耐甲氧西林金黄色葡萄球菌SCCmec分型及同源性研究

目的对下呼吸道标本中分离的耐甲氧西林金黄色葡萄球菌(MRSA)耐药机制、同源性及分子生物学分型进行研究,从分子水平了解其耐药特点,为临床用药提供参考依据。方法于2012年7月-2013年4月住院患者送检的下呼吸道标本中分离出金黄色葡萄球菌66株,常规方法进行分离鉴定,根据2013年CLIS规定检测其耐药性;PCR技术检测mecA基因,对其进行SCCmec分子生物学分型及耐消毒剂基因(qacA/B)检测;利用RAPD技术对其进行同源性分析。结果凝胶电泳结果表明,耐甲氧西林金黄色葡萄球菌SCCmec分子分型全部为ccrAB3型,mecA、qacA/B基因的携带率100.0%,并且同源性分析有5个克隆型。结论临床分离的下呼吸道标本耐甲氧西林金黄色葡萄球菌全部为ccrAB3型,并对普通消毒剂有相当程度的抗性;分离到的耐甲氧西林金黄色葡萄球菌中同源性分型不同菌株耐药率与其基因型之间存在有一定的关系,且这些菌株均为多药耐药株。     

Pulse-field gel electrophoresis typing of methicillin-resistant Staphylococcus aureus strains susceptible to aminoglycosides isolated from 1993 to 2002

Methicillin-resistant Staphylococcus aureus (MRSA) susceptible strains to aminoglycosides (AS-MRSA) have been increasingly isolated in the Albert Cheneiver Hospital during the past 10 years. The aim of this study was first, to analyse the genotypes and the profiles of resistance to antibiotics and second to compare the AS-MRSA with the MRSA resistant to gentamicin (GR-MRSA) and with MRSA resistant to kanamycin and tobramycin, but susceptible to gentamicin (GS-MRSA), previously studied in our laboratory. All the AS-MRSA consecutively isolated from clinical samples (carriage isolates excluded) from 01/01/1993 to 31/12/2002 (33 isolates) were typed by DNA macrorestriction. Their susceptibilities to other anti-staphylococcal drugs (erythromycin, lincomycin, tetracycline, rifampicin, fusidic acid and fosfomycin) were studied by the French standard disk method. The 33 strains showed a heterogeneous resistance to oxacillin and fell into five phenotypes. The main phenotype (51.5% of the AS-MRSA strains) was susceptible to the six antibiotics studied. DNA macrorestriction defined 24 genotypes (percentage similarity <80%). Among them 16 genotypes contained only one strain each, and none contained more than three isolates. Conversely the comparison with GR-MRSA and GS-MRSA isolated during the same period showed that the strains were not closely linked. The diversity of our isolates showed that it was not an epidemic phenomenon, in contrast to the results of similar studies. Our findings may be explained by the patients coming mostly from different hospital units. This work indicates the need for further studies on the genome, to determine whether AS-MRSA have derived from strains that occurred before aminoglycosides came into clinical use.     

Bovine mastitis Staphylococcus aureus: Antibiotic susceptibility profile,resistance genes and molecular typing of methicillin-resistant and methicillin-sensitive strains in China

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) infection in dairy animals is of great concern for livestock and public health. The aim of present study was to detect new trends of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) towards antibiotic susceptibility, resistance genes and molecular typing by methods of disc diffusion, multiplex PCR assay and multilocus sequence typing (MLST). A total of 219 S. aureus strains were isolated from bovine mastitis cases from six provinces of China, including 34 MRSA strains. The results revealed that more than 70% isolated strains showed resistance to various antibiotics, and multiple-drugs resistance to more than five categories of antibiotics was found more common. The ermC was the most prevalent resistance gene, followed by other genes; however, ermA was the least frequently detected gene. Twenty-eight mecA-negative MRSA and six mecA-positive MRSA strains were detected, and in which three strains were ST97-MRSA-IV, others were ST965-MRSA-IV, ST6-MRSA-IV and ST9-MRSA-SCCmec-NT. The mecA-negative MRSA strains were found resistant to most of the antibiotics, and harbored aac(6′)/aph(2′′), aph(3′)-III and tetM genes higher than MSSA strains. The resistance to most of the antibiotics was significantly higher in MRSA than in MSSA strains. The MLST profiles showed that these strains mainly belonged to CC5, CC398, CC121 and CC50 lineage, especially within ST97 and ST398, while some novel sequence types (ST2154, ST2165 and ST2166) were identified and deposited in the MLST database. This indicates that the resistance of S. aureus is becoming more complicated by changes in multi-drug resistance mechanism and appearance of mecA-negative MRSA isolates, and importantly, MRSA-IV strains in different MLST types are emerging.     

SICU环境与临床标本耐甲氧西林金黄色葡萄球菌的基因分型

目的了解上海某三级综合医院外科重症监护病房(SICU)环境及临床标本耐甲氧西林金黄色葡萄球菌(MRSA)的基因特征。方法收集2012年1-7月SICU患者标本中的MRSA,以及同期SICU环境标本中分离到的MRSA,对菌株进行常用药物的MIC检测、脉冲场凝胶电泳(PFGE)和SCCmec分型。结果 PFGE共得到7个不同型别,以E型为主要型别,24株占50.0%,包括源自临床感染标本17株和环境标本7株;SCCmec分型为Ⅱ型17株占35.4%、Ⅲ型27株占56.2%、Ⅳ型2株占4.2%、Ⅴ型2株占4.2%,未检测到Ⅰ型菌株;药敏结果显示,Ⅱ型和Ⅲ型菌株对环丙沙星、克林霉素、红霉素、庆大霉素和青霉素耐药率为100.0%,Ⅱa型菌株对磺胺甲噁唑/甲氧苄啶均敏感,Ⅲ型菌株对利福平的耐药率为4.3%;Ⅳ和Ⅴ型菌株对常见抗菌药物的耐药率较低。结论该医院的SICU临床菌株以SCCmecⅢ型和Ⅱ型为主,环境与患者之间存在明显的MRSA克隆同源。     

青岛地区医院内感染耐甲氧西林金黄色葡萄球菌分子分型研究

目的 探讨青岛地区医院内感染的耐甲氧西林金黄色葡萄球菌(MRSA)分子流行病学特征及脉冲场凝胶电泳(PFGE)型别与菌株表型、一般临床资料间的关系.方法 收集2003-2007年间青岛地区主要医院内感染MRSA 360株,Sma Ⅰ酶切菌株染色体DNA后,进行PFGE电泳,用Bionumericus 2.0软件对电泳图谱进行比较和聚类分析,绘制进化树.同时对患者的性别、年龄、菌株来源等进行多变量统计分析.应用纸片扩散法测定分离菌株的药物敏感谱,并与PFGE型别进行比较分析.PCR扩增不同PFGE型别MRSA代表株25株分离株的7个管家基因进行序列测定和多位点测序分型分析(MLST).结果 所有菌株经PFGE电泳后共分为5型(M0～M4型),其中M1型为优势菌型,M2型次之,M4型相对少见,M0为独特型,明显不同于其他已知PFGE型别.统计学分析发现5种PFGE型别在患者性别、年龄分布上的差异无统计学意义,但在菌株分离部位、来源有统计学的差异:M2型多分离自伤口感染,而M3型菌株多来自ICU病房,5种PFGE型在不同医院间及医院内的分布存在差异.M1与M2两型构成各医院分离菌株的主要型别.抗生素敏感性测定中未发现万古霉素耐药菌株,亦未发现某种PFGE型别与某种特定抗生紊抗性之间的直接相关性.MIST分型发现优势型M1与M3共属于国内常见ST239型,M2型则归类于ST5,M4型属于ST240,独特型中的2种PFGE谱型则分属于ST45及ST398.结论 ST239菌株为青岛地区医院内感染MRSA优势菌株;医院内MRSA的PFGE分型与菌株来源明显相关,与患者年龄、性别无关,MRSA感染普遍存在于各年龄人群中.     

重症监护室MRSA耐药性及RAPD分析

目的:调查重症监护室耐甲氧西林金黄色葡萄球菌的耐药及分子流行病学情况,为控制感染提供科学依据。方法:ICU分离的金黄色葡萄球菌采用mecA基因检测法确定MRSA,对筛选出的MRSA采用纸片法检测其耐药性,用随机扩增多态性DNA(RAPD)进行分子流行病学分析。结果:MRSA的分离率为58.5%,对多种抗生素均耐药,没有发现耐万古霉素和替考拉宁的菌株。24株MRSA经RAPD分型,均获得稳定的条带,可分为四型,以Ⅱ型为主,共检出15株。结论:ICU分离MRSA菌株具有多重耐药性,应根据药敏试验结果合理选用抗生素进行治疗;通过RAPD分型研究,可了解MRSA的基因型流行特征,为控制感染提供分子流行病学依据。     

Enterotoxin production, phage typing and serotyping of Staphylococcus aureus strains isolated from clinical materials and food

The production of enterotoxins A, B, C and F by strains of Staphylococcus aureus isolated from various clinical sources and from isolates implicated in food poisoning was investigated. One hundred and ninety one of the 374 clinical strains (51.1%) were found to be enterotoxigenic; of these, 81 (27.7%) strains produced enterotoxin A, 57 (15.3%) strains produced enterotoxin B, 23 (6.2%) strains produced enterotoxin C, and 64 (17.1%) strains produced enterotoxin F. These enterotoxigenic strains were most frequently lysed by phages of group III (21.5%) or were not typable (22%). Eighteen of the 29 strains implicated in food poisoning were enterotoxigenic. The correlation of antigens and bacteriophage patterns with enterotoxigenicity was determined: enterotoxin A being related to a4 antigen, enterotoxin B to phages of 94/96 complex with c1, o antigens, and enterotoxin F to phages of group I with 2632, k1k2, m antigens.     

Enterotoxin production, phage typing and serotyping of Staphylococcus aureus strains isolated from clinical materials and food.

The production of enterotoxins A, B, C and F by strains of Staphylococcus aureus isolated from various clinical sources and from isolates implicated in food poisoning was investigated. One hundred and ninety one of the 374 clinical strains (51.1%) were found to be enterotoxigenic; of these, 81 (27.7%) strains produced enterotoxin A, 57 (15.3%) strains produced enterotoxin B, 23 (6.2%) strains produced enterotoxin C, and 64 (17.1%) strains produced enterotoxin F. These enterotoxigenic strains were most frequently lysed by phages of group III (21.5%) or were not typable (22%). Eighteen of the 29 strains implicated in food poisoning were enterotoxigenic. The correlation of antigens and bacteriophage patterns with enterotoxigenicity was determined: enterotoxin A being related to a4 antigen, enterotoxin B to phages of 94/96 complex with c1, o antigens, and enterotoxin F to phages of group I with 2632, k1k2, m antigens.     

Epidemiologic and clinical utility of typing systems for differentiating among strains of methicillin-resistant Staphylococcus aureus.

Typing systems for differentiating among strains of methicillin-resistant Staphylococcus aureus (MRSA) can be valuable tools for the epidemiologist and the clinician. Specific criteria for evaluating such systems are typeability, reproducibility, and discriminatory power. An ideal typing system also would be rapid, inexpensive, technically simple, and readily available. Systems based on the detection of phenotypic variations include antimicrobial susceptibility testing, bacteriophage typing, multilocus enzyme electrophoresis, and electrophoretic methods such as protein electrophoresis and immunoblotting. Systems that directly detect genotypic variations include plasmid profile analysis, restriction enzyme analysis of plasmid DNA, restriction enzyme analysis of chromosomal DNA, Southern blot analysis of specific restriction fragment length polymorphisms, and pulse field gel electrophoresis. In general, the more widely available typing systems based on phenotypic assays and plasmid analysis have limitations in typeability and/or discriminatory power. The chromosomal DNA-based techniques, although promising, are unproven approaches still under active investigation.     

金黄色葡萄球菌婴幼儿分离株黏附毒素与细胞毒素编码基因研究

目的调查金黄色葡萄球菌婴幼儿分离株的黏附毒素与细胞毒素编码基因携带状况。方法收集儿童医院2013年10-12月金黄色葡萄球菌婴幼儿分离株20株,采用聚合酶链反应(PCR)的方法分析9种黏附毒素编码基因、9种细胞毒素编码基因及2种荚膜抗原编码基因。结果 20株金黄色葡萄球菌共检出7种黏附毒素编码基因,5种细胞毒素编码基因,荚膜抗原编码基因cap5占15.0%、cap8占85.0%;黏附毒素、细胞毒素及荚膜抗原3类编码基因每一株均有阳性检出;阳性基因可分为7种模式,携带≥10种基因的菌株占大多数。结论黏附毒素和细胞毒素编码基因的高检出率是该组金黄色葡萄球菌在患儿皮肤软组织和病灶部定植和感染的重要原因,对金黄色葡萄球菌婴幼儿分离株进行9种黏附毒素编码基因、9种细胞毒素编码基因及2种荚膜抗原编码基因检测研究尚为国内外首次。     

Multiply- and methicillin-resistant Staphylococcus aureus strains isolated in the German Democratic Republic in 1985 and 1986

Multiply- and methicillin-resistant Staphylococcus aureus (MRSA) strains have been isolated from five small outbreaks of nosocomial infection in five different hospitals. The MRSA were typed by phage patterns, biochemical traits, resistance phenotypes and plasmid patterns. Three different groups of strains can be distinguished. The MRSA from three outbreaks in one country share identical characters. Phage typing by the use of the International Basic Set for Phage Typing staphylococci as well as experimental phages does not completely discriminate between the strains. Attribution of several resistance determinants to plasmids in two of the described strain groups proved valuable for strain differentiation. These multiply-resistant strains are sensitive to vancomycin and to rifampicin.     

Prevalence of icaA and icaD genes in Staphylococcus aureus and Staphylococcus epidermidis strains isolated from patients and hospital staff

Staphylococci are ubiquitous microorganisms that predominate in normal skin and mucosal flora. Staphylococcus aureus and Staphylococcus epidermidis have been identified as a major cause of nosocomial infections, especially in patients with predisposing factors such as indwelling or implanted foreign bodies. The ability of both S. epidermidis and S. aureus to produce biofilm was compared between 116 clinically significant strains (46 from blood cultures of patients with bloodstream infection and 70 isolated from catheters) and 60 strains isolated from nasal swabs of healthy carriers from hospital staff. The presence of the intercellular adhesion genes (icaA and icaD) was determined by the Polymerase Chain Reaction method, and slime production was examined using qualitative Congo red agar technique. Among clinical strains, 35.2% (19/54) of S. aureus and 48.4% (30/62) of S.epidermidis were both positive icaA and icaD and they produced slime. Among carrier strains, 22.2% (8/36) of S. aureus and 33.3% (8/24) of S. epidermidis were positive for slime synthesis and exhibited ica genes. Our results suggest that the virulence factors contributing to the development of infections can be present in patient and hospital staff isolates. Thus, we consider it is important to detect healthy carriers of slime-producing staphylococci and to control the dissemination of these microorganisms especially in a hospital.     

Biofilm formation by and accessory gene regulator typing of methicillin-resistant Staphylococcus aureus strains recovered from patients with nosocomial infections.

The association between biofilm formation and the accessory gene regulator (agr) types of methicillin-resistant Staphylococcus aureus (MRSA) strains in our hospital were investigated. The biofilm index and the incidence of MRSA strains carrying agr-2 in the infection group (n=91) were significantly higher than were those in the carrier group (n=225), suggesting that biofilm formation and agr type are associated with nosocomial MRSA infections.     

Molecular epidemiology of methicillin-resistant Staphylococcus aureus in nursing homes: a cross-sectional study.

A cross-sectional study of methicillin-resistant Staphylococcus aureus carriage in 2,857 nursing home residents showed an overall prevalence of 4.9%. The three clones identified by genetic analysis were identical to those in the acute care facilities; only their relative prevalence differed. Clone 2 took epidemic proportions in five of these nursing homes.     

Molecular fingerprinting of meticillin-resistant Staphylococcus aureus strains isolated from patients and staff of two Iranian hospitals

Meticillin-resistant Staphylococcus aureus (MRSA) is an important cause of hospital-acquired infection. Methods for typing and epidemiological investigation of MRSA isolates have an important impact in detection of MRSA strains, source, transmission and control of these micro-organisms. The aims of this study were to study molecular diversity of MRSA isolates by randomly amplified polymorphic DNA (RAPD)-polymerase chain reaction (PCR), the surveillance efficacy of this method and determination of antibiotic resistance patterns of MRSA isolates. MRSA isolates were collected from clinical specimens and noses of 460 staff and inpatients admitted to Imam Khomeini and Paediatric Hospitals during a six-month period (2004-2005). Eighty MRSA strains, in which the presence of mecA gene had been confirmed by PCR, were subjected to RAPD-PCR using five primers and the results were summarised in a dendrogram to show the relationships between the test isolates. Antibiotic resistance patterns of MRSA isolates were also determined by disc agar diffusion method using 13 antibiotic discs according to Clinical and Laboratory Standards Institute guidelines. Forty-three RAPD-PCR profiles were detected. The test isolates were clustered into 18 taxa with 50% similarity, indicating the heterogeneity of our test isolates. MRSA isolates fell into 41 antibiotic resistance patterns. There was correlation between antibiotic resistance patterns and results of RAPD-PCR. Most of the MRSA isolates were multi-resistant.     

Comparative pulsed-field gel electrophoresis typing of gentamicin-resistant and -susceptible methicillin-resistant Staphylococcus aureus strains isolated in France between 1991 and 1998. Changes in antibiotic susceptibility

Using macrorestriction of genomic DNA and pulsed-field gel electrophoresis, we examined 504 non-redundant, infection-causing human isolates of methicillin-resistant Staphylococcus aureus susceptible (G(S): 238 isolates) or resistant to gentamicin (G(R): 266 isolates). The strains were isolated at Albert Chenevier Hospital (Créteil, France) between 1 January 1991 and 31 December 1998. Their susceptibility to erythromycin, lincomycin, tetracycline, rifampicin, fusidic acid and fosfomycin was also studied. Seventy-six genotypes were identified (percentage similarity<80). Ten types, each containing at least eight strains, predominated. G(R) strains showed higher genetic polymorphism than G(S) strains: the 266 G(R) isolates belonged to 67 genotypes, five of which predominated (44, 42, 38, 30 and 15 isolates); the 238 G(S) isolates belonged to only 18 types, four of which predominated (112, 83, 11 and 10 isolates). Fifty-six percent of G(R) strains (34 Gt) were resistant to erythromycin, lincomycin, tetracycline and rifampicin, and were isolated at relatively stable frequencies. Resistance to five antibiotics studied (susceptible to fusidic acid) was observed among 16.5% of G(R) strains. The frequency of strains with this profile diminished from 30% in the early 1990s to 10% in 1998. One hundred and twenty-six G(S) isolates were susceptible to all six antibiotics; this profile was only found from 1993 onwards, and was increasingly frequent (60% of G(S) strains in 1996). Resistance to erythromycin and lincomycin only was found in 70 G(S) isolates; this profile accounted for approximately half the isolates in 1992/1993 and only one-third in 1998. These results, obtained over an eight-year period, show an overall increase in antibiotic susceptibility. They confirm the spread of two major clones of MRSA-G(S) and support the hypotheses that G(S) strains derive from G(R) strains that have lost the aac6'-aph2" gene; and that G(S) strains are genetically related to those that were present before the use of gentamicin and persisted at a low frequency until 1992-1993.     

Analysis of methicillin-resistant and methicillin-susceptible Staphylococcus aureus by a molecular typing method based on coagulase gene polymorphisms.

A molecular typing method for Staphylococcus aureus based on coagulase gene polymorphisms (coagulase gene typing) was evaluated by examining a total of 240 isolates which comprised 210 methicillin-resistant S. aureus (MRSA) and 30 methicillin-susceptible S. aureus (MSSA) collected from a single hospital. By AluI restriction enzyme digestion of the PCR-amplified 3''-end region of the coagulase gene including 81-bp repeated units, the MRSA and MSSA isolates examined were divided into 6 and 12 restriction fragment length polymorphism (RFLP) patterns, respectively, whereas five patterns were commonly detected in MRSA and MSSA. MRSA isolates that showed a particular RFLP pattern were considered to be predominant in the hospital. Coagulase typing with type-specific antisera was also performed for all S. aureus isolates for comparison. Coagulase types II and VII were most frequently detected and included isolates with four and five different AluI RFLP patterns, respectively, whereas each of the other coagulase types corresponded to a single RFLP pattern. These results indicated that RFLP typing was more discriminatory than serological typing, for typing S. aureus and demonstrated its utility in epidemiologic investigation of S. aureus infection in hospitals.     

Genotypic screening of atypical Staphylococcus aureus strains isolated from clinical samples for presence of selected adhesin genes

Objective

The aim of this study was to screen Staphylococcus aureus negative for production of coagulase or clumping factor and for presence of selected adhesin genes.

Methods

Sixty coagulase-negative and 20 clumping factor-negative S. aureus strains were studied. Detection of methicillin resistance was performed using the agar screen technique with 6 mg/L of oxacillin and was confirmed by amplification mec A gene. The presence of bone binding protein (bbp), collagen binding protein (cna), fibronectin A binding protein (fnbA), fibronectin B binding protein (fnbB) and clumping factor A (clfA) genes was detected by multiplex PCR.

Results

Almost all (98%) of the strains were positive for clfA gene. There were fnbA and fnbB in 85%, cna in 54% and bbp in 5% of strains found. No correlation between presence of the particular genes and clinical samples was observed. The prevalence of fnbA, fnbB and cna was statistically higher in coagulase-negative than in clumping factor-negative strains (89, 89, 66 and 70, 70, 15%, respectively). Similarly, all of these genes were more often observed in MRSA than in MSSA atypical strains. The cna was detected only in coagulase-negative MRSA.     

市售生鲜肉食品中金黄色葡萄球菌基因分型与毒素基因检测

【目的】了解市售生鲜肉中金黄色葡萄球菌的污染、群体遗传多样性和毒素基因携带规律,为金黄色葡萄球菌的污染防控提供依据。【方法】按照GB4789.10—2016对金黄色葡萄球菌进行分离鉴定,采用多位点序列分型方法(MLST)进行分子分型,利用PCR方法检测11种毒素基因的携带情况。【结果】148份样品中有56份检出金黄色葡萄球菌,污染率为30.1%,分离到56株菌。56株菌可分成11种序列型(STs),其中ST7(28.6%)是主要流行的序列型,其他优势序列型分别为ST188(23.2%),ST1(8.93%)和ST88(8.93%)。6种毒素基因在27株菌(48.2%)中检出阳性结果,其中杀白细胞素基因pvl(26.8%)检出率最高,其次为肠毒素基因sec(12.5%),seh(10.7%),sea(7.1%)和sed(5.4%)。【结论】金黄色葡萄球菌在市售生鲜肉中具有较高的污染率,丰富的遗传多样性表明菌株污染来源广泛,与食物中毒和临床感染相关的毒素基因具有较高的分布比例,应加强对生鲜食品中金黄色葡萄球菌的监控。     

Prevalence of enterotoxin and toxic shock syndrome toxin genes in Staphylococcus aureus isolated from milk of cows with mastitis

Staphylococcus aureus isolated from milk of cows with mastitis were evaluated for the prevalence of 16 enterotoxin genes (sea-see and seg-seq) and toxic shock syndrome toxin gene (tsst-1). Of 78 S. aureus examined, 73 (93.6%) were positive for one or more enterotoxin genes and these were divided into 36 groups by the presence of different enterotoxin genes. Enterotoxin genes including sen (84.6%), sem (71.8%), sei (60.3%) and sed (52.6%) were found frequently, while seg (24.4%), seq (16.7%), seo (12.8%), and seb (1.3%) were found at lower frequencies. Toxic shock syndrome toxin (tsst-1) gene was detected in 20 (25.6%) isolates and was always found in combination with other enterotoxin genes. The majority (88.5%) harbored more than one enterotoxin gene in different combinations. Eight S. aureus isolates (10.3%) were positive for sed, sei, sem, and sen; six (7.7%) possessed sed, seg, sei, sem, sen, and tsst-1; five (6.4%) had sei, sem, and sen; and four (5.1%) had sei, and sen. One isolate was positive for seb along with other SE genes including sed, seh, sem, sen, seq, and tsst-1. None of the isolates carried other enterotoxin genes (sea, sec, see, sej, sek, sel, and sep). PFGE profiles revealed 15 distinct pulsotypes among the 78 S. aureus isolates evaluated. PFGE and enterotoxin gene profiles did not match with each other because a single pulsotype carried different combinations of enterotoxin genes. The majority of S. aureus isolated from milk of mastitic cows carried newly described SE genes sem, sen and sei along with classical SE genes, sed and tsst-1. This is the first report describing the high prevalence of newly described enterotoxin genes, sem and sen in S. aureus from bovine mastitis. The high prevalence of enterotoxin genes and tsst-1 in S. aureus may be important as it is relevant to udder pathogenicity and food hygiene.