Comparison of antimicrobial resistance patterns between clinical and sewage isolates in a regional hospital in Taiwan

Aims:  To compare bacterial populations and antimicrobial resistance patterns between clinical and sewage isolates from a regional hospital in northern Taiwan. The dissemination of antibiotic-resistant bacteria from hospital compartments to the hospital sewage treatment plant was examined.
Methods and Results:  A total of 1020 clinical isolates and 435 sewage isolates were collected between July and September 2005. The percentages of Gram-negative bacteria from the clinical and sewage isolates were 87·2% and 91·0%, respectively ( P  =   0·033). Escherichia coli were the leading bacterial isolates in both groups. Antimicrobial susceptibility testing showed a significant difference ( P  <   0·001) in resistance to ampicillin (85·6% vs 94·1%), ampicillin/sulbactam (31·7% vs 55·4%), cefazolin (29·2% vs 71·5%) and cefuroxime (20·7% vs 61·9%) between clinical and sewage coliform isolates, respectively.
Conclusions:  The sewage isolates had higher antimicrobial resistance rates than the clinical isolates from the same hospital.
Significance and Impact of the Study:  The low efficacy of the hospital sewage treatment may contribute to the dissemination of multidrug resistant bacteria from this hospital compartments to the environment. Practices which limit the disposal of antimicrobial agents into the wastewater system may be the possible measure to prevent the selection of multidrug-resistant bacteria from sewage treatment plants.