Clonal diversity of Staphylococcus aureus originating from the small ruminants goats and sheep

Phenotypic and Genotypic Characterization of Staphylococcus aureus Isolated from Nasal Samples of Healthy Dairy Goats in Algeria

The present study aimed to determine the phenotypic and genotypic characteristics of S. aureus isolates from the nasal swabs of goats. A total of 232 nasal samples (one per animal) were collected from goats on 13 farms located in two regions of Algeria and were analyzed for the presence of S. aureus. The detection of virulence factors was carried out using PCR. The antibiotic susceptibility of the recovered isolates was assessed using the disc diffusion method. The biofilm formation ability was assessed by the Congo red agar method and a microtiter plate assay, and the molecular characterization of isolates was carried out by spa-typing, and for selected isolates also by multilocus sequence typing (MLST). Overall, 36 out of 232 nasal swabs (15.5%) contained S. aureus, and 62 isolates were recovered. Regarding the virulence factors, at least one staphylococcal enterotoxin gene was detected in 30 (48.4%) isolates. The gene tst encoding the toxic shock syndrome toxin was detected in fifteen isolates (24.2%), but none of the isolates harbored the gene of Panton-Valentine leukocidin (lukF/S-PV). Nine different spa-types were identified, including the detection of a new one (t21230). The recovered isolates were assigned to three clonal complexes, with CC5 (51.8%) being the most common lineage. Two isolates were methicillin-resistant (MRSA) and belonged to ST5 (CC5) and to spa-types t450 and t688. Moreover, 27 (43.5%) of the S. aureus isolates were found to be slime producers in Congo red agar, and all of the recovered isolates could produce biofilms in the microtiter plate assay. Our study showed that the nares of healthy goats could be a reservoir of toxigenic and antibiotic-resistant strains of S. aureus isolates, including MRSA, which could have implications for public health.

spa Types and Staphylococcal Enterotoxin Production of Staphylococcus aureus Isolated from Wild Boar

Little is known about the structure of S. aureus population and the enterotoxin gene content in wild boar. In 1025 nasal swabs from wild boars, 121 S. aureus isolates were identified. Staphylococcal enterotoxin (SE) genes were identified in 18 isolates (14.9%). The seb gene was found in 2 S. aureus isolates, sec in 2 isolates, the see and seh genes were found in 4 and 11 isolates, respectively. The production of SEs was evaluated in bacteria grown in microbial broth. Concentration of SEB reached 2.70 µg/ml after 24 h and 4.46 µg/ml at 48 h. SEC was produced at 952.6 ng/ml after 24 h and 7.2 µg/ml at 48 h. SEE reached 124.1 ng/ml after 24 h and 191.6 ng/ml at 48 h of culture. SEH production reached 4.36 µg/ml at 24 h and 5.42 µg/ml at 48 h of culture. Thirty-nine spa types were identified among S. aureus isolates. The most prevalent spa types were t091 and t1181, followed by t4735 and t742, t3380 and t127. Twelve new spa types, i.e., t20572‒t20583 were identified. The wild boar S. aureus population was shown to contain previously identified animal/human-associated spa types and spa types not identified in humans or animals. We also indicate that wildlife animals can be a significant reservoir of see-positive S. aureus.

Production of recombinant proteins including the B-cell epitopes of autolysin A of Staphylococcus aureus isolated from clinical sheep mastitis and their potential for vaccine development

Staphylococcus aureus is the most common clinical mastitis-associated pathogen in sheep which contributes to reduced welfare of affected animals and, therefore, compromises the quality and quantity of milk production. To prevent mastitis and its spread, it is essential to guarantee adequate breeding conditions and animal health, through the adoption of good farm management practices and the application of suitable biosecurity measures. Vaccination can play a strategic role in prevention, control, and eradication of diseases. The identification of secreted and cellular antigens of the predominant sheep-CC130/ST700/t1773 lineage would assist in the design of effective vaccine against mammary infections caused by S. aureus. In the current study, we carried out a 3D structural prediction analysis with the identification of the best B cell epitopes of the whole and secreted portion of S. aureus AtlA. Fragments of atlA, containing the main predicted epitopes, were amplified, cloned, and expressed in Escherichia coli for recombinant protein production. Two selected clones produced recombinant proteins (rAtl4 and rAtl8) showing strong reactivity with a hyperimmune serum against the native AtlA and with blood sera collected from sheep with clinical S. aureus mastitis. These may represent potential candidate protein-based vaccines able to elicit a protective immune response to be evaluated by vaccination and subsequent challenge of the vaccinated sheep.

Multi-host infection and phylogenetically diverse lineages shape the recombination and gene pool dynamics of Staphylococcus aureus

BACKGROUND

Staphylococcus aureus can infect and adapt to multiple host species. However, our understanding of the genetic and evolutionary drivers of its generalist lifestyle remains inadequate. This is particularly important when considering local populations of S. aureus, where close physical proximity between bacterial lineages and between host species may facilitate frequent and repeated interactions between them. Here, we aim to elucidate the genomic differences between human- and animal-derived S. aureus from 437 isolates sampled from disease cases in the northeast region of the United States.

RESULTS

Multi-locus sequence typing revealed the existence of 75 previously recognized sequence types (ST). Our population genomic analyses revealed heterogeneity in the accessory genome content of three dominant S. aureus lineages (ST5, ST8, ST30). Genes related to antimicrobial resistance, virulence, and plasmid types were differentially distributed among isolates according to host (human versus non-human) and among the three major STs. Across the entire population, we identified a total of 1,912 recombination events that occurred in 765 genes. The frequency and impact of homologous recombination were comparable between human- and animal-derived isolates. Low-frequency STs were major donors of recombined DNA, regardless of the identity of their host. The most frequently recombined genes (clfB, aroA, sraP) function in host infection and virulence, which were also frequently shared between the rare lineages.

CONCLUSIONS

Taken together, these results show that frequent but variable patterns of recombination among co-circulating S. aureus lineages, including the low-frequency lineages, that traverse host barriers shape the structure of local gene pool and the reservoir of host-associated genetic variants. Our study provides important insights to the genetic and evolutionary factors that contribute to the ability of S. aureus to colonize and cause disease in multiple host species. Our study highlights the importance of continuous surveillance of S. aureus circulating in different ecological host niches and the need to systematically sample from them. These findings will inform development of effective measures to control S. aureus colonization, infection, and transmission across the One Health continuum.

Colonization of Extramammary Sites with Mastitis-Associated S. aureus Strains in Dairy Goats

Staphylococcus aureus (S. aureus), a major mastitis pathogen in dairy goats, is classified as a contagious pathogen. Although previous research has shown that extramammary body sites can be colonized with S. aureus, it is unknown whether these sites are reservoirs for intramammary infections. The aim of this research was to determine whether extramammary sites can be colonized with mastitis-associated S. aureus strains in dairy goats. Milk samples were collected from 207 primiparous goats and from 120 of these goats, extramammary site samples (hock, groin, nares, vulva and udder) were collected from a large commercial dairy goat herd in the Netherlands during four sampling visits. Extramammary site swabs and milk samples were (selectively) cultured and S. aureus isolates were spa genotyped. The prevalence of colonization of the extramammary sites at goat level was 51.7% and the prevalence of S. aureus intramammary infections was 7.2%. The nares were colonized most frequently (45%), while the groin area was colonized the least (2.5%). Six spa genotypes were identified in this herd and there was no significant difference in the distribution of spa genotypes between the milk or the extramammary sites (p = 0.141). Both in the extramammary sites and in the milk, spa genotypes t544 (82.3% and 53.3%) and t1236 (22.6% and 33.3%) were the dominant genotypes. These results show that in goats, extramammary sites, particularly the nares, are frequently colonized with mastitis-associated S. aureus strains. Extramammary sites may, thus, be a source of S. aureus intramammary infections that are not targeted by the intervention measures aimed at preventing transmission from infected udder glands.

Effects of management strategies during early lactation and weaning on etiological agents of ovine subclinical mastitis and antimicrobial susceptibility of milk-derived bacterial isolates

Subclinical mastitis is a common intramammary disease in sheep production systems. Expenses associated with compromised animal performance, therapeutic interventions, and decreased ewe longevity make efforts to minimize its prevalence worthwhile. The objectives of this study were to (i) quantify the prevalence of subclinical mastitis throughout lactation, (ii) evaluate the impact of bedding treatments on subclinical mastitis during early lactation, (iii) evaluate the efficacy of prophylaxis and feed restriction during weaning on subclinical mastitis cure rates, (iv) and identify levels and types of antimicrobial resistance in milk-derived bacteria. Ewe milk samples were collected at d 1, 2, and 28 post-partum, weaning, and 3-d post-weaning for bacterial identification via culture-based methods. Staphylococcus spp. and Streptococcus spp. isolates were subjected to in vitro antimicrobial susceptibility testing. The overall prevalence of subclinical mastitis defined by culture growth ranged between 22 and 66% and differences were observed between post-weaning and d 1 and 28 milk samples. Commonly isolated bacteria include coagulase-negative staphylococci (CoNS; 59%), Bacillus spp. (35%), Mannheimia haemolytica (10%), Staphylococcus aureus (8%), Streptococcus spp. (5%), and Corynebacterium spp. (5%). Early milk samples (d 1 and 2) were compared between jug bedding treatment: jugs were recently vacated, cleaned, and dusted with barn lime before adding fresh straw (CLEAN) or jugs were previously vacated and fresh straw was added atop soiled bedding (SOILED). Jug bedding treatment did not affect the prevalence of subclinical mastitis, though CoNS had greater sulfadimethoxine resistance in SOILED isolates than CLEAN isolates (P = 0.03). Three different weaning treatments were used: ewes were injected with penicillin at weaning (PENN), ewes had restricted feed access 48 h prior to and 72 h post-weaning (FAST), or a combination of these treatments (COMBO). Weaning treatment did not affect the prevalence of subclinical mastitis or cure rate from weaning to 3-d post-weaning, though all PENN and no FAST milk S. aureus isolates were resistant against tetracycline (P = 0.08). Subclinical mastitis prevalence tended to decrease from weaning to post-weaning (P = 0.08). These data show subclinical mastitis is common throughout lactation and the levels of antimicrobial resistance of bacteria isolated from ewe milk are generally low against commonly used antimicrobials.

Assessment of animal diseases caused by bacteria resistant to antimicrobials: sheep and goats

In this opinion, the antimicrobial-resistant bacteria responsible for transmissible diseases that constitute a threat to the health of sheep and goats have been assessed. The assessment has been performed following a methodology based on information collected by an extensive literature review and expert judgement. Details of the methodology used for this assessment are explained in a separate opinion. A global state of play on antimicrobial resistance in clinical isolates of Staphylococcus aureus, Escherichia coli (non-VTEC), Pseudomonas aeruginosa, Dichelobacter nodosus, Moraxella ovis, Mannheimia haemolytica, Pasteurella multocida, Mycoplasma ovipneumoniae, Mycoplasma agalactiae, Trueperella pyogenes, Streptococcus uberis, Bibersteinia trehalosi, Campylobacter fetus, Mycoplasma mycoides subsp. capri, Mycoplasma capricolum subsp. capricolum, Fusobacterium necrophorum is provided. Among those bacteria, EFSA identified E. coli with ≥ 66% certainty as being the most relevant antimicrobial-resistant bacteria in sheep and goat in the EU based on the available evidence. The animal health impact of these most relevant bacteria, as well as their eligibility for being listed and categorised within the animal health law framework will be assessed in separate scientific opinions.

Investigation of clonal diversity, virulence genes, and antibiotic resistance of Staphylococcus aureus recovered from raw cow milk in southern Xinjiang, China

Staphylococcus aureus is an important pathogen of humans and animals. The aim of this study was to characterize 71 of S. aureus isolates from raw cow milk in southern Xinjiang of China, including molecular typing, distribution of virulence genes, and antimicrobial susceptibility. The isolates belonged to 18 sequence types (STs) (including 11 novel STs) and 6 spa types which were divided into five different clonal complexes (CCs), including CC188, CC352, CC22, CC398, and CC5406. The majority of the strains was grouped into multilocus sequence typing (MLST) CC188 (n = 41), t189 (n = 40), and ST5796 (n = 17). Only 30.9, 12.7, 11.3, and 9.9% of the isolates were resistant to erythromycin, clindamycin/norfloxacin, tetracycline, and gentamicin, respectively. Nine of multidrug resistant (MDR) isolates were observed which was associated with CC398-t2876. The adhesion molecules clfa, clfb, and hlb were most frequently detected with the percentage rate of 98.6% (70/71), 98.6% (70/71), and 90.1% (64/71), respectively. The percentage rates of the staphylococcal enterotoxin genes sea, seb, sec, sed, seg, and sei in S. aureus isolates were 5.6, 19.8, 40.8, 1.4, 49.3, and 30.9%, respectively. The see, seh, and sej genes were not found. This study provides data about the occurrence of S. aureus in raw cow milk, revealing high carriage frequency, drug resistance, and population structure of S. aureus. Furthermore, this study suggests that effective hygienic measures be taken when handling dairy cows, in order to prevent spreading MDR strains to human through direct contact and/or consumption of contaminated food.

Genomic analysis of Staphylococcus aureus from the West African Dwarf (WAD) goat in Nigeria

Background

Staphylococcus aureus can colonize various host species, and human-animal interaction is a significant factor for cross-species transmission. However, data on S. aureus colonization in animals, particularly on ruminants in close contact with humans, is limited. The West African Dwarf (WAD) goat is among the earliest domesticated ruminant associated with rural dwellers and small-holder farmers in sub-Saharan Africa. This study aimed to investigate the population structure, antibiotic resistance, and virulence gene determinants of S. aureus from the WAD goat in Nigeria.

Methods

Nasal samples were obtained from the WAD goat in five markets in Osun State, South-West Nigeria. S. aureus was characterized by antibiotic susceptibility testing, detection of virulence determinants, spa typing, and multilocus sequence typing (MLST). Representative isolates were selected for whole-genome sequencing, biofilm, and cytotoxicity assay.

Results

Of the 726 nasal samples obtained from the WAD goat, 90 S. aureus (12.4%) were recovered. Overall, 86 isolates were methicillin-susceptible, and four were mecA-positive (i.e., methicillin-resistant S. aureus [MRSA]). A diverse S. aureus clonal population was observed (20 sequence types [STs] and 37 spa types), while 35% (13/37) and 40% (8/20) were new spa types and STs, respectively. Eleven MLST clonal complexes (CC) were identified (CC1, CC5, CC8, CC15, CC30, CC45, CC97, CC121, CC133, CC152, CC522). The MRSA isolates were designated as t127-ST852-CC1-SCCmec type VII, t4690-ST152-CC152-SCCmec type Vc, and t8821-ST152-CC152-SCCmec type Vc. Phylogenetic analysis revealed that 60% (54/90) of all isolates were associated with ruminant lineages (i.e., CC133, CC522). Panton-Valentine Leukocidin (PVL)-positive S. aureus was identified in CC1, CC30, CC121, and CC152. For the CC522 isolates, we illustrate their pathogenic potential by the detection of the toxic shock syndrome gene and hemolysins, as well as their strong cytotoxicity and ability to form biofilms.

Conclusions

This is the first detailed investigation on the genomic content of S. aureus from the WAD goat in Nigeria. The S. aureus population of the WAD goat consists mainly of ruminant-associated lineages (e.g., CC133, CC522), interspersed with human-associated clones, including PVL-positive MRSA CC1 and CC152.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13756-021-00987-8.

Study on bacterial pathogens through multiplex polymerase chain reaction system and their antimicrobial resistance pattern in goats presumed with fever and/or diarrhea

Background and Aim:

Goat is one of the major livestock species, plays an important role in the economy of Bangladesh. However, the outbreak of different infectious diseases in goats causes high mortality and economic losses due to lack of proper diagnosis and treatment. Conventional culture-based methods for detecting specific pathogens as confirmatory diagnosis are laborious as well as time-consuming in comparison to multiplex polymerase chain reaction (mPCR), by which multiple pathogens can be detected at a time. The present study was aimed to perform faster molecular identification of bacterial pathogens from goats presumed with fever and/or diarrhea and their antimicrobial resistance (AMR) pattern.

Materials and Methods:

A total of 200 blood samples were collected from goats at S. A. Quaderi Teaching Veterinary Hospital (SAQTVH) in Chattogram Veterinary and Animal Sciences University for the period of July 2017-April 2018. DNA was extracted and subsequently, mPCR assay was performed for the screening of several bacterial pathogens (Salmonella spp., Listeria monocytogenes, Bacillus cereus, Yersinia enterocolitica, Campylobacter jejuni, Campylobacter coli, Clostridium perfringens, Vibrio cholerae, and Staphylococcus aureus). An antimicrobial susceptibility test against ten antimicrobials for positive samples of each organism was conducted using the Kirby–Bauer Disk-Diffusion Method on selective media.

Results:

S. aureus, C. perfringens, L. monocytogenes, and Salmonella spp. were detected from collected samples and their overall prevalence was 11.5%, 3.5%, 1%, and 20.5%, respectively. The most common clinical signs were mild fever, nasal discharge, dyspnea, and coughing (39.1%) for S. aureus, diarrhea, convulsion, abdominal pain, and incoordination (57.1%) for C. perfringens, fever, protrusion of tongue, and incoordination (100%) for L. monocytogenes, and fever, anorexia, dehydration with mucous feces (36.6%) for Salmonella spp. infection in goats. AntimGentamicinicrobial diagram of S. aureus showed resistance against Cefotaxime (74%), Cefixime (65%), and Tetracycline (65%); highly sensitive against Amoxicillin (48%), Ciprofloxacin (44%), and Gentamicin (44%). On the other hand, C. perfringens showed highly resistant against Ampicillin (71%), Gentamicin (71%), sensitive against Penicillin (57%), and Cefotaxime (57%). L. monocytogenes were found to be sensitive to Penicillin (100%) and Cefixime (100%) and Salmonella spp. showed resistance to Ampicillin (78%) and Amoxicillin (59%) but sensitive to Ciprofloxacin (54%).

Conclusion:

This study identified pathogens with their specific clinical signs in goats presumed fever and/or diarrhea through mPCR with their AMR pattern in SAQTVH, Chattogram. Potential risk factors, measuring the strength of association of disease caused by these particular pathogens, were also determined. mPCR may use as an effective tool for rapid detection of pathogens in animal.

Staphylococcus aureus Isolated from Ruminants with Mastitis in Northern Greece Dairy Herds: Genetic Relatedness and Phenotypic and Genotypic Characterization

Staphylococcus aureus is the most common mastitis-related pathogen in dairy cattle, goats, and sheep worldwide. However, the population structure and genomic characteristics of mastitis-associated S. aureus in small ruminants are limited. Furthermore, the genotypic and phenotypic characteristics involved in the pathogenicity of S. aureus have been thoroughly defined, yet their association with the severity of mastitis is not fully established. Here, we performed genotyping by pulsed-field gel electrophoresis (PFGE) and spa analyses to assess the genetic diversity and relatedness of 162 S. aureus strains recovered from clinical mastitis (CM) and subclinical mastitis (SCM) cases from goats, sheep, and bovines. PFGE analysis revealed 108 distinguishable pulsotypes and 3 main clusters that comprised isolates from the three host species, while according to spa typing, 32 different spa types were identified. Genotypic analysis revealed a spreading of genetically related or indistinguishable S. aureus strains among ovine, caprine, and bovine farms of distant geographical regions. In total, 28 different staphylococcal enterotoxin (SE) gene profiles were observed, revealing a diverse range of SE genes among isolates. By evaluating the antimicrobial resistance, we found low phenotypic antimicrobial resistance among all ruminant isolates. We also performed multiple correspondence analysis, which indicated that the presence of the sec gene, biofilm production, and high autoaggregation ability are associated with CM cases.

Staphylococcal Enterotoxin Gene Cluster: Prediction of Enterotoxin (SEG and SEI) Production and of the Source of Food Poisoning on the Basis of vSaβ Typing

Besides the infection properties in human and animals, S. aureus can produce different enterotoxins in food. The enterotoxins can cause vomiting and diarrhea, often involving many people.

Currently, only 5 (SEA to SEE) out of 27 known staphylococcal enterotoxins can be analyzed using commercially available kits. Six genes (seg, sei, sem, sen, seo, and seu), encoding putative and undetectable enterotoxins, are located on the enterotoxin gene cluster (egc), which is part of the Staphylococcus aureus genomic island vSaβ. These enterotoxins have been described as likely being involved in staphylococcal food-poisoning outbreaks. The aim of the present study was to determine if whole-genome data can be used for the prediction of staphylococcal egc enterotoxin production, particularly enterotoxin G (SEG) and enterotoxin I (SEI). For this purpose, whole-genome sequences of 75 Staphylococcus aureus strains from different origins (food-poisoning outbreaks, human, and animal) were investigated by applying bioinformatics methods (phylogenetic analysis using the core genome and different alignments). SEG and SEI expression was tested in vitro using a sandwich enzyme-linked immunosorbent assay method. Strains could be allocated to 14 different vSaβ types, each type being associated with a single clonal complex (CC). In addition, the vSaβ type and CC were associated with the origin of the strain (human or cattle derived). The amount of SEG and SEI produced also correlated with the vSaβ type and the CC of a strain. The present results show promising indications that the in vitro production of SEG and SEI can be predicted based on the vSaβ type or CC of a strain.

IMPORTANCE Besides having infectious properties in human and animals, S. aureus can produce different enterotoxins in food. The enterotoxins can cause vomiting and diarrhea, often involving many people. Most of these outbreaks remain undiscovered, as detection methods for enterotoxins are only available for a few enterotoxins but not for the more recently discovered enterotoxins G (SEG) and I (SEI). In this study, we show promising results that in vitro production of SEG and SEI can be predicted based on the whole-genome sequencing data of a strain. In addition, these data could be used to find the source (human or cattle derived) of an outbreak strain, which is the key for a better understanding of the role SEG and SEI play in foodborne outbreaks caused by S. aureus.

Staphylococcus aureus From Goats Are Genetically Heterogeneous and Distinct to Bovine Ones

Staphylococcus aureus is one of the major pathogens responsible for intramammary infections in small ruminants, causing severe economic losses in dairy farms. In addition, S. aureus can contaminate milk and dairy products and produce staphylococcal enterotoxins, being responsible for staphylococcal food poisoning. Currently, data on the population structure and the virulence gene patterns of S. aureus strains isolated from goat milk is limited. Therefore, this study aimed at defining Ribosomal Spacer PCR (RS-PCR) genotypes, clonal complexes (CC), spa types, and virulence gene profiles of S. aureus isolated from goat milk samples from Lombardy region of Italy. A total of 295 S. aureus isolates from 65 goat bulk tank milk samples were genotyped by RS-PCR. spa typing and virulence gene patterns of a subgroup of 88 isolates were determined, and MLST was performed on a further subgroup of 39 isolates, representing all the spa types identified during the analysis. This study revealed 7 major genotypic clusters (CLR, CLAA, CLZ, CLAW, CLBW, CLS, and CLI), of which S. aureus CLR (19.8%) was the most common. A total of 26 different spa types were detected, the most prevalent types were t1773 (24%), t5428 (22.7%), and t2678 (12.5%). Overall, 44.3% of all isolates harbored at least one enterotoxin gene. The most prevalent was the combination of sec-sel genes (35.2%). Based on their MLST, isolates were assigned to 14 different CC, with majority grouped as CC133 (24%), CC130 (19.6%), and CC522 (19.6%). The caprine S. aureus population was depicted with a minimum spanning tree and an evolutionary analysis based on spa typing and MLST, respectively. Then, the variability of such strains was compared to that of bovine strains isolated in the same space-time span. Our results confirmed that S. aureus isolates from goats have wide genetic variability and differ from the bovine strains, supporting the idea that S. aureus from small ruminants may constitute a distinct population.

Isolation and characterization of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) from milk of dairy goats under low-input farm management in Greece

The presence of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) in raw milk is a challenge for veterinarians and public health professionals. In this study, we investigated the presence and clonality of S. aureus and MRSA in milk of individual dairy goats with subclinical mastitis reared under the low-input farming system in Greece and determined the isolates' enterotoxin gene carriage and their ability to form biofilms. S. aureus was isolated from 162 out of the 559 milk samples examined (29 %) and one isolate per S. aureus-positive sample was further characterized. S. aureus isolates were very closely related even among farms of distant geographical regions. Nine S. aureus isolates carried a functional mecA gene and were classified as MRSA. The S. aureus protein A (spa) typing in the MRSA isolates showed that four belonged to spa type t127 (44.4 %), three to t2049 (33.3 %) and two to t7947 (22.2 %). The spa type t7947 is reported for the first time in Greece. The MRSA isolates originated from two very distantly located farms, one located in the island of Skopelos and the other in Central Macedonia. Four of the MRSA isolates carried the staphylococcal enterotoxin genes sea or sec. Most of the isolates (92 % of S. aureus and 77.8 % of the MRSA) possessed moderate or weak biofilm-formation ability. Raw milk from low-input goat herds may serve as a potential vector of antimicrobial-resistant S. aureus to raw-milk consumers.

Profiles of Staphyloccocus aureus isolated from goat persistent mastitis before and after treatment with enrofloxacin

BACKGROUND

Staphylococcus aureus is one of the main causative agents of mastitis in small ruminants. Antimicrobial use is the major treatment, but there are many flaws linked to resistance, tolerance or persistence. This study aimed to verify changes in resistance, virulence and clonal profiles of S. aureus isolated from persistent mastitis goat milk before and after enrofloxacin treatment.

RESULTS

MIC increased to at least one antimicrobial in S. aureus isolates after enrofloxacin treatment compared to before. The most detected resistance genes before and after treatment were tetK, tetM, and blaZ, with more resistance genes detected after enrofloxacin treatment (p < 0.05). Occasional variations in efflux system gene detection were observed before and after treatment. Nine virulence genes (hla, fnbA, fnbB, eta, etb, sea, sec, seh, and sej) were detected at both times, and between these, the hla and eta genes were detected more in isolates after treatment. All isolates of S. aureus belonged to the same sequence type (ST) 133, except for two S. aureus isolates prior to enrofloxacin treatment which were classified as ST5 and the other as a new one, ST4966. Isolates of S. aureus 4, 8, and 100 from before and after treatment had identical pulse types, while others obtained from other animals before and after treatment were classified into distinct pulse types.

CONCLUSION

There were occasional changes in the studied profiles of S. aureus isolated before and after treatment of animals with enrofloxacin, which may have contributed to the permanence of bacteria in the mammary gland, even when using traditional treatment, resulting in persistent mastitis.

The Evolutionary Genomics of Host Specificity in Staphylococcus aureus

Staphylococcus aureus is an important human bacterial pathogen that has a cosmopolitan host range, including livestock, companion and wild animal species. Genomic and epidemiological studies show that S. aureus has jumped between host species many times over its evolutionary history. These jumps have involved the dynamic gain and loss of host-specific adaptive genes, usually located on mobile genetic elements. The same functional elements are often consistently gained in jumps into a particular species. Further sampling of diverse animal species is likely to uncover an even broader host range and greater genetic diversity of S. aureus than is already known, and understanding S. aureus host specificity in these hosts will mitigate the risks of emergent human and livestock strains.

Short communication: Diversity of staphylococci isolated from sheep mastitis in northern Algeria

Mastitis in ruminants is an important disease with major effects on both the economy and animal welfare. It is caused by major pathogens such as Staphylococcus aureus and minor pathogens such as coagulase-negative staphylococci. The objective of this study was to identify and characterize staphylococci as a cause of sheep mastitis in Algeria. In this study, 123 milk samples were collected directly from the udder of sheep suffering from clinical mastitis in 2 provinces in Algeria. Recovered isolates were identified using MALDI-TOF mass spectrometry. Virulence-associated and antimicrobial resistance genes as well as clonal complexes (CC) of S. aureus were determined using microarray-based analysis. A total of 45 staphylococci isolates were cultivated from sheep milk samples, and 28 S. aureus were identified as methicillin susceptible (62.2%). Seventeen other Staphylococcus isolates of different species were identified using MALDI-TOF mass spectrometry. Subsequent microarray analysis typed the methicillin-susceptible S. aureus to 6 CC: CC8-MSSA, CC97-MSSA, CC130/521-MSSA, CC479-MSSA, CC522-MSSA, and CC705-MSSA. The accessory gene regulator agrIII and the ruminant leukocidin genes lukF-P83 and lukM were found in all isolates of CC130/521, CC479, CC522, and CC705. The toxic shock syndrome toxin gene tst1 was detected exclusively in CC130/521. Additionally, virulence-associated genes (sea, sed, sak, hld, hlgA, edinB, and others) were detected. The presence of antibiotic resistance genes [blaZ, erm(B), and tet(K)] was detected in small numbers of staphylococci. Staphylococci possessing these genes are considered potential hazards for farm animals, farmers, and consumers. Data concerning the prevalence and diversity of staphylococci causing mastitis in sheep from Algeria are lacking. Presented results on different aspects about staphylococci in Algerian sheep populations should at least partially close that gap. However, further extensive studies covering more geographical regions are needed to assess the epidemiological risk.

Genotyping and antimicrobial resistance of Staphylococcus aureus isolates from dairy ruminants: differences in the distribution of clonal types between cattle and small ruminants

Staphylococcus aureus is part of the normal flora of animals, and represents one of the leading causes of contagious mastitis in dairy herds worldwide. Sixty-seven epidemiologically unrelated S. aureus isolates from nasal and mastitis milk samples of dairy-producing animals (32 cows, 25 sheep, and 10 goats) were characterized by antimicrobial susceptibility testing and spa typing followed by multilocus sequence typing (MLST) on representative isolates and SCCmec-typing on methicillin-resistant S. aureus (MRSA) isolates. The highest resistance was observed to penicillin (64.2%, 43/67), followed by tetracycline (23.9%, 16/67), erythromycin (22.4%, 15/67), and streptomycin (17.9%, 12/67). In general, 18 spa types (including newly identified t16958) and 13 sequence types (STs) belonging to 8 clonal complexes (CCs) were detected. The cow-associated isolates were mainly assigned to CC5 (n = 18, related to t267-ST97, t521-ST352, t527-ST97, t304-ST6, and t084-ST15), followed by CC398 (n = 6, t937-ST291), CC45 (n = 3, t230-ST45), CC88 (n = 2, t2526-ST88), CC22 (n = 2, t3680-ST22), and CC522 (n = 1, t3576-ST522). Small ruminant isolates were mostly clustered into CC522 (n = 29, related to t3576, t1534, t16958, t7308, t7311, t7305 [ST522], t1534-ST2057, and t5428-ST2079). Two isolates from cows with mastitis were found to be MRSA, exhibited a composite profile of t937-ST291-SCCmecIV. No isolates carried the PVL and mecC genes. A significant difference in clonal types of S. aureus isolates from cows in comparison with those from small ruminants was found. This study demonstrated the circulation of diverse clones of S. aureus among dairy animals in Iran, with a different clonal composition between cows and small ruminants. The current study also reports MRSA-related mastitis in dairy cows, emphasizing the need for comprehensive surveillance.

Prevalence and characteristics of methicillin-resistant staphylococci in goats on the island of Tenerife, Spain

The aim of this study was to determine the prevalence of methicillin-resistant Staphylococcus (MRS) in healthy goats on the Island of Tenerife, Spain, as well as to identify the phenotypic and genotypic characteristics of the strains found. A cross-sectional prevalence study was conducted. A total of 158 goats from 15 different farms were sampled between September 2017 and January 2018. The percentage of positive samples of methicillin-resistant Staphylococcus aureus (MRSA) was 15.8% (25/158) and that of methicillin-resistant coagulase-negative staphylococci (MRCoNS) was 6.9% (11/158). All MRSA isolates from goats belonged to one clonal group showing Multi-Locus Sequence type 398. All strains studied (n = 36) were resistant to non-carbapenem beta-lactam antibiotics and susceptible to teicoplanin, linezolid, vancomycin, rifampicin, quinupristin-dalfospristin and mupirocine. In MRSA isolates, the highest percentage of resistance obtained, besides beta-lactam non-carbapenem antibiotics, was to trimethoprim-sulphamethoxazole and, in the case of MRCoNS isolates, to phosphomycin and erythromycin. A total of 12 resistance patterns were obtained, presenting differences between patterns obtained for MRSA and MRCoNS, with 7 different patterns for MRSA and 5 for MRCoNS. We therefore consider it essential to expand the epidemiological study of these strains of animal origin, as well as to increase surveillance and control measures at all stages of the food chain.

Role of staphylococci in mastitis in sheep

Staphylococci have been isolated from various sites of the body of healthy sheep, as well as from many infections of those animals, the main one being mastitis. The objective of this review is to appraise the importance and significance of staphylococci in causing mastitis in ewes. The review includes a brief classification and taxonomy of staphylococci and describes the procedures for their isolation and identification, as well as their virulence determinants and the mechanisms of resistance to antibacterial agents. Various staphylococcal species have been implicated in staphylococcal mastitis and the characteristics of isolates are discussed with regards to potential virulence factors. Staphylococcal mastitis is explicitly described, with reference to sources of infection, the course of the disease and the relevant control measures. Finally, the potential significance of staphylococci present in ewes' milk for public health is discussed briefly.

Differences between Staphylococcus aureus lineages isolated from ovine and caprine mastitis but not between isolates from clinical or subclinical mastitis

Staphylococcus aureus is an important mastitis pathogen, causing both clinical mastitis (CM) and subclinical mastitis (SCM) in small ruminants. In general, CM has a low incidence in sheep and goats but can be very severe and costly. In contrast, subclinical mastitis (SCM) is common but is associated with less cost. For both sheep and goats, S. aureus is the main cause of CM and is associated with SCM cases with a high SCC. Recently, specific lineages of S. aureus have been identified that are associated with CM rather than SCM in dairy cows. It is unknown whether specific S. aureus lineages are associated with CM in goats and sheep. The aim of this study was to compare the clonal complex (CC), staphylococcal protein A (spa) type, leukocidin lukM-lukF' presence, and potential to produce LukMF' in vitro between CM and SCM S. aureus mastitis isolates obtained from sheep and goats. Differences between isolates from different host species were also compared. Ovine (CM, n = 12; SCM, n = 29) and caprine (CM, n = 14; SCM, n = 30) isolates were obtained from 8 sheep flocks and 8 goat herds in the Netherlands. Overall, the isolates belonged to CC133 (85%), CC398 (7%), CC425 (5%), and CC45 (2%). Seventeen spa types were found, including 6 novel types; the predominant types were t2678 (34%), t544 (18%), and t3583 (18%). Although CC133 was dominant among both sheep and goat isolates, spa type CC133/t2678 was associated with ovine isolates, whereas CC133/t544 and CC133/t3583 were found mostly in goats. The presence of lukM-lukF' among the S. aureus isolates was high (87%), especially in CC133 (96%) and CC425 (100%), but the genes were absent in CC45 and CC398. In vitro-cultured lukM-lukF'-positive isolates produced LukM (71 out of 74 positive isolates tested) in the range of 0.4 to 5.0 µg/mL. Interestingly, the goat-associated lineages CC133/t544 and CC133/t3583 produced more LukM in vitro than the sheep-associated CC133/t2678. We found no difference in LukMF' production potential between CM and SCM isolates. In sheep as well as in goats, no association was found between genotype and CM or SCM, demonstrating that the same lineages of S. aureus are responsible for both CM and SCM. These results suggest that subclinically infected animals in a herd or flock likely act as the reservoir of S. aureus causing CM. This highlights the importance of early identification and control of SCM and suggests that controlling SCM within a herd is an effective intervention to prevent CM in small ruminants.

Antibiotic Resistance Profiling, Analysis of Virulence Aspects and Molecular Genotyping of Staphylococcus aureus Isolated in Sicily, Italy

Staphylococcus aureus is the major cause of foodborne diseases worldwide. In this retrospective study, 84 S. aureus strains were characterized. The collection comprises 78 strains isolated during 1998 and 2014 from dairy products and tissue samples from livestock bred for dairy production in Sicily. One isolate was obtained from a pet (dog), one from an exotic animal (a circus elephant), and four human isolates were obtained during a severe food poisoning outbreak that occurred in Sicily in 2015. All the strains were characterized by pulsed-field gel electrophoresis (PFGE), for antibiotic resistance and presence of toxin genes. PFGE results showed 10 different pulsotypes, with three relatively frequent and three unique. The antibiotic resistance profiling showed that penicillin G (35.7%) and tetracycline (20.2%) resistance is largely spread. Most isolates contained at least one toxin gene making them a potential threat for public health. Enterotoxin sec gene was observed in 28.6% and seg in 23.8% of the strains, respectively; the human isolates were the only ones to concurrently harbor both seg and sei genes. In addition, 24 isolates were randomly selected and analyzed by multilocus sequence typing. Interestingly, the analysis showed the presence of 12 sequence types (STs), of which 6 were novel. One of them, ST700, was detected in 29% of the isolates and was found to be spread throughout Sicily. ST700 has been present in the island for almost 16 years (1998–2014) and it shows no host preference since it was isolated from different ruminant species. Four human isolates shared both the pulsotype (PT10) and the sequence type (ST9), as well as the virulence genes (seg-sei); this observation suggests that the isolates originated from a single clone, although they were obtained from two different individuals.

Prevalence and molecular characterization of Staphylococcus aureus isolated from goats in Chongqing, China

BACKGROUND

Staphylococcus aureus is an important zoonotic pathogen which not only causes significant economic loss in livestock production but also poses a potential threat to public health. Compared with bovine and swine, the information on the colonization of S. aureus in goats is very limited. To understand the prevalence and characteristics of S. aureus in goats, we used the nasal swabs collected from apparently healthy goats to isolate S. aureus, and tested their antimicrobial susceptibility, virulence gene carrying levels, and multilocus sequence typing (MLST).

RESULTS

In 74 nasal swabs of apparently healthy goats, 32 (43.24%) S. aureus strains were isolated and identified, most of which were susceptible to many antibiotics, except for trimethoprim, furazolidone, amoxicillin, lincomycin and roxithromycin, and the resistance incidence of which were 50%, 40.63%, 37.5%, 28.13%, and 21.88% respectively. All the isolates were methicillin-susceptible S. aureus (MSSA) and mecA-negative. Enterotoxin genes were found in 53.13% of the strains. Of which, sej was the most prevalent (21.88%), followed by seb, sec, and see with the same level (18.75%). The most prevalent combination were seb + see and seb + tst. None of the S. aureus isolates harbored sea, sed, seh, eta and etb. Multilocus sequence typing (MLST) revealed 6 new alleles (aroe-552, aroe-553, glpf-500, pta-440, yqil-482 and yqil-496) and 5 new sequence types (STs) (3431,3440,3444,3445 and 3461). Using eBURST, the 5 STs were assigned to clonal complex 522 (CC522) and a further CC with no predicted ancestor. Phylogenetic analysis of seven concatenated MLST alleles revealed that the 5 STs were grouped into cluster I composed of S. aureus mainly from goats and sheep.

CONCLUSION

We provide the data for prevalence of S. aureus in goats in Chongqing municipality and their characterization which will help in tracking evolution of epidemic strains and their control methods.

Staphylococcus aureus isolated from wastewater treatment plants in Tunisia: occurrence of human and animal associated lineages

The objective was to characterize Staphylococcus aureus isolated from two wastewater treatment plants (WWTPs) located in Tunis City (Tunisia), during the period 2014-2015. Genetic lineages, antibiotic resistance mechanisms and virulence factors were determined for the recovered isolates. S. aureus isolates were recovered from 12 of the 62 wastewater samples tested (19.35%), and one isolate/sample was characterized, all of them being methicillin-susceptible (MSSA). Six spa types (t587, t674, t224, t127, t701 and t1534) were found among the 12 isolates, and the spa-t587, associated with the new sequence type ST3245, was the most predominant one (7 isolates). The remaining isolates were assigned to five clonal complexes (CC5, CC97, CC1, CC6 and CC522) according to the sequence-type determined and/or the spa-type detected. S. aureus isolates were ascribed to agrI (n = 3), agrII (n = 7) and agrIII (n = 1); however, one isolate was non-typeable. S. aureus showed resistance to (number of isolates): penicillin (12), erythromycin (7), tetracycline (one) and clindamycin (one). Among the virulence factors investigated, only one isolate harboured the tst gene, encoding the TSST-1 (toxic shock syndrome toxin 1). Despite the low number of studied isolates, the present study reports the occurrence of both human- and animal-associated S. aureus clonal complexes in WWTPs in Tunisia.

Molecular Epidemiology of Methicillin-Resistant and Methicillin-Susceptible Staphylococcus aureus in the Ovine Dairy Chain and in Farm-Related Humans

Staphylococcus aureus is a major cause of clinical infections in humans and its enterotoxins cause foodborne disease. In the present study, we tested a total of 51 isolates of S. aureus from small-ruminant dairy farms with artisan dairy facilities, all located in Latium, Italy. The farms have a known history of a high prevalence of methicillin-resistant S. aureus (MRSA). Most of the MRSA isolates (27 of 51) belonged to spa-type t127 (43.1%), followed by t2678 (3.9%), t044 (2%), t1166 (2%), and t1773 (2%). PFGE performed on mecA positive strains identified one cluster (≥ 80% of similarity), comprising 22 MRSA. Nine of twenty-two MRSA isolates were assigned human host origin, and 13 isolates did not belong to a specific host. During the characterization study, one strain isolated from bulk tank milk samples harbored the pvl gene; the strain was not enterotoxigenic with a non-specific host according to the biotyping scheme, highlighting the possible emerging risk of transmission of bacterial virulence factors by foods, the environment, and foodhandlers. These findings stress the importance of hygienic measures at all processing steps of the food production chain and underline that monitoring for the presence of MRSA throughout the food chain is essential for public health.

Antimicrobial susceptibility and genotyping of Staphylococcus aureus isolates collected between 1986 and 2015 from ovine mastitis

In this research, 330 Staphylococcus aureus isolates, collected in Sardinia (Italy) in the period 1986-2015 from clinical ovine mastitis and used for the preparation of inactivated autogenous vaccines, were analyzed. Susceptibility to 12 antimicrobial agents was tested by disk diffusion, according to CLSI recommendations. Resistance genes were detected by PCR assays. The most of isolates (85.2%) were susceptible to all antimicrobials tested, suggesting that did not exist change of resistance over time. Two isolates were multidrug-resistant (MDR), one of them (isolate 1496) showed resistance to seven antibiotics including oxacillin and erythromycin. This MRSA harboured SCCmec type IV and the erm(C) gene. Isolates were characterized by spa typing and MLST. Isolates belonged to 29 spa types: t1773 (n=186), t2678 (n=53), t7754 (n=14), t1532 (n=5), t524 (n=5) and t6060 (n=4) were the most frequent spa types found in Sardinia. The majority of ovine isolates (t1773, t7754 and t1532) was grouped in MLST CC130 (n=205) followed by CC133 (n=57). MRSA 1496 was classified as t3896, ST1 and CC1, a clonal complex common in human and also reported in cattle and pig. This study suggests that the CC130/ST700/t1773 is the prevalent S. aureus lineage associated with ovine mastitis in Sardinia.

Genetic characterization of Staphylococcus aureus isolated from nasal samples of healthy ewes in Tunisia. High prevalence of CC130 and CC522 lineages

Staphylococcus aureus is a versatile bacterium, which can infect or colonize a variety of host species. The objective of this study was to characterize S. aureus isolates recovered from nasal swabs of 167 healthy ewes sampled from 12 farms in different areas of Tunisia during the period of 2014-2015. Genetic lineages, virulence factors and antibiotic resistance mechanisms were determined for recovered isolates. S. aureus was detected in 45 out of 167 tested samples (26.9%). All isolates were methicillin-susceptible (MSSA) and the majority of them were susceptible to tested antibiotics with few exceptions (% of resistance): penicillin (8.8), ciprofloxacin (4.4), and tobramycin or tetracycline (2.2, each). Twelve different spa types were detected (t15098, t15099, t1773, t3576, t1534, t5428, t3750, t5970 t254, t2883, t127 and t933), two of them were new (t15098 and t15099). S. aureus isolates were ascribed to agrI (n=23), agrII (n=1) and agrIII (n=20), and one was non-typeable. According to the sequence-type (ST) determined and/or the spa-type detected, the 45S. aureus isolates were assigned to six clonal complexes, with CC522 (44.4%) and CC130 (37.7%) being the most common lineages. Twenty-one (46.6%) and two (4.2%) isolates harbored the tst and eta genes encoding TSST-1 and ETA, respectively. In conclusion, nares of healthy ewes could be a reservoir of MSSA CC522 and CC130, lineages associated with TSST-1 and ETA that might represent a risk to human health.

Differences in sheep and goats milk microbiological profile between conventional and organic farming systems in Greece

The aim of this study was to examine differences in the microbiological profile and antimicrobial resistance of bacteria isolated from milk from organic and conventional sheep and goat farms. Twenty-five organic and 25 conventional sheep and goat farms in the region of Thessaly, Greece participated in this study. A standardised detailed questionnaire was used to describe farming practices. A total of 50 samples were collected and analysed for total viable count (TVC), total coliform count (TCC) and somatic cell count (SCC), while Staphylococcus aureus and Escherichia coli were isolated using standard methods. Isolates were identified at species level by Api-test and Matrix-Assisted Laser Desorption/Ionisation-Time of Flight Mass Spectrometry (MALDI-TOF MS). Susceptibility to a panel of 20 for E. coli and 16 for S. aureus antimicrobials was determined by the agar dilution method. Pulsed Field Gel Electrophoresis (PFGE) was performed for S. aureus and E. coli isolates to determine predominant clones. Lower counts of TVC, TCC and SCC were identified in milk from the organic farms, possibly due to differences in the hygienic farming practices found on those farms. API-tests and MALDI-TOF MS showed no significant differences in the S. aureus and E. coli isolates. Overall, antimicrobial resistance rates were low, while a statistically higher percentage was estimated among strains originating from conventional farms in comparison with organic farms, possibly due to the restriction of antibiotic use in organic farming. PFGE revealed diversity among S. aureus and E. coli populations in both organic and conventional farms indicating circulation of 2-3 main clones changing slightly during their evolution. Consequently, there is evidence that milk from the organic farms presents a better microbiological profile when compared with milk from conventional farms.

Molecular characterization of Staphylococcus aureus from nasal samples of healthy farm animals and pets in Tunisia

A total of 261 healthy farm and pet animals (75 cattle, 52 goats, 100 dogs, and 34 cats) from different regions of Tunisia were screened for Staphylococcus aureus nasal carriage. Molecular typing of isolates (by spa- and multilocus sequence-typing) was performed, and their antimicrobial resistance and virulence genotypes were determined by PCR and sequencing. S. aureus isolates were detected in 17 of 261 tested samples (6.5%). All S. aureus isolates recovered were methicillin-susceptible (MSSA), and one isolate/sample was further studied. Eight different spa types were detected (t189, t279, t582, t701, t1166, t1268, t1534, and t1773), and eight different sequence types were identified (ST6, ST15, ST45, ST133, ST188, ST700 [clonal complex CC130], ST2057, and a new ST2121). MSSA from pets (six isolates) showed resistance to (number of isolates, resistance gene): penicillin (six, blaZ), tetracycline (one, tet[M]), erythromycin one, erm[A]), streptomycin (one, ant[6]-Ia), and ciprofloxacin (one). All isolates from farm animals showed susceptibility to the tested antimicrobials, except for two penicillin-resistant isolates. Five S. aureus isolates from goats and cats harbored the lukF/lukS-PV genes, encoding the Panton-Valentine leukocidin, and six isolates from goats harbored the tst virulence gene. In addition, diverse combinations of enterotoxin genes were detected, including two variants of the egc cluster. Goats and cats could represent a reservoir of important toxin genes, with potential implications in animal and human health.

Methicillin-resistant and methicillin-susceptible Staphylococcus aureus in dairy sheep and in-contact humans: An intra-farm study

Staphylococcus aureus is involved in a wide variety of diseases in humans and animals, and it is considered one of the most significant etiological agents of intramammary infection in dairy ruminants, causing both clinical and subclinical infections. In this study, the intra-farm prevalence and circulation of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) were investigated on an Italian dairy sheep farm previously identified as MRSA-positive by testing bulk tank milk (first isolation in 2012). Human samples (nasal swabs, hand skin samples, and oropharyngeal swabs) from 3 persons working in close contact with the animals were also collected, and the genetic characteristics and relatedness of the MRSA isolates from human and animal sources within the farm were investigated. After 2yr from the first isolation, we confirmed the presence of the same multidrug-resistant strain of MRSA sequence type (ST)1, clonal complex (CC)1, spa type t127, staphylococcal cassette chromosome mec (SCCmec) type IVa, showing identical pulsed field gel electrophoresis (PFGE) and resistance profiles at the farm level in bulk tank milk. Methicillin-resistant S. aureus isolates were detected in 2 out of 556 (0.34%) individual milk samples, whereas MSSA isolates were detected in 10 samples (1.8%). The MRSA were further isolated from udder skin samples from the 2 animals that were MRSA-positive in milk and in 2 of the 3 examined farm personnel. All MRSA isolates from both ovine and human samples belonged to ST(CC)1, spa type t127, SCCmec type IVa, with some isolates from animals harboring genes considered markers of human adaptation. In contrast, all MSSA isolates belonged to ruminant-associated CC130, ST700, spa type t528. Analysis by PFGE performed on selected MRSA isolates of human and animal origin identified 2 closely related (96.3% similarity) pulsotypes, displaying only minimal differences in gene profiles (e.g., presence of the immune evasion cluster genes). Although we observed low MRSA intra-farm prevalence, our findings highlight the importance of considering the possible zoonotic potential of CC1 livestock-associated MRSA, in view of the ability to persist over years at the farm level. Biosecurity measures and good hygiene practices could be useful to prevent MRSA spread at the farm level and to minimize exposure in the community and in categories related to farm animal industry (e.g., veterinarians, farmers, and farm workers).

Staphylococcus aureus Isolates from Goat and Sheep Milk Seem to Be Closely Related and Differ from Isolates Detected from Bovine Milk

Dairy goat and sheep farms suffer severe economic losses due to intramammary infections, with Staphylococcus aureus representing the main cause of clinical mastitis in small ruminants. In addition, S. aureus contamination of goat and sheep milk may cause staphylococcal food poisoning, as many traditional caprine and ovine milk products are not subjected to pasteurization. Data on virulence and antimicrobial resistance genes, as well as on the clonality of S. aureus detected in goat and sheep milk is scarce. Therefore, it was the aim of this study to determine (i) spa types and clonal complexes (CC) and (ii) virulence and resistance gene profiles of S. aureus isolated from goat and sheep milk. A total of 162 milk samples from sheep and goats presenting signs of an intramammary infection and 104 bulk milk samples were collected. While low prevalence rates of S. aureus was detected on single animal level, 46% of the bulk tank milk samples from small ruminants were positive for S. aureus. All isolates were spa typed and CC and virulence and resistance gene patterns were determined using a DNA microarray. Data from 49 S. aureus isolates was included in the statistical analysis and the construction of a SplitsTree. The analyzed isolates could be assigned to eleven CC, with the large majority of goat and sheep isolates being assigned to CC130 and CC133. The findings of this study suggest that S. aureus shows pronounced adaptation to small ruminants in general, but not to sheep or goats in particular. Although some common characteristics among S. aureus from caprine, ovine, and bovine milk samples were observed, S. aureus from small ruminants seem to form a distinct population. As 67% of the detected S. aureus strains exhibited at least one enterotoxin gene, many caprine, or ovine raw milk products may be contaminated with low levels of enterotoxigenic S. aureus, stressing the importance of strict maintenance of the cold chain.

Staphylococcus aureus in Animals and Food: Methicillin Resistance, Prevalence and Population Structure. A Review in the African Continent

The interest about Staphylococcus aureus (S. aureus) and methicillin resistant S. aureus (MRSA) in livestock, and domestic and wild animals has significantly increased. The spread of different clonal complexes related to livestock animals, mainly CC398, and the recent description of the new mecC gene, make it necessary to know more about the epidemiology and population structure of this microorganism all over the world. Nowadays, there are several descriptions about the presence of S. aureus and/or MRSA in different animal species (dogs, sheep, donkeys, bats, pigs, and monkeys), and in food of animal origin in African countries. In this continent, there is a high diversity of ethnicities, cultures or religions, as well as a high number of wild animal species and close contact between humans and animals, which can have a relevant impact in the epidemiology of this microorganism. This review shows that some clonal lineages associated with humans (CC1, CC15, CC72, CC80, CC101, and CC152) and animals (CC398, CC130 and CC133) are present in this continent in animal isolates, although the mecC gene has not been detected yet. However, available studies are limited to a few countries, very often with incomplete information, and many more studies are necessary to cover a larger number of African countries.

Bovine Staphylococcus aureus: Subtyping, evolution, and zoonotic transfer

Staphylococcus aureus is globally one of the most important pathogens causing contagious mastitis in cattle. Previous studies using ribosomal spacer (RS)-PCR, however, demonstrated in Swiss cows that Staph. aureus isolated from bovine intramammary infections are genetically heterogeneous, with Staph. aureus genotype B (GTB) and GTC being the most prominent genotypes. Furthermore, Staph. aureus GTB was found to be contagious, whereas Staph. aureus GTC and all the remaining genotypes were involved in individual cow disease. In addition to RS-PCR, other methods for subtyping Staph. aureus are known, including spa typing and multilocus sequence typing (MLST). They are based on sequencing the spa and various housekeeping genes, respectively. The aim of the present study was to compare the 3 analytic methods using 456 strains of Staph. aureus isolated from milk of bovine intramammary infections and bulk tanks obtained from 12 European countries. Furthermore, the phylogeny of animal Staph. aureus was inferred and the zoonotic transfer of Staph. aureus between cattle and humans was studied. The analyzed strains could be grouped into 6 genotypic clusters, with CLB, CLC, and CLR being the most prominent ones. Comparing the 3 subtyping methods, RS-PCR showed the highest resolution, followed by spa typing and MLST. We found associations among the methods but in many cases they were unsatisfactory except for CLB and CLC. Cluster CLB was positive for clonal complex (CC)8 in 99% of the cases and typically positive for t2953; it is the cattle-adapted form of CC8. Cluster CLC was always positive for tbl 2645 and typically positive for CC705. For CLR and the remaining subtypes, links among the 3 methods were generally poor. Bovine Staph. aureus is highly clonal and a few clones predominate. Animal Staph. aureus always evolve from human strains, such that every human strain may be the ancestor of a novel animal-adapted strain. The zoonotic transfer of IMI- and milk-associated strains of Staph. aureus between cattle and humans seems to be very limited and different hosts are not considered as a source for mutual, spontaneous infections. Spillover events, however, may happen.

Livestock-Associated MRSA: The Impact on Humans

During the past 25 years an increase in the prevalence of methicillin-resistant Staphylococcus aureus (HA-MRSA) was recorded worldwide. Additionally, MRSA infections may occur outside and independent of hospitals, caused by community associated MRSA (CA-MRSA). In Germany, we found that at least 10% of these sporadic infections are due to livestock-associated MRSA (LA-MRSA), which is initially associated with livestock. The majority of these MRSA cases are attributed to clonal complex CC398. LA-MRSA CC398 colonizes the animals asymptomatically in about half of conventional pig farms. For about 77%-86% of humans with occupational exposure to pigs, nasal carriage has been reported; it can be lost when exposure is interrupted. Among family members living at the same farms, only 4%-5% are colonized. Spread beyond this group of people is less frequent. The prevalence of LA-MRSA in livestock seems to be influenced by farm size, farming systems, usage of disinfectants, and in-feed zinc. LA-MRSA CC398 is able to cause the same kind of infections in humans as S. aureus and MRSA in general. It can be introduced to hospitals and cause nosocomial infections such as postoperative surgical site infections, ventilator associated pneumonia, septicemia, and infections after joint replacement. For this reason, screening for MRSA colonization at hospital admittance is recommended for farmers and veterinarians with livestock contacts. Intrahospital dissemination, typical for HA-MRSA in the absence of sufficient hygiene, has only rarely been observed for LA-MRSA to date. The proportion of LA-MRSA among all MRSA from nosocomial infections is about 3% across Germany. In geographical areas with a comparatively high density of conventional farms, LA-MRSA accounts for up to 10% of MRSA from septicemia and 15% of MRSA from wound infections. As known from comparative genome analysis, LA-MRSA has evolved from human-adapted methicillin-susceptible S. aureus, and the jump to livestock was obviously associated with several genetic changes. Reversion of the genetic changes and readaptation to humans bears a potential health risk and requires tight surveillance. Although most LA-MRSA (>80%) is resistant to several antibiotics, there are still sufficient treatment options.

Further evidence for staphylococcal food poisoning outbreaks caused by egc-encoded enterotoxins

Staphylococcal food poisoning represents the most prevalent foodborne intoxication worldwide. It is caused by oral intake of enterotoxins preformed by Staphylococcus aureus in food. The relevance of newly described enterotoxins in outbreaks of staphylococcal food poisoning is controversially discussed. Although the staphylococcal enterotoxins SEG, SEI, SEM, SEN, and SEO elicit emesis in a monkey feeding assay, there has been no conclusive proof of their emetic activity in humans. In this study, we provide further evidence suggesting that one of these enterotoxins or a combination of SEG, SEI, SEM, SEN, and SEO cause staphylococcal food poisoning. We investigated two outbreaks registered with the Swiss Federal Office of Public Health, in which only Staphylococcus aureus strains harboring the egc cluster, including seg, sei, sem, sen, and seo linked to typical signs of staphylococcal food poisoning were isolated. The outbreaks were caused by consumption of raw goat cheese and semi-hard goat cheese, and were linked to strains assigned to CC45 (agr type I) and CC9 (agr type II), respectively. These outbreaks provide further evidence that newly-described staphylococcal enterotoxins are likely to cause staphylococcal food poisoning in humans.

Staphylococcus aureus from 152 cases of bovine, ovine and caprine mastitis investigated by Multiple-locus variable number of tandem repeat analysis (MLVA)

Staphylococcus aureus is one of the main etiological agents of mastitis in ruminants. In the present retrospective study, we evaluated the potential interest of a previously described automated multiple loci Variable Number of Tandem Repeats (VNTR) Assay (MLVA) comprising 16 loci as a first line tool to investigate the population structure of S. aureus from mastitis. We determined the genetic diversity of S. aureus strains from cases of clinical and subclinical mastitis in dairy cattle (n = 118, of which 16 were methicillin-resistant), sheep (n = 18) and goats (n = 16). The 152 strains could be subdivided into 115 MLVA genotypes (including 14 genotypes for the ovine strains and 15 genotypes for the caprine strains). This corresponds to a discriminatory index (D) value of 0.9936. Comparison with published MLVA data obtained using the same protocol applied to strains from diverse human and animal origins revealed a low number (8.5%) of human-related MLVA genotypes among the present collection. Eighteen percent of the S. aureus mastitis collection belonged to clonal complexes apparently not associated with other pathological conditions. Some of them displayed a relatively low level of diversity in agreement with a restricted ecological niche. These findings provide arguments suggesting that specific S. aureus lineages particularly adapted to ruminant mammary glands have emerged and that MLVA is a convenient tool to provide a broad overview of the population, owing to the availability via internet of databases compiling published MLVA genotypes.

Carriage of Staphylococcus aureus by free-living wild animals in Spain

The presence of methicillin-susceptible Staphylococcus aureus (MSSA) was analyzed in different free-living wild animals to assess the genetic diversity and predominant genotypes on each animal species. Samples were taken from the skin and/or nares, and isolates were characterized by spa typing, multilocus sequence typing (MLST) and antimicrobial susceptibility testing. The proportion of MSSA carriers were 5.00, 22.93, 19.78, and 17.67% in Eurasian griffon vulture, Iberian ibex, red deer, and wild boar, respectively (P = 0.057). A higher proportion of isolates (P = 0.000) were recovered from nasal samples (78.51%) than skin samples (21.49%), but the 9.26% of red deer and 18.25% of wild boar would have been undetected if only nasal samples had been tested. Sixty-three different spa types were identified, including 25 new spa types. The most common were t528 (43.59%) in Iberian ibex, t548 and t11212 (15.79% and 14.04%) in red deer, and t3750 (36.11%) in wild boar. By MLST, 27 STs were detected, of which 12 had not been described previously. The most frequent were ST581 for Iberian ibex (48.72%), ST425 for red deer (29.82%), and ST2328 for wild boar (42.36%). Isolates from Eurasian griffon vulture belong to ST133. Host specificity has been observed for the most frequent spa types and STs (P = 0.000). The highest resistance percentage was found against benzylpenicillin (average, 22.2%), although most of the S. aureus isolates were susceptible to all antimicrobial tested. Basically, MSSA isolates were different from those MRSA isolates previously detected in the same animal species.

A shared population of epidemic methicillin-resistant Staphylococcus aureus 15 circulates in humans and companion animals

Methicillin-resistant Staphylococcus aureus (MRSA) is a global human health problem causing infections in both hospitals and the community. Companion animals, such as cats, dogs, and horses, are also frequently colonized by MRSA and can become infected. We sequenced the genomes of 46 multilocus sequence type (ST) 22 MRSA isolates from cats and dogs in the United Kingdom and compared these to an extensive population framework of human isolates from the same lineage. Phylogenomic analyses showed that all companion animal isolates were interspersed throughout the epidemic MRSA-15 (EMRSA-15) pandemic clade and clustered with human isolates from the United Kingdom, with human isolates basal to those from companion animals, suggesting a human source for isolates infecting companion animals. A number of isolates from the same veterinary hospital clustered together, suggesting that as in human hospitals, EMRSA-15 isolates are readily transmitted in the veterinary hospital setting. Genome-wide association analysis did not identify any host-specific single nucleotide polymorphisms (SNPs) or virulence factors. However, isolates from companion animals were significantly less likely to harbor a plasmid encoding erythromycin resistance. When this plasmid was present in animal-associated isolates, it was more likely to contain mutations mediating resistance to clindamycin. This finding is consistent with the low levels of erythromycin and high levels of clindamycin used in veterinary medicine in the United Kingdom. This study furthers the “one health” view of infectious diseases that the pathogen pool of human and animal populations are intrinsically linked and provides evidence that antibiotic usage in animal medicine is shaping the population of a major human pathogen.

Methicillin-resistant Staphylococcus aureus (MRSA) is major problem in human medicine. Companion animals, such as cats, dogs, and horses, can also become colonized and infected by MRSA. Here, we demonstrate that a shared population of an important and globally disseminated lineage of MRSA can infect both humans and companion animals without undergoing host adaptation. This suggests that companion animals might act as a reservoir for human infections. We also show that the isolates from companion animals have differences in the presence of certain antibiotic resistance genes. This study furthers the “one health” view of infectious diseases by demonstrating that the pool of MRSA isolates in the human and animal populations are shared and highlights how different antibiotic usage patterns between human and veterinary medicine can shape the population of bacterial pathogens.

Effective application of multiple locus variable number of tandem repeats analysis to tracing Staphylococcus aureus in food-processing environment

A total of 256 isolates of Staphylococcus aureus were isolated from 98 samples (34 swabs and 64 food samples) obtained from small or medium meat- and cheese-processing plants in Slovakia. The strains were genotypically characterized by multiple locus variable number of tandem repeats analysis (MLVA), involving multiplex polymerase chain reaction (PCR) with subsequent separation of the amplified DNA fragments by an automated flow-through gel electrophoresis. With the panel of isolates, MLVA produced 31 profile types, which was a sufficient discrimination to facilitate the description of spatial and temporal aspects of contamination. Further data on MLVA discrimination were obtained by typing a subpanel of strains by multiple locus sequence typing (MLST). MLVA coupled to automated electrophoresis proved to be an effective, comparatively fast and inexpensive method for tracing S. aureus contamination of food-processing factories.

SIGNIFICANCE AND IMPACT OF THE STUDY

Subspecies genotyping of microbial contaminants in food-processing factories may facilitate identification of spatial and temporal aspects of the contamination. This may help to properly manage the process hygiene. With S. aureus, multiple locus variable number of tandem repeats analysis (MLVA) proved to be an effective method for the purpose, being sufficiently discriminative, yet comparatively fast and inexpensive. The application of automated flow-through gel electrophoresis to separation of DNA fragments produced by multiplex PCR helped to improve the accuracy and speed of the method.

The emergence of mecC methicillin-resistant Staphylococcus aureus

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A novel mecA homologue, mecC, confers methicillin resistance to methicillin-resistant Staphylococcus aureus (MRSA).

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mecC MRSA produce negative results with common diagnostic tools.

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Reported from throughout Western Europe. Recent increase in Denmark.

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Found in a range of host species and may pose a zoonotic risk to humans.

The report of methicillin-resistant Staphylococcus aureus (MRSA) encoding a divergent mecA gene in 2011 was highly significant. This homologue, designated mecC, poses diagnostic problems with the potential to be misdiagnosed as methicillin-sensitive S. aureus, with important potential consequences for individual patients and for the surveillance of MRSA. mecC MRSA have now been reported from 13 European countries and have been isolated from 14 different host species, with evidence of a recent increase in Denmark. The emergence of mecC MRSA is a topic of interest to human and veterinary microbiology, and we consider it timely to review here its discovery and subsequent investigation.

Differences in virulence genes and genome patterns of mastitis-associated Staphylococcus aureus among goat, cow, and human isolates in Taiwan

A total of 117 mastitis-associated Staphylococcus aureus isolates from cow, goat, and human patients were analyzed for differences in antibiotic susceptibility, virulence genes, and genotypes using accessory gene regulator (agr) typing, pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Multidrug-resistant (MDR) S. aureus were commonly found in all sources, though they were predominantly found in human and goat isolates. Almost 70% of the isolates were resistant to ampicillin and penicillin. Host-associated virulence genes were identified as follows: tst, a gene encoding toxic shock syndrome toxin, was found in goat isolates; lukED and lukM, genes encoding leukocidin, found in cow isolates; lukPV, a gene encoding leukocidin, found in human isolates; and eta, a gene encoding for exfoliative toxin, found in both human and cow isolates. All four types of hemolysin, α, β, γ, and δ, were identified in human isolates, three types (α, γ, and δ), were identified in cow isolates, and two types (α and δ) were identified in goat isolates. Agr-typing determined agr1 to be the main subtype in human and cow isolates. PFGE and MLST analysis revealed the presence of diverse genotypes among the three sources. In conclusion, mastitis-associated, genetically diverse strains of MDR S. aureus differed in virulence genes among human, cow, and goat isolates.

Global distribution and diversity of ovine-associated Staphylococcus aureus

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97 global ovine S. aureus isolates characterised using MLST and spa typing.

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Majority of 261 global ovine isolates belong to one of three clonal complexes (CC).

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One CC has spread across the New World; two are restricted to Europe and Africa.

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Clonal complex spread matches the route and timing of sheep domestication.

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Patterns of clonal diversification of sheep isolates differ from human isolates.

Staphylococcus aureus is an important pathogen of many species, including sheep, and impacts on both human and animal health, animal welfare, and farm productivity. Here we present the widest global diversity study of ovine-associated S. aureus to date. We analysed 97 S. aureus isolates from sheep and sheep products from the UK, Turkey, France, Norway, Australia, Canada and the USA using multilocus sequence typing (MLST) and spa typing. These were compared with 196 sheep isolates from Europe (n = 153), Africa (n = 28), South America (n = 14) and Australia (n = 1); 172 bovine, 68 caprine and 433 human S. aureus profiles. Overall there were 59 STs and 87 spa types in the 293 ovine isolates; in the 97 new ovine isolates there were 22 STs and 37 spa types, including three novel MLST alleles, four novel STs and eight novel spa types. Three main CCs (CC133, CC522 and CC700) were detected in sheep and these contained 61% of all isolates. Four spa types (t002, t1534, t2678 and t3576) contained 31% of all isolates and were associated with CC5, CC522, CC133 and CC522 respectively. spa types were consistent with MLST CCs, only one spa type (t1403) was present in multiple CCs. The three main ovine CCs have different but overlapping patterns of geographical dissemination that appear to match the location and timing of sheep domestication and selection for meat and wool production. CC133, CC522 and CC700 remained ovine-associated following the inclusion of additional host species. Ovine isolates clustered separately from human and bovine isolates and those from sheep cheeses, but closely with caprine isolates. As with cattle isolates, patterns of clonal diversification of sheep isolates differ from humans, indicative of their relatively recent host-jump.

Incidence and characterisation of methicillin-resistant Staphylococcus aureus (MRSA) from nasal colonisation in participants attending a cattle veterinary conference in the UK

We sought to determine the prevalence of nasal colonisation with methicillin-resistant Staphylococcus aureus among cattle veterinarians in the UK. There was particular interest in examining the frequency of colonisation with MRSA harbouring mecC, as strains with this mecA homologue were originally identified in bovine milk and may represent a zoonotic risk to those in contact with dairy livestock. Three hundred and seven delegates at the British Cattle Veterinarian Association (BCVA) Congress 2011 in Southport, UK were screening for nasal colonisation with MRSA. Isolates were characterised by whole genome sequencing and antimicrobial susceptibility testing. Eight out of three hundred and seven delegates (2.6%) were positive for nasal colonisation with MRSA. All strains were positive for mecA and none possessed mecC. The time since a delegate's last visit to a farm was significantly shorter in the MRSA-positive group than in MRSA-negative counterparts. BCVA delegates have an increased risk of MRSA colonisation compared to the general population but their frequency of colonisation is lower than that reported from other types of veterinarian conference, and from that seen in human healthcare workers. The results indicate that recent visitation to a farm is a risk factor for MRSA colonisation and that mecC-MRSA are rare among BCVA delegates (<1% based on sample size). Contact with livestock, including dairy cattle, may still be a risk factor for human colonisation with mecC-MRSA but occurs at a rate below the lower limit of detection available in this study.