Staphylococcal Enterotoxin Genes Research Articles

Staphylococcal enterotoxin genes are common inStaphylococcus aureusintestinal flora in Sudden Infant Death Syndrome (SIDS) and live comparison infants

Pathological and epidemiological findings in sudden infant death syndrome (SIDS) suggest an infectious aetiology with indications of involvement of staphylococcal enterotoxins (SEs). While SEA, SEB and SEC have been found in the sera and tissues of SIDS cases, little is known about the role of intestinal Staphylococcus aureus or the roles of later-described toxins SEE, SEG, SEH, SEI and SEJ in SIDS. We used a molecular-based approach to define whether the intestinal tract could be a source of SEs to support the staphylococcal toxic shock hypothesis for SIDS. Intestinal contents from 57 SIDS infants and faeces from 79 age- and gender-matched live comparison infants were cultured and tested for S. aureus and sea-b-c-e-g-h-j and TSST using PCR. High proportions of infants in both groups carried toxigenic and nontoxigenic S. aureus. Significantly greater proportions of SIDS compared with comparison babies were positive for S. aureus (68.4% vs. 40.5%) and for SE genes (43.8% vs. 21.5%), suggesting a possible role in SIDS. The results indicate that colonization by S. aureus with SE genes is common in infants; however, their detection is unlikely to be a strong predictive tool for SIDS. Other factors (including immune response) may reveal a specific susceptibility to SEs in SIDS infants.

Methicillin-resistant Staphylococcus aureus strain USA300: origin and epidemiology

Methicillin-resistant Staphylococcus aureus (MRSA) PFGE strain type USA300 (multilocus sequence type 8, clonal complex 8, staphylococcal cassette chromosome mec type IV) was first reported in the USA as a cause of skin and soft issue infection among college football players in Pennsylvania and among prisoners in Missouri in 2000. Over the next 5 years, USA300 became the predominant community-associated MRSA strain in the USA. It was the most common PFGE type recovered from skin and soft tissue infections in persons presenting to 11 emergency departments across the USA, and caused outbreaks in Native American populations, children in daycare centres, military recruits, prison inmates and among men who have sex with men. Although predominantly a cause of skin and soft issue infection, USA300 isolates also have been recovered from cases of invasive disease including bacteraemia, endocarditis, severe necrotizing pneumonia and osteomyelitis. Isolates of USA300 usually carry the genes encoding the Panton-Valentine leucocidin and the arginine catabolic mobile element, but rarely carry staphylococcal enterotoxin genes. USA300 isolates are becoming more resistant to antimicrobial agents, including erythromycin, levofloxacin, mupirocin and tetracycline, and have spread to Europe, South America and Australia. The emergence of the MRSA USA300 strain type represents a unique biological success story.

Differential temporal expression of the staphylococcal enterotoxins genes during cell growth

Staphylococcal enterotoxins (SEs) are a large family of structurally related superantigens produced by Staphylococcus aureus and responsible for staphylococcal food-poisoning (SFP). To better understand how the se genes are expressed, and especially the newly described ones ( seg to ser, seu), a quantitative reverse transcription–polymerase chain reaction was developed and used to monitor their expression in a panel of 28 enterotoxigenic staphylococci including seven reference strains and 21 isolates collected from foods and SFP outbreaks in France. Kinetic mRNA studies revealed four distinct patterns of expression according to the enterotoxins genes analysed corresponding either to: (i) unchanged mRNAs abundance during bacterial growth ( sea, see, sej, sek, seq and sep); (ii) slight decrease in transcript levels ( seg, sei, sem, sen, seo, seu); (iii) drastic induction of expression at the end of the exponential growth phase ( seb, sec, seh), or (iv) modest post-exponential increase in mRNAs level (<10-fold) ( sed, ser, sel). The study demonstrates that all se containing strains are potentially able to produce SEs and that most of the newly described se genes are likely not controlled by the agr system. The rapid assessment of se transcripts levels by RT-qPCR might provide valuable clue to evaluate the poisoning risk linked to a strain.

Development and Use of a Chromogenic Macroarray System for the Detection ofStaphylococcus aureuswith Enterotoxin A, B, C, D, E, and G Genes in Food and Milk Samples

Abstract Staphylococcus aureus is one of the major pathogens that can cause staphylococcal infection and food poisoning. There are five major classical types of staphylococcal enterotoxins (SEs): SEA, SEB, SEC, SED, and SEE, as well as new SEs or SE-like superantigens (SAgs), such as SEG to SEU. Since many S. aureus strains harbor more than one SE gene and identification of SEs involved in food poisoning cases is time consuming, we developed a chromogenic macroarray method that allows convenient and simultaneous detection of classical SE genes and a new SE gene (seg), which is phylogenetically highly related to seb and sec. Two sets of degenerated primers labeled with biotin were used to co-amplify all SE genes in S. aureus strains through the polymerase chain reaction (PCR). Afterwards, these biotin-labeled PCR products were hybridized with SE gene-specific probes spotted on the nitrocellulose membrane. When this macroarray was used to detect enterotoxingenic S. aureus in milk or beef homogenate containing 10(0)-10(4) target cells per milliliter or gram of the sample, all six enterotoxin genes could be identified after a 12-hour enrichment step. This macroarray offers clinical and food inspection laboratories a rapid and economical visual method to detect common enterotoxigenic S. aureus strains.

Diversity and Enterotoxigenicity of Staphylococcus spp. Associated with Domiati Cheese

A total of 87 samples of fresh and stored Domiati cheese (an Egyptian soft cheese) were examined for the presence of Staphylococcus spp. Fifteen Staphylococcus isolates identified as S. aureus (2 isolates), S. xylosus (4), S. caprae (4), and S. chromogenes (5) were recovered from 15 cheese samples. The S. aureus isolates were resistant to penicillin G and ampicillin, and one isolate was also resistant to tetracycline. S. aureus isolates harbored classical staphylococcal enterotoxin (SE) genes (sea and seb) and recently characterized SE-like genes (selg, seli, selm, and selo). One S. aureus isolate contained a single SE gene (sea), whereas another isolate contained five SE genes (seb, selg, seli, selm, and selo). These results suggest that Domiati cheese is a source for various Staphylococcus species, including S. aureus strains that could be enterotoxigenic.

Antibacterial Resistance and Virulence Determinants in Staphylococcus aureus Obtained from Food Handlers in Kuwait City

Introduction: Food handlers are important sources of bacteria causing food poisoning. Consequently, it is important to identify and treat carriers to prevent food poisoning. The purpose of this study was to determine the antibacterial susceptibility patterns and the carriage of virulence genes in S. aureus obtained from food handlers in Kuwait City restaurants. Methods: Two hundred S. aureus isolates were obtained from stool, nasal and hand swabs of food handlers in different restaurants in Kuwait City. Susceptibility to antibacterial agents was done by disk diffusion and Etest. PCR was used to detect genes for accessory gene regulator (agr); capsular polysaccharide serotypes (cap) 5 and 8, staphylococcal enterotoxins (SE), toxic shock syndrome toxin-1 (TSST-1) and Panton-Valentine leukocidin (PVL). Results: A total of 188 (94.0%) isolates were resistant to at least one antibacterial agent and 138 (69.0%) were resistant to two or more antibacterial agents. Majority (78.5%) of them were resistant to penicillin, 63.5% were resistant to cadmium; 19.0%, 9.5% and 2.5% were resistant to tetracycline, trimethoprim and kanamycin and streptomycin respectively. Fifty-seven and 38.0 percent of them belonged to cap8 and cap5 respectively. Fifty, 20 and 23.5 percent of them belonged to agr types I, II and III respectively. Genes for SE, TSST-1 and PVL were detected in 70.5, 4.0 and 9.0 percent respectively. Genes for SEI, SEG, SEC, SEH, SEB, SEA, SED and SEE were present in 36.5, 27.0, 24.5, 23.0, 12.5, 12.0, 1.5 and 1.5 percent respectively. Most (45.5%) of them contained genes for two to four SEs. Genes for PVL were detected in isolates from different sources, and different genetic background but none carried gene for TSST-1. Conclusions: The study demonstrated a wide variation in susceptibility to antibacterial agents and the distribution of virulence determinants, including PVL and justifies the need for regular screening of food handlers to detect and treat carriers and protect restaurant customers from food poisoning.

Comparative prevalence of superantigenic toxin genes in meticillin-resistant and meticillin-susceptible Staphylococcus aureus isolates

A total of 118 meticillin-resistant Staphylococcus aureus (MRSA) and 140 meticillin-susceptible S. aureus (MSSA) isolates from different patients in the same time period were comprehensively searched using a multiplex PCR for the classical and recently described superantigenic toxin gene family comprising the staphylococcal enterotoxin genes sea to ser and the toxic shock syndrome toxin 1 gene, tst-1. Both MRSA and MSSA isolates carried a number of superantigenic toxin genes, but the MRSA isolates harboured more superantigenic toxin genes than the MSSA isolates. The most frequent genotype of the MRSA isolates was sec, sell and tst-1 together with the gene combination seg, sei, selm, seln and selo, which was found strictly in combination in 69.5% of the isolates tested. In contrast, possession of the sec, sell and tst-1 genes in MSSA isolates was significantly less than in MRSA (2.1 vs 77.1%, respectively), although they also often contained the combination genes (25.0%). This notable higher prevalence in MRSA isolates indicated that possession of the sec, sell and tst-1 genes in particular appeared to be a habitual feature of MRSA. Moreover, these were mainly due to the fixed combinations of the mobile genetic elements type I nuSa4 encoding sec, sell and tst-1, and type I nuSabeta encoding seg, sei, selm, seln and selo. Analysis of the relationship between toxin genotypes and the toxin gene-encoding profiles of mobile genetic elements has a possible role in determining superantigenic toxin genotypes in S. aureus.

Multiplex PCR and RPLA Identification of Staphylococcus aureus Enterotoxigenic Strains From Bulk Tank Milk

Enterotoxigenic Staphylococcus aureus in raw milk poses a potential health hazard to consumers, and the identification of such strains should be used as part of a risk analysis of milk and milk products. The primary purpose of this study was to investigate the occurrence of enterotoxigenic S. aureus strains in raw milk supplied for dairy processing in the Czech Republic. A further aim was to compare the production of staphylococcal enterotoxins (SEs) with the presence of the corresponding genes. This was undertaken using multiplex polymerase chain reaction (PCR) and reversed passive latex agglutination (RPLA). Out of 440 bulk tank milk samples from 298 dairy herds, 70 proved positive for S. aureus (15.9%). Staphylococcal enterotoxin genes (ses) were detected in 39 (55.7%) isolates. The genes most commonly detected were sei (38.6%), seg (31.4%) and sea (27.1%). Genes seb, seh, sed, sej and sec were observed in 10%, 4.3%, 2.9%, 2.9% and 1.4% of strains respectively. Genes see and sel did not occur. The most frequently detected genotypes were seg, sei at 11.4%; sea at 10.0%; and sea, seg, sei at 8.6%. Toxin production was observed in nine (12.9%) S. aureus isolates. Seven strains were detected as SEB- (10%) and two as SED- (2.9%) producing. A relatively high number (32%) of discrepancies between the results with multiplex PCR and RPLA assays was obtained, particularly on account of SEA. Nineteen strains were sea positive by PCR but SEA negative by RPLA, and one strain was sec positive and SEC negative. The results of both methods were identical concerning SEB and SED. It was concluded that detection of ses by PCR was a useful additional tool to support identification of enterotoxigenic strains.

PCR detection of staphylococcal enterotoxin genes in Staphylococcus aureus strains isolated from raw and pasteurized milk

Milk is considered a nutritious food because it contains several important nutrients including proteins and vitamins. Conversely, it can be a vehicle for several pathogenic bacteria such as Staphylococcus aureus. This study aimed to analyze the frequency of genes encoding the staphylococcal enterotoxins (SEs) SEA, SEB, SEC, SED, SEE, SEG, SEH, SEI and SEJ in S. aureus strains isolated from raw or pasteurized bovine milk. S. aureus was found in 38 (70.4%) out of 54 raw milk samples at concentrations of up to 8.9 × 10 5 CFU/ml. This microorganism was present in eight samples of pasteurized milk before the expiration date and in 11 samples analyzed on the expiration date. Of the 57 strains studied, 68.4% were positive for one or more genes encoding the enterotoxins, and 12 different genotypes were identified. The gene coding for enterotoxin A, sea, was the most frequent (16 strains, 41%), followed by sec (8 strains, 20.5%), sed (5 strains, 12.8%), seb (3 strains, 7.7%) and see (2 strains, 5.1%). Among the genes encoding the other enterotoxins, seg was the most frequently observed (11 strains, 28.2%), followed by sei (10 strains) and seh and sej (3 strains each). With the recent identification of new SEs, the perceived frequency of enterotoxigenic strains has increased, suggesting that the pathogenic potential of staphylococci may be higher than previously thought; however, further studies are required to assess the expression of these new SEs by S. aureus, and their impact in foodborne disease. The quality of Brazilian milk is still low, and efforts from the government and the entire productive chain are required to attain consumer safety.

Shedding of food-borne pathogens and microbiological carcass contamination in rabbits at slaughter

To obtain microbiological data from rabbits at slaughter, 500 fecal samples and 500 carcasses samples were examined. All samples tested negative for Listeria and Salmonella. Campylobacter were detected in two fecal samples. Of the 500 fecal samples, 45.8% tested positive for eae (intimin), 1.2% for stx (Shiga toxin), and 1.8% for both eae and stx. By colony hybridization, 56 eae positive Escherichia coli strains were isolated. Among them, 27 strains (48.2%) were of the serotypes O178:H7 and O153:H7, whereas 15 strains (26.8%) belonged to a serogroup that has not yet been described (O(CB10681):H7). All strains possessed intimin β1 and the translocated intimin receptor ( tir) capable of being tyrosine phosphorylated. None of the strains harbored the genes for Shiga toxins, EAST1 ( astA), bundlin ( bfpA), or the EAF plasmid. Slaughter rabbits therefore constitute a reservoir for certain atypical enteropathogenic Escherichia coli. On rabbit carcasses, average total bacterial counts accounted for 3.3 log CFU cm −2. Enterobacteriaceae and coagulase positive staphylococci (CPS) were detected on 118 (23.6%) and 153 (30.6%) carcasses, respectively. Enterobacteriaceae and CPS counts of positive samples were mainly <1.5 log CFU cm −2. Among 153 selected CPS isolates, 98.7% were identified as Staphylococcus aureus. None of the 151 isolated strains harbored the gene for methicillin resistance ( mecA). Genes for staphylococcal enterotoxins (SE) were detected in 102 strains. The combinations of seg and sei (53 strains) and sed, seg, sei, and sej (27 strains) dominated.

An alternative method for Staphylococcus aureus DNA isolation

This study describes a rapid procedure for the isolation of genomic DNA from Staphylococcus aureus that yielded a good amount of high quality DNA for the amplification of staphylococcal enterotoxins genes (A, B, C, D, and E) and the TSST-1 gene as well as enzymatic restriction (HaeIII) from environmental isolates. With this method, it was possible to detect these genes in a sample containing as little as 10(5) cells with positive PCR reactions obtained from approximately 10pg of DNA in a final reaction volume of 25µl.

Enterotoxigenic properties of Staphylococcus aureus isolated from goats' milk cheese

Goats' milk cheeses ( n = 181) from the Hessian market (retail shops, weekly markets, farm markets) were quantitatively analysed for Staphylococcus ( S.) aureus, and 14 were found positive. From these samples, 64 isolates of S. aureus were characterized biochemically and genetically, including their potential to produce staphylococcal enterotoxins (SE). SE genes sea to selo was studied by PCR and gene expression was evaluated by reverse transcriptase (RT)-PCR. SEA–SEE production in culture was determined by enzyme immunoassay (EIA). One isolate produced SEA, 18 isolates (from 4 samples) produced SEC, while SEB, SED, and SEE were not found. Toxin production was in agreement with PCR and RT-PCR results for the presence and expression, respectively, of the corresponding toxin genes. Trans-SE genes seg, sei, selm, seln, and selo were detected in 14 isolates from 4 cheese samples, exclusively as clusters. These samples were all from small-scale producers which directly or indirectly market their products regionally. No isolate was positive for seh or sej. RT-PCR detected the presence of the corresponding mRNA for all genes except selo, further indicating the possibility that respective proteins indeed have been produced in culture. These results suggest that S. aureus in goats' milk cheese potentially produces SE like proteins, besides SEA and SEC.

A study of the enterotoxigenicity of coagulase-negative and coagulase-positive staphylococcal isolates from food poisoning outbreaks in Minas Gerais, Brazil

The purpose of this study was to identify enterotoxin genes from isolates of coagulase-negative staphylococci and coagulase-positive staphylococci obtained from dairy products, responsible for 16 outbreaks of food poisoning. From the pool of 152 staphylococcal isolates, 15 coagulase-negative and 15 coagulase-positive representatives were selected for this study. The 15 coagulase-negative isolates were tested for the presence of coa and femA genes, which are known to be characteristic of Staphylococcus aureus. After testing for enterotoxin genes by polymerase chain reaction (PCR), the 30 selected isolates were tested for the presence of toxin by immunoassay. Seven of the coagulase-negative isolates amplified the coa gene and were subsequently reclassified as coagulase-positive. Twenty-one of 30 selected isolates had staphylococcal enterotoxin genes and most of these produced toxin as well. The most frequently encountered enterotoxin genes were sea and seb. Among eight coagulase-negative isolates, five had enterotoxin genes, all of which were found to have detectable toxin by immunoassay. The results from this study demonstrate that coagulase-negative as well as coagulase-positive staphylococci isolated from dairy products are capable of genotypic and phenotypic enterotoxigenicity. Furthermore, these data demonstrate that PCR is a sensitive and specific method for screening outbreak isolates regardless of coagulase expression.

Detection of classical enterotoxins and identification of enterotoxin genes in Staphylococcus aureus from milk and dairy products

Milk and dairy products are frequently contaminated with enterotoxigenic Staphylococcus aureus, which is often involved in staphylococcal food poisoning. The distribution of genes encoding staphylococcal enterotoxins (SE) in S. aureus isolated from bovine, goat, sheep and buffalo milk and dairy products was verified by the presence of the corresponding SE production. A total of 112 strains of S. aureus were tested for SE production by immuno-enzymatic (SEA-SEE) and reversed passive latex agglutination (SEA-SED) methods, while multiplex-PCR was applied for SE genes ( sea, sec, sed, seg, seh, sei, sej and sel). Of the total strains studied, 67% were detected to have some SE genes ( se), but only 52% produced a detectable amount of the classic antigenic SE types. The bovine isolates frequently had enterotoxin SEA, SED and sej, while SEC and sel predominated in the goat and sheep strains. The results demonstrated (i) marked enterotoxigenic S. aureus strain variations, in accordance with strain origin and (ii) the two methods resulted in different information but concurred on the risk of foodstuff infection by S. aureus.

Novel multiplex PCR for the detection of the Staphylococcus aureus superantigen and its application to raw meat isolates in Korea

A multiplex PCR assay that allows for the rapid screening of the 19 genes that encode staphylococcal enterotoxins (SEs) ( sea to see, and seg to sei), SE-like (SEl) toxins ( sej to ser, and seu), and toxic shock syndrome toxin-1 (TSST-1) ( tst) was developed in this study. These toxins are included in the pyrogenic toxin superantigen (PTSAg) family and are responsible for many diseases such as staphylococcal food poisoning (SFP) and TSS. The primers were designed based on dual priming oligonucleotide (DPO) technology to detect all of the 19 SAg genes in three sets of PCR. The developed multiplex PCR was applied to 143 Staphylococcus aureus strains isolated from pork and chicken meat in Korea. Almost 50% of the strains possessed at least one of the 19 SAg genes. The most frequently found genes were seg, sei, sem, and sen (53 isolates, 37%), which were often found simultaneously in the same isolate. In those isolates, the seo (39 isolates, 27%) or seu (6 isolates, 4%) genes were frequently found together and this combination ( seg, sei, sem, sen, and seo or seu) was considered to be a part of the enterotoxin gene cluster ( egc). The sea gene (10 isolates, 7%) was the gene most frequently detected out of all the classical SE genes ( sea to see). Although these classical SEs are considered to be major etiological factors in SFP, newly described SE or SEl genes ( seg to ser, and seu) were more frequently detected than the classical SE genes in this study. There was no isolate detected containing the seb, sec, sek, sel, or seq genes. S. aureus possessing mobile genetic elements known to encode these SAg genes, such as egc, were presumed to be widely distributed among pork and chicken meats in Korea. The multiplex PCR developed in this study could be applied to the investigation of SAg genes in S. aureus strains isolated from various sources.

Characterization of Staphylococcus aureus strains associated with food poisoning outbreaks in France

Enterotoxins produced by Staphylococcus aureus are responsible for staphylococcal food-poisoning outbreaks (SFPO). In France, SFPO are the second cause of food-borne diseases after Salmonella. However, very little is known about the strains involved. The objective of this study was to characterize the staphylococcal strains related to these SFPO through phenotypic and genotypic analyses. A total of 178 coagulase-positive staphylococcal isolates recovered from 31 SFPO (1981–2002) were screened through biotyping. Thirty-three strains representative of the different biotypes in each SFPO were further examined for SmaI macrorestriction-type, phage-type, resistance to various antimicrobial drugs, presence of staphylococcal enterotoxin ( se) genes sea to sei, and production of enterotoxins SEA to SED. All these 33 strains were identified as S. aureus species: 27 were of human biotypes and six ovine or non-host-specific biotypes. Most (74.1%) strains reacted with group III phages. Eleven strains were resistant to at least two classes of antibiotics and among them, two were resistant to methicillin. Twenty-nine strains carried one or several of the eight se genes tested; the gene sea was most common ( n = 23), and often linked to sed ( n = 12) or seh ( n = 5). The novel se genes seg-i were in all cases associated with se genes sea to sed except for one strain which carried only seg and sei. Pulsed-Field Gel Electrophoresis (PFGE) of SmaI macrorestriction digests of the 33 strains discriminated 32 PFGE patterns grouped into nine biotype-specific clusters. All five strains carrying sea and seh were grouped together into the same sub-cluster. Three of the four se-gene-negative strains were in one PFGE cluster: all four should be tested for se genes not included in this study and, if negative, be further investigated for the presence of unidentified SEs.

Staphylococcus aureus and staphylococcal enterotoxin A in breaded chicken products: detection and behavior during the cooking process.

In this study we examined the presence of Staphylococcus aureus and staphylococcal enterotoxin A (SEA) in 20 industrial breaded chicken products obtained from different retail butchers and supermarket stores in Italy. The levels of contamination in the products analyzed were quite low, although the pH values and water activities (a(w)) in the samples considered were in ranges favorable for S. aureus growth. As demonstrated by phenotypic and molecular characterization, in spite of the high percentage of coagulase-positive Staphylococcus strains, only three strains could be referred to the species S. aureus. Moreover, all the strains were negative in PCR assays targeting staphylococcal enterotoxin genes (seA to seE, seG to seJ, and seM to seO), as well as the toxic shock syndrome toxin 1 gene, and no SEA was detected in the retail breaded chicken samples analyzed by a reversed passive latex agglutination assay or by Western blotting. Hence, we evaluated the thermal resistance of two strains of SEA-producing S. aureus in a laboratory-scale preparation of precooked breaded chicken cutlets. The heat treatment employed in the manufacture determined the inactivation of S. aureus cells, but the preformed SEA remained active during product storage at 4 degrees C. The presence of the staphylococci and, in particular, of S. aureus in the retail breaded chicken products analyzed is a potential health risk for consumers since the pH and a(w) values of these kinds of products are favorable for S. aureus growth. The thermal process used during their manufacture can limit staphylococcal contamination but cannot eliminate preformed toxins.

Phenotypic and genotypic traits of Staphylococcus aureus strains isolated from pig carcasses

A total of 142 S. aureus strains isolated from pig carcasses from abattoirs A ( n = 98) and B ( n = 44) were characterized by phenotypic and genotypic traits. Phenotypically, 96% showed yellow-pigmented colonies, 63% β/δ hemolysis, 85% were egg yolk-positive and 99% were positive for clumping factor/protein A. Only 25% of the strains were resistant to the antimicrobials tested (abattoir A: 19%; abattoir B: 39%), especially to penicillin and ampicillin. None of the strains harbored the mecA gene, which is conserved in methicillin-resistant S. aureus. The biofilm associated genes icaA, icaD and bap were present in 100%, 100% and 0% of the strains. Genes for staphylococcal enterotoxin (SE) were detected in 51% (abattoir A) and 14% of the strains (abattoir B). Among strains harboring SE genes ( n = 56), 63%, 31%, 4% and 2% tested positive for seg/ sei, seg, sei and sec, respectively. The amplification of the 3′ end of the coagulase gene ( coa) yielded amplicons of 400, 436, 602, 682 or 776 bp. Coa restriction profile (CRP) analysis using HaeIII resulted in seven patterns (a–d, e1–e3). CRP (c) was detected most frequently at both abattoirs, whereas CRP (a) was restricted to abattoir A and CRP (e3) to abattoir B. In the slaughter process (abattoir B), (i) two CRPs (b and d) were only found before dehairing/singeing, and (ii) four CRPs (c, e1–e3) were identified throughout the process. The genotyping revealed a remarkable homogeneity in S. aureus strains from the two different abattoirs and the slaughter process stages. These results may be explained by the distribution of a limited number of S. aureus genotypes in the pig population. Moreover, as the predominant CRPs (c, e1–e3) persisted throughout the slaughter process in abattoir B, it may be hypothesized that these types are characterized by colonization advantages.

A Subset of Staphylococcus aureus Strains Harboring Staphylococcal Cassette Chromosome mec (SCC mec ) Type IV Is Deficient in CcrAB-Mediated SCC mec Excision

The gene encoding resistance to beta-lactam antibiotics in the staphylococci is found on the chromosome in a genomic island designated staphylococcal cassette chromosome mec, or SCCmec. In addition to the resistance gene mecA, SCCmec also contains site-specific recombinase genes that are capable of catalyzing the chromosomal excision and reintegration of SCCmec. SCCmec is found in five major isotypes partially defined by the recombinase genes present, either ccrAB or ccrC. Of these, SCCmec type IV is presumed to be mobile in the environment, and this mobility may be partially responsible for the rise in community-associated methicillin-resistant staphylococcal infections. In this study, we investigate the presumptive first step in type IV SCCmec mobility: chromosomal excision of the element. CcrAB from a panel of six Staphylococcus aureus and four Staphylococcus epidermidis strains were able to catalyze chromosomal excision of SCCmec types I and II, indicating that these proteins maintain recombinase activity despite varying by up to 3.7% at the amino acid level. Excision of type IV SCCmec was not universally seen, as a subset of S. aureus strains with type IV SCCmec did not excise their element. These strains are all highly related and represent a lineage of successful community-associated pathogens. In addition, the inability to excise SCCmec in these strains is associated with the insertion of a presumptive mobile element containing the gene for staphylococcal enterotoxin H (seh) immediately downstream of SCCmec on the chromosome. Acquisition of this mobile element, containing a known virulence gene, appears to have stabilized the chromosomal integration of the methicillin resistance gene in these strains.

Molecular analysis of Staphylococcus aureus isolates associated with staphylococcal food poisoning in South Korea

To investigate the molecular epidemiological study of Staphylococcus aureus from staphylococcal food poisoning (SFP) incidents in South Korea. Three hundred and thirty-two strains isolated from ten provinces between June 1999 and January 2002 were characterized by staphylococcal enterotoxin genes, toxic shock syndrome toxin 1 (tst) gene, and exfoliative toxin genes. Toxin genotypes were sea-seh (n=197), sea (n=51), sea-seg-sei (n=14), seg-sei (n=10), seb (n=10), seb-sed-seg-sei-sej (n=3), sea-seg-seh-sei (n=1), sea-seb (n=1), sea-sec (n=1), seg-sei plus eta (n=4), and sea-seg-sei plus tst (n=40). Most of the strains could be classified into three clusters of pulsed-field gel electrophoresis (PFGE) types A and B with coagulase type VII and type E with coagulase type IV. Of the ten sequence types (ST), ST1, ST59, and ST30 were frequently showed by multilocus sequence typing. The strain belonging to PFGE pattern A with sea-seh gene, coagulase VII, and ST1 was the most epidemic clone of SFP incidents in Korea.