With Extremely Low MICs, Typhoid Bacilli in Jamaica Susceptible to all available antibiotics

    Going against the global trend toward multi-drug resistance (MDR) in strains of Salmonella enterica serotype Typhi, isolates encountered in Jamaica have been uniformly susceptible not only to all anti-typhoid drugs but also to a number of other antibiotics over the years, according to data presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy in Chicago. 

   Those were the key findings of N. C. Bodonaik, MD, and O. Heslop, PhD, of the University of the West Indies in Kingston, Jamaica. They presented data on susceptibilities to a total of 25 antibiotics against each of the 39 viable isolates encountered in 17 consecutive years (1984 to 2000) at their 534-bed tertiary care teaching hospital. According to Drs. Bodonaik and Heslop, "We have been routinely serotyping all isolates of Salmonella encountered from patients in the hospital and referred to us from other health care Institutions across the country and maintaining them on Dorset Egg medium over the years."

   They subcultured the isolates, tested them for viability, and again identified and serotyped them. The researchers determined MICs by E test, using E. coli ATCC 25922 as control. In addition, the isolates were tested against 21 other available antibiotics using the CLSI disc method. The findings were that the MICs (ug/ml) of 4 front-line anti-typhoid drugs were chloramphenicol MIC range 2-4, MIC50=3 and MIC90=3; ampicillin range 0.125-1, MIC50=0.25 and MIC90=0.5; trimeth/sulpha range 0.023-0.064, MIC50=0.032, and MIC90=0.047; and ceftriaxone range 0.023-0.047, MIC50=0.032 and MIC90=0.047.

   Drs. Bodonaik and Heslop noted that "All isolates were susceptible, MICs were extremely low and fell in a narrow range far below the CLSI susceptible breakpoints of the antibiotics. In addition, the isolates were susceptible by disc method to 21 other antibiotics available in the hospital."