Characterization of enterococci populations collected from a subsurface flow constructed wetland

Draft Genome Sequence of Enterococcus dispar CoE-457-22, Isolated from Traditionally Produced Montenegrin Dry Sausage

Enterococcus dispar was isolated for the first time from synovial fluid and stool cultures and described as a new species in 1991. Here, we report the genome of E. dispar CoE-457-22, which was obtained from traditionally produced Montenegrin dry sausage (sudzuk).

Prevalence, antibiotic resistance and virulence of Enterococcus spp. from wastewater treatment plant effluent and receiving waters in South Africa

Poorly operating wastewater treatment plants (WWTPs) result in faecal pollution of receiving waters, posing a health risk to humans and animals. The aim of this study was to determine the antimicrobial resistance patterns and presence of virulent genes in Enterococcus spp. isolated from three WWTPs' final effluent and receiving waters in the North West Province, South Africa. Sixty-three Enterococcus spp. were identified and their antimicrobial susceptibility, as well as the presence of five virulence genes, determined. The antibiotic inhibition zone diameter data were subject to cluster analysis. Sixty-eight percent of the screened Enterococcus spp. were resistant to three or more antibiotics and harboured plasmids. Five virulence genes were detected and six multi-virulence profiles observed. Cluster analysis indicated groupings of isolates from all three effluent points downstream together, and between plants 1 and 2 together. The findings of this study have demonstrated that Enterococcus spp. harbouring virulence factors and plasmids that mediate multiple antibiotic resistance are present in effluent and receiving water systems that support various social needs. This is a cause for concern and it is recommended that Enterococcus be used as an additional faecal indicator when microbiological quality of water is assessed.

Occurrence, diversity, and persistence of antibiotic resistant enterococci in full-scale constructed wetlands treating urban wastewater in Sicily

Enterococci isolated from different sites of an urban wastewater treatment plant (consisting of three horizontal subsurface flow constructed wetlands) were investigated. One-hundred-thirty isolates were identified at species level and tested for resistance to eleven antibiotics, by microdilution method, and their clonal relatedness was established by SmaI-PFGE analysis. Results highlighted the persistence of enterococcal population in all effluents and the dominance of E. faecium species. A high incidence of antibiotic resistance against erythromycin, chloramphenicol, rifampicin and ampicillin was observed, with 120 strains (93%) showing a multi-drug-resistance. Numerous pulso-types with a unique pattern were detected indicating a high diversity within enterococcal population. The recurrence of some pulso-types in different effluents was disclosed and, within the same pulso-types, different resistance patterns were observed. Comparing the MIC values of strains from inlet and outlet, different trends were observed, highlighting a certain variability among constructed wetlands in affecting the antibiotic resistance among enterococcal population.

Continuous Flow-Constructed Wetlands for the Treatment of Swine Waste Water

The microbiological quality of treated waste water is always a concern when waste water is disposed to the environment. However, when treated appropriately, such water can serve many purposes to the general population. Therefore, the treatment and removal of contaminants from swine waste water by continuous flow-constructed wetlands involves complex biological, physical, and chemical processes that may produce better quality water with reduced levels of contaminants. Swine waste contains E. coli populations and other bacterial contaminants originating from swine houses through constructed wetlands, but little is known about E. coli population in swine waste water. To assess the impacts of seasonal variations and the effect of the wetland layout/operations on water quality, E. coli isolates were compared for genetic diversity using repetitive extragenic palindromic polymerase chain reaction (REP-PCR). None of the isolates was confirmed as Shiga toxin producing E. coli O157:H7 (STEC); however, other pathotypes, such as enterotoxigenic E. coli (ETEC) were identified. Using a 90% similarity index from REP-PCR, 69 genotypes out of 421 E. coli isolates were found. Our data showed that the E. coli population was significantly (p = 0.036) higher in November than in March and August in most of the wetland cells. Furthermore, there was a significant (p = 0.001) reduction in E. coli populations from wetland influent to the final effluent. Therefore, the use of continuous flow-constructed wetlands may be a good treatment approach for reducing contaminants from different waste water sources.

Environmental Growth of Enterococci and Escherichia coli in Feedlot Catch Basins and a Constructed Wetland in the Absence of Fecal Input

Population structures of fecal indicator bacteria (FIB) isolated from catch basins, a constructed wetland, and feces from a beef cattle feedlot were compared over a two-year period. Enterococcus hirae accounted for 92% of the fecal isolates, whereas secondary environments were characterized by greater relative abundance of environmentally adapted species including Enterococcus casseliflavus. While enterococci densities in the catch basins and wetland were similar under wet and drought conditions, E. hirae predominated during rainy periods, while E. casseliflavus predominated during drought conditions. Environmentally adapted species accounted for almost half of the erythromycin resistant enterococci isolated from the wetland. Densities of Escherichia coli were also comparable during wet versus drought conditions, and the relative abundance of strains from environmentally adapted clades was greater in secondary environments compared to feces. Unlike enterococci, fewer environmentally adapted E. coli strains were isolated on selective media containing ceftriaxone from the wetland compared to feces, suggesting resistance to this antibiotic may not be well maintained in the absence of selective pressure. Overall, these findings suggest that secondary environments select for environmentally adapted FIB. While these species and clades tend to be of limited clinical relevance, they could potentially serve as reservoirs of antimicrobial resistance.

Tyrosine decarboxylase activity of Enterococcus mundtii: new insights into phenotypic and genetic aspects

Few information is available about the tyraminogenic potential of the species Enterococcus mundtii. In this study, two plant‐derived strains of E. mundtii were selected and investigated to better understand the phenotypic behaviour and the genetic mechanisms involved in tyramine accumulation. Both the strains accumulated tyramine from the beginning of exponential phase of growth, independently on the addition of tyrosine to the medium. The strains accumulated also 2‐phenylethylamine, although with lower efficiency and in greater extent when tyrosine was not added. Accordingly, the tyrosine decarboxylase (tyrDC) gene expression level increased during the exponential phase with tyrosine added, while it remained constant and high without precursor. The genetic organization as well as sequence identity levels of tyrDC and tyrosine permease (tyrP) genes indicated a correlation with those of phylogenetically closer enterococcal species, such as E. faecium, E. hirae and E. durans; however, the gene Na+/H+ antiporter (nhaC) that usually follow tyrP is missing. In addition, BLAST analysis revealed the presence of additional genes encoding for decarboxylase and permease in the genome of several E. mundtii strains. It is speculated the occurrence of a duplication event and the acquisition of different specificity for these enzymes that deserves further investigations.

Potential pathogens, antimicrobial patterns and genotypic diversity of Escherichia coli isolates in constructed wetlands treating swine wastewater

Escherichia coli populations originating from swine houses through constructed wetlands were analyzed for potential pathogens, antimicrobial susceptibility patterns, and genotypic diversity. Escherichia coli isolates (n = 493) were screened for the presence of the following virulence genes: stx1, stx2 and eae (Shiga toxin-producing E. coli [STEC]), heat-labile enterotoxin (LT) genes and heat stable toxin STa and STb (enterotoxigenic E. coli (ETEC), cytotoxin necrotizing factors 1 and 2 (cnf1 and cnf2 [necrotoxigenic E. coli- NTEC]), as well as O and H antigens, and the presence of the antibiotic resistance genes blaTEM, blaSHV, blaCMY-2, tet A, tet B, tet C, mph(A), aadA, StrA/B, sul1, sul2 and sul3. The commensal strains were further screened for 16 antimicrobials and characterized by BOX AIR-1 PCR for unique genotypes. The highest antibiotic resistance prevalence was for tetracycline, followed by erythromycin, ampicillin, streptomycin, sulfisoxazole and kanamycin. Our data showed that most of the isolates had high distribution of single or multidrug-resistant (MDR) genotypes. Therefore, the occurrence of MDR E. coli in the wetland is a matter of great concern due to possible transfer of resistance genes from nonpathogenic to pathogenic strains or vice versa in the environment.

Comparison of Enterococcus faecium and Enterococcus faecalis Strains isolated from water and clinical samples: antimicrobial susceptibility and genetic relationships

Enterococci are part of the normal intestinal flora in a large number of mammals, and these microbes are currently used as indicators of fecal contamination in water and food for human consumption. These organisms are considered one of the primary causes of nosocomial and environmental infections due to their ability to survive in the environment and to their intrinsic resistance to antimicrobials. The aims of this study were to determine the biochemical patterns and antimicrobial susceptibilities of Enterococcus faecalis and E. faecium isolates from clinical samples and from water (groundwater, water from the Xochimilco wetland, and treated water from the Mexico City Metropolitan Area) and to determine the genetic relationships among these isolates. A total of 121 enterococcus strains were studied; 31 and 90 strains were isolated from clinical samples and water (groundwater, water from the Xochimilco wetland, and water for agricultural irrigation), respectively. Identification to the species level was performed using a multiplex PCR assay, and antimicrobial profiles were obtained using a commercial kit. Twenty-eight strains were analyzed by pulsed-field gel electrophoresis (PFGE). E. faecium strains isolated from water showed an atypical biochemical pattern. The clinical isolates showed higher resistance to antibiotics than those from water. Both the enterococci isolated from humans, and those isolated from water showed high genetic diversity according to the PFGE analysis, although some strains seemed to be closely related. In conclusion, enterococci isolated from humans and water are genetically different. However, water represents a potential route of transmission to the community and a source of antimicrobial resistance genes that may be readily transmitted to other, different bacterial species.