Antimicrobial resistance among Campylobacter jejuni isolated from raw poultry meat at retail level in Denmark

Campylobacter jejuni isolated from raw poultry meat collected at retail shops in Denmark in the period 1996-2003 were tested for susceptibility to seven antimicrobial agents. The food samples consisted of raw chicken meat and other raw poultry meat of domestic or imported origin. The highest levels of resistance among C. jejuni were observed for tetracycline, nalidixic acid and ciprofloxacin, whereas macrolide resistance was rarely detected. C. jejuni originating from other poultry meat (mainly duck and turkey meat) exhibited the highest occurrences of antimicrobial resistance monitored; approximately one third of the isolates were tetracycline resistant (N=100). Among chicken meat isolates, the occurrence of tetracycline resistance was significantly higher (P<0.005) in C. jejuni isolated from imported chicken meat (N=88) than in C. jejuni from Danish chicken meat (N=367). The same tendency was observed for chloramphenicol, nalidixic acid and ciprofloxacin (P<0.05). The trends in resistance in the period 1996-2003 among C. jejuni isolates from chicken meat indicate a decrease in the occurrence of resistance towards fluoroquinolones. This may be due to reduced application of fluoroquinolones for food animals. Monitoring of the occurrence of antimicrobial resistance in C. jejuni isolated from raw uncooked poultry has been performed on a yearly basis since 1996, thus providing useful insight into consumer exposure to antimicrobial-resistant C. jejuni.     

Antibiotic resistance of Campylobacter jejuni and Campylobacter coli isolated from hog, beef, and chicken carcass samples from provincially inspected abattoirs in Ontario

Campylobacterjejuni is one of the most common causes of bacterial foodborne infection in the United States, and there are reports of resistance of Campylobacter spp. to antimicrobial agents used for the treatment of gastroenteritis. The purpose of this study was to determine the antimicrobial resistance patterns of Campylobacter spp. isolated from hog, beef, and chicken carcasses from provincially inspected abattoirs in Ontario. The agar dilution method was performed to measure antimicrobial resistance of the isolates. Antimicrobial resistance of Campylobacter isolates from hogs (n = 401), beef (n = 21), and chicken (n = 435) to ampicillin, azithromycin, chloramphenicol, ciprofloxacin, clindamycin, erythromycin, gentamicin, nalidixic acid, streptomycin, and tetracycline was determined. Resistance of chicken, hog, and beef isolates was 14.3, 18.2, and 9.5% to ampicillin; 17.9, 67.3, and 38.1% to azithromycin; 0, 0.5, and 0% to chloramphenicol; 3.7, 1.2, and 0% to ciprofloxacin; 2.3, 46.6, and 4.8% to clindamycin; 6.7, 43.6, and 4.8% to erythromycin; 0.2, 0, and 0% to gentamicin; 5.1, 10.7, and 0% to nalidixic acid; 13.6, 57.4, and 4.8% to streptomycin; and 52.6, 44.1, 42.9% to tetracycline, respectively. The hog isolates had the greatest resistance to seven of the ten antimicrobials tested. Results of this study confirm the existence of antimicrobial resistance of Campylobacter to various antimicrobial agents,especially ciprofloxacin and erythromycin, commonly used for treatment of campylobacteriosis in humans.     

Antimicrobial resistance and molecular subtyping of Campylobacter jejuni and Campylobacter coli from retail meats

Campylobacter isolates (n = 297; 202 C. jejuni and 95 C. coli isolates) recovered from 2,513 retail meat samples (chicken breasts, ground turkey, ground beef, and pork chops) were examined for antimicrobial susceptibility. The isolates were further analyzed for genetic relatedness by pulsed-field gel electrophoresis (PFGE) using SmaI and KpnI restriction enzymes, and a subset of isolates (n = 174) were subtyped by multilocus sequence typing (MLST). The resistance most frequently observed was that to doxycycline (27.6%), followed by ciprofloxacin (13.8%) and erythromycin (6.4%). All isolates were susceptible to gentamicin and meropenem. C. coli showed higher resistance to doxycycline than did C. jejuni (42.1 versus 20.8%) and lower resistance to ciprofloxacin than did C. jejuni (10.5 versus 15.3%). Erythromycin resistance was only observed in C. coli. PFGE using SmaI plus KpnI digestion generated 168 clusters from 297 isolates: 115 from C. jejuni and 53 from C. coli. MLST revealed 44 sequence types (STs) under 10 clonal complexes from 120 C. jejuni and 27 STs under two clonal complexes from 54 C. coli. There was a positive association between PFGE and STs; however, PFGE showed greater discriminatory power than MLST. Subtyping data did not correlate with antimicrobial resistance phenotypes.     

Antimicrobial resistance in Enterococcus spp. strains isolated from organic chicken, conventional chicken, and turkey meat: a comparative survey

The mean counts of Enterococcus spp. were determined for 30 samples each of organic chicken meat, conventional chicken meat, and turkey meat, and differences for Enterococcus contamination in meat were determined. Two enterococci strains from each sample were isolated to obtain a total of 180 strains, and resistance to ampicillin, chloramphenicol, doxycycline, ciprofloxacin, erythromycin, gentamicin, nitrofurantoin, and vancomycin was determined by a disk diffusion method. Average counts obtained showed that Enterococcus mean counts from organic chicken meat (3.18 log CFU/g) were significantly higher than those obtained from conventional chicken meat (2.06 log CFU/g) or conventional turkey meat (1.23 log CFU/g). However, the resistance data obtained showed that isolates from organic chicken meat were less resistant than enterococci isolates from conventional chicken meat to ampicillin (P = 0.0067), chloramphenicol (P = 0.0154), doxycycline (P = 0.0277), ciprofloxacin (P = 0.0024), erythromycin (P = 0.0028), and vancomycin (P = 0.0241). In addition, isolates from organic chicken were less resistant than conventional turkey meat isolates to ciprofloxacin (P = 0.001) and erythromycin (P = 0.0137). Multidrug-resistant isolates were found in every group tested, but rates of multidrug-resistant strains were significantly higher in conventional chicken and turkey than those obtained from organic chicken meat. Enterococcus faecalis was the most common species isolated from organic chicken (36.67%), whereas Enterococcus durans was the most common species isolated from conventional chicken (58.33%) and turkey (56.67%). The rates obtained for antimicrobial resistance suggest that although organic chicken meat may have higher numbers of Enterococcus, these bacteria present a lower level of antimicrobial resistance.     

Prevalence and antimicrobial resistance of Campylobacter jejuni and Campylobacter coli isolated from raw chicken meat and human stools in Korea

Prevalence of Campylobacter in raw chicken meat and human stools and subsequent antibiotic resistance profiles of the pathogenic isolates obtained from 2000 through 2002 were investigated. Campylobacter jejuni and Campylobacter coli were isolated from 570 of the 923 raw chicken meat samples collected from traditional markets, large retail stores, or department stores in Korea, resulting in the isolation rate of 61.8%. A total of 579 Campylobacter isolates were obtained from raw chicken (36.3% for C. jejuni and 26.4% for C. coli) with the average population of 335.6 CFU/g. From 513 human stool samples, 15 isolates of Campylobacter were detected. Seasonal variation in the quantification of C. coli was not noticeable throughout the year, while the isolation rate of C. jejuni was the highest in September through October (840 CFU/g) followed by that of July through August and May through June in decreasing order, showing a significant seasonal effect (P < 0.05). Contamination of Campylobacter was more severe in raw chicken meat sold in traditional markets than in those sold in large retail stores and department stores. Prevalence of Campylobacter in raw chicken sold in traditional markets was significantly influenced by seasonal changes (P < 0.05), whereas the samples obtained from other places was less affected by the seasonal changes. Susceptibilities of the 594 chicken isolates to ciprofloxaxin, chloramphenicol, erythromycin, kanamycin, nalidixic acid, and tetracycline were determined by an E-test. Campylobacter isolates were the most resistant to nalidixic acid (91.4%) followed by ciprofloxaxin (87.9%), tetracycline (87.2%), kanamycin (30.6%), erythromycin (19.4%), and chloramphenicol (1.3%). Human isolates showed a similar resistance to the six antibiotics tested. The proportion of Campylobacter isolates with multidrug resistance to four or more antimicrobials obtained from 2000 through 2002 ranged from 28 to 43.5%, indicating that it could be a serious health-threatening factor. This study suggests that it is prudent to establish an effective National Monitoring Program in Korea for the prevention and control of Campylobacter spp.     

In vitro antimicrobial susceptibility, genetic diversity and prevalence of UDP-glucose 4-epimerase (galE) gene in Campylobacter coli and Campylobacter jejuni from Turkey production facilities

This study evaluated the genetic diversity of multi-drug resistant Campylobacter jejuni (n=44) and C. coli (n=30) isolated from 18 turkey houses. Antimicrobial resistances to ampicillin, ciprofloxacin and nalidixic acid were higher (P<0.05) in C. coli than in C. jejuni strains. PCR analysis indicated that 82% of total isolates tested, including 91% of C. jejuni and 70% of C. coli tested positive for a 496-bp UDP-glucose 4-epimerase (galE) gene. The diversity of isolates was mapped by antibiogram, SmaI-PFGE and flaA-RFLP typing methods using the discriminatory index (DI). RFLP was more suitable in discriminating C. coli (DI=0.895) than PFGE (DI=0.816) or antibiogram profile (DI=0.552), while either PFGE (DI=0.941) or RFLP (DI=0.942) could be used in discriminating C. jejuni strains. The combined PFGE and antibiogram dendrogram had the highest DI for both C. coli (0.910) and C. jejuni (0.968), suggesting that a combination of typing methods is more useful in examining the diverse Campylobacter population on turkey farms.     

石家庄市肉鸡屠宰和市售环节弯曲菌污染状况及耐药分析

目的了解石家庄市肉鸡屠宰和市售环节中弯曲菌的污染状况及对12种抗生素的耐药谱和耐药特征。方法采集屠宰前肉鸡肛拭子、鸡酮体涂抹拭子标本和市售鸡肉、鸡肝脏样品,参照GB 4789.9—2014《食品安全国家标准食品微生物学检验空肠弯曲菌检验》和多重聚合酶链式反应(PCR)方法进行弯曲菌的分离和鉴定,用K-B纸片法对分离弯曲菌进行6类12种抗生素药敏测定。结果在439份标本/样品中共有17份检出弯曲菌,总检出率为3.9%(17/439)。空肠弯曲菌对萘啶酸、左氧氟沙星、环丙沙星和四环素的耐药率均为85.7%(6/7),对庆大霉素、链霉素、丁胺卡那、阿奇霉素、氟苯尼考全部敏感。结肠弯曲菌除对阿奇霉素、多西环素、氟苯尼考的耐药率小于50.0%外,对环丙沙星、左氧氟沙星、萘啶酸、庆大霉素、丁胺卡那、四环素、链霉素、克林霉素的耐药率均高于80.0%。17株弯曲菌多重耐药率为70.6%(12/17),呈11种耐药谱型,市售环节分离株耐药谱型多于屠宰环节分离株,并具有各自不同的优势耐药谱型。结论石家庄市肉鸡屠宰和市售环节均有一定程度的弯曲菌污染,分离株多重耐药情况严重,呈多种耐药谱型。     

Comparison of antimicrobial resistance of Campylobacter jejuni and Campylobacter coli isolated from humans and chicken carcasses in Poland

Campylobacter-associated gastroenteritis remains an important cause of morbidity worldwide, and some evidence suggests that poultry is an important source of this foodborne infection in humans. This study was conducted to analyze the prevalence and genetic background of resistance of 149 Campylobacter jejuni and 54 Campylobacter coli strains isolated from broiler chicken carcasses and from stool samples of infected children in Poland from 2003 through 2005. Nearly all isolates were susceptible to macrolides and aminoglycosides. The highest resistance in both human and chicken strains was observed for ciprofloxacin (more than 40%), followed by ampicillin (13 to 21%), and tetracycline (8 to 29%). Resistance to ampicillin and tetracycline rose significantly between 2003 and 2005. Slight differences in resistance between human and chicken isolates indicate that although chicken meat is not the only source of Campylobacter infection in our population, it can be involved in the transmission of drug-resistant Campylobacter strains to humans.     

Prevalence and antimicrobial resistance of Campylobacter isolated from retail raw chicken and beef meat, Tehran, Iran

Campylobacter spp. is a leading cause of human diarrhea. The common source of infection is contaminated food, particularly poultry. The veterinary use of antimicrobial drugs has been suggested to be largely responsible for resistance in human isolates of this zoonotic pathogen. From April to October 2004, 241 samples of chicken and beef meat for sale in retail outlets in Tehran (Iran) were analyzed for the presence of Campylobacter. Totally, 88 (36.5%) Campylobacter strains were isolated. Campylobacter was isolated from a significantly larger number of chicken (63%) than beef (10%) meat (P < 0.0001). Susceptibilities of 72 strains were determined for eight antimicrobial drugs using the disk diffusion assay. Resistance to nalidixic acid was the most common finding (75%), followed by resistance to ciprofloxacin (69.4%), tetracycline (45.8%), amoxicillin (11.1%), streptomycin (4.2%), chloramphenicol (2.8%) and gentamicin (1.4%). None of the isolates was resistant to erythromycin. Multidrug resistance was seen in 75% of the Campylobacter strains.     

Prevalence, antibiotic resistance and RAPD typing of Campylobacter species isolated from ducks, their rearing and processing environments in Penang, Malaysia

We report for the first time on the prevalence, antibiotic resistance and RAPD types of Campylobacter species in ducks and duck related environmental samples in Malaysia. Samples were examined by enrichment in Bolton Broth followed by plating onto modified Charcoal Cefoperazone Deoxycholate agar (mCCDA) and/or plating directly onto mCCDA. A total of 643 samples were screened, and the prevalence of Campylobacter spp. in samples from different sources ranged from 0% to 85%. The method of isolation had a significant (P<0.05) effect on the isolation rate. One hundred and sixteen Campylobacter isolates, comprising of 94 Campylobacter jejuni, 19 Campylobacter coli and three Campylobacter lari, were examined for their sensitivity to 13 antibiotics. Majority of the C. jejuni isolates were resistant to cephalothin (99%), tetracycline (96%), suphamethoxazole/trimethoprim (96%), and very few were resistant to gentamicin (5%), chloramphenicol (7%) and erythromycin (1%). All C. coli isolates were resistant to cephalothin, nalidixic acid, norfloxacin and tetracycline but susceptible to chloramphenicol, erythromycin and gentamicin. The three C. lari isolates were resistant to all the antibiotics tested except chloramphenicol and gentamicin (1/3 and 2/3 susceptible, respectively). Genetic diversity of Campylobacter isolates were determined using random amplification of polymorphic DNA (RAPD). C. jejuni and C. coli isolates belong to fifty-eight and twelve RAPD types, respectively.     

Prevalence and antibiotic resistance of Campylobacter spp. isolated from chicken meat, pork, and beef in Korea, from 2001 to 2006

A total of 770 samples of retail raw meat were examined for the presence of Campylobacter spp. The samples were obtained randomly from 232 retail stores in Korea from September 2001 to April 2006. The highest contamination rates were observed in chicken meat (220 181.4%] of 270 samples), whereas the rates of contamination in pork and beef were extremely low (1.6 and 1.2%, respectively). The antibiotic-resistant patterns of the 317 Campylobacter isolates were examined by the agar dilution method. Resistance to doxycycline was the most common (97.5%), followed by ciprofloxacin (95.9%), nalidixic acid (94.6%), tetracycline (94.6%), enrofloxacin (84.2%), and erythromycin (13.6%). All Campylobacter isolates from the retail raw meat were resistant to at least one of the six antibiotics tested, and 296 isolates (93.4%) showed multidrug (four or more antibiotics) resistance. This demonstrates that the multidrug-resistant Campylobacter species are widespread in meats in Korea. Therefore, further investigations will be needed to determine appropriate methods for eliminating Campylobacter contamination in industrial chicken production and food chains.     

2016—2018年北京市腹泻患者弯曲菌耐药性与脉冲场凝胶电泳分子分型的研究

目的分析北京市腹泻患者弯曲菌(Campylobacter spp.)分离株的抗生素敏感性和脉冲场凝胶电泳(pulsed field gel electrophoresis,PFGE)分子分型特征。方法2016—2018年,对北京市19家医院肠道门诊分离的弯曲菌采用琼脂稀释法进行抗生素敏感性检测,按照PulseNet的方法进行PFGE实验和聚类分析。结果所有空肠弯曲菌至少对一种抗生素有耐药性。空肠弯曲菌对环丙沙星(95.30%)的耐药率最高,其次为四环素(94.02%)和萘啶酸(92.31%),结肠弯曲菌对环丙沙星(95.00%)、四环素(95.00%)的耐药率最高,其次为萘啶酸(90.00%)。空肠弯曲菌菌株和结肠弯曲菌菌株的多耐药率分别是55.56%和75.00%。228株空肠弯曲菌共产生135种PFGE带型,40株结肠弯曲菌共产生34种PFGE带型,带型分布较为分散。结论2016—2018年北京市腹泻患者弯曲菌分离株的耐药率较为严重,耐药模式复杂,PFGE带型呈多态性分布。     

Prevalence, genetic diversity, and antibiotic resistance patterns of Campylobacter jejuni from retail raw chickens in Korea

Campylobacter jejuni is a frequently detected food-borne pathogenic bacterium. Clinical cases are mostly sporadic but campylobacteriosis can have serious consequences, such as the development of Guillain-Barré syndrome as well as diarrheal diseases. We examined 265 retail raw chickens from Korean markets for the presence of C. jejuni using the US Food and Drug Administration standard cultural method and multiplex polymerase chain reaction (mPCR). The mPCR-confirmed C. jejuni isolates were subtyped by pulsed field gel electrophoresis (PFGE) and flaA-typing for investigating the genetic diversity of the microorganism in retail raw chickens. Restriction enzymes SmaI and DdeI were used for PFGE and flaA-typing, respectively. Campylobacter spp. were found in 181 samples (68.3%) and C. jejuni in 100 samples (37.74%). For C. jejuni, 73 pulsotypes and 30 flaA types were detected. Antibiotic resistance tests performed by disk diffusion assay indicated that most C. jejuni isolates were resistant to tetracycline, nalidixic acid, and ciprofloxacin, and 87 composite types were revealed by PFGE, flaA-typing, and the antibiotic resistance tests. Our results show that the genetic diversity of C. jejuni isolates is very high and the correlation between genotype and antibiotic resistance was low even though many bacteria showed multi-drug resistance.     

Comparison of antimicrobial resistance of Campylobacter jejuni isolated from humans, chickens, raw milk, and environmental water in Québec

This study compares the occurrence of antimicrobial resistance to erythromycin, ciprofloxacin, and tetracycline among 384 Campylobacter jejuni isolates from humans (245), fresh whole retail chickens (56), raw milk (33), and environmental water (41) collected between 2000 and 2003 in Québec, Canada. Resistance to ciprofloxacin was significantly more frequent in human isolates acquired abroad than in those acquired locally (50 versus 5.9%; P < 0.001); ciprofloxacin resistance was almost absent in water, chicken, and raw milk isolates. In contrast, resistance to erythromycin was significantly more common in chicken than in locally acquired human isolates (16 versus 3.0%, respectively; P < 0.001); no erythromycin resistance was found among water, raw milk, and human isolates acquired abroad. Resistance to tetracycline was significantly more common in chicken and human isolates acquired locally (58.9 and 45.8%, respectively) than in raw milk and water isolates (9.1 and 7.3%, respectively, P < 0.001). Tetracycline resistance was also observed in 44.4% of human isolates acquired abroad. No human isolate was resistant to both ciprofloxacin and erythromycin, but one chicken isolate was resistant to all three antimicrobial agents. Our results suggest that from 2000 to 2003 in Québec, antimicrobial resistance remained stable among locally acquired C. jejuni human clinical isolates and might even have decreased. However, the high erythromycin resistance rate observed among chicken isolates is concerning because of the risk of transmission of such isolates to humans. Additional studies are needed to monitor trends in antimicrobial resistance among food, environment, and human C. jejuni isolates as well as antibiotic use in animals.     

Antimicrobial resistance of Campylobacter coli isolates from swine

Eighty-three swine isolates of Campylobacter coli were tested for mechanisms underlying resistance to nalidixic acid, ciprofloxacin, erythromycin and tetracycline. Four isolates harbored class 1 integrons but none carried class 2 and 3 integrons. Most of the tetracycline-resistant isolates (97%) possessed tet(O). A Thr-86-Ile substitution in GyrA and an A-2230-G mutation in 23S rRNA were the main resistance mechanisms for quinolones and erythromycin, respectively.     

The temporal,PFGE and resistance pattern associations suggest that poultry products are only a minor source of human infections in Western Finland

In order to compare human and retail poultry meat thermophilic Campylobacter isolates originating in a regional area in Western Finland, minimum inhibitory concentration (MICs) for six antimicrobials (96 isolates) and pulsed-field gel electrophoresis (PFGE) (102 isolates) were analysed. Campylobacter spp. were detected in 10.5% out of 305 fresh poultry products studied; 29 (90.5%) isolates were identified as Campylobacter jejuni. Among the 70 human isolates, 66 (94.3%) isolates were identified as C. jejuni. Only one C. jejuni domestic poultry isolate showed resistance (ampicillin), whereas domestic human C. jejuni isolates were more commonly resistant to ciprofloxacin, nalidixic acid, ampicillin and tetracycline. The resistance in foreign human isolates was significantly more common than among domestic isolates. PFGE analysis with KpnI restriction enzyme resulted in 59 different PFGE types among the poultry and human isolates. Three types were detected first in poultry meat and thereafter during the following month in domestic human samples, whereas the other conjoint types were detected only after many months. This study suggests that poultry products play only a minor role in human campylobacteriosis in the study area and that the resistance found in domestic human isolates is not likely related to retail poultry meat products.     

杨凌及周边地区零售分割鸡肉中沙门菌污染状况及耐药和分型特征研究

目的研究陕西杨凌及周边地区零售分割鸡肉中沙门菌的污染状况及其药敏性、血清型和基于脉冲场凝胶电泳(PFGE)的基因型,为预警食源性沙门菌疾病暴发提供数据基础。方法采用GB 4789.4—2010《食品安全国家标准食品微生物学检验沙门氏菌检验》对陕西杨凌及周边地区采集的188份零售分割鸡肉中沙门菌进行分离和鉴定,并进行血清学分型。采用PFGE方法确定沙门菌DNA酶切电泳图谱,使用BioNumerics软件聚类分析电泳结果,确定沙门菌基因型。结果 188份零售分割鸡肉中共有34份(18.1%)样品检出沙门菌,农贸市场样品沙门菌检出率(24.6%,29/118)高于超市(7.1%,5/70)。鸡腿、鸡爪、鸡脖和鸡肝样品中沙门菌检出率高于鸡肠和鸡胗。34株沙门菌中共检出10种血清型,其中科瓦利斯沙门菌最为流行,高于德尔卑沙门菌和鼠伤寒沙门菌等,差异有统计学意义(P0.05)。分离株均对磺胺异噁唑、氯霉素、头孢噻呋和环丙沙星耐药,对甲氧苄啶/磺胺甲噁唑、萘啶酮酸、四环素、链霉素、氨苄西林和阿莫西林/克拉维酸的耐药率均在50%以上。34株沙门菌PFGE分型后可被分为11个簇,同一血清型菌株基本聚于同一大簇,同一时间、从相同市场采集的不同样品,其分离株PFGE型相似度均较高,表明分割鸡肉在加工或销售过程可能存在交叉污染。农贸市场分离菌株基因型多样性比较丰富。结论杨凌及周边地区零售分割鸡肉存在沙门菌污染,沙门菌血清型和基因型多样化,耐药菌株比例较高。     

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.     

Detection, semiquantitative enumeration, and antimicrobial susceptibility of Yersinia enterocolitica in pork and chicken meats in Italy

Yersinia enterocolitica is recognized as an etiological agent of gastroenteritis, lymphadenitis, and chronic sequelae. During 2006 and 2007, 205 samples (125 pork and 80 chicken meats) were collected in Italy and tested for detection and most-probable-number (MPN) enumeration of Y. enterocolitica organisms. The microorganism was isolated from 45 samples (21.9%): 19 (15.2%) pork samples and 26 (32.5%) chicken samples. Y. enterocolitica MPN contamination levels were low, ranging from 0.30 to 1.50/g. Most (94.4%) Y. enterocolitica strains were biotype 1A (serotypes O:3; O:5; O:6,30; O:6,30-6,31; O:7,8-8-8,19; O:8; O:9; O:25,35; O:36; and O nontypeable), and 5.6% of the isolates were bioserotype 2/O:9. All isolates were tested for yadA, ail, inv, ystA, and ystB virulence sequences. The yadA gene was detected in two strains (3.7%) isolated from chicken samples: one Y. enterocolitica 2/O:9 yadA+ ail+ ystA+, and one Y. enterocolitica 1A/O:7,8-8-8,19 yadA+ inv+ ystB+. Two (3.7%) 2/O:9 strains, isolated from pork products, were ail+ ystA+. Most biotype 1A strains were ystB+ (84.3%) and inv+ (39.2%). All strains were sensitive to cefotaxime, ciprofloxacin, chloramphenicol, nalidixic acid, streptomycin, sulfonamide, tetracycline, trimethoprim, and trimethoprim-sulfamethoxazole. Resistance to gentamicin and aztreonam was observed in 1.9% of the isolates. High levels of resistance were detected toward amoxicillin-clavulanic acid (27.8%), ampicillin (75.9%), and erythromycin (100%). The authors hypothesize that Y. enterocolitica pathogenic biotypes are rather uncommon in foods when compared with their isolation rates from animal sources and that chicken meat could be contaminated as well as pig meat and its derived products.     

Prevalence and antimicrobial resistance of Campylobacter in antimicrobial-free and conventional pig production systems

The objectives of this study were to determine and compare the prevalence and antimicrobial resistance of Campylobacter species in swine reared in conventional and antimicrobial-free (ABF) production systems. Campylobacter coli was the predominant species, with 1,459 isolates (99%) in the study. We found significantly higher prevalence of C. coli on the ABF farms (77.3%) than on the conventional farms (27.6%) among pigs at the nursery stage (P < 0.001). At slaughter, we found significantly higher prevalence at the postevisceration than at the preevisceration stage (P < 0.001) in both production systems. The 1,459 C. coli isolates were tested with the agar dilution method for their susceptibility to six antimicrobials: chloramphenicol, ciprofloxacin, erythromycin, gentamicin, nalidixic acid, and tetracycline. Resistance was most prevalent against tetracycline (66.2% of isolates) followed by erythromycin (53.6% of isolates). Frequency of resistance to these two antimicrobials was significantly higher among conventional herds (83.4% for tetracycline and 77% for erythromycin) than among ABF herds (56.2% for tetracycline and 34.5% for erythromycin). Resistance to ciprofloxacin at the MIC (> 4 mg/liter) was also found on farms in both systems. Multidrug-resistant C. coli strains were detected in both the conventional (7%) and ABF (4%) herds. This is the first report of ciprofloxacin-resistant strains of C. coli in ABF pigs in the United States. These findings highlight the high prevalence of antimicrobial-resistant C. coli in both conventional and ABF pig production systems and have significant implications for the persistence of antimicrobial-resistant Campylobacter in the pig production environment regardless of levels of antimicrobial use.