Using indicator bacteria and Salmonella test results from three large-scale beef abattoirs over an 18-month period to evaluate intervention system efficacy and plan carcass testing for Salmonella

To develop a process for predicting the likelihood of Salmonella contamination on beef carcasses, we evaluated the influence of several possible causative factors (i.e., year, abattoir, day of week, month, and intervention system components) on the risk of Salmonella and indicator organism contamination. Hide and carcass sponge samples were collected in 2005 to 2006 in six steps at three abattoirs in the East (A), Midwest (B), and Southwest (C) United States. Each abattoir used the same intervention system. Samples were analyzed for aerobic plate counts (APCs; n = 18,990) and Enterobacteriaceae counts (EBCs; n = 18,989) and the presence or absence of Salmonella (n = 5,355). Our results demonstrated that many factors play a significant role in the level of microbial contamination of beef carcasses. Overall, Salmonella prevalence and EBC levels were significantly higher in 2006 than in 2005. APCs and EBCs were highest in abattoirs A (3.57 log CFU/100 cm2) and B (1.31 log CFU/100 cm2). The odds of detecting a positive Salmonella isolate were greatest in abattoir C and lowest in abattoir A. Across the three abattoirs, the overall intervention process effectively reduced microbiological contamination. Salmonella prevalence fell from 45% (preevisceration) to 0.47% (postchilled-lactic acid), and there were APC and EBC reductions of 5.43 and 5.28 log CFU/100 cm2, respectively, from hide-on to postchilled-lactic acid samples. At each abattoir, composites of three individual EBC-negative carcass samples yielded Salmonella-negative results 97 to 99% of the time. These results suggest the possibility of using indicator test results to accurately predict the absence of Salmonella in a beef carcass sample.     

OCCURRENCE OF ESCHERICHIA COLIO157:H7/O157, LISTERIA MONOCYTOGENES AND SALMONELLA SPP. IN BEEF SLAUGHTERHOUSE ENVIRONMENTS, EQUIPMENT AND WORKERS

Escherichia coli O157/O157:H7, Listeria monocytogenes and Salmonella spp. are major foodborne pathogens and the emergence of these pathogens has been reported in many countries. The aim of this study was to investigate contamination of the beef slaughterhouse environment, equipment and workers with E. coli O157/O157:H7, L. monocytogenes and Salmonella spp. For this study, 500 swab samples were taken from 19 different points in five privately owned slaughterhouses, their periphery, slaughterhouse equipment and slaughterhouse employees. The presence of E. coli O157:H7/O157, L. monocytogenes and Salmonella spp. was determined with the application of the immunomagnetic separation method. Our study showed that the swabs taken from the five slaughterhouses contained E. coli O157:H7 in the environment, equipment, abattoir workers and water with a frequency 0.31, 1, 1.42 and 0%, respectively; while E. coli O157 was evident in the environment, equipment, abattoir workers and water with a ratio of 15, 10, 10 and 0%, respectively; L. monocytogenes was detected in the environment, equipment, abattoir workers and water at a ratio of 4.37, 15, 5.71 and 0%, respectively; and Salmonella spp. occurrence in the environment, equipment, abattoir workers and water at a ratio of 3.43, 16, 11.42, and 0%, respectively. Implementing hazard analysis critical control point principles in work procedures would definitely reduce the gross contamination occurring in abattoirs.

PRACTICAL APPLICATIONS

This study has revealed the effect of personnel and equipment on the contamination routes of E. coli O157:H7, Listeria monocytogenes and Salmonella spp. in meat in slaughterhouses and showed that especially L. monocytogenes and Salmonella spp. may pose a higher risk than E. coli O157:H7 in slaughterhouses.     

Assessment of carcass contamination with E. coli O157 before and after washing with water at abattoirs in Nigeria

The study was carried out to assess the level of beef carcass contamination with Escherichia coli including O157 strains before and after washing with water. Samples of water used for washing carcasses were collected and thirty beef carcasses were swabbed within a period of one month in each of three abattoirs located in North-Western states of Nigeria. E. coli were enumerated as indicator organisms. Using conventional biochemical tests, the isolation rate of E. coli in the 120 swab samples collected in each abattoir from external and internal surfaces of the carcasses was 58.3% at Kano abattoir, 70.8% at Sokoto abattoir, while 76.7% was recorded at Zango abattoir. E. coli counts from external and internal surfaces of the carcasses were enumerated as mean log and ranged between 4.3 Log(10) and 4.6 Log(10) cfu/cm(2) before washing, while the values were 4.6 Log(10) and 4.9 Log(10) cfu/cm(2) after washing. Data analysis revealed that the increase in E. coli counts after washing carcasses with water was statistically significant (P<0.05) in all the abattoirs. However, there was no statistically significant difference (P>0.05) between the 3 abattoirs in mean log of E. coli counts from external surfaces of carcass after washing. E. coli O157 was identified from both the water and surfaces of carcasses using Latex agglutination kit. A prevalence of 2.8% of E. coli O157 was detected in 360 swab samples from 90 beef carcasses examined. E. coli counts from water used in washing carcasses were between 22 and 120 cfu/100 ml. Of the 72 water samples, 3(4.2%) were positive for E. coli O157. In conclusion, there was increased contamination of carcasses during processing and water used in washing carcasses might have contributed to carcass contamination in all the abattoirs studied due to use of non-potable water.     

Prevalence and characterization of Salmonella infantis isolates originating from different points of the broiler chicken-human food chain in Hungary

During the 10-month study period Salmonella contamination of broiler houses and the flocks reared in three farms (A, B and C), the slaughter houses where the flocks were slaughtered, as well as the carcass and retail raw meat products originating from them was investigated. In the broiler farm A five consecutive flocks, in the B and C farms one flock was sampled. Environmental samples were taken prior to the introductions. Environmental, drinking water, feed and faecal samples were collected regularly using standard methods. Before and during processing of the flocks, environmental and carcass samples were taken at the abattoirs. Salmonella contamination of the carcass, retail meat, as well as stool samples of farm and abattoir workers and from human illnesses registered in the same period and region were also examined. Isolation, sero-, phage- and antibiotic resistance typing, class 1 integron and plasmid profiling of the strains were performed; their genetic relationship was assessed by PFGE. Although the broiler house and the faecal samples of the 5 flocks of the farm A were negative for Salmonella, S. infantis was isolated from 20-100% of the abattoir carcass samples. The retail raw meat samples were 0-100% S. infantis positive. The environmental samples of farm B were Salmonella negative, but the examined flock was contaminated: S. infantis was identified from 43% of the faecal samples. This serotype was identified in 100% of the carcass and retail raw meat samples. From environmental samples taken before the arrival of the 1-day-old chicks in the broiler house C, S. infantis was cultured. S. infantis prevalence in the faecal samples was 35% and all the carcass and retail raw meat samples were S. infantis contaminated. Altogether 164 S. infantis strains were isolated out of which 145 were further characterized. The vast majority (142/145) of the strains belonged to phage types 217 and 213. All but one were characterized by the nalidixic acid-streptomycin-sulphonamide-tetracycline resistances, had an 885 bp class 1 integron and a large plasmid of >168 kb in size. The strains showed >/=88.7% genetic similarity. The results obtained shows that the same multi-drug resistant S. infantis clone was spread from the examined broiler farms contaminating the slaughter and the retail meat and appeared in the human illnesses of the examined region that was earlier detected as the dominant clone characteristic of the broiler and human population of the whole country.     

Survey of Salmonella serotypes shed in feces of beef cows and their antimicrobial susceptibility patterns

Salmonella prevalence on cow-calf operations was studied as a part of a national study of health and management of the U.S. beef cow-calf industry and was conducted as part of the National Animal Health Monitoring System. Within this study, the prevalence of Salmonella spp. shed in feces was determined. A total of 5,049 fecal samples were collected from 187 beef cow-calf operations each visited on a single occasion. The number of fecal samples collected per operation was predetermined based on herd size. Salmonellae were recovered from 1 or more fecal samples collected on 11.2% (21 of 187) of the operations. Overall 78 salmonellae representing 22 serotypes were recovered from 1.4% (70 of 5,049) of samples. Multiple serotypes were recovered from eight samples from a single operation. The five most common serotypes were Salmonella Oranienburg (21.8% of isolates), and Salmonella Cerro (21.8%), followed by Salmonella Anatum (10.3%), Salmonella Bredeney (9.0%), and Salmonella Mbandaka (5.1%). The most common serogroups identified were C1 (33.3%), K (21.8%), B (16.7%), and E (15.4%). Even though the recovery rate of salmonellae from fecal samples was very low, 43.6% (34 of 78) and 38.5% (30 of 78) of the isolates were among the 10 most common serotypes from cattle with clinical signs of disease or isolated from humans, respectively. The majority of the isolates (50 of 78; 64.1%) were recovered from fecal samples from two operations. All isolates were screened for resistance to a panel of 17 antimicrobics, and 87.2% (68 of 78) were susceptible to all of the antimicrobics. The resistant isolates were most commonly resistant to streptomycin (n = 9) and/or sulfamethoxazole (n = 9). Nine isolates showed multiple (> or =2 antimicrobics) resistance most commonly to streptomycin and sulfamethoxazole (n = 6).     

Incidence of coagulase positive Staphylococcus on beef carcasses in three Australian abattoirs.

The contamination of beef carcasses with coagulase-positive staphylococci (CPS) was studied at three beef abattoirs (A, B and C). The incidence and the number of CPS were determined on cattle hides immediately after slaughter and on three carcass sites (brisket, flank and round) at different points during processing along the slaughter line. The incidence of CPS on cattle hides ranged from 20 to 68.6%. At abattoir A, 6.5% of the carcasses sampled before evisceration were contaminated with CPS, compared to 40% of the carcasses after evisceration. The incidence on carcasses changed little during further processing; however, after chilling for 72 h, the incidence increased to 83%. After evisceration, the brisket and flank areas were more often contaminated than the round. A similar pattern of contamination was observed at abattoir B. At abattoir C, 26.7% of the samples collected before evisceration were contaminated and this fell to 16.7% after evisceration. After chilling for 72 h, the incidence of carcass contamination with CPS increased to 46.7%. The average number of CPS on contaminated carcasses prior to and after overnight chilling was less than 50 colony-forming units (cfu)/cm2 and, after weekend chilling, increased to 64 and 112 cfu/cm2 in abattoirs A and B, respectively. Of the isolates tested, 71.4% produced staphylococcal enterotoxin and 21% could not be classified phenotypically. The hands of workers and environmental sites associated with the evisceration process were examined for CPS at abattoir A. Hands were heavily contaminated and were the likely source of CPS contamination at this abattoir.     

Microbiological monitoring of sheep carcass contamination in three Swiss abattoirs

At three Swiss abattoirs, 580 sheep carcasses were examined at 10 sites by the wet-dry double-swab technique. The aim of this study was to obtain data on microbiological contamination at the abattoirs and to develop a procedure for monitoring slaughter hygiene. Median aerobic plate counts (APCs) (log CFU/cm2) ranged from 2.5 to 3.8, with the brisket and neck sites showing the most extensive contamination. Enterobacteriaceae were detected on 68.1% of the carcasses and in 15.2% of the samples. The proportion of positive results ranged from 2.6% (for the hind leg and the flank at abattoir C) to 42.2% (for the perineal area at abattoir A). The percentage of samples testing positive for stx genes by polymerase chain reaction was 36.6%. A significant relationship between APC and the detection of Shiga toxin-producing Escherichia coli (STEC) was found for abattoirs A and B (depending on sampling site), whereas a significant relationship between Enterobacteriaceae and STEC detection was confirmed only for abattoir A (P < 0.05). In 57.1% of the 56 isolated non-O157 strains, stx2 genes were detected, and most of them were stx2d positive. Additional virulence factors were detected in 50% of the STEC strains, with 8.9% of these strains being eae positive, 50% being EHEC-hlyA positive, and 3.6% being astA positive. For the determination of carcass contamination, the monthly examination of 10 sheep carcasses for APC and Enterobacteriaceae counts in the neck, brisket, and perineal areas is recommended. This procedure is a valuable tool for the verification of slaughter hygiene according to hazard analysis critical control point principles.     

Microbiological contamination of cattle and pig carcasses at five abattoirs determined by swab sampling in accordance with EU Decision 2001/471/EC

A total of 800 cattle carcasses (abattoir A: n=200; B: n=150; C: n=150; D: n=150, E: n=150) and 650 pig carcasses (abattoir A: n=200; B: n=150; C: n=150; D: n=150) were examined at five Swiss abattoirs with an annual slaughtering capacity >10 million kg. Weekly, 10 cattle and 10 pig carcasses were sampled at four sites by the wet-dry double swab technique. From each carcass the samples were pooled and examined for total viable counts (TVC) and Enterobacteriaceae. At the abattoirs, mean log TVCs from cattle carcasses ranged from 2.1 to 3.1 cm(-2) and those from pig carcasses from 2.2 to 3.7 cm(-2). Daily TVC mean log values showed significant differences between abattoirs (P<0.05), whereas no significant differences were detected between animal species. On average, Enterobacteriaceae were detected (i) in low counts, (ii) on 31.0% of cattle and on 20.2% of pig carcasses, and (iii) more frequently and in higher counts on cattle than on pig carcasses (P<0.05). Data from this study indicate that the wet-dry double swab technique is suitable to determine microbiological contamination of cattle and pig carcasses in accordance with EU Decision 2001/471/EC. For samples obtained by the non-destructive technique from cattle and pig carcasses, the following microbiological performance criteria are proposed: Daily mean log values are acceptable, marginal, and unacceptable for TVC when they are <3.00, 3.00-4.00, >4.00 cm(-2), and for Enterobacteriaceae when they are <1.00, 1.00-2.00, and >2.00 cm(-2). However, such values have to be seen merely as baselines. It is important to implement a monitoring system based on abattoir-specific data and criteria as permitted by quality control chart methods.     

Microbiological sampling of swine carcasses: a comparison of data obtained by swabbing with medical gauze and data collected routinely by excision at Swedish abattoirs

Swab sample data from a 13-month microbiological baseline study of swine carcasses at Swedish abattoirs were combined with excision sample data collected routinely at five abattoirs. The aim was to compare the numbers of total aerobic counts, Enterobacteriaceae, and Escherichia coli, recovered by swabbing four carcass sites with gauze (total area 400 cm2) with those obtained by excision at equivalent sites (total area 20 cm2). The results are considered in relation to the process hygiene criteria that are stated in Commission Regulation (EC) No 2073/2005. These criteria apply only to destructive sampling of total aerobic counts and Enterobacteriaceae, but alternative sampling schemes, as well as alternative indicator organisms such as E. coli, are allowed if equivalent guarantees of food safety can be provided. Swab sampling resulted in higher mean log numbers of total aerobic counts at four of the five abattoirs, compared with excision, and lower or equal standard deviations at all abattoirs. The percentage of swab and excision samples positive for Enterobacteriaceae at the different abattoirs ranged from 68 to 100% and 15 to 24%, respectively. Similarly, the percentages of swab samples that were positive for E. coli were higher than the percentages of positive excision samples (range 52 to 84% and 3 to 14%, respectively). Due to the low percentage of positive excision results, the mean log numbers of Enterobacteriaceae and E. coli were only compared at two and one abattoirs, respectively, using log probability regression to substitute censored observations. Higher mean log numbers of Enterobacteriaceae were recovered by swabbing compared with excision at one abattoir, whereas the numbers of Enterobacteriaceae and E. coli did not differ significantly between sampling methods at one abattoir. This study suggests that the same process hygiene criteria as those stipulated for excision can be used for swabbing with gauze without compromising food safety. For monitoring of low numbers of Enterobacteriaceae and E. coli, like those found on swine carcasses at Swedish abattoirs, the results also show that swabbing of a relatively large area is superior to excision of a smaller area.     

Contamination of bovine carcasses and abattoir environment by Escherichia coli O157:H7 in Istanbul

The aim of this study was to investigate contamination of carcasses and abattoir environment with Escherichia coli O157:H7. Five abattoirs in Istanbul were visited between January 2000 and April 2001. During visits, sampling was performed and a total of 330 cattle were selected. Cattle were examined for the presence of faeces on the hide (abdomen and legs) before slaughter. The swabs from the carcasses and environmental samples (abattoir floor, benches including conveyors, knives, aprons, saws, hooks, hands) were taken at the abattoir immediately after slaughter using sterile cotton swabs. A sample from the wash water of the abattoir was also taken. Preenrichment, immunomagnetic separation and CT-SMAC agar were used for the isolation. The reaction of the isolates with anti-O157 and H7 antisera were also analysed. Twelve strains (3.6%) of E. coli O157 were isolated from the cattle carcasses and eight (2.4%) of them gave positive reaction with anti-H:7. Six strains of E. coli O157 were isolated from the environmental samples and all strains were positive for H7. The number of E. coli O157H:7 strains isolated from the environmental samples was two from the knife, two from the hands, one from the apron and one from the floor. No E. coli O157 was isolated from the abattoir water.     

Rabbit meat as a source of bacterial foodborne pathogens

Even though worldwide production of rabbit meat is >1,000,000 tons, little information is available for rabbit meat microbiology. This study provides data on the prevalence of Salmonella, Escherichia coli O157:H7, Yersinia enterocolitica, Listeria spp., motile Aeromonas spp., and Staphylococcus aureus on rabbit meat. A total of 24 rabbit carcasses from two abattoirs and 27 rabbit meat packages from supermarket displays were examined. In addition to culturing methods, associated virulence genes were investigated by PCR in suspect isolates and samples. Neither Salmonella nor E. coli O157:H7 was detected. All samples were negative for virulence-associated invA, stx1, and stx2 genes. At one abattoir, two carcasses (3.9%) carried Y. enterocolitica yst-, and two were positive for the yst gene, although viable Y. enterocolitica cells were not recovered from these samples. Seven samples (13.7%) were contaminated with Listeria. Of them, three were positive for hly and iap genes (Listeria monocytogenes hly+ / iap+), two carried Listeria seeligeri, one carried Listeria ivanovii, and one carried Listeria innocua. For detectable motile Aeromonas spp. (average count, 1.77 +/- 0.62 log CFU/g), the contamination rate was 35.3%, although ca. 90% of the samples were positive for the aerA and/or hlyA genes. The majority of aeromonad isolates were Aeromonas hydrophila aerA+ / hlyA+. Aeromonas caviae, Aeromonas popoffii, Aeromonas schubertii, and the two biovars of Aeromonas veronii were also isolated. The prevalence of S. aureus contamination (average count, 1.37 +/- 0.79 log CFU/g) was 52.9%. Among 27 S. aureus isolates, two harbored genes for staphylococcal enterotoxin B (seb), and two harbored genes for staphylococcal enterotoxin C (sec). The remaining isolates were negative for sea, seb, sec, sed, and see.     

Antimicrobial drug resistance of Salmonella and Escherichia coli isolates from cattle feces, hides, and carcasses

To determine patterns of cross-contamination and antibiotic susceptibility of microorganisms commonly associated with cattle, 60 cattle shipped to a commercial abattoir (20 in each of three separate trial periods) were followed through processing. Samples for bacterial isolation were collected from the feces and hides immediately before shipping, from the hides at the abattoir after exsanguination, and from the carcasses before evisceration and in the cooler. Samples were cultured for Salmonella and non-type-specific Escherichia coli. Salmonella was identified in 33.9% (n = 20) of the fecal samples and on 37.3% (n = 22) of the hides before shipment. At the abattoir, the proportion of hides from which Salmonella was isolated increased (P < 0.001) to 84.2% (48 hides). Nonspecific E. coli and Salmonella were recovered from 40.4 and 8.3% of preevisceration carcass samples, respectively. No Salmonella or nonspecific E. coli were recovered from hotbox carcass samples. Isolates were tested for antimicrobial drug susceptibility. For nonspecific E. coli, 80.3% (n = 270) of the isolates were resistant to at least one antimicrobial drug. For Salmonella, 97% (n = 101) of the isolates were resistant to at least one antimicrobial drug; however, only 4.0% were resistant to two or more. The most common resistance was to sulfamethoxazole. These results indicate that the presence of microorganisms resistant to antimicrobial drugs is common in cattle and beef. Further studies are needed to identify the sources and causes of this drug resistance.     

Salmonella spp. shedding by alberta beef cattle and the detection of Salmonella spp. in ground beef

Breeder cows, cattle recently arrived at feedlots, and cattle about to be shipped for slaughter were tested for Salmonella spp. No Salmonella spp. were detected in fecal samples from breeding cows. Nineteen of 1,000 (1.9%) fecal samples from recently arrived feedlot cattle were positive for Salmonella spp. compared to only 2 of 1,000 (0.2%) fecal samples taken within 2 weeks of slaughter. The positive fecal samples were collected in 5 of 50 (10%) "recent arrival" pens tested and in 1 of 50 (2%) pens tested within 2 weeks of slaughter. The serotypes isolated were Salmonella Agona, Salmonella Enteritidis, Salmonella Typhimurium DT104, and Salmonella 4,5,12:i:-. Ground beef samples purchased from retail outlets throughout Alberta were processed for Salmonella spp. Thirteen of 1,002 (1.3%) samples were positive for Salmonella spp. The serotypes isolated from ground beef were Salmonella Anatum, Salmonella Heidelberg, Salmonella Montevideo, Salmonella Typhimurium, Salmonella Typhimurium var. Copenhagen, and Salmonella Rough-O:i:1,2. The antibiotic resistance and pulsed-field electrophoresis gel macrorestriction patterns of all isolates were compared.     

Salmonella cross-contamination in swine abattoirs in Portugal: Carcasses, meat and meat handlers

In this study the occurrence of Salmonella in swine, pork meat and meat handlers along with their clonal relatedness is evaluated at abattoir level. Samples from the lymph nodes, carcass surface and meat of 100 pigs and 45 meat handlers were collected in eight abattoirs (July 2007-August 2008). Salmonella isolates were serotyped and genotyped by pulsed-field gel electrophoresis (PFGE). From the pigs tested, 42 produced at least one positive sample. A relatively high frequency of Salmonella occurrence was found in the ileoceacal lymph node samples (26.0%), followed by carcass (16.0%) and meat samples (14.0%). However, ileoceacal lymph nodes that test positive for Salmonella are not found to be a predictor of positive test results further on in the process. Besides the slaughterhouse environment, meat handlers were identified as a possible source of subsequent contamination, with 9.3% of the sample testing positive. Diverse Salmonella enterica serotypes were detected, mainly S. Typhimurium and the monophasic variant S. 4,[5],12:i:-, but also S. Derby, S. Rissen, S. Mbandaka, S. London, S. Give, S. Enteritidis and S. Sandiego, in total corresponding to 17 PFGE types. Our results demonstrate that besides a high level of Salmonella swine contamination at pre-harvest level, slaughtering, dressing, cutting and deboning operations are contributing to the occurrence of clinically relevant clones (e.g. S. Typhimurium DT104 and S. 4,[5],12:i:-) in pork products. This study also highlights the possibility of an ongoing Salmonella community being spread by abattoir workers.     

The bacteriological quality of British beef 1. Carcasses sampled prior to chilling

During a survey of 11 beef abattoirs in England 2200 swab samples were taken from carcasses just before chilling. Geometric mean aerobic plate counts at 30°C on each of four carcass sites ranged from log(10) 2·45 to 4·29cfu cm(2) with the brisket and flank samples tending to be more highly contaminated than those from the fore-rib and groin. Presumptive coliforms were isolated from 24% of the samples and the proportion of positive samples among the abattoirs varied between 1·5% and 43%. Analysis of variance confirmed that the bacteriological status of beef carcasses may be influenced by a number of interacting factors, including abattoir, visit, and sampling site. However, the results showed that working methods alone were not critical factors in the production of beef of superior bacteriological quality.     

Quantity and distribution of Salmonella recovered from three swine lairage pens

The quantity of Salmonella recoverable from three lairage pens in a swine abattoir was determined. Using dry four-ply cotton gauze pads measuring 10 by 10 cm, 100 fecal slurry samples were collected from each of the three pens. Salmonella recovery was expressed as the log CFU per milliliter of sample. Mean values were 2.5 log CFU/ml in pen A, 2.7 log CFU/ ml in pen B, and 0.89 log CFU/ml in pen C. Median values were 2.6 log CFU/ml in pen A, 2.0 log CFU/ml in pen B, and below the detectable limit in pen C. In pen C, Salmonella was not recoverable from a high number of samples. Pen B results suggested spatial dependency, i.e., samples close together were more similar than samples farther apart. These results indicate that Salmonella concentrations vary within and between lairage pens. Because of the limited number of pens assessed, it was not possible to identify factors that were associated with the observed variation in Salmonella concentrations within and between pens. However, this variation suggests that numeroussamples are required to adequately describe the concentration of Salmonella in a lairage pen.     

Detection and frequency of VT1, VT2 and eaeA genes in Escherichia coli O157 and O157:H7 strains isolated from cattle, cattle carcasses and abattoir environment in Istanbul

The aim of this study was to detect VT1, VT2 and eaeA genes and to determine the frequency of these genes in Escherichia coli O157 and O157:H7 strains isolated from cattle, cattle carcasses and environmental samples of the 5 abattoirs located in Istanbul, Turkey. For this, the presence of VT1, VT2 and eaeA genes in 26 strains of E. coli O157:H7 and 6 strains of O157 was investigated by multiplex-PCR. The results have shown that eaeA gene was detected in all O157 and O157:H7 strains tested. Both VT2 and eaeA genes were detected in 4 (80%) of 5 strains of E. coli O157 and eaeA alone in 1 strain of O157. In 27 strains of O157:H7, 5 (18.5%) strains were found to be positive for VT1, VT2 and eaeA genes, 19 (70.3%) strains for both VT2 and eaeA and, 3 (11.1%) strains for only eaeA gene. Either VT1 alone or VT2 alone was not detected in any strains tested. eaeA gene alone in 2 strains, VT2-eaeA genes in 9 strains and VT1-VT2-eaeA genes in 2 strains were detected in 13 of E. coli O157:H7 strains isolated from cattle. eaeA alone in 1 strain, VT2-eaeA genes in 5 strains and VT1-VT2-eaeA genes in 2 strains were detected in 8 of E. coli O157:H7 strains isolated from carcasses. VT2-eaeA genes in 5 strains (isolated from hands, apron, knife and floor) and VT1-VT2-eaeA genes in 1 strain (isolated from knife) were also detected in 6 of E. coli O157:H7 strains isolated from environmental samples. This study reveals that most of the strains are found to be toxigenic and it is most likely that strains isolated from carcasses and abattoir environment originated from cattle feces. Therefore, HACCP systems are necessary from farm to table especially in the abattoirs to prevent contamination of meat and abattoir environment with intestinal content.     

Prevalence of Salmonella enterica, Listeria monocytogenes, and Escherichia coli virulence factors in bulk tank milk and in-line filters from U.S. dairies

The zoonotic bacteria Salmonella enterica, Listeria monocytogenes, and Escherichia coli are known to infect dairy cows while not always causing clinical signs of disease. These pathogens are sometimes found in raw milk, and human disease outbreaks due to these organisms have been associated with the consumption of raw milk or raw milk products. Bulk tank milk (BTM) samples (536) and in-line milk filters (519) collected from dairy farms across the United States during the National Animal Health Monitoring System's Dairy 2007 study were analyzed by real-time PCR for the presence of S. enterica and pathogenic forms of E. coli and by culture techniques for the presence of L. monocytogenes. S. enterica was detected in samples from 28.1% of the dairy operations, primarily in milk filters. Salmonella was isolated from 36 of 75 PCR-positive BTM samples and 105 of 174 PCR-positive filter samples, and the isolates were serotyped. Cerro, Kentucky, Muenster, Anatum, and Newport were the most common serotypes. L. monocytogenes was isolated from 7.1% of the dairy operations, and the 1/2a complex was the most common serotype, followed by 1/2b and 4b (lineage 1). Shiga toxin genes were detected in enrichments from 15.2% of the BTM samples and from 51.0% of the filters by real-time PCR. In most cases, the cycle threshold values for the PCR indicated that toxigenic strains were not a major part of the enrichment populations. These data confirm those from earlier studies showing significant contamination of BTM by zoonotic bacterial pathogens and that the consumption of raw milk and raw milk products presents a health risk.     

Thermal inactivation D- and z-values of multidrug-resistant and non-multidrug-resistant Salmonella serotypes and survival in ground beef exposed to consumer-style cooking

There has been speculation that multidrug-resistant (MDR) strains are generated by subtherapeutic antibiotic use in food animals and that such strains result in increased resistance to lethality by food processes such as heat and irradiation. The objective of this study was to evaluate the heat resistance of 20 strains, namely an MDR and a non-multidrug-resistant (NMDR) strain of each of 10 Salmonella serotypes isolated from cattle or cattle environments. MDR and NMDR Salmonella serotypes studied included Montevideo, Typhimurium, Anatum, Muenster, Newport, Mbandaka, Dublin, Reading, Agona, and Give. For phase I, stationary-phase cultures of the strains were aliquoted into sterile capillary tubes and immersed in a temperature-controlled water bath at 55, 60, 65, and 70 degrees C for appropriate times. Survivor curves were plotted for each temperature, and a best-fit linear regression was derived for each temperature. D-values (decimal reduction times) and z-values (changes in temperature required to change the D-values) were calculated for each strain. Although there was no overall significant difference in the heat resistance of MDR and NMDR serotypes, NMDR serotypes generally appeared to have slightly higher heat resistance than NMDR serotypes, especially at 55 and 60 degrees C. The highest relative heat resistance (highest z-values) was exhibited by Salmonella Anatum. Notably, the relative heat resistance of NMDR Salmonella Agona was similar to that of NMDR Salmonella Anatum and had the highest D-values at all four temperatures. For phase II, three serotypes (regardless of resistance profile) with the highest relative heat resistance and their drug-resistant counterparts were selected for thermal inactivation in ground beef patties cooked to endpoint temperatures. Salmonella Agona was able to survive in ground beef cooked to an internal temperature of 71 degrees C. Results of these studies suggest drug resistance does not affect the heat resistance of Salmonella and that serotype or strain is an important consideration in risk assessment of the pathogen with regard to survival at cooking temperatures.     

Effect of preslaughter events on the prevalence of Salmonella in market-weight turkeys

The goal of this study was to determine if preslaughter events, such as transport to and holding at the slaughterhouse, affect Salmonella prevalence in turkeys. Floors of transport crates were swabbed after loading and prior to transport at the farm (time 1, n = 100 swabs per trial) and after transport to and holding at the abattoir (time 2, n = 100 swabs per trial). In addition, environmental samples were taken at each of the six premises (n = 25 per premises) as well as in the holding shed at the abattoir (n = 25 samples per trial). At slaughter, the crops, ceca, and spleens were cultured (n = 50 each per flock). As shown from the culture of the crate floor swabs collected pre- and posttransport, when individual farms were analyzed, samples from only one premises exhibited a statistically significant change, as seen by the decline in Salmonella prevalence posttransport (P < 0.01). When the data from all farms were combined, Salmonella was recovered more frequently from swabs collected pretransport at loading on-farm (time 1, 47.6%) than from swabs collected after transport (time 2, 39.7%, P < 0.01). This suggests that transport to and holding at the abattoir do not increase the prevalence of Salmonella in turkeys. This observation contrasts with the increase in Salmonella prevalence reported for hogs and some broilers.