Unusual antibiotic resistance pattern among blood culture isolates of Salmonella Paratyphi A.

INTRODUCTION: With increasing fluoroquinolone resistance, extended spectrum cephalosporins are recommended for the treatment of invasive Salmonella infections. However, Extended spectrum beta-lactamases (ESBL) producing Salmonella Paratyphi A causing enteric fever is on the rise and constitutes a major therapeutic challenge. Hence, we aimed to assess the incidence of ESBL production, fluoroquinolone resistance in S. Paratyphi A and to compare the fluoroquinolone resistance detection methods. METHODOLOGY: Seventeen blood-culture isolates of S. Paratyphi A were tested for susceptibility to ampicillin, chloramphenicol, co-trimoxazole, streptomycin and tetracycline (ACCuST), fluoroquinolones, azithromycin and ceftriaxone by disk diffusion method. We compared and correlated between disk diffusion of ciprofloxacin and pefloxacin with ciprofloxacin MIC. Combined disk test was employed to determine ESBL production. RESULTS: In this study, 13(76.5%) isolates were nalidixic acid resistant (NAR), 16 (94.1%) were pefloxacin resistant, while 7 (41.2%), 9 (52.9%) exhibited resistance and intermediate susceptibility to ciprofloxacin respectively. The MIC50, MIC90 of ciprofloxacin was 1 µg/mL, 2 µg/mL respectively. Among the NAR, 76.92% were DSC (MIC 0.5-1 µg/mL) and 23.08% had an MIC of 2-4 µg/mL. Of note, 4 isolates with DSC were NAS. Of the 17 S. Paratyphi A isolates, 14 (82.4%) were ESBL producers and 11 (64.7%) isolates were ceftriaxone susceptible. CONCLUSIONS: Multidrug resistant (AmpRChlRSxtR) S. Paratyphi A with combined resistance to fluoroquinolones and ESBL production is a cause of concern. We found S. Paratyphi A isolates with a relatively unusual phenotype: nalidixic acid susceptible but exhibited DSC; pefloxacin susceptible but ciprofloxacin resistant. Of note one multidrug resistant (AmpRChlRSxtR) isolate, an ESBL producer exhibited resistance to azithromycin, cephalosporins and fluoroquinolones but was susceptible to carbapenems and streptomycin.

Extended Spectrum Beta-lactamase producing Salmonella Lindenberg gastroenteritis.

INTRODUCTION: Increasing antimicrobial resistance among non-typhoidal Salmonella (NTS) is a major public health issue especially in developing countries and is partly due to the use of antimicrobials in animal feeds as growth promoters. NTS are often associated with self-limiting acute gastroenteritis (AGE). Nevertheless, fluoroquinolones and third-generation cephalosporins are currently used in the treatment of severe diarrhoeal infections. METHODOLOGY: We report the case of a 30-year-old male who presented with clinical symptoms of moderate gastroenteritis. Stool culture and antibiotic susceptibility was performed as per standard microbiological methods. Molecular detection of bla genes was carried out by PCR. RESULTS: The isolate was confirmed as S. Lindenberg by serotyping. The isolate exhibited dual resistance to fluoroquinolone and third generation cephalosporins. The isolate was an ESBL producer and harboured blaSHV. Based on the antibiotic susceptibility pattern, the patient was successfully treated with ceftriaxone-tazobactam. CONCLUSION: Presently, there are no Indian reports on the blaSHV positive ESBL producing S. Lindenberg gastroenteritis. We report on the successful management of the first case of acute gastroenteritis caused by S. Lindenberg that exhibited dual resistance to fluoroquinolone and third generation cephalosporins. Continued surveillance of the antibiotic resistance pattern of the Non-typhoidal Salmonella serovars circulating in the geographical region is warranted.