Abstract
Bacterial resistance to carbapenems is an emerging problem of this century. A carbapenem-resistant bacterial population (CRBP) grown at 42°C was monitored in the influent and effluent of a secondary municipal wastewater treatment plant over 10 months. The municipal wastewater consisted of domestic, industrial, hospital and storm wastewaters. Median numbers of CRBP in influent and effluent water were 3.5 and 1.3 log CFU/mL, with its prevalence among total heterotrophic bacteria at 47% and 26%, respectively. Correlation of CRBP with physico-chemical and other bacteriological parameters of wastewater was estimated. Higher numbers of CRBP in influent and effluent were found in cases of nutrient-rich wastewater with higher concentrations of total heterotrophic bacteria and intestinal enterococci. Reduction of CRBP in the wastewater treatment process of 54% was comparable to the reduction of intestinal enterococci. Despite the significant elimination of CRBP in the secondary type of wastewater treatment plant, substantial numbers of CRBP are released through the effluent into the natural receiving waters. Since the CRBP grown at 42°C was not found in natural water samples beyond the vicinity of hospitals, these bacteria may be used as an indicator of hospital wastewaters. Keywords: environmental bacteria, carbapenem-resistant bacteria, public health, wastewater
Highlights
Carbapenems are potent β-lactam antibiotics including, at the present time, 7 antibiotics for the treatment of serious infections caused by multi-drug resistant bacteria in hospital settings
The applied method surely allowed the isolation of a narrower range of carbapenem-resistant bacterial populations (CRBP), but eliminated the enumeration of carbapenem-resistant bacteria which are autochthonous in water
CRBP grown at 42°C were found in the influent and effluent water of the secondary type of municipal wastewater treatment plant receiving untreated hospital wastewater
Summary
Carbapenems are potent β-lactam antibiotics including, at the present time, 7 antibiotics for the treatment of serious infections caused by multi-drug resistant bacteria in hospital settings. They have a broad antimicrobial spectrum action on selected Gram-positive and Gram-negative bacteria by acting on penicillin-binding proteins, inhibiting cell wall synthesis (EFSA Panel on Biological Hazards, 2013; Zavascki et al, 2013; Meletis, 2016). Carbapenem resistance in Gram-negative bacteria, which is almost always associated with resistance to several other classes of antibiotics, can be a result of: production of carbapenemases, expression of efflux pumps, porin loss, and alteration in penicillin-binding proteins. Different species of carbapenem-resistant bacteria were isolated from drinking water in New Delhi (Walsh et al 2011; Tanner et al, 2015)
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