| Abstract | MOLECULAR CHARACTERIZATION OF ANTIMICROBIAL RESISTANCE
IN GRAM-NEGATIVE BACTERIA ISOLATED FROM BOVINE MASTITIS IN
EGYPT
Ashraf M. Ahmed and Tadashi Shimamoto
Department of Bacteriology, Mycology and Immunology, Faculty of Veterinary Medicine, Kafr El-Sheikh University, El-Geish Street, Kafr El-Sheikh
33516, Egypt, and 2Laboratory of Food Microbiology and Hygiene, Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama,
Higashi-Hiroshima-shi, Hiroshima 739-8528, Japan
ABSTRACT
The aim of this study was to characterize the genetic basis of multidrug resistance in Gram-negative bacteria isolated from bovine mastitis cases in Egypt. Multidrug resistance phenotypes were found in 34 of 112 (30.4%) Gram-negative bacterial isolates, which harbored at least one antimicrobial resistance gene. Themost prevalentmultidrug-resistant (MDR) species were Enterobacter cloacae (8 isolates, 7.1%), Klebsiella pneumoniae (7 isolates, 6.3%), Klebsiella oxytoca (7 isolates, 6.3%), Escherichia coli (5 isolates, 4.5%), and Citrobacter freundii (3 isolates, 2.7%). The most commonly observed resistance phenotypeswere against ampicillin (97.0%), streptomycin (94.1%), tetracycline (91.2%), trimethoprim– sulfamethoxazole (88.2%), nalidixic acid (85.3%), and chloramphenicol (76.5%). Class 1 integrons were detected in 28 (25.0%) isolates. The gene cassettes within class 1 integrons included those encoding resistance to trimethoprim (dfrA1, dfrA5, dfrA7, dfrA12, dfrA15, dfrA17, and dfrA25), aminoglycosides (aadA1, aadA2, aadA5, aadA7, aadA12, aadA22, and aac(3)-Id), chloramphenicol (cmlA), erythromycin (ereA2), and rifampicin (arr-3). Class 2 integrons were identified in 6 isolates (5.4%) with three different profiles. Furthermore, the ?-lactamase encoding genes, blaTEM, blaSHV, blaCTX?M, and blaOXA, the plasmid-mediated quinolone resistance genes, qnr and aac(6)-Ib-cr, and the florfenicol resistance gene, floR, were also identified. To the best of our knowledge, the results identified class 2 integrons, qnr and aac(6)-Ib-cr from cases ofmastitis for the first time. This is the first report ofmolecular characterization for antimicrobial resistance in Gram-negative bacteria isolated from bovine mastitis in Africa. |