foodborne and Waterborne Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences , Tehran , Iran ;|b Gastroenterology and Liver Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences , Tehran , Iran ;
Mohammad Reza
MR
Zali
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D005243:Feces / Q000382:microbiology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D058889:Molecular Typing; D016133:Polymerase Chain Reaction; D012480:Salmonella Infections / Q000382:microbiology*; D019779:Salmonella enterica / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics*
D000900:Anti-Bacterial Agents; D001618:beta-Lactamases
Antimicrobial resistance; non-typhoidal Salmonella; β-lactamase activity