Reduction of experimental Salmonella and Campylobacter contamination of chicken skin by application of lytic bacteriophages

Lytic bacteriophages, applied to chicken skin that had been experimentally contaminated with Salmonella enterica serovar Enteritidis or Campylobacter jejuni at a multiplicity of infection (MOI) of 1, increased in titer and reduced the pathogen numbers by less than 1 log(10) unit. Phages applied at a MOI of 100 to 1,000 rapidly reduced the recoverable bacterial numbers by up to 2 log(10) units over 48 h. When the level of Salmonella contamination was low (< log(10) 2 per unit area of skin) and the MOI was 10(5), no organisms were recovered. By increasing the number of phage particles applied (i.e., MOI of 10(7)), it was also possible to eliminate other Salmonella strains that showed high levels of resistance because of restriction but to which the phages were able to attach.

Development of a triplex PCR assay for the specific detection of Campylobacter jejuni, Salmonella spp., and Escherichia coli O157:H7

A triplex PCR assay was developed and evaluated for efficacy in detecting Campylobacter jejuni, Salmonella spp., and Escherichia coli O157:H7 in a variety of raw and ready-to-eat food products. Following a short enrichment period, artificially contaminated food samples were subjected to a triplex PCR assay, which incorporated published primers for each food pathogen, a protocol for sample collection, and a PCR procedure designed specifically for the assay. The selected primers amplified fragment sizes of 159 bp, 252 bp, and 360 bp for C. jejuni, E. coli O157:H7, and Salmonella spp., respectively. This assay provides specific and reliable results and allows for the cost-effective detection of all three bacterial pathogens in one reaction tube.

Rapid detection of Campylobacter jejuni in chicken rinse water by melting-peak analysis of amplicons in real-time polymerase chain reaction

Five DNA extraction protocols for the detection of Campylobacter spp. by polymerase chain reaction (PCR) were compared. A method involving Triton X-100 produced template DNA of sufficient quality to allow the detection of Campylobacter jejuni at levels of 100 CFU/ml in pure culture. Primers were designed on the basis of the cadF gene sequence. With a SYBR Green I real-time PCR assay, these primers amplified only sequences present in C. jejuni to produce a product with a melting temperature of 81.5 degrees C. None of the strains of Campylobacter coli, Campylobacter lari, or Campylobacter fetus tested produced this product during the PCR assay. Other noncampylobacter species tested were shown not to possess the cadF sequence. The real-time PCR combined with a rapid, simple Triton X-100 DNA extraction protocol made it possible to detect < 10 CFU of C. jejuni per ml of chicken rinse within 14 h.

Molecular typing of Campylobacter jejuni isolates involved in a neonatal outbreak indicates nosocomial transmission

Genotypic typing by restriction fragment length polymorphism and pulsed-field gel electrophoresis showed that two neonates in a neonatal ward were infected with the same Campylobacter jejuni strain. Isolates from the mother and brother of the index patient were identical to each other but distinct from the neonatal type. Genotyping results therefore suggested that the neonatal C. jejuni infection was nosocomial in origin.

A descriptive study of Guillain-Barré syndrome in high and low Campylobacter jejuni incidence regions of Michigan: 1992-1999

The incidence rate of Guillain-Barré syndrome (GBS) was compared between high and low Campylobacter jejuni incidence counties in Michigan, USA, between 1992 and 1999. Data on GBS was obtained from cases reported to the Michigan Department of Community Health. Poisson confidence intervals were used to compare incidence rates. There was no significant difference in the overall rate between high and low C. jejuni incidence regions in Michigan. Though no differences in age-specific, gender-specific, and seasonal rates were significant, GBS was more common in spring and summer in the high C. jejuni incidence region than in the low C. jejuni incidence region. Differences in the distribution of cases by age group and gender are described, though no difference was statistically significant.

Antimicrobial resistance of Campylobacter jejuni and Campylobacter coli isolates from broiler chickens isolated at an Irish poultry processing plant

AIMS

The antibiotic susceptibility of Campylobacter jejuni and Campylobacter coli isolates from broiler chickens were determined in order to evaluate the level of antibiotic resistance of Campylobacter species in the Irish poultry industry.

METHODS AND RESULTS

Seventy-eight Camp. jejuni and 22 Camp. coli strains were examined for susceptibility to eight antibiotics using the disc diffusion assay. The highest level of resistance of the Camp. jejuni isolates was recorded to ampicillin (35.9%), followed by 20.5% to tetracycline, 20.5% to naladixic acid, 17.9% to ciprofloxacin, 10.2% to erythromycin, 2.5% to streptomycin and 1.2% to kanamycin. Multidrug resistance to two or more antibiotics was seen for 30.7% of Camp. jejuni strains. Resistance of the Camp. coli isolates was shown to ampicillin (9%) and tetracycline (18.2%).

CONCLUSIONS

The majority of Camp. jejuni strains were susceptible to antibiotics commonly used for human therapy. Camp. coli strains showed very low resistance levels and were susceptible to six of the eight antimicrobial agents studied.

SIGNIFICANCE AND IMPACT OF THE STUDY

Levels of Camp. jejuni and Camp. coli antimicrobial resistance in Irish poultry production was assessed to determine the current situation in Ireland. The prevalence of antibiotic resistance of Campylobacter strains isolated from broiler chickens was low.

[Susceptibility of Campylobacter jejuni clinical isolates from children to eight antibiotics]

This study aimed to identify the activity of eight antibiotics (ofloxacin, moxifloxacin, azithromycin, erythromycin, clindamycin, ampicillin, amoxicillin-clavulanic acid and tetracycline) against 80 strains of Campylobacter jejuni isolated from children. Minimal inhibitory concentrations (MIC) were determined by an agar dilution method. Resistance to azithromycin and erythromycin was considered when MIC > or =8 mg/l, to clindamycin when MIC > or =1 mg/l, to amoxicillin-clavulanic acid and ampicillin when MIC > or =32 mg/l, to ofloxacin and moxifloxacin when MIC > or =4 mg/l, and to tetracycline when MIC > or =16 mg/l. All strains tested were susceptible to amoxicillin-clavulanic acid. The lowest frequency of resistance was to azithromycin (2%), erythromycin (3.7%), clindamycin (4.4%) and ampicillin (4.9%), and the highest was to ofloxacin and tetracycline (61.7% for both), and moxifloxacin (37%). Considered the antibiotics of choice for the treatment of infections caused by this microorganism, macrolides showed excellent activity with MIC(90)=0.5 mg/l for azithromycin and MIC(90)=0.5 mg/l for erythromycin.

Campylobacter jejuni isolated from poultry and humans in Styria, Austria: epidemiology and ciprofloxacin resistance

Sixty-six broiler flocks were sampled to determine the presence of Campylobacter spp. at slaughter in 1998. Thirty flocks (45%) tested positive and C. jejuni was identified in all isolates. Combined pulsed-field gel electrophoresis/amplified fragment length polymorphism (PFGE/AFLP) subtyping of 177 isolates from 24 positive flocks revealed 62 subtypes; 16 flocks harboured more than one subtype. When subtyping 101 clinical C. jejuni isolates collected in the same time period and area, 60 PFGE/AFLP types were identified. Comparison of subtypes from poultry and human isolates revealed three shared PFGE/AFLP types, which were present in 11 human isolates. Fifty per cent of all poultry isolates and 39% of all human isolates were resistant to ciprofloxacin. The present study confirms the increase in ciprofloxacin resistance in both human and poultry C. jejuni isolates in Austria, as observed in several countries worldwide. A small number of human isolates shared PFGE/AFLP types with poultry isolates, however, further studies should also focus on the identification of other sources of C. jejuni infection in humans.

Antimicrobial resistance of Campylobacter jejuni subsp. jejuni strains isolated from humans in 1998 to 2001 in Montréal, Canada

The rates of resistance of 51 to 72 human strains of Campylobacter jejuni subsp. jejuni isolated annually from 1998 to 2001 in Montréal, Québec, Canada, varied from 1 to 12% for erythromycin, 43 to 68% for tetracycline, and 10 to 47% for ciprofloxacin. In the last years of the study, there was a significant increase in the rate of resistance to ciprofloxacin (P = 0.00003) but not in the rate of resistance to erythromycin (P = 0.056) or tetracycline (P = 0.095) compared to the rate obtained in the first years. All 51 C. jejuni strains isolated in 2001 were susceptible to gentamicin, amoxicillin-clavulanic acid, imipenem, and meropenem. From 1999 to 2001, 74 strains of C. jejuni acquired abroad were significantly more resistant to ciprofloxacin than 109 strains of C. jejuni acquired locally (66 versus 9%, P < 0.00001) but were not significantly more resistant to erythromycin (1 versus 6%, P = 0.15) or to tetracycline (55 versus 58%, P = 0.87).

Rapid detection of Campylobacter coli, C. jejuni, and Salmonella enterica on poultry carcasses by using PCR-enzyme-linked immunosorbent assay

Contamination of retail poultry by Campylobacter spp. and Salmonella enterica is a significant source of human diarrheal disease. Isolation and identification of these microorganisms require a series of biochemical and serological tests. In this study, Campylobacter ceuE and Salmonella invA genes were used to design probes in PCR-enzyme-linked immunosorbent assay (ELISA), as an alternative to conventional bacteriological methodology, for the rapid detection of Campylobacter jejuni, Campylobacter coli, and S. enterica from poultry samples. With PCR-ELISA (40 cycles), the detection limits for Salmonella and Campylobacter were 2 x 10(2) and 4 x 10(1) CFU/ml, respectively. ELISA increased the sensitivity of the conventional PCR method by 100- to 1,000-fold. DNA was extracted from carcass rinses and tetrathionate enrichments and used in PCR-ELISA for the detection of Campylobacter and S. enterica, respectively. With PCR-ELISA, Salmonella was detected in 20 of 120 (17%) chicken carcass rinses examined, without the inclusion of an enrichment step. Significant correlation was observed between PCR-ELISA and cultural methods (kappa = 0.83; chi-square test, P < 0.001) with only one false negative (1.67%) and four false positives (6.67%) when PCR-ELISA was used to screen 60 tetrathionate enrichment cultures for Salmonella. With PCR-ELISA, we observed a positive correlation between the ELISA absorbance (optical density at 405 nm) and the campylobacter cell number in carcass rinse, as determined by standard culture methods. Overall, PCR-ELISA is a rapid and cost-effective approach for the detection and enumeration of Salmonella and Campylobacter bacteria on poultry.

Occurrence and resistance to antibiotics of Campylobacter jejuni and Campylobacter coli in animals and meat in northeastern Italy

A study was carried out in northeastern Italy during 2000 and 2001 to investigate the occurrence of Campylobacter jejuni and Campylobacter coli in animals, cattle, pigs, and broilers, and raw meat, beef, pork, and chicken. Campylobacter spp. were detected in 53.9% of the cattle, 63.5% of the pigs, and 82.9% of the broilers examined. Chicken meat was frequently contaminated (81.3%), while lower rates were found in pork meat (10.3%) and beef (1.3%). The resistance to antibiotics of the strains was also investigated, and compared to that of human clinical isolates. C. coli was generally more resistant than C. jejuni. Resistance to quinolones was frequently observed in C. coli isolated in chicken meat (78.6%); slightly lower rates were found in C. jejuni isolated in broilers (42.2%), chicken meat (52.8%), and humans (38.2%). C. coli was also frequently resistant to tetracycline in all sources, while resistance to streptomycin was most frequently observed in pig isolates (89.4%).

Quantitative, multiplexed detection of bacterial pathogens: DNA and protein applications of the Luminex LabMAP system

Escherichia coli, Salmonella, Listeria monocytogenes and Campylobacter jejuni are bacterial pathogens commonly implicated in foodborne illnesses. Generally used detection methods (i.e., culture, biochemical testing, ELISA and nucleic acid amplification) can be laborious, time-consuming and require multiple tests to detect all of the pathogens. Our objective was to develop rapid assays to simultaneously detect these four organisms through the presence of antigen or DNA using the Luminex LabMAP system. For nucleic acid detection, organism-specific capture probes corresponding to the 23S ribosomal RNA gene (rrl) were coupled covalently to LabMAP microspheres. Target molecules included synthetic complementary oligonucleotides and genomic DNA isolated from ATCC type strains or other well-characterized strains of each organism. Universal PCR primers were designed to amplify variable regions of bacterial 23S ribosomal DNA, yielding biotinylated amplicons of 86 to 109 bp in length. Varying quantities of targets were hybridized to the combined microsphere sets, labeled with streptavidin-R-phycoerythrin and analyzed on the Luminex(100) system. Results of nucleic acid detection assays, obtained in 30 to 40 min following amplification, correctly and specifically identified each bacterial species with a detection sensitivity of 10(3) to 10(5) genome copies. Capture-sandwich immunoassays were developed with organism-specific antibodies coupled to different microsphere sets. Microspheres were incubated with organism-specific standards and reactivity was assessed with biotinylated detection antibodies and streptavidin-R-phycoerythrin. In the immunoassays, microsphere-associated fluorescence was organism concentration dependent with detectable response at < or = 1000 organisms/ml and with no apparent cross-reactivity. We have demonstrated that the Luminex LabMAP system is a rapid, flexible platform capable of simultaneous, sensitive and specific detection of pathogens. The practical significance of this multiplexing approach would be to provide more timely, economical and comprehensive information than is available with conventional isolation and identification methodologies.

In vivo tracking of Campylobacter jejuni by using a novel recombinant expressing green fluorescent protein

Campylobacter jejuni is a leading cause of food-borne disease in developed countries. The goal of this study was to develop a plasmid-based reporter system with green fluorescent protein (GFP) to facilitate the study of C. jejuni in a variety of niches. C. jejuni transformants harboring the pMEK91 GFP gene (gfp)-containing vector were readily detectable by both fluorescence microscopy and flow cytometry. Given the ease of detecting these organisms, additional experiments were performed in which BALB/c mice were injected intraperitoneally with C. jejuni harboring the gfp-containing vector. Four hours after injection of the mice, flow cytometry analyses determined that C. jejuni synthesizing GFP were predominantly associated with granulocytes. More specifically, the proportion of CD11b(+) Gr-1(+) lavage neutrophils with green fluorescence ranged from 99.7 to 100%, while the proportion of CD11b(+) Gr-1(-) lavage macrophages ranged from 77.0 to 80.0%. In contrast, few CD11b(-) CD45R(+) B lymphocytes from the lavage of the C. jejuni-injected mice were associated with green-fluorescent C. jejuni (proportions ranged from 0.75 to 0.77%). Cell-free C. jejuni was recovered from tissue homogenates after intraperitoneal injection. Macrorestriction profiling with pulsed-field gel electrophoresis identified a genotypic variant of the C. jejuni F38011 wild-type isolate. In vivo this variant displayed a phenotype identical to that of the wild-type isolate. In summary, we demonstrate that C. jejuni associates with marker-defined cellular subsets in vivo with a novel gfp reporter system and that C. jejuni genotypic variants can be isolated from both in vitro and in vivo systems.

Antimicrobial-resistant Campylobacter species from retail raw meats

The antimicrobial susceptibilities of 378 Campylobacter isolates were determined. Resistance to tetracycline was the most common (82%), followed by resistance to doxycycline (77%), erythromycin (54%), nalidixic acid (41%), and ciprofloxacin (35%). Campylobacter coli displayed significantly higher rates of resistance to ciprofloxacin and erythromycin than Campylobacter jejuni, and Campylobacter isolates from turkey meat showed a greater resistance than those from chicken meat.

Campylobacter jejuni enteritis associated with consumption of raw milk

An outbreak of Campylobacter jejuni enteritis occurred among people who had attended a meal where raw milk was served. A case control study was conducted using instances of illness as cases; those who attended the event but did not become ill served as controls. Thirteen of 20 people who had attended the meal became ill. C. jejuni was cultured from five of six stools that were submitted. Raw milk consumption was strongly associated with illness (p = .0072, Fisher exact test). Although C. jejuni outbreaks associated with milk can be prevented with pasteurization, they still occur in association with raw milk consumption.

Colonisation phenotype and colonisation potential differences in Campylobacter jejuni strains in chickens before and after passage in vivo

Campylobacter jejuni strains isolated from chicken faeces and from humans suffering from gastroenteritis were used to determine the colonisation phenotypes and colonisation potential of these strains in chickens. Five different colonisation types were observed ranging from immediate and sustained colonisation to completely non-colonising. Phenotype one showed immediate colonisation with prolonged excretion of viable C. jejuni bacteria. Phenotype two showed delayed colonisation with prolonged excretion of viable C. jejuni bacteria. Phenotype three showed immediate colonisation and delayed clearing of viable C. jejuni bacteria. Phenotype four showed delayed colonisation and delayed clearing of viable C. jejuni bacteria. Strains of phenotype five could not colonise chickens. Inoculum levels to obtain maximum caecal colonisation for each phenotype for strains cultured in vitro and in vivo was also determined. Following passage in vivo through a chicken, the minimum inoculum required for sustained colonisation dropped approximately 1000-fold, however, the colonisation phenotype remained unchanged before and after a passage in vivo.

Prevalence of 11 pathogenic genes of Campylobacter jejuni by PCR in strains isolated from humans, poultry meat and broiler and bovine faeces

Although many genes related to the pathogenicity of Campylobacter jejuni have been reported, the relationships between these genes and the sources of strains are not clear. In this study, the presence of 11 pathogenic genes responsible for the expression of adherence, invasion, colonization and cytotoxin production was examined in 111 C. jejuni isolated from human clinical samples, poultry meat, broiler faeces and bovine faeces. For most of the pathogenic genes, no difference in their presence in C. jejuni was found among the sources, but, for racR, wlaN and virB11, there were some variations among sources. The racR gene was present at rates of 98.2 (human clinical samples), 90.5 (poultry meat), 85.7 (broiler faeces) and 76.7 % (bovine faeces). Detection rates for the wlaN gene were 25.0, 23.8, 4.7 and 7.7 % and those for the virB11 gene were 10.7, 9.5, 9.5 and 15.4 % in human clinical samples, poultry meat, broiler faeces and bovine faeces, respectively. One hundred and seven of 111 strains (96.4 %) carried from eight to 10 of the pathogenic genes. These data did not show remarkable differences in the presence of pathogenic genes carried by C. jejuni from various sources.

Reference isolates for the clonal complexes of Campylobacter jejuni

AIMS

To identify and make available through the National Collection of Type Cultures (NCTC) a set of reference isolates for the clonal complexes of Campylobacter jejuni.

METHODS AND RESULTS

The development of a multilocus sequence typing scheme for C. jejuni enabled the genetic characterization of a large number of isolates (n = 814) from cases of human disease, animals, birds and their food products. The nucleotide sequence data were used to assign each isolate an allelic profile or sequence type (ST) and examine the C. jejuni population structure in terms of clonal complexes. The clonal complexes consisted of an abundant central or founder genotype (ST), after which the complex was named, together with very closely related, generally less abundant genotypes differing from the founder at one, two or three loci. The clonal complex is an informative unit for the study C. jejuni epidemiology. It provides data which enabled the choice of 13 C. jejuni founder isolates for submission to the NCTC as a representative cross-section of the C. jejuni population.

CONCLUSIONS

These 13 isolates provide a defined resource for further research into aspects of C. jejuni biology such as genomic diversity, virulence and adaptation to particular hosts or environmental survival.

SIGNIFICANCE AND IMPACT OF STUDY

This isolate collection is available through the NCTC and provides a resource for further research.

Application of single-strand conformation polymorphism and denaturing gradient gel electrophoresis for fla sequence typing of Campylobacter jejuni

Campylobacter jejuni is a frequent cause of bacterial gastroenteritis in humans all over the world. Several molecular typing methods are used to study the epidemiology of Campylobacter spp. infections. The aim of the present study was to investigate the application of single-strand conformation polymorphism (SSCP) and denaturing gradient gel electrophoresis (DGGE) analysis as rapid primary subtyping methods for C. jejuni. A variable fragment from the 3' end of the flaA to the 3' end of the intergenic region, separating the flaA and flaB genes, was subjected to SSCP and DGGE analysis. A total of 48 clinical C. jejuni isolates, 49 C. jejuni strains isolated from poultry, 2 strains isolated from ducks and 1 strain isolated from a pheasant were assigned to 24 distinct SSCP patterns. Sequence analysis of the respective DNA fragments revealed that every different fla sequence type could be distinguished by SSCP. DGGE proved to be equally discriminatory. Both methods can be applied as primary subtyping methods, because pulsed-field gel electrophoresis (PFGE) and amplified fragment length polymorphism (AFLP) analysis further differentiated isolates belonging to the same fla sequence types.

A real-time PCR assay for the detection of Campylobacter jejuni in foods after enrichment culture

A real-time PCR assay was developed for the quantitative detection of Campylobacter jejuni in foods after enrichment culture. The specificity of the assay for C. jejuni was demonstrated with a diverse range of Campylobacter species, related organisms, and unrelated genera. The assay had a linear range of quantification over six orders of magnitude, and the limit of detection was approximately 12 genome equivalents. The assay was used to detect C. jejuni in both naturally and artificially contaminated food samples. Ninety-seven foods, including raw poultry meat, offal, raw shellfish, and milk samples, were enriched in blood-free Campylobacter enrichment broth at 37 degrees C for 24 h, followed by 42 degrees C for 24 h. Enrichment cultures were subcultured to Campylobacter charcoal-cefoperazone-deoxycholate blood-free selective agar, and presumptive Campylobacter isolates were identified with phenotypic methods. DNA was extracted from enrichment cultures with a rapid lysis method and used as the template in the real-time PCR assay. A total of 66 samples were positive for C. jejuni by either method, with 57 samples positive for C. jejuni by subculture to selective agar medium and 63 samples positive in the real-time PCR assay. The results of both methods were concordant for 84 of the samples. The total time taken for detection from enrichment broth samples was approximately 3 h for the real-time PCR assay, with the results being available immediately at the end of PCR cycling, compared to 48 h for subculture to selective agar. This assay significantly reduces the total time taken for the detection of C. jejuni in foods and is an important model for other food-borne pathogens.