Phenotypic and genotypic characteristics of Staphylococcus aureus isolates from raw bulk-tank milk samples of goats and sheep

Virulence traits, agr typing, multidrug resistance patterns, and biofilm ability of MDR Staphylococcus aureus recovered from clinical and subclinical mastitis in dairy cows

BACKGROUND

Bovine mastitis caused by Staphylococcus aureus is considered a public health threat globally. Herein, we aimed to investigate the occurrence, agr typing, antimicrobial resistance patterns, biofilm production, and PCR-based detection of the virulence, biofilm, adhesion, and enterotoxins genes of S. aureus strains recovered from clinical and subclinical bovine mastitis.

RESULTS

The prevalence of S. aureus in the examined milk samples was 44.4%. Besides, 95% of the retrieved S. aureus strains were identified as MRSA. Herein, all the tested isolates were biofilm producers. PCR revealed that 85% of the retrieved S. aureus strains were positive for the agr I gene. Furthermore, the clfB, clfA, fnbB, fnbA, and cna genes were detected with a prevalence of 100%, 80%, 60%, 55%, and 30%, respectively. Also, all the tested S. aureus strains were positive for the coa gene (100%). Besides, 92.5% and 85% of the recovered strains harbored the lukF and spa genes, respectively. In addition, the prevalence of the hla, hlb, and hlg hemolysin genes was 70%, 50%, and 35%, respectively. Among the enterotoxin genes, the seb gene was detected in 30% of the tested strains. The prevalence of eno and icaA biofilm genes was 95% in the tested strains. Moreover, 15% of S. aureus strains were MDR to 8 antimicrobial agents and harbored the mecA, ermC, and ermB genes. As well, 12.5% of S. aureus strains were MDR to 8 antimicrobial agents and carried the mecA, ermC, ermB, tetK, and tetM genes. Also, 5% of S. aureus strains were XDR to 11 antimicrobial agents and carried the mecA, ermC, and ermB genes.

CONCLUSIONS

The existence of MDR and XDR MRSA strains in bovine milk is a public health hazard. The mecA, ermC, ermB, tetK, and tetM resistance genes and the coa, clfB, eno, icaA, lukF, spa, clfA, and hla virulence genes are commonly associated with the MDR and XDR MRSA strains. Moreover, the seb gene was the predominant enterotoxin gene in the MRSA strains recovered from milk.

Antimicrobial resistance, virulence profiling, and drug repurposing analysis of Staphylococcus aureus from camel mastitis

Camel mastitis especially caused by Staphylococcus aureus (S. aureus), is a major risk to animal health and milk production. The current investigation evaluated the antibiotic susceptibility and virulence factors of S. aureus isolates from subclinical mastitis in camels. A total of 384 milk samples were collected and submitted to isolate S. aureus. The S. aureus isolates exhibiting resistance to Penicillin and Cefoxitin disc on Kirby-Bauer disc diffusion method were considered as β-lactam resistant S. aureus (BRSA) and methicillin-resistant S. aureus (MRSA) which were further confirmed by PCR targeting blaZ and mecA genes, respectively. The results showed that S. aureus was found in 57.06% of subclinical (SCM) positive camel milk samples. A high molecular prevalence of BRSA and MRSA were found to be 48.51% and 46.53% respectively depicting that treating these infections is challenging due to their high resistance levels. The phylogenetic analysis revealed a significant resemblance of the study isolates with each other and with already reported sequences from different countries which shows the potential for the spread of pathogen. Virulence profiling of antibiotic resistance strains showed the presence of virulence markers (nuc and coag genes), intercellular adhesion genes (icaA, icaD), Panton-Valentine leukocidin (pvl) gene, and enterotoxin-producing genes including sea, seb, sec, and sed. In-vitro antibiotic susceptibility testing revealed that the most resistant antibiotic group was penicillin followed by aminoglycosides and cephalosporins. Drug repurposing analysis of different non-antibiotics for combination therapies with resistant antibiotics was done to combat the S. aureus isolates harboring the mecA and blaZ genes. The results revealed the synergistic effect of amoxicillin, sulfamethoxazole, gentamicin, and doxycycline with ketoprofen, amikacin with flunixin meglumine, and gentamicin with N-acetylcysteine (NAC) against study isolates. The current investigation provides the status of antibiotic-resistant strains and virulence factors of S. aureus in the udder of dromedary camels. The combinational therapy of resistant antibiotics with non-antibiotics provides a potential therapeutic option for the treatment of resistant strains.

An Investigation of Virulence Genes of Staphylococcus aureus in Autologous Vaccines Against Sheep Mastitis

Staphylococcus aureus is well known to be the primary causal agent of clinical or subclinical mastitis in dairy sheep. The production of virulence factors allows S. aureus strains to cause mastitis. In the present study, 96 strains isolated from dairy sheep farms used for the production of autologous vaccines were tested for enterotoxin and hemolysin genes by PCR. In addition, 14 strains isolated from half udders of ewes with subclinical mastitis belonging to a single farm were also tested for the same genes. The phylogenetic trees were constructed, and spatial analysis was performed. Overall, 20 gene patterns were identified, but 43.64% of the tested strains showed the same profile (sec+, sel+, hla+, hld+, hlgAC+). Considering only the enterotoxin genes, four profiles were identified while the evaluation of the hemolysin genes revealed the presence of 12 gene patterns. In the farm with subclinical mastitis, six gene profiles were found. Spatial analysis of the isolated strains and their virulence genes did not show a specific pattern. The present study highlights the importance of identifying and analyzing virulence genes of S. aureus strains involved in dairy sheep mastitis, and the presence of different strains in the same farm.

Genomic portraits of methicillin-resistant staphylococci (MRS) from food fish unveiled the genes associated with staphylococcal food poisoning (SFP), virulence and antimicrobial resistance

BACKGROUND

Characteristics of non-clinical strains of methicillin-resistant Staphylococcus aureus (MRSA) especially from fishery environment are poorly understood. This research, in addition to comprehensive characterisation, sought to delineate the genetic relatedness between the MRSA strains originating from clinical as well as non-clinical settings. Out of 39 methicillin-resistant staphylococcal isolates from 197 fish samples, 6 (Three each of methicillin-resistant S. haemolyticus (MRSH) and MRSA) with distinct resistance profiles were selected for whole-genome sequencing. Using respective bioinformatics tools, MRSA genomes were comprehensively characterized for resistome, virulomes, molecular epidemiology and phylogenetic analysis. Simultaneously, MRSH genomes were specifically examined to characterize antimicrobial resistance genes (ARGs), owing to the fact that MRSH is often recognized as a reservoir for resistance determinants.

RESULTS

Three MRSA clones identified in this study include ST672-IVd/t13599 (sequence type-SCCmec type/spa type), ST88-V/t2526, and ST672-IVa/t1309. Though, the isolates were phenotypically vancomycin-sensitive, five of the six genomes carried vancomycin resistance genes including the VanT (VanG cluster) or VanY (VanM cluster). Among the three MRSA, only one harbored the gene encoding Panton-Valentine Leukocidin (PVL) toxin, while staphylococcal enterotoxin (SEs) genes such as sea and seb, associated with staphylococcal food poisoning were identified in two other MRSA. Genomes of MRSH carried a composite of type V staphylococcal cassette chromosome mec (SCCmec) elements (5C2 & 5). This finding may be explained by the inversion and recombination events that may facilitate the integration of type V elements to the SCC elements of S. aureus with a methicillin-susceptible phenotype. Phylogenetically, MRSA from a non-clinical setting displayed a considerable relatedness to that from clinical settings.

CONCLUSION

This study highlights the genetic diversity and resistance profiles of MRSA and MRSH, with non-clinical MRSA showing notable relatedness to clinical strains. Future research should explore resistance gene transfer mechanisms and environmental reservoirs to better manage MRSA spread.

Zoonotic linkage and environmental contamination of Methicillin-resistant Staphylococcus aureus (MRSA) in dairy farms: A one health perspective

Methicillin-Resistant Staphylococcus aureus (MRSA) is a ubiquitous public health challenge, with its prevalence in human, animal, and environmental interfaces posing significant concerns. This study aimed to characterize and detect the zoonotic linkages of MRSA within the cow-environment-human interfaces in dairy farms to address the One Health perspective. A comprehensive investigation, involving 636 samples (an equal number of raw milk and cow nasal swab samples, along with varying numbers of human nasal swab and environmental samples), revealed an overall MRSA prevalence of 13.4% (n = 271/636). Notably, environmental samples exhibited the highest prevalence (19.3%), emphasizing the potential role of farm surroundings in MRSA transmission, while the lowest prevalence was found in raw milk at 11.8% (n = 31/263). The prevalence in cow nasal swabs and human nasal swabs was 13.3% (n = 35/263) and 15.1% (n = 8/53), respectively. Multiplex PCR analysis revealed the presence of different Staphylococcal enterotoxin (SEa, SEb, SEc, and SEd), and exfoliative toxin-producing genes (Eta, Etb) within the MRSA isolates underlining their potential to induce public health threats. All MRSA isolates exhibited complete resistance to Oxacillin (100%) and Amoxicillin (100%), while the highest sensitivity was observed for Vancomycin (85.8%). Furthermore, these MRSA strains demonstrated varying degrees of resistance to other commonly used antimicrobial drugs, including Cefoxitin (75.3%), Ceftarolin (71.2%), Sulfamethoxazole-Trimethoprim (63.5%), Ciprofloxacin (60%), and Gentamicin (49.5%). Detection of MRSA in cow, human, and environmental samples within the same farm vicinity highlights the risk of zoonotic transmission of MRSA from cows to humans through environmental interfaces. Phylogenetic analysis of the mecA gene in MRSA isolates from all sources within the same farm revealed a high similarity index (>84%) among them suggesting a shared evolutionary origin. Moreover, the MRSA isolates from milk samples showed a close evolutionary relationship with isolates from Kenya and Brazil, while the isolates from humans and the environment displayed noticeable resemblance to isolates from several Asian countries. The findings emphasize the importance of collaborative efforts under the One Health framework to address this multifaceted issue and ensure the safety of our food supply and public health.

Enterotoxigenic and Antimicrobic Susceptibility Profile of Staphylococcus aureus Isolates from Fresh Cheese in Croatia

Certain Staphylococcus aureus strains harbour staphylococcal enterotoxin genes and hence can produce enterotoxin during their growth in food. Therefore, food can be a source of staphylococcal food poisoning, one of the most common food-borne diseases worldwide. Epidemiological data show that S. aureus is often present in raw milk cheeses, and consequently, cheeses are often the source of staphylococcal food poisoning outbreaks. The aim of this study was to determine the phenotypic characteristics of S. aureus isolates from fresh cheese, including antibiotic susceptibility; the presence of classical sea-see enterotoxin genes through molecular methods; and the isolate's ability to produce SEA-SEE enterotoxins in vitro through reversed passive latex agglutination. A total of 180 coagulase-positive staphylococci were isolated from 18 out of 30 cheese samples, and 175 were confirmed as S. aureus through latex agglutination and API STAPH tests. All isolates possessed phenotypic characteristics typical for S. aureus, with certain variations in the egg yolk reaction (18.3% of the isolates showed a weak reaction and 28% no reaction at all) and haemolysis pattern (36.6% of the isolates produced double-haemolysis and 4.6% were non-haemolytic). Antibiotic resistance was observed in 1.1% of the isolates and to mupirocin only. Real-time PCR detected the sec gene in 34 (19.4%) isolates, but most isolates (80.6%) were not enterotoxigenic. For all 34 (19.4%) strains that carried the sec gene, the RPLA method detected the production of the SEC enterotoxin in vitro. For those enterotoxigenic strains, the possibility of enterotoxin production in fresh cheese could not be ruled out.

On-farm epidemiology, virulence profiling, and molecular characterization of methicillin-resistant Staphylococcus aureus at goat farms

Antimicrobial resistance (AMR) becomes a challenging issue that limits the therapeutic options for both veterinary and public health professionals. The current study aimed to investigate the on-farm epidemiology, antibiotics resisting profiling, virulence analysis, and molecular detection of methicillin-resistant Staphylococcus aureus (MRSA) at the caprine-human interface. A total of 768 goat milk samples and 94 skin swabs from farm personnel were collected from 30 goat flocks and processed for isolation of S. aureus. The study isolates were confirmed as MRSA based on the oxacillin and cefoxitin disc diffusion test and the presence of mecA gene. MRSA isolates of goats and human origin were characterized and further evaluated for the presence of virulence genes responsible for intramammary infections and public health hazards. The results revealed 26.82 % and 27.79 % goat milk samples and human samples positive for S. aureus, respectively. A higher MRSA prevalence of 35.92 % and 10.71 % was found in goat and human isolates respectively. The phylogenetic analysis revealed a lesser extent of homology in mecA gene of S. aureus isolates at the caprine-human interface. Moreover, this study revealed strong evolutionary connection between the study isolates and MRSA isolates of Pakistani cattle and buffalo while the in-silico protein analysis showed that all sequences have the same protein motifs resembling penicillin binding protein 2a. The risk factors analysis revealed that teat length, drainage system, hygienic measures during milking, use of teat dip, teat injury, and veterinary services were significantly associated with subclinical mastitis in goats. A total of 43.24 % of local MRSA isolates showed multi-drug resistance (MDR). The isolates showed higher resistance to oxytetracycline followed by gentamicin and vancomycin while moxifloxacin, and linezolid were among the susceptible antibiotics. Local MRSA isolates carried virulence markers (nuc and coag genes) and biofilm-associated icaA (43.24 %) and icaD (29.73 %) genes which are responsible for the intramammary infection. The local isolates also carried the virulence genes of public health concern including the enterotoxin C (sec) gene (24.3 %), enterotoxins B (seb) gene (5.41 %), and enterotoxin D (sed) gene (2.7 %). Enterotoxins A (sea) and E (see) genes were not detected in any isolate. The study concluded that MRSA is an emerging and prevailing pathogen in dairy goats with a high potential to transmit to associated human beings. The presence of a variety of virulence factors as well as the associated antibiotic resistance makes MRSA a potential threat at animal-human interface and thus demands further research.

Phenotypic and genotypic characterization of erythromycin-resistant Staphylococcus aureus isolated from bovine subclinical mastitis in Egypt

Background and Aim

Subclinical mastitis (SCM) caused by erythromycin-resistant Staphylococcus aureus is a significant disease in lactating animals. Therefore, it is crucial to understand the genetic factors contributing to erythromycin resistance in S. aureus. This study aimed to estimate the prevalence of S. aureus in milk from subclinical mastitic cattle and buffaloes and tank milk samples as identified by probe-based real-time polymerase chain reaction (PCR) and the genotypic assessment of macrolide and erythromycin resistance profiles, as well as to analyze the phylogenetic relatedness of our local isolates of S. aureus.

Materials and Methods

In total, 285 milk samples were analyzed using the California mastitis test to detect SCM. Milk samples were cultured on different specific Staphylococcus media. The presence of S. aureus was confirmed by Gram staining, the catalase and coagulase tests, the detection of hemolytic activity, DNase agar testing, and biofilm activity in Congo red medium. The genotypic identification of S. aureus (nuc) was performed. The determinants of erythromycin (ermA, ermB, ermC, and ermT) and macrolide resistance (msrA) were screened in all isolates. DNA sequencing of our local isolates of S. aureus was used to analyze their phylogenetic relatedness. Moreover, histopathological examination of tissue specimens of mammary gland was performed.

Results

The S. aureus positivity rates were 36.4%, 48.8%, and 63.6% in cattle, buffalo, and bulk tank milk, respectively. Probe-based real-time PCR molecularly confirmed all 62 S. aureus isolates. Thirty-one isolates were subjected to PCR to create profiles of their genotypic erythromycin resistance. ermA, ermB, ermC, and ermT were present in 5 (8%), 26 (41.9%), 18 (29%), and 15 (24.1%) S. aureus isolates, respectively. Moreover, msrA was found in three (4.8%) strains. Eight PCR products were produced using standard PCR for DNA sequencing. Multiple sequence alignment, phylogenetic tree construction, and analysis of nuc in S. aureus revealed a high degree of homology (100%) with S. aureus strains isolated from milk in cases of bovine mastitis in India and Kenya. Histological analysis of udder tissues revealed extensive aggregation of mononuclear inflammatory cells in the interstitial connective tissue, primarily lymphocytes, and macrophages.

Conclusion

This study showed a high prevalence of erythromycin resistance in S. aureus isolates. This information is vital for controlling mastitis and the spread of resistance genes between bacterial strains and hosts. Moreover, the probe-based real-time PCR approach is helpful for the rapid screening of S. aureus isolates and the consequent efficient treatment and control of S. aureus mastitis.

Staphylococcus aureus and MRSA in Livestock: Antimicrobial Resistance and Genetic Lineages

Animal production is associated with the frequent use of antimicrobial agents for growth promotion and for the prevention, treatment, and control of animal diseases, thus maintaining animal health and productivity. Staphylococcus aureus, in particular methicillin-resistant S. aureus (MRSA), can cause a variety of infections from superficial skin and soft tissue infections to life-threatening septicaemia. S. aureus represents a serious public health problem in hospital and community settings, as well as an economic and animal welfare problem. Livestock-associated MRSA (LA-MRSA) was first described associated with the sequence (ST) 398 that was grouped within the clonal complex (CC) 398. Initially, LA-MRSA strains were restricted to CC398, but over the years it has become clear that its diversity is much greater and that it is constantly changing, a trend increasingly associated with multidrug resistance. Therefore, in this review, we aimed to describe the main clonal lineages associated with different production animals, such as swine, cattle, rabbits, and poultry, as well as verify the multidrug resistance associated with each animal species and clonal lineage. Overall, S. aureus ST398 still remains the most common clone among livestock and was reported in rabbits, goats, cattle, pigs, and birds, often together with spa-type t011. Nevertheless, a wide diversity of clonal lineages was reported worldwide in livestock.

First Evidence of the Presence of the Causative Agent of Caseous Lymphadenitis-Corynebacterium pseudotuberculosis in Dairy Products Produced from the Milk of Small Ruminants

This study focused on the detection and quantification of selected bacteria and on the presence of enterotoxin genes in milk and dairy products from sheep and goat farms in the Czech Republic using quantitative real-time PCR (qPCR) and multiplex PCR (PCR). The presence of Corynebacterium pseudotuberculosis (CP), Mycobacterium avium subsp. paratuberculosis (MAP), Listeria monocytogenes, Staphylococcus aureus, S. aureus enterotoxin genes and methicillin-resistant Staphylococcus aureus (MRSA) was determined in 18 milk samples, 28 fresh cheeses, 20 ripened cheeses and 14 yoghurts. The serological status of the herds in relation to CP and MAP was taken into account. The most frequently detected bacterium was S. aureus (48.8%), and subsequent PCR revealed 11 MRSA positive samples. The S. aureus enterotoxin genes seg, sei and sec were detected in two goat cheeses. Cheese samples showed a statistically higher risk of SA and MRSA occurrence. CP (8.8%) and MAP (13.8%) were detected by qPCR on two different seropositive farms. Cultivation of qPCR positive CP samples on agar plates supplemented with potassium tellurite showed the presence of viable bacterium. The results obtained confirmed the necessity of monitoring the infectious status of dairy animals and rapid diagnosis of bacterial pathogens in milk and dairy products.

Isolation, Identification, and Antimicrobial Susceptibility Profiles of Staphylococcus aureus from Clinical Mastitis in Sebeta Town Dairy Farms

A cross-sectional study was carried out in and around Sebeta town dairy farms, Finfinne special zone, Ethiopia, from December 2019 to May 2020 to isolate, identify, and test antimicrobial susceptibility profile of Staphylococcus aureus from clinical mastitis. A total of 116 milk samples were purposively collected from 57 lactating cows with clinical mastitis. Isolation and identification of Staphylococcus aureus were carried out by using primary and secondary biochemical tests. Besides, Biolog was used for microbial identification systems. To know if the isolates develop resistance to antibiotics, the antimicrobial susceptibility test (ATS) was performed on Mueller-Hinton agar by the disk diffusion method. From a total of 57 lactating cows and 116 teat quarters examined, 21.05% (12/57) and 15.52% (18/116) were positive for S. aureus from clinical mastitis, respectively. From a total of 116 milk samples collected, 15.52% (18/116) Staphylococcus aureus were isolated, and from 11 farms surveyed, about 72.72% (8/11) overall farm prevalence of clinical mastitis due to S. aureus was recorded. All the 18 Staphylococcus aureus isolates were found susceptible to sulphamethoxazole/trimethoprim, erythromycin, gentamicin, ciprofloxacin, and chloramphenicol. However, high level of resistance was observed to common drugs such as penicillin (88.89%, 16/18) and tetracycline (61.11%, 11/18). The observed high level of resistance to penicillin and tetracycline also indicates the need to visit our treatment guidelines for mastitis caused by Staphylococcus aureus. Therefore, improved management and early treatment of the cases with drug of choice after the antimicrobial susceptibility test for each specific case can reduce chance of further development of resistance and are imperative to tackle clinical mastitis occurring at Sebeta and other similar farms in Ethiopia.

Phenotypic and genotypic study on antibiotic resistance and pathogenic factors of Staphylococcus aureus isolates from small ruminant mastitis milk in South of Italy (Sicily)

Staphyloccoccus aureus is the major cause of mastitis in small ruminants in the Mediterranean farms causing severe losses to dairy industry. Antibiotic treatment has been the most common approach to control these infections. Aim of this study was to investigate antimicrobial resistance (AMR), virulence factors and biofilm-related genes of 84 Sicilian strains of S. aureus isolated from sheep and goats milk during two different periods δT1 (2006-2009) and δT2 (2013-2015). Kirby Bauer method and Polymerase Chain Reaction (PCR) were utilized to monitor AMR and related genes (mecA, tetK, tetM, ermA, ermC). Moreover, toxin genes (tsst-1, sea-see, seg-sej, and sep) and biofilm genes (bap, ica, sasC) were studied. Twenty-six isolates (30.9%) showed multidrug resistance. The two groups showed similar results with exception for higher values of resistance for tilmicosin and lower for sulfamethoxazole and vancomycin of the second group. MecA gene was detected in one isolate. Tetracycline resistance was higher than 20%, with an increase in δT2 group. Toxin genes were found in 5 isolates (5.9%), belonging of δT2 group, while 57 of isolates (67.8%) showed biofilm related genes. The high presence of multi-resistant isolates suggests the need of more responsible use of antibiotic therapy for the control of these infections.

Mild Lactic Acid Stress Causes Strain-Dependent Reduction in SEC Protein Levels

Staphylococcal enterotoxin C (SEC) is a major cause of staphylococcal food poisoning in humans and plays a role in bovine mastitis. Staphylococcus aureus (S. aureus) benefits from a competitive growth advantage under stress conditions encountered in foods such as a low pH. Therefore, understanding the role of stressors such as lactic acid on SEC production is of pivotal relevance to food safety. However, stress-dependent cues and their effects on enterotoxin expression are still poorly understood. In this study, we used human and animal strains harboring different SEC variants in order to evaluate the influence of mild lactic acid stress (pH 6.0) on SEC expression both on transcriptional and translational level. Although only a modest decrease in sec mRNA levels was observed under lactic acid stress, protein levels showed a significant decrease in SEC levels for some strains. These findings indicate that post-transcriptional modifications can act in SEC expression under lactic acid stress.

Non-Digestible Oligosaccharides and Short Chain Fatty Acids as Therapeutic Targets against Enterotoxin-Producing Bacteria and Their Toxins

Enterotoxin-producing bacteria (EPB) have developed multiple mechanisms to disrupt gut homeostasis, and provoke various pathologies. A major part of bacterial cytotoxicity is attributed to the secretion of virulence factors, including enterotoxins. Depending on their structure and mode of action, enterotoxins intrude the intestinal epithelium causing long-term consequences such as hemorrhagic colitis. Multiple non-digestible oligosaccharides (NDOs), and short chain fatty acids (SCFA), as their metabolites produced by the gut microbiota, interact with enteropathogens and their toxins, which may result in the inhibition of the bacterial pathogenicity. NDOs characterized by diverse structural characteristics, block the pathogenicity of EPB either directly, by inhibiting bacterial adherence and growth, or biofilm formation or indirectly, by promoting gut microbiota. Apart from these abilities, NDOs and SCFA can interact with enterotoxins and reduce their cytotoxicity. These anti-virulent effects mostly rely on their ability to mimic the structure of toxin receptors and thus inhibiting toxin adherence to host cells. This review focuses on the strategies of EPB and related enterotoxins to impair host cell immunity, discusses the anti-pathogenic properties of NDOs and SCFA on EPB functions and provides insight into the potential use of NDOs and SCFA as effective agents to fight against enterotoxins.

Methicillin-Resistant Staphylococcus aureus (MRSA): One Health Perspective Approach to the Bacterium Epidemiology, Virulence Factors, Antibiotic-Resistance, and Zoonotic Impact

Methicillin-resistant Staphylococcus aureus (MRSA) is a major human pathogen and a historically emergent zoonotic pathogen with public health and veterinary importance. In humans, MRSA commonly causes severe infectious diseases, including food poisoning, pyogenic endocarditis, suppurative pneumonia, otitis media, osteomyelitis, and pyogenic infections of the skin, soft tissues. In the horse, MRSA could cause a localized purulent infection and botryomycosis; in cattle and ewe, localized pyogenic infection and severe acute mastitis with marked toxemia; in sheep, abscess disease resembles caseous lymphadenitis caused by anaerobic strains; in dogs and cats, pustular dermatitis and food poisoning; in pig, exudative epidermatitis “greasy pig disease; in birds, MRSA causes bumble-foot. The methicillin resistance could be determined by PCR-based detection of the mecA gene as well as resistance to cefoxitin. In Egypt, MRSA is one of the important occasions of subclinical and clinical bovine mastitis, and the prevalence of MRSA varies by geographical region. In this review, we are trying to illustrate variable data about the host susceptibility, diseases, epidemiology, virulence factors, antibiotic resistance, treatment, and control of MRSA infection.

Staphylococcal Enterotoxin C-An Update on SEC Variants, Their Structure and Properties, and Their Role in Foodborne Intoxications

Staphylococcal enterotoxins are the most common cause of foodborne intoxications (staphylococcal food poisoning) and cause a wide range of diseases. With at least six variants staphylococcal enterotoxin C (SEC) stands out as particularly diverse amongst the 25 known staphylococcal enterotoxins. Some variants present unique and even host-specific features. Here, we review the role of SEC in human and animal health with a particular focus on its role as a causative agent for foodborne intoxications. We highlight structural features unique to SEC and its variants, particularly, the emetic and superantigen activity, as well as the roles of SEC in mastitis and in dairy products. Information about the genetic organization as well as regulatory mechanisms including the accessory gene regulator and food-related stressors are provided.

Prevalence, Antimicrobial Resistance Profiles, Virulence and Enterotoxins-Determinant Genes of MRSA Isolated from Subclinical Bovine Mastitis in Egypt

Subclinical mastitis caused by Staphylococcus aureus has worldwide public health significance. Here, we aimed to determine the prevalence of S. aureus, antimicrobial resistance profiles, and the virulence and enterotoxins determinant genes of MRSA strains that caused subclinical bovine mastitis. Milk samples were collected from 120 lactating animals (50 buffaloes and 70 dairy cattle) from different farms located in Ismailia Province (Egypt). The collected samples were investigated for subclinical mastitis using a California mastitis test. The total prevalence of S. aureus was 35.9% (84/234) with 36.3% (53/146) in cattle and 31% (31/88) in buffaloes. Antimicrobial susceptibility testing showed that 35.7% (30/84) of the isolated strains were resistant to cefoxitin, defined as methicillin-resistant S. aureus (MRSA), with 37.7% (20/53) in cattle and 32.2% (10/31) in buffaloes. Using PCR, 100% of the tested strains harbored coa and mecA genes, while 86.6% were positive for spa gene, with remarkable gene size polymorphism. Additionally, 10% of the tested strains contained the pvl gene. Further, using multiplex PCR, 26.6% of the tested samples had sea gene, two strains had sec gene and only one strain had sea and sec genes. The seb and sed genes were absent in the tested strains. In conclusion, mecA, coa and spa virulence genes were widely distributed in MRSA strains isolated from bovine milk, whereas the sea gene was the most predominant enterotoxin gene. Notably, this is the first report that emphasizes the prevalence of pvl gene of MRSA isolated from bovine milk in Egypt.

Molecular typing of Staphylococcus aureus from different sources by RAPD-PCR analysis

Staphylococcus aureus is an opportunistic bacterium which is carried as a normal flora organism but has a major role in the epidemiology and pathogenesis of different staphylococcal infections in humans and animals. Fifty S. aureus isolated from banknotes, foods, human infections and bovine mastitis were subjected to DNA fingerprinting by randomly amplified polymorphic DNA (RAPD) analysis to examine their genotypic polymorphism and investigate the amount of genetic relatedness among these various isolates. At 100% RAPD profile similarity level, isolates were classified into four, five and seven groups of the same clone, according to the RAPDPCR with OLP6, OLP11 and OLP13 primers, respectively. Amplification of the isolates resulted in several polymorphic bands ranged from >50 to >1500 bp in size. Maximum number of bands was obtained by primer OLP13 which produced seven bands in bovine mastitis isolates. Most polymorphisms were observed in isolates of bovine mastitis and the lowest were associated with human infections isolates. There was no relationship between the RAPD patterns and the sources of isolates, except the three clusters which showed host specificity and only included the strains from the same sources. The results confirm the wide genotypic diversity of the studied S. aureus strains. RAPD-PCR technique can be a valuable tool for assessing the genetic relationship, detection of polymorphism in S. aureus and tracing the sources and management of S. aureus infections.

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.

Prevalence and Characterization of Staphylococcus aureus Isolated From Pasteurized Milk in China

Staphylococcus aureus is one of the most important food-borne pathogens globally. It produces various toxins and invasive enzymes and can be found in numerous food products. Milk is an important source of staphylococcal food poisoning. After pasteurization, this microorganism or its enterotoxins might still remain in pasteurized milk. Therefore, this study was to investigate the contamination of S. aureus in 258 pasteurized milk from 39 cities of China. The prevalence and levels of S. aureus in these samples as well as antibiotic susceptibility profiles, virulence genes, biofilm formation, and biofilm related genes, spa typing and MLST were used to determine the characterization among the isolates. It was found 3.9% of samples were detected S. aureus in 8 of 39 cities in China. The contaminated level were not very excessive which showed the MPN values of the most positive samples (9/10) were less than 1 MPN/g. All pasteurized milk-related S. aureus isolates have ability to produce biofilm and harbored icaA, icaD, eno, clfA, clfB, fnbA, fnbB, fib genes, other biofilm related genes icaC were showed in 91.7% of isolates and cna gene were showed in 50%, except bap gene which were free in all isolates. The antibiotic susceptibility test showed that all isolates were resistant or intermediate-resistant to different concentrations of the antibiotics. Furthermore, 75.0% of the isolates were resistant to three or more antibiotic classes, which indicated multidrug resistance. The isolates had virulence potential, which showed 66.7% (8/12) of the isolates carried one or more virulence-associated genes. Molecular typing by MLST and spa typing enabled classification of these isolates into a total of 11 sequence types (STs) and spa types, which indicated high genetic diversity. Most of these types were related to various clinical S. aureus infections. Thus, the findings of this study reflect the potential risk of S. aureus infection in China. Our study also provides comprehensive analysis of the prevalence of S. aureus in pasteurized milk and helps ensure more accurate treatment of human infection with effective antibiotics.

Panton-Valentine leukocidin (PVL) positive methicillin resistant Staphylococcus aureus (MRSA) in raw milk in Punjab

The emergence of methicillin resistant Staphylococcus aureus (MRSA) as a foodborne pathogen has posed a serious public health issue. Milk is extensively consumed food worldwide. The aim of this study was to estimate the presence of MRSA in raw milk in Punjab, by culture and polymerase chain reaction (PCR) techniques. Raw milk samples (291) were collected from all over Punjab. These 291 samples comprised 204 and 87 cow and buffalomilk samples respectively. The S. aureus was isolated on Baird Parker agar and typical colonies were subjected to biochemical tests and PCR for genus (16S rDNA) and species (nuc) specific detection. All the S. aureus isolates were further subjected to susceptibility testing to oxacillin and detection of mecA gene for methicillin resistance. Out of 291 samples, 42 (14.43%) showed contamination of S. aureus. Prevalence of S. aureus contamination was higher in cow milk (15.68%) than buffalo milk (11.49%). Only, three (1.03%) samples (one from buffalo and two from cow) were positive for MRSA. On SCC mec typing, all the MRSA positive isolates belonged to SCC mec type V, which is characteristic of Community Associated-MRSA (CA-MRSA). One isolate was also positive for pvl gene. PFGE showed that all the four isolates were closely related to each other. The results show that MRSA arepresent in food of animal origin and has potential to spread through it.

Development of resistance to antibiotics in bacteria Staphylococcus spp. Isolated from milk samples in the sheep breedings on east of Slovakia

During the last three years (2015 to 2017), the frequency of occurrence of bacteria Staphylococcus spp. were examined in total 3466 individual and 12 pool milk samples. Experiment was carried out in two herds of breed of sheep Improved Valaska in region of East Slovakia. Were isolated and taxonomically identified 15 species of the genus Staphylococcus spp. (n = 444). From the coagulase positive staphylococci (CPS), S. aureus was isolated during the reporting period, however, most often in the first year (45). The incidence of S. intermedius and S. hyicus has been irregular. From the coagulase negative staphylococci (CNS) (n = 288), were isolated S. epidermidis present in 37.5% (108), S. scheiferi 25.69% (74) and S. chromogenes 23.61% (68), while other species occurred only rarely. The bacteria S. aureus (n = 117) showed the highest resistance to novobiocine 14.5%, to erythromycin 12.8%, lincomycin 7.69% and also 7.69% to penicillin. In the framework of the CNS sensitivity we tested 108 strains of S. epidermidis, from which it was 11.1% resistant to novobiocine and 8.3% to erythromycin. Statistical comparison of the incidence of resistance to penicillin and novobiocine in S. aureus and S. epidermidis was performed using Chi square test. There was statistically significant dependence of tracked characters was confirmed on significance level α = 0.05. Also, the incidence of intermediate sensitivity of bacteria in the Staphylococcus spp., indicates the unfavourable development of resistance to the most commonly used antibiotics to treat the inflammation of the udder in sheep. It is therefore recommended to regularly check the resistance to antibiotics and often isolated bacteria CNS.

Safety hazards in bacteriocinogenic Staphylococcus strains isolated from goat and sheep milk

In this study, 28 bacteriocinogenic Staphylococcus strains isolated from goat and sheep milk were subjected to the PCR detection of enterotoxin genes (sea-see), enterotoxin-like toxin Q gene (selq), toxic shock syndrome toxin gene (tst1), and antibiotic resistance genes. They were also evaluated for phenotypic resistance against 10 antibiotics and hemolytic activity. The tyramine and histamine production was investigated using the agar plate assay and capillary zone electrophoretic analysis (CZE). Twenty-five isolates harbored at least one enterotoxin gene. The gene sec was the most frequent (89%). The gene tst1 was found in 84% of sec-positive isolates. The occurrence of antibiotic resistance genes was in the order of blaZ/tetK (100%), mecA/ermB (86%), ermC (50%), and tetM (18%). The genes ermA, aac(6')Ie-aph(2″)Ia, vanA, and vanB were absent in all the isolates. Nineteen isolates were phenotypically susceptible to all the antibiotics. The only isolate with phenotypic resistance to penicillin G and oxacillin was S. epidermidis 4S93 which had a different SmaI-PFGE profile from those of the other S. epidermidis strains. All the S. haemolyticus and S. pseudintermedius isolates were not susceptible to trimethoprim. Twenty-five isolates showed complete or partial hemolytic activity. None of the isolates was able to decarboxylate tyrosine, while CZE analysis revealed histamine formation activity in S. haemolyticus 4S12. The occurrence of safety risks in the isolates reinforces the need for regular monitoring of food-producing animals to mitigate the risks of multidrug resistant and zoonotic pathogens. Moreover, none of the isolates fulfilled the safety criteria to be used as starter cultures or biopreservatives.

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.

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.

Genotype and enterotoxigenicity of Staphylococcus epidermidis isolate from ready to eat meat products

We have previously shown that potentially pathogenic isolates of Staphylococcus epidermidis occur at high incidence in ready-to-eat food. Now, within 164 samples of ready-to-eat meat products we identified 32 S. epidermidis isolates. In 8 isolates we detected the genes encoding for staphylococcal enterotoxins, but in 7 S. epidermidis isolates these genes were not stable over passages. One isolate designated 4S was shown to stably harbour sec and sel genes. In the genome sequence of S. epidermidis 4S we identified 21,426-bp region flanked by direct-repeats, encompassing sec and sel genes, corresponding to the previously described composite staphylococcal pathogenicity island (SePI) in S. epidermidis FRI909. Alignment of S. epidermidis 4S and S. epidermidis FRI909 SePIs revealed 6 nucleotide mismatches located in 5 of the total of 29 ORFs. Genomic location of S. epidermidis 4S SePI was the same as in FRI909. S. epidermidis 4S is a single locus variant of ST561, being genetically different from FRI909. SECepi was secreted by S. epidermidis 4S to BHI broth ranging from 14 to almost 36μg/mL, to milk ranging from 6 to 9ng/mL, to beef meat juice from 2 to 3μg/mL and to pork meat juice from 1 to 2μg/mL after 24 and 48h of cultivation, respectively. We provide the first evidence that S. epidermidis occurring in food bears an element encoding an orthologue to Staphylococcus aureus SEC, and that SECepi can be produced in microbial broth, milk and meat juices. Regarding that only enterotoxins produced by S. aureus are officially tracked in food in EU, the ability to produce enterotoxin by S. epidermidis pose real risk for food safety.

Improved Multiplex Polymerase Chain Reaction for Rapid Staphylococcus Aureus Detection in Meat and Milk Matrices

Staphylococcal food poisoning represents one of the most frequently occurring intoxications, caused by staphylococcal enterotoxins (SE-s) and staphylococcal enterotoxin-like proteins (SEl-s). Therefore, there is a need for rapid, sensitive and specific detection method for this human pathogen and its toxin genes in food matrices. The present work is focused on Staphylococcus aureus detection by a nonaplex polymerase chain reaction, which targets the 23S rRNA gene for identification of S. aureus at the species level, genes for classical SE-s (SEA, SEC, SED), new SE-s (SEH, SEI), SEl-s (SEK, SEL) and tsst-1 gene (toxic shock syndrome toxin). Primers were properly designed to avoid undesirable interactions and to create a reliably identifiable profile of amplicons when visualized in agarose gel. According to obtained results, this approach is able to reach the detection sensitivity of 12 colony forming units from milk and meat matrices without prior culturing and DNA extraction.

Detection of biofilm related genes, classical enterotoxin genes and agr typing among Staphylococcus aureus isolated from bovine with subclinical mastitis in southwest of Iran

Staphylococcus aureus by producing biofilm and facilitating chronic infection is a common cause of mastitis in cows and thereby can cause food poisoning by production of enterotoxins in milk. The agr typing method is an important tool for epidemiological investigation about S. aureus. The aims of the present study were to detect biofilm related genes, 5 classical enterotoxin genes and the agr types among S. aureus isolates. The ability of S. aureus isolates to produce biofilm was evaluated by modified CRA plate. Six biofilm related adhesion genes (icaD, icaA, fnbA, bap, clfA and cna), five classical enterotoxin genes (sea, seb, sec, sed and see) and tst-1 gene were detected by PCR methods. Multiplex-PCR was used to determination of the agr groups. 55 out of 80(68.8%) S. aureus isolates were biofilm producer. The icaD gene was detected in 70 (87.5%) of isolates. The prevalence rates of fnbA, icaA, clfA, cna and bap were 72.5, 56.25, 50, 22.5, and 5% respectively. The agr group I and III were detected in 57.5% 25% of studied isolates. The sea, sed and tst-1 genes were found in 10%, 7.5% and 1.25% of isolates respectively. The majority of S. aureus were able to produce biofilm. Significant associations were observed between presence of the icaD, icaA, fnbA, clfA and the cna genes as well as biofilm formation. The present study revealed that isolates with the agr type III are more potent for biofilm production. Our data supported a possible link between the agr types and certain SE genes.

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.

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.

Microbiological Examination of Bulk Tank Goat's Milk in the Castilla y León Region in Northern Spain

The purpose of the study was to evaluate the microbiological status (mesophilic aerobic microorganism counts) of 68 samples of bulk tank goat's milk and determine the risk associated with the foodborne pathogens Staphylococcus aureus, enteropathogenic and Shiga toxin-producing Escherichia coli, and Cronobacter sakazakii. Most samples (83.8%) complied with the limits of mesophilic aerobe counts set in the European Union for milk of species other than cows. A total of 144 isolates of coagulase-positive staphylococci were characterized, and 11 (7.6%) of them carried staphylococcal enterotoxin (SE) genes of the classical types (encoding SEA to SEE), distributed as follows: 4 carried the SEA gene, 1 the SEB gene, and 6 the SED gene. C. sakazakii was not detected in any sample. Regarding detection of E. coli virulence-related genes in enriched milk samples, 12 milk samples were positive only for the presence of stx genes, 4 were positive for both stx and eae genes, and 20 were negative for stx amplification and positive for eae amplification. Seven enteropathogenic E. coli and 9 Shiga toxin-producing E. coli isolates (one of them of serogroup O157) were recovered. In conclusion, goat's milk produced on farms in Castilla y León is generally in accordance with European Union standards, but the presence of pathogenic E. coli isolates indicates that the consumption of raw goat's milk may pose a risk to public health.

The Use of Multiplex PCR to Determine the Prevalence of Enterotoxigenic Staphylococcus aureus Isolated from Raw Milk, Feta Cheese, and Hand Swabs

Staphylococcus aureus (S. aureus) can cause mastitis in cattle and, therefore, can be present in milk. This study was undertaken to determine the prevalence of coagulase positive S. aureus and its enterotoxin genes sea, seb, and sec in isolates recovered from raw milk, feta cheese, and human hand swabs of milk and cheese handlers in Beni-Suef province, Egypt. A total of 100 samples of raw milk and 50 samples of pasteurized-milk feta cheese were collected. In addition, 50 hand swabs from milk handlers and 25 hand swabs from cheese handlers were examined for the presence of coagulase positive S. aureus. The isolates were characterized by multiplex PCR for detection of sea, seb, and sec genes, and for resistance to 5 classes of commonly used antibiotics. Twelve (12/100), 12 (6/50), and 17% (13/75) of milk, cheese, and hand swab samples, respectively, were positive for coagulase positive S. aureus. One isolate was obtained from each positive sample (31 isolates), and none contained genes for SEA or SEC production. Twenty-five percent, 33%, and 31%, respectively, of the isolates contained the genes for SEB, resulting in 3%, 4%, and 5% of samples being positive for toxin producing coagulase positive S. aureus, respectively. At least one isolate was resistant to each of the antibiotics tested. Despite the low potential for SEB production shown, preventative measures, such as maintenance of the cold-chain and good hygienic practices should be implemented to further reduce the potential risk to public health from SEB, and to reduce the spread of antimicrobial resistance.

Genetic characterization of antibiotic-resistant Staphylococcus aureus from milk in the North-West Province, South Africa

Food borne diseases are a major public health concern worldwide. Staphylococcus aureus is one of the potential food borne pathogens which causes nosocomial and community acquired infections. In the present study, 74 representative strains of S. aureus isolated and characterized in previous study from different milk samples were subjected to random amplified polymorphic DNA (RAPD) polymerase chain reaction (PCR) and enterobacterial repetitive intergenic consensus (ERIC)-PCR to generate fingerprints to determine the genetic relationships of the isolated strains. A total of 20 RAPD patterns were generated and the number of amplified fragments obtained ranged from 0 to 8 with molecular weight ranging from 250 to 2000 bp. A dendrogram based on fingerprinting pattern grouped isolates into twelve major clusters (I–XII). In the case of ERIC-PCR 9 banding patterns were obtained with amplicons ranging from 1 to 8 and band sizes ranging from 250 to 2000 bp. A total of four major clusters (I–IV) were observed in the dendrogram based on ERIC fingerprints. The discrete banding patterns obtained both from ERIC-PCR and RAPD-PCR showed remarkably the genetic diversity of S. aureus. The findings of this study indicate that raw, bulk and pasteurized milk in the North-West Province was contaminated with toxigenic and multi-drug resistant S. aureus strains. This emphasizes the need to implement appropriate control measures to reduce contamination as well as the spread of virulent S. aureus strains to reduce the burden of disease in humans.

Detection of Antibiotic Resistant Staphylococcus aureus from Milk: A Public Health Implication

The aim of this study was to investigate the occurrence, antibiotic susceptibility profiles, and virulence genes determinants of S. aureus isolated from milk obtained from retail outlets of the North-West Province, South Africa. To achieve this, 200 samples of raw, bulk and pasteurised milk were obtained randomly from supermarkets, shops and some farms in the North-West Province between May 2012 and April 2013. S. aureus was isolated and positively identified using morphological (Gram staining), biochemical (DNase, catalase, haemolysis and rapid slide agglutination) tests, protein profile analysis (MALDI-TOF mass spectrometry) and molecular (nuc specific PCR) methods. The antimicrobial resistance profiles of the isolates were determined using the phenotypic agar diffusion method. Genes encoding enterotoxins, exfoliative toxins and collagen adhesins were also screened using PCR. Among all the samples examined, 30 of 40 raw milk samples (75%), 25 of 85 bulk milk samples (29%) and 10 of 75 pasteurised milk samples (13%) were positive for S. aureus. One hundred and fifty-six PCR-confirmed S. aureus isolates were obtained from 75 contaminated milk samples. A large proportion (60%-100%) of the isolates was resistant to penicillin G, ampicillin, oxacillin, vancomycin, teicoplanin and erythromycin. On the contrary, low level resistance (8.3%-40%) was observed for gentamicin, kanamycin and sulphamethoxazole. Methicillin resistance was detected in 59% of the multidrug resistant isolates and this was a cause for concern. However, only a small proportion (20.6%) of these isolates possessed PBP2a which codes for Methicillin resistance in S. aureus. In addition, 32.7% of isolates possessed the sec gene whereas the sea, seb sed, see, cna, eta, etb genes were not detected. The findings of this study showed that raw, bulk and pasteurised milk in the North-West Province is contaminated with toxigenic and multi-drug resistant S. aureus strains. There is a need to implement appropriate control measures to reduce contamination as well as the spread of virulent S. aureus strains and the burden of disease in humans.

Molecular analysis of Staphylococcus aureus pathogenicity islands (SaPI) and their superantigens combination of food samples

Staphylococcus aureus produces a wide variety of superantigenic activity Staphylococcal enterotoxins (SE) and they are a major cause of food poisoning. These superantigens are associated with mobile genetic elements such as plasmids, prophages and S. aureus pathogenicity islands (SaPI). The presence of well-known eight SaPI integrase and 13 enterotoxin genes (sea, seb, sec, sed, see, seg, seh, sei, sej, sel, sek, seq, and tst) in 93 S. aureus strains were investigated. All S. aureus isolates were characterized by pulsed-field gel electrophoresis (PFGE), and the genes were detected using five sets of multiplex PCR (mPCR). The most predominant toxin genes were sea (19%), seb (15%), sec (54%), sell (48%), selk (46%), selq (52%), seg (22%), and sei (19%). Analysis showed that many S. aureus isolates harbored multiple toxin genes. An mPCR-based assay was developed for the determination of all SaPI and their superantigen gene combinations. Twenty three isolates revealed the gene combination sec, sell and tst, typical of the SaPIbov1 and SaPIn1/m1 pathogenicity islands. Twelve isolates revealed the selk and selq gene combination consistent with SaPI3. Eight isolates exhibited the sec and sell genes without the tst gene typical of SaPImw2. We established a correlation between superantigenic toxin genotypes in S. aureus in terms of combinations of toxin gene-encoding SaPI. These results provide a rapid method for determining superantigenic toxin genotypes in S. aureus strains. A total of 24 PFGE patterns were generated. To our knowledge, this is a first study analyzing the correlation of all known SaPI and their enterotoxins in S. aureus using mPCR.

Clonal profile, virulence and resistance of Staphylococcus aureus isolated from sheep milk

The objective of this study was to characterize the clonal profile, virulence factors and antimicrobial resistance, particularly oxacillin resistance, of Staphylococcus aureus isolated from sheep milk. Milk samples were collected from all teats for the California Mastitis Test (CMT), somatic cell count, identification of S. aureus, investigation in these strains of genes encoding toxins (sea, seb, sec, sed, tst), biofilm (icaA, icaC, icaD, bap), leukocidin (luk-PV) oxacillin resistance by mecA gene detection and susceptibility testing (12 antibiotics). Messenger RNA expression was evaluated by RT-PCR in isolates carrying toxin and biofilm genes. Biofilm formation was also evaluated phenotypically by adherence to polystyrene plates. The clonal profile of S. aureus was investigated by pulsed-field gel electrophoresis. A total of 473 milk samples were collected from 242 animals on three farms and 20 S. aureus strains were isolated and none carried the mecA gene. The two sec gene-positive isolates and the isolates carrying the tst and luk-PV genes were positive by RT-PCR. Staphylococcus aureus isolated from the three flocks studied showed high susceptibility to the drugs tested and none was biofilm producer, indicating that biofilm formation was not a virulence factor causing infection by these strains. The typing of 17 S. aureus isolates revealed the presence of a common clone on the three farms studied, and the presence and expression of the sec and tst genes in one strain of this clone suggest the possible acquisition of virulence genes by this clone, a fact that is important for animal health and food hygiene.

The bacteriological quality of goat and ovine milk

This study concentrates on information concerning the microbiological hazards that can be present in raw milk from animal species other than cows. A total of 54 (23 of ovine and 31 of goat) bulk tank milk samples from 10 farms in the Czech Republic were collected in years 2013 - 2014. The sampling was done at regular time intervals during the whole year, with five to eight samples collected from each of the 10 dairy farms involved in the study. All milk samples were collected into sterile sampling bottles and transported in a cooler sampling case to the laboratory for immediate examination. Farms were randomly selected to cover the whole area of the Czech Republic. The prevalence and characteristic of Escherichia coli, Staphylococcus aureus, Salmonella spp., Campylobacter spp. and Listeria monocytogenes was studied. Raw cow's milk can be contaminated by E. coli intramammarily during clinical or subclinical mastitis and either directly through animal feces or indirectly during milk collection through farm employees or the milking equipment. E. coli was detected in 90.3% of the goat milk and 95.7% of the ovine milk samples. The genes encoding Shiga toxins 1 and 2- (stx1, stx2) were not detected and no STEC was identified. The Eae was the detected in 3 (4.6%) isolates. S. aureus was detected in 9 (29.0%) samples of goat milk and 8 (34.8%) samples of ovine milk. A total 12 (57.1%) enterotoxin positive S. aureus were obtained; 6 (28.6%) were positive for the production of sec encoding enterotoxin SEC; in 4 (19.0%) isolates the gene seh was detected; 2 (9.5%) isolates were proven positive for seg (4.8%) and combination seg and sei (4.8%). The presence of MRSA was not detected in the tested samples in our study. L. monocytogenes was detected in 1 (3.2%) samples of goat milk and 1 (4.3%) samples of ovine milk. The serotype (1/2a, 1/2b) was detected in our study. Campylobacter spp. and Salmonella spp. were not isolated from any of the samples. These results form the basis for determining the microbiological quality standards for goat and ovine milk.

Prevalence of multidrug-resistant, coagulase-positive Staphylococcus aureus in nasal carriage, food, wastewater and paper currency in Jalandhar city (north-western), an Indian state of Punjab

Development of multidrug-resistant pattern in the bacterial community is a major threat to the society. Staphylococcus aureus is perhaps the pathogen of the greatest concern because of its inherent virulence, its ability to cause a diverse array of life-threatening situations and capacity to adapt to different environmental conditions. The aims of this study is to investigate the multidrug-resistant pattern of the coagulase-positive S. aureus isolated from nasal carriage, food, paper currency and wastewater samples. We had also studied the multiple antibiotic resistance index and in vitro production of β-lactamase. The study had found out 130 coagulase-positive S. aureus strains isolated from total of 595 samples such as anterior nares of preschool children (195), hospital nurses (100), drivers (76), food (86), wastewater (3) and paper currency (135) (Indian rupee). The biotypes pattern were as follows; A > D > B > C> UT. Multiple antibiotic resistance (MAR) value clearly defines the multidrug-resistant pattern of the S. aureus among different sources. Statistical analysis (one-way ANOVA) of results obtained indicated that the difference in the antibiotic resistance observed in the 130 bacterial isolates against the 23 different antibiotics used in this study was statically significant (p < 0.01).

Distribution of classical enterotoxin genes in staphylococci from milk of cows withand without mastitis and the cowshed environment

The aim of this study was to analyze by PCR 185 isolates of Staphylococcus from milk of cows with- and without mastitis and from the cowsheds environment for their potential ability to produce five classical staphylococcal enterotoxins. Among S. aureus isolates 8 (32%) carried enterotoxin genes and only 2 of them had more than one gene. The enterotoxin genes were detected in 22 (13.7%) coagulase-negative staphylococci (CNS) isolates, among them in 9 (11.4%) isolates of S. xylosus, 5 (16.7%) S. sciuri, 3 (10.3%) S. epidermidis and in 5 (22.7%) Staphylococcus spp. In some CNS 2 or 3 genes were detected simultaneously. Among the investigated enterotoxin genes, sec was the most prevalent (70%). The genes encoding enterotoxin B and D were detected in 5 (16.7%) and 6 (20%) isolates, respectively. The lowest number of isolates had sea and see genes.

The genes encoding enterotoxins were often identified in staphylococci from milk of cows with mastitis (73.4% of detected genes), while only 6 (20%) isolates from milk of cows without mastitis and 2 (6.6%) isolates from cowshed environment were positive for enterotoxin genes.

The results showed that CNS from bovine milk, like S. aureus, carried enterotoxin genes and may pose a risk for public health.

Occurrence of enterotoxin-encoding genes in Staphylococcus aureus causing mastitis in lactating goats

Staphylococcal enterotoxins are the leading cause of human food poisoning worldwide. Staphylococcus spp. are the main mastitis-causing agents in goats and frequently found in high counts in goat milk. This study aimed to investigate the occurrence of enterotoxin-encoding genes in Staphylococcus aureus associated with mastitis in lactating goats in Paraiba State, Brazil. Milk samples (n=2024) were collected from 393 farms. Staphylococcus aureus was isolated in 55 milk samples. Classical (sea, seb, sec, sed, see) and novel (seg, seh, sei) enterotoxin-encoding genes were investigated by means of polymerase chain reaction (PCR). From thirty-six tested isolates, enterotoxin-encoding genes were detected in 7 (19.5%) S. aureus. The gene encoding enterotoxin C (seC) was identified in six isolates, while seiwas observed in only one isolate. The genes sea, seb, sed, see, seg and seh were not observed amongst the S. aureus investigated in this study. In summary, S. aureus causing mastitis in goats can harbor enterotoxin-encoding genes and seC was the most frequent gene observed amongst the investigated isolates. This finding is important for surveillance purposes, since enterotoxin C should be investigated in human staphylococcal food poisoning outbreaks caused by consumption of goat milk and dairy products.