Effects of tourist flows on antibiotic resistance in wastewater of a Greek island

Aim Antibiotic resistance in wastewaters reflects the clinical resistome. This study aimed at investigating whether changes in the population size and composition in the popular tourist destination of Zakynthos island are associated with differentiation in the antibiotic resistance of environmental micro-organisms isolated from wastewater. Methods and Results The resistance profiles of four species (Escherichia coli,Staphylococcussp.,Pseudomonassp. andEnterococcussp.) were studied in 124 raw and treated municipal wastewaters from November 2015 to August 2016. Isolates were tested against their susceptibility to several antibiotics of different antimicrobial categories. Data concerning the alteration in the population size and composition, due to the tourist mobility, were collected and logistic regression models were used to examine the relationships between antimicrobial resistance and population changes. The decrease in resistance ofE. colito amoxicillin-clavulanate, of enterococci to norfloxacin and ampicillin, and of pseudomonads to almost all antibiotics tested was associated with population increase due to tourist flows. In contrast, the presence of tourists was linked to an increase in quinupristin-dalfopristin resistant enterococci. Resistance of staphylococci did not change during the tourist period. Conclusion Changes in population composition in touristic areas are reflected in antibiotic resistance of environmental bacteria in wastewater. Significance and Impact of the Study In touristic areas, where people carrying different resistomes are merged, medication should be adapted accordingly.

Automated summary

The study aimed to investigate whether changes in the population size and composition in the popular tourist destination of Zakynthos island are associated with differentiation in the antibiotic resistance of environmental micro-organisms isolated from wastewater. The results showed that an increase in population due to tourist flows was associated with a decrease in antibiotic resistance of E. coli and an increase in quinupristin-dalfopristin resistant enterococci.