Minimum inhibitory concentration of carbapenems and tigecycline against Salmonella spp

1 Department of Microbiology, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi, India 2 New Drug Discovery, Ranbaxy Research Laboratories, Gurgaon, India 3 Department of Microbiology, Majeedia Hospital, Hamdard University, New Delhi, India Correspondence Deepthi Nair deepthinair2{at}gmail.com Received December 31, 2007 Accepted October 31, 2008 Antimicrobial resistance in Salmonella spp. is of grave concern, more so in quinolone-resistant and extended-spectrum β -lactamase (ESBL)-producing isolates that cause complicated infections. The MIC of azithromycin, ciprofloxacin, cefixime, cefepime, ceftriaxone, gatifloxacin, imipenem, levofloxacin, meropenem and ofloxacin (E-test strip) and tigecycline and faropenem (agar dilution) against 210 Salmonella spp. was determined. MIC 90 (defined as the antimicrobial concentration that inhibited growth of 90 % of the strains) of the carbapenems (imipenem and meropenem) for Salmonella Typhi and Salmonella Paratyphi A was 0.064 µg ml –1 . MIC 90 of faropenem was 0.25 µg ml –1 for S . Typhi, S . Paratyphi A and Salmonella Typhimurium. The MIC 90 of azithromycin for all Salmonella spp. ranged from 8 to 16 µg ml –1 . Tigecycline showed an MIC 90 of 2 µg ml –1 for S . Typhi, 1 µg ml –1 for S. Paratyphi A and 4 µg ml –1 for S. Typhimurium. We concluded that tigecycline and the carbapenems are likely to have roles in the final stage of treatment of quinolone-resistant and ESBL-producing multidrug-resistant salmonellae. Abbreviations: CLSI, Clinical and Laboratory Standards Institute; ESBL, extended-spectrum β -lactamase; EUCAST, European committee on antimicrobial susceptibility testing; FDA, Food and Drug Administration; MDR, multidrug-resistant; MIC 50 and MIC 90 , antimicrobial concentration that inhibited growth of 50 and 90 %, respectively, of the strains; NAR, nalidixic acid-resistant.