Antimicrobial susceptibility and distribution of antimicrobial-resistance genes among Enterococcus and coagulase-negative Staphylococcus isolates recovered from poultry litter

Conditions Necessary for the Transfer of Antimicrobial Resistance in Poultry Litter

Animal manures contain a large and diverse reservoir of antimicrobial resistance (AMR) genes that could potentially spillover into the general population through transfer of AMR to antibiotic-susceptible pathogens. The ability of poultry litter microbiota to transmit AMR was examined in this study. Abundance of phenotypic AMR was assessed for litter microbiota to the antibiotics: ampicillin (Ap; 25 μg/mL), chloramphenicol (Cm; 25 μg/mL), streptomycin (Sm; 100 μg/mL), and tetracycline (Tc; 25 μg/mL). qPCR was used to estimate gene load of streptomycin-resistance and sulfonamide-resistance genes aadA1 and sul1, respectively, in the poultry litter community. AMR gene load was determined relative to total bacterial abundance using 16S rRNA qPCR. Poultry litter contained 10⁸ CFU/g, with Gram-negative enterics representing a minor population (<10⁴ CFU/g). There was high abundance of resistance to Sm (10⁶ to 10⁷ CFU/g) and Tc (10⁶ to 10⁷ CFU/g) and a sizeable antimicrobial-resistance gene load in regards to gene copies per bacterial genome (aadA1: 0.0001-0.0060 and sul1: 0.0355-0.2455). While plasmid transfer was observed from Escherichia coli R100, as an F-plasmid donor control, to the Salmonella recipient in vitro, no AMR Salmonella were detected in a poultry litter microcosm with the inclusion of E. coli R100. Confirmatory experiments showed that isolated poultry litter bacteria were not interfering with plasmid transfer in filter matings. As no R100 transfer was observed at 25 °C, conjugative plasmid pRSA was chosen for its high plasmid transfer frequency (10^-4 to 10^-5) at 25 °C. While E. coli strain background influenced the persistence of pRSA in poultry litter, no plasmid transfer to Salmonella was ever observed. Although poultry litter microbiota contains a significant AMR gene load, potential to transmit resistance is low under conditions commonly used to assess plasmid conjugation.

Biofilm-Formation Ability and the Presence of Adhesion Genes in Coagulase-Negative Staphylococci Isolates from Chicken Broilers

Simple Summary

Bacteria of the genus Staphylococcus are universally present on the mucous membranes and skin of warm-blooded animals. They are divided into two groups on the basis of their ability to clot blood plasma: the coagulase-positive (CoPS) and coagulase-negative staphylococci (CoNS). Some species can cause opportunistic infections in poultry. Identification and characterization of strains of the genus Staphylococcus isolated from farm animals are crucial in epidemiological research and for developing effective methods to treat infections and food poisoning induced by these bacteria. The main virulence factor of coagulase-negative staphylococci is considered to be their ability to form complex biofilm structures on the surfaces of damaged tissues. Biofilms increase the invasive properties of CoNS and their ability to cause infection. The purpose of this study was to determine the biofilm-forming potential of coagulase-negative Staphylococcus strains isolated from poultry. The frequency of selected genes potentially playing a role in the biofilm formation process was also determined. The results of the study indicate that the majority (79.3%) of CoNS isolated from broiler chickens in this study were capable of producing a biofilm.

Abstract

The aim of the study was to analyze the biofilm-production capacity of 87 coagulase-negative Staphylococcus strains (CoNS) isolated from broiler chickens and to determine the occurrence of biofilm-associated genes. The biofilm production capacity of staphylococci was assessed using the microtiter plate method (MTP), and the frequency of genes was determined by PCR. The ability to form a biofilm in vitro was shown in 79.3% of examined strains. Strong biofilm capacity was demonstrated in 26.4% of strains, moderate capacity in 25.3%, weak capacity in 27.6%, and a complete lack of biofilm production capacity in 20.7% of strains. The icaAB gene responsible for the production of extracellular polysaccharide adhesins was detected in 6.9% of strains. The other four genes, i.e., bap (encoding biofilm-associated protein), atlE (encoding cell surface protein exhibiting vitronectin-binding activity), fbe (encoding fibrinogen-binding protein), and eno (encoding laminin-binding protein) were detected in 5.7%, 19.5%, 8%, and 70.1% of strains, respectively. Demonstration of genes that play a role in bacterial biofilm formation may serve as a genetic basis to distinguish between symbiotic and potentially invasive coagulase-negative staphylococcal strains.

Virulence Factors in Coagulase-Negative Staphylococci

Coagulase-negative staphylococci (CoNS) have emerged as major pathogens in healthcare-associated facilities, being S. epidermidis, S. haemolyticus and, more recently, S. lugdunensis, the most clinically relevant species. Despite being less virulent than the well-studied pathogen S. aureus, the number of CoNS strains sequenced is constantly increasing and, with that, the number of virulence factors identified in those strains. In this regard, biofilm formation is considered the most important. Besides virulence factors, the presence of several antibiotic-resistance genes identified in CoNS is worrisome and makes treatment very challenging. In this review, we analyzed the different aspects involved in CoNS virulence and their impact on health and food.

The Role of the Salmonella spvB IncF Plasmid and Its Resident Entry Exclusion Gene traS on Plasmid Exclusion

Salmonella enterica cause significant illnesses worldwide. There has been a marked increase in resistance to fluoroquinolones and β-lactams/cephalosporins, antibiotics commonly used to treat salmonellosis. However, S. enterica serovars vary in their resistance to these and other antibiotics. The systemic virulence of some Salmonella serovars is due to a low copy number, IncF plasmid (65–100 kb) that contains the ADP-ribosylating toxin, SpvB. This virulence plasmid is present in only nine Salmonella serovars. It is possible that the spvB-virulence plasmid excludes other plasmids and may explain why antibiotic resistance is slow to develop in certain Salmonella serovars such as S. Enteritidis. The distribution of plasmid entry exclusion genes traS/traT and traY/excA are variable in Salmonella IncF and IncI plasmids, respectively and may account for differences in emergent antimicrobial resistance for some Salmonella serovars. The goal of this study is to determine the contribution of the Salmonella spvB-virulence plasmid in F-plasmid exclusion. From conjugation experiments, S. Typhimurium exhibited lower conjugation frequency with incFI and incFII plasmids when the spvB-virulence plasmid is present. Furthermore, introduction of cloned incFI traS into a “plasmidless” S. Typhimurium LT2 strain and Escherichia coli DH5α excluded incFI plasmid. However, deletion of the virulence plasmid traS did not affect plasmid exclusion significantly compared to a spvB control deletion. In addition, differences in F plasmid conjugation in natural Salmonella isolates did not correlate with IncF or SpvB-virulence plasmid genotype. There appear to be other plasmid or chromosomal genes at play in plasmid exclusion that may be responsible for the slow development of antibiotic resistance in certain serovars.

Antimicrobial Susceptibilities and Phylogenetic Analyses of Enterococcus hirae Isolated from Broilers with Valvular Endocarditis

Enterococcus hirae is a zoonotic Enterococcus species that causes opportunistic infections in both humans and animals and can be transmitted by contact with animals or through contaminated food. The aim of this study was to investigate the importance of E. hirae in broilers with endocarditis, as well as the antimicrobial resistance patterns and genetic relatedness of the isolates. A total of 477 three- to five-week-old broilers were studied during five fattening periods on a farm with mortality due to endocarditis. Endocarditis was observed in 27 chickens (5.66%), and samples were taken for pathological, microbiological, and molecular studies. Lesions were mainly found in the right atrioventricular valve and corresponded with a fibrinous endocarditis. Enterococcus hirae was identified in all cases. Pulsed-field gel electrophoresis results showed clonality among some isolates, with one pulsotype harboring 11 isolates that were found throughout the study. Most of the isolates showed multi-drug-resistant phenotypes. These results confirm that E. hirae is a significant cause of endocarditis in broilers, and suggest that broilers may be important carriers of antimicrobial-resistant E. hirae that might enter into the food chain.

High concentration of coagulase-negative staphylococci carriage among bioaerosols of henhouses in Central China

Background

Coagulase-negative staphylococci (CoNS) are a group of opportunistic pathogens, which are widely spread in the environment. Animal breeding is an important source of pathogen spreading. However, the concentration and characteristics of CoNS in the bioaerosols of henhouses are unclear.

Results

In this study, we showed that CoNS were significantly increased in bioaerosols of henhouses during the first 60 days, and reached 2.0 × 10⁶ CFU/m³, which account for 75.4% of total bacteria. One hundred and two CoNS isolates from bioaerosols and nasal swabs of farmers were further identified, covering seven species. Among these, 41.2% isolates were Staphylococcus sciuri, which was the predominant species, followed by S. equorum, S. saprophyticus, S. haemolyticus, S. xylosus, S. arlettae and S. gallinarum. There were high rates of resistance to oxacillin in CoNS (49.0%), which were defined as Methicillin-Resistant CoNS (MRCoNS), and 36.3% isolates contained resistance gene mecA. Bioaerosol infection models showed that, chickens exposed to aerosolized S. sciuri had significant induction of inflammatory cytokines interleukin (IL)-1β, IL-6, IL-8 and IL-10 at 5 days post-infection (dpi) in lungs and at 7 dpi in spleens.

Conclusions

We reported a high concentration of CoNS in henhouses, and S. sciuri was the preponderant CoNS species. Antibiotic resistance analysis and bioaerosols infection of CoNS further highlighted its hazards on resistance and immunological challenge. These results suggested that, CoNS in bioaerosols could be one serious factor in the henhouses for not only poultry industry but also public health.

Detection of Antibiotic Resistance and Classical Enterotoxin Genes in Coagulase -negative Staphylococci Isolated from Poultry in Poland

Introduction

The study sought to characterise antimicrobial resistance among coagulase-negative Staphylococcus (CNS) species recovered from broiler chickens and turkeys in Poland including the presence of 12 antimicrobial resistance genes and five classical genes of staphylococcal enterotoxins.

Material and Methods

A panel of 11 antimicrobial disks evaluated the phenotypic sensitivity of the tested strains to antibiotics. Five multiplex PCR assays were performed using primer pairs for specific detection of antibiotic resistance genes and staphylococcal enterotoxin A to E genes.

Results

Selected antimicrobial agent susceptibility testing revealed 100% of such in in vitro conditions to cefoxitin among strains of Staphylococcus sciuri and S. chromogenes. The blaZ (for ß-lactam) and mecA (for methicillin resistance) genes were in 58.3% and 27.5% of strains, respectively. Among genes resistant to tetracyclines, tetK was most frequent. Fewer (CNS) strains showed genes resistant to macrolides, lincosamides, and florfenicol/chloramphenicol. Multiplex PCR for classical enterotoxins (A-E) detected the see gene in two S. hominis strains, while the seb gene producing enterotoxin B was found in one strain of S. epidermidis.

Conclusion

CNS strains of Staphylococcus isolated from poultry were either phenotypically or genotypically multidrug resistant. Testing for the presence of the five classical enterotoxin genes showed that CNS strains, as in the case of S. aureus strains, can be a source of food intoxications.

Prevalence and antibiotic resistance of coagulase-negative Staphylococci isolated from poultry farms in three regions of Ghana

The use of antibiotics in animal production has been associated with the development and spread of antibiotic-resistant organisms including commensals. Coagulase-negative Staphylococcus (CoNS) species, which were until recently considered non-pathogenic, have been associated with opportunistic infections and high resistance to several antibiotics. This study sought to determine the prevalence, identity, and phenotypic resistance of coagulase-negative Staphylococcus spp. isolated from some selected poultry farms and farm workers in the Ashanti, Brong Ahafo, and Greater Accra regions of Ghana. Poultry litter samples and oral swabs of poultry farm workers were collected, from which bacterial species were isolated, identified, and analyzed. Various selective media were used for the presumptive identification of the different species. Confirmation of bacterial identity was done using matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry. Antibiotic susceptibility testing of the isolates was performed using the Kirby-Bauer disk diffusion method. Zones of growth inhibition were interpreted based on the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. Two hundred and fifty-six coagulase-negative Staphylococcus spp., comprising S. sciuri (42.97%), S. lentus (35.94%), S. gallinarum (6.64%), S. xylosus (4.30%), S. haemolyticus (3.91%), S. saprophyticus (1.95%), and S. cohnii (0.39%) were confirmed by MALDI-TOF. CoNS were isolated from samples from the Brong Ahafo (48.83%), Ashanti (33.59%), and Greater Accra (17.78%) regions. Isolates from poultry litter constituted 55.47%, and farm workers 44.53%. All the isolates were susceptible to amoxicillin/clavulanic acid and amikacin. The isolates exhibited high resistance toward tetracycline (57.03%), doxycycline (43.75%), and oxacillin (43.36%). Multi-drug resistance (MDR) was observed in 19.14% of the isolates. MDR was higher in isolates obtained from poultry farm workers (61.22%) than isolates from poultry litter (38.78%). The above findings call for stricter monitoring of antibiotic usage in both animal production and in humans.

Retail ready-to-eat food as a potential vehicle for Staphylococcus spp. harboring antibiotic resistance genes

Ready-to-eat (RTE) food, which does not need thermal processing before consumption, could be a vehicle for the spread of antibiotic-resistant microorganisms. As part of general microbiological safety checks, staphylococci are routinely enumerated in these kinds of foods. However, the presence of antibiotic-resistant staphylococci in RTE food is not routinely investigated, and data are only available from a small number of studies. The present study evaluated the pheno- and genotypical antimicrobial resistance profile of Staphylococcus spp. isolated from 858 RTE foods (cheeses, cured meats, sausages, smoked fishes, salads). Of 113 strains isolated, S. aureus was the most prevalent species, followed by S. xylosus, S. saprophyticus, and S. epidermidis. More than half (54.9%) of the isolates were resistant to at least one class of tested antibiotic; of these, 35.4% of the strains were classified as multidrug resistant. Most of the isolates were resistant to cefoxitin (49.6%), followed by clindamycin (39.3%), tigecycline (27.4%), quinupristin-dalfopristin (22.2%), rifampin (20.5%), tetracycline (17.9%), and erythromycin (8.5%). All methicillin-resistant staphylococci harbored the mecA gene. Among the isolates resistant to at least one antibiotic, 38 harbored tetracycline resistance determinant tet (M), 24 harbored tet (L), and 9 harbored tet (K). Of the isolates positive for tet (M) genes, 34.2% were positive for the Tn916-Tn1545-like integrase family gene. Our results indicated that retail RTE food could be considered an important route for the transmission of antibiotic-resistant bacteria harboring multiple antibiotic resistance genes.

Can probiotics improve the environmental microbiome and resistome of commercial poultry production?

Food animal production systems have become more consolidated and integrated, producing large, concentrated animal populations and significant amounts of fecal waste. Increasing use of manure and litter as a more "natural" and affordable source of fertilizer may be contributing to contamination of fruits and vegetables with foodborne pathogens. In addition, human and animal manure have been identified as a significant source of antibiotic resistance genes thereby serving as a disseminator of resistance to soil and waterways. Therefore, identifying methods to remediate human and animal waste is critical in developing strategies to improve food safety and minimize the dissemination of antibiotic resistant bacteria. In this study, we sought to determine whether withdrawing antibiotic growth promoters or using alternatives to antibiotics would reduce the abundance of antibiotic resistance genes or prevalence of pathogens in poultry litter. Terminal restriction fragment length polymorphism (T-RFLP) paired with high throughput sequencing was used to evaluate the bacterial community composition of litter from broiler chickens that were treated with streptogramin growth-promoting antibiotics, probiotics, or prebiotics. The prevalence of resistance genes and pathogens was determined from sequencing results or PCR screens of litter community DNA. Streptogramin antibiotic usage did not elicit statistically significant differences in Shannon diversity indices or correlation coefficients among the flocks. However, T-RFLP revealed that there were inter-farm differences in the litter composition that was independent of antibiotic usage. The litter from all farms, regardless of antibiotic usage, contained streptogramin resistance genes (vatA, vatB, and vatE), macrolide-lincosamide-streptogramin B resistance genes (ermA and ermB), the tetracycline resistance gene tetM and class 1 integrons. There was inter-farm variability in the distribution of vatA and vatE with no statistically significant differences with regards to usage. Bacterial diversity was higher in litter when probiotics or prebiotics were administered to flocks but as the litter aged, diversity decreased. No statistically significant differences were detected in the abundance of class 1 integrons where 3%-5% of the community was estimated to harbor a copy. Abundance of pathogenic Clostridium species increased in aging litter despite the treatment while the abundance of tetracycline-resistant coliforms was unaffected by treatment. However some treatments decreased the prevalence of Salmonella. These findings suggest that withdrawing antibiotics or administering alternatives to antibiotics can change the litter bacterial community and reduce the prevalence of some pathogenic bacteria, but may not immediately impact the prevalence of antibiotic resistance.

Characterization of Staphylococcus xylosus isolated from broiler chicken barn bioaerosol

In this study we isolated and characterized Staphylococcus xylosus, a coagulase-negative staphylococcal species considered as commensal and one of the prevalent staphylococcal species found in poultry bioaerosol. Isolates were obtained using air samplers and selective phenylethyl alcohol agar for gram-positive bacteria during 35-d periods at different times of the day. A total of 200 colonies were recovered and after basic biochemical tests were performed, presumptive staphylococci were subsequently identified by API Staph strips. A total of 153 (76.5%) staphylococci were found, among which 84 were S. xylosus (46 and 38 isolated inside and outside, respectively). Biofilm formation was observed in 86.9% of S. xylosus isolates, whereas 79.8% of them showed hemolytic activity. There was a strong correlation (92.5%) between biofilm formation and hemolytic activity. All 84 S. xylosus isolates were susceptible to amikacin, ampicillin/sulbactam, chloramphenicol, ciprofloxacin, gentamycin, kanamycin, linezolid, trimethoprim/sulfamethoxazole, and vancomycin. Resistance to nalidixic acid (86.9%), novobiocin (85.7%), penicillin (70.2%), lincomycin (46.4%), oxacillin (42.9%), ampicillin (27.4%), tetracycline (21.4%), erythromycin (11.9%), bacitracin (10.7%), and streptomycin (2.4%) was observed among the isolates. Resistance to tetracycline, lincomycin, erythromycin, and β-lactam antibiotics was occasionally linked to the tetK, linA, ermB, and blaZ genes, respectively. Random amplification of polymorphic DNA results showed similarity of 15 to 99% between isolates collected outside and inside the barn, indicating genetic diversity of these isolates. Our study indicates that characterization of poultry bioaerosol coagulase-negative staphylococcal species such as S. xylosus is necessary for assessing their safety status for both poultry and humans.

Multidrug-resistant coagulase-negative Staphylococci in food animals

AIMS

To study the antimicrobial resistance of coagulase-negative staphylococci (CoNS) in animals.

METHODS AND RESULTS

In the present study, a total of 87 CoNS recovered from food animals were characterized by antimicrobial susceptibility testing, resistance gene identification and conjugation. Of the seven species studied, Staphylococcus lentus, Staphylococcus sciuri, Staphylococcus xylosus and Staphylococcus haemolyticus accounted for over 96% of the isolates. In addition to β-lactam resistance (100%), high percentages of CoNS were resistant to tetracycline (67·8%), erythromycin (36·7%), clindamycin (27·5%) and quinopristin/dalfopristin (14·9%). Importantly, 47 (54%) isolates were resistant to at least three antimicrobial classes, including six CoNS resistant to six antimicrobial classes. The common genes for the above-mentioned resistance phenotypes were mec(A), tet(M), erm(A) and vga(A)(LC) , which were identified from 68·7%, 61%, 56·2% and 69·2% of the isolates, respectively. tet(M) was conjugatively transferable from 10 tetracycline-resistant CoNS to a Enterococcus strain, underlining the potential of antimicrobial resistance transfer from Staphylococcus to the commensal bacteria in human.

CONCLUSIONS

Multidrug resistance and resistance to non-β-lactam antimicrobials are common in CoNS in animals.

SIGNIFICANCE AND IMPACT OF THE STUDY

The data improve our understanding on the extent to which CoNS contribute to the dissemination of antimicrobial resistance in the food production environment.

New MLSB resistance gene erm(43) in Staphylococcus lentus

The search for a specific rRNA methylase motif led to the identification of the new macrolide, lincosamide, and streptogramin B resistance gene erm(43) in Staphylococcus lentus. An inducible resistance phenotype was demonstrated by cloning and expressing erm(43) and its regulatory region in Staphylococcus aureus. The erm(43) gene was detected in two different DNA fragments, of 6,230 bp and 1,559 bp, that were each integrated at the same location in the chromosome in several S. lentus isolates of human, dog, and chicken origin.

An ecological perspective on U.S. industrial poultry production: the role of anthropogenic ecosystems on the emergence of drug-resistant bacteria from agricultural environments

The industrialization of food animal production, specifically the widespread use of antimicrobials, not only increased pressure on microbial populations, but also changed the ecosystems in which antimicrobials and bacteria interact. In this review, we argue that industrial food animal production (IFAP) is appropriately defined as an anthropogenic ecosystem. This paper uses an ecosystem perspective to frame an examination of these changes in the context of U.S. broiler chicken production. This perspective emphasizes multiple modes by which IFAP has altered microbiomes and also suggests a means of generating hypotheses for understanding and predicting the ecological impacts of IFAP in terms of the resistome and the flow of resistance within and between microbiomes.

IS element IS16 as a molecular screening tool to identify hospital-associated strains of Enterococcus faecium

Background

Hospital strains of Enterococcus faecium could be characterized and typed by various molecular methods (MLST, AFLP, MLVA) and allocated to a distinct clonal complex known as MLST CC17. However, these techniques are laborious, time-consuming and cost-intensive. Our aim was to identify hospital E. faecium strains and differentiate them from colonizing and animal variants by a simple, inexpensive and reliable PCR-based screening assay. We describe here performance and predictive value of a single PCR detecting the insertion element, IS16, to identify hospital E. faecium isolates within a collection of 260 strains of hospital, animal and human commensal origins.

Methods

Specific primers were selected amplifying a 547-bp fragment of IS16. Presence of IS16 was determined by PCR screenings among the 260 E. faecium isolates. Distribution of IS16 was compared with a prevalence of commonly used markers for hospital strains, esp and hyl_Efm. All isolates were typed by MLST and partly by PFGE. Location of IS16 was analysed by Southern hybridization of plasmid and chromosomal DNA.

Results

IS16 was exclusively distributed only among 155 invasive strains belonging to the clonal complex of hospital-associated strains ("CC17"; 28 MLST types) and various vancomycin resistance genotypes (vanA/B/negative). The five invasive IS16-negative strains did not belong to the clonal complex of hospital-associated strains (CC17). IS16 was absent in all but three isolates from 100 livestock, food-associated and human commensal strains ("non-CC17"; 64 MLST types). The three IS16-positive human commensal isolates revealed MLST types belonging to the clonal complex of hospital-associated strains (CC17). The values predicting a hospital-associated strain ("CC17") deduced from presence and absence of IS16 was 100% and thus superior to screening for the presence of esp (66%) and/or hyl_Efm (46%). Southern hybridizations revealed chromosomal as well as plasmid localization of IS16.

Conclusions

This simple screening assay for insertion element IS16 is capable of differentiating hospital-associated from human commensal, livestock- and food-associated E. faecium strains and thus allows predicting the epidemic strengths or supposed pathogenic potential of a given E. faecium isolate identified within the nosocomial setting.

Association of Enterococcus cecorum with vertebral osteomyelitis and spondylolisthesis in broiler parent chicks

Enterococcus cecorum is the most frequently occurring enterococcal species in the intestine of chickens of over 12 weeks of age, and there are few reports on its isolation from the skeleton of broiler parent chicks. In the present study, observations on vertebral osteomyelitis and spondylolisthesis ('kinky back syndrome') showing high incidence in 8 broiler parent flocks in different parts of Hungary are summarised. Clinical signs were seen only in roosters between 5 and 13 weeks of age. Diseased birds were alert and remained sitting on their hocks with their feet slightly raised off the ground. Incidence of the disease among male birds ranged from 8% to 30% depending on flocks. Enlargement and distortion of the body of the 6th vertebra were seen as the main pathological lesions. The cavity of the spinal canal was constricted by the distorted vertebral bodies. Resorption of bone tissue and sequestrum formation, signs of increased osteoclast activity, proliferation of fibrotic tissues, infiltration with heterophils and formation of sclerotic layers were detected in the vertebral bodies. From all 24 samples collected from the vertebral lesions, Enterococcus cecorum was isolated and identified using metabolic fingerprinting as well as 16S rRNA gene sequencing. Demonstration of E. cecorum from the vertebral lesions in all examined broiler breeder roosters showing the same clinical and pathological findings in different flocks suggested the pathogenic role of this microorganism for the first time in Hungary.

Antibiotic resistant enterococci and staphylococci isolated from flies collected near confined poultry feeding operations

Use of antibiotics as feed additives in poultry production has been linked to the presence of antibiotic resistant bacteria in farm workers, consumer poultry products and the environs of confined poultry operations. There are concerns that these resistant bacteria may be transferred to communities near these operations; however, environmental pathways of exposure are not well documented. We assessed the prevalence of antibiotic resistant enterococci and staphylococci in stored poultry litter and flies collected near broiler chicken houses. Drug resistant enterococci and staphylococci were isolated from flies caught near confined poultry feeding operations in the summer of 2006. Susceptibility testing was conducted on isolates using antibiotics selected on the basis of their importance to human medicine and use in poultry production. Resistant isolates were then screened for genetic determinants of antibiotic resistance. A total of 142 enterococcal isolates and 144 staphylococcal isolates from both fly and poultry litter samples were identified. Resistance genes erm(B), erm(A), msr(C), msr(A/B) and mobile genetic elements associated with the conjugative transposon Tn916, were found in isolates recovered from both poultry litter and flies. Erm(B) was the most common resistance gene in enterococci, while erm(A) was the most common in staphylococci. We report that flies collected near broiler poultry operations may be involved in the spread of drug resistant bacteria from these operations and may increase the potential for human exposure to drug resistant bacteria.

One reservoir: redefining the community origins of antimicrobial-resistant infections

This article reviews the evidence concerning the emergence of community-acquired MRSA and highlights the relevance of reservoirs of antimicrobial resistance in humans and animals in the community environment. Although hospital use of antimicrobials has been assumed to generate the highest risk of resistance and transmission of resistant infections, the greater load of antimicrobial use is found in food animal production. The authors conclude that it is important to assess accurately and evaluate the interactions between hospital and community; improve surveillance for resistance of community origin, including agriculture; and to implement policies that prevent increases in community reservoirs of antibiotic resistance.