Use of an alkaline phosphatase-labeled synthetic oligonucleotide probe for detection of Campylobacter jejuni and Campylobacter coli.

A commercially available synthetic nucleic acid probe (SNAP) conjugated to alkaline phosphatase was compared with standard culture techniques for detecting Campylobacter species. The SNAP was able to detect either 5 ng of C. jejuni DNA or 10(5) CFU of bacteria. The SNAP could also detect DNA extracted from 10(5) CFU in mock-infected stool samples. The SNAP detected C. jejuni and C. coli but showed no reactivity with C. laridis, C. fetus subsp. fetus, C. fetus subsp. venerealis, C. fennelliae, "C. upsaliensis," C. cinaedii, C. fecalis, C. hyointestinalis, C. mucosalis, or Helicobacter (Campylobacter) pylori. The SNAP also showed no cross-reactivity with other enteric pathogens. When applied to pure cultures, the SNAP detected 55 clinical isolates of C. jejuni and 11 clinical isolates of C. coli, with an accuracy of 100%. When applied directly to clinical specimens, the SNAP detected Campylobacter spp. in 19 of 23 culture-positive stool specimens (sensitivity, 82.6%; specificity, 100%). Pure cultures of the Campylobacter strains isolated from the four probe-negative, culture-positive stool specimens gave positive reactions with the SNAP. While the SNAP had excellent sensitivity and specificity for isolated bacterial colony isolates, the main limitation to the Campylobacter probe detection kit may be the sensitivity limit on direct detection of Campylobacter organisms in stools.     

PCR detection, identification to species level, and fingerprinting of Campylobacter jejuni and Campylobacter coli direct from diarrheic samples.

Three sets of primers were designed for PCR detection and differentiation of Campylobacter jejuni and Campylobacter coli. The first PCR assay was designed to coidentify C. jejuni and C. coli based on their 16S rRNA gene sequences. The second PCR assay, based on the hippuricase gene sequence, identified all tested reference strains of C. jejuni and also strains of that species which lack detectable hippuricase activity. The third PCR assay, based on the sequence of a cloned (putative) aspartokinase gene and the downstream open reading frame, identified all tested reference strains of C. coli. The assays will find immediate application in the rapid identification to species level of isolates. The assays combine with a protocol for purification of total DNA from fecal samples to allow reproducible PCR identification of campylobacters directly from stools. Of 20 clinical samples from which campylobacters had been cultured, we detected C. jejuni in 17, C. coli in 2, and coinfection of C. jejuni and Campylobacter hyointestinalis in 1. These results were concordant with culture and phenotypic identification to species level. Strain typing by PCR-restriction fragment length polymorphism of the flagellin (flaA) gene detected identical flaA types in fecal DNA and the corresponding campylobacter isolate. Twenty-five Campylobacter-negative stool samples gave no reaction with the PCR assays. These PCR assays can rapidly define the occurrence, species incidence, and flaA genotypes of enteropathogenic campylobacters.     

Specific detection of Campylobacter jejuni and Campylobacter coli by using polymerase chain reaction.

Development of a routine detection assay for Campylobacter jejuni and Campylobacter coli in clinical specimens was undertaken by using the polymerase chain reaction (PCR). An oligonucleotide primer pair from a conserved 5' region of the flaA gene of C. coli VC167 was used to amplify a 450-bp region by PCR. The primer pair specifically detected 4 strains of C. coli and 47 strains of C. jejuni; but it did not detect strains of Campylobacter fetus, Campylobacter lari, Campylobacter upsaliensis, Campylobacter cryaerophila, Campylobacter butzleri, Campylobacter hyointestinalis, Wolinella recta, Helicobacter pylori, Escherichia coli, Shigella spp., Salmonella spp., Vibrio cholerae, Citrobacter freundii, or Aeromonas spp. By using a nonradioactively labeled probe internal to the PCR product, the assay could detect as little as 0.0062 pg of purified C. coli DNA, or the equivalent of four bacteria. In stools seeded with C. coli cells, the probe could detect between 30 and 60 bacteria per PCR assay. The assay was also successfully used to detect C. coli in rectal swab specimens from experimentally infected rabbits and C. jejuni in human stool samples.     

Evaluation of a latex agglutination method for the rapid identification of Campylobacter jejuni/coli

A latex agglutination assay was developed to identify Campylobacter jejuni and Campylobacter coli. We evaluated the specificity, reproducibility and utility of the assay for clinical use and the following results were obtained. 1) To prepare standardized antigen, bacterial cells must be suspended to a density of 1 to 5 McFarland unit, and heated at 121 degrees C for 10 to 30 min. 2) Bacterial cells may be suspended either in the solution provided with the kit, or in physiological saline, without affecting the results. 3) Of C. jejuni, 94 strains, 6 of C. coli, and 3 of "Campylobacter upsaliensis", all tested positive without exception. All other Campylobacter species, encompassing 13 species and 80 strains, were negative. An additional 9 species and 30 strains, of non-Campylobacter gram negative bacteria, isolated on the Campylobacter selection agar medium, also were uniformly negative. Based on these results, we conclude that bacteria testing positive with the kit can be identified as C. jejuni/coli. Interestingly, "C. upsaliensis", although isolated very rarely from the clinical specimens, also tested positive.     

Evaluation of the ProSpecT Microplate Assay for detection of Campylobacter: a routine laboratory perspective

Objectives  To evaluate the use of the new enzyme-linked immunosorbent assay, the ProSpecT Campylobacter Microplate Assay (Alexon-Trend, Minneapolis, MN, USA), which allows 2-h detection of both Campylobacter jejuni and Campylobacter coli antigen directly in stool specimens.
Methods  Over 4 months, all stool samples preserved in Cary–Blair medium, or fresh specimens, from non-hospitalized children and HIV-infected patients (adults and children), submitted to our laboratory were evaluated with the ProSpecT Campylobacter Microplate Assay. Results were compared with those obtained by routine culture methods using both a specific medium and a filtration method for the recovery of Campylobacter spp.
Results  Of the 1205 stool specimens cultured, 101 were found to be positive for either C. jejuni or C. coli , giving an overall recovery rate of 8.38%. Ninety samples were positive by both culture and ProSpecT Campylobacter Microplate Assay, and 11 were positive by culture only, giving a sensitivity of 89.1%. In addition, of 1104 samples negative by culture, 25 were initially positive by ProSpecT Campylobacter Microplate Assay. We found no cross-reaction with other bacterial enteropathogens isolated from stool specimens. These results thus confirm a high specificity (97.7%) for both C. jejuni and C. coli. The positive and negative predictive values found were 78.3% and 99%, respectively. There was no statistically significant difference in sensitivity and specificity if the stool was fresh or preserved with Cary–Blair medium.
Conclusion  These data suggest that the ProSpecT Campylobacter Microplate Assay is a rapid and easy-to-use test for the detection of both C. jejuni and C. coli in stool specimens. It could be used for patients for whom early antibiotic therapy is needed or for epidemiologic studies.     

实时荧光PCR方法快速检测空肠弯曲菌方法的建立

目的建立实时荧光PCR快速检测空肠弯曲菌的方法。方法以空肠弯曲杆菌HipO基因的保守序列为模板设计特异性引物探针,建立一种能快速检测样本中空肠弯曲杆菌的实时荧光PCR方法;对方法的特异性和敏感性进行评价,并以正常人粪便为空白样本,添加一定量空肠弯曲菌标准株菌液进行检测,以对方法的检测效果进行初步评价。结果该实时荧光PCR方法只对空肠弯曲杆菌进行特异扩增,同种属的结肠弯曲菌及其他常见食源性病原菌均不能扩增;整个检测过程只需要80min,对空肠弯曲菌菌悬液可检测至5个细菌,对加标粪便样本可检测至10-100个细菌。结论本研究建立的实时荧光PCR检测空肠弯曲菌方法不仅能实现对空弯菌的快速检测,而且还为空弯菌的快速诊断及其引起的食源性疾病的监控溯源提供有意义的参考。     

Simultaneous detection of six diarrhea-causing bacterial pathogens with an in-house PCR-luminex assay

Diarrhea can be caused by a range of pathogens, including several bacteria. Conventional diagnostic methods, such as culture, biochemical tests, and enzyme-linked immunosorbent assay (ELISA), are laborious. We developed a 7-plex PCR-Luminex assay to simultaneously screen for several of the major diarrhea-causing bacteria directly in fecal specimens, including pathogenic Aeromonas, Campylobacter jejuni, Campylobacter coli, Salmonella, Shigella, enteroinvasive Escherichia coli (EIEC), Vibrio, and Yersinia. We included an extrinsic control to verify extraction and amplification. The assay was first validated with reference strains or isolates and exhibited a limit of detection of 10(3) to 10(5) CFU/g of stool for each pathogen as well as quantitative detection up to 10(9) CFU/g. A total of 205 clinical fecal specimens from individuals with diarrhea, previously cultured for enteric pathogens and tested for Campylobacter by ELISA, were evaluated. Using these predicate methods as standards, sensitivities and specificities of the PCR-Luminex assay were 89% and 94% for Aeromonas, 89% and 93% for Campylobacter, 96% and 95% for Salmonella, 94% and 94% for Shigella, 92% and 97% for Vibrio, and 100% and 100% for Yersinia, respectively. All discrepant results were further examined by singleplex real-time PCR assays targeting different gene regions, which revealed 89% (55/62 results) concordance with the PCR-Luminex assay. The fluorescent signals obtained with this approach exhibited a statistically significant correlation with the cycle threshold (C(T)) values from the cognate real-time PCR assays (P < 0.05). This multiplex PCR-Luminex assay enables sensitive, specific, and quantitative detection of the major bacterial causes of gastroenteritis.     

Modified selective medium for isolation of Campylobacter spp. from feces: comparison with Preston medium, a blood-free medium, and a filtration system.

Our previously described (H. Goossens, M. De Boeck, and J. P. Butzler, Eur. J. Clin. Microbiol. 2:389-393, 1983) selective medium, consisting of cefoperazone (15 mg/liter), rifampin (10 mg/liter), colistin (10,000 IU/liter), and amphotericin B (2 mg/liter) (medium M1), for the isolation of Campylobacter jejuni and Campylobacter coli from stool specimens was modified as follows: cefoperazone (30 mg/liter), rifampin (10 mg/liter), and amphotericin B (2 mg/liter) (medium M2). A comparative study of the isolation of Campylobacter spp. from stool specimens was carried out with medium M1; medium M2; a selective blood-free medium consisting (per liter) of charcoal (4 g), ferrous sulfate (0.25 g), sodium pyruvate (0.25 g), casein hydrolysate (3 g), sodium deoxycholate (1 g), nutrient broth no. 2 (25 g), agar (12 g), and cefoperazone (32 mg) (medium M3); and Preston medium containing (per liter) trimethoprim (10 mg), rifampin (10 mg), polymyxin B (5,000 IU), and cycloheximide (100 mg) (medium M4). We also included a filtration system in which membrane filters were applied directly to the surface of the nonselective blood-free medium distributed in small petri dishes. A total of 5,276 stool specimens were tested: 2,788 stool specimens were tested on M1 and M3 in study 1; 2,488 stool specimens were inoculated on the four selective media in study 2, and the last 986 specimens of the 2,488 were tested in parallel with the filtration system. In study 2, 128 Campylobacter strains were isolated from 126 different patients; 85.0, 88.3, 82.5, and 66.6% of these strains were isolated on M1, M2, M3, and M4, respectively. No contaminating fecal flora was found on 65.4, 70.7, 62.4, and 40.3% of the M1, M2, M3, and M4 plates, respectively. Furthermore, C. coli was found to be more susceptible to antibiotics present in the selective media, particularly colistin and polymyxin B, than was C. jejuni. We therefore recommend M2 for the isolation of Campylobacter spp. Finally, the filtration method was found to be easy and cheap; although the sensitivity was low, this method allowed the isolation of new Campylobacter spp. which seem to be associated with diarrhea.     

In vitro susceptibility of Campylobacter jejuni and Campylobacter coli isolated in Austria to erythromycin and ciprofloxacin

More than 200 strains of Campylobacter (C.) jejuni/coli isolated in 1985 and 1987/88 from human fecal specimens were tested for their susceptibility to erythromycin and ciprofloxacin. Their MIC90 as assessed by agar dilution tests was 2.0 and 0.5 mg/l, respectively. Thus, all strains were regarded as susceptible to ciprofloxacin. With 2 out of 55 strains of C. coli the MIC of erythromycin was 8.0 mg/l. Therefore, only 3.6% of the C. coli strains were resistant to erythromycin. All 209 strains of C. jejuni proved to be susceptible to erythromycin.     

Laboratory and clinical evaluation of isolation media for Campylobacter jejuni.

Six selective isolation media were evaluated for their ability to support the growth of Campylobacter jejuni. Colony counts of 70 isolated strains of C. jejuni and recovery studies on these strains in simulated positive feces samples demonstrated that Bolton and Hutchinson' charcoal, cefoperazone, deoxycholate agar and Karmali's charcoal-based selective medium produced the highest recovery rates with the greatest suppression of other fecal flora. C. jejuni colonies were more easily recognized on charcoal-based selective medium. A clinical evaluation performed on 2,780 human, animal, and avian feces specimens confirmed the results of the laboratory investigation. From human samples, 4 more strains of C. jejuni were isolated on charcoal-based selective medium than were isolated on Skirrow medium, and 19 more strains of C. jejuni or C. coli were isolated on charcoal-based selective medium from animal specimens. Suppression of normal fecal flora was also greater on charcoal-based selective medium.     

Detection of Campylobacter species by using polymerase chain reaction and nonradioactive labeled DNA probe]

We have detected Campylobacter species which are now recognized as major pathogens of acute diarrheal disease in humans using polymerase chain reaction (PCR) and a nonradioactive labeled DNA probe. Diagnosis of Campylobacter enteritis without doing culture from stool samples is of great benefit in the laboratory. Two oligonucleotide primers (20 mer) complementary to a unique sequence of the DNA encoding ribosomal RNA (rRNA) of Campylobacter jejuni for PCR were synthesized by solid-phase phosphoamidite method. Amplified target DNA of 275 base pairs could be resolved on ethidium bromide-stained gels, and hybridized with an oligodeoxynucleotide probe (28 mer) conjugated to alkaline phosphatase. In identification experiments, it was shown that the nonradioactive probe was hybridized to clinical strains of C. jejuni (104), C. coli (5), C. laridis (5), C. hyointestinalis (1) and C. fetus subsp. fetus (1) with an accuracy of 99-100%, while it was not for Helicobacter pylori. Further, there was no evidence of amplification in strains of K. pneumoniae, S. marcescens and E. coli. Using direct detection to stool specimens, this method could be performed in C. jejuni in 39 of 43 culture-positive specimens (91%), and in 19 of 141 culture-negative specimens (13.5%), respectively. The results of this comparative study suggested that the DNA probe assay became a rapid and reliable technique to confirm culture of Campylobacter species.     

Direct immunofluorescence microscopy for rapid screening of Campylobacter enteritis.

Diagnostic use of a direct fluorescent-antibody test for detection of Campylobacter jejuni and C. coli in human fecal specimens (n = 497) was compared with detection by culturing (specificity, 99.7%; sensitivity, 40%). Conjugates were prepared from immunoglobulin G antibody against 22 Lior C. jejuni and C. coli reference strains (H. Lior, D. L. Woodward, J. A. Edgar, L. J. Laroche, and P. Gill, J. Clin. Microbiol. 15:761-768, 1982). Interestingly, the serotypes of cultures tested by the direct fluorescent antibody test were different from those of cultures tested by Lior slide agglutination, although the antisera used were common to both test systems.     

Evaluation of a PCR/DNA Probe Colorimetric Membrane Assay for Identification of Campylobacter spp. in Human Stool Specimens

DNA was extracted from 50 human stool specimens using the QIAamp DNA stool minikit. PCR amplification was followed by post-PCR hybridization to DNA probes specific for the Campylobacter genus, Campylobacter jejuni, and Campylobacter coli in a colorimetric membrane assay. Thirty-two of 38 culture-positive specimens were PCR/DNA probe positive for C. jejuni. The assay is rapid and simple and can be applied to stool specimens for the detection of Campylobacter.     

Prevalence of virulence genes and cytolethal distending toxin production in Campylobacter jejuni isolates from diarrheal patients in Bangladesh

From 300 stool samples, 58 Campylobacter strains were isolated by standard microbiological and biochemical methods. Of these, 40 strains were identified as Campylobacter jejuni and 5 as Campylobacter coli. The presence of flaA (100%), cadF (100%), racR (100%), dnaJ (100%), pldA (100%), ciaB (95%), virB11 (0%), ceuE (82.5%), cdtA (97.5%), cdtB (97.5%), cdtC (97.5%), and wlaN (7.5%) genes was detected in C. jejuni by PCR. All C. jejuni strains but one produced cytolethal distending toxin in a HeLa cell assay.     

Murine intranasal challenge model for the study of Campylobacter pathogenesis and immunity.

Campylobacter jejuni infection of mice initiated by intranasal administration was investigated as a potential model for studies of pathogenesis and immunity. By using a standard challenge (5 x 10(9) CFU), C. jejuni 81-176 was more virulent for BALB/c (72% mortality) than for C3H/Hej (50%), CBA/CAJ (30%), or C58/J (0%). Intranasal challenge of BALB/c was used to compare the relative virulence of three reference strains; C.jejuni 81-176 was more virulent (killing 83% of challenged mice) than C. jejuni HC (0%) or C. coli VC-167 (0%). The course of intranasally initiated C. jejuni 81-176 infection in BALB/c was determined. C. jejuni was recovered from the lungs, intestinal tract, liver, and spleen at 4 h after challenge, the first interval evaluated. After this initial interval, three distinct patterns of infection were recognized: (i) a progressive decline in number of C. jejuni CFU (stomach, blood, lungs), (ii) decline followed by a second peak in the number of organisms recovered at 2 or 3 days postchallenge (intestine, liver, mesenteric lymph nodes), and (iii) persistence of approximately the same number of C.jejuni CFU during the course of the experiment (spleen). Intranasally induced infection initiated with a sublethal number of bacteria or intranasal immunization with killed Campylobacter preparations resulted in both the generation of Campylobacter antigen-specific immune responses and an acquired resistance to homologous rechallenge. The model was used to evaluate the relative virulence of nine low-in vitro-passage (no more than five passages) isolates of C. jejuni species from patients with diarrhea. The patient isolates were differentially virulent for mice; one killed all exposed mice, three were avirulent (no deaths) and the remainder showed an intermediate virulence, killing 17 to 33%. Mouse virulence of Campylobacter strains showed a trend toward isolates originating from individuals with watery diarrhea; however, no association was found between mouse virulence and other signs or symptoms. There were no observed relationships between mouse virulence and bacterial Lior serotype or Fla polymorphic group. Intranasal challenge of BALB/c with C. jejuni is a useful model for the study of infection and vaccination-acquired immunity to this agent.     

Correct identification and discrimination between Campylobacter jejuni and C. coli by a standardized hippurate test and species-specific polymerase chain reaction

Hippurate hydrolysis test results of 240 Campylobacter strains were compared with those of two multiplex polymerase chain reaction (PCR) assays. Of the 152 strains identified in Finnish clinical microbiology routine laboratories as C. coli (hippurate-negative), 11% were C. jejuni (hippurate-positive) by standardized hippurate test and 39% by PCR in the reference laboratory. Two of the 81 hippurate-positive strains were identified as C. coli. Standardizing the hippurate test by determining minimum and maximum turbidity limits (McFarland 6 and McFarland 10, OD(450) values 0.8 and 1.4, respectively) for the bacterial cell suspension eliminated the false-positive results, but 32% of the 145 hippurate-negative strains were still identified as C. jejuni by PCR. The species identification of Campylobacter isolates in Finland could be improved by using a standardized hippurate hydrolysis test to identify hippurate-positive C. jejuni and testing hippurate-negative strains by molecular methods. This would also improve the epidemiological data on this important zoonotic pathogen.     

Evaluation of culture methods and a DNA probe-based PCR assay for detection of Campylobacter species in clinical specimens of feces

Campylobacter species are the leading agents of bacterial gastroenteritis in developed countries. In this study 320 specimens of feces from patients with symptoms of acute gastroenteritis were cultured for Campylobacter species by direct plating on modified charcoal cefoperazone deoxycholate agar and by enrichment in modified Preston broth, with or without blood added, for 48 h at 37 degrees C prior to plating. A 16S/23S PCR/DNA probe membrane-based colorimetric detection assay was evaluated on a subset of the feces (n = 127), including 18 culture-positive and 109 culture-negative specimens. DNA was extracted directly from the fecal specimens by using the QIAamp DNA stool Minikit for the DNA probe-based PCR assay (PCR/DNA probe assay). A second PCR/DNA probe assay based on the 16S rRNA gene in Campylobacter spp. was applied to all specimens that were culture negative, PCR/DNA positive on initial analysis. Campylobacter species were cultured in 20 of the 320 specimens. The 16S/23S PCR/DNA probe assay detected campylobacter DNA in 17 of 18 (94% sensitivity) culture-positive specimens and in 41 (38%) culture-negative specimens. The presence of campylobacter DNA in 35 of 41 culture-negative specimens was confirmed by the 16S PCR/DNA probe assay. DNA sequence analysis of seven 16S/23S PCR products and five 16S PCR products amplified from a selection of these specimens confirmed the presence of campylobacter DNA and more specifically Campylobacter jejuni, C. concisus, C. curvus, and C. gracilis DNA in these specimens. The molecular assays described in this study are rapid methods for the detection and identification of Campylobacter species in fecal specimens. The finding of Campylobacter spp. DNA in a large number of specimens of feces from patients with no other identified cause of diarrhea may suggest that Campylobacter spp. other than C. jejuni and C. coli may account for a proportion of cases of acute gastroenteritis in which no etiological agent is currently identified.     

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.     

2010年广州某医疗中心儿童夏季细菌性腹泻的病原学调查

目的研究广州地区小儿夏季细菌性腹泻的病原菌分布。方法采集2010年5～7月广州市妇女儿童医疗中心珠江新城院区腹泻患儿的大便标本进行常规病原菌的分离培养,通过生化反应和血清凝集试验进行鉴定和分型,并使用金标法对空肠弯曲菌抗原进行检测。结果从110份标本中检出44株病原菌,检出率为40.0%。其中致病性大肠埃希菌17株,2岁以下患儿检出15株;空肠弯曲菌12株,2岁以下患儿检出10株;沙门菌6株;念珠菌纯生长6株;产气荚膜杆菌3株。结论广州地区夏季儿童细菌性腹泻的主要病原菌是致病性大肠埃希菌及空肠弯曲菌,两者的易感人群以2岁以下婴幼儿为主。     

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.