Antibiotic resistance in Campylobacter spp. isolated from human faeces (1980-2000) and foods (1997-2000) in Northern Ireland: an update

Prevalence and antibiotic resistance of Campylobacter spp. isolated from chicken meat, pork, and beef in Korea, from 2001 to 2006

A total of 770 samples of retail raw meat were examined for the presence of Campylobacter spp. The samples were obtained randomly from 232 retail stores in Korea from September 2001 to April 2006. The highest contamination rates were observed in chicken meat (220 181.4%] of 270 samples), whereas the rates of contamination in pork and beef were extremely low (1.6 and 1.2%, respectively). The antibiotic-resistant patterns of the 317 Campylobacter isolates were examined by the agar dilution method. Resistance to doxycycline was the most common (97.5%), followed by ciprofloxacin (95.9%), nalidixic acid (94.6%), tetracycline (94.6%), enrofloxacin (84.2%), and erythromycin (13.6%). All Campylobacter isolates from the retail raw meat were resistant to at least one of the six antibiotics tested, and 296 isolates (93.4%) showed multidrug (four or more antibiotics) resistance. This demonstrates that the multidrug-resistant Campylobacter species are widespread in meats in Korea. Therefore, further investigations will be needed to determine appropriate methods for eliminating Campylobacter contamination in industrial chicken production and food chains.

Antibiotic resistance of retail food and human Campylobacter isolates on the island of Ireland from 2001-2002

The antimicrobial resistance profiles of Campylobacter isolates recovered from a range of retail food samples (n=374) and humans (n=314) to eight antimicrobial compounds were investigated. High levels of resistance in food C. jejuni isolates were observed for ceftiofur (58%), ampicillin (25%) and nalidixic acid (17%) with lower levels observed for streptomycin (7.9%) and chloramphenicol (8.3%). A total of 80% of human C. jejuni isolates were resistant to ceftiofur, while 17% showed resistance to ampicillin and nalidixic acid, 8.6% to streptomycin and 4.1% to chloramphenicol. Resistance to clinically relevant antimicrobials such as erythromycin, ciprofloxacin and tetracycline was 6.7, 12, and 15% respectively for all food isolates and was similar to corresponding resistance prevalences observed for human isolates, where 6.4, 12 and 13% respectively were found to be resistant. Comparisons of C. jejuni isolates in each location showed a high degree of similarity although some regional variations did exist. Comparison of total C. jejuni and C. coli populations showed minor differences, with C. jejuni isolates more resistant to ampicillin and ceftiofur. Multidrug resistance patterns showed some profiles common to human and clinical isolates.

The epidemiology of antibiotic resistance in Campylobacter

Antibiotic resistance, particularly with the fluoroquinolones and macrolide antibiotics, has now emerged globally with thermophilic campylobacters, including Campylobacter jejuni and C. coli, giving rise to concerns about how these organisms have acquired such resistance characteristics, as well as consequences for human and animal treatment. This review examines (i) the clinical epidemiology of antibiotic resistance in human and animal thermophilic campylobacters, (ii) an update on resistance rates globally, (iii) surveillance of antimicrobial resistance in campylobacters originating from animals, particularly poultry, (iv) the role of the environment in the acquisition and transmission of antibiotic-resistant campylobacters, as well as (v) issues of biocide resistance in campylobacters.

Detection of mutations associated with macrolide resistance in thermophilic Campylobacter spp. by real-time PCR

Two point mutations (A2074C and A2075G) in the 23S rRNA gene of Campylobacter coli and C. jejuni are associated with erythromycin resistance. A real-time fluorescence resonance energy transfer PCR assay using a melting curve analysis was developed to identify these two point mutations and the wild-type genotype in thermophilic Campylobacter species such as C. coli, C. jejuni, and C. lari. Concerning these species, 141 strains were tested and a result obtained in 140 (99.3%). A single genotype was detected in 133 cases and two genotypes in seven cases. There was an agreement with the phenotypic methods except for one C. coli strain that was not amplified during the PCR assay. The A2075G mutation was mainly found among the 92 resistant strains tested (95.6%) and the A2074C mutation only twice (2.2%). One C. jejuni strain (1.1%) harbored both mutations on the same 23S rDNA copy. When compared to the phenotypic tests, the new real-time PCR assay was able to detect the correct genotype, in all cases except one (1.1%). This assay is more sensitive and more rapid than other PCR assays, the entire procedure taking less than 2 hr.

Prevalence and subtypes of ciprofloxacin-resistant Campylobacter spp. in commercial poultry flocks before, during, and after treatment with fluoroquinolones

Five commercial broiler chicken flocks were treated with either difloxacin or enrofloxacin for a clinically relevant infection, as instructed by a veterinarian. Campylobacters were isolated from individual fecal samples and from samples associated with the broiler environment before, during, and after treatment. Ciprofloxacin-resistant Campylobacter jejuni and/or C. coli strains were detected pretreatment in four flocks, but they constituted a very small proportion of the campylobacters present. When the broilers were treated with a fluoroquinolone, a rapid increase in the proportion of ciprofloxacin-resistant campylobacters was observed. During treatment nearly 100% of campylobacters were resistant, and in some flocks a high proportion of resistant strains persisted for up to 4 weeks after treatment. Prior to treatment a variety of campylobacter subtypes were present. During and after treatment considerable changes in both species and subtype prevalence were observed, but no single fluoroquinolone-resistant clone became dominant. Instead, resistant C. coli strains or a mixture of resistant C. coli and C. jejuni strains became dominant, whereas susceptible C. jejuni strains had usually been dominant prior to treatment. The resistant subtypes which emerged and became dominant were not always the same as those detected pretreatment. The persistence of resistant strains for up to 4 weeks posttreatment has important implications for any strategy designed to avoid the introduction of such strains into the food chain.

Diagnosis and treatment of bacterial diarrhea

Diarrheal illness caused by bacterial pathogens is a global health problem and remains one of the most common complaints prompting patients to seek medical care. Strategies to increase the yield of stool culture and new rapid diagnostic tests can improve diagnostic ability. Emerging antimicrobial resistance among the common bacterial causes of diarrhea has made treatment more challenging. Emerging fluoroquinolone resistance is a particular concern. Recent studies of rifaximin, a nonabsorbed antibiotic for the treatment of bacterial diarrhea, have shown favorable results. Rifaximin may represent a much-needed addition to the armamentarium against bacterial agents.

Selection and characterization of fluoroquinolone-resistant mutants of Campylobacter jejuni using enrofloxacin

Significant levels of fluoroquinolone resistance were obtained in Campylobacterjejuni isolates after an unique step of selection using enrofloxacin. An Asp90-to-Asn and a Thr86-to-Ile change in the gyrase subunit GyrA were found associated with a low (MIC < or = 8 /microg/ml) or a high (MIC > or = 16 microg/ml) level of resistance to ciprofloxacin, respectively. An association of both mutations conferred a higher level of resistance (MIC > or = 128 microg/ml). Further steps of selection increased the MICs of fluoroquinolones but did not result in a multiple antibiotic resistance phenotype. The Thr86-to-Ile change was found to confer different levels of resistance, pointing out other mechanisms of resistance. However, sequencing revealed no mutation in gyrB, and several attempts did not enable any amplification of the parC gene coding for topoisomerase IV, suggesting an absence of this secondary target in C. jejuni. In addition, no difference in the major outer membrane protein expression was found among the isolates. Furthermore, the use of the recently identified efflux pump inhibitor Phe-Arg-beta-naphthylamide did not result in a significant decrease of fluoroquinolone MICs or change in the frequency of isolation of enrofloxacin-resistant mutants, and thus appears ineffective against fluoroquinolone-resistant C. jejuni isolates. Results obtained during ciprofloxacin accumulation studies confirmed that efflux probably plays a minor role in fluoroquinolone resistance of C. jejuni.

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

AIMS

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

METHODS AND RESULTS

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

CONCLUSIONS

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

SIGNIFICANCE AND IMPACT OF THE STUDY

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

Phenotypic and genotypic relationship between Campylobacter spp isolated from humans and chickens in Northern Ireland--a comparison of three phenotyping and two genotyping schemes

Human campylobacteriosis is currently the most common cause of acute bacterial gastroenteritis on the island of Ireland, accounting for over 3,000 laboratory reports per year, where circa 2,000 reports originate from the Republic of Ireland and circa 1,000 reports from Northern Ireland. Elsewhere, consumption of contaminated poultry has been associated with the zoonotic transmission of disease, therefore it was the aim of this study to examine the phenotypic and genotypic relatedness of campylobacters isolated from chickens and humans locally. Sixty isolates were subtyped using phenotyping techniques (biotyping, phage-typing), as well as genotyping techniques (multilocus enzyme electrophoresis (MEE), ribotyping) and the data compared. The frequency of shared phenotypes and genotypes between poultry and humans varied depending on the typing technique employed ranging from 98.2% of human isolates sharing a similar resistotyping (MAST) disc type with poultry strains to 20% similarity with MEE typing. Overall, this small study is the first report on phenotypic and genotypic relatedness between human and poultry campylobacters in Northern Ireland, isolated under controlled conditions. The study demonstrated an association between chicken and human sub-species types, taken from a relatively contained epidemiological environment. Further work is required with larger numbers of isolates coupled with typing schemes, which are able to reliably cluster strains from chicken and humans, which share high degrees of clonality, before local poultry can be conclusively proven to be a significant source of human campylobacteriosis.

Antimicrobial-resistant Campylobacter species from retail raw meats

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

PCR-restriction fragment length polymorphism analysis for detection of point mutations associated with macrolide resistance in Campylobacter spp

A 23S rRNA gene fragment in domain V was sequenced from 30 clinical isolates of Campylobacter spp., including 22 resistant to macrolides. Two point mutations associated with erythromycin resistance were identified at positions 2074 and 2075 on the 23S rRNA gene (homologous to A2142C and A2143G mutations in Helicobacter pylori) in which an adenine residue is also replaced with a cytosine and a guanine residue, respectively. A combined PCR-restriction fragment length polymorphism technique was developed to detect these mutations by using the BsaI and BceAI enzymes.

gyrA polymorphism in Campylobacter jejuni: detection of gyrA mutations in 162 C. jejuni isolates by single-strand conformation polymorphism and DNA sequencing

Mutations in the quinolone resistance-determining region of the gyrA gene from 138 ciprofloxacin-resistant (MIC, > or =4 microg/ml) and 24 ciprofloxacin-susceptible (MIC, < or =1 microg/ml) clinical Campylobacter jejuni isolates were subjected to single-strand conformation polymorphism analysis and sequencing. All of the isolates could be assigned to three genotypic clusters based on silent mutations. All resistant isolates had a point mutation at codon 86.

Phenotyping of Campylobacter jejuni and Campylobacter coli by a quantitative antibiogram [MIC] typing scheme using Euclidean distances [QATED]

BACKGROUND

Enteropathogenic Campylobacter jejuni and C. coli are presently the most common cause of acute bacterial gastroenteritis in the developed world. An understanding of sources and means of transmission of Campylobacter is an essential factor in order to reduce the incidence of Campylobacter-related gastroenteritis in man. Consequently a reproducible, sensitive and well-standardised typing scheme is critical in the successful discrimination of strains and in the subsequent investigations of outbreaks. For this purpose, a phenotypic typing scheme based on quantitative antibiogram determination based on Euclidean distance (QATED), was developed.

RESULTS AND CONCLUSION

The results obtained with this typing scheme demonstrated that individual livers of colonized pigs could be infected with multiple strains of Campylobacter spp. and subspecies types. In conclusion, phenotyping of Campylobacter jejuni and C. coli by QATED is a simple, inexpensive and discriminatory sub-species characterisation scheme, which may be useful in primary diagnostic clinical laboratories, where no specialist Campylobacter phenotyping or molecular genotyping schemes exist. It is especially suitable for food-borne outbreak investigations in the community, where a rapid and local response is required to aid with public health epidemiological investigations.