Inhibition of phage-resistant bacterial pathogen re-growth with the combined use of bacteriophages and EDTA

The combined effects of ethylenediaminetetraacetic acid (EDTA) and bacteriophage (phage) treatment of foodborne pathogens were investigated. Although viable counts for Campylobacter jejuni decreased by 1.5 log after incubation for 8 h in the presence of phage PC10, re-growth was observed thereafter. The combination of phage PC10 and 1 mM EDTA significantly inhibited the re-growth of C. jejuni. The viable counts for C. jejuni decreased by 2.6 log (P < 0.05) compared with that of the initial count after 24 h. Moreover, EDTA at 0.67 or 1.3 mM, combined with the specific lytic phages, also effectively inhibited the re-growth of phage-resistant cells of Campylobacter coli, Salmonella enterica serovar Enteritidis, and Salmonella enterica serovar Typhimurium. In addition, the combined effects of lytic phages and EDTA were investigated on the viability of Campylobacter in BHI broth at low temperatures followed by the optimum growth temperature. The re-growth of C. coli was significantly inhibited by the coexistence of 1.3 mM EDTA, and the viable counts of surviving bacteria was about the same as the initial viable count after the incubation. This is the first study demonstrating the combined use of lytic phages and EDTA is effective in inhibiting the re-growth of phage-resistant bacteria in Gram-negative bacteria.

Importance of the producer on retail broiler meat product contamination with Campylobacter spp

BACKGROUND

Campylobacter spp. are a leading cause of human bacterial gastroenteritis worldwide, with poultry meat being considered the most important source of the infection. To obtain data on broiler meat contamination with Campylobacter spp. in Lithuania, the occurrence, counts and genotypes of these pathogens on raw broiler meat products from different producers were examined.

RESULTS

Out of 312 broiler meat product samples examined, 46.8% were contaminated with Campylobacter spp. Campylobacter jejuni was identified in 51.4% and Campylobacter coli in 37.7% of positive samples. Campylobacter jejuni was more frequently found in the warm period (April-October) and C. coli in the cold period (November-March) of the year (P < 0.05). The overall mean count of Campylobacter spp. was 3.55 and 3.50 log10 colony-forming units (CFU) on wings and drumsticks respectively. The occurrence and counts of Campylobacter spp. varied significantly between producers examined (P < 0.05). Analysis of flaA-RFLP genotyping revealed C. jejuni genotypes common to all producers as well as producer-specific genotypes.

CONCLUSION

Both the occurrence and counts of Campylobacter spp. on broiler meat products were producer-dependent, so this should be kept in mind when risk-based control measures at national level are applied.

Sensitive and rapid detection of Campylobacter jejuni and Campylobacter coli using loop-mediated isothermal amplification

Loop-mediated isothermal amplification (LAMP) is an established nucleic acid amplification method offering rapid, accurate, and cost-effective diagnosis of infectious diseases. From the beginning of DNA extraction to final detection of Campylobacter jejuni and Campylobacter coli, the assay requires less than 50 and 90 min from a colony on selective media, and human feces, respectively. For chicken meat samples, the assay requires approximately 24-48 h from the beginning of the enrichment culture to final detection. The sensitivity of the LAMP assay is tenfold higher than that of the equivalent PCR assay. LAMP amplification can be judged by both turbidimeter analysis and visual assessment with the unaided eye. The LAMP assay is a powerful tool for rapid, simple, and sensitive detection of C. jejuni and C. coli, which may facilitate the investigation of C. jejuni and C. coli contamination in chicken, as well as the early diagnosis of C. jejuni and C. coli infection in humans.

Comparison of agar dilution and E-test for antimicrobial susceptibility testing of Campylobacter coil isolates recovered from 80 Ontario swine farms

The primary aim of this study was to evaluate the level of agreement of the E-test for in vitro antimicrobial susceptibility testing of Campylobacter coli using the agar dilution technique, which is the approved method. A convenience sample of 80 Ontario swine farms was chosen for this study; each farm was visited from January to June 2004. A total of 233 isolates of C. coli were tested for susceptibility to 10 antimicrobials by agar dilution and the E-test. Performance of the tests was evaluated using 7 quality control strains: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, Campylobacter jejuni ATCC 33560, and Campylobacter coli ATCC 33559 for the E-test and E. coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and C. jejuni ATCC 33560 for the agar dilution test. Weighted Cohen's kappa and prevalence-adjusted bias-adjusted kappa (PABAK) tests were used for statistical analysis. The E-test and agar dilution test results had a strong agreement when resistance to streptomycin and tetracycline were evaluated (weighted kappa: 0.68 and 0.66, respectively). However, marked disagreement was detected when testing susceptibility to nalidixic acid and ampicillin (0.15 and 0.22, respectively). Almost perfect agreement was detected by PABAK when testing susceptibility to gentamicin (0.99). Agreement was found to be moderate for ciprofloxacin, azithromycin, clindamycin, erythromycin, and chloramphenicol. Although the level of agreement between the E-test and agar dilution depended on the antimicrobial being tested, the E-test always detected a lower proportion of resistant isolates compared to agar dilution.

Campylobacter succession in broiler chickens

The competitive ability of Campylobacter coli OR12 over C. jejuni OR1 has been examined in experimental broiler chickens following the observation that C. coli replaced an established C. jejuni intestinal colonisation within commercial chicken flocks reared outdoors [El-Shibiny, A., Connerton, P.L., Connerton, I.F., 2005. Enumeration and diversity of campylobacters and bacteriophages isolated during the rearing cycles of free-range and organic chickens. Appl. Environ. Microbiol. 71, 1259-1266]. Co-cultures of C. coli OR12 with C. jejuni OR1, revealed that the two species were able to grow together at similar growth rates in exponential growth phase but if the disparity of the inoculum ratios were >log(10)4 in favour of C. coli OR12, C. jejuni OR1 was observed to prematurely enter decline phase. Chickens were pre-colonised with C. jejuni OR1 at 21-days-old to examine succession in vivo. The birds were inoculated between 2 and 12 days later with C. coli OR12, to determine if the second isolate could efficiently colonise and compete with an established C. jejuni strain. C. coli OR12 were able to co-colonise before replacing C. jejuni OR1 as the dominant species when the birds were more than 27 days of age at the time of administration over a 4-day period. If these criteria were met C. coli OR12 became the dominant isolate otherwise co-colonisation occurred until they were met. C. coli OR12 was also found to displace three alternative C. jejuni strains from pre-colonised chickens challenged with C. coli OR12 at 30 days of age and tested at 40 days. These data raise the possibility of manipulating populations of Campylobacter colonising chickens through competition.

Development of macrolide-resistant Campylobacter in broilers administered subtherapeutic or therapeutic concentrations of tylosin

The use of antimicrobials in food animal production, particularly those commonly used to treat infections in humans, has become a source of debate in recent years. However, limited data are available regarding the development of resistance following the subtherapeutic or therapeutic administration of antimicrobials in animal production. The objective of this study was to evaluate the effect of the administration of therapeutic and subtherapeutic concentrations of tylosin on the erythromycin susceptibility of Campylobacter jejuni and Campylobacter coli isolated from the ceca of treated broilers. In three replicated studies, day-of-hatch chicks were exposed to macrolide-susceptible C. jejuni or C. coli. At 2 weeks of age, tylosin was administered at subtherapeutic (22 ppm, continuously in the diet) or therapeutic concentrations (529 ppm, in the drinking water for 5 days). Broilers were sacrificed weekly. Total and erythromycin-resistant Campylobacter spp. were enumerated from individual ceca plus cecal contents. Overall erythromycin resistance was observed at a higher frequency (P < 0.01) among C. coli isolates (70.8%) than among C. jejuni isolates (36.8%) following tylosin administration. Across Campylobacter species, erythromycin resistance was observed at a higher frequency (P < 0.001) when tylosin was administered at subtherapeutic (62.7%) than at therapeutic (11.4%) concentrations. Subtherapeutic administration resulted in the recovery of 83.3 and 56.1% erythromycin-resistant isolates compared with only 33.3 and 7.9% of the isolates expressing erythromycin resistance following the administration of therapeutic concentrations for C. coli and C. jejuni, respectively. Further studies are needed to determine the factors involved in the apparent difference in the acquisition of macrolide resistance in C. coli compared with C. jejuni.

Succession in the intestinal microbiota of preadolescent turkeys

In the present study, automated ribosomal intergenic spacer analysis (ARISA), library sequence analysis, real-time PCR detection of Bacteroides uniformis and Campylobacter coli and dot-blot hybridizations of Clostridiaceae were used to identify trends in microbial colonization of the ceca of male turkeys. Two separate trials were performed with six and five birds, respectively. ARISA community profiles identified a period of community transition at week 12 of age in both trials. A significant increase of Ca. coli was also detected at week 12 in one trial, suggesting a possible correlation between microbiota destabilization and pathogen prevalence. Libraries of ribosomal small subunit 16S genes representing weeks 9, 11, 12 and 14 of both trials were sequenced. Whereas fingerprint and sequence analyses indicated significant differences in the species composition between the two trials, in general sequence library and dot-blot analyses indicated that Clostridia-like species decreased in prevalence over time. While B. uniformis prevalence in the two trials rose from 7% and 0% of the library clones at week 9 to 84% and 79% at week 11, real-time PCR did not support these results, with only approximately twofold and sixfold increases in internal transcribed spacer copy numbers observed.

Detection of Campylobacter jejuni and Campylobacter coli in chicken meat samples by real-time nucleic acid sequence-based amplification with molecular beacons

A nucleic acid sequence-based amplification (NASBA) assay based on molecular beacons was used for real-time detection of Campylobacter jejuni and Campylobacter coli in samples of chicken meat. A set of specific primers and beacon probe were designed to target the 16S rRNA of both species. The real-time NASBA protocol including the RNA isolation was valid for both of the cell suspensions in buffered saline and the artificially contaminated chicken meat samples. The presence of rRNA could be correlated with cellular viability, following inactivation of the bacteria by heating, in inoculated chicken meat samples but not in RNase-free cell suspensions.

Dissemination of antimicrobial resistant strains of Campylobacter coli and Campylobacter jejuni among cattle in Washington State and California

The purpose of this study was to investigate the genetic similarity of Campylobacter jejuni and Campylobacter coli with similar antimicrobial resistance phenotypes, isolated from cattle on different farms and at different times, in order to evaluate the possible existence of disseminated antimicrobial resistant clones. PFGE after SmaI and KpnI restriction identified 23 and 16 distinct PFGE patterns among 29 C. jejuni and 66 C. coli isolates, respectively. In C. coli, 51 (77%) of the resistant isolates demonstrated one of the four indistinguishable PFGE patterns, whereas only 24% doxycycline resistant C. jejuni shared one of the two indistinguishable PFGE patterns. The genetic mechanisms of resistance were homogeneous within and between these clonal types. Genetically indistinguishable (clonal) groups of C. coli accounted for most Campylobacter sp. with multiple antimicrobial resistance observed in this study, consistent with a role for clonal dissemination in the epidemiology of resistance in this species.

Effect of direct culture versus selective enrichment on the isolation of thermophilic campylobacter from feces of mature cattle at harvest

Campylobacterjejuni and Campylobacter coli are leading bacterial causes of human gastroenteritis in the United States and other industrialized nations. These organisms frequently colonize avian hosts, including commercial poultry, but are also found in the gastrointestinal tract of other warm-blooded animals, including swine, sheep, and cattle. This study investigated the effect of direct culture versus selective enrichment on the isolation of thermophilic Campylobacter from the colon of 610 cattle. Fecal samples were taken from the colon of mature cattle (older than 30 months of age) immediately after slaughter in a commercial abattoir over a period of 17 months. Campylobacter was isolated from 23.4% of the animals. Most (93%) of the culture-confirmed Campylobacter isolates were C. jejuni, with the remaining 7% being C. coli. Additionally, of the 143 samples from which pure cultures of Campylobacter could be isolated, 72 (50.3%) were positive only with selective enrichment, 18 (12.6%) were positive only with direct plating, and 53 (37.1%) were positive by both methods. The data suggest that, even though selective enrichment was more effective than direct plating, both direct plating and selective enrichment protocols might need to be employed for optimal surveillance of C. jejuni in fecal material from cattle.

The importance of Campylobacter coli in human campylobacteriosis: prevalence and genetic characterization

The primary aim of this study was to detect and genotype Campylobacter coli strains from humans over a period of one year from November 2002 to October 2003. Campylobacter spp. were isolated from patients with symptoms of enteric infection. Amplified fragment length polymorphism (AFLP) analysis was used to identify the genetic diversity of C. coli strains by cluster analysis. A total of 18.6% of all Campylobacter isolates were identified as C. coli. These data show, that C. coli is indeed of importance to human campylobacter infections. Heterogeneous patterns were detectable among the human C. coli pool by AFLP analysis suggesting different sources of infection. A continuous seasonal shift of genotypes was detectable.

Antibiotic resistance of Campylobacter jejuni and Campylobacter coli isolated from hog, beef, and chicken carcass samples from provincially inspected abattoirs in Ontario

Campylobacterjejuni is one of the most common causes of bacterial foodborne infection in the United States, and there are reports of resistance of Campylobacter spp. to antimicrobial agents used for the treatment of gastroenteritis. The purpose of this study was to determine the antimicrobial resistance patterns of Campylobacter spp. isolated from hog, beef, and chicken carcasses from provincially inspected abattoirs in Ontario. The agar dilution method was performed to measure antimicrobial resistance of the isolates. Antimicrobial resistance of Campylobacter isolates from hogs (n = 401), beef (n = 21), and chicken (n = 435) to ampicillin, azithromycin, chloramphenicol, ciprofloxacin, clindamycin, erythromycin, gentamicin, nalidixic acid, streptomycin, and tetracycline was determined. Resistance of chicken, hog, and beef isolates was 14.3, 18.2, and 9.5% to ampicillin; 17.9, 67.3, and 38.1% to azithromycin; 0, 0.5, and 0% to chloramphenicol; 3.7, 1.2, and 0% to ciprofloxacin; 2.3, 46.6, and 4.8% to clindamycin; 6.7, 43.6, and 4.8% to erythromycin; 0.2, 0, and 0% to gentamicin; 5.1, 10.7, and 0% to nalidixic acid; 13.6, 57.4, and 4.8% to streptomycin; and 52.6, 44.1, 42.9% to tetracycline, respectively. The hog isolates had the greatest resistance to seven of the ten antimicrobials tested. Results of this study confirm the existence of antimicrobial resistance of Campylobacter to various antimicrobial agents,especially ciprofloxacin and erythromycin, commonly used for treatment of campylobacteriosis in humans.

Heat resistance and mechanism of heat inactivation in thermophilic campylobacters

The heat resistance of Campylobacter jejuni strains AR6 and L51 and the heat resistance of Campylobacter coli strains DR4 and L6 were measured over the temperature range from 50 to 60 degrees C by two methods. Isothermal measurements yielded D55 values in the range from 4.6 to 6.6 min and z values in the range from 5.5 to 6.3 degrees C. Dynamic measurements using differential scanning calorimetry (DSC) during heating at a rate of 10 degrees C/min yielded D55 values of 2.5 min and 3.4 min and z values of 6.3 degrees C and 6.5 degrees C for AR6 and DR4, respectively. Both dynamic and isothermal methods yielded mean D55 values that were substantially greater than those reported previously (0.75 to 0.95 min). DSC analysis of each strain during heating at a rate of 10 degrees C/min yielded a complex series of overlapping endothermic peaks, which were assigned to cell wall lipids, ribosomes, and DNA. Measurement of the decline in the numbers of CFU in calorimetric samples as they were heated showed that the maximum rate of cell death occurred at 56 to 57 degrees C, which is close to the value predicted mathematically from the isothermal measurements of D and z (61 degrees C). Both estimates were very close to the peak m1 values, 60 to 62 degrees C, which were tentatively identified with unfolding of the 30S ribosome subunit, showing that cell death in C. jejuni and C. coli coincided with unfolding of the most thermally labile regions of the ribosome. Other measurements indicated that several essential proteins, including the alpha and beta subunits of RNA polymerase, might also unfold at the same time and contribute to cell death.

Speciation of Campylobacter coli, C. jejuni, C. helveticus, C. lari, C. sputorum, and C. upsaliensis by matrix-assisted laser desorption ionization-time of flight mass spectrometry

Multiple strains of Campylobacter coli, C. jejuni, C. helveticus, C. lari, C. sputorum, and C. upsaliensis isolated from animal, clinical, or food samples have been analyzed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Whole bacterial cells were harvested from colonies or confluent growth on agar and transferred directly into solvent and then to a spot of dried 3-methoxy-4-hydroxycinnamic acid (matrix). Multiple ions in the 5,000- to 15,000-Da mass range were evident in spectra for each strain; one or two ions in the 9,500- to 11,000-Da range were consistently high intensity. "Species-identifying" biomarker ions (SIBIs) were evident from analyses of multiple reference strains for each of the six species, including the genome strains C. jejuni NCTC 11168 and C. jejuni RM1221. Strains grown on nine different combinations of media and atmospheres yielded SIBI masses within +/-5 Da with external instrument calibration. The highest-intensity C. jejuni SIBIs were cytosolic proteins, including GroES, HU/HCj, and RplL. Multiple intraspecies SIBIs, corresponding probably to nonsynonymous nucleotide polymorphisms, also provided some intraspecies strain differentiation. MALDI-TOF MS analysis of 75 additional Campylobacter strains isolated from humans, poultry, swine, dogs, and cats revealed (i) associations of SIBI type with source, (ii) strains previously speciated incorrectly, and (iii) "strains" composed of more than one species. MALDI-TOF MS provides an accurate, sensitive, and rapid method for identification of multiple Campylobacter species relevant to public health and food safety.

Discrimination of enterobacterial repetitive intergenic consensus PCR types of Campylobacter coli and Campylobacter jejuni by Fourier transform infrared spectroscopy

Fourier transform infrared spectroscopy (FT-IR) has been used together with pattern recognition methodology to study isolates belonging to the species Campylobacter coli and Campylobacter jejuni and to compare FT-IR typing schemes with established genomic profiles based on enterobacterial repetitive intergenic consensus PCR (ERIC-PCR). Seventeen isolates were cultivated under standardized conditions for 2, 3, and 4 days to study variability and improve reproducibility. ERIC-PCR profiles and FT-IR spectra were obtained from strains belonging to the species Campylobacter coli and C. jejuni, normalized, and explored by hierarchical clustering and stepwise discriminant analysis. Strains could be differentiated by using mainly the first-derivative FT-IR spectral range, 1,200 to 900 cm(-1) (described as the carbohydrate region). The reproducibility index varied depending on the ages of the cultures and on the spectral ranges investigated. Classification obtained by FT-IR spectroscopy provided valuable taxonomic information and was mostly in agreement with data from the genotypic method, ERIC-PCR. The classification functions obtained from the discriminant analysis allowed the identification of 98.72% of isolates from the validation set. FT-IR can serve as a valuable tool in the classification, identification, and typing of thermophilic Campylobacter isolates, and a number of types can be differentiated by means of FT-IR spectroscopy.

Factors affecting the pressure resistance of some Campylobacter species

AIMS

To compare pressure resistance between strains of Campylobacter jejuni, Campylobacter coli, Campylobacter lari and Campylobacter fetus, and to investigate the effect of suspending medium on pressure resistance of sensitive and more resistant strains.

METHODS AND RESULTS

Six strains of C. jejuni and four each of C. coli, C. lari and C. fetus were pressure treated for 10 min at 200 and 300 MPa. Individual strains varied widely in pressure resistance but there were no significant differences between the species C. jejuni, C. coli and C. lari. Campylobacter fetus was significantly more pressure sensitive than the other three species. The pressure resistance of C. jejuni cultures reached a maximum at 16-18 h on entry into stationary phase then declined to a minimum at 75 h before increasing once more. Milk was more baroprotective than water, broth or chicken slurry but did not prevent inactivation even of a resistant strain at 400 MPa.

CONCLUSIONS

Pressure resistance varies considerably between species of Campylobacter and among strains within a species, and survival after a pressure challenge will be markedly influenced by culture age and food matrix.

SIGNIFICANCE AND IMPACT OF THE STUDY

Despite the strain variation in pressure resistance and protective effects of food, Campylobacter sp. do not present a particular problem for pressure processing.

Strain persistence and fluctuation of multiple-antibiotic resistant Campylobacter coli colonizing turkeys over successive production cycles

The dynamics of colonization of turkeys by thermophilic campylobacters that are resistant to multiple antibiotics is poorly understood. In this study, we monitored cecal colonization of turkeys by Campylobacter over three successive production cycles at the same farm. Campylobacter isolated from the ceca was predominantly C. coli in all three flocks. Isolates with two distinct fla types that represented a single clonal group based on pulsed-field gel electrophoresis and that were resistant to multiple antibiotics (tetracycline, streptomycin, ampicillin, erythromycin, kanamycin, nalidixic acid, and ciprofloxacin) predominated throughout the three production cycles. The relative prevalence of each fla type, however, varied significantly from one flock to the next. The repeated isolation of these multiresistant C. coli from successive flocks likely reflected persistence of the organisms in currently unknown reservoirs in the production environment or, alternatively, repeated introduction events followed by establishment of these bacteria in each successive flock.

Macrolide resistance in Campylobacter jejuni and Campylobacter coli: molecular mechanism and stability of the resistance phenotype

A collection of 23 macrolide-resistant Campylobacter isolates from different geographic areas was investigated to determine the mechanism and stability of macrolide resistance. The isolates were identified as Campylobacter jejuni or Campylobacter coli based on the results of the hippurate biochemical test in addition to five PCR-based genotypic methods. Three point mutations at two positions within the peptidyl transferase region in domain V of the 23S rRNA gene were identified. About 78% of the resistant isolates exhibited an A-->G transition at Escherichia coli equivalent base 2059 of the 23S rRNA gene. The isolates possessing this mutation showed a wide range of erythromycin and clarithromycin MICs. Thus, this mutation may incur a greater probability of treatment failure in populations infected by resistant Campylobacter isolates. Another macrolide-associated mutation (A-->C transversion), at E. coli equivalent base 2058, was detected in about 13% of the isolates. An A-->G transition at a position cognate with E. coli 23S rRNA base 2058, which is homologous to the A2142G mutation commonly described in Helicobacter pylori, was also identified in one of the C. jejuni isolates examined. In the majority of C. jejuni isolates, the mutations in the 23S rRNA gene were homozygous except in two cases where the mutation was found in two of the three copies of the target gene. Natural transformation demonstrated the transfer of the macrolide resistance phenotype from a resistant Campylobacter isolate to a susceptible Campylobacter isolate. Growth rates of the resulting transformants containing A-2058-->C or A-2059-->G mutations were similar to that of the parental isolate. The erythromycin resistance of six of seven representative isolates was found to be stable after successive subculturing in the absence of erythromycin selection pressure regardless of the resistance level, the position of the mutation, or the number of the mutated copies of the target gene. One C. jejuni isolate showing an A-2058-->G mutation, however, reverted to erythromycin and clarithromycin susceptibility after 55 subcultures on erythromycin-free medium. Investigation of ribosomal proteins L4 and L22 by sequence analysis in five representative isolates of C. jejuni and C. coli demonstrated no significant macrolide resistance-associated alterations in either the L4 or the L22 protein that might explain either macrolide resistance or enhancement of the resistance level.

Prevalences and transmission routes of Campylobacter spp. strains within multiple pig farms

In this work, faecal samples were collected from 15 pig farms to determine the Campylobacter prevalences at different times during the rearing period and to visualize the exchange of strains among the pig population by genotyping specific isolates. All isolated strains were identified as C. coli. Whereas no Campylobacter were detectable in the faeces of piglets at the day of birth, the Campylobacter incidence rose within days to 32.8%. After transfer to the nursery unit the prevalence increased to 56.6%. Approximately two-thirds of the pigs remained C. coli shedders in the fattening unit. In contrast to most farms, one farm expressed a very low Campylobacter incidence during the whole rearing period. Amplified fragment length polymorphism (AFLP) analysis was performed on all C. coli isolates of one farm. Clonal strains were identified from the brood sows and their offsprings or neighbouring piglets. After moving to the nursery unit, new genotypes appeared in that pig group but the original C. coli strains largely remained within that group. C. coli genotypes, identified during the fattening period, replaced the previously isolated genotypes. Transportation to the abattoir had no significant influence on the shedding rate of C. coli. The detection rate before transportation was 79.1% and decreased slightly to 78.2% (n=330). Additionally, eleven of 1474 environmental samples from different sources of the pig farms were positive for C. coli. This study demonstrates the importance of pigs as a reservoir for C. coli. Maternal C. coli strains are the primary source of infection but non-related genotypes from different sources appear during the rearing period and these latter strains constitute largely the final C. coli flora.

In vitro inhibitory activity of Chinese leek extract against Campylobacter species

Three aqueous extracts of dietary materials of Chinese leek (leek flower stem, soft leek and green leek) and two other reference extracts of Allium plants were used to investigate the antibacterial effects against Campylobacter jejuni and Campylobacter coli. All the tested strains of Campylobacter species were isolated from chickens. The minimum concentration of aqueous leek extracts (ALEs) required to inhibit the bacterial growth was 2.0 mg/ml. Among the plant extracts tested, ALEs shared the lowest value of minimum inhibitory concentration (MIC), and soft leek significantly demonstrated the strongest inhibitory activities (P < 0.05). All the Allium plants tested shared similar characteristics of heat and pH susceptibility. Heat treatment (>75 degrees C) of the extracts reduced the inhibitory activity. The boiled ALEs revealed significant loss of inhibition (P < 0.05), but they retained some inhibitory effect. The antibacterial activities of the ALEs were stable between pH 2.0 and 8.0, while the effects were significantly decreased (P < 0.05) when pH of the ALEs were adjusted to 1.0 or 9.0 above. The results indicated that the antibacterial activities of the ALEs against Campylobacter species were more effective than that of aqueous garlic extract.

Effects of Aeration and Storage Temperature on Campylobacter Concentrations in Poultry Semen

Campylobacter is one of the most commonly reported bacterial causes of human foodborne infections in the United States. Recent evidence has demonstrated that Campylobacter is present in poultry semen and may contribute to the vertical transmission between the breeder hen and offspring. As Campylobacter is considered sensitive to oxygen and cold temperature, the objective of this study was to determine if aeration and storage temperature could reduce or eliminate Campylobacter in poultry semen. In 4 separate trials, pooled semen samples were collected from roosters or toms, diluted with a commercial poultry semen extender, and inoculated with an average of 10(7) cells/mL of a wild-type C. jejuni or C. coli semen isolate. Pooled ejaculates were then divided into 3 aeration treatments: Control (no aeration), air, or oxygen (gently bubbled for 20 min with atmospheric air or oxygen, respectively). Immediately after aeration, pooled semen samples were further divided to 3 test storage temperatures: 4, 23, or 42 degrees C. At 0, 2, 6, and 24 h of storage, samples were enumerated for Campylobacter. Aeration of the semen alone, or aeration with reduced temperatures (4 or 23 degrees C), did not reduce the amount of Campylobacter compared with the controls. Campylobacter concentrations were, however, reduced when stored at 42 degrees C for 24 h. This effect is associated with reduced sperm viability and is therefore not a practical treatment of reducing Campylobacter in semen. It appears alternative methods will be needed to eliminate Campylobacter from poultry semen.

Prevalence and antimicrobial resistance of Campylobacter coli isolated from fattening pigs in France

Campylobacter are a leading cause of human diarrhea. The usual source of infection is contaminated food, particularly poultry but pork has also been described. The veterinary use of antimicrobial drugs has been suggested to be largely responsible for resistance in human isolates of this zoonotic pathogen. A study was carried out to investigate the occurrence and antimicrobial resistance of Campylobacter isolated from French fattening pigs. From March 1998 to June 1999, stomach samples were collected at slaughter from 240 fattening pigs originating from 24 different farms. Half of the pigs were found to be positive for Campylobacter but considerable variation was observed between farms. Isolates all belong to the Campylobacter coli species. Susceptibilities of the strains were determined for five antimicrobial drugs using agar dilution. Resistance to tetracycline and erythromycin was high (79 and 55%, respectively). For nalidixic acid, enrofloxacin and ampicillin, resistance was observed in 34, 15 and 20% of the isolates, respectively. More than one-third of the strains was resistant to at least three antimicrobial drugs. A Thr86Ile modification in GyrA was observed in the enrofloxacin-resistant strains studied. The multiresistant strains analyzed expressed the multidrug transporter CmeB at a high level. Results indicated a high prevalence of C. coli in the stomach of the French pigs examined. In addition, a high proportion of the strains was resistant to antimicrobial drugs, particularly to tetracycline and erythromycin, or were multiresistant.

Antagonistic activities of several bacteria on in vitro growth of 10 strains of Campylobacter jejuni/coli

Chicken meat contaminated with Campylobacter jejuni can be the source of human enteritis. To decrease the risk of human infection, Campylobacter should be controlled at farm levels. Orally given probiotic bacteria could prevent colonisation of chicken with pathogenic bacteria like Campylobacter. The aim of this study was to investigate the effect of different bacteria on Campylobacter growth. Our results demonstrated that bacteria isolated from conventional chicken had potential inhibitory activities against Campylobacter. Other bacteria not isolated from chickens but with known antagonistic capacities, e.g. Enterococcus (56 strains) and Escherichia coli (20 strains), did not show any negative effect on Campylobacter. Interestingly, one Lactobacillus (P93) strain isolated from the chicken gut showed bactericidal activity against all tested Campylobacter. The bactericidal effect was characterised as the production of organic acids in combination with probably production of an anti-Campylobacter protein. In a co-culture study of Campylobacter and Lactobacillus (P93), the culturability of Campylobacter was under the detection limit after 48 h of incubation. A chicken experiment is needed to further evaluate the effect of the promising probiotic bacteria against Campylobacter colonisation in chicken.

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.

Detection and enumeration of Campylobacter jejuni and Campylobacter coli by indirect impedimetry with an oxygen scavenging system

Six strains of Campylobacter jejuni and Campylobacter coli were shown to grow in a variety of media, but, with one exception, they were unable to produce sufficient change in the electrical properties of the medium to allow their detection by impedance monitoring. With the use of an indirect method based on absorption of evolved carbon dioxide and a medium containing the oxygen scavenger Oxyrase, all strains were detectable, and correlations between time to detection and the logarithm of the inoculum level were excellent. The level of interstrain variation was sufficiently low that all data could be consolidated into a single calibration curve (r = 0.987).

Reduction of bacteria on pork carcasses associated with chilling method

In addition to reducing the temperature of pork carcasses immediately after slaughter and before fabrication, blast chilling (snap chill) or conventional chilling can reduce bacterial populations associated with fresh meats. However, there is little information on bacteria survival resulting from the freeze or chill injury of meat products. In this study, porcine fecal slurries with and without pathogens (Listeria monocytogenes, Salmonella Typhimurium, and Campylobacter coli) were inoculated onto skin-on and skin-off pork surfaces and subjected to industry-specific blast or conventional chilling conditions. A thin agar layer method was used for the recovery of freeze- or chill-injured cells. Test results indicated that there were no statistically significant (P > 0.05) differences between blast and conventional chilling treatments with respect to the reduction of high and low inoculation levels of mesophilic aerobic bacteria, total coliforms, or Escherichia coli on either skin-on or skin-off surfaces. Chilling treatments did not differ significantly (P > 0.05) with respect to their ability to reduce low (3 log10 CFU/cm2) levels of L. monocytogenes and Salmonella Typhimurium. However, C. coli was reduced to undetectable levels, even after enrichment, on pork surfaces inoculated with low levels (3 log10 CFU/cm2) and subjected to blast chilling. Blast and conventional chilling treatments were more effective against all pathogenic bacterial populations when pork surfaces where inoculated at high levels (5 log10 CFU/cm2). The effects of chilling techniques on microbial populations could provide pork processors with an additional intervention for pork slaughter or information to modify and/or improve the chilling process. The information obtained from this study has the potential to serve as a means of producing a microbiologically safer product.

Comparison of recovery methods for freeze-injured Listeria monocytogenes, Salmonella Typhimurium, and Campylobacter coli in cell suspensions and associated with pork surfaces

Cells injured as a result of freezing, heating, and acidification treatments may not grow during conventional microbiological procedures owing to the presence of selective agents, compounds, or dyes in the media, impairing the cell's ability to repair itself and grow. Injured cells can be recovered by combining selective and nonselective media into a single system. With such combinations, the diffusion of the selective compounds or dyes is controlled, allowing for the resuscitation of injured cells of interest while also inhibiting the growth of undesirable background microflora. In this study, Listeria monocytogenes, Salmonella Typhimurium, and Campylobacter coli suspended in buffer or associated with pork surfaces were subjected to a freeze-thaw cycle (-15 degrees C for 24 h, 4 degrees C for 4 h). Following treatments, freeze-injured cells were plated on appropriate media for the overlay (OV), thin agar layer (TAL), and Lutri plate (LP) recovery methods. The levels of L. monocytogenes and Salmonella Typhimurium recovered from cell suspensions and pork surfaces by the TAL, OV, and LP methods following freeze treatments were not statistically different (P > 0.05) from recovery levels associated with nonselective media. Conversely, levels of pathogens on selective media were significantly reduced compared with those for the other methods employed. The TAL method's recovery of C. coli was not significantly different from that achieved with the nonselective media. Overall, the results presented in this study demonstrate that the TAL method not only was easier to perform, but also allowed improved isolation of single colonies for further characterization. This study may provide researchers with better methods to determine the effectiveness of industry-employed chilling processes in reducing pathogenic bacteria associated with red meat surfaces.

Survival and resuscitation of ten strains of Campylobacter jejuni and Campylobacter coli under acid conditions

The culturability of 10 strains of Campylobacter jejuni and Campylobacter coli was studied after the bacteria were exposed to acid conditions for various periods of time. Campylobacter cells could not survive 2 h under acid conditions (formic acid at pH 4). The 10 Campylobacter strains could not be recovered, even when enrichment media were used. Viable cells, however, could be detected by a double-staining (5-cyano-2,3-ditolyl tetrazolium chloride [CTC]-4',6'-diamidino-2-phenylindole [DAPI]) technique, demonstrating that the treated bacteria changed into a viable but nonculturable (VBNC) form; the number of VBNC forms decreased over time. Moreover, some VBNC forms of Campylobacter could be successfully resuscitated in specific-free-pathogen fertilized eggs via two routes, amniotic and yolk sac injecting.

Impediometric detection of Campylobacter coli

The rapid automated bacterial impedance technique (RABIT) was examined as a method for the detection of two wild-type isolates of Campylobacter coli in broth media. Both isolates failed to produce a change in impedance that was sufficient for detection in any combination of six nonselective basal broth media, including Mueller-Hinton broth, nutrient broth no. 2, brain heart infusion broth supplemented with yeast extract (0.5% [wt/vol]), brucella broth, Campy broth supplemented with yeast extract (0.5% [wt/voll), and Whitley impedance broth, at 37 and 42 degrees C. Although the strains did proliferate in the media, changes in conductivity were very small (ranging from 0 to 1,000 microS) and were not significantly greater than the drift in conductance observed in the control broth medium. Additional work is therefore required to define a nonionic growth substrate that will produce charged ions upon metabolism that are detectable by RABIT.

Double-staining method for differentiation of morphological changes and membrane integrity of Campylobacter coli cells

We developed a double-staining procedure involving NanoOrange dye (Molecular Probes, Eugene, Oreg.) and membrane integrity stains (LIVE/DEAD BacLight kit; Molecular Probes) to show the morphological and membrane integrity changes of Campylobacter coli cells during growth. The conversion from a spiral to a coccoid morphology via intermediary forms and the membrane integrity changes of the C. coli cells can be detected with the double-staining procedure. Our data indicate that young or actively growing cells are mainly spiral shaped (green-stained cells), but older cells undergo a degenerative change to coccoid forms (red-stained cells). Club-shaped transition cell forms were observed with NanoOrange stain. Chlorinated drinking water affected the viability but not the morphology of C. coli cells.

In vitro study on the effect of organic acids on Campylobacter jejuni/coli populations in mixtures of water and feed

Gastroenteritis caused by Campylobacter spp. infection has been recognized as one of the important public health problems in the developed countries. Outbreaks mostly originate from the consumption of contaminated poultry or infected water. The aim of this study was to determine the bactericidal activity on Campylobacter spp. of organic acids individually and in combinations at different pH levels and times and to compare bactericidal activities with activities of commercially available products. Ten strains of Campylobacter spp. were added in a mixture of water with commercial broiler feed, separately adjusted by four acids: formic, acetic, propionic, and hydrochloric acids, into pH 4.0, 4.5, 5.0, and 5.5. A combination of three organic acids was used in two different formulation ratios: formic:acetic:propionic at 1:2:3 and 1:2:5, at pH 4.0, 4.5, 5.0, and 5.5. All organic acids showed the strongest bactericidal effect on Campylobacter at pH 4.0. In contrast, at pH 5.0 and 5.5, the bactericidal activity of the four acids was low. The combination of organic acids showed a synergistic bactericidal activity at pH 4.5. Interestingly, the effect of the combined organic acids was stronger than the commercial products. Morphological cell changes were studied by transmission electron microscopy to determine the effect of the organic acids on the cell structure of Campylobacter. Some loss of outer membranes of the bacteria could be found in treated groups. Therefore, it can be concluded that organic acids, individually or in combination, have a strong bactericidal effect on Campylobacter spp. Routine application of organic acids to the water supply on poultry farms could prevent or diminish Campylobacter transmission.

Cecal colonization of chicks by porcine strains of Campylobacter coli

Ten genotypically distinct strains of Campylobacter coli were isolated from a swine production facility. These porcine isolates were then orally inoculated into day-of-hatch leghorn chicks and were excellent colonizers of the chick cecum. Campylobacter coli recovered from inoculated chickens were genotypically identical to the challenge strain. The absence of host specificity suggests a possible movement of strains among swine, field animals and birds, and poultry houses.

[Antagonistic activity of Lactobacillus bacteria strains against anaerobic gastrointestinal tract pathogens (Helicobacter pylori, Campylobacter coli, Campylobacter jejuni, Clostridium difficile)]

Antagonistic activity of Lactobacillus strains has been known for some time. This property is connected with production of many active substances by lactobacilli e.g., organic acids and bacteriocin-like substances which interfere with other indigenous microorganisms inhabiting the same ecological niche, including also anaerobic gastrointestinal tract pathogens. Growing interest of clinical medicine in finding new approaches to treatment and prevention of common inflammatory infections of the digestive tract resulted in studies on a possible usage of lactic acid bacteria. Last years, several in vitro and in vivo experiments on antagonism of different Lactobacillus strains against Helicobacter pylori and Clostridium difficile were performed. These observations had been done on already established, well known probiotic Lactobacillus strains. We tested antibacterial activities of Lactobacillus strains isolated from human digestive tract. As indicator bacteria, four species known as anaerobic bacterial etiologic agents of gastroenteric infections: Helicobacter pylori, Campylobacter jejuni, C. coli and Clostridium difficile were used. Some of them were obtained from international collections, others were clinical isolates from specimens taken from patients with different defined gastrointestinal infections. We used a slab method of testing inhibitory activity described in details previously. Following conclusions were drawn from our study: All tested human Lactobacillus strains were able to inhibit the growth of all strains of anaerobic human gastrointestinal pathogens used in this study. Inhibitory activities of tested Lactobacillus strains against Helicobacter pylori, Campylobacter spp., and Clostridium difficile as measured by comparing mean diameters of the inhibition zones were similar. Differences in susceptibility of individual indicator strains of Campylobacter spp. and Clostridium difficile to inhibitory activity of Lactobacillus strains were small. A similar mechanism of inhibition of anaerobic bacteria by lactobacilli is postulated.

Antimicrobial susceptibilities of Campylobacter strains isolated from broilers in the southern part of Japan from 1995 to 1999

Cecal contents (16 samples/each flock) of broilers derived from 212 flocks were investigated for colonization of Campylobacter from 1995 to 1999 in the southern part of Japan, and the isolates were tested for antimicrobial susceptibilities. C. jejuni-positive flocks numbered 42 (19.8%) and C. coli-positive ones 26 (12.3%); Campylobacter spp. were recovered from 68 flocks (32.1%) in total. MICs of ampicillin, erythromycin (EM), tetracycline, nalidixic acid (NA), norfloxacin (NFLX), and ofloxacin (OFLX) to these 68 Campylobacter isolates were determined. Quinolone-resistant Campylobacter isolates numbered 22 (32.4%). All the isolates except one were cross-resistant to NA, OFLX, and NFLX. A high frequency of quinolone-resistance was found in both C. jejuni and C. coli, whereas a high level of EM-resistance was found in only C. coli strains. All C. jejuni isolates were sensitive to EM.

Trichuris suis: detection of antibacterial activity in excretory-secretory products from adults

Antibacterial activity was detected in excretory-secretory products (ESP) of adult Trichuris suis cultured in vitro in serum-free media. Gram-negative bacteria (Campylobacter jejuni, Campylobacter coli, and Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus) were sensitive to ESP. Susceptibility was dependent on the concentration of ESP but not on the inoculum size. Preliminary assessment of the mode of action suggests a bacteriocidal mechanism. This antibacterial activity was heat stable and resistant to digestion with pronase E and trypsin. Based on ultrafiltration experiments, the activity is less than 10,000 MW. This excreted/secreted antibacterial activity from T. suis is likely a component of a humoral defense system for this helminth.

Survival of Campylobacter jejuni during stationary phase: evidence for the absence of a phenotypic stationary-phase response

When Campylobacter jejuni NCTC 11351 was grown microaerobically in rich medium at 39 degrees C, entry into stationary phase was followed by a rapid decline in viable numbers to leave a residual population of 1% of the maximum number or less. Loss of viability was preceded by sublethal injury, which was seen as a loss of the ability to grow on media containing 0.1% sodium deoxycholate or 1% sodium chloride. Resistance of cells to mild heat stress (50 degrees C) or aeration was greatest in exponential phase and declined during early stationary phase. These results show that C. jejuni does not mount the normal phenotypic stationary-phase response which results in enhanced stress resistance. This conclusion is consistent with the absence of rpoS homologues in the recently reported genome sequence of this species and their probable absence from strain NCTC 11351. During prolonged incubation of C. jejuni NCTC 11351 in stationary phase, an unusual pattern of decreasing and increasing heat resistance was observed that coincided with fluctuations in the viable count. During stationary phase of Campylobacter coli UA585, nonmotile variants and those with impaired ability to form coccoid cells were isolated at high frequency. Taken together, these observations suggest that stationary-phase cultures of campylobacters are dynamic populations and that this may be a strategy to promote survival in at least some strains. Investigation of two spontaneously arising variants (NM3 and SC4) of C. coli UA585 showed that a reduced ability to form coccoid cells did not affect survival under nongrowth conditions.

The effects of UVB and temperature on the survival of natural populations and pure cultures of Campylobacter jejuni, Camp. coli, Camp. lari and urease-positive thermophilic campylobacters (UPTC) in surface waters

AIMS

To determine whether diurnal and seasonal variations in campylobacters in surface waters result from the effects of temperature and u.v. radiation, and whether natural populations of Campylobacter lari and urease-positive thermophilic campylobacters (UPTC) from birds survive better in surface waters than Camp. jejuni from sewage.

METHODS AND RESULTS

Natural populations of Camp. lari and UPTC in sea water, and Camp. jejuni in river water, were exposed to artificial sunlight (equivalent to a sunny day in June). Both populations became non-culturable within 30 min, with T90s of 15 min and 25 min, respectively. Cultures of Camp. jejuni became non-culturable within 40 min and those of Camp. coli, Camp. lari and UPTC, within 60 min. In darkness, survival was temperature-dependent. Natural populations took 12 h at 37 degrees C and 5 days at 4 degrees C to become non-culturable in sea water, and slightly less in river water. Cultures of Camp. lari and UPTCs survived for significantly longer than Camp. jejuni and Camp. coli. Loss of culturability for all isolates was most rapid at 37 degrees C and slowest at 4 degrees C. Newly isolated strains from sea water and river water behaved in an almost identical manner to NCTC strains.

CONCLUSION

Campylobacter lari and UPTCs survive for longer in surface waters than Camp. jejuni and Camp. coli, particularly in the dark. Low Campylobacter numbers in coastal waters in the summer, especially in the afternoon, are due to the combined effects of higher temperatures and higher levels of u.v. radiation.

SIGNIFICANCE AND IMPACT OF THE STUDY

Campylobacter lari and UPTCs from birds predominate in bathing waters in Morecambe Bay because they are better able to survive; they also originate from closer to the shore than Camp. jejuni and Camp. coli in sewage effluent, which survive poorly and die before the incoming tide reaches the shore. The predominance of Camp. jejuni in river water results from its dominance of the inputs and not from its ability to survive.

Genetic diversity of the Campylobacter genes coding immunodominant proteins

Three Campylobacter jejuni 72Dz/92 genes (cjaA (ompH1), cjaC (hisJ) and cjaD (omp18)) encoding immunodominant proteins are considered to be potential chicken vaccine candidates. The presence and conservation of cjaA, cjaC and cjaD genes among different Campylobacter clinical isolates were determined. The genes were detected in thirty Campylobacter strains using hybridization as well as Western blot analysis. However, PCR products of the predicted size were amplified only from ten out of thirty examined strains regardless of the employed primer pair. The nucleotide sequence of the C. jejuni 72Dz/92 genes was compared with the nucleotide sequences of their homologs cloned from other Campylobacter strains as well as with the whole genome sequence of C. jejuni NCTC 11168. The examined sequences revealed 0 to 16% divergence. Strain-dependent levels of divergence were observed. The polymorphism detected in cjaC was mainly within the 5' region of the gene, while the nucleotide substitutions in cjaA and cjaD are distributed uniformly along the whole genes. Most of the observed nucleotide substitutions occurred at the third base of the codons. This observation is consistent with the results of Western blot experiments.

Development of a m-PCR assay for simultaneous identification of Campylobacter jejuni and C. coli

Multiplex PCR assay (m-PCR) with three sets of primers was developed for simultaneous identification of Campylobacter jejuni and C. coli. Poultry faecal samples were enriched in Preston broth for 24 h and streaking on selective media was performed before and after enrichment. m-PCR was applied on bacterial cultures harvested from media plates. The data showed a selective effect of Preston broth which favoured the growth of C. coli. Identification of the species by the hippurate hydrolysis test and by the m-PCR was performed on 294 isolates of Campylobacter. The efficiency of the identification by the biochemical test is only 34% in comparison to 100% efficiency with the PCR. The use of our m-PCR in combination with the culture method allowed reliable detection and identification of C. jejuni and C. coli within 3-4 d.

[A nutrient medium for the isolation and cultivation of Campylobacter]

Campylobacter agar, nutrient medium intended for the isolation of bacteria of the genus Campylobacter from clinical material, has been developed. The composition of the medium includes sprat hydrolysate, aerotolerant additive (ferric sulfate--oxide, sodium pyruvate, sodium pyrosulfite), sodium glutaminate, agar. The selective properties of the medium are ensured by introducing the mixture of antibiotics consisting of polymyxin B, rifampicin, amphotericin B, ristomycin. The balanced composition of Campylobacter agar ensures the aerotolerance of Campylobacter organisms and gives the optimal conditions for their growth when the inoculated material is cultivated in the atmosphere made up of the mixture of three gases (5% of oxygen, 10% of carbon dioxide, 85% of nitrogen), as well as under the conditions of a "candle vessel". The medium suppresses the development of the associative microflora diluted 10(-1). As shown in the trial of the quality of Campylobacter agar by the inoculation of material taken from patients with acute enteric infections, agricultural animals and monkeys, the medium has pronounced selective, properties with regard to extraneous microflora, while ensuring the isolation of Campylobacter on the level of the control medium.

Comparative value of colonic biopsy and intraluminal fluid culture for diagnosis of bacterial acute colitis in immunocompetent patients. Infectious Colitis Study Group

We compared the yield of intraluminal fluid culture to that of biopsy specimens obtained during colonoscopy for the diagnosis of bacterial colitis in 93 immunocompetent patients with a recent episode of diarrhea and macroscopic lesions of colitis. Stool culture findings were also available for 68 patients. At least one bacterial pathogen was isolated from the biopsy specimen, intraluminal fluid, or stool from 48 patients (51.6%). Salmonella species, Clostridium difficile, Klebsiella oxytoca, Shigella species, and Campylobacter species were recovered from 16 (17.2%), 15 (16.1%), 8 (8.6%), 7 (7.5%), and 4 (4.3%) of the patients, respectively. One Shigella species and one K. oxytoca strain were isolated from biopsy specimens but not from intraluminal fluid, and intraluminal fluid was the only positive specimen in 12 cases (yielding 1 Salmonella species, 2 Shigella species, 2 K. oxytoca, and 7 C. difficile isolates). In nine cases out of 10, toxin B was detected only in intraluminal fluid. A correlation of 91.2% was observed between stool and intraluminal fluid cultures for Salmonella, Shigella, and Campylobacter species isolations. Culture of biopsy specimens adds little to the diagnosis of infectious colitis, and stools and intraluminal fluids appear to have comparable value.

Generation of a superoxide dismutase (SOD)-deficient mutant of Campylobacter coli: evidence for the significance of SOD in Campylobacter survival and colonization

The microaerophilic nature of Campylobacter species implies an inherent sensitivity towards oxygen and its reduction products, particularly the superoxide anion. The deleterious effects of exposure to superoxide radicals are counteracted by the activity of superoxide dismutase (SOD). We have shown previously that Campylobacter coli possesses an iron cofactored SOD. The sodB gene of C. coli UA585 was insertionally inactivated by the site-specific insertion of a tetO cassette. Organisms harboring the inactivated gene failed to produce a biologically functional form of the enzyme. While the ability of this mutant to grow in aerobic conditions was unchanged relative to the parental strain, its survival was severely compromised when nongrowing cells were exposed to air. Accordingly, the SOD-deficient mutant was unable to survive for prolonged periods in model foods. Furthermore, inactivation of the sodB gene decreased the colonization potential in an experimental infection of 1-day-old chicks. In contrast, strain CK100, which is deficient in catalase activity, showed the same survival and colonization characteristics as the parental strain. These results indicate that SOD, but not catalase, is an important determinant in the ability of C. coli to survive aerobically and for optimal colonization within the chicken gut.

Study of the presence of Campylobacter jejuni and C. coli in sand samples from four Swiss chicken farms

Chicken farms are frequently infected with Campylobacter jejuni and Campylobacter coli. The objective of the present study was to investigate environmental samples from chicken farms for the presence of C. jejuni and C. coli. Every week between July and November 1997, three sand samples from the runs of four chicken farms were analyzed by culture and directly by polymerase chain reaction (PCR). These two detection methods were compared to each other. A total of 231 samples were tested. Eleven samples (4%) were found to contain Campylobacter cells by culture, whereas 157 samples (68%) were positive by PCR. All samples which were positive by culture were also positive by PCR. All direct PCR products were further typed by restriction fragment length polymorphism (RFLP). Three different RFLP types and mixtures of these types were observed. Direct PCR products of one chicken farm were further typed by direct sequencing and two temporally separated sequence types could be distinguished. Campylobacter strains isolated by culture were also typed by RFLP and direct sequencing revealing close accordance with the corresponding direct PCR products.

In vitro genotypic variation of Campylobacter coli documented by pulsed-field gel electrophoretic DNA profiling: implications for epidemiological studies

Six isolates of Campylobacter coli from different pig herds were subcultured up to 50 times over a 6-month period and DNA samples suitable for pulsed-field gel electrophoretic (PFGE) profiling prepared at regular (1, 20, 40 and 50 passages) intervals. In 5/6 strains, changes in the banding patterns of Sma1, Sal1 and/or BamH1 digests were observed. In one such strain the differences were considered artifactual. However, significant alterations in PFGE profiles between subcultures of four strains were seen, irrespective of the restriction enzyme used. Spontaneous intramolecular genomic rearrangements were considered the most likely mechanism for the changes observed. A numerical analysis based upon the combined distribution of Sma1- and sal1-derived fragments clustered most strain subcultures together, with the exception of those from one isolate which were divided into two clusters. The effect of spontaneous genetic change on PFGE profiles must be considered when evaluating strain relationships. Numerical techniques may aid data interpretation but results must be evaluated cautiously.

Effect of low temperatures on growth, structure, and metabolism of Campylobacter coli SP10

The effect of low temperatures on the survival, structure, and metabolism of Campylobacter coli SP10, a virulent strain, was investigated. C. coli became nonculturable rapidly at 20 and 10 degree C and slightly later at 4 degrees C. Incubation in a microaerobic atmosphere improved survival, but after day 8, campylobacters were detectable by direct-count procedures only. The increase in the number of coccoid cells was most pronounced at 37 degrees C but also was noticeable at 20 and 10 degrees C. Two forms of coccoid cells were seen electron microscopically, but only one (20 and 10 degrees C) seemed to be a degenerative form. The flagella were shorter at 20 and 10 degrees C, a result which correlates well with the observed slight changes in the 62-kDa protein band. The fatty acid composition of bacterial cells was influenced significantly by low temperatures. An increase in the short-chain and unsaturated acids was noted; above all, a drastic increase in C19:0 cyc at 20 degrees C with a concomitant decrease in C18:1 trans9,cis11 was seen. The concentrations of excreted metabolites were analyzed to obtain information on metabolic activity. Depending on the magnitude of the temperature downshift, the production of organic acids decreased, but it was always observable after a temperature-specific lag phase and regardless of ability to be cultured. Under optimal conditions, succinate, lactate, and acetate were the main metabolites, other acids being of less importance. The pattern changed significantly at lower temperatures. Succinate was never detected at 20 degrees C and was only occasionally detected at 10 and 4 degrees C. At the same time, fumarate concentrations, which are normally not detectable at 37 degrees C, were highest at 20 degrees C and reduced at 10 and 4 degrees C. Inactivation of fumarate reductase was considered to be a possible explanation.

[The role of the "milk" factor in the transmission of Campylobacter infection]

The epidemiological survey of the foci of campylobacteriosis confirmed the activity of the "milk" factor in the transmission of this enteric infection. The proliferation of Campylobacter in milk corresponded to the general regularities of the growth of bacterial population in the closed system. Most of the Campylobacter strains under study retained their viability in cooled boiled milk for a longer time.

Polymerase chain reaction assay for detection of Campylobacter coli and Campylobacter jejuni in poultry meat

Primers of 16S rRNA and flaA genes were used to optimise a PCR technique for detecting thermotolerant campylobacters in poultry meat. Different methods for crude DNA extraction were also evaluated. The use of flaA primers and extraction of nucleic acid by boiling and proteinase K gave good results in the detection of Campylobacter either in artificially or naturally contaminated foodstuffs. The lowest sensitivity limit for the PCR reaction was 10(1)-10(2) thermophilic Campylobacter cells either in pure cultures or in artificially and naturally contaminated poultry skins, corresponding to a concentration of 10(2)-10(3) Campylobacter/ml or g product. The PCR method we devised had a high sensitivity and specificity. It appears to give better results than conventional methods and is very easy and fast, requiring only eight hours to detect thermotolerant Campylobacter from poultry meat. In contrast, conventional methods require almost 4 days.

Enrichment medium for isolation of Campylobacter jejuni-Campylobacter coli

A kaseini-broth enrichment medium (KBEM) for the isolation improvement of Campylobacter jejuni-Campylobacter coli from stool samples is described. Isolation of Campylobacters from stool specimens by direct inoculation onto solid selective medium was compared with isolation after twenty-four hours enrichment at 37 degrees C in KBEM, followed by subculture onto the same solid selective medium. Of 156 examined stool samples from diarrhoeal children positive results were obtained from 17 patients altogether: 11 by direct inoculation on selective media and 6 only owing to enrichment. Thus, an increase of 35.3% in the isolation rate was obtained by using the enrichment medium. The same medium allows the preservation of isolates of Campylobacter jejuni-Campylobacter coli for 2 months and longer at 37 degrees C.

Oxygen tolerance estimates in Campylobacter species depend on the testing medium

Oxygen tolerance of the microaerophile Campylobacter jejuni subsp. jejuni varied with different brands of complex media which were used for plating the dilute cell suspensions. The tryptone component was one factor. With some tryptones growth occurred at 21% oxygen whereas with others there was no growth at oxygen levels of 15% or higher. A chemically-defined, agar-solidified plating medium was used to estimate the oxygen tolerance of Camp. jejuni subsp. jejuni, Camp. coli and Camp. fetus subsp. fetus, and also to assess the effect of added scavengers of reactive oxygen intermediates on the oxygen tolerance. Some scavengers such as allopurinol, azelaic acid, caffeine, cimetidine, TEMPOL and pyruvate enhanced oxygen tolerance markedly whereas others such as carnosine, dimethyl thiourea, spermidine and superoxide dismutase had little effect.

In vitro activity of new quinoxaline compounds against Campylobacter species and Clostridium difficile

SC-44914 and SC-44942-A are two new quinoxaline compounds with a spectrum of activity similar to that of metronidazole. We studied the activity of SC-44914 and SC-44942-A against 35 Campylobacter jejuni, 30 C. coli, and 20 Clostridium (Cl.) difficile and compared it with that of metronidazole by utilizing an agar dilution method. The quinoxalines had little activity against the C. jejuni and C. coli [minimum inhibitory concentration (MIC)90 > or = 64 micrograms/ml]. SC-44914 and SC-44942-A had excellent activity against Cl. difficile (MIC90 < or = 0.06 micrograms/ml for SC 44914, and 0.5 micrograms/ml for SC-44942A).