Drug resistance in Campylobacter jejuni, C coli, and C lari isolated from humans in north west England and Wales, 1997

AIMS: To test the sensitivity of strains of Campylobacter species isolated from humans in England and Wales against a range of antimicrobial agents for the purpose of monitoring therapeutic efficacy and as an epidemiological marker. METHODS: An agar dilution breakpoint technique was used to screen isolates against ampicillin, chloramphenicol, gentamicin, kanamycin, neomycin, tetracycline, nalidixic acid, ciprofloxacin, and erythromycin. Minimal inhibitory concentrations (MIC) were also determined for a sample of quinolone resistant strains. RESULTS: Approximately 50% of strains tested were resistant to at least one drug. Strains which were resistant to four or more of the drugs tested were classified as multiresistant; this occurred in 11.3% of C jejuni, 19.9% of C coli, and 63.6% of C lari. Resistance to erythromycin occurred in 1.0% of C jejuni and 12.8% of C coli. Resistance to quinolones occurred in 12% of strains, with a ciprofloxacin MIC of > 8 mg/l and a nalidixic acid MIC of > 256 mg/l; a further 4% of strains had intermediate resistance with a ciprofloxacin MIC of between 0.5 and 2 mg/l (fully sensitive strains, 0.25 mg/l or less) and a nalidixic acid MIC of between 32 and 64 mg/l (fully sensitive strains, 8 mg/l or less). CONCLUSIONS: Resistance to quinolones in campylobacters from human infection may relate to clinical overuse or use of fluoroquinolones in animal husbandry. Both veterinary and clinical use should be reconsidered and fluoroquinolone drugs used only as a treatment for serious infections requiring hospital admission. Erythromycin resistance is still rare in C jejuni but much more common in C coli.     

Ciprofloxacin resistance and its molecular mechanism in Campylobacter spp. isolated in Kuwait

Campylobacter spp. are an important cause of diarrhea in Kuwait. Because susceptibility data for ciprofloxacin and erythromycin, the two recommended drugs for treatment, are not available for this part of the world, 64 Campylobacter spp. isolates obtained from human diarrheal stools in Kuwait during 2000--2003 were studied for susceptibility to these antimicrobials by E-test. The utility of a simple mismatch amplification mutation assay (MAMA) PCR to detect base substitution in the gyrA gene mediating resistance to ciprofloxacin was also explored. Approximately, 53% (34/64) of the isolates were resistant to ciprofloxacin (MIC, 4-64 microg/ml) and 5% (3/64) to erythromycin (MIC>256 microg/ml). MAMA PCR showed a Thr-86-to-Ile mutation in gyrA gene of 23/26 ciprofloxacin-resistant C. jejuni, and in all resistant C. coli. Sequencing of PCR product showed that two resistant strains of C. coli studied had Thr-86-to-Ile (ACT--> ATT) gyrA mutation and three resistant strains of C. jejuni studied had Thr-86-to-Ile (ACA--> ATA) gyrA mutation. In addition, all the three C. jejuni strains had silent mutations. Thus, ciprofloxacin is of limited use for treatment in Kuwait and MAMA PCR is a useful assay to study gyrA mutation. Because Kuwait has a large expatriate population of workers, it can be a focus of spread of antimicrobial resistance.     

Comparison of broth microdilution,E Test,and agar dilution methods for antibiotic susceptibility testing of Campylobacter jejuni and Campylobacter coli

A standardized broth microdilution method was compared to the E test and an agar dilution method for the antimicrobial susceptibility testing of Campylobacter jejuni and C. coli isolates. A group of 47 human clinical isolates, 37 isolates from retail poultry, and 29 isolates from living turkeys (total, 113 isolates) was included in the study. These encompassed 92 C. jejuni and 21 C. coli strains. The MICs of six antimicrobial agents were determined by the broth microdilution and E test methods, and the strains of human origin were additionally tested by the agar dilution method. In general, broth microdilution MICs agreed within 1 log(2) MIC increment with 90.0% of E test results and 78.7% of agar dilution test results. The agar dilution method gave much lower gentamicin MICs than the broth microdilution method, but the data were significantly (P < 0.01) correlated and there was 100% agreement in the sensitivities and specificities in the comparison of the tests. The broth microdilution method had the highest sensitivity for analysis of the susceptibilities of Campylobacter to nalidixic acid and trimethoprim-sulfamethoxazole. The MICs of ciprofloxacin and erythromycin complied numerically by all three methods. The classification of the results and the correlation of the data demonstrated a high degree of agreement. All methods were equally suitable for the testing of the sensitivity of Campylobacter to tetracycline. Thus, the broth microdilution method appears to be an easy and reliable method for determination of the MICs of antibiotics for C. jejuni and C. coli, and it may offer an interesting alternative to MIC determination by the agar dilution technique or the E test.     

Inhibition of Campylobacter coli and Campylobacter jejuni by antibiotics used in selective growth media.

The ability of Campylobacter coli and Campylobacter jejuni to grow in the presence of antibiotics used in selective growth media was compared. MIC data for C. coli indicated that some strains were more susceptible to the antibiotics than were the C. jejuni strains tested. A reduction of greater than 1 log cycle in the numbers of cells growing on plates containing antibiotics was considered to be a marked level of inhibition. Only one of nine of the antibiotic combinations studied did not markedly inhibit most of the C. coli strains tested. Although one C. coli strain was not inhibited by any of the antibiotic combinations, the other six strains were inhibited for up to 7 log cycles. The addition of blood or growth supplements reduced but did not eliminate the inhibitory effect. The inhibition of laboratory strains of C. coli on media developed for the isolation of Campylobacter spp. indicates that the incidence of C. coli may be underestimated.     

Fitness of macrolide resistant Campylobacter coli and Campylobacter jejuni

The aim of this study was to investigate the fitness of macrolide resistant Campylobacter coli and Campylobacter jejuni. The in vitro growth, the survival on food matrix, and the in vivo colonization of C. jejuni and C. coli susceptible isolates and their isogenic resistant mutants were studied. In vitro experiments demonstrated that macrolide resistance imposed a fitness cost when the susceptible strains and their isogenic resistant mutants were cultured in competition. When inoculated in food matrix, the resistant C. jejuni mutant was no longer detectable after 3 to 5 days but the susceptible strain remained detectable for over 18 days. No difference in survival in food matrix was observed between susceptible and resistant C. coli. When inoculated in vivo in chickens, the macrolide susceptible and resistant C. coli displayed similar levels of colonization, both in separated inoculations and during competitive assays. Strikingly, when mono-inoculated or co-inoculated into chickens, macrolide susceptible C. jejuni outcompeted the macrolide resistant population. However, a spontaneous mutant that evolved in vivo showed a colonization capacity similar to the susceptible strain. Our findings demonstrate the effect of macrolide resistance on the fitness of Campylobacter but suggest that evolved mutants may be as fit as susceptible strains.     

Effects of low-level ciprofloxacin challenge in the in vitro development of ciprofloxacin resistance in Campylobacter jejuni

The effects on MIC values and the selection of different base substitutions in the quinolone resistance determining region (QRDR) of gyrA were studied on initially ciprofloxacin-susceptible Campylobacter jejuni strains by challenging them to 0.125 mg/L of ciprofloxacin. This ciprofloxacin challenge selected variants with ciprofloxacin MIC levels up to 32 mg/L. Repeated experiments under identical conditions resulted in different responses in MIC levels and alterations in the QRDR of gyrA. A characteristic outcome to ciprofloxacin challenges was the appearance of double peaks in the sequencing chromatograms of QRDR. This finding suggested the coexistence of subpopulations possessing Thr86 --> Ile and/or Asp90 --> Asn mutations alongside the unmutated parent population. In some cases, bacterial variants expressing ciprofloxacin-resistant phenotypes possessed no mutations in their QRDR. These variants were prone to regain susceptibility to ciprofloxacin rapidly after the removal of the selection pressure, whereas the QRDR-mutated variants persisted over several subcultivations in a medium without ciprofloxacin. In conclusion, a low ciprofloxacin concentration of 0.125 mg/L selects a variety of QRDR mutations and also a QRDR-independent resistance mechanism, which may coexist with each other in a C. jejuni population. Persistent ciprofloxacin challenge selects Thr86 --> Ile and/or Asp90 --> Asn mutants.     

Characterization and description of "Campylobacter upsaliensis" isolated from human feces

During a 3-year period, "Campylobacter upsaliensis" was isolated from 99 patients. Phenotypic characterization and numerical analysis of protein electrophoregrams showed evidence that "C. upsaliensis" is a distinct Campylobacter species with unique characteristics. The MBCs of 13 antibiotics were determined. In general, these organisms were highly susceptible to drugs that were present in the selective isolation media, making none of the available selective media suitable for the isolation of "C. upsaliensis." Ten strains were found to be resistant to erythromycin (MBCs, greater than or equal to 12.50 mg/liter). Plasmid DNA was detectable in 89 of the 99 strains; 16 plasmid profiles could be identified. Plasmid pattern 16, containing four plasmids of 52, 32, 5.5, and 2.6 megadaltons, represented 60.7% of the plasmid-containing strains. None of the "C. upsaliensis" strains could be agglutinated with antisera against heat-labile antigens from C. jejuni, C. coli, or C. laridis. "C. upsaliensis" was found to be susceptible to serum killing and was readily phagocytized by human polymorphonuclear cells.     

In vitro susceptibility of diarrhoea producing gram negative enteric bacteria to sulfasalazine, 5-aminosalicylic acid, sulfapyridine and four quinolones. Brief report

The in vitro susceptibility of diarrhoea producing Gram negative enteric bacteria to sulfasalazine, 5-aminosalicylic acid, sulfapyridine and four quinolones was investigated using an agar dilution method. All strains were resistant to 1600 micrograms/ml of sulfasalazine and 5-aminosalicylic acid. MIC range of sulfapyridine for Y. enterocolitica was 3.1-25 micrograms/ml (median:6.2) and for Salmonella 25-100 micrograms/ml (median: 100) Campylobacter jejuni/coli were less susceptible to sulfapyridine with MIC values ranging from 200 to 800 micrograms/ml. Shigella and three of five E. coli strains were resistant to 1600 micrograms/ml of sulfapyridine. Two strains of E. coli were inhibited by 25 micrograms/ml. All strains were fairly susceptible to enoxacin, ciprofloxacin, pefloxacin and ofloxacin. Cirpofloxacin was the most active drug on weight basis.     

Comparative in vitro activity of a new macrolide RU 28965 and of erythromycin against Chlamydia trachomatis

Activity of a new macrolide, RU 28965, and erythromycin against 8 Chlamydia trachomatis strains isolated from the human genital tract was studied. Minimal inhibitory concentrations were determined using cycloheximide-treated McCoy cells. Giemsa and immunofluorescence staining with monoclonal antibodies were used to detect Chlamydial inclusions. Immunofluorescence proved more sensitive and easier to read. All the strains were highly susceptible to RU 28965 (MIC = 0.05 mg/l - 0.1 mg/l) and erythromycin (MIC = 0.02 mg/l - 0.2 mg/l).     

Inaccuracy of routine susceptibility tests for detection of erythromycin resistance of Campylobacter jejuni and Campylobacter coli

In The Netherlands, both an increase in and regional differences in erythromycin resistance of Campylobacter jejuni and Campylobacter coli have been reported. To determine the accuracy of routine tests for erythromycin resistance, 48 erythromycin-resistant isolates from various laboratories that participate in the Dutch surveillance of Campylobacter infections were reinvestigated. Initial susceptibility testing for erythromycin had been performed by disk diffusion in six and MIC-based methods in two laboratories. Reinvestigation was carried out using broth microdilution as a reference standard, as well as E -test and genetic resistance testing. Of 36 C. jejuni isolates reported by the initial laboratories as erythromycin-resistant, four (11%) and five (14%) were confirmed as erythromycin-resistant using broth microdilution according to CLSI and EUCAST resistance criteria, respectively. Erythromycin resistance was found in eight of 12 (67%) C. coli isolates according to both criteria. Results of E -tests were in accordance with these results in all isolates. Resistance-associated mutations in the 23S rRNA gene (A2059G and A2058T) were found in all isolates showing high-level resistance, whereas none were found in susceptible isolates. Routine determination of the erythromycin resistance of C. jejuni and C. coli shows unacceptable interlaboratory variation. In the absence of standardized protocols and interpretive criteria for disk diffusion, and while we await the development of easily applicable and reliable methods for molecular resistance testing, the use of broth microdilution remains the best method.     

Occurrence of plasmids and antibiotic resistance among Campylobacter jejuni and Campylobacter coli isolated from healthy and diarrheic animals.

Serologically defined strains of Campylobacter jejuni and Campylobacter coli from healthy and diarrheic animals were examined for the occurrence of plasmid DNA in association with the antibiotic susceptibility of the bacterial host and the health status of the animal host. Of all campylobacter organisms surveyed, 53% (116 of 200) contained plasmid DNA. A plasmid occurrence rate of 73.8% was obtained for C. coli from healthy pigs, contrasted by lower plasmid occurrence rates for C. coli from diarrheic pigs (30%) and from all diarrheic animals (21.4%). For C. jejuni, in contrast, only 13.6% of healthy cattle contained plasmid DNA, contrasted by a higher plasmid occurrence rate of 31.2% from diarrheic cattle. A high plasmid occurrence rate of 75.8% was observed for C. jejuni from healthy chickens. Campylobacter plasmids ranged in size from less than or equal to 1 to 86 megadaltons. Antibiotic susceptibility for 52 animal isolates (excluding chickens) indicated that most isolates were susceptible to kanamycin, erythromycin, gentamicin, tetracycline, and compound sulfonamide, whereas few were susceptible to bacitracin (19.2%); approximately half were susceptible to ampicillin (55.8%) and streptomycin (51.9%), and no isolates were susceptible to penicillin G. More isolates containing plasmids were resistant to ampicillin, tetracycline, and gentamicin than were isolates not carrying plasmids, there being a statistically significant difference for tetracycline and gentamicin, which suggested that these two antibiotics were probably plasmid mediated. The antibiotic susceptibility patterns of 21 chicken isolates of C. jejuni, by contrast, were different in that most were susceptible to ampicillin in addition to kanamycin, erythromycin, and gentamicin, whereas few wer susceptible to compound sulfonamide, streptomycin, and tetracycline in addition to penicillin G and bacitracin. A 30- or 39-megadalton plasmid, or both, common to many of the chicken isolates was usually associated with tetracycline resistance.     

Fitness cost of fluoroquinolone resistance in Campylobacter coli and Campylobacter jejuni

In this study, the fitness cost of fluoroquinolone resistance was evaluated in vitro, on food matrices, and in vivo, using Campylobacter coli and Campylobacter jejuni in vitro selected mutants. In vitro, the growth rate of the susceptible (wild type) and resistant (mutant) strains did not differ when cultured separately. However, by conducting sequential passages of mixed cultures, the ratio of the resistant mutant to the susceptible strain decreased for C. coli but not for C. jejuni. When the wild type and the mutant were co-inoculated on food matrices, mutants were no longer detectable 3 to 5 days after artificial contamination, but the wild-type strains remained detectable for over 13 days. In mono-inoculated animals, no difference was observed between wild-type and mutant fecal titers. When co-inoculated into chickens, the susceptible strain outcompeted the resistant mutant for C. coli and for C. jejuni. However, for C. coli, if the resistant strain was already present in animals, it could persist at high titers in the digestive tract even in the presence of the wild-type strain. Together, these findings suggest that, depending on strain and study conditions, fluoroquinolone resistance can impose a fitness cost on Campylobacter.     

Development of a standardized susceptibility test for campylobacter with quality-control ranges for ciprofloxacin, doxycycline, erythromycin, gentamicin, and meropenem

A standardized agar dilution susceptibility testing method was developed for Campylobacter that consisted of testing on Mueller-Hinton medium supplemented with 5% defibrinated sheep blood in an atmosphere of 10% CO2, 5% O2, and 85% N2. Campylobacter jejuni ATCC 33560 was identified as a quality-control (QC) strain. Minimal inhibitory concentration (MIC) QC ranges were determined for two incubation time/temperature combinations: 36 degrees C for 48 hr and 42 degrees C for 24 hr. Quality-control ranges were determined for ciprofloxacin, doxycycline, erythromycin, gentamicin, and meropenem. For all antimicrobial agents tested at both temperatures, 95-100% of the QC MIC results fell within recommended QC ranges. Twenty-one Campylobacter clinical isolates, encompassing five species of Campylobacter (C. jejuni, C. coli, C. jejuni, subsp. doylei, C. fetus, and C. lari) were tested in conjunction with the C. jejuni QC strain. While C. jejuni and C. coli could be reliably tested under both test conditions, growth of C. jejuni subsp. doylei, C. fetus, and C. lari isolates was inconsistent when incubated at 42 degrees C. Therefore, it is recommended that these species only be tested at 36 degrees C.     

Evaluation of 11 PCR assays for species-level identification of Campylobacter jejuni and Campylobacter coli

We examined the sensitivity and specificity of 11 PCR assays described for the species identification of Campylobacter jejuni and Campylobacter coli by using 111 type, reference, and field strains of C. jejuni, C. coli, and Campylobacter lari. For six assays, an additional 21 type strains representing related Campylobacter, Arcobacter, and Helicobacter species were also included. PCR tests were initially established in the laboratory by optimizing conditions with respect to five type and reference strains of C. jejuni, C. coli, and C. lari. One PCR test for C. coli failed to give appropriate results during this initial setup phase and was not evaluated further. The remaining 10 assays were used to examine heated lysate and purified DNA templates as appropriate of well-characterized type, reference, and field strains of C. jejuni (n = 62), C. coli (n = 34), and C. lari (n = 15). The tests varied considerably in their sensitivity and specificity for their respective target species. No assay was found to be 100% sensitive and/or specific for all C. jejuni strains tested, but four assays for C. coli gave appropriate responses for all strains examined. Between one and six strains of C. jejuni gave amplicons in four of seven C. jejuni PCR tests only where purified DNA was used as the template; corresponding results were seen with one strain of C. coli in each of three assays for the latter species. Our findings indicate that a polyphasic strategy for PCR-based identification should be used to identify C. jejuni and C. coli strains. The data may assist laboratories in selecting assays suited for their needs and in designing evaluations of future PCR tests aimed to identify these species.     

In vitro activity of roxithromycin, new semisynthetic macrolide against obligate anaerobes

The "in vitro" susceptibility to roxithromycin and three other macrolides of 236 anaerobes isolated from clinical samples in 1984/1985 was determined by an agar-dilution method on Wilkins Chalgren medium. 90% of Gram positive cocci were susceptible to both roxithromycin and josamycin (MIC less than 1 mg/l, whereas 1 mg/l erythromycin and 2 mg/l spiramycin were able to inhibit respectively 46 and 86% of the same tested strains. No resistance to the four macrolides was observed among Eubacterium, propionibacterium and Bifidobacterium. Two C. perfringens strains and one C. difficile strain were resistant to all four macrolides, while 97% of Clostridium sp. strains were inhibited by 4 mg/l erythromycin, josamycin or roxithromycin. Against Gram positive anaerobes, roxithromycin was equal or superior to erythromycin and spiramycin. At a concentration of 4 mg/l, roxithromycin inhibited 82% of B. fragilis strains. Roxithromycin and josamycin were more active against Gram negative bacilli that erythromycin and spiramycin. Macrolides had no effect on Fusobacterium strains. In this study, 4 mg/l roxithromycin inhibited 217 of the 236 anaerobic strains investigated (92%).     

DNA relatedness among strains of Campylobacter jejuni and Campylobacter coli with divergent serogroup and hippurate reactions.

Eleven strains of Campylobacter from earlier fluorescent-antibody studies were examined by DNA hybridization to determine their species. Three of the strains hydrolyzed sodium hippurate, and eight did not. Four of the hippurate-negative strains were in Campylobacter jejuni serogroups, and the remaining strains were in both C. jejuni and Campylobacter coli serogroups. DNA relatedness to type strains of C. jejuni and C. coli indicated that all three of the hippurate-positive strains and two of the hippurate-negative strains were C. jejuni. The six remaining hippurate-negative strains were C. coli. Two of the hippurate-negative strains in C. jejuni serogroups were C. jejuni, and two were C. coli. Three of the strains in serogroups of both species were C. jejuni, and four were C. coli. These studies confirm that a few strains of C. jejuni are hippurate negative and show that identical or highly related antigens are found in C. coli and C. jejuni.     

In-vitro activity of cefonicid on hospital bacteria. Regression line and proposal for critical values

Antimicrobial activity of cefonicid, a new second generation cephalosporin, against 315 hospital isolates (4th trimester 1984) was investigated. E. coli and Proteus mirabilis were the most susceptible species. All E. coli strains except one were inhibited at 8 mg/l (modal MIC: 0.5); MICs of all indole + Proteus were 8 mg/l (modal MIC: 0.06). Another group was moderately susceptible: MICs of Klebsiella and Citrobacter ranged from 0.12 to 128 mg/l, but MICs of 50% of these strains were less than or equal to 4 mg/l; MIC was less than or equal to 8 mg/l for 75% of indole + Proteus and Providencia strains; tested Proteus vulgaris were especially resistant (MICs greater than 128 mg/l). Most Enterobacter and Serratia strains showed little susceptibility (modal MIC for both species greater than or equal to 128 mg/l). MICs of all tested Pseudomonas aeruginosa strains were greater than 128 mg/l. 20 of the 24 tested Acinetobacter strains had a MIC of greater than or equal to 128 mg/l. For Staphylococcus aureus, 88% of methicillin-sensitive strains were inhibited by concentrations of 2 to 4 mg/l whereas methicillin-resistant strains were resistant to cefonicid (75%: MIC greater than 64 mg/l). Enterococci were resistant to cefonicid. A correlation curve was established (Enterobacteria and Staphylococci). On the basis of cefonicid's pharmacokinetic characteristics, critical concentrations are proposed.     

Azithromycin resistance inCampylobacter jejuni andCampylobacter coli

The MICs of erythromycin, azithromycin and ciprofloxacin were determined for 60 human fecal isolates ofCampylobacter. Of these, 30 strains selected on the basis of their resistance to erythromycin by disk diffusion were highly resistant to both erythromycin and azithromycin. Nine of these selected isolates were resistant to ciprofloxacin. The remaining 30 strains were non-selected, consecutive isolates ofCampylobacter susceptible to erythromycin by disk diffusion and were shown to be two- to five-fold more susceptible to azithromycin than to erythromycin as determined by MIC testing.     

Identification of ciprofloxacin-resistant Campylobacter jejuni by use of a fluorogenic PCR assay

Fluoroquinolones are one class of antimicrobial agents commonly used to treat severe Campylobacter jejuni infection. C. jejuni strains resistant to high levels of the fluoroquinolone ciprofloxacin (MIC >/=16 microg/ml) have been predominantly characterized with a C-->T transition in codon 86 of gyrA. The gyrA gene encodes one subunit of DNA gyrase, which is a primary target for fluoroquinolone antibiotics. This study establishes a rapid PCR-based TaqMan method for identifying ciprofloxacin-resistant C. jejuni strains that carry the C-->T transition in codon 86 of gyrA. The assay uses real-time detection, eliminating the need for gel electrophoresis. Optimization of the assay parameters using purified Campylobacter DNA resulted in the ability to detect femtogram levels of DNA. The method should be useful for monitoring the development of ciprofloxacin resistance in C. jejuni. Compiled nucleotide sequence data on the quinolone resistance-determining region of gyrA in Campylobacter indicate that sequence comparison of this region is a useful method for tentative identification of Campylobacter isolates at the species level.     

Fluorescent amplified fragment length polymorphism genotyping of Campylobacter jejuni and Campylobacter coli strains and its relationship with host specificity, serotyping, and phage typing

Fluorescent amplified fragment length polymorphism (FAFLP) analysis was applied to 276 Campylobacter jejuni strains and 87 Campylobacter coli strains isolated from humans, pigs, cattle, poultry, and retail meats to investigate whether certain FAFLP genotypes of C. jejuni and C. coli are associated with a particular host and to determine the degree of association between FAFLP-defined genotypes and heat-stable serotypes and/or phage types. Within C. coli, the poultry strains clustered separately from those of porcine origin. In contrast, no evidence of host specificity was detected among C. jejuni strains. While C. coli strains show host specificity by FAFLP genotyping, C. jejuni strains that are genotypically similar appear to colonize a range of hosts, rather than being host adapted. Some serotypes and/or phage types (C. jejuni serotype HS18, phage type PT6, and serophage type HS19/PT2 and C. coli HS66, PT2, and HS56/PT2) were the most homogeneous by FAFLP genotyping, while others were more heterogeneous (C. jejuni HS5 and PT39, and C. coli HS24 and PT44) and therefore poor indicators of genetic relatedness between strains. The lack of host specificity in C. jejuni suggests that tracing the source of infection during epidemiological investigations will continue to be difficult. The lack of congruence between some serotypes and/or phage types and FAFLP genotype underlines the need for phenotypic testing to be supplemented by genotyping. This study also demonstrates how, in general, FAFLP generates "anonymous" genetic markers for strain characterization and epidemiological investigation of Campylobacter in the food chain.