Occurrence and multiple antibiotic resistance profiles of non-fermentativeGram-negative microflora in five brands of non-carbonated French bottled spring water

Five brands of French bottled mineral water were analyzed by heterotrophic plate counts (HPC) and for the presence of multiple antibiotic resistant ba cteria. HPC at 22 degrees C were around 10(4) colony forming units ml(-1) o n R2A medium. Enumeration on PCA/10, MH, and especially PCA and King B medi a was less efficient. At 37 degrees C, HPC were two to three orders of magn itude less than at 22 degrees C. Moreover, phenotypic diversity (7 to 15 ph enotypes) was optimal on R2A incubated at 22 degrees C. All isolates were i dentified as non-fermentative Gram-negative rods and 75% were non-identifia ble with the API 20NE system. Stenotrophomonas maltophilia and fluorescent Pseudomonas were isolated on VIA and CFC selective agar media, respectively . Burkholderia cepacia strains were not isolated on BCSA medium. The specie s S. maltophilia was found in 33%, 28%, and 11% of sample from springs A, D , and E, respectively. Independent of brand, isolates from HPC media were l ess efficient to achieve confluent growth in 18 h on MH at 30 or 37 degrees C (0 to 40%) than isolates from selective media (28 to 63%). Seventy perce nt of the total isolates from dominant microflora (1-5 x 10(3) CFU ml(-1) o n HPC media) were resistant against two or four antibiotics. The antibiotic s concerned were principally aztreonam, ampicillin, and nalidixic acid. The remaining dominant bacteria showed a 6-9 multiple antibiotic resistant (MA R) pattern. All isolates were susceptible to newer antimicrobial agents. Ow ing to their low nutrient and temperature requirements, these isolates are unlikely to cause concern to public heath. Fifty percent of strains isolate d from selective media (non-dominant microflora, 4-40 CFU l(-1)) showed a 1 0-18 MAR pattern and 33%, identified as S. maltophilia, a 20-27 MAR pattern . However, minocycline was effective against all isolates. Owing to its low concentration, colonization of human intestine by MAR S. maltophilia is un likely.