Multiple antibiotic resistances of Enterococcus isolates from raw or sand-filtered sewage

Investigating antimicrobial resistance genes in probiotic products for companion animals

Introduction

One of the greatest challenges of our time is antimicrobial resistance, which could become the leading cause of death globally within a few decades. In the context of One Health, it is in the common interest to mitigate the global spread of antimicrobial resistance by seeking alternative solutions, alongside appropriate drug selection and responsible use. Probiotics offer a potential avenue to reduce antibiotic usage; however, there is a scarcity of research that examines commercial products in terms of carrying antimicrobial resistance genes (ARGs) involved in resistance development through microbial vectors.

Methods

Our study investigated 10 commercially available probiotic products for cats and dogs. Initially, we conducted phenotypic testing through determination of minimum inhibitory concentration (MIC) for antibiotics important in animal and public health. Subsequently, we performed next-generation sequencing (NGS) of the products to elucidate the genetic background behind the decrease in phenotypic sensitivity.

Results

In total, 19 types of ARGs were identified, with 57.9% being found on plasmids, and in two cases, carriage as mobile genetic elements were found. One of the genes identified was the APH(3')-Ia gene, capable of inactivating aminoglycoside antibiotics through phosphotransferase enzyme production regulation, while the other was the tetS gene, capable of conferring reduced sensitivity to tetracycline antibiotics through target protection.

Discussion

Our findings underscore the importance of approaching antimicrobial resistance investigations from a broader perspective. We suggest that further studies in this area are justified and raise questions regarding the need to extend legally required studies on probiotic products from their use in economic livestock to their use in companion animals.

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.

Determination of Vancomycin Resistant Enterococcus faecium Diversity in Tehran Sewage Using Plasmid Profile, Biochemical Fingerprinting and Antibiotic Resistance

Background:

Sewage treatment plants are considered to be the hotspots for antibiotic resistance transfer among bacterial species. Many fecal bacteria including Enterococci circulate and are exposed to antibiotic residues in this environment. Being as one of the most common cause of nosocomial infections, special concerns have risen worldwide about the rate and characteristics of Enterococci (especially, isolates with high resistance against glycopeptides) which are available in raw sewages.

Objectives:

Study on the vancomycin Resistant E. faecium diversity in Tehran sewage by plasmid profile, biochemical fingerprinting and antibiotic resistance

Materials and Methods:

Forty isolates recovered from an urban sewage treatment plant were studied during 2009- 2010. The antibiotic resistance of isolates against 7 antibiotics was examined by disk diffusion method. Extraction of plasmid DNA was performed and identification of van genotype (vanA and vanB) was done by PCR. Biochemical fingerprinting was done by the use of Phene-Plate system (PhP).

Results:

All isolates were found to be resistant to erythromycin, ampicillin and ciprofloxacin. The PCR analyses showed that all E. faecium isolates harbored vanA gene and 5 (13%) isolates harbored vanA and vanB concomitantly. By plasmid profiling the VRE isolates differentiated into 11 types. PhP showed that VRE isolates were grouped into 23 biochemical types.

Conclusions:

The combination of plasmid profiling and PhP techniques revealed the presence of diverse population of VRE in sewage treatment plant in Tehran. Furthermore, the results showed that the PhP technique is a reliable method in determining the VRE clonal diversity.

Frequency of virulence genes and antibiotic resistances inEnterococcusspp. isolates from wastewater and feces of domesticated mammals and birds, and wildlife

Enterococci are gastrointestinal tract residents and also an important cause of nosocomial infections. To understand which species, virulence determinants, and antibiotic resistances are prevalent in enterococci shed by various hosts groups, a total of 1460 strains isolated from 144 fecal samples obtained from wastewater, domesticated mammals and birds, and wildlife were characterized. Identification of isolates to the species level showed that Enterococcus faecalis was dominant in domesticated mammals and birds and wildlife feces, whereas Enterococcus faecium was dominant among wastewater isolates, and that no single Enterococcus species could be associated with a specific host group. The frequency of 12 virulence determinants was evaluated among isolates, but no single virulence determinant could be associated with a specific host group. Resistance to 12 antibiotics was evaluated among isolates, and it was shown that the highest frequency of resistance at breakpoint concentration was found in domesticated mammals and birds (P ≤ 0.05 for 4 antibiotics). Our results suggests that (1) species identification and virulence typing of Enterococcus spp. isolates are not useful for the identification of the host groups responsible for fecal contamination of water by microbial source tracking and that (2) antibiotic use for clinical, veterinary, or animal husbandry practices is promoting resistance.

Distribution of aerobic motile and non-motile bacteria within the capillary fringe of silica sand

Retention of bacterial cells as "particles" by silica sand during formation of a capillary fringe (CF) and the influence of motility was examined with motile Pseudomonas putida and non-motile Corynebacterium glutamicum suspensions in the absence of nutrients. The fractional retention of C. glutamicum cells at all regions of the CF was higher than for P. putida cells, most probably due to the motility of P. putida. Only about 5% of P. putida cells and almost no C. glutamicum cells reached the upper end of a CF of 10 cm height. With cell suspensions of P. putida and C. glutamicum in nutrient broth the development of a CF in silica sand fractions of 355-710 microm and 710-1000 microm respectively, was finished after about 6 h. Growth of cells proceeded for about 6 days. P. putida formed a biofilm on silica grains, whereas no attachment of C. glutamicum on silica sand occurred. Relative cell densities of C. glutamicum on the bottom and in the upper regions of the CF were always lower than those of P. putida and were also lower than those reached in suspended cultures with the same medium. In coarse sand the motile P. putida cells reached significantly higher cell densities in upper CF regions than in fine sand. Growth of C. glutamicum in the CF apparently was slower and a higher proportion of the energy was required for maintenance. Whereas cell densities of P. putida, in CFs of both sand fractions, varied less than one order of magnitude, those of C. glutamicum varied in a wider range from the basis to the top of the CF. Analyses of the esterase activity of P. putida and C. glutamicum with fluorescein diacetate (FDA) revealed that the cells in higher CF regions were significantly more active than those at the bottom of the CF. Furthermore, a significant correlation (r = 0.66, p < 0.01) between cells ml(-1) and the FDA conversion to fluorescein was found.

Solid phase microextraction of macrolide, trimethoprim, and sulfonamide antibiotics in wastewaters

In this work, we optimize a solid phase microextraction (SPME) method for the simultaneous collection of antibiotics (sulfonamides, macrolides, and trimethoprim) present in wastewaters. The performance of the SPME method is compared to a solid phase extraction (SPE) method. Analytes in both cases were quantified by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS-MS) with electrospray ionization. The advantages offered by SPME in this application are: decreased sample volume requirements, ease of sample processing and extraction, decreased cost, and most importantly, elimination of electrospray matrix effects. Despite having higher limits of quantification (16-1380 ng/L in influent and 35-260 ng/L in effluent), nearly all of the compounds found to be present in Edmonton Gold Bar wastewater by SPE were measurable by SPME (i.e., sulfamethoxazole, trimethoprim, erythromycin, and clarithromycin), with values similar to those obtained using the former method. Limits of quantification for the SPE method for the measured compounds were 4.7-15 ng/L and 0.86-6.1 ng/L for influent and effluent, respectively.