Carbapenemase-producing Gram-negative bacteria in hospital wastewater, wastewater treatment plants and surface waters in a metropolitan area in Germany, 2020.

Carbapenemase-producing bacteria (CPB) such as Klebsiella pneumoniae and Escherichia coli are causing hospital outbreaks worldwide. An important transfer route into the aquatic environment is the urban water cycle. We aimed to determine the presence of CPB in hospital wastewater, wastewater treatment plants (WWTPs) and surface waters in a German metropolitan area and to characterise these bacteria by whole-genome comparisons. During two periods in 2020, 366 samples were collected and cultivated on chromogenic screening media. Bacterial colonies were selected for species identification and PCR-based carbapenemase gene screening. Genomes of all detected CPB were sequenced and analysed for resistance gene content, followed by multilocus sequence typing (MLST) and core genome MLST (cgMLST) for K. pneumoniae and E. coli isolates. Carbapenemase genes were detected in 243 isolates, most of which belonged to genera/species Citrobacter spp. (n = 70), Klebsiella spp. (n = 57), Enterobacter spp. (n = 52) and E. coli (n = 42). Genes encoding KPC-2 carbapenemase were detected in 124 of 243 isolates. K. pneumoniae produced mainly KPC-2 and OXA-232 whereas E. coli harboured various enzymes (KPC-2, VIM-1, OXA-48, NDM-5, KPC-2 + OXA-232, GES-5, GES-5 + VIM-1, IMP-8 + OXA-48). Eight and twelve sequence types (STs) were identified for K. pneumoniae and E. coli, respectively, forming different clusters. The detection of numerous CPB species in hospital wastewater, WWTPs and river water is of concern. Genome data highlight a hospital-specific presence of distinct carbapenemase-producing K. pneumoniae and E. coli strains belonging to "global epidemic clones" in wastewater samples representing local epidemiology. The various detected CPB species including E. coli ST635, which is not known to cause human infections, could serve as reservoirs/vectors for the spread of carbapenemase genes in the environment. Therefore, effective pretreatment of hospital wastewater prior to discharge into the municipal wastewater system may be required, although swimming lakes do not appear to be a relevant risk factor for CPB ingestion and infection.

Potential role of host-derived quorum quenching in modulating bacterial colonization in the moon jellyfish Aurelia aurita.

Multicellular organisms can be regarded as metaorganisms, comprising of a macroscopic host interacting with associated microorganisms. Within this alliance, the host has to ensure attracting beneficial bacteria and defending against pathogens to establish and maintain a healthy homeostasis. Here, we obtained several lines of evidence arguing that Aurelia aurita uses interference with bacterial quorum sensing (QS) - quorum quenching (QQ) - as one host defense mechanism. Three A. aurita-derived proteins interfering with bacterial QS were identified by functionally screening a metagenomic library constructed from medusa-derived mucus. Native expression patterns of these host open reading frames (ORFs) differed in the diverse life stages (associated with different microbiota) pointing to a specific role in establishing the developmental stage-specific microbiota. Highly increased expression of all QQ-ORFs in germ-free animals further indicates their impact on the microbiota. Moreover, incubation of native animals with pathogenic bacteria induced expression of the identified QQ-ORFs arguing for a host defense strategy against confronting bacteria by interference with bacterial QS. In agreement, immobilized recombinant QQ proteins induced restructuring of polyp-associated microbiota through changing abundance and operational taxonomic unit composition. Thus, we hypothesize that additional to the immune system host-derived QQ-activities potentially control bacterial colonization.