Abstract
BackgroundAquatic matrices impacted by sewage may shelter carbapenem-resistant (CR) Gram-negative bacilli (GNB) harboring resistance genes of public health concern. In this study, sewage treatment plants (STPs) servicing well-defined catchment areas were surveyed for the presence of CR-GNB bearing carbapenemase genes (blaKPC or blaNDM).ResultsA total of 325 CR-GNB were recovered from raw (RS) and treated (TS) sewage samples as well as from water body spots upstream (UW) and downstream (DW) from STPs. Klebsiella-Enterobacter (KE) group amounted to 116 isolates (35.7%). CR-KE isolates were recovered from TS, DW (35.7%) and RS samples (44.2%) (p = 0.001); but not from UW samples. KE isolates represented 65.8% of all blaKPC or blaNDM positive strains. The frequency of blaKPC-or-NDM strains was positively associated with the occurrence of district hospitals located near STPs, as well as with the number of hospitalizations and of sewer connections serviced by the STPs. blaKPC-or-NDM strains were recovered from ST samples in 7 out of 14 STPs, including four tertiary-level STPs; and from 6 out of 13 DW spots whose RS samples also had blaKPC-or-NDM strains.ConclusionsClinically relevant GNB bearing blaKPC-or-NDM resist sewage treatments and spread into environmental aquatic matrices mainly from STPs impacted by hospital activities.
Highlights
Aquatic matrices impacted by sewage may shelter carbapenem-resistant (CR) Gram-negative bacilli (GNB) harboring resistance genes of public health concern
This study aimed to characterize the spread of blaKPC-or-NDM-positive GBN strains by way of Sewage Treatment Plant (STP), taking into account the profile of economic activity in areas serviced by STPs, the burden on the STPs imposed by hospital services, and the level of sewage treatment achieved by STPs
Isolates of P. putida group were recovered (p = 0.588) from raw sewage (RS), Treated Sewage (TS) and DW samples [respectively 27.4% (36/131), 33.6% (31/92) and 32.1% (27/84)]; they were recovered at a higher frequency (p = 0.015) from Upstream Water (UW) samples [66.6% (12/18)]
Summary
Aquatic matrices impacted by sewage may shelter carbapenem-resistant (CR) Gram-negative bacilli (GNB) harboring resistance genes of public health concern. Sewage treatment plants (STPs) servicing well-defined catchment areas were surveyed for the presence of CR-GNB bearing carbapenemase genes (blaKPC or blaNDM). Concerning Brazil, strains harboring blaKPC or blaNDM (blaKPC-or-NDM) emerged and were firstly detected in nosocomial environments [7,8,9]. BlaKPC-or-NDM isolates of GNB have been recovered from hospital effluents worldwide [12,13,14,15,16], including Brazil [17, 18]. In the United States, CR isolates were recovered from treated effluent in 42% of sewage treatment plants (STPs) using chlorination process, and in 12% of STPs using ultraviolet radiation [21]. STPs are selective spots and reservoirs of MDR bacteria which contribute to spreading resistant strains in the environment [18, 20, 21]
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