Toxin genes and other characteristics of Staphylococcus aureus isolates from milk of cows with mastitis

Prevalence, antimicrobial resistance, and genetic characteristics of Staphylococcus aureus isolates in frozen flour and rice products in Shanghai, China

Staphylococcus aureus is widely recognized as a highly hazardous pathogen that poses significant threats to food safety and public health. This study aimed to assess the prevalence, antimicrobial resistance, and genetic characteristics of S. aureus isolates recovered from 288 frozen flour and rice product samples in Shanghai, China, between September 2019 and May 2020. A total of 81 S. aureus isolates were obtained, representing 25 sequence types (STs), with ST7 being the most prevalent (17.28%, n = 14). The majority of S. aureus isolates (85.19%, n = 69) carried at least one enterotoxin gene, with the seg gene being the most frequently detected (51.85%, n = 42). Additionally, 12 isolates (14.81%) were identified as methicillin-resistant S. aureus (MRSA) through mecA gene detection. Notably, this study reported the presence of an ST398 MRSA isolate in frozen flour and rice products for the first time. All MRSA isolates displayed multidrug resistance, with the highest resistance observed against cefoxitin (100.00%), followed by penicillin (91.67%) and erythromycin (66.67%). Genomic analysis of the 12 MRSA isolates revealed the presence of twenty distinct acquired antimicrobial resistance genes (ARGs), eight chromosomal point mutations, and twenty-four unique virulence genes. Comparative genome analysis indicated close genetic relationships between these MRSA isolates and previously reported MRSA isolates from clinical infections, highlighting the potential transmission of MRSA through the food chain and its implications for public health. Significantly, the identification of three plasmids harboring ARGs, insertion sequences (ISs), the origin of transfer site (oriT), and the relaxase gene suggested the potential for horizontal transfer of ARGs via conjugative plasmids in S. aureus. In conclusion, this study revealed significant contamination of retail frozen flour and rice products with S. aureus, and provided essential data for ensuring food safety and protecting public health.

Genotypes and virulence factors in Staphylococcus aureus isolated from dairy cows with subclinical mastitis in Serbia

This study aimed to determine the prevalence of Staphylococcus aureus subclinical mastitis and to genotype the S. aureus isolates using the 16S-23S rRNA intergenic spacer (RS-PCR) method. In addition, the genes responsible for adherence, biofilm formation, host evasion, tissue necrosis, methicillin resistance, and enterotoxin production of S. aureus were investigated. The overall prevalence of S. aureus subclinical mastitis in lactating cows was 5.4% (95% confidence interval, CI=4.7-6.1%). An increased risk of S. aureus intramammary infection was observed on small family farms (odds ratio, OR=4.2, 95% CI=2.6-6.6, P < 0.001) and medium-sized farms (OR=3.5, 95% CI=2.2-5.7, P < 0.001). The RS-PCR analysis revealed 44 genotypes and genotype variants, of which 15 new genotypes and five new variants were detected within small and medium-sized farms. S. aureus isolates of new genotypes and genotype variants carried the clfA gene responsible for adherence at a lower frequency (64.8%) and enterotoxin-producing genes sea (20.4%), seb (14.8%) and sec (14.8%) at a higher frequency than the other known genotypes (P < 0.001), and were confirmed to carry the sej and sep genes. The spa gene was detected in all S. aureus isolates, whereas none harbored bap, ser, or tsst-1 genes. Methicillin-resistant strains of S. aureus (MRSA) were also detected, with a higher prevalence (19.2%) on large farms with more than 50 cows (P < 0.001). Using molecular techniques as diagnostic tools provides a better understanding of intramammary staphylococcal infections' occurrence, spread, and eradication.

Molecular Characterization of Staphylococcus aureus Complex Isolated from Free-Ranging Long-Tailed Macaques at Kosumpee Forest Park, Maha Sarakham, Thailand

The Staphylococcus (S.) aureus complex, including methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA), and S. argenteus are bacterial pathogens that are responsible for both human and animal infection. However, insights into the molecular characteristics of MRSA, MSSA, and S. argenteus carriages in wildlife, especially in long-tailed macaques, rarely have been reported in Thailand. The objective of this study was to assess molecular characterization of MRSA, MSSA, and S. argenteus strains isolated from free-ranging long-tailed macaques (Macaca fascicularis) at Kosumpee Forest Park, Maha Sarakham, Thailand. A total of 21 secondary bacterial isolates (including 14 MRSA, 5 MSSA, and 2 S. argenteus) obtained from the buccal mucosa of 17 macaques were analysed by a Polymerase chain reaction (PCR) to identify several virulence genes, including pvl, tst, hla, hlb clfA, spa (x-region), spa (IgG biding region), and coa. The most prevalent virulence genes were clfA, coa, and the spa IgG biding region which presented in all isolates. These data indicated that MRSA, MSSA, and S. argenteus isolates from the wild macaques at Kosumpee Forest Park possess a unique molecular profile, harbouring high numbers of virulence genes. These findings suggest that wild macaques may potentially serve as carriers for distribution of virulent staphylococcal bacteria in the study area.

Ecological Distribution of Virulent Multidrug-Resistant Staphylococcus aureus in Livestock, Environment, and Dairy Products

Staphylococcus aureus is one of the most common causes of mastitis, leading to severe economic losses in the dairy industry. It is also zoonotic, with potential risks to public health. This study aimed to detect the occurrence of S. aureus-resistant strains isolated from cattle, buffalo, their environment, milk and dairy products; and to investigate the extent of animal, ecological, and food contamination by methicillin-resistant (MRSA) or enterotoxigenic S. aureus. Samples (n = 350) were collected from four animal (two cattle and two buffalo) farms, i.e., their environment. Thirty Karish cheese samples were collected from 10 markets in Mansoura, Egypt. S. aureus was detected in 17.9%, 17.6%, and 16.7% of samples collected from cattle, buffalo and Karish cheese, respectively. About 19% of isolated S. aureus strains carried the mecA gene. The distribution of the mecA gene was high in isolates from Karish cheese (60%), followed by samples collected from buffalo (16.2%) and cattle (16%). More than 34% of isolated S. aureus strains were enterotoxigenic, and the presence of enterotoxin genes was higher in isolates from Karish cheese (80%) than those from cattle (48%) and buffalo (18.9%). The most predominant enterotoxin gene among isolated S. aureus strains was the sea gene (26.9%), followed by sec (4.5%) and sed (3%) genes. Isolated strains were resistant to clindamycin (100%), kanamycin (97%), nalidixic acid (86.6%), cefotaxime (73.1%) sulphamethazole—trimethoprim (65.6%). Meanwhile, 95.5%, 94%, 86.6% and 77.7% of S. aureus strains were sensitive to ciprofloxacin, amikacin, imipenem and both cefoxitin and gentamycin, respectively. In conclusion, the presence of enterotoxigenic- and methicillin-resistant S. aureus strains in animals, their environment, and dairy products represents a public health concern, particularly in small-scale dairy farms in Egypt. To reduce the risk of infection of livestock and humans with resistant strains, strict regulations and guidelines for antimicrobial use in such a system are urgently required.

Identification of coagulase negative staphylococcal species from bovine mastitis in India

Background

Staphylococcal mastitis is a major cause of concern to the dairy industry in India and several countries worldwide. Though Staphylococcus aureus is the major cause, coagulase negative staphylococcal species (CoNS) are being increasingly reported in recent years.

Aims

To investigate the incidence of coagulase negative staphylococcal species in bovine mastitis.

Methods

Isolation of staphylococci was carried out from 237 milk samples of cows and She buffaloes with clinical and subclinical mastitis from different regions of Andhra Pradesh and Karnataka. CoNS isolates were identified by tube coagulase test using fresh rabbit plasma and coagulase gene PCR. We employed the biochemical test scheme published elsewhere previously for identification of the CoNS isolates up to species and subspecies levels. Seven representative isolates were identified by 16S rDNA sequencing to check the accuracy of biochemical test based identification.

Results

The CoNS constitute the majority of the staphylococcal isolates from mastitis (80/125, 64%) in this region. Using biochemical test scheme, the CoNS isolates from bovine mastitis were identified as S. cohnii sub sp. cohnii, S. simulans, S. capitis sub sp. capitis, S. cohnii sub sp. xylosus, and S. lugdunensis. The CoNS species S. schleiferi, S. haemolyticus, S. sciuri, S. xylosus, S. chromogenes, and Macrococcus epidermidis were identified by 16S rDNA sequencing.

Conclusion

The 16S rDNA sequencing is the appropriate method for the identification of CoNS species. This study highlighted coagulase negative staphylococcal species as possible etiological agents of mastitis.

Prevalence and distribution of multilocus sequence types of Staphylococcus aureus isolated from bulk tank milk and cows with mastitis in Pennsylvania

A total of 163 S. aureus isolates; 113 from mastitic milk (MM) and 50 from bulk tank milk (BTM) (2008, 2013–2015) submitted for bacteriologic analysis at the Penn State Animal Diagnostic Laboratory were examined for their phenotypic and genotypic characteristics. Multi-locus sequence typing (MLST) analysis identified 16 unique sequence types (STs) which belonged to eight clonal complexes (CCs). Majority of the isolates were variants of CC97 (68.7%) and CC151 (25.1%). CC97 comprised of seven STs, of which two were new STs (ST3273, ST3274), while CC151 comprised of three STs of which ST3272 was identified for the first time. Several farms had more than one ST type that were either members of the same clonal complex or unrelated STs. On one farm, six different STs of both categories were seen over the years within the farm. It was observed that ST352 and ST151 were the two main clonal populations in cattle not only in Pennsylvania but also globally. Most isolates were susceptible to all the antibiotics evaluated. 6.7% of isolates showed resistance to vancomycin and penicillin. Two isolates of ST398 showed multidrug resistance (>3 antibiotics) against clindamycin, erythromycin, tetracycline, and penicillin. It was noted that 59 of 163 (36.2%) isolates encoded for enterotoxigenic genes. Enterotoxin genes seg/sei accounted for ~85% of enterotoxin positive isolates. Toxic shock syndrome gene tsst-1 alone was positive in two isolates (ST352, ST 2187). 97.5% of CC151 isolates were enterotoxin seg/sei positive. Most isolates were positive for lukED (95%) and lukAB (96.3%) leukotoxin genes. Bovine specific bi-component leucocidin lukMF’ was present in 54% of isolates. A prominent observation of this study was the explicit association of lukMF’ with lineages ST151 and ST352. In conclusion, the findings of the study, suggest that small number of S. aureus STs types (ST352, ST2187, ST3028, and ST151) are associated with majority of cases of bovine mastitis in Pennsylvania dairy farms. It was observed that one ST of S. aureus predominated in the herd and this ST can coexist with several other ST types of S. aureus strains. When STs were interpreted along with virulence, leucocidin genes and antimicrobial resistance, ST-variants allowed better interpretation of the S. aureus molecular epidemiologic findings specifically for tracing recurrence or persistence of infections in cow over time, among cows in the herd, and between herds in Pennsylvania.

Staphylococcus spp. Isolated from Bovine Subclinical Mastitis in Different Regions of Brazil: Molecular Typing and Biofilm Gene Expression Analysis by RT-qPCR

Bovine mastitis is mainly caused by bacteria of the genus Staphylococcus spp., which possess different virulence factors, including the capacity for biofilm formation that provides enhanced protection against the action of immune system components and serves as a barrier against the penetration of antimicrobial agents. This study aimed to characterize 181 Staphylococcus spp. Strains—including Staphylococcusaureus and coagulase-negative staphylococci (CoNS) isolated from bovine subclinical mastitis in six Brazilian states—by molecular methods. RT-qPCR was used to verify the expression of genes of the ica operon—mainly responsible for biofilm formation—as well as bap and bhp. Chromosome similarity among the isolates was investigated by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). The icaA gene was detected in 79 (43.6%) isolates, icaB in 24 (13.2%), icaC in 57 (31.4%), and icaD in 127 (70.1%). The bap gene was identified in 66 (36.4%) isolates, while the bhp gene was found in nine (4.9%). RT-qPCR confirmed the expression of the icaA gene in 60 (75.9%) isolates, of icaB in six (25%), of icaC in 26 (45.6%), and of icaD in 80 (63%). Clonal typing of the isolates by PFGE permitted the identification of eight Staphylococcusaureus clusters that simultaneously included ≥3 strains, with a similarity of ≥80%. Regarding the other species studied, three clusters were observed for Staphylococcuschromogenes and four clusters for Staphylococcusepidermidis. Only one cluster each was identified for Staphylococcussaprophyticus and Staphylococcussimulans, while the other species did not form any cluster. With respect to MLST, ST126 and ST1 were the prevalent sequence types in S. aureus, while in S.epidermidis all sequence types were different. These results reveal strains with the same evolutionary origin as other isolates, which might cause infections in humans and animals, suggesting their ability to spread between these species.

Overview of the Potential Impacts of Climate Change on the Microbial Safety of the Dairy Industry

Climate change is expected to affect many different sectors across the food supply chain. The current review paper presents an overview of the effects of climate change on the microbial safety of the dairy supply chain and suggest potential mitigation strategies to limit the impact. Raw milk, the common raw material of dairy products, is vulnerable to climate change, influenced by changes in average temperature and amount of precipitation. This would induce changes in the microbial profile and heat stress in lactating cows, increasing susceptibility to microbial infection and higher levels of microbial contamination. Moreover, climate change affects the entire dairy supply chain and necessitates adaptation of all the current food safety management programs. In particular, the review of current prerequisite programs might be needed as well as revisiting the current microbial specifications of the receiving dairy products and the introduction of new pretreatments with stringent processing regimes. The effects on microbial changes during distribution and consumer handling also would need to be quantified through the use of predictive models. The development of Quantitative Microbial Risk Assessment (QMRA) models, considering the whole farm-to-fork chain to evaluate risk mitigation strategies, will be a key step to prioritize actions towards a climate change-resilient dairy industry.

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.

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.

Villa T, Barros-Velázquez J, Cañas B, Sánchez-Pérez A, Calo-Mata P, Carrera M. Staphylococcus aureus Exotoxins and Their Detection in the Dairy Industry and Mastitis

Staphylococcus aureus constitutes a major food-borne pathogen, as well as one of the main causative agents of mastitis in dairy ruminants. This pathogen can produce a variety of extracellular toxins; these include the shock syndrome toxin 1 (TSST-1), exfoliative toxins, staphylococcal enterotoxins (SE), hemolysins, and leukocidins. S. aureus expresses many virulence proteins, involved in evading the host defenses, hence facilitating microbial colonization of the mammary glands of the animals. In addition, S. aureus exotoxins play a role in the development of both skin infections and mastitis. Indeed, if these toxins remain in dairy products for human consumption, they can cause staphylococcal food poisoning (SFP) outbreaks. As a result, there is a need for procedures to identify the presence of exotoxins in human food, and the methods used must be fast, sensitive, reliable, and accurate. It is also essential to determine the best medical therapy for human patients suffering from S. aureus infections, as well as establishing the relevant veterinary treatment for infected ruminants, to avoid economic losses in the dairy industry. This review summarizes the role of S. aureus toxins in the development of mastitis in ruminants, their negative effects in the food and dairy industries, and the different methods used for the identification of these toxins in food destined for human consumption.

Molecular epidemiology of methicillin-resistant Staphylococcus aureus from dairy farms in North-eastern Italy

Transmission of Staphylococcus aureus along the dairy production chain is an emerging public health problem with human, veterinary, and food safety issues. The prevalence of multidrug-resistant, particularly methicillin-resistant S. aureus (MRSA), has steadily increased in several European countries. In this study, the prevalence of S. aureus in raw cow milk and farm workers was investigated, and the trajectories of MRSA transmission at the primary stage of the dairy chain were assessed. To this purpose, a longitudinal survey was conducted in 618 dairy farms in two contiguous regions with high livestock density in North-eastern Italy. S. aureus contamination of bulk tank milk (BTM) was observed in more than 80% of farms, while MRSA prevalence was 3.6% and 15.9% in BTM and farm workers, respectively. The majority of MRSA isolates from both BTM and farm workers were assigned to ST398, and showed a worrisome multidrug-resistant phenotype. Enterotoxin and Panton-Valentine leukocidin genes were detected in 11.5% and 4.9% of MRSA isolates from both sources. Nearly all MRSA isolates from workers belonged to the same epidemiological type as BTM isolates from the corresponding farm, denoting a bidirectional MRSA transmission pattern. A focus on the ST398 spa type t899 MRSA lineage in the Italian livestock system highlighted the presence of two major clusters whose dissemination was likely facilitated by the selective pressure imposed by antimicrobial use in animal farming. Our findings emphasize the need for continuous monitoring of MRSA along the dairy production chain, not only to avoid transmission between animals and exposed workers, but also to contain the risk of raw milk and dairy product contamination by multidrug resistant and toxigenic strain.

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.

Prevalence, molecular typing, and antimicrobial resistance of bacterial pathogens isolated from ducks

Aim:

This study aimed to investigate the prevalence of different bacterial species affecting ducks as well as demonstrating the antimicrobial susceptibility and molecular typing of the isolated strains.

Materials and Methods:

A total of 500 samples were randomly collected from different duck farms at Ismailia Governorate, Egypt. The collected samples were subjected to the bacteriological examination. Polymerase chain reaction (PCR) was applied for amplification of Kmt1 gene of Pasteurella multocida and X region of protein-A (spA) gene of the isolated Staphylococcus aureus strains to ensure their virulence. The antibiotic sensitivity test was carried out.

Results:

The most common pathogens isolated from apparently healthy and diseased ducks were P. multocida (10.4% and 25.2%), Escherichia coli (3.6% and 22.8%), Staphylococcus epidermidis (10% and 8.8%), Pseudomonas aeruginosa (2% and 10%), and Proteus vulgaris (0.8% and 10%), respectively. In addition, S. aureus and Salmonella spp. were isolated only from the diseased ducks with prevalence (12.2%) and (2.8%), respectively. Serotyping of the isolated E. coli strains revealed that 25 E. coli strains were belonged to five different serovars O1, O18, O111, O78, and O26, whereas three strains were untypable. Salmonella serotyping showed that all the isolated strains were Salmonella Typhimurium. PCR revealed that four tested P. multocida strains were positive for Kmt1 gene with specific amplicon size 460 bp, while three strains were negative. In addition, all the tested S. aureus strains were positive for spA gene with specific amplicon size 226 bp. The antibiotic sensitivity test revealed that most of the isolated strains were sensitive to enrofloxacin, norfloxacin, and ciprofloxacin.

Conclusion:

P. multocida is the most predominant microorganism isolated from apparently healthy and diseased ducks followed by E. coli and Staphylococci. The combination of both phenotypic and genotypic characterization is more reliable an epidemiological tool for identification of bacterial pathogens affecting ducks.

Staphylococcus spp. associated with subclinical bovine mastitis in central and northeast provinces of Thailand

Background

Staphylococcus spp. are major cause of bovine mastitis (BM) worldwide leading to economic damage to dairy farms and public health threat. Recently, a newly emerged Staphylococcus argenteus has been found as a human and animal pathogen. Molecular characteristics, virulence and antibiotic resistant phenotypes of bacteria causing BM in Thailand are rare. This study aimed to investigated Staphylococcus spp. associated with subclinical bovine mastitis (SCM) in Thailand.

Methods

Milk samples were collected from 224 cows of 52 dairy herds in four central and northeast provinces. Total somatic cell counts (SCC) and California mastitis test (CMT) were used to identify SCM cows. Milk samples were cultured for Staphylococcus spp. Coagulase-positive isolates were subjected to pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Organisms suspected as S. argenteus were verified by detecting nonribosomal peptide synthetase gene. All isolates were checked for antibiograms and the presence of various virulence genes.

Results

From the 224 milk samples of 224 cows, 132 (59%) were positive for SCM by SCC and CMT and 229 staphylococcal isolates were recovered. They were 32 coagulase-positive (24 S. aureus and eight S. argenteus) and 197 coagulase-negative. PFGE of the S. aureus and S. argenteus revealed 11 clusters and a non-typeable pattern. MLST of representatives of the 11 PFGE clusters, three PFGE non-typeable S. aureus isolates from different locations and S. argenteus showed 12 sequence types. The eight S. argenteus isolates belonged to ST1223 (three isolates), ST2250 (two isolates), and ST2793 (two isolates). The antimicrobial tests identified 11 (46%) methicillin-resistant S. aureus and 25 (13%) methicillin-resistant coagulase-negative isolates, while seven S. argenteus were methicillin-susceptible and one isolate was methicillin-resistant. All of the 229 isolates were multiply resistant to other antibiotics. The most prevalent virulence genes of the 24 S. aureus isolates were clfA, coa and spa (X and IgG-binding region) (100%), hla (96%), pvl (96%) and sec (79%). Six S. argenteus isolates carried one enterotoxin gene each and other virulence genes including coa, clfA, hla/hlb, spa, tsst and pvl, indicating their pathogenic potential.

Conclusion and perspective

This is the first report on the S. argenteus from cow milk samples with SCM. Data on the molecular characteristics, virulence genes and antibiograms of the Staphylococcus spp. obtained from the present study showed a wide spread and increasing trend of methicillin-resistance and multiple resistance to other antibiotics. This suggests that the "One Health" practice should be nurtured, not only at the dairy farm level, but also at the national or even the international levels through cooperation of different sectors (dairy farmers, veterinarians, medical and public health personnel and scientists) in order to effectively combat and control the spread of these pathogens.

Detection of coagulase gene in Staphylococcus aureus from several dairy farms in East Java, Indonesia, by polymerase chain reaction

Aim:

This study was conducted to study the coagulase (coa) gene-based genetic diversity of Staphylococcus aureus, isolated from different samples of cattle from three different regions in East Java Province, Indonesia.

Materials and Methods:

A total of 160 raw milk samples collected in East Java Province, Indonesia, were screened for the presence of S. aureus. The presumptive isolates were confirmed by coa test. The confirmed S. aureus isolates were subjected to coa gene polymerase chain reaction.

Results:

Of 160 different samples, 20 (12.5%) isolates of S. aureus were confirmed by positive coa test. Of 20 S. aureus isolates, 19 (95%) isolates carried coa gene. Six different genotypes of coa gene, i.e., 440 bp, 510 bp, 547 bp, 680 bp, 740 bp, and 820 bp were obtained. One coa genotypes, 510 bp (10 isolates) were observed in polymorphism to be more prevalent than the others, and the genotype was present in at least one isolates from every region.

Conclusion:

It can be concluded that coa gene is easily epidemiological tool for detection of variation strain from S. aureus.

OCORRÊNCIA DE GENES CODIFICADORES DE ENTEROTOXINAS ESTAFILOCÓCICAS EM AMOSTRAS DE LEITE DE VACAS

Resumo Objetivou-se com este trabalho identificar a ocorrência de genes codificadores de enterotoxinas estafilocócicas (sea, seb, sec e seg) e do gene da toxina 1 responsável pela síndrome do choque tóxico (tst) em isolados de Staphylococcus aureus procedentes de casos de mastite bovina, no estado de Pernambuco, Brasil. Foram analisados 93 isolados e observou-se a presença de genes toxigênicos em 20 (21,6%) deles, dos quais 11 (55,0%) foram positivos para o gene tst, sete (35,0%) para o gene sec e dois (10,0%) para o gene seg. Dentre os 20 isolados que amplificaram na PCR para presença dos genes sec, seg e tst, 16 (80,0%) foram positivos apenas para um gene e quatro (20,0%) foram positivos para dois genes (sec e tst). Das 17 propriedades de onde as amostras tiveram origem, sete (41,2%) apresentaram amostras positivas para pelo menos um dos genes sec, seg e tst. Este é primeiro registro de ocorrência dos genes codificadores das enterotoxinas SEC e TST-1 em amostras de leite de vacas com mastite no estado de Pernambuco, Brasil.

Staphylococcus aureus Isolates from Bovine Mastitis in Eight Countries: Genotypes, Detection of Genes Encoding Different Toxins and Other Virulence Genes

Staphylococcus aureus is recognized worldwide as one of the major agents of dairy cow intra-mammary infections. This microorganism can express a wide spectrum of pathogenic factors used to attach, colonize, invade and infect the host. The present study evaluated 120 isolates from eight different countries that were genotyped by RS-PCR and investigated for 26 different virulence factors to increase the knowledge on the circulating genetic lineages among the cow population with mastitis. New genotypes were observed for South African strains while for all the other countries new variants of existing genotypes were detected. For each country, a specific genotypic pattern was found. Among the virulence factors, fmtB, cna, clfA and leucocidins genes were the most frequent. The sea and sei genes were present in seven out of eight countries; seh showed high frequency in South American countries (Brazil, Colombia, Argentina), while sel was harboured especially in one Mediterranean country (Tunisia). The etb, seb and see genes were not detected in any of the isolates, while only two isolates were MRSA (Germany and Italy) confirming the low diffusion of methicillin resistance microorganism among bovine mastitis isolates. This work demonstrated the wide variety of S. aureus genotypes found in dairy cattle worldwide. This condition suggests that considering the region of interest might help to formulate strategies for reducing the infection spreading.

Detection of Enterotoxin Genes and Methicillin-Resistance in Staphylococcus aureus Isolated from Water Buffalo Milk and Dairy Products

The aim of this study was to analyze the presence of genes encoding staphylococcal enterotoxins and methicillin resistance in Staphylococcus aureus isolates obtained from water buffalo milk and dairy products. A total of 200 samples (100 raw milk, 50 clotted cream, and 50 cheese samples) was collected from different dairy farms and smallholders in Samsun, Turkey. All samples were analyzed using the standard procedure EN ISO 6888-1 and isolates were confirmed for the presence of the target 16S rRNA specific for Staphylococcus genus specific and nuc gene specific for S. aureus species by PCR. S. aureus was identified in 30 of 100 milk (30%), 9 of 50 clotted cream (18%), and 17 of 50 cheese (34%) samples. A total of 99 isolates was confirmed as S. aureus. Genotypic methicillin resistance was evaluated using PCR for the mecA gene. Out of 99 isolates, nine (9%) were found to be methicillin resistant (mecA gene positive). Twelve out of 99 (12%) S. aureus isolates were found positive for one or more genes encoding the enterotoxins. The gene coding for enterotoxin, sea, was the most frequent (five isolates, 41.6%), followed by sec (two isolates, 16.6%), sed (1 isolates, 8.3%) and see (1 isolate, 8.3%). While three isolates (25%) contained both sec and sed, none of the samples was positive for seb. In conclusion, the presence of se gene-positive and methicillin-resistant S. aureus in buffalo milk and products revealed that consumption of these products is a potential risk of foodborne infection in this region.

PRACTICAL APPLICATION

Enterotoxigenic and methicillin-resistant S. aureus (MRSA) in milk and dairy products is an important public health problem. Especially in traditional dairy products, Staphylococcal enterotoxins may cause food poisoning due to consumption of raw or unpasteurized milk products.

Presence of Classical Enterotoxin Genes, agr Typing, Antimicrobial Resistance, and Genetic Diversity of Staphylococcus aureus from Milk of Cows with Mastitis in Southern Brazil

Staphylococcus aureus is a common causative agent of bovine mastitis in dairy cows and commonly associated with foodborne disease outbreaks. The aim of this study was to evaluate the presence of enterotoxin genes, agr typing, antimicrobial resistance, and genetic diversity of S. aureus isolated from milk of cows with mastitis in dairy farms from southern Brazil. Results showed that 7 (22.6%) of 31 S. aureus isolates were positive for enterotoxin genes. Specifically, the genes encoding for enterotoxins A ( n = 4), C ( n = 2), and B ( n = 1) were detected. Isolates belonging to the agr group III (10 of 31, 32.2%) and agr group I (7 of 31, 22.5%) were the most common. To our knowledge, this is the first report of both agr I and III in the same S. aureus isolate from milk of cows with bovine mastitis. The antimicrobial resistance test showed that 54% of the isolates were multiresistant to antimicrobial agents. The macrorestriction analysis produced 16 different major SmaI pulsed-field gel electrophoresis patterns, with up to two subpatterns. Moreover, the presence of some S. aureus clones in a distinct area was observed. Although this study characterized a limited number of S. aureus isolates, the presence of classical enterotoxin genes and resistance to multiple antimicrobial agents reinforces the importance of this microorganism to animal and human health. In addition, similar genetic profiles have been identified in distinct geographic areas, suggesting clonal dissemination of S. aureus in dairy herds from southern Brazil.

Characterization of Toxin Genes and Antimicrobial Susceptibility of Staphylococcus aureus from Retail Raw Chicken Meat

The aim of this study was to investigate the toxin gene profile and antimicrobial resistance of Staphylococcus aureus isolates from raw chicken in the People's Republic of China. In total, 289 S. aureus isolates were characterized by antimicrobial susceptibility testing, and genes encoding enterotoxins, exfoliative toxins, Panton-Valentine leukocidin, and toxic shock syndrome toxin were revealed by PCR. Overall, 46.0% of the isolates were positive for one or more toxin genes. A high proportion of toxin genes were pvl (26.6%), followed by sej (12.5%), sea (9.0%), seh (8.3%), seb (6.9%), sec (6.9%), sed (4.8%), sei (3.1%), and see (2.4%). None of the isolates harbored seg, tsst-1, or exfoliative toxin genes. In total, 29 toxin gene profiles were obtained, and pvl (10.7%) was the most frequent genotype, followed by sea (5.9%), seb (4.8%), and sej (4.2%). Furthermore, 99.7% of the strains were resistant to at least one of the tested antimicrobial agents, and 87.2% of them displayed multidrug resistance. Resistance was most frequently observed to trimethoprim-sulfamethoxazole and erythromycin (86.2% for each), followed by tetracycline (69.9%), amoxicillin-clavulanic acid (45.0%), and ampicillin (42.6%). None of the strains were resistant to vancomycin. This study indicates that S. aureus isolates from raw chicken harbored multiple toxin genes and exhibited multiple antimicrobial resistance, which represents a potential health hazard for consumers.

Comparative genome analysis of 24 bovine-associated Staphylococcus isolates with special focus on the putative virulence genes

Non-aureus staphylococci (NAS) are most commonly isolated from subclinical mastitis. Different NAS species may, however, have diverse effects on the inflammatory response in the udder. We determined the genome sequences of 20 staphylococcal isolates from clinical or subclinical bovine mastitis, belonging to the NAS species Staphylococcus agnetis, S. chromogenes, and S. simulans, and focused on the putative virulence factor genes present in the genomes. For comparison we used our previously published genome sequences of four S. aureus isolates from bovine mastitis. The pan-genome and core genomes of the non-aureus isolates were characterized. After that, putative virulence factor orthologues were searched in silico. We compared the presence of putative virulence factors in the NAS species and S. aureus and evaluated the potential association between bacterial genotype and type of mastitis (clinical vs. subclinical). The NAS isolates had much less virulence gene orthologues than the S. aureus isolates. One third of the virulence genes were detected only in S. aureus. About 100 virulence genes were present in all S. aureus isolates, compared to about 40 to 50 in each NAS isolate. S. simulans differed the most. Several of the virulence genes detected among NAS were harbored only by S. simulans, but it also lacked a number of genes present both in S. agnetis and S. chromogenes. The type of mastitis was not associated with any specific virulence gene profile. It seems that the virulence gene profiles or cumulative number of different virulence genes are not directly associated with the type of mastitis (clinical or subclinical), indicating that host derived factors such as the immune status play a pivotal role in the manifestation of mastitis.

Screening method for Staphylococcus aureus identification in subclinical bovine mastitis from dairy farms

Background:

Staphylococcus aureus is one of the most important contagious bacteria causing subclinical bovine mastitis. This bacterial infection is commonly identified by determine the pathogen in bovine milk samples through conventional technique including coagulase test. However, this test has several disadvantages as low sensitivity, risk of biohazard, cost expensive, and limited preparation especially in local area.

Aim:

Aim of this study was to compare and assess the screening method, Mannitol fermentation test (Mannitol salt agar [MSA]), and deoxyribonuclease (DNase) test, for S. aureus identification in milk samples.

Materials and Methods:

A total of 224 subclinical bovine mastitis milk samples were collected from four provinces of Thailand and determined S. aureus using conventional method and also subjected to the screening test, MSA and DNase test. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) among both tests were analyzed and compared to the tube coagulase test (TCT), as reference method. Immunological test by latex agglutination and molecular assay by determined spa gene were also used to identify and differentiate S. aureus.

Results:

A total of 130 staphylococci were isolated by selective media, Gram-stain, and catalase test. The number of S. aureus which identified using TCT, MSA and DNase test were 32, 102, and 74 isolates, respectively. All TCT results were correlated to results of latex agglutination and spa gene which were 32 S. aureus. MSA showed 100% sensitivity, 28.57% specificity, 31.37% PPV, and 100% NPV, whereas DNase showed 53.13% sensitivity, 41.84% specificity, 22.97% PPV, and 73.21% NPV. DNase test showed higher specificity value than MSA but the test presented 26.79% false negative results whereas no false-negative result from MSA when comparing to TCT.

Conclusion:

MSA had a tendency to be a good preference for screening S. aureus because of its high sensitivity and NPV. The result from this study will improve a choice to use a screening test to diagnose S. aureus of veterinary field for prompt disease controlling and effective treatment.

Detection of icaA and icaD genes of Staphylococcus aureus isolated in cases of bovine mastitis in the Republic of Serbia

Staphylococcus aureus (S. aureus) is the most common agent of contagious mastitis that causes serious health and economic problems. The ability to form biofilms is an important virulence factor of S. aureus for the establishment of persistent infections. This study is aimed to investigate the presence of icaA and icaD, two genes of importance for the biofilm formation in S. aureus bovine mastitis isolates. In order to isolate and identify S. aureus, 1555 milk samples were collected from 401 cows, located in different regions of the Republic of Serbia. Using the conventional microbiological methods 100 isolates were characterized as coagulase-positive staphylococci. After primary biochemical identification, the species confirmation of 44 S. aureus isolates was done using MALDI-TOF Mass Spectrometry and PCR technique, targeting the S. aureus-specific nuc gene. Among all investigated S. aureus isolates 25.0% harbored both icaA gene and icaD genes. The presence of icaD gene alone was confirmed in 40.9% of cases totaling icaD positive isolates to 65.9%. The remaining 34.1% of S. aureus isolates were negative for the presence of both genes. The results of the present study indicate the existence of potential biofilm-producer strains in different regions of the Republic of Serbia, both under intensive and semi-extensive cows breeding.

Phenotypic Antimicrobial Resistance Profile of Isolates Causing Clinical Mastitis in Dairy Animals

Mastitis is the most frequent and costly disease of lactating animals and is associated with a significant reduction in milk yield, increased cost and culling. Early and specific antibiotic based treatment reduces the severity of the disease. Over the years the extensive use of antimicrobials has led to increase antimicrobial resistance. The present study was designed to investigate the prevalence of microorganisms responsible for mastitis and their antimicrobial resistance pattern. A total of 282 milk samples were collected from different animal species (sheep, cows and goats) with clinical mastitis. Antimicrobial resistance was evaluated for Streptococcus spp. and Staphylococcus spp. In cow samples Streptococcus spp. represented the most frequently isolated genus (33.84%), while Staphylococcus spp. was the most prevalent genus in sheep and goat samples (44.4 and 73.86%, respectively). Gentamicin and chloramphenicol were found to be the most effective drugs against the tested isolates, while the highest resistance rates were observed for amoxicillin, ampicillin, tetracycline, trimethoprim-sulfamethoxazole.

Molecular Characterization of Staphylococcus aureus Isolated from Bovine Mastitis and Close Human Contacts in South African Dairy Herds: Genetic Diversity and Inter-Species Host Transmission

Staphylococcus aureus is one of the most common etiological agents of contagious bovine mastitis worldwide. The purpose of this study was to genetically characterize a collection of S. aureus isolates (bovine = 146, human = 12) recovered from cases of bovine mastitis and nasal swabs of close human contacts in the dairy environment. Isolates were screened for a combination of clinically significant antimicrobial and virulence gene markers whilst the molecular epidemiology of these isolates and possible inter-species host transmission was investigated using a combination of genotyping techniques. None of the isolates under evaluation tested positive for methicillin or vancomycin resistance encoding genes. Twenty seven percent of the bovine S. aureus isolates tested positive for one or more of the pyrogenic toxin superantigen (PTSAg) genes with the sec and sell genes predominating. Comparatively, 83% of the human S. aureus isolates tested positive for one or more PTSAg genes with a greater variety of genes being detected. Genomic DNA macrorestriction followed by pulsed-field gel electrophoresis (PFGE) of the bovine isolates generated 58 electrophoretic patterns which grouped into 10 pulsotypes at an 80% similarity level. The majority of the bovine isolates, 93.2% (136/146), clustered into four major pulsotypes. Seven sequence types (ST) were identified among the representative bovine S. aureus isolates genotyped, including: ST8 (CC8), ST97 (CC97), ST351 (CC705), ST352 (CC97), ST508 (CC45), ST2992 (CC97) and a novel sequence type, ST3538 (CC97). Based on PFGE analysis, greater genetic diversity was observed among the human S. aureus isolates. Bovine and human isolates from three sampling sites clustered together and were genotypically indistinguishable. Two of the isolates, ST97 and ST352 belong to the common bovine lineage CC97, and their isolation from close human contacts suggests zoonotic transfer. In the context of this study, the third isolate, ST8 (CC8), is believed to be a human clone which has transferred to a dairy cow and has subsequently caused mastitis. The detection of indistinguishable S. aureus isolates from bovine and human hosts at three of the sampling sites is suggestive of bacterial transmission and supports the need for vigilant monitoring of staphylococcal populations at the human-animal interface.

Staphylococcus enterotoxin profile of China isolates and the superantigenicity of some novel enterotoxins

The genus of staphylococcus widely distributes in environments and contributes to a variety of animal and human diseases. The enterotoxins (SEs) secreted by this type of pathogen have been the leading cause of bacterial toxic shock syndrome and food poisoning, and thus present a substantial concern to public health. In this study, we analyzed the superantigen profile of 122 staphylococcus strains isolated from diverse sources. When screened for the presence and prevalence of 17 known se or se-like (sel) genes, except selj, all other genes were detected in these isolates. In particular, 95.9% of the isolates harbored at least one se/sel gene. Moreover, 47.5% of them bore at least 5. Remarkably, several non-pathogenic species of animal- and environment-origin were also found to carry multiple se/sels. The most frequent genes detected were tsst (62.3%), sei (54.1%), and seb (46.7%), followed by some sel genes (selo, selu, and selm), which also were present at relatively high frequency (20-30%). The generated data improved understanding of strain-specific differences in enterotoxin expression. The gene products of the latter (selo and selu) were subsequently analyzed for their antigenicity in a mouse model using purified E. coli-based recombinant proteins. The studies revealed a strong activity for SEO in induction of T-lymphocyte proliferation and production of various inflammatory cytokines either in vivo or in vitro. In contrast, SEU exhibited little superantigenic effects. The molecular basis for the difference in antigenicity was analyzed by 3D homology remodeling, which revealed a difference in binding and affinities for MHC-II molecules and TCR Vβ region.

Genetic characterization and antimicrobial resistance of Staphylococcus aureus isolated from bovine milk in Tunisia

Staphylococcus aureus is a major agent of bovine mastitis in dairy herds, causing economic losses in dairy industry worldwide. In addition, milk and milk-products contaminated by Staph. aureus can cause harmful human diseases. The aim of this study was to characterize Staph. aureus strains isolated from dairy farms in Tunisia. Bulk tank milk (n = 32) and individual cow milk (n = 130) samples were collected during the period of 2013-2014. Forty-three Staph. aureus isolates were recovered and typed by spa typing, 16S-23S rRNA intergenic spacer (RS-PCR) and multiplex PCRs for 22 virulence genes. Antimicrobial resistance was also investigated with a disc diffusion test. A selected subsample of 22 strains was additionally genotyped by multilocus sequence typing. Seventeen spa types were recovered, and t2421 (n = 10), t521 (n = 6) and t2112 (n = 5) were the most common. Fourteen different RS-PCR genotypes grouped into 11 clusters were detected in our study, with predominance of the R^VI genotype (n = 24). Eight sequence types were identified and Clonal Complex 97, corresponding to RS-PCR cluster R, was the most common (n = 10), followed by CC1 (n = 4), CC15 (n = 3) and other four accounting for one or two strains. Different combinations of virulence genes were reported, and enterotoxin genes were present in few strains (seh, n = 4; sea, n = 2; sea and seh, n = 2; sec and sel, n = 2). The majority of strains were resistant only to penicillin; only one strain was found to be multiresistant and no methicillin-resistant Staph. aureus was demonstrated. Our study reported the isolation of CC97 from bovine milk in Tunisia for the first time and confirmed the relevance of this lineage in intramammary infection in cows.

SIGNIFICANCE AND IMPACT OF THE STUDY

This paper describes the characteristics of Staphylococcus aureus isolated from bulk tank and individual cow milk in Tunisia. All strains were genotyped by spa typing and RS-PCR, a method based on the amplification of the 16S-23S rRNA intergenic spacer region, and multiplex PCRs for 22 virulence genes. A selected subsample of strains was also genotyped by multilocus sequence typing. All strains were tested for antimicrobial resistance. Our study evidences a predominance of strains belonging to Clonal Complex 97. Methicillin-resistant strains were not detected, and overall low level of antimicrobial resistance was reported.

Enterotoxin Gene Profile and Molecular Characterization of Staphylococcus aureus Isolates from Bovine Bulk Milk and Milk Products of Tigray Region, Northern Ethiopia

Staphylococcal food poisoning (SFP) is an important foodborne disease worldwide, and milk and milk products are commonly associated with SFP outbreaks. The objectives of this study were to investigate the distribution of staphylococcal enterotoxin (se) genes in Staphylococcus aureus from raw cow's milk and milk products and to assess their genetic background with the spa typing method. Of the 549 samples (297 bulk milk and 162 milk product samples) collected from Tigray region, Northern Ethiopia, 160 (29.1%) were positive for S. aureus, of which 82 (51%) were found to harbor se genes by a modified multiplex PCR. Nine se genes were identified: sea (n = 12), seb (n = 3), sec (n = 3), sed(n = 4), seg (n = 49), seh (n = 2), sei (n = 40), sej (n = 1), and tsst-1 (n = 24). The classical type of genes accounted for 27%. Of the 82 enterotoxigenic isolates, 41.5 and 12.4% harbored two or more se genes, respectively. The highest gene association was observed between sei and seg, whereas sea and seb were always found together with the new types of se genes. Altogether, 18 genotypes of toxin genes were identified, and 33% of the samples contained > 5 log CFU ml(-1) S. aureus. spa typing identified 22 spa types and three novel spa sequences, which showed the high genetic diversity of the isolates. No apparent relationship was observed between spa type and se genes. Of the 25 spa types, 13 (52%) were from raw milk, 3 (12%) from milk products, and 9 (36%) from both types of sample. Types t314 (20.7%,n = 17), t458 (18.3%, n = 15), and t6218 (9.8%, n= 8) were the most common spa types identified and were widely distributed in three of the eight studied localities. This is the first study from the Tigray region to report the high distribution of enterotoxigenic S. aureus with a diversified genetic background from dairy food. The study may provide valuable data for microbial food safety risk assessment, molecular epidemiology, and phylogenetic studies of S. aureus in Ethiopia.

Detection of Enterotoxigenic Potential and Determination of Clonal Profile in Staphylococcus aureus and Coagulase-Negative Staphylococci Isolated from Bovine Subclinical Mastitis in Different Brazilian States

Epidemiological studies have identified Staphylococcus aureus as the most common agent involved in food poisoning. However, current research highlights the importance of toxigenic coagulase-negative staphylococci (CoNS) isolated from food. The aim of this study was to characterize Staphylococcus spp. isolated from cows with bovine subclinical mastitis regarding the presence of genes responsible for the production of staphylococcal enterotoxins and of the tst-1 gene encoding toxic shock syndrome toxin 1, and to determine the clonal profile of the isolates carrying any of the genes studied. A total of 181 strains isolated in different Brazilian states, including the South, Southeast, and Northeast regions, were analyzed. The sea gene was the most frequent, which was detected in 18.2% of the isolates, followed by seb in 7.7%, sec in 14.9%, sed in 0.5%, see in 8.2%, seg in 1.6%, seh in 25.4%, sei in 6.6%, and ser in 1.6%. The sej, ses, set, and tst-1 genes were not detected in any of the isolates. The typing of the isolates by pulsed-field gel electrophoresis revealed important S. aureus and S. epidermidis clusters in different areas and the presence of enterotoxin genes in lineages isolated from animals that belong to herds located geographically close to each other.

Typing of Staphylococcus aureus obtained from mastitic milk of cattle and buffalo on the basis of two virulence-associated genes (spa and clfA)

Aim:

The present study was undertaken to type Staphylococcus aureus isolates from cattle and buffalo mastitic milk on the basis of spa (X-region) and clfA genes, both responsible for producing virulence factors.

Material and Methods:

In the present investigation S. aureus isolates were isolated as per standard protocols. Typing of S. aureus was carried out by molecular detection of spa and clfA gene by polymerase chain reaction.

Results:

All the 32 isolates from cattle (16) and buffalo (16) were divisible into seven spa types with amplicon sizes ranging between 120 and 380bp. The cattle isolates produced seven different spa amplicons of 120, 150, 200, 250, 280, 300, and 330 bp with 3, 4, 6, 8, 10, 11 and 12 number of tandem repeats, respectively whereas buffalo isolates were divisible into five spa types with amplicons of 150, 200, 250, 330 and 380 bp having calculated number of repeats of 5, 7, 9, 12, and 14, respectively. Of the total isolates, 24 were considered pathogenic on the basis of more than seven number of tandem repeats. In the present investigation, clfA gene was amplified in 27 isolates from cattle and buffalo producing two different amplicons of 900 and 1000 bp sizes showing polymorphism. The most (71.80%) of the isolates produced amplicons of 900 bp while amplicon size of 1000 bp was produced by four (12.5%) of the isolates.

Conclusion:

The presence of these genes with a wide degree of polymorphism confirmed the pathogenic potential of S. aureus and their association with clinical manifestations in mastitis among cattle and buffalo.

Virulence gene profiles in Staphylococcus aureus isolated from cows with subclinical mastitis in eastern Poland

Staphylococcus aureus is arguably the most important pathogen involved in bovine mastitis. The aim of this study was to determine the virulence gene profiles of 124 Staph. aureus isolates from subclinical mastitis in cows in eastern Poland. The presence of 30 virulence genes encoding adhesins, proteases and superantigenic toxins was investigated by PCR. The 17 different combinations of adhesin genes were identified. Occurrence of eno (91·1%) and fib (82·3%) genes was found to be common. The frequency of other adhesion genes fnbA, fnbB, ebps were 14·5, 50, 25%, respectively, and for cna and bbp were 1·6%. The etA and etD genes, encoding exfoliative toxins, were present in genomes of 5·6 and 8·9% isolates, respectively. The splA and sspA, encoding serine protease, were detected in above 90% isolates. The most frequent enterotoxin genes were sei (21%), sem (19·4%), sen (19·4%), seg (18·5%) and seo (13·7%). The tst gene was harboured by 2·4% isolates. The 19 combinations of the superantigenic toxin genes were obtained and found in 35·5% of isolates. Three of them (seg, sei, sem, sen, seo; sec, seg, sei, sem, sen, seo and seg, sei, sem, sen) were the most frequent and found in 16·1% of the isolates. The most common virulotype, present in 17·7% of the isolates, was fib, eno, fnbB, splA, splE, sspA. The results indicate the variation in the presence of virulence genes in Staph. aureus isolates and considerable diversity of isolates that are able to cause mastitis in cows.

Molecular typing, virulence traits and antimicrobial resistance of diabetic foot staphylococci

BACKGROUND

Diabetes mellitus is a major chronic disease that continues to increase significantly. One of the most important and costly complications of diabetes are foot infections that may be colonized by pathogenic and antimicrobial resistant bacteria, harboring several virulence factors, that could impair its successful treatment. Staphylococcus aureus is one of the most prevalent isolate in diabetic foot infections, together with aerobes and anaerobes.

METHODS

In this study, conducted in the Lisbon area, staphylococci isolated (n = 53) from diabetic foot ulcers were identified, genotyped and screened for virulence and antimicrobial resistance traits. Genetic relationship amongst isolates was evaluated by pulsed-field-gel-electrophoresis with further multilocus sequence typing of the identified pulsotypes. PCR was applied for detection of 12 virulence genes and e-test technique was performed to determine minimal inhibitory concentration of ten antibiotics.

RESULTS

Among the 53 isolates included in this study, 41 Staphylococcus aureus were identified. Staphylococcal isolates were positive for intercellular adhesins icaA and icaD, negative for biofilm associated protein bap and pantone-valentine leucocidin pvl. S. aureus quorum sensing genes agrI and agrII were identified and only one isolate was positive for toxic shock syndrome toxin tst. 36 % of staphylococci tested were multiresistant and higher rates of resistance were obtained for ciprofloxacin and erythromycin. Clonality analysis revealed high genomic diversity and numerous S. aureus sequence types, both community- and hospital-acquired, belonging mostly to clonal complexes CC5 and C22, widely diffused in Portugal nowadays.

CONCLUSIONS

This study shows that diabetic foot ulcer staphylococci are genomically diverse, present resistance to medically important antibiotics and harbour virulence determinants. These properties suggest staphylococci can contribute to persistence and severity of these infections, leading to treatment failure and to the possibility of transmitting these features to other microorganisms sharing the same niche. In this context, diabetic patients may become a transmission vehicle for microorganisms' clones between community and clinical environments.

Staphylococcus aureus genotype B and other genotypes isolated from cow milk in European countries

Staphylococcus aureus is globally one of the most important pathogens causing contagious mastitis in cattle. Previous studies, however, have demonstrated in Swiss cows that Staph. aureus isolated from bovine intramammary infection is genetically heterogeneous, with Staph. aureus genotype B (GTB) and GTC being the most prominent genotypes. In addition, Staph. aureus GTB was found to be contagious, whereas Staph. aureus GTC and all the remaining genotypes were involved in individual cow disease. The aim of this study was to subtype strains of Staph. aureus isolated from bovine mastitic milk and bulk tank milk to obtain a unified view of the presence of bovine staphylococcal subtypes in 12 European countries. A total of 456 strains of Staph. aureus were subjected to different typing methods: ribosomal spacer PCR, detection of enterotoxin genes, and detection of gene polymorphisms (lukE, coa). Major genotypes with their variants were combined into genotypic clusters (CL). This study revealed 5 major CL representing 76% of all strains and comprised CLB, CLC, CLF, CLI, and CLR. The clusters were characterized by the same genetic properties as the Swiss isolates, demonstrating high clonality of bovine Staph. aureus. Interestingly, CLB was situated in central Europe whereas the other CL were widely disseminated. The remaining 24% of the strains comprised 41 genotypes and variants, some of which (GTAM, GTBG) were restricted to certain countries; many others, however, were observed only once.

Screening of virulence genes in Staphylococcus aureus isolates from rabbits

<p><em>Staphylococcus aureus</em> is a versatile pathogen able to cause disease in both humans and animals. In rabbits, this bacterium infects animals of different ages, producing several purulent lesions. The ability of <em>S. aureus</em> to cause disease depends on a combination of virulence factors. The aim of this study was therefore to investigate the distribution of bacterial virulence determinants in 69 <em>S. aureus</em> isolates from rabbits. Some virulence factors (7 adhesins, 1 toxin and 1 protease) were positive in all rabbit <em>S. aureus</em> isolates analysed, while others (1 adhesin and 10 toxins) were always negative. The remaining virulence factors were more variable among isolates. An association between genotype and the different profiles of virulence factors was observed, but not with the type of lesion (P&lt;0.05). One strain of each genotype was further analysed by multilocus sequence typing, generating ST121, ST96 and ST2951, determining a greater number of enterotoxins in ST121 isolates compared to ST96 and ST2951 isolates, which could justify the different pathogenicity between strains. </p>

Staphylococcus epidermidis and Staphylococcus haemolyticus: Molecular Detection of Cytotoxin and Enterotoxin Genes

Although opportunistic pathogens, coagulase-negative staphylococci (CoNS), including Staphylococcus epidermidis and Staphylococcus haemolyticus, have long been regarded as avirulent organisms. The role of toxins in the development of infections caused by CoNS is still controversial. The objective of this study was to characterize the presence of enterotoxin and cytotoxin genes in S. epidermidis and S. haemolyticus isolates obtained from blood cultures. Cytotoxin genes were detected by PCR using novel species-specific primers. Among the 85 S. epidermidis and 84 S. haemolyticus isolates, 95.3% and 79.8%, respectively, carried at least one enterotoxin gene. The most frequent enterotoxin genes were sea (53.3%), seg (64.5%) and sei (67.5%). The seg gene was positively associated with S. epidermidis (p = 0.02), and this species was more toxigenic than S. haemolyticus. The hla/yidD gene was detected in 92.9% of S. epidermidis and the hla gene in 91.7% of S. haemolyticus isolates; hlb was detected in 92.9% of the S. epidermidis isolates and hld in 95.3%. Nosocomial Staphylococcus epidermidis and S. haemolyticus isolates exhibited a high toxigenic potential, mainly producing the non-classical enterotoxins seg and sei. The previously unreported detection of hla/yidD and hlb in S. epidermidis and S. haemolyticus using species-specific primers showed that these hemolysin genes differ between CoNS species and that they are highly frequent in blood culture isolates.

Genomic characteristics of Staphylococcus aureus strains associated with high within-herd prevalence of intramammary infections in dairy cows

Staphylococcus aureus is one of the most important causes of mastitis in dairy cattle. Based on previous research, Staph. aureus genotypes with different pathogenic and contagious properties can cause intramammary infection (IMI) and coexist in the same herd. Our study aimed to compare Staph. aureus strains from herds that differed in IMI prevalence using different molecular approaches such as ribosomal spacer (RS)-PCR, multilocus sequence typing (MLST), spa typing, ribotyping, pulsed-field gel electrophoresis (PFGE), and multiplex PCR. For this purpose, 31 dairy herds with Staph. aureus IMI were selected, and 16 of these were chosen for a comparison study: the 8 high-prevalence (HP) herds had Staph. aureus IMI prevalence >28% and the 8 low-prevalence (LP) herds had an IMI prevalence <4%. A total of 650 isolates of Staph. aureus from mammary quarters of all positive cows were genotyped with RS-PCR, a technique based on amplification of a portion of the intergenic spacer 16S-23S rRNA, and a subset of 54 strains was also analyzed by multiplex PCR, ribotyping, PFGE, MLST, and spa typing. The RS-PCR analysis revealed 12 different profiles. Staphylococcus aureus strains isolated from 5 out of 8 HP herds showed a profile identical to the genotype B (GTB), described in previous studies as being strongly associated with high within-herd prevalence of Staph. aureus mastitis and the presence of the genes coding for enterotoxins sea, sed, and sej, a long x-region of spa gene, and 3 lukE fragments. Moreover, all strains isolated in the HP herds possessed genes coding for staphylococcal enterotoxins. In LP herds, a limited number of strains of 6 genotypes, different from those isolated in HP herds, were identified and GTB was not found. Within these genotypes, 4 strains were positive for the mecA gene. Preliminary results and comparison with other genotyping methods confirmed that genotyping by RS-PCR is an accurate, rapid, and inexpensive tool for future field studies on Staph. aureus mastitis strains and generates clinically relevant results.

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.

Diversity and antimicrobial susceptibility profiling of staphylococci isolated from bovine mastitis cases and close human contacts

The objectives of this study were to examine the diversity of Staphylococcus spp. recovered from bovine intramammary infections and humans working in close contact with the animals and to evaluate the susceptibility of the staphylococcal isolates to different antimicrobials. A total of 3,387 milk samples and 79 human nasal swabs were collected from 13 sampling sites in the KwaZulu-Natal province of South Africa. In total, 146 Staph. aureus isolates and 102 coagulase-negative staphylococci (CNS) were recovered from clinical and subclinical milk samples. Staphylococcusaureus was isolated from 12 (15.2%) of the human nasal swabs and 95 representative CNS were recovered for further characterization. The CNS were identified using multiplex-PCR assays, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and tuf gene sequencing. Seven Staphylococcus spp. were identified among the CNS of bovine origin, with Staph.chromogenes (78.4%) predominating. The predominant CNS species recovered from the human nasal swabs was Staph.epidermidis (80%) followed by Staph.chromogenes (6.3%). The antimicrobial susceptibility of all staphylococcal isolates was evaluated using disk diffusion and was supplemented by screening for specific antimicrobial resistance genes. Ninety-eight (67.1%) Staph.aureus isolates of bovine origin were pansusceptible; 39 (26.7%) isolates were resistant to a single class, and 7 (4.8%) isolates were resistant to 2 classes of antimicrobials. Two Staph. aureus (1.4%) isolates were multidrug-resistant. Resistance to penicillin was common, with 28.8% of the bovine and 75% of the human Staph. aureus isolates exhibiting resistance. A similar observation was made with the CNS, where 37.3% of the bovine and 89.5% of the human isolates were resistant to penicillin. Multidrug-resistance was common among the human CNS, with 39% of the isolates exhibiting resistance to 3 or more classes of antimicrobials. The antimicrobial susceptibility results suggest that resistance among staphylococci causing bovine intramammary infections in South Africa is uncommon and not a significant cause for concern. In contrast, antimicrobial resistance was frequently observed in staphylococcal isolates of human origin, highlighting a possible reservoir of resistance genes. Continued monitoring of staphylococcal isolates is warranted to monitor changes in the susceptibility of isolates to different classes of antimicrobials.

An innate immune system-mimicking, real-time biosensing of infectious bacteria

An immune system-mimicking real-time biosensing could detect bacteria (<100 CFU mL⁻¹) automatically within the working time.

Prevalence of Enterotoxigenic Staphylococcus aureus Isolated From Chicken Nugget in Iran

Background:

The enterotoxigenic Staphylococcus aureus is considered as one of the most important cause of food poisoning that manifests with gastroenteritis, diarrhea, and vomiting. Its complications usually occur when bacterial virulence genes are produced. The most important virulence factors are cell-associated components, exoenzymes, exotoxins, enterotoxins, and enterotoxin-like toxins.

Objectives:

The present study aimed to study the presence of S. aureus and its virulence factors in chicken nuggets in Iran.

Materials and Methods:

Totally, 420 chicken nuggets from five brands were collected from Isfahan and Chaharmahal-va-Bakhtiari provinces, Iran. Samples were cultured and the positive results were studied using ELISA and PCR for detection of classical staphylococcal enterotoxins and sea-sej virulence genes, respectively.

Results:

Results showed that 27 (6.42%) of 420 samples were contaminated with S. aureus with bacteria concentration between 6.1 × 10³ to 8.4 × 10¹/mL. Totally, 33.33% of isolates produced SEA, 4.16% SEB, 12.50% SEC, 8.33% SED, 12.50% SEA + SEC, and 12.50% SEA + SED. The most commonly detected genes were sea (25%), sea + seg (8.33%), sec (12.50%), sea + sed (12.50%), and sea + sec + sej (12.50%).

Conclusions:

S. aureus can easily contaminate the chicken nugget and this contamination is usually associated with significant presences of virulence genes. Consumption of these nuggets certainly is associated with gastrointestinal diseases. Therefore, some food safety and quality standards should be applied and performed in most of the Iranian food units to control growth of S. aureus and its virulence factors.