Bacteriological profile of raw, frozen chicken nuggets

The bacteriological profile of raw, frozen chicken nuggets manufactured at a chicken processing facility in Queensland, Australia, was determined. Chicken nuggets are manufactured by grinding poultry, adding premixes to incorporate spices, forming the meat to the desired size and shape, applying a batter and breading, freezing, and packaging. A total of 300 frozen batches were analyzed for aerobic plate count, Escherichia coli, and Salmonella over a period of 4 years. The mean of the aerobic plate count was 5.4 log CFU/g, and counts at the 90th, 95th, and 99th percentiles were 5.7, 5.9, and 6.5 log CFU/g, respectively. The maximum number of bacteria detected was 6.6 log CFU/g. E. coli prevalence was 47%, and of the positive samples, the mean was 1.9 log CFU/g; counts at the 90th, 95th, and 99th percentiles were 2.3, 2.4, and 2.8 log CFU/g, respectively. The maximum number of E. coli was 2.9 log CFU/g. The Salmonella prevalence was 8.7%, and 57.7% of these isolates were typed as Salmonella subspecies II 4,12,[27]:b:[e,n,x] (Sofia), a low-virulence serotype well adapted to Australian poultry flocks. There was a significant relationship (P < 0.05) between season and both aerobic plate counts and E. coli counts, and no correlation between E. coli counts and Salmonella prevalence. This study provides valuable data on the bacteriological quality of raw, frozen chicken nuggets.     

A national survey of the microbiological quality of retail raw meats in Australia

A national survey of the microbiology of meat (ground beef and diced lamb) at the retail level in Australia was undertaken. For ground beef samples (n = 360), the mean aerobic plate count (APC) was 5.79 log CFU/g, and Escherichia coli was detected in 17.8% of samples; the mean population for these positive samples was 1.49 log CFU/g. Enterobacteriaceae were detected in 96.9% of samples (mean for positive samples, 3.01 log CFU/g), and coagulase-positive staphylococci were detected in 28.1% of samples (mean for positive samples, 2.18 log CFU/g). For diced lamb samples (n = 360), the mean APC was 5.71 log CFU/g, and E. coli was detected in 16.7% of samples (mean for positive samples, 1.67 log CFU/g). Enterobacteriaceae were detected in 91.1% of samples (mean for positive samples, 2.85 log CFU/g), and coagulase-positive staphylococci were detected in 22.5% of samples (mean for positive samples, 2.34 log CFU/g). Salmonella was recovered from 4 (1.1%) of the 360 ground beef samples (isolates were Salmonella Typhimurium phage types), and E. coli O157 was recovered from 1 (0.3%) of 357 samples; Campylobacter and Clostridium perfringens were not recovered from any of the 91 and 94 samples tested, respectively. Salmonella was recovered from 2 (0.6%) of the 360 diced lamb samples (serovars were Salmonella Infantis and Salmonella Typhimurium), Campylobacter was recovered from 1 (1.1%) of 95 samples, and C. perfringens was recovered from 1 (1.1%) of 92 samples.     

Hygiene indicator microorganisms for selected pathogens on beef, pork, and poultry meats in Belgium

Several bacterial indicators are used to evaluate hygiene during the meat slaughtering process. The objectives of this study were to assess the Belgian baseline data on hygienic indicators and the relationship between the indicators and zoonotic agents to establish hygiene indicator criteria for cattle, pig, and chicken carcasses and meat. The study used the results from the official Belgian surveillance plan from 2000 to 2003, which included the monitoring of Escherichia coli counts (ECC), Enterobacteriaceae counts (EC), aerobic colony counts (ACC), and Pseudomonas counts (PC). The sampling method was the wet and dry swabbing technique for cattle and pig carcasses and neck skin excision for broiler and layer chicken carcasses. The 75th and 95th percentiles of ECC were -0.20 and 0.95 log CFU/cm2 for cattle carcasses, 1.20 and 2.32 log CFU/cm2 for pig carcasses, and 4.05 and 5.24 log CFU/g for chicken carcasses. The ACC were 2.1- to 4.5-log higher than the ECC for cattle, pigs, and chickens. For cattle and pig carcasses, a significant correlation between ECC, EC, and ACC was found. ECC for pork and beef samples and EC in pig carcasses were significantly higher in samples contaminated with Salmonella. In poultry samples, ECC were in general higher for samples containing Salmonella or Campylobacter. Thus, E. coli may be considered as a good indicator for enteric zoonotic agents such as Salmonella for beef, pork, and poultry samples and for Campylobacter in poultry samples.     

Efficacy of UV light treatment for the microbiological decontamination of chicken, associated packaging, and contact surfaces

UV light was investigated for the decontamination of raw chicken, associated packaging, and contact surfaces. The UV susceptibilities of a number of Campylobacter isolates (seven Campylobacter jejuni isolates and three Campylobacter coli isolates), Escherichia coli ATCC 25922, and Salmonella enterica serovar Enteritidis ATCC 10376 in liquid media were also investigated. From an initial level of 7 log CFU/ml, no viable Campylobacter cells were detected following exposure to the most intense UV dose (0.192 J/cm(2)) in liquid media (skim milk subjected to ultrahigh-temperature treatment and diluted 1:4 with maximum recovery diluent). Maximum reductions of 4.8 and 6.2 log CFU/ml were achieved for E. coli and serovar Enteritidis, respectively, in liquid media. Considerable differences in susceptibilities were found between the Campylobacter isolates examined, with variations of up to 4 log CFU/ml being observed. UV treatment of raw chicken fillet (0.192 J/cm(2)) reduced C. jejuni, E. coli, serovar Enteritidis, total viable counts, and Enterobacteriaceae by 0.76, 0.98, 1.34, 1.76, and 1.29 log CFU/g, respectively. Following UV treatment of packaging and surface materials, reductions of up to 3.97, 4.50, and 4.20 log CFU/cm(2) were obtained for C. jejuni, E. coli, and serovar Enteritidis, respectively (P < 0.05). Overall, the color of UV-treated chicken was not significantly affected (P ≥ 0.05). The findings of this study indicate that Campylobacter is susceptible to UV technology and that differences in sensitivities exist between investigated isolates. Overall, UV could be used for improving the microbiological quality of raw chicken and for decontaminating associated packaging and surface materials.     

One-year (2003) nationwide pork carcass microbiological baseline data survey in Taiwan

From January through December 2003, swab samples from 1,650 pork carcasses were collected from 39 slaughter plants in Taiwan. These samples were analyzed for the prevalence of indicator microorganisms and specific pathogens. Viable aerobic bacteria, total coliforms, and Escherichia coli were recovered from 100, 95.3, and 87.5% of these carcasses, respectively. Of those carcasses that harbored bacteria, the mean aerobic plate, total coliform, and Escherichia coli counts were 4.0, 0.6, and 0.1 log CFU/cm2, respectively. Staphylococcus aureus, Clostridium perfringens, Campylobacter jejuni, Campylobacter coli, Listeria monocytogenes, and Salmonella were recovered from 4.8, 0.3, 13.8, 0.7, and 1.7 of 1,038 carcasses, respectively. E. coli O157:H7 was not detected from any carcass. When positive for a specific pathogen, the mean carcass concentration was 0.57 log CFU/cm2 for S. aureus, 0.66 most probable number (MPN)/cm2 for C. jejuni and C. coli, and 0.18 MPN/cm2 for Salmonella. The findings of this study will help provide a reference for establishing hygienic standards and a criterion for evaluating the effects of slaughtering operations in Taiwan.     

Effect of acidified sodium chlorite treatment on chicken carcases processed in South Australia

A trial on the effectiveness of acidified sodium chlorite (ASC) on Salmonella and Campylobacter was undertaken on chicken carcases after they exited the screw chiller of a commercial premises in Adelaide, Australia. On untreated carcases mean log10 total viable count (25 degrees C) was 2.78/cm2 compared with 1.23/cm2 on treated carcases. Prevalence of E. coli, Salmonella and Campylobacter was 100%, 90% and 100% respectively, on untreated carcases and 13%, 10% and 23% respectively, on treated carcases. The distributions of E. coli, Salmonella and Campylobacter (mean log10 of positive samples) from untreated carcases were 1.55, -1.80 and 1.59/cm2 respectively, and -0.64, -1.85 and -2.21/cm2 respectively, on treated carcases. On untreated carcases S. Sofia and S. Infantis were isolated from 73% and 37% of carcases, respectively; only S. Sofia was isolated from treated carcases. The significant reductions in both prevalence and concentration demonstrated in the present trial indicate that ASC is a risk management option immediately available to the poultry industry.     

Microbiological quality and safety of ready-to-eat street-vended foods in Johannesburg, South Africa

Fifty-one ready-to-eat street foods, 18 dishwater, and 18 surface swab samples were collected from six vendors in Johannesburg, South Africa. Food temperatures were recorded at the time of sampling. Standard methods were used to determine aerobic plate counts (APCs), spore counts (SCs), and Enterobacteriaceae counts (ECs) for food samples as well as coliform counts (CCs) for water and swab samples. In addition, Petrifilm Escherichia coli count (PC) plates were used for the enumeration of coliforms in food, water, and swab samples. The presence of selected foodborne pathogens in the food samples as well as the presence of nonpathogenic E. coli 1 (in food and water samples) was also tested for. Predominant colonies isolated from APC plates were characterized to the genus level. Holding temperatures for cooked meats and gravies ranged from 42.0 to 94.0 degrees C, and those for uncooked salads ranged from 29.0 to 39.0 degrees C. Mean APC values of 3.4 (+/-0.4) log CFU/g, 4.0 (+/-1.2) log CFU/ml, and 2.1 (+/-0.4) log CFU/25 cm2 were obtained for food, water, and swab samples, respectively. Mean SC values of 1.6 (+/-0.2) log CFU/g and 1.5 (+/-0.3) log CFU/25 cm2 were obtained for food and swab samples, respectively. A mean EC value of 2.0 (+/-0.4) log CFU/g for food samples and mean CC values of 2.5 (+/-0.3) log CFU/ml and 1.3 (+/-0.3) log CFU/25 cm2 for water and swab samples, respectively, were determined. Mean PC values of 1.6 (+/-0.1) log CFU/g, 1.9 (+/-0.6) log CFU/ml, and 1.4 (+/-0.4) log CFU/25 cm2 were determined for food, water, and swab samples, respectively. Bacillus cereus was detected in 22%, Clostridium perfringens in 16%, Salmonella spp. in 2%, and E. coli (non-O157:H+) in 2% of the 51 food samples. E. coli was found in 14 water samples (78%) and in 3 food samples (6%). Campylobacter spp., Listeria monocytogenes, Staphylococcus aureus, Vibrio cholerae, and Yersinia enterocolitica were also tested for in the food samples, but they were not detected. The 340 isolates obtained from APC plates for food, water, and swab samples were predominantly Bacillus spp., Micrococcus spp., and Staphylococcus spp. for all three sample types. It was concluded that the foods analyzed in this study were of acceptable quality and safety.     

A national survey of the microbiological quality of beef carcasses and frozen boneless beef in Australia

The third national baseline microbiological survey of Australian beef carcasses and frozen boneless beef was conducted in 2004. Carcasses (n=1155) sampled at 27 slaughter establishments had a mean aerobic plate count (at 25 degrees C) of 1.3 log CFU/cm2. Escherichia coli was isolated from 8.0% of the cacasses, with a mean count of -0.8 log CFU/cm2 for positive samples. On samples from 24 boning (fabrication) plants (n=1082), the mean aerobic plate count for frozen boneless beef was 1.3 log CFU/g, and the mean count for the 1.8% of samples with detectable E. coli was 1.5 log CFU/g. E. coli O157: H7 was isolated from 1 of 1,143 carcasses and from 0 of 1082 boneless samples. Salmonella was isolated from 0 of 1155 carcasses and from 1 of 1082 samples of boneless product. No Campylobacter spp. were isolated from carcasses or boneless beef. Coagulase-positive staphylococci were isolated from 28.7% of beef carcasses and 20.3% of boneless beef samples, and positive samples had a mean count of 0.3 log CFU/cm2 and 0.8 log CFU/g, respectively.     

A survey of the microbiological quality of kangaroo carcasses processed for human consumption in two processing plants in Queensland, Australia

An investigation of the microbiological quality of kangaroo carcasses at two Queensland processing plants was carried out. A total of 836 whole muscle samples were taken, 801 from plant A and 35 from plant B. Samples were analyzed for aerobic bacteria, Escherichia coli, and Salmonella. The mean adjusted aerobic plate count (APC) was 2.8 log CFU/g, and counts at the 90th, 95th, and 99th percentiles were 4.2, 4.9, and 6.4 log CFU/g, respectively. The maximum number of bacteria recovered was 6.5 log CFU/g. E. coli was detected in 13.9% of samples, for which the adjusted mean was 0.7 log CFU/g, and counts at the 90th, 95th, and 99th percentiles were 1.4, 2.0, and 3.0 log CFU/g, respectively. Salmonella was detected in 0.84% of samples. There was no significant relationship (P < 0.05) between season and APC or E. coli count. There was a significant relationship (P < 0.001) between Salmonella prevalence and summer. The microbiological quality of Queensland kangaroo carcasses is similar to that obtained during other excision-based studies of kangaroo, wild boar, and beef carcasses.     

Microbiological baseline study of broiler chickens at Swedish slaughterhouses

This 1-year study was conducted to estimate the prevalence and concentrations of pathogenic and indicator bacteria on Swedish broiler chickens. A total of 636 chilled carcasses were collected from 10 slaughterhouses and sent to the National Food Administration for analyses of carcass rinses. No carcasses were positive for Salmonella. Campylobacter, predominantly Campylobacter jejuni, were detected on 15% (by enrichment) or 14% (by direct plating) of the carcasses. With one exception, all samples from late December through April were Campylobacter negative. The 10th and 90th percentiles of Campylobacter numbers per carcasses were 3.0 and 5.0 log CFU, respectively, and the maximum was 7.1 log CFU. Coagulase-positive staphylococci were detected on 68% of the carcasses, with a maximum of 3.5 log CFU/cm2. The 10th and 90th percentiles were 3.4 and 4.4 log CFU/cm2 for total aerobic microorganisms, 1.8 and 3.3 log CFU/cm2 for Enterobacteriaceae, and 2.0 and 3.6 log CFU/cm2 for Escherichia coli. No correlation was found between numbers of any indicator bacteria and numbers of pathogenic bacteria. Subsets of the samples were analyzed for Listeria monocytogenes, Clostridium perfringens, pathogenic Yersinia enterocolitica, and Enterococcus, resulting in prevalence estimates of 29, 18, 9 (as determined by a PCR assay), and 97%, respectively. L. monocytogenes was most common at slaughterhouses with a low prevalence of coagulase-positive staphylococci, and vice versa. These results will improve the ability of researchers to assess the importance of chicken as a source of foodborne pathogens and can serve as a basis for risk management actions.     

Microbiological status of Australian sheep meat.

Two studies were undertaken to determine the microbiological status of sheep carcass meat and frozen, bulk-packed sheep meat produced in Australia. Samples were collected from 470 sheep carcasses and 415 cartons of frozen sheep trimmings over a period of approximately 12 months. Samples were collected from plants processing sheep carcasses for domestic or export markets. On carcasses, where bacterial counts were obtained, the mean of the log10 aerobic plate count (APC) was 3.92/cm2, the geometric mean of the most probable number (MPN) per square centimeter of Escherichia coli (biotype I) was 23, and the geometric mean of the coliform count was 38 MPN per cm2. A high percentage (75%) of samples was positive for E. coli (biotype I), 81% were positive for coliforms, 5.74% were positive for Salmonella spp., and 1.29% were positive for Campylobacter. Bacterial counts were higher on carcasses chilled over a weekend than on carcasses chilled for 24 h. The total number of bacteria on carcasses processed for domestic markets was similar to that on carcasses processed for export markets. E. coli O157 was not isolated from any of the 465 samples tested. Of the frozen export samples that tested positive, the mean of the log10 APC was 3.47/g, the geometric mean of the E. coli (biotype I) count was 9 MPN per g, and the geometric mean of the coliform count was 19 MPN per g. Of the frozen export samples tested, 48% were positive for E. coli (biotype I), 58% were positive for coliforms, and 6.5% were positive for Salmonella spp. E. coli O157 was recovered from 1 of 343 frozen sheep meat samples tested (0.29%). Bacterial counts were higher on samples of domestic product than on samples of export product. Results from both surveys are compared with data from similar studies conducted in other countries.     

Microbial contamination occurring on lamb carcasses processed in the United States

Lamb carcasses (n = 5,042) were sampled from six major lamb packing facilities in the United States over 3 days during each of two visits (fall or winter, October through February; spring, March through June) in order to develop a microbiological baseline for the incidence (presence or absence) of Salmonella spp. and for populations of Escherichia coli after 24 h of chilling following slaughter. Samples also were analyzed for aerobic plate counts (APC) and total coliform counts (TCC). Additionally, incidence (presence or absence) of Campylobacter jejuni/coli on lamb carcasses (n = 2,226) was, determined during the slaughtering process and in the cooler. All samples were obtained by sponge-sampling the muscle-adipose tissue surface of the flank, breast, and leg of lamb carcasses (100 cm2 per site; 300 cm2 total). Incidence of Salmonella spp. in samples collected from chilled carcasses was 1.5% for both seasons combined, with 1.9% and 1.2% of fall or winter and spring samples being positive, respectively. Mean (log CFU/cm2) APC, TCC, and E. coli counts (ECC) on chilled lamb carcasses across both seasons were 4.42, 1.18, and 0.70, respectively. APC were lower (P < 0.05) in samples collected in the spring versus fall or winter, while TCC were higher in samples collected in the spring. There was no difference (P > 0.05) between ECC from samples collected in the spring versus winter. Only 7 out of 2,226 total samples (0.3%) tested positive for C. jejuni/coli, across all sampling sites. These results should be useful to the lamb industry and regulatory authorities as new regulatory requirements for meat inspection become effective.     

Microbiological baseline study of swine carcasses at Swedish slaughterhouses

This 13-month survey was conducted to estimate the prevalence and counts of foodborne pathogenic bacteria and indicator bacteria on swine carcasses in Sweden. A total of 541 swine carcasses were sampled by swabbing prechill at the 10 largest slaughterhouses in Sweden. Pathogenic Yersinia enterocolitica was detected by PCR in 16% of the samples. The probability of finding Y. enterocolitica increased with increasing counts of Escherichia coli. No samples were positive for Salmonella. The prevalences of Campylobacter, Listeria monocytogenes, and verocytotoxin-producing E. coli were low (1, 2, and 1%, respectively). None of the verocytotoxin-positive enrichments, as determined by a reverse passive latex agglutination assay, tested positive for the virulence genes eaeA or hlyA by PCR. Coagulase-positive staphylococci, E. coli, and Enterobacteriaceae were recovered from 30, 57, and 87% of the samples, respectively, usually at low levels (95th percentiles, 0.79, 1.09, and 1.30 log CFU/cm2, respectively). The mean log level of Enterobacteriaceae was 0.35 log CFU/cm2 higher than that of E. coli on carcasses positive for both bacteria. The mean log level of aerobic microorganisms was 3.48 log CFU/cm2, and the 95th percentile was 4.51 log CFU/cm2. These data may be useful for risk assessment purposes and can serve as a basis for risk management actions, such as the use of E. coli as an alternative indicator organism for process hygiene control.     

Quantification of Campylobacter on the surface and in the muscle of chicken legs at retail

The objective of this study was to determine the prevalence and numbers of Campylobacter on the skin and in the muscle of chicken legs at retail to examine the external and internal contamination for an exposure assessment. Furthermore, the study assessed seasonal influence on Campylobacter contamination in chicken legs. Of the 140 examined skin samples, 66% were positive, and the internal contamination of 115 sampled chicken legs was 27%. The enumeration of Campylobacter on the surface of positive chicken legs revealed a median of 2.4 log CFU/g of skin, and the quantification of Campylobacter in the muscle gave results mainly under the detection limit of the most-probable-number method (<0.3 MPN Campylobacter per g). The external contamination was significantly higher than the internal. In both skin and muscle samples, Campylobacter jejuni had a much higher incidence than Campylobacter coli. However, with regard to the specification of Campylobacter on the surface of chicken legs, C. coli was isolated at higher colony counts than C. jejuni. During the 1-year study, two peaks of Campylobacter contamination occurred, one in the early springtime (February and March, 100 and 90%, respectively) and the second during the warmer months in the summer (July and August, both 90%). Furthermore, a positive correlation between prevalence and numbers of Campylobacter on chicken legs was observed.     

Effect of fecal contamination and cross-contamination on numbers of coliform, Escherichia coli, Campylobacter, and Salmonella on immersion-chilled broiler carcasses

The effect of prechill fecal contamination on numbers of bacteria on immersion-chilled carcasses was tested in each of three replicate trials. For each trial, 16 eviscerated broiler carcasses were split into 32 halves and assigned to one of two groups. Cecal contents (0.1 g inoculated with Campylobacter and nalidixic acid-resistant Salmonella) were applied to each of eight halves in one group (direct contamination) that were placed into one paddle chiller (contaminated), whereas the other paired halves were placed into another chiller (control). From the second group of eight split birds, one of each paired half was placed in the contaminated chiller (to determine cross-contamination) and the other half was placed in the control chiller. Postchill carcass halves were sampled by a 1-min rinse in sterile water, which was collected and cultured. Bacterial counts were reported as log CFU per milliliter of rinsate. There were no significant statistical differences (paired t test, P < 0.05) from direct contamination for coliforms (mean 3.0 log CFU) and Escherichia coli (mean 2.7 log CFU), although Campylobacter numbers significantly increased from control values because of direct contamination (1.5 versus 2.1 log CFU), and the incidence increased from 79 to 100%. There was no significant effect of cross-contamination on coliform (mean 2.9 log CFU) or E. coli (mean 2.6 log CFU) numbers. Nevertheless, Campylobacter levels were significantly higher after exposure to cross-contamination (1.6 versus 2.0 log CFU), and the incidence of this bacterium increased from 75 to 100%. Salmonella-positive halves increased from 0 to 42% postchill because of direct contamination and from 0 to 25% as a result of cross-contamination after chilling. Water samples and surface swabs taken postchill from the contaminated chiller were higher for Campylobacter than those taken from the control chiller. Immersion chilling equilibrated bacterial numbers between contaminated and control halves subjected to either direct contamination or cross-contamination for coliforms and E. coli. Campylobacter numbers, Campylobacter incidence, and Salmonella incidence increased because of both direct contamination and cross-contamination in the chiller. Postchill E. coli numbers did not indicate which carcass halves were contaminated with feces before chilling.     

Prevalence and antimicrobial susceptibility of major foodborne pathogens in imported seafood

Seafood is a leading commodity implicated in foodborne disease outbreaks in the United States. Seafood importation rose dramatically in the past 3 decades and now contributes to more than 80% of the total U.S. seafood supply. However, limited data are available on the microbiological safety of imported seafood. In this study, we obtained a total of 171 salmon, shrimp, and tilapia samples imported from 12 countries in three retail stores in Baton Rouge, LA. The total microbial population and the prevalence and antimicrobial susceptibilities of six major foodborne-pathogen genera (Campylobacter, Escherichia coli, Listeria, Salmonella, Shigella, and Vibrio) were determined. The aerobic plate counts (APC) for the 171 samples averaged 4.96 log CFU/g, with samples from Chile carrying the highest mean APC of 6.53 log CFU/g and fresh samples having a significantly higher mean APC than frozen ones (P < 0.0001). There were 27 samples (15.8%) with unacceptable microbiological quality (APC > 7 log CFU/g). By culture, no sample tested positive for Campylobacter coli, Shigella, or Vibrio vulnificus. Campylobacter jejuni and Salmonella enterica serovar Typhimurium were each recovered once from farm-raised tilapia from China. By PCR, 17.5 and 32.2% of the samples were positive for Salmonella and Shigella, respectively. The overall prevalence rates of other target bacteria were low, ranging from 4.1% for Listeria monocytogenes to 9.4% for E. coli. All of the Vibrio parahaemolyticus isolates recovered were from shrimp, and 63.3% showed intermediate resistance to ampicillin. Both C. jejuni isolates possessed a rare resistance to gentamicin, while 75% of L. monocytogenes isolates were resistant to nitrofurantoin. Taken together, these findings suggest potential food safety hazards associated with imported seafood and warrant further large-scale studies.     

Effect of dry air or immersion chilling on recovery of bacteria from broiler carcasses

A study was conducted to investigate the effect of chilling method (air or immersion) on concentration and prevalence of Escherichia coli, coliforms, Campylobacter, and Salmonella recovered from broiler chicken carcasses. For each of four replications, 60 broilers were inoculated orally and intracloacally with 1 ml of a suspension containing Campylobacter at approximately 10(8) cells per ml. After 1 day, broilers were inoculated with 1 ml of a suspension containing Salmonella at approximately 10(8) cells per ml. Broilers were processed, and carcasses were cooled with dry air (3.5 m/s at -1.1 degrees C for 150 min) or by immersion chilling in ice water (0.6 degrees C for 50 min). Concentrations of E. coli, coliforms, Campylobacter, and Salmonella recovered from prechill carcasses averaged 3.5, 3.7, 3.4, and 1.4 log CFU/ml of rinse, respectively. Overall, both chilling methods significantly reduced bacterial concentrations on the carcasses, and no difference in concentrations of bacteria was observed between the two chilling methods (P < 0.05). Both chilling methods reduced E. coli and coliforms by 0.9 to 1.0 log CFU/ml. Air and immersion chilling reduced Campylobacter by 1.4 and 1.0 log CFU/ml and reduced Salmonella by 1.0 and 0.6 log CFU/ml, respectively. Chilling method had no effect on the prevalence of Campylobacter and Salmonella recovered from carcasses. These results demonstrate that air- and immersion-chilled carcasses without chemical intervention are microbiologically comparable, and a 90% reduction in concentrations of E. coli, coliforms, and Campylobacter can be obtained by chilling.     

Monochloramine versus sodium hypochlorite as antimicrobial agents for reducing populations of bacteria on broiler chicken carcasses

Studies were conducted to compare the effect of sodium hypochlorite (SH) versus monochloramine (MON) on bacterial populations associated with broiler chicken carcasses. In study 1, nominal populations (6.5 to 7.5 log CFU) of Escherichia coli, Listeria monocytogenes, Pseudomonas fluorescens, Salmonella serovars, Shewanella putrefaciens, and Staphylococcus aureus were exposed to sterilized chiller water (controls) or sterilized chiller water containing 50 ppm SH or MON. SH at 50 ppm eliminated all (6.5 to 7.5 log CFU) viable E. coli, L. monocytogenes, and Salmonella serovars; 1.2 log CFU of P. fluorescens; and 5.5 log CFU of S. putrefaciens. MON eliminated all (6.5 to 7.5 log CFU) viable E. coli, L. monocytogenes, S. putrefaciens, and Salmonella serovars and 4.2 log CFU of P. fluorescens. In study 2, chicken carcasses were inoculated with P. fluorescens or nalidixic acid-resistant Salmonella serovars or were temperature abused at 25 degrees C for 2 h to increase the populations of naturally occurring E. coli. The groups of Salmonella serovar-inoculated or temperature-abused E. coli carcasses were immersed separately in pilot-scale poultry chillers and exposed to tap water (controls) or tap water containing 20 ppm SH or 20 ppm MON for 1 h. The P. fluorescens-inoculated group was immersed in pilot-scale poultry chillers and exposed to tap water (controls) or tap water containing 50 ppm SH or 50 ppm MON for 1 h. Carcasses exposed to the SH treatment had nominal increases (0.22 log CFU) in E. coli counts compared with controls, whereas exposure to MON resulted in a 0.89-log reduction. Similarly, average nalidixic acid-resistant Salmonella serovar counts increased nominally by 34% (41 to 55 CFU/ml) compared with controls on carcasses exposed to SH, whereas exposure to MON resulted in an average nominal decrease of 80% (41 to 8 CFU/ml). P. fluorescens decreased by 0.64 log CFU on carcasses exposed to SH and decreased by 0.87 log CFU on carcasses exposed to MON. In study 3, SH or MON was applied to the chiller in a commercial poultry processing facility. E. coli counts (for carcass halves emerging from both saddle and front-half chillers) and Salmonella prevalence were evaluated. Data from carcasses exposed to SH during an 84-day historical (Hist) and a 9-day prepilot (Pre) period were evaluated. Other carcasses were exposed to MON and tested during a 27-day period (Test). E. coli counts for samples collected from the saddle chiller were 25.7, 25.2, and 8.6 CFU/ml for Hist, Pre, and Test, respectively. E. coli counts for samples collected from the front-half chiller were 6.7, 6.9, and 2.5 CFU/ml for Hist, Pre, and Test, respectively. Salmonella prevalence was reduced from 8.7% (Hist + Pre) to 4% (Test). These studies indicate that MON is superior to SH in reducing microbial populations in poultry chiller water.     

Effect of temperature on viability of Campylobacter jejuni and Campylobacter coli on raw chicken or pork skin

To determine growth and survival of Campylobacter jejuni and Campylobacter coli on chicken and pork, Campylobacter spp. (10(4) CFU/cm2) were inoculated on pieces of raw, irradiated chicken or pork skin and exposed to temperatures ranging from -20 to 42 degrees C under either microaerobic or aerobic conditions. Viable counts over 48 h declined 2 to 3 log CFU/cm2 at -20 degrees C and 1 to 2 log CFU/cm2 at 25 degrees C regardless of skin type, species of Campylobacter, or level of oxygen. At 4 degrees C, there was no significant change in the number of Campylobacter over 48 h. At both 37 and 42 degrees C, the number of viable Campylobacter increased significantly (2 to 3 log CFU/cm2, P < 0.0001) under microaerobic conditions but decreased 0.5 to 1.5 log CFU/cm2 in air. Preincubation of skins for 24 h at 42 degrees C under microaerobic conditions to establish Campylobacter on the surface prior to lowering the temperature to -20, 4, or 25 degrees C and incubating in air resulted in a decline in viability for the first 4 h (0.5 to 1 log CFU/cm2). However, after this initial drop in viability, no additional effect on viability was observed compared with incubation at -20, 4, or 25 degrees C in air without microaerobic preincubation at 42 degrees C. Preincubation of inoculated skins at -20, 4, or 25 degrees C in air for 24 h followed by a shift in temperature to 42 degrees C for 4, 8, 24, or 48 h and a shift to microaerobic conditions resulted in an overall decline in viability on raw pork skin but not on raw chicken skin. In contrast, preincubation of inoculated skins at -20, 4, or 25 degrees C for 24 h in air followed by a shift in temperature to 37 degrees C and microaerobic conditions did not result in a decrease in viable counts for either chicken or pork skins. Overall, viability of C. coli and C. jejuni on chicken and pork skins was similar. Therefore, a lower incidence of Campylobacter spp. in pork than in poultry postslaughter, despite a similar prevalence in live animals, is not due to differences in viability of C. coli versus C. jejuni on raw chicken or pork skin.     

Assessment of post-Hurricane Katrina recovery in poultry slaughter establishments

Control of bacterial contamination during poultry slaughter can be compromised by natural disaster. In October 2005, disaster recovery was evaluated in 11 broiler slaughter establishments 1 month after operations were disrupted by Hurricane Katrina. A questionnaire was administered to characterize the establishment's operational disruption. Carcass rinses were collected at the early and late stage of the slaughter process (rehang and postchill). Counts for generic Escherichia coli were determined for all rinses. Salmonella culture and serotyping were performed on postchill samples. Historical U.S. Food Safety and Inspection Service data on the presence of Salmonella also were examined. The mean duration of disruption was 6.3 days (range, 3 to 9 days). Loss of utilities (electricity and water) was the cause of prolonged recoveries. Most establishments (64%) did not exceed the m performance criteria threshold for generic E. coli (>2 log or 100 CFU/ml) during the recovery period. The mean reduction in E. coli counts between rehang and postchill was 2.3 log or 200 CFU/ml (range, 0.9 to 3.1 log CFU/ ml). Rinse samples from 5 of 11 establishments were positive for Salmonella. Of 12 Salmonella isolates that were recovered, eight were Salmonella Kentucky. Salmonella Heidelberg and Salmonella Thompson were recovered from one establishment, and two isolates of Salmonella Typhimurium were isolated from another. This study provided empirical reassurance that the establishments' processes controlled bacterial contamination. Data on reductions in E. coli counts during poultry slaughter may help establishments control microbial contamination. Other data (e.g., Salmonella and Campylobacter enumeration) may also have merit for this purpose.