Detection of TEM-, SHV- and CTX-M-type beta-lactamase production among clinical isolates of Salmonella species

作者：Elumalai Sathishkumar; Muthu G; Selvam R Esther Mary; Ramesh Srivani^*

来源：Journal of Medical Microbiology, 2014, 63(Pt_7): 962-967.

DOI：10.1099/jmm.0.068486-0

Enteric fever is a major public health problem in developing countries. Due to the problem of resistance to first-line drugs and fluoroquinolone, cephalosporins are currently used for treatment of enteric fever. Cephalosporin resistance in Salmonella spp. is mainly due to production of extended-spectrum beta-lactamases (ESBLs). The majority of ESBLs in Salmonella are derivatives of the TEM and SHV beta-lactamase families. The objectives of this study were to detect antibiotic susceptibility patterns, ESBL production and TEM-, SHV- and CTX-M-encoding genes (bla(TEM), bla(SHV) and bla(CTX-M)) among clinical isolates of Salmonella spp. A total of 134 Salmonella isolates [Salmonella Typhi (n=101), Salmonella Paratyphi A (n=31), Salmonella Paratyphi B (n=1) and Salmonella Typhimurium (n=1)] were included in this study. Multidrug resistance was seen in 5/134 (3.73%) isolates, all of which belonged to serotype S. Typhi. A better susceptibility profile was observed for first-line drugs (ampicillin, chloramphenicol, co-trimoxazole and tetracycline) and cephalosporins (cefotaxime, ceftazidime, ceftriaxone, cefixime and cefepime). However, 131 (97.76%) of the 134 isolates were resistant to nalidixic acid and one (0.75 %) was resistant to ciprofloxacin. TEM-1-type beta-lactamase (bla(TEM-1)) was detected in six (4.47%) of the 134 isolates, which belonged to the serotype S. Typhi. All six TEM-positive isolates were negative for the bla(SHV) gene and none of the isolates was positive for the bla(CTX-M) gene. The presence of the bla(TEM) gene encoding TEM-1 beta-lactamase is believed to confer resistance only to penicillins and early cephalosporins; however, the resistance spectrum of TEM-1 descendants may extend to second-, third- and fourth-generation cephalosporins. The ESBLs derived from TEM-1 differ from their progenitors by as few as 1 aa, and have the ability to hydrolyse third-generation cephalosporins. Therefore, appropriate selection and rotation of antibiotics as well as continuous monitoring of antibiotic susceptibility profiles could help to control the emergence and spread of resistant strains.

• 出版日期2014-7