Development of a PCR assay for rapid detection of enterococci

Identification of Enterococcus spp. by MALDI-TOF mass spectrometry isolated from clinical mastitis and bulk tank milk samples

BACKGROUND

Throughout a three-year study period, 1,577 bovine clinical mastitis samples and 302 bulk tank samples were analyzed from ten Brazilian dairy herds. Enterococcus spp. was isolated and identified in 93 (5.9%) clinical mastitis samples. In addition, 258 Enterococcus spp. were isolated from the bulk tank samples of the same herds. The identification of Enterococcus spp. isolated from bulk tanks and milk samples of clinical mastitis were accomplished by phenotypic characteristics and confirmed by MALDI-TOF Mass Spectrometry (MS). Fisher test was performed to verify the difference between bulk tanks and mastitis samples.

RESULTS

The following species were identified from clinical mastitis: E. saccharolyticus (62.4%), E. faecalis (19.4%), E. faecium (15.1%), E. hirae (1.1%), E. mundtii (1.1%), E. durans (1.1%). Furthermore, from 258 bulk tank milk samples, eight enterococci species were isolated: E. faecalis (67.8%), E. hirae (15.1%), E. faecium (4.6%), E. saccharolyticus (4.6%), E. mundtii (3.1%), E. caseliflavus ( 2.7%), E. durans (1.2%), E. galinarum (0.8%).

CONCLUSIONS

The difference in species predominance in bulk tank samples (67.8% of E. faecalis) and clinical mastitis (62.4% of E. saccharolyticus) was unexpected and caught our attention. Although Enterococcus spp. are traditionally classified as an environmental mastitis agent, in the present study, E. saccharolyticus behaved as a contagious agent of mastitis, which consequently changed the control patterns to be implemented.

Occurrence of Enterococci in the Process of Artisanal Cheesemaking and Their Antimicrobial Resistance

Enterococci are a group of microorganisms that have a controversial position from some scientific points of view. The species of the greatest clinical importance are E. faecalis and E. faecium, which are common agents of nosocomial infections. However, enterococci also have important applications in the dairy industry, as they are used as non-starter lactic acid bacteria (NSLAB) in a variety of cheeses, especially artisanal cheeses. The aim of this study was to determine the presence of representatives from the Enterococcus genus using PCR and MALDI-TOF MS methods on samples of raw milk, processing environment swabs, and cheese from four different artisanal dairy plants in Slovakia. Among the 136 isolates of enterococci, 9 species of genus Enterococci (E. faecalis, E. faecium, E. durans, E. devriesi, E. hirae, E. italicus, E. casseliflavus, E. malodoratus, and E. gallinarum) were identified and were tested for their antimicrobial resistance (AMR) to 8 antibiotics (amoxicillin, penicillin, ampicillin, erythromycin, levofloxacin, vancomycin, rifampicin, and tetracycline); most of them were resistant to rifampicin (35.3%), ampicillin (22.8%), and tetracycline (19.9%). A PCR analysis of vanA (4.41%) and tetM (14.71%) revealed that antimicrobial resistance genes were present in not only phenotypic resistant isolates of enterococci but also susceptible isolates. The investigation of antimicrobial resistance in enterococci during the cheesemaking process can be a source of valuable information for public health in the concept of "One Health".

Metagenomic insights into isolable bacterial communities and antimicrobial resistance in airborne dust from pig farms

This study aims to investigate bacterial communities and antimicrobial resistance (AMR) in airborne dust from pig farms. Airborne dust, pig feces and feed were collected from nine pig farms in Thailand. Airborne dust samples were collected from upwind and downwind (25 meters from pig house), and inside (in the middle of the pig house) of the selected pig house. Pig feces and feed samples were individually collected from the pen floor and feed trough from the same pig house where airborne dust was collected. A direct total bacteria count on each sampling plate was conducted and averaged. The ESKAPE pathogens together with Escherichia coli, Salmonella, and Streptococcus were examined. A total of 163 bacterial isolates were collected and tested for MICs. Pooled bacteria from the inside airborne dust samples were analyzed using Metagenomic Sequencing. The highest bacterial concentration (1.9-11.2 × 103 CFU/m3) was found inside pig houses. Staphylococcus (n = 37) and Enterococcus (n = 36) were most frequent bacterial species. Salmonella (n = 3) were exclusively isolated from feed and feces. Target bacteria showed a variety of resistance phenotypes, and the same bacterial species with the same resistance phenotype were found in airborne dust, feed and fecal from each farm. Metagenomic Sequencing analysis revealed 1,652 bacterial species across all pig farms, of which the predominant bacterial phylum was Bacillota. One hundred fifty-nine AMR genes of 12 different antibiotic classes were identified, with aminoglycoside resistance genes (24%) being the most prevalent. A total of 251 different plasmids were discovered, and the same plasmid was detected in multiple farms. In conclusion, the phenotypic and metagenomic results demonstrated that airborne dust from pig farms contained a diverse array of bacterial species and genes encoding resistance to a range of clinically important antimicrobial agents, indicating the significant role in the spread of AMR bacterial pathogens with potential hazards to human health. Policy measurements to address AMR in airborne dust from livestock farms are mandatory.

Powder diet exacerbates oropharyngeal candidiasis in a mouse model

This study reports on the influence of a powder diet in a mouse model of oropharyngeal candidiasis (OPC), a significant health concern caused primarily by Candida albicans. Despite identical nutritional composition, we found that a powdered diet significantly increased Candida burdens and oral lesions, and aggravated weight loss compared to a standard pelleted diet. High fungal burdens and severe oral lesions were accomplished within 48 hours after infection with only one dose of cortisone. Moreover, mice on a powder diet recovered a week after infection. Using a powder diet, we thus modified the cortisone OPC murine model in a way that simplifies the infection process, enhances reproducibility, and facilitates studies investigating both pathogenesis and recovery processes. Our findings also underscore the pivotal role of the physical form of the diet in the progression and severity of oral Candida infection in this model. Future research should investigate this relationship further to broaden our understanding of the underlying mechanisms, potentially leading to novel prevention strategies and improved disease management.IMPORTANCEOropharyngeal candidiasis (OPC) is a multifactorial disease and a significant health concern. We found that the physical form of the diet plays a critical role in the severity and progression of OPC. We developed a modified cortisone OPC murine model that facilitates studies investigating pathogenesis and recovery processes.

Antimicrobial resistance patterns, virulence genes, and biofilm formation in enterococci strains collected from different sources

BACKGROUND

Currently, antibiotic-resistant strains of Enterococcus are considered to be one of the critical health challenges globally. This study aimed to investigate the antibiotic susceptibility pattern, biofilm formation capacity, and virulence genes of enterococci isolated from different sources.

METHODS

In this cross-sectional study, environmental and fecal samples were collected from the hospital environment, volunteers, and hospital staff from October 2018 to August 2019. The isolates were identified by morphological and biochemical tests (gram staining, catalase, bile resistance, esculin hydrolysis, carbohydrate fermentation, growth in 6.5% NaCl, Pyrrolidonyl arylamidase, arginine dehydrolase), and PCR for ddl gene. An antimicrobial susceptibility test was performed by the standard disk agar diffusion method according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Quantitative microplate assays were used to assess biofilm production. The bacterial DNAs were extracted by alkaline lysis method and polymerase chain reaction technique was used detect the esp, ace, and efaA virulence genes.

RESULTS

Out of 145 isolates, 84 (57.9%) were identified as E. faecalis and 61 (42.1%) as E. faecium. Resistance to kanamycin and quinupristin-dalfopristin was 82.1% (69/84) and 85.7% (72/84), respectively, in E. faecalis isolates. Out of 61 E. faecalis isolates, 38 (62.4%) were resistant to kanamycin. Among the E. faecalis isolates, esp was the most dominant virulence gene (73.80%), followed by efaA, and ace, which were detected in 60.71%, and 30.95% isolates, respectively. In total, 68.27% of the strains were biofilm producers. Further, esp and efaA genes were more frequently found among E. faecalis strains with moderate and strong biofilm biomass.

CONCLUSIONS

According to the findings of our study, enterococci strains isolated from different samples possess distinctive patterns of virulence genes. The esp, ace, and efaA genes were more prevalent among E. faecalis than E. faecium. Besides, the high level antibiotic resistance of normal flora and environmental enterococci strains is alarming the researchers.

Microbiological Quality and Antimicrobial Resistance of Commercial Probiotic Products for Food-Producing Animals

Probiotics have been popularly used in livestock production as an alternative to antibiotics. This study aimed to investigate the microbiological quality and phenotypic and genotypic antimicrobial resistance of bacteria in probiotic products sold for food animals. A total of 45 probiotic products were examined for the number of viable cells, species, and antimicrobial susceptibility; the contamination of Escherichia coli and Salmonella; and the presence of 112 genes encoding resistance to clinically important antimicrobials and transferability of AMR determinants. The results showed that 29 of 45 products (64.4%) were incorrectly labeled in either number of viable cells or bacterial species. None of the tested products were contaminated with E. coli and Salmonella. A total of 33 out of 64 bacterial isolates (51.6%) exhibited resistance to at least one antimicrobial agent. Of the 45 products tested, 16 (35.5%) carried AMR genes. Almost all AMR genes detected in probiotic products were not correlated to the AMR phenotype of probiotic strains formulated in the products. Three streptomycin-resistant Lactobacillus isolates could horizontally transfer their AMR determinants. The findings demonstrated that the probiotic products could serve as reservoirs for the spread of AMR genes and may not yield benefits to animals as claimed. The need for the adequate quality control of probiotic products is highlighted.

A prebiotic diet modulates the oral microbiome composition and results in the attenuation of oropharyngeal candidiasis in mice

Oral bacteria can influence the ability of Candida albicans to cause oropharyngeal candidiasis (OPC). We recently reported that a Lactobacillus johnsonii-enriched oral microbiota reduced C. albicans virulence in an immunosuppressed OPC mouse model. As a follow-up, in this work, we aimed to enrich the resident oral Lactobacillus communities with a prebiotic diet to further assess their effect on the severity of OPC. We tested the effect of a prebiotic xylo-oligosaccharides (XOS)-enriched diet in the oral global bacterial composition and severity of OPC. We assessed changes in the oral microbiome composition via 16S-rRNA gene high-throughput sequencing, validated by qPCR. The impact of the prebiotic diet on Candida infection was assessed by quantifying changes in oral fungal and bacterial biomass and scoring tongue lesions. Contrary to expectations, oral Lactobacillus communities were not enriched by the XOS-supplemented diet. Yet, XOS modulated the oral microbiome composition, increasing Bifidobacterium abundance and reducing enterococci and staphylococci. In the OPC model, the XOS diet attenuated Candida virulence and bacterial dysbiosis, increasing lactobacilli and reducing enterococci on the oral mucosa. We conclude that XOS attenuates Candida virulence by promoting a bacterial microbiome structure more resilient to Candida infection. IMPORTANCE This is the first study on the effects of a prebiotic diet on the oral mucosal bacterial microbiome and an oropharyngeal candidiasis (OPC) mouse model. We found that xylo-oligosaccharides change the oral bacterial community composition and attenuate OPC. Our results contribute to the understanding of the impact of the oral bacterial communities on Candida virulence.

Determination of the Prevalence and Antimicrobial Resistance of Enterococcus faecalis and Enterococcus faecium Associated with Poultry in Four Districts in Zambia

The presence of antimicrobial-resistant Enterococci in poultry is a growing public health concern worldwide due to its potential for transmission to humans. The aim of this study was to determine the prevalence and patterns of antimicrobial resistance and to detect drug-resistant genes in Enterococcus faecalis and E. faecium in poultry from four districts in Zambia. Identification of Enterococci was conducted using phenotypic methods. Antimicrobial resistance was determined using the disc diffusion method and antimicrobial resistance genes were detected using polymerase chain reaction and gene-specific primers. The overall prevalence of Enterococci was 31.1% (153/492, 95% CI: 27.1–35.4). Enterococcus faecalis had a significantly higher prevalence at 37.9% (58/153, 95% CI: 30.3–46.1) compared with E. faecium, which had a prevalence of 10.5% (16/153, 95% CI: 6.3–16.7). Most of the E. faecalis and E. faecium isolates were resistant to tetracycline (66/74, 89.2%) and ampicillin and erythromycin (51/74, 68.9%). The majority of isolates were susceptible to vancomycin (72/74, 97.3%). The results show that poultry are a potential source of multidrug-resistant E. faecalis and E. faecium strains, which can be transmitted to humans. Resistance genes in the Enterococcus species can also be transmitted to pathogenic bacteria if they colonize the same poultry, thus threatening the safety of poultry production, leading to significant public health concerns.

A Strategy for the Recovery of Raw Ewe's Milk Microbiodiversity to Develop Natural Starter Cultures for Traditional Foods

Commercial starter cultures, composed of high concentrations of a few species/strains of lactic acid bacteria (LAB), selected based on their strong technological aptitudes, have been developed to easily and safely carry out food fermentations. Frequently applied to industrial productions, selected starter LAB easily become the dominant microbiota of products, causing a dramatic decrease in biodiversity. On the contrary, natural starter cultures, which usually characterize the most typical and Protected Designation of Origin (PDO) food products, are constituted by a multitude and an indefinite number of LAB species and strains, both starter and nonstarter, thus contributing to preserving microbial biodiversity. However, their use is not risk-free since, if obtained without heat treatment application, natural cultures can contain, together with useful, also spoilage microorganisms or pathogens that could be allowed to multiply during fermentation. In the present study, an innovative method for the production of a natural starter culture directly from raw ewe's milk, inhibiting the growth of spoilage and potentially pathogenic bacteria without applying any heat treatment, was described. The culture developed show a good degree of microbial biodiversity and could be applied to both artisanal and industrial scales, guaranteeing safety, quality constancy, technological performance reproducibility, preserving biodiversity and peculiar sensory characteristics, usually linked to traditional products, while overcoming the problems associated with the daily propagation of natural cultures.

Bacteriocinogenic Enterococcus casseliflavus Isolated from Fresh Guava Fruit (Psidium guajava): Characterization of Bacteriocin ST192Gu and Some Aspects of Its Mode of Action on Listeria spp. and Enterococcus spp

Strain ST182Gu, isolated from fresh guava fruit, was identified as Enterococcus casseliflavus on the basis of biochemical tests, sugar fermentation reactions (API20Strip), PCR with genus-specific primers, and 16S rRNA sequencing. This appears to be the first documentation of the presence of this species in guava. E. casseliflavus ST182Gu was shown to produce a 4.8 kDa class IIa bacteriocin, active against various lactic acid bacteria including Enterococcus spp. and Streptococcus spp., and Staphylococcus aureus, and different serotypes of Listeria spp. The activity of the peptide was reduced by treatment with 0.1 mg/mL proteolytic enzymes, but not by α-amylase, catalase, lipase, and 1% (w/v) sodium dodecyl sulphate (SDS), Tween-20, Tween-80, urea, NaCl, and EDTA. No change in activity was recorded after adjustment to pH values of between 2.0 and 12.0 for 2 h, and after treatment at 100 °C for 120 min or 121°C for 20 min, compared with non-treated antimicrobial peptide. The mode of action against representative susceptible bacteria was shown to be bactericidal and associated with cell lysis and enzyme- and DNA-leakage. These susceptible bacteria, Listeria ivanovii subsp. ivanovii ATCC 19119, Listeria monocytogenes ATCC 15313, and Enterococcus faecalis ATCC 19443 differed however in their sensitivity to bacteriocin ST182Gu (6,553,600 AU/mL, 102,400 AU/mL, and 51,200 AU/mL, respectively). No significant differences were detected in cell growth and bacteriocin production when strain ST182Gu was grown in MRS broth at 26 °C, 30 °C, and 37 °C for 24 h. Bacteriocin ST182Gu recovery from the surface of the producer cells showed different activity, dependent of the applied test organisms (3200, 800 and 400 AU/mL, evaluated versus L. ivanovii subsp. ivanovii ATCC 19119, L. monocytogenes ATCC 15313 and E. faecalis ATCC 19443, respectively), however, with proportional values with the activity recorded in cell free supernatant versus same test microorganisms. When bacteriocin ST182Gu was combined with sublethal doses of ciprofloxacin, synergistic inhibition of L. ivanovii subsp. ivanovii ATCC 19119 was demonstrated. This increase in ciprofloxacin sensitivity may be due to the dissipation of the proton gradient in the cell membrane of the target organism associated with exposure to bacteriocin ST182Gu. Apart from reducing the MIC of classical therapeutic antibiotics, bacteriocins such as ST182Gu may also play an important role in the treatment of multidrug resistant strains.

In Vivo Effect of a Nisin–Biogel on the Antimicrobial and Virulence Signatures of Canine Oral Enterococci

Periodontal disease is a relevant oral disease in dogs and nisin–biogel has been previously proposed to be used in its control. Enterococci, as inhabitants of the oral cavity with a high genetic versatility, are a reliable bacterial model for antimicrobial studies. Our goal was to evaluate the in vivo influence of the long-term dental application of the nisin–biogel on the virulence and antimicrobial signatures of canine oral enterococci. Twenty dogs were randomly allocated to one of two groups (treatment group—TG with nisin–biogel dental application, or control group—CG without treatment) and submitted to dental plaque sampling at day 0 and after 90 days (T90). Samples were processed for Enterococcus spp. isolation, quantification, identification, molecular typing and antimicrobial and virulence characterization. From a total of 140 enterococci, molecular typing allowed us to obtain 70 representative isolates, mostly identified as E. faecalis and E. faecium. No significant differences (p > 0.05) were observed in the virulence index of the isolates obtained from samples collected from the TG and CG at T90. At T90, a statistically significant difference (p = 0.0008) was observed in the antimicrobial resistance index between the isolates from the TC and CG. Oral enterococci were revealed to be reservoirs of high resistant and virulent phenotypes.

Prevalence of Class 1 Integron and In Vitro Effect of Antibiotic Combinations of Multidrug-Resistant Enterococcus Species Recovered from the Aquatic Environment in the Eastern Cape Province, South Africa

Enterococci are regarded as a better indication of faecal pollution in freshwater and marine waters. Their levels in seawater are positively connected with swimming-related gastrointestinal disorders. This study used an Enterococcus-specific polymerase chain reaction (PCR) to characterize the isolates. Classes 1 and 2 integrons were examined for environmental Enterococcus isolates using a standard biological procedure. All strains were assessed against a panel of 12 antibiotics from various classes using disc diffusion methods. The microdilution method was used to work out the minimum inhibitory concentration (MIC) according to the CLSI guiding principles. The combination therapy of the resistant drugs was evaluated using a checkerboard assay and a time-dependent test for assessing their bactericidal or bacteriostatic activity. The gene diversity of the tested organisms was analyzed with the aid of Enterobacterial Repetitive Intergenic Consensus (ERIC) PCR. In total, 57 Enterococcus spp. environmental samples were recovered, in which Enterococcus faecalis (33.33%) and Enterococcus faecium (59.65%) were the dominant species. Resistance to linezolid, ciprofloxacin, erythromycin, gentamicin, vancomycin, rifampicin, and tetracycline was prevalent. Fifty (50) strains tested positive for class 1 integron, more frequent in Enterococcus faecium and Enterococcus faecalis isolates, with no gene cassette array discovered. A combination of gentamicin (MIC 4 µg/mL) with vancomycin (MIC 256 µg/mL) antibiotics against Enterococcus faecalis showed antibacterial activity. In contrast, the combination of ciprofloxacin (1 µg/mL) with Ampicillin (16 µg/mL) antibiotics against Enterococcus faecalis showed a bacteriostatic effect. The ERIC-PCR analysis pointed out that most of the assessed isolates have close genetic similarities.

Development of A Rapid, Low-Cost Portable Detection Assay for Enterococci in Wastewater and Environmental Waters

Waterborne diseases are known as a leading cause of illness and death in both developing and developed countries. Several pathogens can be present in contaminated water, particularly waters containing faecal material; however, routine monitoring of all pathogens is not currently possible. Enterococcus faecalis, which is present in the microflora of human and animals has been used as a faecal indicator in water due to its abundance in surface water and soil. Accurate and fast detection methods are critical for the effective monitoring of E. faecalis in the environment. Although conventional and current molecular detection techniques provide sufficient sensitivity, specificity and throughput, their use is hampered by the long waiting period (1-6 days) to obtain results, the need for expensive laboratory equipment, skilled personnel, and cold-chain storage. Therefore, this study aimed to develop a detection system for E. faecalis that would be simple, rapid, and low-cost, using an isothermal DNA amplification assay called recombinase polymerase amplification (RPA), integrated with a lateral flow assay (LFA). The assay was found to be 100% selective for E. faecalis and capable of detecting rates as low as 2.8 × 10³ cells per 100 mL from water and wastewater, and 2.8 × 10⁴ cells per 100 mL from saline water. The assay was completed in approximately 30 min using one constant temperature (38 °C). In addition, this study demonstrated the quantitation of E. faecalis using a lateral flow strip reader for the first time, enhancing the potential use of RPA assay for the enumeration of E. faecalis in wastewater and heavily contaminated environmental waters, surface water, and wastewater. However, the sensitivity of the RPA-LFA assay for the detection of E. faecalis in tap water, saline water and in wastewater was 10-1000 times lower than that of the Enterolert-E test, depending on the water quality. Nevertheless, with further improvements, this low-cost RPA-LFA may be suitable to be used at the point-of-need (PON) if conjugated with a rapid field-deployable DNA extraction method.

Development of diagnostic tests for pathogen identification and detection of antimicrobial resistance on WHO global priority pathogens using modular real-time nucleic acid amplification test

BACKGROUND

Concerns regarding antimicrobial resistance (AMR) have resulted in the World Health Organization (WHO) designating so-called global priority pathogens (GPPs). However, little discussion has focused on the diagnosis of GPPs. To enable the simultaneous identification of pathogens and AMR, we developed a modular real-time nucleic acid amplification test (MRT-NAAT).

METHODS

Sequence-specific primers for each modular unit for MRT-NAAT pathogen identification and AMR sets were designed. The composition of the reaction mixture and the real-time PCR program were unified irrespective of primer type so to give MRT-NAAT modularity. Standard strains and clinical isolates were used to evaluate the performance of MRT-NAAT by real-time PCR and melting curve analysis. Probit analysis for the MRT-NAAT pathogen identification set was used to assess the limit of detection (LoD).

RESULTS

The MRT-NAAT pathogen identification set was made up of 15 modular units 109-199 bp in product size and with a T_ms of 75.5-87.5 °C. The LoD was < 15.548 fg/μL, and nine modular units successfully detected the target pathogens. The MRT-NAAT AMR set included 24 modular units 65-785 bp in product size with a T_ms of 75.5-87.5 °C; it showed high performance for detecting GPP target genes and variants.

CONCLUSIONS

MRT-NAAT enables pathogen identification and AMR gene detection and is time-effective. By unifying the reaction settings of each modular unit, the modularity where combinations of primers can be used according to need could be achieved. This would greatly help in reflecting the researcher's need and the AMR status of a certain region while successfully detecting pathogens and AMR genes.

Vancomycin-variable enterococci in sheep and cattle isolates and whole-genome sequencing analysis of isolates harboring vanM and vanB genes

Background

Vancomycin resistance encoded by the vanA/B/M genes in enterococci is clinically important because of the transmission of these genes between bacteria. While vancomycin resistance is determined by detecting only vanA and vanB genes by routine analyses, failure to detect vanM resistance causes vancomycin resistance to be overlooked, and clinically appropriate treatment cannot be provided.

Aims

The study aimed to examine the presence of vanM-positive enterococcal isolates in Ankara, Turkey, and to have detailed information about them with sequence analyses.

Methods

Caecal samples were collected from sheep and cattle during slaughter at different slaughterhouses in Ankara, Turkey. Enterococci isolates were identified, confirmed, and analyzed for the presence of vanA/B/M genes. Antibiotic resistance profiles of isolates were determined by the broth microdilution method. A whole genome sequence analysis of the isolates harboring the vanM and vanB genes was performed.

Results

13.7% of enterococcal isolates were determined as Enterococcus faecium and Enterococcus faecalis. 15% of these isolates contained vanB, and 40% were vanM-positive. S98b and C32 isolates were determined to contain 16 CRISPR-Cas elements. 80% of the enterococci isolates were resistant to nitrofurantoin and 15% to ciprofloxacin. The first vanM-positive vancomycin-variable enterococci (VVE) isolates from food-producing animals were identified, and the S98b strain has been assigned to Genbank with the accession number CP104083.1.

Conclusion

Therefore, new studies are needed to facilitate the identification of vanM-resistant enterococci and VVE strains.

Towards the standardization of Enterococcus culture methods for waterborne antibiotic resistance monitoring: A critical review of trends across studies

Antibiotic resistance is a major 21^st century One Health (humans, animals, environment) challenge whose spread limits options to treat bacterial infections. There is growing interest in monitoring water environments, including surface water and wastewater, which have been identified as key recipients, pathways, and sources of antibiotic resistant bacteria (ARB). Aquatic environments also facilitate the transmission and amplification of ARB. Enterococcus spp. often carry clinically-important antibiotic resistance genes and are of interest as environmental monitoring targets. Enterococcus spp. are Gram-positive bacteria that are typically of fecal origin; however, they are also found in relevant environmental niches, with various species and strains that are opportunistic human pathogens. Although the value of environmental monitoring of antibiotic-resistant Enterococcus has been recognized by both national and international organizations, lack of procedural standardization has hindered generation of comparable data needed to implement integrated surveillance programs. Here we provide a comprehensive methodological review to assess the techniques used for the culturing and characterization of antibiotic-resistant Enterococcus across water matrices for the purpose of environmental monitoring. We analyzed 117 peer-reviewed articles from 33 countries across six continents. The goal of this review is to provide a critical analysis of (i) the various methods applied globally for isolation, confirmation, and speciation of Enterococcus isolates, (ii) the different methods for profiling antibiotic resistance among enterococci, and (iii) the current prevalence of resistance to clinically-relevant antibiotics among Enterococcus spp. isolated from various environments. Finally, we provide advice regarding a path forward for standardizing culturing of Enterococcus spp. for the purpose of antibiotic resistance monitoring in wastewater and wastewater-influenced waters within a global surveillance framework.

Mining the microbiota to identify gut commensals modulating neuroinflammation in a mouse model of multiple sclerosis

BACKGROUND

The gut microbiome plays an important role in autoimmunity including multiple sclerosis and its mouse model called experimental autoimmune encephalomyelitis (EAE). Prior studies have demonstrated that the multiple sclerosis gut microbiota can contribute to disease, hence making it a potential therapeutic target. In addition, antibiotic treatment has been shown to ameliorate disease in the EAE mouse model of multiple sclerosis. Yet, to this date, the mechanisms mediating these antibiotic effects are not understood. Furthermore, there is no consensus on the gut-derived bacterial strains that drive neuroinflammation in multiple sclerosis.

RESULTS

Here, we characterized the gut microbiome of untreated and vancomycin-treated EAE mice over time to identify bacteria with neuroimmunomodulatory potential. We observed alterations in the gut microbiota composition following EAE induction. We found that vancomycin treatment ameliorates EAE, and that this protective effect is mediated via the microbiota. Notably, we observed increased abundance of bacteria known to be strong inducers of regulatory T cells, including members of Clostridium clusters XIVa and XVIII in vancomycin-treated mice during the presymptomatic phase of EAE, as well as at disease peak. We identified 50 bacterial taxa that correlate with EAE severity. Interestingly, several of these taxa exist in the human gut, and some of them have been implicated in multiple sclerosis including Anaerotruncus colihominis, a butyrate producer, which had a positive correlation with disease severity. We found that Anaerotruncus colihominis ameliorates EAE, and this is associated with induction of RORγt⁺ regulatory T cells in the mesenteric lymph nodes.

CONCLUSIONS

We identified vancomycin as a potent modulator of the gut-brain axis by promoting the proliferation of bacterial species that induce regulatory T cells. In addition, our findings reveal 50 gut commensals as regulator of the gut-brain axis that can be used to further characterize pathogenic and beneficial host-microbiota interactions in multiple sclerosis patients. Our findings suggest that elevated Anaerotruncus colihominis in multiple sclerosis patients may represent a protective mechanism associated with recovery from the disease. Video Abstract.

Dissemination of Quinupristin-Dalfopristin and Linezolid resistance genes among hospital environmental and healthy volunteer fecal isolates of Enterococcus faecalis and Enterococcus faecium

BACKGROUND

Streptogramins and linezolid are important in the treatment of infections caused by vancomycin-resistant enterococci.

PURPOSE

Then, we aimed to evaluate the resistance rates against these drugs and the prevalence of genes involved in hospital environmental and fecal normal-flora isolates of Enterococcus faecalis and Enterococcus faecium.

METHODS AND RESULTS

The strains were isolated from the stool samples and hospital environments by culturing on M-Enterococcus (ME) agar, and identified by phenotypic and genotypic microbiological tests. The disk agar diffusion method was used to identify the antimicrobial susceptibility pattern of the isolates. The genomic DNA extraction was done by the alkaline lysis method, and the PCR test was used to detect the resistance genes. A total of 145 enterococci isolates were taken, from which 84 (57.9%) isolates were detected as E. faecalis and 61 (42.06%) isolates were E. faecium. Moreover, 70 (83.33), 4 (4.76%), 1 (1.19%), and 40 (47.61%) isolates of E. faecalis and 20 (32.78%), 1 (1.63%), 4 (6.55%), and 26 (42.62%) E. faecium isolates were resistant against quinupristin-dalfopristin, linezolid, vancomycin, and erythromycin, respectively. Also, 112 (77.24%), 50 (34.48%), 39 (26.89%), 27 (18.62%), 19 (13.1%), 4 (2.75%), and 1 (0.68%) isolates were contained LsaA, vatD, vgbB, vatE, cfr, lsaE and optrA genes, respectively. None of the isolates carried the vgbA gene.

CONCLUSIONS

High-level streptogramin resistance rate and high prevalence of resistance genes in enterococci isolated from the stool of healthy persons and the hospital environment indicates the importance of possible transmission of resistance genes from these isolates to clinical ones.

Occurrence, Phenotypic and Molecular Characteristics of Vancomycin-Resistant Enterococci Isolated from Retail Raw Milk in Egypt

The aim of this study was to determine the occurrence, phenotypic and molecular characteristics of vancomycin-resistant enterococci (VRE), isolated from retail raw cow's milk. One hundred milk samples collected from retail shops in Egypt were examined for the occurrence of VRE by using kanamycin aesculin azide agar supplemented with 4 μg/mL vancomycin. PCR was conducted to determine enterococcal species and to screen the isolated strains for the presence of antibiotic resistance and virulence genes. All isolated strains were characterized by antimicrobial susceptibility testing for 12 antibiotics. From 24 samples (24%), we recovered 22 isolates (91.6%) classified as VRE (minimum inhibitory concentration ≥32) and 2 isolates (8.3%) classified as intermediate resistant to vancomycin (≤16). Enterococcus faecium (29.1%), Enterococcus faecalis (12.5%), Enterococcus casseliflavus (16.6%), and Enterococcus gallinarum (4.1%) were identified by using multiplex PCR. The genus Enterococcus was resistant to clindamycin (100%), linezolid (91.6%), teicoplanin (91.6%), erythromycin (87.5%), and tetracycline (29.1%). Co-resistance to vancomycin, teicoplanin, and linezolid was detected in 83.3% of isolates. Antibiotic resistance genes vanB, tet(M), tet(L), and erm(B) were identified in 29.1%, 16.6%, 8.3%, and 4.1% of isolates, respectively. Virulence genes gelE and esp were detected in 16.6% and 12.5% of isolates, respectively. In conclusion, the high occurrence of co-resistance to vancomycin, teicoplanin, and linezolid reported in this study is alarming. The high frequency of linezolid resistance prompts increased the attention of researchers to routinely perform linezolid susceptibility in food isolates. This study declares potential food safety risks from consumption and improper handling of raw milk regarding clinically important bacteria and promotes necessary legislation for forbidding the selling and consumption of retail raw milk.

Potential Probiotic Enterococcus faecium OV3-6 and Its Bioactive Peptide as Alternative Bio-Preservation

Probiotic Enterococcus faecium OV3-6 and its secreted active peptide were characterized and investigated. The strain survived in simulated gastric and small intestinal conditions at 88.16% and 94.33%, respectively. The safety assessment revealed that the strain was shown α-hemolysis and susceptible to most clinically relevant antibiotics, but intermediate sensitivity to erythromycin and kanamycin was found. It does not harbor any virulence genes except for the efaA_fm gene. Both of its living cells and the cell-free supernatants (CFS) of the strain significantly reduced the adhesion of E. coli and S. Typhi on Caco-2 cells. The strain can regulate the secretion of pro and inflammatory cytokines, IL-6 and IL-12 and induce the secretion of anti-inflammatory IL-10 of the Caco-2 cell. The strain can prevent the growth of Gram-positive strains belonging to the genera Bacillus, Carnobacterium, Listeria, and Staphylococcus. It also presented the entP gene that involves the production of bacteriocin named enterocin P. The antimicrobial peptide was matched 40% with 50S ribosomal proteins L29 (7.325 kDa), as revealed by LC-MS/MS. This active peptide exhibits heat stability, is stable over a wide pH range of 2−10, and maintains its activity at −20 and 4 °C for 12 weeks of storage. Altogether, E. faecium OV3-6 thus has potential for consideration as a probiotic and bio-preservative for applied use as a fermented food starter culture and in functional food or feed industries.

Antimicrobial Resistance of Enterococcus sp. Isolated from Sheep and Goat Cheeses

This study aimed to calculate the proportion of antibiotic resistance profiles of Enterococcus faecium, E. faecalis, and E. durans isolated from traditional sheep and goat cheeses obtained from a selected border area of Slovakia with Hungary (region Slanské vrchy). A total of 110 Enterococcus sp. were isolated from cheese samples, of which 52 strains (E. faecium (12), E. faecalis (28), E. durans (12)) were represented. After isolation and identification by polymerase chain reaction and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry, the enterococci (E. faecium, E. faecalis, and E. durans) were submitted to susceptibility tests against nine antimicrobial agents. In general, strains of E. faecalis were more resistant than E. durans and E. faecium. A high percentage of resistance was noted in E. faecalis to rifampicin (100%), vancomycin (85.7%), teicoplanin (71.4%), erythromycin (71.4%), minocycline (57.1%), nitrofurantoin (57.1%), ciprofloxacin (14.3%), and levofloxacin (14.3%). E. durans showed resistance to rifampicin (100%), teicoplanin (100%), vancomycin (66.7%), erythromycin (66.7%), nitrofurantoin (66.7%), and minocycline (33.3%), and E. faecium showed resistance to vancomycin, teicoplanin, and erythromycin (100%). Multidrug-resistant strains were confirmed in 80% of the 52 strains in this study. Continuous identification of Enterococcus sp. and monitoring of their incidence and emerging antibiotic resistance is important in order to prevent a potential risk to public health caused by the contamination of milk and other dairy products, such as cheeses, made on farm level.

Enterococcal contamination of hospital environments in KwaZulu-Natal, South Africa

AIMS

Enterococci are implicated in hospital-acquired infections and show high tenacity on inanimate objects in the hospital environment. This study investigated the prevalence of Enterococcus spp. in selected wards in public hospitals at four levels of healthcare from a district in KwaZulu-Natal, South Africa.

METHODS AND RESULTS

Swabs were collected from frequently touched areas in the paediatric wards and intensive care units (ICUs). Presumptive Enterococcus spp. were isolated and confirmed to genus and species levels, followed by Kirby-Bauer disk diffusion against 14 antibiotics. The results showed that enterococci were recovered from all 11 surfaces tested with the highest contamination rate observed on occupied beds and mops used to clean floors. A total number of 295 Enterococcus was identified. Polymerase chain reaction identified Enterococcus faecalis 83.1% (245/295) and Enterococcus faecium 12.9% (38/295), while whole genome sequencing identified Enterococcus gallinarum 2.0% (6/295) and Enterococcus casseliflavus 2.0% (6/295). Significant prevalence was observed in paediatric wards 64.1% (189/295) compared with the ICUs 35.9% (106/295), p < 0.05, in central, regional and district hospitals. Collectively, 82.0% (242/295) of enterococcal isolates were multidrug resistant, and 80 different antibiograms were observed. The most prominent antibiogram for E. faecium was CIP-RIF-NIT-TET-ERY and for E. faecalis CIP-TET-ERY.

CONCLUSION

E. faecalis was the most frequent enterococcal species isolated in all the hospitals investigated and correlates with studies conducted elsewhere. A substantially greater number of isolates were recovered from the paediatric wards compared with ICUs, and thus improved standards should be developed for infection control practices. It is suggested that the elevated use of antibiotics contributed to the increased nonsusceptible isolates observed from ICUs. This study highlighted the high recovery rate of enterococci in the hospital environment even in a nonoutbreak setting.

SIGNIFICANCE AND IMPACT OF THE STUDY

Enterocci had a high prevalence rate on the surfaces within the hospitals studied. This study gives an insight into the possible roles all healthcare staff may play in infection control intervention, including proper handling of hospital cleaning equipment and lack of knowledge about the potential for bacteria dissemination.

Genomic Analysis of Enterococcus spp. Isolated From a Wastewater Treatment Plant and Its Associated Waters in Umgungundlovu District, South Africa

We investigated the antibiotic resistome, mobilome, virulome, and phylogenomic lineages of Enterococcus spp. obtained from a wastewater treatment plant and its associated waters using whole-genome sequencing (WGS) and bioinformatics tools. The whole genomes of Enterococcus isolates including Enterococcus faecalis (n = 4), Enterococcus faecium (n = 5), Enterococcus hirae (n = 2), and Enterococcus durans (n = 1) with similar resistance patterns from different sampling sites and time points were sequenced on an Illumina MiSeq machine. Multilocus sequence typing (MLST) analysis revealed two E. faecalis isolates that had a common sequence type ST179; the rest had unique sequence types ST841, and ST300. The E. faecium genomes belonged to 3 sequence types, ST94 (n = 2), ST361 (n = 2), and ST1096 (n = 1). Detected resistance genes included those encoding tetracycline [tet(S), tet(M), and tet(L)], and macrolides [msr(C), msr(D), erm(B), and mef(A)] resistance. Antibiotic resistance genes were associated with insertion sequences (IS6, ISL3, and IS982), and transposons (Tn3 and Tn6000). The tet(M) resistance gene was consistently found associated with a conjugative transposon protein (TcpC). A total of 20 different virulence genes were identified in E. faecalis and E. faecium including those encoding for sex pheromones (cCF10, cOB1, cad, and came), adhesion (ace, SrtA, ebpA, ebpC, and efaAfs), and cell invasion (hylA and hylB). Several virulence genes were associated with the insertion sequence IS256. No virulence genes were detected in E. hirae and E. durans. Phylogenetic analysis revealed that all Enterococcus spp. isolates were more closely related to animal and environmental isolates than clinical isolates. Enterococcus spp. with a diverse range of resistance and virulence genes as well as associated mobile genetic elements (MGEs) exist in the wastewater environment in South Africa.

Occurrence of multidrug-resistant Enterococcus faecium isolated from environmental samples

Enterococcus species are present in the microbiota of humans and animals and have also been described in the environment. Among the species, Enterococcus faecium is one of the main pathogens associated with nosocomial infections worldwide. Enterococcus faecium isolates resistant to different classes of antimicrobials have been increasingly reported, including multidrug-resistant (MDR) isolates in environmental sources, which is worrying. Therefore, this study aimed to characterize E. faecium isolates obtained from soil and water samples regarding antimicrobial resistance and virulence determinants. A total 40 E. faecium isolates were recovered from 171 environmental samples. All isolates were classified as MDR, highlighting the resistance to the fluoroquinolones class, linezolid and vancomycin. Furthermore, high-level aminoglycoside resistance and high-level ciprofloxacin resistance were detected in some isolates. Several clinically relevant antimicrobial resistance genes were found, including vanC1, ermB, ermC, mefAE, tetM, tetL, ant(6')-Ia, ant(4')-Ia, aph(3')-IIIa and aac(6')-Ie-aph(2″)-Ia. Three virulence genes were detected among the MDR E. faecium isolates, such as esp, gelE and ace. The results of this study contribute to a better understanding of MDR E. faecium isolates carrying antimicrobial resistance and virulence genes in environmental sources and report for the first time in the world the presence of vanC1-producing E. faecium isolated from soil.

Antimicrobial Resistance of Campylobacter jejuni, Escherichia coli and Enterococcus faecalis Commensal Isolates from Laying Hen Farms in Spain

Simple Summary

Antimicrobial resistance (AMR) is a global threat for human and animal health. Few studies have been carried out in laying hens. We evaluated the antimicrobial susceptibility of commensal Campylobacter jejuni, Escherichia coli, and Enterococcus faecalis isolates in Spanish laying hens in 2018. C. jejuni was highly resistant, and a medium proportion of the isolates were susceptible to all the antimicrobials studied. E. coli showed medium to high percentages of resistance to the antibiotic categories of highest public health risk concern (A and B). Only a low proportion of the isolates were susceptible to all antimicrobials. The E. faecalis resistance to antimicrobials was variable, and very few isolates were susceptible to all antimicrobials. Novel data on AMR in laying hen commensal isolates in Spain was provided, and the AMR levels differed from those reported for poultry in the EU. High resistance to key drugs used in human medicine was found. Therefore, laying hens could be a source of AMR for humans, thus, representing a public health risk.

Abstract

Antimicrobial resistance (AMR) is a global threat for human and animal health. Few studies have been carried out in laying hens. We evaluated the antimicrobial susceptibility of commensal Campylobacter jejuni, Escherichia coli, and Enterococcus faecalis isolates in Spanish laying hens in 2018. The Minimum Inhibitory Concentration (MIC) was used to identify any AMR of the studied isolates by means of a broth microdilution method. C. jejuni was highly resistant to the B category antimicrobials, and 52% of the isolates were susceptible to all the antimicrobials tested. E. coli showed medium and high percentages of resistance to the B and A antibiotic categories, respectively, and 33.33% of the isolates were susceptible to all antimicrobials. The E. faecalis resistance to A category antimicrobials was variable, and 4.62% of the isolates were susceptible to all antimicrobials. In our work, novel data on AMR in laying hen commensal isolates in Spain is provided, and the AMR levels differ from those reported for poultry in the EU. A high resistance to key drugs for human medicine was found, representing a public health risk.

Rethinking Manure Application: Increase in Multidrug-Resistant Enterococcus spp. in Agricultural Soil Following Chicken Litter Application

The current study investigated the impact of chicken litter application on the abundance of multidrug-resistant Enterococcus spp. in agricultural soil. Soil samples were collected from five different strategic places on a sugarcane farm before and after manure application for four months. Chicken litter samples were also collected. Enterococci were enumerated using the Enterolert^®/Quanti-Tray 2000^® system and confirm and differentiated into species using real-time PCR. The antibiotic susceptibility profile of the isolates was determined using the disk diffusion method following the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. The overall mean bacterial count was significantly higher (p < 0.05) in manure-amended soil (3.87 × 10⁷ MPN/g) than unamended soil (2.89 × 10⁷ MPN/g). Eight hundred and thirty-five enterococci (680 from soil and 155 from litter) were isolated, with E. casseliflavus being the most prevalent species (469; 56.2%) and E. gallinarum being the least (16; 1.2%). Approximately 56% of all the isolates were resistant to at least one antibiotic tested, with the highest resistance observed against tetracycline (33%) and the lowest against chloramphenicol (0.1%); 17% of E. faecium were resistant to quinupristin-dalfopristin. Additionally, 27.9% (130/466) of the isolates were multidrug-resistant, with litter-amended soil harbouring more multidrug-resistant (MDR) isolates (67.7%; 88/130) than unamended soil (10.0%; 13/130). All isolates were susceptible to tigecycline, linezolid and gentamicin. About 7% of the isolates had a multiple antimicrobial resistance index > 0.2, indicative of high antibiotic exposure. Although organic fertilizers are regarded as eco-friendly compared to chemical fertilizers for improving soil fertility, the application of untreated animal manure could promote the accumulation of antibiotics and their residues and antibiotic-resistant bacteria in the soil, creating an environmental reservoir of antimicrobial resistance, with potential human and environmental health risks.

Longitudinal Surveillance of Antibiotic Resistance in Escherichia coli and Enterococcus spp. from a Wastewater Treatment Plant and Its Associated Waters in KwaZulu-Natal, South Africa

We assessed the prevalence, distribution, and antibiotic resistance patterns of Escherichia coli and Enterococcus spp. isolated from raw and treated wastewater of a major wastewater treatment plant (WWTP) in KwaZulu-Natal, South Africa and the receiving river water upstream and downstream from the WWTP discharge point. Escherichia coli and enterococci were isolated and counted using the Colilert^®-18 Quanti-Tray^® 2000 and Enterolert^®-18 Quanti-Tray 2000 systems, respectively. A total of 580 quantitative PCR-confirmed E. coli and 579 enterococci were randomly chosen from positive samples and tested for in vitro antibiotic susceptibility using the disk diffusion assay against 20 and 16 antibiotics, respectively. The removal success of the bacterial species through the treatment procedure at the WWTP was expressed as log removal values (LRVs). Most E. coli were susceptible to meropenem (94.8%) and piperacillin-tazobactam (92.9%), with most Enterococcus susceptible to ampicillin (97.8%) and vancomycin (96.7%). In total, 376 (64.8%) E. coli and 468 (80.8%) Enterococcus isolates showed multidrug resistance (MDR). A total of 42.4% (246/580) E. coli and 65.1% (377/579) enterococci isolates had multiple antibiotic resistance indices >0.2. The LRV for E. coli ranged from 2.97 to 3.99, and for enterococci the range was observed from 1.83 to 3.98. A high proportion of MDR E. coli and enterococci were present at all sampled sites, indicating insufficient removal during wastewater treatment. There is a need to appraise the public health risks associated with bacterial contamination of environmental waters arising from such WWTPs to protect the health of users of the receiving water bodies.

Identification of drug-resistant phenotypes and resistance genes in Enterococcus faecalis isolates from animal feces originating in Xinjiang, People’s Republic of China

This study examined the presence and the antibiotic resistance patterns of Enterococcus faecalis isolated from the feces of 285 animals. Polymerase chain reaction tests verified the presence of E. faecalis from 49 pigs, 20 cows, 174 sheep, 17 horses, 21 chickens, and four dung beetles. Bacterial strains from different animals showed differences in susceptibility and resistance to the tested antimicrobials. The isolates exhibited resistance to ampicillin (6.32%), ciprofloxacin (40.00%), nitrofurantoin (1.40%), erythromycin (54.04%), streptomycin (82.11%), tetracycline (45.26%), amoxicillin (64.91%), penicillin (92.28%), and vancomycin (0.35%). The resistant strains also possessed varying complements of resistance genes including tem (77.89%), tetM (33.68%), gyrA (37.54%), parC (34.74%), aph(3′)-III (22.46%), aac(6′)/aph2″ (10.88%), and ant(6′)-I (8.42%). Genes for vancomycin resistance (vanB and vanC) and erythromycin resistance (mefA) were not detected. These results indicate high levels of antibiotic resistance among the isolates, although no positive correlation was observed between resistance genes and antibiotic resistance spectrum.

Resistance patterns to C and D antibiotic categories for veterinary use of Campylobacter spp., Escherichia coli and Enterococcus spp. commensal isolates from laying hen farms in Spain during 2018

Antimicrobial Resistance (AMR) is a global threat for human and animal health. Few studies have been carried out on laying hens. The aim of this work was to evaluate the antimicrobial susceptibility of commensal Campylobacter spp., E. coli, and Enterococcus spp. isolates in Spanish laying hens in 2018. Samples were collected from 39 laying hen farms. The microorganisms of interest were isolated and confirmed by PCR. The Minimum Inhibitory Concentration (MIC) to antimicrobials of C and D categories were determined. 195 E. coli, 195 Enterococcus spp. and 25 Campylobacter spp. isolates were obtained. E. coli isolates showed high resistance to D category antimicrobials (sulfamethoxazole 76.41 %, tetracycline 62.05 %, trimethoprim 50.77 %, ampicillin 30.77 %) and lower resistance to C category (azithromycin 30.26 %, gentamicin 12.31 %, chloramphenicol 4.62 %). A 10.26 % of E. coli isolates were susceptible to all antimicrobials tested, Multi Drug Resistance (MDR) to 3 antimicrobial families was found in 23.08 % of the isolates and 13.85 % were MDR to 4 families, being Erythromycin-Sulfamethoxazole-Tetracycline the most common resistance profile (10.77 %). Enterococcus spp. showed very high resistance to D category tetracycline (78.47 %) and C category erythromycin (76.42 %). The 11.79 % of Enterococcus spp. isolates were susceptible to all antimicrobials and 53.33 % were resistant to 2 families, being Erythromycin-Tetracycline the most common AMR profile (51.79 %). Regarding Campylobacter spp., resistance to tetracycline (48 %) was higher than resistance to C category antimicrobials (erythromycin 28 %, streptomycin 24 %, gentamicin 16 %). There was a 52 % sensitivity to all tested antimicrobials and 24 % showed MDR to aminoglycosides, macrolides and tetracyclines (Gentamicin-Streptomycin-Erythromycin-Tetracycline MDR profile). Novel data on AMR in laying hen commensal isolates in Spain was provided. High resistance to several antimicrobials was found, especially to key drugs for the treatment of zoonosis, which represents a public health risk. Better surveillance and careful regulation of antimicrobial use is required in laying hen production.

Quantitative microbial risk assessment for waterborne pathogens in a wastewater treatment plant and its receiving surface water body

BACKGROUND

Access to safe water for drinking and domestic activities remains a challenge in emerging economies like South Africa, forcing resource-limited communities to use microbiologically polluted river water for personal and household purposes, posing a public health risk. This study quantified bacterial contamination and the potential health hazards that wastewater treatment plant (WWTP) workers and communities may face after exposure to waterborne pathogenic bacteria in a WWTP and its associated surface water, respectively.

RESULTS

Escherichia coli (Colilert®-18/ Quanti-Tray® 2000) and enterococci (Enterolert®/ Quanti-Tray® 2000) were quantified and definitively identified by real-time polymerase chain reaction targeting the uidA and tuf genes, respectively. An approximate beta-Poisson dose-response model was used to estimate the probability of infection (Pi) with pathogenic E. coli. Mean E. coli concentration ranged from 2.60E+ 02/100 mL to 4.84E+ 06/100 mL; enterococci ranged from 2.60E+ 02/100 mL to 3.19E+ 06/100 mL across all sampled sites. Of the 580 E. coli isolates obtained from this study, 89.1% were intestinal, and 7.6% were extraintestinal pathogenic E. coli. The 579 enterococci obtained were 50.4% E. faecalis (50.4%), 31.4% E. faecium, 3.5%, E. casseliflavus and 0.7% E. gallinarum. The community health risk stemming from the use of the water for recreational and domestic purposes revealed a greater health risk (Pi) from the ingestion of 1 mL of river water from upstream (range, 55.1-92.9%) than downstream (range, 26.8-65.3%) sites. The occupational risk of infection with pathogenic E. coli for workers resulting from a once-off unintentional consumption of 1 mL of water was 0% (effluent) and 23.8% (raw influent). Multiple weekly exposures of 1 mL over a year could result in a Pi of 1.2 and 100% for the effluent and influent, respectively.

CONCLUSION

Our findings reveal that there is a potentially high risk of infection for WWTP workers and communities that use river water upstream and downstream of the investigated WWTP.

Identification of Clinically Relevant Streptococcus and Enterococcus Species Based on Biochemical Methods and 16S rRNA, sodA, tuf, rpoB, and recA Gene Sequencing

Streptococci and enterococci are significant opportunistic pathogens in epidemiology and infectious medicine. High genetic and taxonomic similarities and several reclassifications within genera are the most challenging in species identification. The aim of this study was to identify Streptococcus and Enterococcus species using genetic and phenotypic methods and to determine the most discriminatory identification method. Thirty strains recovered from clinical samples representing 15 streptococcal species, five enterococcal species, and four nonstreptococcal species were subjected to bacterial identification by the Vitek^® 2 system and Sanger-based sequencing methods targeting the 16S rRNA, sodA, tuf, rpoB, and recA genes. Phenotypic methods allowed the identification of 10 streptococcal strains, five enterococcal strains, and four nonstreptococcal strains (Leuconostoc, Granulicatella, and Globicatella genera). The combination of sequencing methods allowed the identification of 21 streptococcal strains, five enterococcal strains, and four nonstreptococcal strains. The 16S rRNA and rpoB genes had the highest identification potential. Only a combination of several molecular methods was sufficient for unambiguous confirmation of species identity. This study will be useful for comparison of several identification methods, both those used as a first choice in routine microbiology and those used for final confirmation.

Evaluation of commercial veterinary probiotics containing enterococci for transferrable vancomycin resistance genes

Objective

Vancomycin resistant enterococci (VRE) are of significant public health concern. The identification of VRE in livestock and food has increased. The objective of this study was to determine if the transferrable vancomycin resistance genes vanA and vanB were present in probiotics marketed for use in animals that claimed to contain Enterococcus spp.

Results

Of the 40 products selected, Enterococcus spp. DNA was successfully extracted from 36 products. Of these 36 products with enterococcal DNA, 2 (6%) had a PCR product consistent with vanA which was confirmed by sequencing. None of the products appeared to contain vanB.

Antimicrobial resistance and genetic relationships of enterococci from siblings and non-siblings Heliconius erato phyllis caterpillars

BACKGROUND

Studies evaluating bacteria in insects can provide information about host-microorganism-environment interactions. The gut microbial community has a profound effect on different physiological functions of insects. Enterococcus spp. are part of the gut community in humans and other animals, as well as in insects. The presence and antimicrobial resistance profile of enterococci are well studied in different animals; however, data for Heliconius erato phyllis (Lepidoptera: Nymphalidae) do not yet exist. Therefore, the aims of this study were to evaluate the distribution of enterococcal species, their antimicrobial resistance profile and virulence genes, and the genetic relationships between enterococci isolated from fecal samples from sibling and non-sibling H. erato phyllis caterpillars collected from different sites in South Brazil.

METHODS

Three H. erato phyllis females were captured (two from a forest fragment and one from an urban area), and kept individually in open-air insectaries. Eggs were collected and caterpillars (siblings and non-siblings) were fed daily with Passiflora suberosa leaves. Fecal samples (n = 12) were collected from fifth-instar caterpillars, inoculated in selective medium, and 15 bacterial colonies were randomly selected from each sample. Enterococci were identified by PCR and MALDI-TOF, analyzed by disk diffusion antimicrobial susceptibility tests, and screened for resistance and virulence genes by PCR. The genetic relationships between the strains were determined using pulsed-field gel electrophoresis (PFGE).

RESULTS

A total of 178 enterococci strains were identified: E. casseliflavus (74.15%; n = 132), E. mundtii (21.34%; n = 38), E. faecalis (1.12%; n = 2) and Enterococcus sp. (3.37%; n = 6). High rates of resistance to rifampicin (56%) and erythromycin (31%) were observed; 120 (67.41%) of the isolates showed resistance to at least one antibiotic and six (3.37%) were multidrug-resistant.None of the erythromycin-resistant strains was positive for the erm(B) and msrC genes. The virulence genes esp, ace, and gelE were observed in 35%, 7%, and 1% of the strains, respectively. PFGE separated the enterococci into 22 patterns, four being composed of strains from sibling caterpillars.

CONCLUSION

Enterococcus casseliflavus was the dominant species in fecal samples of fifth-instar caterpillars. Resistant enterococci strains may be related to environmental pollution or the resistome. The PFGE analysis showed genetic relationships between some strains, suggesting that the enterococci isolated from fecal samples of the sibling caterpillars might have come from common sources, e.g., via diet (herbivory) and/or vertical transmission (through the egg surface). Further studies will be conducted to better understand the role of Enterococcus in the microbial community of the gastrointestinal tract of these insects, and the mechanisms involved in acquisition and maintenance of enterococci.

CRISPR elements and their association with antimicrobial resistance and virulence genes among vancomycin-resistant and vancomycin-susceptible enterococci recovered from human and food sources

We aimed to investigate the occurrence of CRISPR elements in the genomes of vancomycin-resistant (VRE) and vancomycin-susceptible (VSE) enterococci and their association with the presence of antimicrobial resistance and virulence genes. We analyzed 180 isolates, including 91 VRE and 89 VSE. Isolates were identified by PCR or MALDI-TOF. Antimicrobial susceptibility and MICs for vancomycin were determined by the disk-diffusion method and E-test®, respectively. The presence of resistance and virulence genes, as well as CRISPR elements, was investigated by PCR. We identified 95 (53%) E. faecalis, 78 (43%) E. faecium, five (2.8%) E. gallinarum, and one (0.6% each) E. casseliflavus and E. durans. The highest and the lowest non-susceptibility frequencies were observed for erythromycin (n = 152; 84.4%) and fosfomycin (n = 5; 2.8%), respectively. Most erythromycin-resistant isolates had the erm(B) gene (106/152; 69.7%). Of 118 (65.6%) isolates with high-level resistance to aminoglycoside, 69 (58.5%) had at least one aminoglycoside resistance gene, mostly ant(6)-Ia and aac(6')-Ie + aph(2″)-Ia. We found at least one virulence gene among 135 (75%) isolates, mostly gelE (79/180; 43.9%). Ninety-two (51.1%) isolates had at least one CRISPR element, especially CRISPR3 (62/92; 67.4%). CRISPR elements were more common among E. faecalis, in which we observed a relationship between the absence of CRISPR and the presence of the vanA resistance gene, and the hyl and esp virulence genes. Among VRE. faecium, a relationship was found between the absence of CRISPR and the hyl gene. In conclusion, we found evident associations between the lack of CRISPR elements with species, multidrug resistance, and major resistance- and virulence-associated genes.

Molecular epidemiology of antibiotic-resistant Enterococcus spp. from the farm-to-fork continuum in intensive poultry production in KwaZulu-Natal, South Africa

The poultry industry is among the main protein suppliers worldwide. Thus, this study determined the antibiotic resistance and virulence profiles of Enterococcus spp. along the farm-to-fork production chain of an intensive poultry system in the uMgungundlovu District, Kwazulu-Natal, South Africa. Overall, 162 samples along the continuum (growth phase, transport and post-slaughter) were evaluated for the presence of Enterococcus spp. using selective media, biochemical tests and polymerase chain reaction (PCR). Resistance profiles were assessed by Kirby-Bauer disk diffusion method following the WHO-AGISAR recommended antibiotics panel for Enterococcus spp. Antibiotic resistance and virulence genes were detected using real-time PCR. Clonal relatedness was evaluated by REP-PCR. Overall, 131 isolates were recovered across the continuum, (34% E. faecalis, 32% E. faecium, 2% E. gallinarum and 32% other Enterococcus spp.). Resistance to tetracycline (79%), erythromycin (70%), nitrofurantoin (18%), ampicillin (15%), streptomycin (15%), chloramphenicol (10%), ciprofloxacin (4%), tigecycline (4%), gentamicin (4%), teicoplanin (3%) was observed among all Enterococcus spp.; no vancomycin resistance (0%) was recorded. Also, 24% of E. faecium were resistant to quinupristin-dalfopristin. Twenty-four multidrug resistance (MDR) antibiograms were observed across all species; E. faecium (43%) showed the highest frequency of MDR. The most frequently observed antibiotic resistomes were tetM (76%) and ermB (66%) while smaller percentages were noted for aph(3')-IIIa (12%) and vanC1 (1%). Virulence genes efaAFs (100%), cpd (96%) and gelE (80%) were more prevalent in E. faecalis. Clonality revealed that isolates along the continuum were highly diverse with major REP-types consisting of isolates from the same sampling point. This study highlights the diversity of MDR Enterococcus in the food chain with isolates harbouring resistance and virulence genes. These could be reservoirs for the potential transfer of pathogenic enterococci carrying these genes from poultry to humans through the food chain continuum, thus, underscoring the need for routine antibiotic resistance surveillance in food animals.

Development of a reference data set for assigning Streptococcus and Enterococcus species based on next generation sequencing of the 16S-23S rRNA region

Background

Many members of Streptococcus and Enterococcus genera are clinically relevant opportunistic pathogens warranting accurate and rapid identification for targeted therapy. Currently, the developed method based on next generation sequencing (NGS) of the 16S-23S rRNA region proved to be a rapid, reliable and precise approach for species identification directly from polymicrobial and challenging clinical samples. The introduction of this new method to routine diagnostics is hindered by a lack of the reference sequences for the 16S-23S rRNA region for many bacterial species. The aim of this study was to develop a careful assignment for streptococcal and enterococcal species based on NGS of the 16S-23S rRNA region.

Methods

Thirty two strains recovered from clinical samples and 19 reference strains representing 42 streptococcal species and nine enterococcal species were subjected to bacterial identification by four Sanger-based sequencing methods targeting the genes encoding (i) 16S rRNA, (ii) sodA, (iii) tuf and (iv) rpoB; and NGS of the 16S-23S rRNA region.

Results

This study allowed obtainment and deposition of reference sequences of the 16S-23S rRNA region for 15 streptococcal and 3 enterococcal species followed by enrichment for 27 and 6 species, respectively, for which reference sequences were available in the databases. For Streptococcus, NGS of the 16S-23S rRNA region was as discriminative as Sanger sequencing of the tuf and rpoB genes allowing for an unambiguous identification of 93% of analyzed species. For Enterococcus, sodA, tuf and rpoB genes sequencing allowed for identification of all species, while the NGS-based method did not allow for identification of only one enterococcal species. For both genera, the sequence analysis of the 16S rRNA gene was endowed with a low identification potential and was inferior to that of other tested identification methods. Moreover, in case of phylogenetically related species the sequence analysis of only the intergenic spacer region was not sufficient enough to precisely identify Streptococcus strains at the species level.

Conclusions

Based on the developed reference dataset, clinically relevant streptococcal and enterococcal species can now be reliably identified by 16S-23S rRNA sequences in samples. This study will be useful for introduction of a novel diagnostic tool, NGS of the 16S-23S rRNA region, which undoubtedly is an improvement for reliable culture-independent species identification directly from polymicrobially constituted clinical samples.

Phenotypic and genotypic methods for identification of slime layer production, efflux pump activity, and antimicrobial resistance genes as potential causes of the antimicrobial resistance of some mastitis pathogens from farms in Menoufia, Egypt

Mastitis caused by multi- or pan-drug resistant bacteria is a growing health concern. A total of 110 milk samples were collected: Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae, Enterococcus faecalis, and Escherichia coli were present in 54/110 (49.09%), 37/110 (33.63%), 25/110 (22.72%), 7/110 (6.36%), and 50/110 (45.45%) samples, respectively. A total of 20 methicillin-resistant S. aureus (MRSA) isolates, 19 Streptococcus sp. isolates, and 15 E. coli isolates were selected, and 100% were positive for (coagulase and hemolysins), streptokinase, and hemolytic activity, respectively. A number of 11 E. coli isolates were serotyped, and the serotypes were: O26, O55, O111, O119, O124, O125, O127, and O158. The antimicrobial resistance index ranges for MRSA, Streptococcus sp., and E. coli were 0.49-0.83, 0.39-0.83, and 0.56-1, respectively. The most effective antimicrobials on Gram-positive isolates were cephradine, ciprofloxacin, doxycycline, norfloxacin, and vancomycin, while doxycycline and norfloxacin were effective on E. coli serotypes. All of the selected isolates exhibited slime layer production. The efflux pumps of the 12 MRSA, 12 Streptococcus sp., and 11 E. coli isolates exhibited activity with ethidium bromide concentrations of 1, 1.5, and 0.5 µg/ml, respectively. There was a simultaneous antimicrobial activity of the efflux pump inhibitor chlorpromazine with amoxicillin/clavulanic acid, erythromycin, and oxacillin, to which the isolates were resistant. The 12 MRSA isolates harboured the methicillin resistance genes mec(A,A1, and A2), mecA1, and mecC at frequencies of 9/12 (75%), 9/12 (75%), and 8/12 (66.7%), respectively, and the penicillin resistance gene BlaZ was present at a frequency of 5/12 (41.7%). The distributions of erm(A), erm(B), erm(C), erm(F), erm(G), and erm(Q) were 8/12 (66.7%), 5/12 (41.7%), 12/12 (100%), 2/12 (16.7%), 0/12 (0.0%), and 8/12 (66.7%), respectively. The 12 Streptococcus sp. isolates harboured mec(A, A1, and A2), mecA1, mecC, and blaZ at rates of 4/12 (33.33%), 4/12 (33.33%), 5/12 (41.7%), and 4/12 (33.33%), respectively. The frequencies of erm(A) and erm(F) were 4/12 (33.33%), and 9/12 (75%), respectively. The 11 E. coli isolates harboured the extended-spectrum β-lactamases integrase1, integrase2, blaCTX-M, blaCTX-M-1, and blaTEM at frequencies of 10/11 (90.90%), 11/11 (100%), 9/11 (81.81%), 6/11 (54.54%), and 10/11 (90.90%), respectively. Moreover, the frequencies of erm(A), erm(B), erm(C), erm(F), erm(G), and erm(Q) were 7/11 (63.63%), 4/11 (36.36%), 4/11 (36.36%), 5/11 (45.45%), 10/11 (90.90%), and 10/11 (90.90%), respectively. Our results demonstrated the high antimicrobial resistance of the investigated isolates and confirmed the existence of multiple mechanisms underlying multidrug resistance.

Recreational water quality status of the Kidd's Beach as determined by its physicochemical and bacteriological quality parameters

Coastal water resources are habitually exposed to indiscriminate anthropogenic pollution. However, due to their negative consequences to the public health, recreational waters require continuous monitoring for disease-causing organisms as a way of preventing ailments associated with swimming. As a result, the present study assessed the physicochemical parameters and microbial loads of water samples collected from six different sampling points on Kidd's Beach using standard analytical procedures. Generated data were analysed with One-way ANOVA and spearman correlation (at 95%). The physicochemical qualities varied as follows: pH (7.21–8.23), temperature (18.46–27.63 °C), turbidity (0–25.67 NTU), electrical conductivity (22723–62067 μS/cm), total dissolved solids (7662–31037 mg/L), and salinity (8.95–41.84 PSU). All these measured parameters were significantly different (P < 0.05) with respect to the sampling sites. Presumptive Enterococcus counts ranged from 64 – 168 CFU/100 mL of water samples. Out of 409 presumptive Enterococcus isolates obtained from the culture-based method, 67 were confirmed to be Enterococcus by PCR-techniques. From the 67 confirmed isolates, 19(E. faecalis) and 40(E. feacium) while 8(other species that were non-targeted). Findings from this study shown that Kidd's Beach water samples contain some pathogenic bacteria that pose high risk to the public health and make it to be unfit for recreational use when compared to DWAF and US EPA guidelines. Therefore, effort should be made to strictly control all activities contributing to the level of pollution in the marine environment.

Structural and mechanistic insights into EchAMP: A antimicrobial protein from the Echidna milk

BACKGROUND

Antibiotic resistance is a problem that necessitates the identification of new antimicrobial molecules. Milk is known to have molecules with antimicrobial properties (AMPs). Echidna Antimicrobial Protein (EchAMP) is one such lactation specific AMP exclusively found in the milk of Echidna, an egg-laying mammal geographically restricted to Australia and New Guinea. Previous studies established that EchAMP exhibits substantial bacteriostatic activity against multiple bacterial genera. However, the subsequent structural and functional studies were hindered due to the unavailability of pure protein.

RESULTS

In this study, we expressed EchAMP protein using a heterologous expression system and successfully purified it to >95% homogeneity. The purified recombinant protein exhibits bacteriolytic activity against both Gram-positive and Gram-negative bacteria as confirmed by live-dead staining and scanning electron microscopy. Structurally, this AMP belongs to the family of intrinsically disordered proteins (IDPs) as deciphered by the circular-dichroism, tryptophan fluorescence, and NMR spectroscopy. Nonetheless, EchAMP has the propensity to acquire structure with amphipathic molecules, or membrane mimics like SDS, lipopolysaccharides, and liposomes as again observed through multiple spectroscopic techniques.

CONCLUSIONS

Recombinant EchAMP exhibits broad-spectrum bacteriolytic activity by compromising the bacterial cell membrane integrity. Hence, we propose that this intrinsically disordered antimicrobial protein interact with the bacterial cell membrane and undergoes conformational changes to form channels in the membrane resulting in cell lysis.

GENERAL SIGNIFICANCE

EchAMP, the evolutionarily conserved, lactation specific AMP from an oviparous mammal may find application as a broad-spectrum antimicrobial against pathogens that affect mammary gland or otherwise cause routine infections in humans and livestock.

Antimicrobial Resistance of Enterococcus Faecium Isolated from the Urinary System Of Dogs

The purpose of the present study was to determine the antimicrobial susceptibility of vancomycin-resistant and Enterococcus faecium strains isolated from urine samples of dogs. A total of 22 Enterococcus sp. samples were isolated and identified from 100 urine samples collected by cystocentesis from dogs of both sexes. The identification with species specific primers for multiplex PCR revealed that all 22 isolates (100%) belonged to E. faecium. Vancomycin resistance was found in 10 (45%) samples of E. faecium strains with PCR study by vanA and vanB primers.

The Enterococcus: a Model of Adaptability to Its Environment

The genus Enterococcus comprises a ubiquitous group of Gram-positive bacteria that are of great relevance to human health for their role as major causative agents of health care-associated infections. The enterococci are resilient and versatile species able to survive under harsh conditions, making them well adapted to the health care environment. Two species cause the majority of enterococcal infections: Enterococcus faecalis and Enterococcus faecium Both species demonstrate intrinsic resistance to common antibiotics, such as virtually all cephalosporins, aminoglycosides, clindamycin, and trimethoprim-sulfamethoxazole. Additionally, a remarkably plastic genome allows these two species to readily acquire resistance to further antibiotics, such as high-level aminoglycoside resistance, high-level ampicillin resistance, and vancomycin resistance, either through mutation or by horizontal transfer of genetic elements conferring resistance determinants.

Antimicrobial Resistance and Biofilm Formation in Enterococcus spp. Isolated from Humans and Turkeys in Poland

Enterococci are a natural component of the intestinal flora of many organisms, including humans and birds. As opportunistic pathogens, they can cause fatal infections of the urinary tract and endocarditis in humans, whereas in poultry symptoms are joint disease, sepsis, and falls in the first week of life. The study covered 107 Enterococcus strains-56 isolated from humans and 51 from turkeys. Among the isolates investigated Enterococcus faecalis was detected in 80.36% of human and 80.39% of turkey samples. Enterococcus faecium was identified in 8.93% of human and 17.65% of turkey strains. The highest percentage of the strains was resistant to tetracycline as follows: 48 (85.71%) and 48 (94.12%) of human and turkey strains, respectively. Resistance to erythromycin occurred in 37.50% of the human and in 76.47% of turkey strains, otherwise 27.10% of all strains showed resistance to ciprofloxacin. Our study revealed that 25% of human and 15.69% of turkey strains were resistant to vancomycin. Multidrug resistance showed in 32.14% and 43.14% of human and turkey strains, respectively. The tetracycline resistance gene, tetM, was detected in 82.24% of all strains analyzed, whereas the tetO gene was found in 53.57% of human but only in 7.84% of turkey strains. The vancomycin resistance gene (vanA) was detected in seven Enterococcus strains (six isolated from turkeys and one from humans). The ermB gene (resistance to macrolide) was detected in 55.14% of all isolates (42.86% of human and 68.63% of turkey strains), whereas the ermA gene was detected in 17.65% of turkey but only in 3.57% of human isolates. All the strains had the ability to form biofilms. A stronger biofilm was formed after 24-hour incubation by strains isolated from turkeys, whereas after 48 hours of incubation all examined strains produced strong biofilm.

Incidence of Virulence Determinants Among Enterococcal Clinical Isolates in Egypt and Its Association with Biofilm Formation

Background: Although Enterococci compromise an essential part of normal gut microbiota of both animals and humans, they have emerged as a leading opportunistic pathogen causing infections. The pathogenesis of enterococci is attributed to an array of virulence determinants. Objectives: This study aims to explore the prevalence and characteristics of enterococcal clinical isolates collected from Mansoura University Hospitals, Egypt, assess their ability to form biofilm, and the correlation with virulence determinants and antimicrobial resistance. Materials and Methods: A total of 70 Enterococcal clinical isolates were collected from different clinical sources between June and December 2016. Biofilm formation capacity was assessed, and characterization of virulence factors and antibiotic susceptibility was performed. Clonal relatedness between isolates was assessed using enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR) approach. Results and Conclusion: The molecular analysis demonstrated high genetic diversity among enterococcal clinical isolates. The gelE was the most frequently detected gene (91.4%), followed by asa1 (70%), esp (65.7%), and cylA (17.1%), while hyl was not detected in any isolate. Gelatinase activity was detected in 35.7%, while hemolysin and lipase activity was detected in 12.9% and 78.5%, respectively. Most of the enterococcal isolates were biofilm producers, of which 67.1% were strong/moderate biofilm producers. All linezolid-resistant isolates exhibited strong/moderate biofilm formation capacity. Strong/moderate biofilm formation was more frequently observed among esp-positive (esp+) and gelatinase nonproducing (gelatinase-) enterococcal isolates. Multiple regression analysis denoted that esp (odds ratio [OR] 5.371, p = 0.003) and gelatinase production (OR 0.264, p = 0.015) were associated with strong/moderate biofilm formation capacity. These findings suggest that esp gene positivity and gelatinase production may affect biofilm formation capacity among enterococcal clinical isolates.