Bacteriology of the freshwater environment: implications for clinical therapy

Water and animal tissue samples were obtained from sources in Tennessee, California, and Florida. Purified bacterial colonies were isolated and organisms identified. Fifty-eight isolates were recovered. Twenty-seven Gram-negative isolates were identified. Gram-positive organisms were of the coryneform group or Bacillus species. Antibiotic susceptibility testing showed that Aeromonas species were relatively resistant to a wide variety of antimicrobials, which included trimethoprim, cefazolin, and ampicillin. Antibiotics effective against more than 90% of Gram-negative isolates included ciprofloxacin, imipenem, ceftazidime, and trimethoprim-sulfamethoxazole. Freshwater Gram-positive organisms did not display any unexpected susceptibility features. Recommendation for treatment are based on sensitivity in culture and the potentially serious nature of infections caused by Aeromonas species.