Tracing Campylobacter jejuni strains along the poultry meat production chain from farm to retail by pulsed-field gel electrophoresis, and the antimicrobial resistance of isolates

In this study Campylobacter jejuni isolates were recovered from birds, carcasses and carcass portions from two broiler chicken flocks and from equipment used for carcass and meat processing along the production chain from farms to retail stores. Isolates were subjected to pulsed-field gel electrophoresis (PFGE) using SmaI and KpnI restriction enzymes and their antimicrobial susceptibilities were determined. C. jejuni was recovered from product and equipment used with both flocks at each point in the production chain. The prevalence of C. jejuni in poultry products at retail stores was 58.97% (flock 1) and 69.23% (flock 2). SmaI divided 122 C. jejuni strains from flock 1 and 106 from flock 2 into 17 and 13 PFGE types, respectively. PFGE types H and F were present at all steps along the chain, from farms to retail products. Similarly, for both flocks PFGE type D was detected in crates, slaughterhouse and retail stores. Moreover, the PFGE types were highly diverse at the processing and retail steps. Most PFGE types were resistant to ciprofloxacin (95.45%) and tetracycline (81.82%); and multidrug resistant PFGE types were found in the final products. Our study showed that there were several points of cross-contamination of product along the chain, and a high diversity of PFGE types with antimicrobial resistance to ciprofloxacin and tetracycline in the retail products.     

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

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

Molecular characterization and antibiotic resistance profiling of Campylobacter isolated from cattle in Polish slaughterhouses

A total of 812 samples from bovine hides and the corresponding carcasses collected at the slaughterhouse level in the eastern part of Poland were examined for the presence of Campylobacter jejuni and Campylobacter coli. Recovered isolates were confirmed using species-specific PCR, characterized by the presence of 11 putative virulence genes and antimicrobial susceptibility was determined using a microbroth dilution method. Furthermore, the genotypic relatedness of the isolates was determined by PFGE profiling and virulence pattern cluster analysis. The prevalence of Campylobacter was 25.6% and 2.7% in bovine hide and carcass samples, respectively. The presence of virulence markers varied between C. jejuni and C. coli species however, the majority of strains possessed the cadF, flhA, flaA genes, irrespective of the bacterial species and origin. The lower number of the strains was positive for the invasive associated markers – virB11 and wlaN. Antibiotic profiling showed that campylobacters were most frequently resistant to quinolones and fluoroquinolones (nalidixic acid and ciprofloxacin, 38.3% of each, respectively) followed by streptomycin (24.3%) and tetracycline (20.9%). Resistance to erythromycin and gentamicin was demonstrated in 4.3% and 2.6% of strains, respectively. Comparisons of the PFGE and virulence marker profiles of the isolates reflected the high genetic diversity of Campylobacter tested. Moreover, a poor correlation between the PFGE type, pathogenic gene marker and antimicrobial resistance patterns was observed.     

PorA specific primers for the identification of Campylobacter species in food and clinical samples

Campylobacteriosis is a public health problem with considerable socio-economic impact. As the European Food Safety Authority has emphasized the importance of a surveillance programme for campylobacteriosis, the aim of the present study was the optimization of a specific and sensitive PCR protocol able to detect Campylobacter species responsible for gastrointestinal infections. Raw poultry meat samples were analysed for the presence of Campylobacter sp., by plating onto mCCD (Modified Charcoal-Cefoperazone-Deoxycholate) Agar and Campylobacter Selective Preston Agar and using four sets of species-specific primers for Campylobacter jejuni, Campylobacter coli, Campylobacter upsaliensis and Campylobacter lari designed to bridge the porA gene. The resulting primers demonstrated a sensitivity of 0.01 ng/μl for the C. coli-specific, C. lari-specific, and C. upsaliensis-specific primer sets and 0.5 ng/μl for the C. jejuni-specific primer sets using DNA from pure cultures. Non-specific amplification of non-target DNA was not observed indicating excellent specificity. The primers were useful for the analyses of poultry meat samples both for direct plating onto mCCDA, and for DNA extracted directly from the cells grown for 48 h in Preston enrichment broth. The sets of primers were also useful when used for species identification of human isolates.     

Seasonal influence on the prevalence of thermotolerant Campylobacter in retail broiler meat in Denmark

In Denmark, the incidence of human campylobacteriosis cases, as well as the Campylobacter prevalence in broiler flocks, is strongly influenced by season with a summer peak in July-August. Therefore, it was considered that the prevalence of Campylobacter in broiler meat sold at retail in Denmark might also be influenced by season. A retrospective survey analysis was performed on 2001-2007 national surveillance data of the prevalence of thermotolerant Campylobacter in all conventional broiler flocks at slaughter, and in randomly sampled broiler meat at retail. There was a significant effect of season on the occurrence of Campylobacter in meat at retail; the largest effect was found for domestic chilled meat. Thus, the Campylobacter prevalence in Danish broiler flocks, which fluctuated with season, was found to be a strong predictor for the occurrence of Campylobacter in fresh, chilled, Danish broiler meat. However, besides flock prevalence, there was also a direct effect of season on the occurrence of Campylobacter in Danish broiler meat at retail.     

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.     

The biofilm forming potential of bacterial species in the genus Campylobacter

The biofilm forming abilities of 16 strains representative of 14 of the 16 species comprising the genus Campylobacter were determined on glass, stainless steel, and polystyrene plastic. The formation of biofilms has been suggested as a means by which Campylobacter is able to persist within an inhospitable environment. Of the eight microaerophilic Campylobacter species, including two strains each of Campylobacter jejuni and Campylobacter fetus, only C. jejuni strain 81–176 reliably produced a visible biofilm on multiple surfaces. Alternately, all six strains of the anaerobic Campylobacter species reliably produced visible biofilms on multiple surfaces. Electron micrographs of the individual biofilms showed relatively homogeneous biofilms produced by the anaerobic strains, while the microaerophilic C. jejuni strain 81–176 produced a biofilm containing similar quantities of both the spiral and coccoid forms. This survey suggests a difference in the biofilm forming potentials and the morphologies of the bacteria comprising the biofilms between anaerobic and microaerophilic species of Campylobacter. Additionally, differences observed in the biofilm forming ability of two strains of C. jejuni suggest the need for a further investigation of the biofilm forming potential of this species using a larger number of strains.     

Antimicrobial resistance in Campylobacter coli isolated from pigs in two provinces of China

The aim of this study was to determine the prevalence, antimicrobial resistance and molecular epidemiology of Campylobacter coli isolated from swine in China. A total of 190 C. coli isolates obtained from two slaughter houses and ten conventional pig farms in Shandong (SD, n = 95) and Ningxia (NX, n = 95) provinces were tested for their susceptibility to 14 antimicrobials. A high prevalence (> 95%) of ciprofloxacin and tetracycline-resistant strains was observed in both SD and NX. The erythromycin and clindamycin resistance rates of C. coli from NX (ERY: 54.7% CLI: 43.2%) were higher than those from SD (ERY: 37.9%, CLI: 35.8%). A significant difference (P < 0.05) was observed in erythromycin resistance rate, but not (P > 0.05) in clindamycin resistance rate. while the resistance rates of ampicillin and kanamycin in NX (AMP: 34.7%, KAN: 43.2%) were significantly lower (P < 0.05) than those in SD (AMP: 51.6%, KAN: 71.6%). None of the tested isolates were resistant to phenicols. The majority of the isolates from both provinces (SD: 80% and NX: 73.7%) showed multi-drug resistance profiles. The point mutations of A2075G in the 23S rRNA and C257T in the gyrA gene were detected in 98% (87/89) of macrolide resistant isolates and all ciprofloxacin resistant isolates, respectively. In addition, all tetracycline-resistant isolates harbored the tet(O) gene. The high prevalence of antimicrobial resistance in C. coli strains derived from pigs in China was observed and was likely due to the extensive use of various antimicrobials. Prudent use of antimicrobial agents on farms should be further emphasized to control the dissemination of antimicrobial resistant C. coli.     

Long-term persistence of specific genetic types of mastitis-causing Staphylococcus aureus on three dairies

Pulsed-field gel electrophoresis (PFGE) after SmaI digestion was used to investigate the persistence of specific genotypes of bovine mammary gland isolates of Staphylococcus aureus on 3 dairy herds. A total of 341 isolates of Staph. aureus were available from cows in 3 herds, collected over a period of 15 yr. Pulsed-field gel electrophoresis band patterns of Staph. aureus isolates were analyzed visually and with gel analysis and comparison software. Based on this analysis, isolates were classified by PFGE type. Persistence was determined as the time period from the first to the last isolation of a particular PFGE type of Staph. aureus within a herd. Specific types of mastitis-causing Staph. aureus persisted long-term on these dairies. For example, PFGE type 3 isolates persisted on farms A, B, and C for 15, 15, and 13 yr, respectively. Type 6 was found to persist for 13 yr on farm C. Despite the application of standard mastitis control practices, mastitis-causing Staph. aureus types appeared to persist long-term, as detected by PFGE, and were isolated coincident with herd problems of increased milk somatic cell counts and decreased milk production.     

Genotyping of dairy Bacillus licheniformis isolates by high resolution melt analysis of multiple variable number tandem repeat loci

In dairy foods, the sporeformer Bacillus licheniformis can be the cause of spoilage or specification compliance issues. Currently used methods for genotyping B. licheniformis have limited discrimination with only 2 or 3 different subgroups being identified. Here, we have developed a multi-locus variable number tandem repeat analysis (MLVA) method and combined it with high resolution melt analysis (MLV-HRMA) for genotyping B. licheniformis. Five repetitive loci were identified and used as markers for genotyping 52 isolates from two milk powder processing plants and retail samples. Nineteen genotypes could be identified using both MLVA and MLV-HRMA leading to Hunter–Gaston discrimination indices (D-value) of 0.93 each. It was found that all 5 MLVA loci were stable following 10 days of sub-culturing of 8 representative isolates. All isolates were also genotyped using previously used methods including randomly amplified polymorphic DNA-PCR (RAPD) and partial rpoB sequencing. Five different RAPD profiles and 5 different partial rpoB sequence types were identified resulting in corresponding D-values of 0.6 and 0.46, respectively. Analysis of the genotypes from dairy samples revealed that dairy B. licheniformis isolates are more heterogeneous than previously thought and that this new method can potentially allow for more discriminatory tracking and monitoring of specific genotypes.     

Genetic diversity of mastitis-associated Klebsiella pneumoniae in dairy cows

The objectives of this study were to determine the level of genetic diversity of Klebsiella pneumoniae isolated from clinical mastitis cases and to define genotypes most commonly associated with the disease. Individual quarter milk samples were collected from a single privately owned dairy herd over a 2-yr period and submitted to the Laboratory for Udder Health, Minnesota Veterinary Diagnostic Laboratory, University of Minnesota, for bacteriological culture. Eighty-four K. pneumoniae isolates were obtained and fingerprinted by repetitive DNA sequence PCR, 43 by pulsed-field gel electrophoresis (PFGE), and 29 by multilocus sequence typing (MLST). Significant genetic diversity was observed among the isolates regardless of the fingerprinting method used. Simpson's diversity index was 93.5, 96.1, and 97.0% when analyzed by repetitive DNA sequence PCR (n = 84), pulse field gel electrophoresis (n = 43), and MLST (n = 29), respectively. In some cases more than 1 genotype was obtained from a single milk sample originating from an individual quarter. The majority of infections were observed during the winter and accounted for 69.0% of K. pneumoniae mastitis cases. There was a negative correlation between a matrix of fingerprints similarity and a matrix of temporal distances. The MLST results revealed 5 new and novel allelic types, which have not been previously reported in the MLST database. Three isolates shared MLST types with human clinical isolates, raising the possibility that some K. pneumoniae isolates, of bovine origin, may be capable of causing disease in humans. There were 21 genotypes present within the herd, and there was no evidence for nonrandom distribution of genotypes uniquely associated with mastitis. We have shown, using 3 distinct genotyping methods, that K. pneumoniae isolated from clinical mastitis within a single dairy herd is caused by a genetically diverse population and that multiple genotypes can be isolated from a mastitic quarter. The data suggest that mastitis can be caused by a variety of K. pneumoniae genotypes. Diverse genotypes may have different levels of invasiveness and virulence and may originate from various sources within the dairy.     

Molecular characterization of antibiotic resistant Salmonella isolates from Indian foods

Salmonella isolates belonging to five serovars, Salmonella enterica Ohio, S. Oslo, S. Tennessee, S. Weltevreden and S. Typhimurium, isolated during 2006-2008 from food samples like sprouts and different varieties of fresh water and marine fish were tested for antibiotic resistance. High percentages (97%) of the isolates were resistant to at least one antibiotic and 82% of the isolates were resistant to more than one antibiotic. S. Oslo was the most resistant serovar and it exhibited resistance to 13 out of 16 antibiotics tested. Integron 1, which has been shown to confer multidrug resistance to various Salmonella serovars, was detected in multidrug resistant S. Oslo. PFGE studies revealed that serovars showed very high genetic diversity. The multidrug resistant S. Oslo showed unique PFGE pattern, which could be used in epidemiological studies.     

The combination of CRISPR-MVLST and PFGE provides increased discriminatory power for differentiating human clinical isolates of Salmonella enterica subsp. enterica serovar Enteritidis

Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) is a major cause of foodborne salmonellosis. Rapid, efficient and accurate methods for identification are required to track specific strains of S. Enteritidis during outbreaks of human salmonellosis. By exploiting the hypervariable nature of virulence genes and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs), we previously developed a powerful sequence-based subtyping approach, designated CRISPR-MVLST. To substantiate the applicability of CRISPR-MVLST, we analyzed a broad set of S. Enteritidis isolates collected over a six-year period. Among 141 isolates we defined 22 Enteritidis Sequence Types (ESTs), the majority of which were novel. Notably, strains exhibiting the common PFGE pattern, JEGX01.0004 (characteristic of ∼40% of S. Enteritidis isolates in the United States), were separated into twelve distinct sequence types. Conversely, isolates of EST4, the most predominant EST we observed, comprised eight different PFGE patterns. Importantly, we showed that some genotypes that were previously associated with the food supply chain at the farm level have now been identified in clinical samples.     

Prevalence and characterization of antimicrobial resistance of foodborne Listeria monocytogenes isolates in Hebei province of Northern China, 2005-2007

A total of 2177 food samples collected from nine cities in northern China during 2005 to 2007 were screened for the presence of Listeria monocytogenes. All L. monocytogenes isolates were subjected to serotyping, antimicrobial susceptibility, pulsed-field gel electrophoresis (PFGE), as well as PCR screening to identify genes responsible for tetracycline resistance [tet(L), tet(M), tet(K), tet(S) and tet(B)], transposon Tn916, and class 1 integron. Contamination with L. monocytogenes was detected in 4.13% (90/2177) of the total samples representing various food products. The pathogen was mainly isolated from frozen food made of wheat flour or rice products (26/252, 10.32%) and raw meat products (46/733, 6.28%). Besides, 3.31% (10/302) of cooked meat, 1.17% (4/343) of seafood, 0.98% (2/204) of non-fermented bean products and 0.62% (2/323) of vegetables samples were contaminated by this bacterium. The L. monocytogenes isolates belonged to five serotypes (1/2a, 1/2b, 1/2c, 4b, and 3a), with serotype 1/2a being dominant (48.88%). Antimicrobial resistance was most frequently observed for ciprofloxacin (17.8%), tetracycline (15.6%) and streptomycin (12.2%). Overall, resistance was observed against 14 out of 18 antimicrobials tested while multiple resistances occurred among 18.9% (17/90) isolates. Interestingly, two isolates were resistant to more than five antimicrobials. Among 14 tetracycline-resistant isolates, 13 carried tet(M) gene including nine possessing Tn916, and one harbored tet(S) gene. PFGE analysis revealed genetic heterogeneity among individual serotypes as well as scattered occurrence of some genotypes without any clear-cut correlation to source or food type. The widespread distribution of epidemiologically important serotypes (1/2a, 1/2b and 4b) of L. monocytogenes, and their resistance to commonly used antibiotics indicate a potential public health risk. Our data also indicate that L. monocytogenes could act as a reservoir of mobile tet genes along the food chain.     

Danish initiatives to improve the safety of meat products

During the last two decades the major food safety problems in Denmark, as determined by the number of human patients, has been associated with bacterial infections stemming from meat products and eggs. The bacterial pathogens causing the majority of human infections has been Salmonella and Campylobacter, and to a lesser extent Yersinia, Escherichiacoli O157 and Listeria. Danish initiatives to improve the safety of meat products have focused on the entire production chain from the farm to the consumer, with a special emphasis on the pre-harvest stage of production. The control of bacterial pathogens which are resistant to antibiotics has been a new area of attention in the recent decade, and recently, the increasing globalization of the domestic food supply has called for a complete rethinking of the national food safety strategies. The implementations of a “case-by-case” risk assessment system, as well as increased international collaboration on surveillance, are both elements in this new strategy.     

Influence of cell surface hydrophobicity on attachment of Campylobacter to abiotic surfaces

This work aimed to investigate the influence of physicochemical properties and prior mode of growth (planktonic or sessile culture) on attachment of 13 Campylobacter jejuni strains and 5 Campylobacter coli strains isolated from chicken samples to three abiotic surfaces: stainless steel, glass and polyurethane. Water contact angle and zeta potential measurements indicated that the strains varied with respect to surface hydrophobicity (17.6 ± 1.5 to 53.0 ± 2.3°) and surface charge (−3.3 ± 0.4 to −15.1 ± 0.5 mV). Individual strains had different attachment abilities to stainless steel and glass (3.79 ± 0.16 to 5.45 ± 0.08 log cell cm⁻²) but did not attach to polyurethane, with one exception. Attachment of Campylobacter to abiotic surfaces significantly correlated with cell surface hydrophobicity (P ≤ 0.007), but not with surface charge (P ≥ 0.507). Cells grown as planktonic and sessile culture generally differed significantly from each other with respect to hydrophobicity and attachment (P < 0.05), but not with respect to surface charge (P > 0.05). Principal component analysis (PCA) clustered strains into three groups (planktonic culture) and two groups (sessile culture) representing those with similar hydrophobicity and attachment. Of the four highly hydrophobic and adherent strains, three were C. coli suggesting that isolates with greater hydrophobicity and adherence may occur more frequently among C. coli than C. jejuni strains although this requires further investigation using a larger number of strains. Assignment of pulsed-field gel electrophoresis profiles to PCA groups using Jackknife analysis revealed no overall relationship between bacterial genotypes and bacterial attachment. No relationship between serotype distribution and bacterial attachment was apparent in this study.     

Prevalence and survival of Campylobacter in Egyptian dairy products

Campylobacter is a leading foodborne pathogen that poses an interesting paradox of being frequently transmitted by foodstuffs, yet showing sensitivity to food preservation procedures. In the present study, 227 samples of milk and dairy products were randomly collected and examined for the presence of Campylobacter spp. Samples were collected from the Egyptian area Abou-Homos, where the pathogen had been previously shown to be a major causative agent of intestinal disease. Potential Campylobacter isolates were speciated using a multiplex PCR assay targeting the housekeeping gene lpxA. Only raw milk and fresh Domiati cheese samples were found to contain Campylobacter jejuni at low incidence rates. Using a selected C. jejuni isolate recovered in this study, it was shown that the pathogen maintained its viability in Domiati cheese more than in yoghurt, yet it survived in both products more than expected. This suggests that this foodborne strain of C. jejuni may develop adaptive strategies that aid survival under food preservation conditions, which contradicts with what is known about this pathogen as a stress-sensitive organism.     

An investigation of sources of Campylobacter in a poultry production and packing operation in Barbados

Chicken meat is frequently contaminated with Campylobacter jejuni and is thought to be the major source of organisms causing human Campylobacter enteritis. Genotypic similarities between Campylobacter isolates from chicken meat at retail outlets and patients with gastroenteritis in Barbados suggested that it is a vehicle for infection of humans on the island and prompted this investigation of transmission of Campylobacter in a local poultry operation. Campylobacter testing was conducted at the hatchery, on the broiler farm and in the processing plant for two consecutive production cycles. The genetic relatedness of Campylobacter isolates was determined by RAPD typing with primer OPA 11. Hatchery samples and week-old chicks were negative for Campylobacter. Flocks became colonized as early as three weeks after introduction to the farm. Ten distinct RAPD genotypes were identified among isolates. Some genotypes were similar and may be of clonal origin. There was no evidence of vertical transmission of Campylobacter. The results suggest that the broiler flock was infected from more than one source in the farm environment.     

Molecular subtyping and virulence gene analysis of Listeria monocytogenes isolates from food

A total of 67 Listeria monocytogenes isolates from 698 raw meat samples were characterized for molecular serogroup identification and antimicrobial susceptibility. Approximately one third (32.8%) of the isolates belonged to molecular serogroup 1/2a, 3a, followed by 1/2c, 3c (26.9%), 1/2b, 3b, 7 (22.4%), 4b, 4d, 4e (16.4%) and 4a, 4c (1.5%). Most of the L. monocytogenes isolates were susceptible to 14 antimicrobials tested but several were resistant to tetracycline, ciprofloxacin and nitrofurantoin. An additional 30 L. monocytogenes isolates from chicken and produce in our collection were also included to determine the presence of significant virulence markers. All 97 isolates carried inlC and inlJ except for a lineage III isolate 110-1. Most Listeriolysin S (LLS)-carrying isolates (11/12) belonged to lineage I, whereas the remaining one isolate belonged to lineage III. Five 4b, 4d, 4e isolates including two from turkey and three from produce belonged to Epidemic Clone I (ECI). Four molecular serogroup associated mutation types that lead to premature stop codons (PMSCs) in inlA were identified. PFGE and inlA sequence analysis results were concordant, and different virulence potential within 1/2a, 3a and 4b, 4d, 4e isolates were observed. The study revealed that a subset of isolates from meat and produce belonged to ECI, harbored inlC, inlJ and LLS, and produced full length InlA, suggesting that they be capable of causing human illness.     

Survival of Campylobacter jejuni on beef and pork under vacuum packaged and retail storage conditions: examination of the role of natural meat microflora on C. jejuni survival

The ability of Campylobacter jejuni ATCC 11168 to survive on beef and pork stored under chilled, vacuum packaged and retail display conditions were examined. In addition, the effect of natural microflora on commercial beef and pork on the survival of C. jejuni under these storage conditions was examined. When sterile cores of beef and pork were inoculated with ∼10⁵ to 10⁶ cfu cm⁻²C. jejuni, and were stored under aerobic or vacuum packaged conditions at −1.5 or 4 °C, its numbers dropped significantly and C. jejuni could not be enumerated by direct plating after 21 d of the 6 wks study. In contrast, survival of C. jejuni on commercial vacuum packaged beef and pork was significantly enhanced, resulting in only 1 log cfu cm⁻² reduction at the end of 6 wks. During 7 d of display in a retail case, numbers of C. jejuni dropped quickly, but could be enumerated by direct plating even after the 7 d. The presence of high numbers of inoculated C. jejuni on beef and pork had no significant effect on the natural microflora numbers compared to uninoculated controls when the meat was stored either in vacuum or in a retail display case. These results show that natural microflora on vacuum packaged meat afford enhanced survival of C. jejuni present on the surfaces of both beef and pork when stored at refrigeration temperatures. Hence, strict hygienic practices or the implementation of decontamination technologies are recommended to ensure safety of meat with respect to this pathogen.