Emergence and characterization of foodborne methicillin-resistant Staphylococcus aureus in Korea

A total of 165 Staphylococcus aureus strains, isolated from different food samples between 2003 and 2006, were tested for antimicrobial susceptibility. The mecA-positive methicillin-resistant S. aureus (MRSA) strains were further characterized by testing for various virulence genes and by molecular typing with multilocus sequence typing and pulsed-field gel electrophoresis. Of the 165 S. aureus isolates, 150 strains (90.9%) were resistant to at least one antibiotic while no strain was resistant to vancomycin. Four strains were resistant to both oxacillin and cefoxitin and were mecA positive. The mecA-positive MRSA strains were isolated from raw meat and fish samples (two beef samples and two fish samples) and were resistant to β-lactam antibiotics. Based on multilocus sequence typing analysis, the isolates were assigned to sequence type 1 (ST1), ST72, and an undetermined ST (ST72 slv). All four MRSA isolates were shown to be enterotoxigenic. The ST1 MRSA isolate harbored the sea-seh gene combination and the ST72 and ST72 slv MRSA strains harbored the seg-sei and the sea-seg-sei gene combinations, respectively. However, none of the MRSA isolates had the genes for Panton-Valentine leukocidin, toxic shock syndrome toxin 1, and exfoliative toxins. The pulsed-field gel electrophoresis patterns of the ST72 isolates in our study were highly similar, even though they were isolated from food samples in different years and from different regions of Korea.     

Antimicrobial susceptibility of Staphylococcus aureus from retail ground meats

The aim of this study was to characterize antimicrobial resistance in Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), recovered from raw retail meat products purchased in the Washington, D.C., area. From March to August 2008, 694 samples of ground beef (n = 198), ground pork (n = 300), and ground turkey (n = 196) were collected by random sampling from stores of three grocery chains. In total, 200 S. aureus isolates (29%) were recovered by direct plating. When tested for susceptibility to 22 antimicrobials, 69% of the S. aureus isolates were resistant to tetracycline, 26% to penicillin, 17% to ampicillin, 13% to methicillin, 8% to erythromycin, 4.5% to clindamycin, 1.5% to gentamicin, and 0.5% to chloramphenicol, oxacillin, cefoxitin, or quinupristin-dalfopristin. However, 27% of the isolates were susceptible to all tested antimicrobials. More turkey and pork isolates were resistant to ampicillin, penicillin, and tetracycline than were beef isolates (P < 0.05). Additionally, 17% of the turkey and 17% of the pork isolates were resistant to methicillin (MIC ≥ 16 μg/ml), whereas no beef isolates were resistant to the antimicrobial agent. A single MRSA (methicillin MIC > 32 μg/ml) isolate containing the mecA gene with additional resistance to erythromycin, clindamycin, oxacillin plus 2% NaCl, cefoxitin, ampicillin, penicillin, quinupristin-dalfopristin, tetracycline, and gentamicin was recovered from one pork sample. The presence of antimicrobial-resistant S. aureus, coupled with the relative lack of such studies in the United States, suggests that further investigations on MRSA in the food supply are needed despite the low rate of MRSA found in this particular study.     

Beef carcass contamination in a slaughterhouse and prevalence of resistance to antimicrobial drugs in isolates of selected microbial species

Meat contaminating bacteria may be the direct cause of foodborne diseases and represent a potential cause for the drug resistance of human pathogenic agents. The prevalence and resistance to 17 antimicrobial drugs of isolates of selected bacterial species were investigated in 70 swabs of beef carcasses and 70 subsequent samples of beef meat. Molecular techniques (coagulase gene typing Staphylococcus aureus and original gene typing Escherichia coli) were used in the differentiation of isolates. Carcasses were already contaminated after evisceration, least frequently with S. aureus strains (7.5% of samples), most frequently with coagulase-negative staphylococci strains (52.2% of samples). During carcass processing, contamination with resistant or polyresistant strains of S. aureus and E. coli significantly increased (P<0.01). Gene typing isolates of S. aureus and E. coli indicated that the strains probably originated in the processing plant.     

2009-2018年广州市即食食品中金黄色葡萄球菌污染情况和菌型特征

目的 分析2009-2018年广州市零售即食食品中金黄色葡萄球菌污染情况,以及菌株肠毒素基因、耐药表型特征.方法 从广州市辖11个区的农贸市场、超市随机购买零售即食食品,增菌后分离金黄色葡萄球菌.对所有菌株进行多位点序列分型(MLST)、抗生素敏感性试验,并检测24种肠毒素基因.对耐甲氧西林金黄色葡萄球菌(MRSA)进...     

Occurrence and characteristics of methicillin-resistant and -susceptible Staphylococcus aureus and methicillin-resistant coagulase-negative staphylococci from Japanese retail ready-to-eat raw fish

Staphylococci are not part of the normal fish microflora. The presence of staphylococci on fish is an indication of (a) post-harvest contamination due to poor personnel hygiene, or (b) disease in fish. The aim of this study was to determine the prevalence, molecular genetic characteristics, antibiotic resistance and virulence factors of methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) isolated from 200 samples of retail ready-to-eat raw fish (sashimi) collected from the Japanese prefecture of Hiroshima. We characterized 180 staphylococcal strains. A majority of the grocery stores surveyed (92%, 23/25) contained fish contaminated with Staphylococcus species. We recovered 175 S. aureus isolates from 174 (87%, 174/200) samples, with 170 isolates of MSSA. For the MRSA and MR-CoNS, 10 isolates were obtained from 10 samples (5%, 10/200) collected from 10 shops (40%, 10/25) belonging to four supermarket chains. SCCmec typing revealed the presence of a type IV.1 SCCmec cassette in S. warneri isolates, a type II.1 SCCmec cassette in S. haemolyticus isolates and a cassette in methicillin-resistant S. aureus (MRSA) isolates that could not be typed. Molecular typing of two MRSA isolates by spa sequencing and multilocus sequence typing (MLST) identified t1767 and ST8, respectively. Antibiotic resistance genes that confer resistance to aminoglycosides, tetracyclines, β-lactams, macrolides, lincosamides and streptogramin B (MLS(B)) antibiotics were detected. Genes encoding one or more of the following virulence factors: staphylococcal enterotoxins (seb, and sed), toxic shock syndrome toxin 1 (tst), exfoliative toxin (etaA) were detected in 14.2% (25/175) of S. aureus isolates. The accessory gene regulator (agr) typing of S. aureus isolates revealed that agr type 1 was most prevalent (96.5%, 169/175) followed by type 2 (2.2%, 4/175) and type 3 (1.1%, 2/175). None of the S. aureus isolates carried the Panton-Valentine leucocidin (PVL) encoding genes, lukF-PV and lukS-PV. To the best of our knowledge, this is the first report to show MRSA and MR-CoNS isolated from retail ready-to-eat food in Japan. Our results showed that sashimi is a likely vehicle for transmission of multidrug-resistant and toxigenic staphylococci.     

Antimicrobial susceptibilities and epidemiological analysis of Salmonella enteritidis isolates in Korea by phage typing and pulsed-field gel electrophoresis

A total of 81 isolates of Salmonella Enteritidis were analyzed by antibiotic susceptibility, phage typing, and pulsed-field gel electrophoresis (PFGE). Thirty-two isolates came from broiler carcasses and pig feces, and 49 isolates were from humans in Seoul and suburbs of Seoul, Korea. Antibiotic resistance was most prevalent among human isolates. Of human isolates, 89.8% were resistant to more than two antibiotics, while 64.7% of poultry isolates and 13.3% of pig isolates showed multiple resistance to more than two antibiotics. The most common phage type (PT) was PT1, followed by PT30 or 33, PT21 and PT20a. The isolates showed six PFGE patterns with XbaI or SpeI digestion, and five PFGE patterns with NotI digestion. But a single pattern, PFGE X1, S1, or N1, was predominant and the rest of the PFGE patterns differed by only one or two bands. Results indicated the spread of a genetically related clone of Salmonella Enteritidis in foods and humans in Korea and that phage typing as well as PFGE may offer an improved level of discrimination for the epidemiological investigation of Salmonella Enteritidis.     

Comparison of virulence and antibiotic resistance genes of food poisoning outbreak isolates of Staphylococcus aureus with isolates obtained from bovine mastitis milk and pig carcasses

Staphylococcus aureus is the etiological agent in a variety of infections in humans and livestock and produces enterotoxins leading to staphylococcal food poisoning (SFP), one of the most prevalent foodborne intoxication diseases worldwide. Pork and bovine milk are considered possible sources of SFP because pig skin is often colonized by S. aureus and bovine mastitis caused by S. aureus is common, but conclusive data are limited. The objective of the present study was to compare S. aureus isolates associated with cases of SFP with isolates obtained from bovine mastitis milk and pig carcasses. DNA microarray analysis and spa gene typing were performed with 100 S. aureus isolates: 20 isolates related to outbreaks of SFP in humans, 39 isolates obtained from pig carcasses, and 41 isolates collected from bovine mastitis milk. No overlap in spa types was observed for SFP isolates (t008, t015, t018, t024, t056, t084, t279, t377, t383, t648, t733, t912, t1239, t1270, t4802, and t6969) and isolates gathered from milk or pork. The porcine isolates were assigned to t034, t208, t337, t524, t899, t1939, t2922, t2971, t4475, and t7006, and the bovine isolates belonged to t267, t524, t529, t1403, t2953, t7007, t7008, and t7013. Comparison of microarray profiles revealed similar virulence gene patterns for isolates collected from the same host (pigs or cattle) but few similarities between SFP isolate profiles and the profiles of isolates obtained from bovine mastitis milk and pig carcasses. Although only some bovine and porcine isolates possessed the β-lactamase gene blaZ (milk, 24%; pork, 28%), significantly higher numbers of SFP isolates contained blaZ (90%). Investigations of these isolates provided no evidence that pork or bovine mastitis milk represent common sources of SFP.     

现制饮品中金黄色葡萄球菌耐药及遗传特征研究

目的 探究我国现制饮品中金黄色葡萄球菌抗生素耐药及遗传特征。方法 采用微量肉汤稀释法对金黄色葡萄球菌进行药敏测定,同时提取菌株基因组DNA进行全基因组测序,并使用生物信息学分析流程进行基因组特征数据挖掘。结果 现制饮品中43株金黄色葡萄球菌对10种抗生素的总体耐药率为88.4%,分属9种耐药谱,其中3株为耐甲氧西林金黄色葡萄球菌（Methicillin-resistant Staphylococcus aureus,MRSA）。多重耐药菌（Multidrug resistant,MDR）占比16.3%,主要为含乳现制饮品。耐受7类及以上抗生素金黄色葡萄球菌3株,其中1株为MRSA。全基因测序进化分析表明菌株耐药表型与基因型具有良好的相关性,MRSA及多重耐药株出现明显聚集。43株菌属于16种多位点序列分型（multilocus sequence typing,MLST）,其中MRSA菌株包括1株ST45型和2株ST398型。多重耐药株ST型别为ST5、7、15、59、121和398型。多重耐药MRSA株为ST398型。金葡肠毒素基因整体携带率为34.9%,其中sea为主要基因型。MRSA菌株均不携带毒力基因,多重耐药株肠毒素基因携带率为42.9%。3株主要来自含水果类现制饮品的ST1型菌株同时携带6种肠毒素基因,但其仅对青霉素耐药或为敏感株。结论 我国现制饮品中金黄色葡萄球菌存在MRSA及多重耐药菌,且该类菌株在遗传进化中聚类明显,虽然MRSA菌株致病性相对较弱,然而MDR菌株肠毒素基因的高携带率提示耐药金黄色葡萄球菌的潜在危害不容忽视。因此,应加强现制饮品中金黄色葡萄球菌的耐药监测与防控。     

成都市生鲜猪肉MRSA分离株的流行特征分析

目的：分析成都市各地区生鲜猪肉样品中耐甲氧西林金黄色葡萄球菌（Methicillin-resistant Staphylococcus aureus,MRSA）的流行特征。方法：对鉴定出的MRSA菌株进行SCCmec分型、spa分型以及多位点序列（MLST）分型分析,同时运用PCR技术对MRSA菌株携带的多种毒力基因、生物被膜形成相关基因、耐消毒剂基因以及耐药基因进行检测,并采用K-B纸片扩散法调查MRSA菌株的耐药表型。结果：本研究从297株猪肉源金黄色葡萄球菌中筛选出24株MRSA菌株,分离率为8.08%。MRSA菌株主要以ST88-IVa-t1376、ST59-IVa-t437和ST9-IVb-t3433型为主,携带耐药基因3~7个;所有菌株均表现出对氨苄西林和青霉素G耐药,并且存在多重耐药情况;分离菌株携带多种肠毒素基因,其中MRSA8和MRSA13菌株携带了完整的egc基因簇;MRSA分离菌株均携带clfB、eno、icaBC和sasG等生物被膜形成相关基因;携带耐消毒剂基因（qacA/B、qacC和qacG）的菌株占比为62.5%,其中以qacG为主要携带基因类型。另外,79.17%的MRSA菌株携带溶血素基因（hla、hlb）,所有菌株中杀白细胞素基因（pvl）均未检出。结论：成都市猪肉源MRSA的流行可能存在一定的交叉污染,应加强动物源食品携带MRSA菌株的监测。     

Resistance patterns of Campylobacter spp. strains isolated from poultry carcasses in a big Swiss poultry slaughterhouse

The aim of this study was to determine resistance patterns of strains of Campylobacter spp. isolated from poultry carcasses in one of the two big Swiss poultry slaughterhouses. A variety of antibiotics with clinical relevance in human and/or in veterinary medicine was tested. In addition, the results of the disc diffusion method, E-test and microdilution broth methods were compared. Of the 195 Campylobacter jejuni strains isolated from 195 poultry carcasses from 21 flocks, 134 strains were susceptible in vitro to all tested antibiotics. Sixty-one strains (31.3%, from eight flocks) showed resistance. Forty-one strains were resistant to a single antibiotic-34 to streptomycin, 6 to ampicillin and 1 to ciprofloxacin. Eighteen strains (from two flocks) showed combined resistance to erythromycin and streptomycin, two strains to ciprofloxacin and streptomycin. None of the isolates was resistant to tetracycline. The data of this first study in Switzerland show a favourable resistance situation for C. jejuni strains against erythromycin, tetracycline and ciprofloxacin. The disc diffusion method was found to be a reliable and easy tool for monitoring the prevalence of resistant C. jejuni strains. For surveillance of changes in the susceptibility concentration levels to antimicrobial agents, however, a MIC method should be used. Further investigations along the whole poultry production chain (farm, slaughterhouse and retail levels) are now necessary in order to confirm the resistance situation.     

广州市售生猪肉中金黄色葡萄球菌检测及其耐药性研究

了解广州市某区猪肉中金黄色葡萄球菌的污染情况、分子分型及其耐药性特征。根据GB 4789.10-2010对样品进行金黄色葡萄球的分离及鉴定,用多位点序列分型法进行分子分型,纸片扩散法进行抗生素敏感试验,采用PCR法验证MRSA并筛选检测I类整合子及相关耐药基因盒。110份生猪肉样品中有34份样品检出金黄色葡萄球菌(30.9%),得到34株该菌,所有菌株共可分成7种序列分型(sequence types,STs),分别为ST6(1/34)、ST7(16/34)、ST9(9/34)、ST59(1/34)、ST239(4/34)、ST2259(2/34)及一株等位基因谱为5-4-1-4-4-6-53的新型ST,34株金黄色葡萄球菌对12种抗生素耐药率分别为对青霉素100%耐药,对四环素、甲氧苄胺嘧啶、红霉素、克林霉素的耐药率分别为88.2%、76.5%、64.7%、61.8%,MRSA检出率为38.3%(13/34),I类整合子的检测率为14.7%(5/34),其中2株菌携带相应基因盒。本次实验显示生猪肉中金黄色葡萄球菌污染比较严重且具有严重的抗生素耐药现象,ST7为主要的序列型号,I类整合子存在于食源性金黄色葡萄球菌中,相关基因盒对菌株耐药发挥作用。     

Diversity of Campylobacter isolates from retail poultry carcasses and from humans as demonstrated by pulsed-field gel electrophoresis

Campylobacter spp. are a major contaminant of poultry. Eating undercooked chicken and handling raw poultry have been identified as risk factors for campylobacteriosis in humans. Previous studies have found Campylobacter spp. on 90% of poultry carcasses. In the present study, pulsed-field gel electrophoresis (PFGE) was used to assess the genetic diversity of strains on retail poultry carcasses. PFGE patterns of isolates from campylobacteriosis cases were compared to those from the poultry isolates. Over a 1-year study period (March 2000 through February 2001), whole fresh young chickens (n = 72) were obtained from three retail outlets in an urban community in the south-central United States. Campylobacter spp. were isolated from 82% of these carcasses. Strains (n = 70) were defined on the basis of their PFGE pattern. Sixty-seven percent of the carcasses from which Campylobacter spp. were isolated were contaminated with more than one PFGE-distinguishable strain. During the 1-year study period, most of the PFGE patterns (59%) were limited to isolates obtained from a single carcass. Forty-one percent of the PFGE-distinguishable strains were recovered from more than one carcass. Ninety-seven percent of the carcasses contaminated with the same strain were purchased at the same time from the same store. To examine the degree of genetic stability, four strains were followed in vitro over an estimated 1,000 doublings. The PFGE pattern of one of these isolates underwent minor changes during in vitro growth. The data indicate extensive variability in the PFGE patterns of Campylobacter spp. isolated from humans and from poultry carcasses. In spite of difficulties caused by such diversity and the fact that some carcasses are contaminated with more than one strain, the pattern variation provides a useful method for linking a particular strain to its source.     

A seven-year survey of Campylobacter contamination in meat at different production stages in Belgium

The presence of Campylobacter was assessed in different samples of poultry, pork and beef meat and carcasses from slaughterhouses, production plants and retail level. An introductory study from 1997 to 1999, had the purpose of establishing the optimum dilution to detect changes in prevalence and allowed a semi-quantitative estimation of poultry and pork contamination. Following this, between 2000 and 2003, 4254 samples were taken in order to study the trends. The poultry matrixes represented the greatest number and the most highly contaminated samples, with 30.9% (in 0.01 g) positive samples, 18.7% (in 1 g), 46.9% (in 25 g) and 19.6% (in 0.01 g) for broiler carcasses, broiler fillets, prepared chicken and layer carcasses, respectively. Broiler carcasses and fillets sampled at retail level were significantly less contaminated than samples from production plants. Pork, beef and veal samples were rarely contaminated and, where contamination existed, it was at a low prevalence (maximum 5.0%). The high and unvarying prevalence of Campylobacter in poultry necessitates the implementation of intervention measures at the primary production level, in addition to methods of minimizing cross-contamination at the processing level. A survey plan in line with the present study could be used in the future to monitor the effects of the planned measures and performance objectives and to follow the evolution of Campylobacter contamination at all stages of the food chain, in accordance with European legislation.     

Prevalence, antibiotic resistance, and molecular characterization of Salmonella serovars in retail meat products

The prevalence of Salmonella was determined in chicken meat (n = 26), beef (n = 49), and pork (n = 56) collected from wholesale markets, retail stores, and traditional markets in Seoul, South Korea, in 2009. Antibiotic resistance was assessed, and the molecular subtypes of Salmonella isolates were ascertained using an automated repetitive sequence-based PCR (rep-PCR) system (DiversiLab). A total of 18 Salmonella strains were isolated from 17 of 131 samples: 16 strains from each of 16 samples and 2 strains from the same pork sample. The prevalence of Salmonella from the retail meats was 2.0% in beef, 8.9% in pork, and 42.3% in chicken meat. Among 10 different serotypes, Salmonella enterica Panama was recovered from a beef sample, and Salmonella London and Salmonella Montevideo were the predominant serotypes from pork and chicken meat, respectively. The highest antibiotic resistance observed was to erythromycin (100%) followed by streptomycin (22.2%) and tetracycline and chloramphenicol (16.7%). Of the 18 isolates, 5 (27.8%) were resistant to two or more antibiotics, and 1 isolate from chicken meat was resistant to eight antibiotics, including cephalosporins. Differentiation between all of the Salmonella isolates except between Salmonella Montevideo and Salmonella London was successfully performed with the automated rep-PCR system, indicating that it can be added to the toolbox for source tracking of foodborne pathogens associated with outbreaks.     

2007—2016年四川省德尔卑沙门菌耐药与分子分型分析

目的 研究2007—2016年四川省德尔卑沙门菌分子分型和耐药趋势,掌握四川省德尔卑沙门菌污染状况,为暴发预警、溯源调查及抗生素使用策略提供参考数据。方法 运用脉冲场凝胶电泳(PFGE)和微量肉汤稀释法对2007—2016年四川省自临床病例、食品从业人员、食物中毒样品、养殖动物及零售食品中分离的106株德尔卑沙门菌进行分子分型及14种抗生素的敏感性测试。结果 106株德尔卑沙门菌对8类14种抗生素均有不同程度耐药,人源性和动物源性菌株对四环素、萘啶酸、氯霉素、复方磺胺的耐药率均大于20%。其中人源性菌株对头孢噻肟、环丙沙星、氨苄西林、氨苄西林/舒巴坦、头孢唑啉的耐药率均明显高于动物源性菌株;动物源性菌株对四环素、萘啶酸、氯霉素耐药率均明显高于人源性菌株。经Xba I酶切后106株菌共分为67个PFGE带型,不同年份的临床病例、食品从业人员及零售食品生猪肉分离株具有相同PFGE带型。结论 四川省德尔卑沙门菌分离株耐药率较高,并有逐年上升趋势。PFGE型别呈多样性,部分临床病例、食品从业人员分离株与生猪肉分离株PFGE具有相同带型。     

Prevalence of methicillin-resistant Staphylococcus aureus in a fresh meat pork production chain

The objective of this study was to investigate the prevalence of methicillin-resistant Staphylococcus aureus on different stages of a fresh pork production chain to reveal potential carryover from live animals to meat. Samples were collected at different stages of the production process in a large German abattoir with an integrated processing unit for fresh pork. Samples included nasal swabs from pigs at stunning, environmental samples from the slaughter line, surface samples from carcasses, environmental and meat samples from the processing unit, and samples from final products. Samples were analyzed with an established two-step selective enrichment method, and isolates were characterized with respect to their S. aureus protein A gene (spa) and staphylococcal cassette chromosome mec (SCCmec; which harbors the mecA gene) types. Contamination rate was highest (64.7%) in nasal swabs and lower (6.0%) on carcasses, meat at processing (4.2%), and final products (2.8%). Environmental samples were positive along the slaughter line (12%) but not in the processing unit. spa types t011 and t034 and SCCmec type V predominated the isolates. Heterogeneity of spa types was highest in nasal swabs. Results show that methicillin-resistant S. aureus can be identified at all stages of the production chain. Further studies are needed to identify potential control points to reduce the carryover from farm animals to the final products.     

北京市售生鲜猪肉和牛肉中有害细菌的鉴定及耐药性分析

采用选择性培养基初步筛选,结合16S rRNA同源性分析的方法,对北京市农贸市场及超市中所销售的生鲜猪、牛肉中含有的有害细菌的分布情况进行考察。对分离得到的细菌针对7种常见抗生素进行耐药表型检测。同时,利用特异性PCR扩增法检测了2个常见红霉素耐药基因和7个常见四环素耐药基因在分离细菌中的分布情况。结果表明:市场中购买的生鲜肉中分离得到的细菌耐药情况较之超市中的更为严重;猪肉和牛肉中分离的细菌耐药情况均十分严重;分离得到的不同细菌中包含某些条件致病菌的Escherichia/Shigella以及Aeromonas属细菌耐药情况更加严重。同时,研究还发现在北京市售鲜肉中分离得到的细菌中,绝大多数细菌对不止1种抗生素表现出非敏感(耐药及中介),且一些菌株携带多种不同的耐药基因。因此,市售生鲜肉中分离得到的细菌耐药情况较为严重以及普遍,应得到监管部门以及普通消费者的足够重视。     

Prevalence and diversity of Arcobacter spp. in the Czech Republic

The aim of this study was to examine 634 samples of chicken, lamb, pork, beef, fish, samples from the intensive animal industry and from poultry for slaughter, as well as from the domestic breeding of poultry, horses, pigs, and lambs, from surface water, and from clinical samples for the presence of Arcobacter. All the samples were examined with a cultivation method, followed by confirmation by multiplex PCR. The method of multiplex PCR applied directly to a liquid medium after enrichment was applied only to the samples with the highest probability of the presence of arcobacters. Arcobacter spp. were detected in 11.8% of the samples, of which A. butzleri, A. cryaerophilus, and A. skirrowii were found in 6.6, 5.1, and 0.2% of the samples, respectively. The sources of the arcobacters were chicken meat from the retail market, intensive animal production facilities, domestic chicken breeding facilities, lamb raising environments, surface water and wastewater, and beef swabs taken in a meat processing factory. No occurrence of arcobacters was identified in the swabs from slaughter turkeys, ducks, and wild poultry. No arcobacters were found in horse and pig breeding environments, on pork, or on the swabs of fish. Forty-two rectal swabs taken from humans were also free of Arcobacter. Seventeen isolates of Arcobacter were further identified by sequencing the 16S rRNA gene. Varied genotypes were observed among A. butzleri from chicken meat and chicken breeds, and A. cryaerophilus from wastewater and chicken breeds. They were similar to the genotypes present in wastewater, porcine feces, human stool, and human blood obtained from databases. Our results revealed that the chicken meat from the retail market is an important source of arcobacters. Cross-contamination during handling of chicken carcass practices could play a key role in the spread of Arcobacter.     

Occurrence of Salmonella enterica serotype typhimurium DT104A in retail ground beef

Surveillance data of cattle and human isolates of Salmonella enterica serovar Typhimurium DT104 indicate that this pathogen emerged worldwide in the 1980s, particularly in cattle. Studies were conducted to determine the prevalence of Salmonella Typhimurium DT104 in ground beef. Samples were also tested for the presence of generic Escherichia coli. A total of 404 fresh ground beef samples obtained at retail stores from New York, San Francisco, Philadelphia, Denver, Atlanta, Houston, and Chicago were shipped overnight to Georgia for processing. Salmonella spp. were isolated from 14 (3.5%) samples. Eight different serotypes were identified among the isolates, including Salmonella Typhimurium (5), Salmonella Lille (3), Salmonella Montevideo (1), Salmonella Hadar (1), Salmonella Meleagridis (1), Salmonella Cerro (1), Salmonella Kentucky (1), and Salmonella Muenster (1). Antibiotic resistance profiles indicated that all five Salmonella Typhimurium isolates were resistant to ampicillin, streptomycin, sulfamethoxazole, ticarcillin, and tetracycline but that they were sensitive to chloramphenicol. Phage typing revealed that all five Salmonella Typhimurium isolates were DT104A, a subtype of DT104. All five Salmonella Typhimurium DT104A isolates were obtained from ground beef sampled from retail outlets in San Francisco. Pulsed-field gel electrophoresis (PFGE) genomic DNA profiles of the five Salmonella Typhimurium DT104A isolates from ground beef were indistinguishable from those of four control Salmonella Typhimurium DT104 penta-resistant isolates from cattle that were used for comparison. A total of 102 generic E. coli isolates were obtained, only three of which were multiresistant to antibiotics. In addition, three E. coli isolates were recovered from samples that were positive for Salmonella Typhimurium DT104A. No correlation of antibiotic resistance profiles was observed between Salmonella Typhimurium DT104A and generic E. coli, as two of the three E. coli isolates were susceptible to all of the antibiotics tested, and the third isolate was resistant only to cephalothin. These data indicate that Salmonella Typhimurium DT104A can be isolated from retail ground beef, and because there was little overlap in antibiotic resistance patterns between Salmonella Typhimurium DT104A and E. coli isolates from the same ground beef samples, these limited data suggest that the transfer of antibiotic resistance genes among enteric bacteria in ground beef may not be common. This latter observation is further supported by the limited isolation of multiantibiotic-resistant E. coli from retail ground beef.     

Detection of sul1, sul2 and sul3 in sulphonamide resistant Escherichia coli isolates obtained from healthy humans, pork and pigs in Denmark

The occurrence of sulphonamide resistance was investigated in 998 Escherichia coli isolates, obtained from pig faeces collected at slaughter, Danish pork collected at retail outlets and from faeces from healthy persons in Denmark. In total 18% (n=35), 20% (n=38) and 26% (n=161) of the E. coli isolates obtained from humans, pork and pigs, respectively, were resistant to sulphonamide. All sulphonamide resistant E. coli isolates were investigated for the presence of sul1, sul2, sul3 and intI1 genes by PCR. The sul1 gene was detected in 40% (n=14), 29% (n=11) and 55% (n=88) of the sulphonamide resistant isolates from humans, pork and pigs, respectively. The sul2 gene was detected in 80% (n=28), 76% (n=29) and 50% (n=81) of isolates from humans, pork and pigs, respectively. None of the human isolates were PCR-positive for sul3, whereas sul3 was present in 5% of the pork isolates and 11% of the pig isolates. Of the 113 sul1 positive isolates, 97 carried the integron-associated integrase gene intI1. All 20 sul3 positive isolates were positive for intI1, and in 12 of these isolates sul3 was the only sulphonamide resistance gene detected. The origin of sul1 and sul2 found in isolates from healthy humans is speculative, but their spread from pigs to humans via the food chain is possible.