Comparison of antimicrobial resistance patterns in enterococci from intensive and free range chickens in Australia

Antimicrobial susceptibility rates in gram-positive catalase-negative cocci from sheep and goat genital microbiota

Gram-positive catalase-negative cocci (GPCNCs) are significant components of the genital microbiota in sheep and goats. However, characterizing them can be difficult due to overlapping culture features and the limited information on their susceptibility to antibiotics. In this study, 97 foreskin and 13 vaginal swabs were investigated using a culturomic approach. Of 110 animals, 76 (69.09 %) hosted GPCNCs, including strains from Streptococcaceae (37, 33.64 %), Aerococcaceae (30, 27.27 %), Enterococcaceae (6, 5.45 %) and other minor species. With increasing antimicrobial resistance rates in livestock, surveillance programs are globally required, so we conducted a pilot study on GPCNCs isolated from the genital mucosa surfaces of sheep and goats using the minimal inhibitory concentration assay (MIC). Due to gaps in interpretative standard breakpoints, normalized resistance interpretation was used for setting epidemiological susceptibility cut-off values (COWTs). Of 57 suitable strains, the majority (80.71 %) showed high COWTs with decrease susceptibility to at least one antimicrobial class, with 22.81 % displaying multiresistant profiles. Of interest, combined resistances to beta-lactams, macrolides, lincosamides, and tetracyclines were detected in strains of Streptococcus plurianimalium. Further combinations, including resistance to beta-lactams, pleuromutilins, aminoglycosides, and lincosamides, were also recorded in both Streptococcus uberis and Enterococcus spp. strains. Being beta-lactams, macrolides, and tetracyclines the most used antibiotics in livestock worldwide, our results highlight the need for their prudent use. Collectively, our findings highlight that small ruminant genital microbiota can serve as reservoirs for opportunistic severe pathogens, often zoonotic, carrying multidrug resistances, thus standing for high risks for both animals and humans.

Enterococci Isolated from One-Day-Old Chickens and Their Phenotypic Susceptibility to Antimicrobials in the Czech Republic

Our study describes the prevalence and spectrum of enterococci isolated from one-day-old chickens in the Czech Republic, their level of antimicrobial resistance, and the occurrence of multiresistance. Over a 24-month period from 1 August 2021 to 31 July 2023, a total of 464 mixed samples of one-day-old chicken organs were examined during routine inspections at 12 randomly selected poultry farms in the Czech Republic. The samples were processed via cultivation methods and suspected strains were confirmed using the MALDI-TOF Mass Spectrometry method. Antimicrobial susceptibility was determined using the MIC method for eight antimicrobials. A total of 128 isolates (prevalence of 27.6%) representing 4 species of enterococci were isolated, including Enterococcus faecalis, Enterococcus faecium, Enterococcus gallinarum, and Enterococcus hirae, with prevalence rates of 23.3%, 1.5%, 2.2%, and 0.6%, respectively. Susceptibility tests showed a high percentage of susceptible strains among E. faecalis, E. faecium, and E. gallinarum for penicillin-based antibiotics, sulfamethoxazole with trimethoprim, and florfenicol (80-100% susceptible strains). E. hirae was an exception, displaying complete resistance to enrofloxacin (0% susceptible strains) and a high degree of resistance to other tested antimicrobials (33.3% susceptible strains). Among the isolated strains, a total of 16 isolates (12.5%) showed resistance to 3 or more antimicrobials. Complete resistance to all eight antimicrobials simultaneously was observed in four isolates (3.1%). This research shows the possible sources of pathogenic enterococci and their virulence and resistance genes. The findings hold relevance for both veterinary and human medicine, contributing to a better understanding of enterococcal circulation in the human ecosystem and food chain, as well as the development of their resistance and multiresistance.

Dissemination of Enterococcal Genetic Lineages: A One Health Perspective

Enterococcus spp. are commensals of the gastrointestinal tracts of humans and animals and colonize a variety of niches such as water, soil, and food. Over the last three decades, enterococci have evolved as opportunistic pathogens, being considered ESKAPE pathogens responsible for hospital-associated infections. Enterococci's ubiquitous nature, excellent adaptative capacity, and ability to acquire virulence and resistance genes make them excellent sentinel proxies for assessing the presence/spread of pathogenic and virulent clones and hazardous determinants across settings of the human-animal-environment triad, allowing for a more comprehensive analysis of the One Health continuum. This review provides an overview of enterococcal fitness and pathogenic traits; the most common clonal complexes identified in clinical, veterinary, food, and environmental sources; as well as the dissemination of pathogenic genomic traits (virulome, resistome, and mobilome) found in high-risk clones worldwide, across the One Health continuum.

Antimicrobial Resistance, Biofilm Formation, and Virulence Genes in Enterococcus Species from Small Backyard Chicken Flocks

Backyard birds are small flocks that are more common in developing countries. They are used for poultry meat and egg production. However, they are also implicated in the maintenance and transmission of several zoonotic diseases, including multidrug-resistant bacteria. Enterococci are one of the most common zoonotic bacteria. They colonize numerous body sites and cause a wide range of serious nosocomial infections in humans. Therefore, the objective of the present study was to investigate the diversity in Enterococcus spp. in healthy birds and to determine the occurrence of multidrug resistance (MDR), multi-locus sequence types, and virulence genes and biofilm formation. From March 2019 to December 2020, cloacal swabs were collected from 15 healthy backyard broiler flocks. A total of 90 enterococci strains were recovered and classified according to the 16S rRNA sequence into Enterococcus faecalis (50%); Enterococcus faecium (33.33%), Enterococcus hirae (13.33%), and Enterococcus avium (3.33%). The isolates exhibited high resistance to tetracycline (55.6%), erythromycin (31.1%), and ampicillin (30%). However, all of the isolates were susceptible to linezolid. Multidrug resistance (MDR) was identified in 30 (33.3%) isolates. The enterococci AMR-associated genes ermB, ermA, tetM, tetL, vanA, cat, and pbp5 were identified in 24 (26.6%), 11 (12.2%), 39 (43.3%), 34 (37.7%), 1 (1.1%), 4 (4.4%), and 23 (25.5%) isolates, respectively. Of the 90 enterococci, 21 (23.3%), 27 (30%), and 36 (40%) isolates showed the presence of cylA, gelE, and agg virulence-associated genes, respectively. Seventy-three (81.1%) isolates exhibited biofilm formation. A statistically significant correlation was obtained for biofilm formation versus the MAR index and MDR. Multi-locus sequence typing (MLST) identified eleven and eight different STs for E. faecalis and E. faecium, respectively. Seven different rep-family plasmid genes (rep1–2, rep3, rep5–6, rep9, and rep11) were detected in the MDR enterococci. Two-thirds (20/30; 66.6%) of the enterococci were positive for one or two rep-families. In conclusion, the results show that healthy backyard chickens could act as a reservoir for MDR and virulent Enterococcus spp. Thus, an effective antimicrobial stewardship program and further studies using a One Health approach are required to investigate the role of backyard chickens as vectors for AMR transmission to humans.

Fate of Antibiotic Resistance Genes and Changes in Bacterial Community With Increasing Breeding Scale of Layer Manure

The use of antimicrobials in intensive poultry production is becoming increasingly common because of its high throughput of meat and egg products. However, the profile of antibiotic resistance genes (ARGs) and the underlying mechanisms in different breeding scale farms were not fully explored. The study examined the profiles of ARGs in layer manure from three free-range and 12 intensive layer farms with different scales (N500, N5000, N10000, and N20000). A quantitative PCR (qPCR) array was used to quantify ARGs, and microbial community structure was analyzed by 16S rRNA gene sequencing. A total of 48 ARGs, belonging to seven major types, were identified in the layer manure samples, with sul2, tetM-01, and ermB being the predominant ones. The abundance, diversity, and mobility potential of ARGs in layer manure changed significantly with the increasing of the breeding scale. The abundances of total ARGs had significantly positive correlations with mobile genetic elements (MGEs), suggesting the mobility potential of ARGs in layer manure samples. Bacterial abundance did not show significant differences among the five group manure samples. However, bacterial diversity showed an increasing trend along the breeding scale. Pathogenic Bacteroidetes increased in the largest-scale layer manure samples and showed significant positive correlations with most ARGs. Network analysis revealed significant co-occurrence patterns between ARGs and microbial taxa, indicating ARGs had a wide range of bacterial hosts. Proteobacteria and Firmicutes were potential hosts for tetracycline and macrolide-lincosamide-streptogramin B (MLSB) resistant genes. Our results indicated that the expansion of the breeding scale of a farm promotes the abundance, diversity, and mobility potential of ARGs in layer manure.

Molecular detection and antibiotyping of multi-drug resistant Enterococcus faecium from healthy broiler chickens in Bangladesh

BACKGROUND

Enterococcus faecium is a ubiquitously distributed member of the intestinal microbiota of both humans and animals. Antibiotic resistant E. faecium are a major public health concern.

OBJECTIVES

This study aimed to detect multi-drug resistant (MDR) E. faecium and their antibiotic resistance genes from broiler chickens in Bangladesh.

METHODS

A total of 100 faecal samples of healthy broilers were screened by conventional methods and polymerase chain reaction (PCR) to detect E. faecium and their resistance genes. Disk diffusion test was employed to determine antibiotic profiles.

RESULTS

By PCR, among 100 samples, 45% [95% confidence interval (CI): 35.62%-54.76%] were positive for E. faecium. Based on antibiogram, all the E. faecium isolates were found resistant to ampicillin, and frequently (93.33%-55.56%) resistant to ceftriaxone, cefotaxime, streptomycin, erythromycin, and imipenem; moderate to lower (26.67%-4.44%) resistance to tetracycline, ciprofloxacin, norfloxacin, chloramphenicol, gentamicin, and vancomycin. Interestingly, 80% (95% CI: 66.18%-89.10%) E. faecium isolates were MDR in nature. In addition, the indices of multiple antibiotic resistance (MAR) ranged from 0.08 to 0.83. By bivariate analysis, high positive significant correlations were observed between resistance profiles of erythromycin and imipenem, ciprofloxacin and norfloxacin, erythromycin and streptomycin, ceftriaxone and cefotaxime, tetracycline and chloramphenicol, and streptomycin and imipenem. Furthermore, the prevalence of resistance genes of E. faecium was 58.33% (tetA), 33.33% (tetB), 35.56% (blaTEM ), 60% (CITM), 13.33% (aadA1), and 12% (SHV).

CONCLUSIONS

To the best of our knowledge, this is the first study in Bangladesh to detect MDR and MAR E. faecium and their associated resistance genes. The detection of MDR and MAR E. faecium and their corresponding resistance genes from healthy broilers is of public health concern because of their potential to enter into the food chain.

Resistance and virulence distribution in enterococci isolated from broilers reared in two farming systems

Background

The impact of enterococci in human health has been growing for the last decades, mainly due to their resistance to several antimicrobial agents. Human consumption of contaminated meat, especially poultry, has been identified as a possible route of transmission. The aim of the present study was to evaluate and compare the antimicrobial resistance profiles and virulence genes of enterococci isolated from Portuguese conventional and free-range broiler farms.

Results

Antibiotic susceptibility testing showed high frequencies of resistance to tetracycline in both farming systems. Resistance to erythromycin and gentamicin were detected in about half of the isolates. Resistance to penicillin was the less frequently observed and no vancomycin resistant isolates were identified. The majority of the enterococcal isolates, from either farming systems, were resistant to more than one antibiotic, and no statistical associations were found, except for penicillin resistance which associated with the genetic clusters. No differences were found between farming systems regarding the prevalence of tet(M), erm(B), aac (6′)-Ie-aph (2″)-Ia and pbp5 genes, nevertheless pbp5 prevalence was associated with the different genetic clusters. Hemolytic activity was identified in 26.47% of all isolates and gelatinase activity in 50%. The gelE gene was identified in the majority of the isolates, whereas esp and agg genes were rarely detected. The cylA determinant was not detected in any of the isolates.

Conclusions

Overall, results suggest that similar resistance patterns and virulence genes can be found in both farming systems, though enterococci in free-range conditions should be less prone to acquire further resistance genes.

Cost-Effectiveness of Black Soldier Fly Larvae Meal as Substitute of Fishmeal in Diets for Layer Chicks and Growers

The acceptance of eco-friendly black soldier fly larvae meal (BSFLM) as sustainable alternative protein ingredient in poultry feeds continues to gain momentum worldwide. This study evaluates the impact of BSFLM in layer chick and grower diets on the growth, carcass quality and economic returns. Mean weekly weight gain and total live weight per chick and grower varied significantly. The highest final weight gain was achieved when birds were provided diet with 25.6% BSFLM. Average daily feed intake (ADFI), average daily weight gain (ADG) and overall weight gain of the chick varied significantly, except for the feed conversion ratio (FCR). For grower birds, ADFI, ADG, FCR and overall weight gain did not vary significantly across the various feeding regimes. The weight of the wings and drumsticks had a quadratic response with a maximum weight obtained at 33% inclusion of BSFLM. The weight of the internal organs were not significantly affected by dietary types. Positive cost–benefit ratio and return on investment was recorded for diet types with higher BSFLM inclusion levels (>75%). Diets with 25% and 100% BSFLM inclusion were the most suitable and cost-effective, respectively. Thus, BSFLM represents a promising alternative source of protein that could be sustainably used in the poultry industries.

High-Level Resistance to Erythromycin and Tetracycline and Dissemination of Resistance Determinants among Clinical Enterococci in Iran

OBJECTIVES

The purpose of this study was to investigate the distribution pattern of genes responsible for erythromycin and tetracycline resistance and their association with resistance phenotypes in enterococcus isolates.

MATERIALS AND METHODS

Eighty-six Enterococcus faecalis and 26 E. faecium isolates were collected from 2 hospitals in Kerman, Iran. Minimum inhibitory concentration of erythromycin and tetra-cycline was determined and then genes encoding resistance to erythromycin - erm (A-C), mef, and msr - and tetracycline - tet (M), tet (O), tet (S), tet (K), and tet (L) - were investigated.

RESULTS

In all resistant isolates (n = 72, 64%), high-level resistance to both tested antibiotics was found. The most prevalent erm gene was erm (B) (77.7%), followed by erm (A) (15.2%) and erm (C) (8.3%). Genes mediating erythromycin efflux were detected in 70.8% (mef) and 9.7% (msr) of resistant isolates. Regarding tetracycline, tet (M) was detected at the highest rate (50%), followed by tet (O) (31%) and tet (S) (11%). Export of tetracycline was found in 31% (tet (K)) and 12% (tet (L)) of isolates.

CONCLUSION

A high prevalence of high-level resistance to both erythromycin and tetracycline was documented. Alterations at the ribosomal level was more frequently detected in erythromycin and tetracycline resistance than efflux systems. Concurrent resistance mechanisms were more involved in resistance to erythromycin than tetracycline.

Antimicrobial-Resistant Enterococcus faecium and Enterococcus faecalis Isolated From Healthy Thoroughbred Racehorses in Japan

In this study, the occurrence of antimicrobial-resistant (AMR) enterococci was evaluated in Thoroughbred (TB) racehorses in Japan. Fecal samples were collected from 212 healthy TB racehorses at the Miho and Ritto Training Centers of the Japan Racing Association from March 2017 to August 2018. Isolation and identification were performed by enterococcus selective medium and confirmed to the species using MALDI-TOF MS. Enterococcus faecium and E. faecalis isolates were subjected to antimicrobial susceptibility test against 11 antimicrobials by minimum inhibitory concentration based on recommendation from Clinical and Laboratory Standards Institute guidelines. Among 583 enterococcus isolates, E. faecium and E. faecalis were identified for 48.2% (281/583) and 7.4% (43/583), respectively. One isolate that was representing E. faecium (153 isolates) and E. faecalis (31 isolates) from each sample was selected for antimicrobial susceptibility test. The highest rate of resistance for E. faecium isolates was observed against enrofloxacin (57.5%; 88/153), followed by streptomycin (32.0%; 49/153), kanamycin (18.3%; 28/153), gentamycin (5.9%; 9/153), erythromycin (5.9%; 9/153), and oxytetracycline (4.6%; 7/153). For E. faecium isolates, the highest resistance was observed against streptomycin (90.3%; 28/31), followed by kanamycin (41.9%; 13/31), gentamycin (29.0%; 9/31), lincomycin (9.7%; 3/31), oxytetracycline (6.5%; 2/31), erythromycin (6.5%; 2/31), tylosin (6.5%; 2/31), enrofloxacin (6.5%; 2/31), and chloramphenicol (3.2%; 1/31). The results indicated that enrofloxacin and aminoglycosides were highly resistant among tested antimicrobials. Continuous monitoring studies are useful to increase the awareness of the potential for AMR bacteria to arise from imprudent use of antimicrobials in TB racehorses in Japan.

Antibiotic Resistance Genes in Antibiotic-Free Chicken Farms

Rising concern about the use of antibiotics in food production has resulted in many studies on the occurrence of antibiotic resistance genes (ARGs) in animal-associated bacterial communities. There are few baseline data on the abundance of ARGs on farms where chickens are intensively raised with little or no use of antibiotics. This study used a high-throughput quantitative PCR array to survey two antibiotic-free chicken farms for the occurrence of ARGs and mobile genetic elements known to enhance the spread of ARGs. No antibiotics had been used on the study farms for five years prior to this study. The results provide a baseline for the occurrence of resistance genes in the chicken production system without direct selective pressure.

Genomic, Antimicrobial Resistance, and Public Health Insights into Enterococcus spp. from Australian Chickens

Due to Australia's management of antimicrobial use in poultry, particularly the discontinued use of avoparcin for nearly 20 years, it is hypothesized that vancomycin-resistant enterococci associated with human disease are not derived from poultry isolates. This study evaluated antimicrobial resistance (AMR) of five enterococcal species isolated from Australian meat chickens, genomic features of Enterococcus faecium and Enterococcus faecalis, and the phylogenetic relationship of the poultry-derived E. faecium with isolates from human sepsis cases. All enterococcal isolates from chicken ceca were subjected to antimicrobial susceptibility testing. E. faecium and E. faecalis underwent whole-genome sequencing. E. faecium was compared at the core genome level to a collection of human isolates (n = 677) obtained from cases of sepsis over a 2-year period spanning 2015 to 2016. Overall, 205 enterococci were isolated consisting of five different species. E. faecium was the most frequently isolated species (37.6%), followed by E. durans (29.7%), E. faecalis (20%), E. hirae (12.2%), and E. gallinarum (0.5%). All isolates were susceptible to vancomycin and gentamicin, while one isolate was linezolid resistant (MIC 16 mg/liter). Core genome analysis of the E. faecium demonstrated two clades consisting predominantly of human or chicken isolates in each clade, with minimal overlap. Principal component analysis for total gene content revealed three clusters comprised of vanA-positive, vanB-positive, and both vanA- and vanB-negative E. faecium populations. The results of this study provide strong evidence that Australian chicken E. faecium isolates are unlikely to be precursor strains to the currently circulating vancomycin-resistant strains being isolated in Australian hospitals.

Antimicrobial Resistance in Enterococcus spp. of animal origin

Enterococci are natural inhabitants of the intestinal tract in humans and many animals, including food-producing and companion animals. They can easily contaminate the food and the environment, entering the food chain. Moreover, Enterococcus is an important opportunistic pathogen, especially the species E. faecalis and E. faecium, causing a wide variety of infections. This microorganism not only contains intrinsic resistance mechanisms to several antimicrobial agents, but also has the capacity to acquire new mechanisms of antimicrobial resistance. In this review we analyze the diversity of enterococcal species and their distribution in the intestinal tract of animals. Moreover, resistance mechanisms for different classes of antimicrobials of clinical relevance are reviewed, as well as the epidemiology of multidrug-resistant enterococci of animal origin, with special attention given to beta-lactams, glycopeptides, and linezolid. The emergence of new antimicrobial resistance genes in enterococci of animal origin, such as optrA and cfr, is highlighted. The molecular epidemiology and the population structure of E. faecalis and E. faecium isolates in farm and companion animals is presented. Moreover, the types of plasmids that carry the antimicrobial resistance genes in enterococci of animal origin are reviewed.

Molecular and phenotypic characterization of enterococci isolated from broiler flocks in Turkey

The aim of this study was to determine the antimicrobial resistance, resistance mechanisms implicated, and virulence genes (asa1, gelE, cylA, esp, and hyl) of Enterococcus spp. isolated from broiler flocks in Turkey. In addition, clonality of ampicillin and vancomycin-resistant enterococci was also investigated using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Out of 430 cloacal swab samples investigated, 336 (78.1%) Enterococcus spp. was isolated. The most frequently identified species were E. faecalis (87.8%), E. faecium (8.3%), E. durans (2.4%), E. casseliflavus (0.9%), and E. hirae (0.6%). The most common resistance was against tetracycline (81.3%), erythromycin (77.1%), ciprofloxacin (56.8%), and chloramphenicol (46.4%). Fifty (14.9%) isolates showed high-level gentamicin resistance (HLGL) phenotype. Ampicillin and vancomycin resistance were observed in 3.3% and 1.5% of the isolates, respectively. Two hundred eighty-three isolates were positive for the presence of virulence genes. Among the virulence genes tested, only gelE, asa1, esp, and cylA genes were detected. The most prevalent virulence gene was gelE (234, 69.6%), followed by asa1 (160, 47.6%), esp (37, 11%), and cylA (2, 0.6%). In conclusion, this study revealed that commensal enterococci from broiler flocks showed high rate of resistance to antimicrobials including clinically important antimicrobials for humans. The main underlying reason for high resistance could be attributed to the inappropriate and widespread use of antimicrobials. Therefore, there is an urgent need to develop control strategies to prevent the emergence and spread of antimicrobial resistance.

Assessment of antibiotic susceptibility in Lactobacillus isolates from chickens

BACKGROUND

The aim of this study was to determine the susceptibility of 88 Lactobacillus isolates derived from chickens to antibiotic substances and to detect drug-resistance genes.

RESULTS

The minimal inhibitory concentration of 13 antimicrobial substances was determined by the broth microdilution method, and resistance genes were detected by PCR. We recorded a high prevalence of resistance to tiamulin (90% resistant isolates), tetracyclines (74%) and lincomycin (70%), and a moderately high frequency of resistance to enrofloxacin (48%), macrolides (42%), aminoglycosides (12.5-31%), ampicillin (26%) and chloramphenicol (23%). Multi-drug resistance was observed in 79.5% of isolates. The presence of resistance genes was generally correlated with phenotypic resistance, but some molecular determinants were also recorded in susceptible isolates. Among tetracycline resistance genes, the most frequently identified was tetW (45% isolates), followed by tetM (26%) and tetL (24%). The ermB, ermC and lnuA genes, associated with resistance to macrolides and lincosamides, were observed in 39, 12 and 39% of isolates, respectively. Among genes determining resistance to aminoglycoside antibiotics, we identified ant(6)-Ia (10% of isolates), aac(6')-Ie-aph(2')-Ia (8%), aph(2″)-Ic (6%) and aadE (4.5%). The cat gene was present in 32 isolates, including 8 of 20 found to be resistant to chloramphenicol. Two genes encoding efflux pumps were identified-the acrA gene was present in all isolates tested, and 10 of 79 lactobacilli determined to be phenotypically resistant to tiamulin contained the lsaE gene. We were unable to explain the resistance mechanism of Lactobacillus isolates to ampicillin, but showed that it did not involve the production of β-lactamases.

CONCLUSIONS

Our findings indicate that intestinal lactobacilli should be considered a reservoir of resistance genes and that antibiotics must be used prudently in poultry production. The data derived from this study can be used as a basis for reviewing current microbiological breakpoints for categorization of susceptible and resistant strains within the genus Lactobacillus.

Prevalence and genetic profiling of tetracycline resistance (Tet-R) genes and transposable element (Tn916) in environmental Enterococcus species

Resistance against antimicrobial agents in enterococci is a global concern that not only challenges infection therapy but also make them reservoir of antibiotic resistance in human and animal alike. This study was conducted to establish tetracycline resistance profiles, prevalence of tet genes and transposable element (Tn916) in enterococcal soil and clinical isolates. Enterococci (n = 1210) from different environmental niche were collected and subjected to molecular identification. In total, 361 isolates showed tetracycline resistance at the breakpoint of 32 μg ml^-1. MICs (32-512 μg ml^-1) were established by both agar and micro-broth dilution methods. Soil isolates (n = 76) were further investigated for Tet genes (tet-A, C, K, L, M, S, O) and Tn916. Major resistance was observed in E. faecium 67% followed by E. faecalis 22%, E. hirae 8% and E. casseliflavus 2.6%. Results revealed that tet(L) was more frequently found in E. faecium 74.5%, while tet(M) was in high prevalence in E. faecalis 82.3%. Tn916 was detected in both clinical and soil isolates (i.e. 43.3% and 19.7%, respectively). RAPD-PCR analysis showed high diversity among the investigated isolates. Cumulatively, our results revealed high-level tetracycline resistance and the presence of multiple Tet genes and transposable element Tn916 in enterococci.

Identification and prevalence of tetracycline resistance in enterococci isolated from poultry in Ilishan, Ogun State, Nigeria

Background:

Tetracycline is one of the most frequently used antibiotics in Nigeria both for human and animal infections because of its cheapness and ready availability. The use of tetracycline in animal husbandry could lead to horizontal transfer of tet genes from poultry to human through the gut microbiota, especially enterococci. Therefore, this study is designed to identify different enterococcal species from poultry feces in selected farms in Ilishan, Ogun State, Nigeria, determine the prevalence of tetracycline resistance/genes and presence of IS256 in enterococcal strains.

Materials and Methods:

Enterococci strains were isolated from 100 fresh chicken fecal samples collected from seven local poultry farms in Ilishan, Ogun State, Nigeria. The strains were identified by partial sequencing of 16S rRNA genes. Antibiotic susceptibility of the isolates to vancomycin, erythromycin, tetracycline, gentamicin, amoxycillin/claulanate, and of loxacin were performed by disc diffusion method. Detection of tet, erm, and van genes and IS256 insertion element were done by polymerase chain reaction amplification.

Results:

Sixty enterococci spp. were identified comprising of Enterococcus faecalis 33 (55%), Enterococcus casseliflavus 21 (35%), and Enterococcus gallinarium 6 (10%). All the isolates were resistant to erythromycin (100%), followed by tetracycline (81.67%), amoxicillin/clavulanic acid (73.33%), ofloxacin (68.33%), vancomycin (65%), and gentamicin (20%). None of the enterococcal spp. harbored the van and erm genes while tet(M) was detected among 23% isolates and is distributed mostly among E. casseliflavus. IS256 elements were detected only in 33% of E. casseliflavus that were also positive for tet(M) gene.

Conclusion:

This study provides evidence that tetracycline resistance gene is present in the studied poultry farms in Ilishan, Ogun State, Nigeria and underscores the need for strict regulation on tetracycline usage in poultry farming in the studied location and consequently Nigeria.