Listeria monocytogenes contamination in French breeding and fattening turkey flocks

This study aimed to collect data and create a database related to Listeria monocytogenes contamination in breeding and fattening turkey flocks. Seventy-five breeding turkey flocks and 86 fattening turkey flocks were sampled. Three hundred seventy-five and 428 samples were analyzed in breeding and fattening turkey flocks, respectively. L. monocytogenes was detected in 9 of 75 breeding flocks, leading to an estimated prevalence of 12% (95% confidence interval, 4.6-19.4). In fattening turkeys, the prevalence of L. monocytogenes-positive flocks was 9.3% (95% confidence interval, 3.1-15.5). The serotyping of L. monocytogenes strains highlighted the dominance of serovar 1/2a in breeding as well as in fattening turkeys. The relationship between rearing practices and L. monocytogenes status in turkey flocks was studied by using multiple correspondence analyses and then a hierarchical classification. Results were separated into two classes and revealed profiles that were associated with the presence or the absence of L. monocytogenes. This study highlighted the need to implement strict sanitary measures to reduce the risk of L. monocytogenes contamination in turkey production.     

External contamination of Campylobacter-free flocks after transport in cleaned and disinfected containers

The possible colonization of the intestines and contamination of broilers after transport to the slaughterhouse with Campylobacter strains present in cleaned and disinfected transport containers was investigated. Seven broiler flocks with a Campylobacter-free status were sampled once just before loading at the farm and once just before slaughter. On both occasions, samples were also taken from the exterior of the birds and from the intestinal content. Transport containers used to transport the flock were sampled on the farm just before loading the birds. Campylobacters were enumerated and genotyped by flagellin gene A PCR-restriction fragment length polymorphism and pulsed-field gel electrophoresis. In total, 25 of the 35 sampled containers were Campylobacter contaminated, and 30 genotypes were found. Three broiler flocks became colonized on the farm between initial status determination and transport to the slaughterhouse, and three Campylobacter-free flocks were externally contaminated after transport. In none of the seven flocks was evidence found of intestinal colonization or cocolonization due to transport in Campylobacter-contaminated containers.     

肉鸡养殖场中环丙沙星和头孢噻肟双重耐药沙门菌耐药机制的研究

目的阐明养殖场肉鸡及其环境中环丙沙星和头孢噻肟耐药沙门菌的分布和耐药机制特点。方法对河南省4个不同地区肉鸡养殖场及环境中分离的沙门菌进行环丙沙星和头孢噻肟双重耐药菌株的筛选和鉴定,并对分离株进行药敏试验、喹诺酮类和超广谱β内酰胺酶耐药机制研究。结果从52株养殖场肉鸡肛拭子及环境中筛选出5株耐环丙沙星和头孢噻肟的沙门菌,均为印第安纳沙门菌,有AMP-CAZ-CHL-CIP-CTX-GEN(n=1)和AMP-CAZ-CHL-CIP-CTX-GEN-SXT-TET(n=4)两种耐药谱。喹诺酮耐药机制研究显示,5株菌的拓扑异构酶编码基因gyr A和par C均有点突变出现,均携带了质粒介导的喹诺酮耐药基因,包括oqx AB、aac(6')-Ib-cr基因,而qnr A、qnr B、qnr S、qnr C、qnr D和qep A基因则未检出。超广谱β-内酰胺酶耐药机制显示,5株菌均为blaCTX-M-65型。结论耐环丙沙星和头孢噻肟的菌株存在于肉鸡养殖环节及其环境中,并具有复杂的喹诺酮耐药机制和可传播的超广谱β内酰胺酶耐药机制。为阐明农场-餐桌-感染者传递链条中耐药关联性,为社区感染防控、临床抗生素用药提供科学依据,我国应该加强肉鸡等养殖业沙门菌多重耐药菌株的监测。     

Effect of vaccinating breeder chickens with a killed Salmonella vaccine on Salmonella prevalences and loads in breeder and broiler chicken flocks

The objective of this study was to evaluate the effect of vaccination of breeder chickens on Salmonella prevalences and loads in breeder and broiler chicken flocks. Chickens housed on six commercial breeder farms were vaccinated with a killed Salmonella vaccine containing Salmonella Typhimurium, Salmonella Enteritidis, and Salmonella Kentucky. Unvaccinated breeders placed on six additional farms served as controls. Eggs from vaccinated and unvaccinated breeder flocks were kept separately in the hatchery, and the resulting chicks were used to populate 58 commercial broiler flock houses by using a pair-matched design. Vaccinated breeder flocks had significantly higher Salmonella-specific antibody titers than did the unvaccinated breeder flocks, although they did not differ significantly with respect to environmental Salmonella prevalences or loads. Broiler flocks that were the progeny of vaccinated breeders had significantly lower Salmonella prevalences and loads than broiler flocks that were the progeny of unvaccinated breeders. After adjusting for sample type and clustering at the farm level, the odds of detecting Salmonella in samples collected from broiler flocks originating from vaccinated breeders were 62% lower (odds ratio [95% confidence interval] = 0.38 [0.21, 0.68]) than in flocks from unvaccinated breeders. In addition, the mean load of culture-positive samples was lower in broilers from vaccinated breeders by 0.30 log most probable number per sample (95% confidence interval of -0.51, -0.09; P = 0.004), corresponding to a 50% decrease in Salmonella loads. In summary, vaccination of broiler breeder pullets increased humoral immunity in the breeders and reduced Salmonella prevalences and loads in their broiler progeny, but did not significantly decrease Salmonella in the breeder farm environment.     

肉鸡饲养加工过程中沙门菌污染环节的探讨与分析

目的 探讨开封市肉鸡从孵化、养殖,到屠宰、加工、运输和销售各环节样品沙门菌污染状况.方法 采集2012年4个季度开封地区种鸡养殖场、肉鸡孵化场、养殖场、屠宰场和大型超市中土壤、饲料、鸡粪、鸡肉、屠宰工具、工人手等18个环节共802份样品.按照GB 4789.4-2010进行沙门菌鉴定和血清学分型,用SPSS 17.0软件对数据进行统计分析.结果 脱毛池水中沙门菌检出率最高为75％,其次成鸡粪便、鸡肉、刀具案板、肛拭子中沙门菌检出率分别为58.3％、49.4％、33.3％、5.6％,鸡胚和运输车辆中未检出沙门菌.本研究共检出6个血清型,以肠炎沙门菌和印第安纳沙门菌检出率最高;第二季度沙门菌菌型数最多.结论 鸡肉屠宰加工过程使沙门菌污染扩大,脱毛机及脱毛池水是沙门菌交叉污染的关键点,不同季节的检出率差异无统计学意义(P＞0.05).     

Campylobacter contamination of broiler caeca and carcasses at the slaughterhouse and correlation with Salmonella contamination

In order to estimate the prevalence of Campylobacter spp. and Salmonella spp. on broiler chicken carcasses and the prevalence of Campylobacter spp. in caeca, 58 French slaughterhouses were investigated in 2008. Enumeration of Campylobacter spp. was also performed in order to study the relation between caeca and carcass contamination. A pool of 10 caeca and one carcass were collected from 425 different batches over a 12-month period in 2008. Salmonella was isolated on 32 carcasses leading to a prevalence of 7.5% ([5.0-10.0]_95%CI). The prevalence of Campylobacter was 77.2% ([73.2-81.2]_95%CI) in caeca and 87.5% ([84.4-90.7]_95%CI) on carcasses. No significant correlation was found between Campylobacter and Salmonella. Positive values of Campylobacter were normally distributed and the average level was 8.05 log₁₀ cfu/g ([7.94-8.16]_95%CI) in caeca and 2.39 cfu/g ([2.30-2.48]_95%CI) on carcasses. A positive correlation (r = 0.59) was found between the mean of Campylobacter in caeca and on carcasses (p < 0.001). Thus, carcasses from batches with Campylobacter-positive caeca had significantly (p < 0.001) higher numbers of Campylobacter per gram than batches with negative caeca. These results show that Campylobacter can be present in both matrices and reduction in caeca could be a possible way to reduce the amount of bacteria on carcasses. Of the 2504 identifications performed, 3 species of Campylobacter (Campylobacter jejuni, Campylobacter coli and Campylobacter lari) were identified. The main species recovered were C. jejuni and C. coli, which were isolated in 55.3% and 44.5% of positive samples, respectively. These two species were equally represented in caeca but C. jejuni was the most frequently isolated on carcasses with 57.1% and 42.5% of positive carcasses for C. jejuni and C. coli, respectively. This study underlines that target a reduction of Campylobacter on final products requires a decrease of contamination in caeca.     

Pre-harvest surveillance of Campylobacter and Salmonella in Danish broiler flocks: a 2-year study.

In national surveillance programmes of broiler flocks carried out in Denmark during 1998 and 1999, 89,110 samples for Campylobacter representing 8911 broiler flocks were taken at 10 different abattoirs, and 44,550 samples for Salmonella were taken from the same flocks in the broiler houses at the farms. Of the swabs, 42.5% were Campylobacter positive. Most positive samples were found during July, August and September, while the lowest number of positive samples were found during January, February, March and April. Of the flocks, 5.5% were Salmonella positive, but no seasonal variation was observed. For each flock, the presence of Campylobacter and Salmonella was recorded in order to estimate the possible correlation between colonisation with the two pathogens. In conclusion, no significant effects on intensive cleaning and disinfection procedures on Campylobacter occurrence could be demonstrated, and no significant correlation between occurrence of Campylobacter and Salmonella infections in Danish broilers could be demonstrated which is in contrast to previous observations on concurrent colonisation of broilers with these two zoonotic pathogens.     

Effect of logistic slaughter on Salmonella contamination on pig carcasses

Previous studies have shown that infected pigs are the source of carcass and slaughterhouse environment contamination by Salmonella. The present study tried to evaluate the effect of a logistic slaughter, organised according to Salmonella seroprevalence, on Salmonella contamination on carcasses. The study was performed at the beginning of slaughtering during three consecutive days. Low risk herds (8 batches) were slaughtered on day I, high risk herds (6 batches) on day II, and finally, moderate risk herds (5 batches) were slaughtered on day III. Each slaughtering day, holding pens, five points of the slaughter line, and 80 carcasses were sampled. The number of positive carcasses on days I, II and III was 7 (8.8%), 5 (6.3%) and 19 (24.4%) respectively. The results evidenced no clear effect of the logistic slaughter on carcass contamination, with a three times higher risk of finding a positive carcass when moderate Salmonella risk batches were slaughtered. Carcass contamination in low risk herds was linked to the contamination of holding pens and the slaughter line activities. On the other hand, Salmonella was not detected in any of the sampled carcasses in three out of six high risk Salmonella batches, showing that proper slaughtering practices can prevent carcass contamination. The experience reported here, demonstrates that apart from an accurate batch separation according to their seroprevalence levels, strict measures for cleaning and disinfection in the lairage and the slaughterhouse facilities are needed when logistic slaughter is performed.     

肉鸡加工过程中沙门氏菌的污染监测及分析

目的对肉鸡屠宰加工的不同环节进行沙门氏菌监测,了解各个环节沙门氏菌的污染状况,分析肉鸡加工过程中沙门氏菌的污染来源及关键环节。方法选择河南省某大型肉鸡屠宰加工企业作为监测点,在肉鸡屠宰前、褪毛后、过预冷池后、被分割后和包装入库等环节及预冷池水、分割刀具案板和工人手等处分别采集样本,共计1756份,进行沙门氏菌检测及其血清型鉴定。结果于1756份样本中检出沙门氏菌阳性样本700份,检出率为39.9%。其中,褪毛后整禽的沙门氏菌检出率最高,达63.9%;其次为过预冷池后的整禽胴体,检出率为57.3%。屠宰加工环节中检出的沙门氏菌中肠炎沙门氏菌最多,占71.7%,其次为印第安纳沙门氏菌,占20.8%。结论肉鸡在养殖期间存在沙门氏菌污染,且在屠宰加工环节存在交叉污染,应针对相关环节进行重点控制和工艺改进。     

2010年江苏省肉鸡沙门菌污染专项监测分析

目的了解肉鸡养殖和屠宰过程中沙门菌的污染状况,为确定从生产到销售各环节沙门菌分布和疾病可能传染源、制定公共卫生措施并评价其有效性提供科学依据。方法按照《全国食源性致病菌监测工作手册》中专项监测的采样和实验室检测要求,2010年共采集活体肉鸡肛拭样本210份,胴体样本204份,监测沙门菌污染情况。结果肛拭样本检出沙门菌23份,检出率10.95%;胴体样本检出沙门菌71份,检出率34.80%。两类样本的血清学分型构成比不同(χ2=15.7,P<0.001),肛拭样本检出的23株沙门菌中有22株印第安纳沙门菌,胴体样本中检出的71株沙门菌中有35株为印第安纳沙门菌,22株为奥尔巴尼沙门菌。结论肉鸡活体肛拭和胴体样本沙门菌检出率差异有统计学意义(χ2=33.5,P<0.001),胴体高于活体检出率,活体和胴体的沙门菌来源不同,胴体可能存在交叉污染。     

Salmonella contamination during production of cantaloupe: a binational study

Six cantaloupe farms and packing plants in South Texas (950 cantaloupe, 140 water, and 45 environmental samples), including the Rio Grande Valley area, and three farms in Colima State, Mexico (300 cantaloupe, 45 water, and 15 environmental samples), were sampled to evaluate cantaloupe contamination with Salmonella and Escherichia coli during production and processing. Samples collected from external surfaces of cantaloupes, water, and the environments of packing sheds on cantaloupe farms were examined for the presence of Salmonella and E. coli. Of a total of 1,735 samples collected, 31 (1.8%) tested positive for Salmonella. Fifteen Salmonella serotypes were isolated from samples collected in Texas, and nine from samples collected in Colima. Two serotypes (Poona and Oranienburg) that have been associated with three large Salmonella outbreaks in the United States and Canada linked to the consumption of contaminated cantaloupe were found in water samples collected at four farms (three from the United States). Susceptibility of Salmonella isolates to 10 antimicrobials was evaluated by disk diffusion. Eighty-eight percent of the isolates from the United States and Mexico were pansusceptible to the antimicrobials tested; eight isolates from the United States demonstrated an intermediate susceptibility to streptomycin and only two isolates were resistant to the same antimicrobial. From Mexico, four isolates showed an intermediate susceptibility to streptomycin and one isolate was resistant to nalidixic acid and streptomycin. Repetitive sequence-based PCR analysis of Salmonella isolates helped to trace potential sources of Salmonella contamination in source water and in subsequent water samples obtained after the filtration systems of U.S. and Mexican cantaloupe farms. No differences could be seen between the levels of Salmonella contamination in melons from both countries.     

Salmonella contamination of pigs and pork in an integrated pig production system

This paper describes the monitoring of Salmonella in a closed pig production system in Belgium over a 2-year period. A sampling scheme including animal feeds and carcasses was designed to cover the entire chain of production from farrow to finishing pigs. Salmonella was detected by a method based on the use of semisolid Rappaport-Vassiliadis as a selective medium. The serotypes of the isolated strains were determined, and the antibiotic resistance of these strains to six antibiotics was also investigated. Feeds were found to be more contaminated than expected (10.2%, 34 of 332 samples). The percentage of positive fecal samples for pregnant sows (8.1%, 11 of 135 samples) was significantly higher than that for young and lactating sows (2.9%, 11 of 378 samples) (P<0.05). The percentage of positive samples for colon contents collected at the slaughterhouse (47.3%, 88 of 186 samples) was significantly higher than that for feces collected during the fattening stage (5.6%, 18 of 320 samples) (P<0.001). For carcass swab samples, the observed prevalence was 11.2% (17 of 152 samples). On farms, Salmonella recovery levels were higher for overshoe samples than for fecal samples, except for pregnant sows. Salmonella Typhimurium was the most frequently isolated serotype (32.2%, 55 of 171 samples), while Salmonella Brandenburg was predominant in the colon contents collected at the abattoir (21.4%, 18 of 84 samples). Feeds harbored a wide diversity of serotypes of minor epidemiological significance. Of 55 isolated strains of Salmonella Typhimurium, 11 (20%) were resistant to tetracycline, ampicillin, choramphenicol, streptomycin, trimethoprim, and nalidixic acid (R Type TeAmCSNa), while 12 (21.8%) were resistant to all of these antibiotics except nalidixic acid (R Type TeAmCS). The majority of Salmonella Typhimurium strains that exhibited resistance to more than four antimicrobial agents were characterized as Salmonella Typhimurium DT104 or as being closely related to Salmonella Typhimurium DT104 (7 of 12 isolates). In conclusion, our system of surveillance is effective in identifying most points of contamination in the production chain and will be useful in ongoing efforts to develop a Salmonella-free production system.     

济南市肉鸡生产链沙门菌污染监测及分析

了解肉鸡孵化、养殖、屠宰加工和配送分销各环节的沙门菌污染状况,确定易受污染的环节和样品类别,为预防和控制由沙门菌引起的食源性疾病提供科学依据。方法 按照随机抽样的原则,在济南市肉鸡孵化场、养殖场、屠宰场(点)和配送分销点设置16个监测点,按不同的季节和环节定期随机采集监测样本。检验方法按照《2012年全国食源性致病菌监测工作手册》执行。结果 监测17种样品共1204份,13种样品检出沙门菌202株,总检出率为16.78%。除1种不可分型外,其他分属4群28种血清型,以印第安纳血清型沙门菌最多(37.13%)；4个环节中,以屠宰加工环节沙门菌检出率最高(23.14%)；四个季度中,以第二季度沙门菌检出率最高(21.74%)；17种样品中,以屠宰环节的褪毛后整禽样本沙门菌检出率最高(42.19%)。结论 济南市肉鸡相关行业的沙门菌交叉污染严重,应加强肉鸡生产链全过程的监管和监测,并针对各污染环节和工序,确定不同的关键控制点,制定相应的操作程序,以减少沙门菌的交叉污染。     

Prevalence of Salmonella in two Botswana abattoir environments

A 1-year study was carried out to investigate the prevalence of Salmonella in two abattoir environments coded "A" and "B" in Gaborone, Botswana. The total number of environmental samples collected from abattoirs A and B was 250 and 300, respectively. The samples were taken from soils in the corrals, knife blades, saw blades, cattle-drinking water, cattle feces, and feed. Preenrichment, enrichment, and selective/differential media, which enabled the favorable growth of Salmonella, were used in the study. Salmonellae were present in all sampled environments. The most common serotypes found in the environment at abattoir A were E1, C1, C2, and B. Serotypes B, C1, C2, C3, and E1 were common in abattoir B. Antigenic characterization of the salmonellae isolates showed that Salmonella Anatum, Salmonella Azteca, Salmonella Saintpaul, Salmonella Cerro, and Salmonella Westhampton were predominant in abattoir A, whereas Salmonella Anatum, Salmonella Mbandaka, Salmonella Molade, Salmonella Reading, and Salmonella Oranienburg were dominant in abattoir B. Implementing hazard analysis critical control point principles in work procedures would definitely reduce the gross contamination taking place in abattoirs.     

Antimicrobials for reduction of Salmonella contamination in uncooked, surface-browned breaded chicken products

Surface-browned but uncooked frozen breaded chicken products have been associated with salmonellosis outbreaks due to inadequate or no cooking of the products before consumption. This study was conducted to evaluate the effect of three antimicrobials against Salmonella during manufacture of a surface-browned, uncooked frozen breaded chicken meat product. Fresh chicken breast meat portions (5 by 5 by 5 cm) were inoculated (4 to 5 log CFU/g) with Salmonella and mixed with caprylic acid (CAA; 0.5 and 1.0%), carvacrol (CAR; 0.3 and 0.5%), ε-polylysine (POL; 0.125 and 0.25%), or distilled water (control). Sodium chloride (1.2%) and sodium tripolyphosphate (0.3%) were added to all treatments, and the mixtures were ground (5% total moisture enhancement level) and formed into portions (9 by 5 by 3 cm). The products were breaded and surface browned by baking in an oven (208°C for 15 min) or deep frying in vegetable oil (190°C for 15 s), packaged in polyethylene bags, and stored at -20°C for 7 days. Total reductions of inoculated Salmonella in untreated control oven- or fryer-browned products after frozen storage were 1.2 and 0.8 log CFU/g, respectively. In comparison, treatment with CAA, CAR, or POL reduced initial pathogen counts by 3.3 to >4.5, 4.1 to >4.7, and 1.1 to 1.6 log CFU/g, respectively, regardless of the antimicrobial concentration and browning method. Treatment with 1.0% CAA (oven browned) or 0.5% CAR (oven or fryer browned) reduced Salmonella to nondetectable levels (<0.3 log CFU/g) in stored frozen products. These data may be useful for development of suitable antimicrobial treatments to reduce the risk of Salmonella contamination in surface-browned, uncooked frozen breaded chicken products.     

Prevalence, risk factors, and antimicrobial resistance profiles of Salmonella from commercial broiler farms in two important poultry-producing regions of Colombia

Salmonella is one of the most common foodborne pathogens associated with diarrheal disease in humans. Food animals, especially poultry, are important direct and indirect sources of human salmonellosis, and antimicrobial resistance is an emerging problem of public health concern. The use of antimicrobials benefits producers but contributes to the emergence of antimicrobial resistant bacteria. As a step toward implementing the Colombian Integrated Program for Antimicrobial Resistance Surveillance, this study was conducted to establish the prevalence, distribution of serovars, antimicrobial resistance profiles, and risk factors for Salmonella on poultry farms in the two largest states of poultry production in Colombia. Salmonella was isolated from 41% of farms and 65% of the 315 chicken houses sampled. Salmonella Paratyphi B variant Java was the most prevalent serovar (76%), followed by Salmonella Heidelberg (23%). All Salmonella isolates were resistant to 2 to 15 of the antimicrobial drugs tested in this study. For Salmonella Paratyphi B variant Java, 34 drug resistance patterns were present. The predominant resistance pattern was ciprofloxacin, nitrofurantoin, tetracycline, trimethoprim-sulfamethoxazole, ceftiofur, streptomycin, enrofloxacin, and nalidixic acid; this pattern was detected in 15% of isolates. The resistance pattern of tetracycline, ceftiofur, and nalidixic acid was found in over 40% of the isolates of Salmonella Heidelberg. Of the biosecurity practices considered, two factors were significantly associated with reduction in Salmonella: cleaning of fixed equipment and composting of dead birds on the farm. Findings from the present study provide scientific evidence to inform implementation of official policies that support new biosecurity legislation in an effort to decrease the prevalence of Salmonella on Colombian poultry farms.     

开封市畜禽沙门菌污染状况及血清学鉴定分析

了解开封市畜禽肉中沙门菌的污染状况及血清学分布,为沙门菌引起的食源性疾病的防控提供依据。方法 依据GB 4789.4—2010《中华人民共和国国家标准食品卫生微生物学检验方法》和2011年国家食源性疾病监测网监测方案,定期对开封市畜禽养殖场和屠宰场进行随机采样监测。结果 在691份样品中,沙门菌检出率为35.9%(248/691);分离出沙门菌253株,有17个血清型。结论 开封市生鸡肉和生猪肉不同程度受到沙门菌的污染,以生鸡肉污染最严重。应加强禽畜类养殖、屠宰加工等过程的卫生监管,减少食源性疾病的发生。     

淄博市肉鸡生产过程中沙门菌污染情况调查

目的了解沙门菌在肉鸡生产各个环节中的污染状况,对其污染程度及危害进行系统评价,为开展"从农场到餐桌"的风险评估以及制定防控策略提供基础数据。方法采集肉鸡孵化、养殖、屠宰、销售环节的不同样品,按照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》进行沙门菌检测。结果肉鸡生产的不同环节共采集样品1 267份,检出沙门菌阳性样品298份,总检出率为23.5%,孵化、养殖、屠宰、配送分销环节的检出率分别为4.6%(10/217)、8.4%(18/215)、32.8%(187/570)、31.3%(83/265)。印第安纳沙门菌和肠炎沙门菌为主要血清型。结论沙门菌在肉鸡生产的各个环节均有检出。各季节的检出率差异没有统计学意义(P0.05)。屠宰及销售环节的检出率较高,提示加工屠宰过程存在沙门菌交叉污染的可能,这些环节对减少鸡肉及其制品的沙门菌污染尤为重要。     

Seasonal study of aflatoxin M1 contamination in milk in five regions in Iran

Between April 2003 and February 2004, 98 samples of raw milk were obtained from milk tanks in one dairy plant in each of five regions in Iran. These were chosen with mean distances apart of 400 km, whereby they have different ecologies (temperature, relative humidity, etc.) and different agricultural products were used for animal feeding. Samples (24-25 per season) were laboratory heat treated and were analyzed for aflatoxin M1 with a validated High Performance Liquid Chromatography (HPLC) system. The overall mean of all samples was 0.041-0.065 microg/L (95% confidence) and the adjusted mean based on statistical modification was 0.039 ppb: 61 samples had 0.000-0.050 microg/L, 29 samples were contaminated with 0.05-0.10 microg/L, and the remaining 8 samples had 0.1-0.39 microg/L. All of the samples were lower than Codex Alimentarius and FDA standards (0.5 microg/L). Levels of aflatoxin M1 were higher in winter and spring than in summer and autumn, but the differences were not statistically significant (P>0.07). However, the level of aflatoxin in milk from one region (Hamedan) was significantly lower (P<0.05) than in those of the other regions (Gorgan, Rasht, Shiraz, Tehran).