The association between antibiotic use in hospitals and residual antibiotic concentrations in hospital effluents: a pilot study.

OBJECTIVE

To analyse the possible association between hospital antibiotic use and residual antibiotic concentrations in wastewater effluents, with the aim of evaluating wastewater surveillance as a potential alternative antimicrobial use monitoring system (AlAUMS).

METHODS

The study was conducted at a Regional Hospital in South Africa and followed an observational, quantitative and correlational design. The hospital use of selected antibiotics was determined using consumption data as a proxy and calculated using the WHO Anatomic Therapeutic Chemical (ATC) and DDD methodology. Selected antibiotics in the hospital effluent were analysed by solid-phase extraction (SPE) and quantified by GC-MS. Spearman's rank correlation coefficient and values were calculated to determine the possible association between antibiotic use and residual antibiotic concentrations as an AlAUMS.

FINDINGS

The highest mean antibiotic use in the hospital was for oral sulfamethoxazole (6.71 DDD/100 bed days), followed by parenteral cefazolin (3.15 DDD/100 bed days). The highest mean antibiotic concentration in the hospital effluent was for sulfamethoxazole (34.57 μg/L) followed by cefazolin (25.32 μg/L). A strong positive correlation was observed for sulfamethoxazole (s = 0.86) and a moderate positive correlation for cefazolin (s = 0.50). However, none were statistically significant.

CONCLUSIONS

The positive correlation displayed between the use of cefazolin and sulfamethoxazole and their concentrations in wastewater indicates a potential association between antibiotic use and residual antibiotic concentrations in hospital settings suggesting that wastewater surveillance is a promising proxy for conventional antibiotic use surveillance. Further studies are necessary to validate these results before wastewater surveillance can be implemented as an AlAUMS.