Antibiotic resistance and resistance mechanisms inCampylobacter jejuniandCampylobacter coli

Identification of a novel G2073A mutation in 23S rRNA in amphenicol-selected mutants of Campylobacter jejuni

OBJECTIVES

This study was conducted to examine the development and molecular mechanisms of amphenicol resistance in Campylobacter jejuni by using in vitro selection with chloramphenicol and florfenicol. The impact of the resistance development on growth rates was also determined using in vitro culture.

METHODS

Chloramphenicol and florfenicol were used as selection agents to perform in vitro stepwise selection. Mutants resistant to the selective agents were obtained from the selection process. The mutant strains were compared with the parent strain for changes in MICs and growth rates. The 23S rRNA gene and the L4 and L22 ribosomal protein genes in the mutant strains and the parent strain were amplified and sequenced to identify potential resistance-associated mutations.

RESULTS

C. jejuni strains that were highly resistant to chloramphenicol and florfenicol were obtained from in vitro selection. A novel G2073A mutation in all three copies of the 23S rRNA gene was identified in all the resistant mutants examined, which showed resistance to both chloramphenicol and florfenicol. In addition, all the mutants selected by chloramphenicol also exhibited the G74D modification in ribosomal protein L4, which was previously shown to confer a low-level erythromycin resistance in Campylobacter species. The mutants selected by florfenicol did not have the G74D mutation in L4. Notably, the amphenicol-resistant mutants also exhibited reduced susceptibility to erythromycin, suggesting that the selection resulted in cross resistance to macrolides.

CONCLUSIONS

This study identifies a novel point mutation (G2073A) in 23S rRNA in amphenicol-selected mutants of C. jejuni. Development of amphenicol resistance in Campylobacter likely incurs a fitness cost as the mutant strains showed slower growth rates in antibiotic-free media.

Macrolides and lincosamides in cattle and pigs: use and development of antimicrobial resistance

Macrolides and lincosamides are important antibacterials for the treatment of many common infections in cattle and pigs. Products for in-feed medication with these compounds in combination with other antimicrobials are commonly used in Europe. Most recently approved injectable macrolides have very long elimination half-lives in both pigs and cattle, which allows once-only dosing regimens. Both in-feed medication and use of long-acting injections result in low concentrations of the active substance for prolonged periods, which causes concerns related to development of antimicrobial resistance. Acquired resistance to macrolides and lincosamides among food animal pathogens, including some zoonotic bacteria, has now emerged. A comparison of studies on the prevalence of resistance is difficult, since for many micro-organisms no agreed standards for susceptibility testing are available. With animal pathogens, the most dramatic increase in resistance has been seen in the genus Brachyspira. Resistance towards macrolides and lincosamides has also been detected in staphylococci isolated from pigs and streptococci from cattle. This article reviews the use of macrolides and lincosamides in cattle and pigs, as well as the development of resistance in target and some zoonotic pathogens. The focus of the review is on European conditions.

Pentavalent single-domain antibodies reduce Campylobacter jejuni motility and colonization in chickens

Campylobacter jejuni is the leading cause of bacterial foodborne illness in the world, with symptoms ranging from acute diarrhea to severe neurological disorders. Contaminated poultry meat is a major source of C. jejuni infection, and therefore, strategies to reduce this organism in poultry, are expected to reduce the incidence of Campylobacter-associated diseases. We have investigated whether oral administration of C. jejuni-specific single-domain antibodies would reduce bacterial colonization levels in chickens. Llama single-domain antibodies specific for C. jejuni were isolated from a phage display library generated from the heavy chain IgG variable domain repertoire of a llama immunized with C. jejuni flagella. Two flagella-specific single-domain antibodies were pentamerized to yield high avidity antibodies capable of multivalent binding to the target antigen. When administered orally to C. jejuni-infected two-day old chicks, the pentabodies significantly reduced C. jejuni colonization in the ceca. In vitro, the motility of the bacteria was also reduced in the presence of the flagella-specific pentabodies, suggesting the mechanism of action is through either direct interference with flagellar motility or antibody-mediated aggregation. Fluorescent microscopy and Western blot analyses revealed specific binding of the anti-flagella pentabodies to the C. jejuni flagellin.

Report of ribosomal RNA methylase gene erm(B) in multidrug-resistant Campylobacter coli

OBJECTIVES

Campylobacter is a major foodborne enteric pathogen and macrolides are the drug of choice for the clinical therapy of campylobacteriosis. Macrolide resistance among Campylobacter compromises clinical treatment, is associated with adverse health events and is a significant public health concern. Here, we report the first identification of a horizontally transferrable macrolide resistance mechanism in porcine Campylobacter coli ZC113 that is mediated by a ribosomal RNA methylase, Erm(B).

METHODS

Horizontal transfer of a macrolide resistance determinant between C. coli and Campylobacter jejuni was performed by natural transformation. Whole-genome sequencing was initially used to identify the ribosomal methylase-encoding gene erm(B) in Campylobacter. Cloning of erm(B) into C. jejuni NCTC 11168 was performed to evaluate whether the erm(B) gene is responsible for high-level macrolide resistance in Campylobacter.

RESULTS

The erm(B) gene was identified in ZC113, conferred high-level resistance to macrolides and was associated with a chromosomal multidrug-resistant genomic island (MDRGI). The MDRGI probably originated from Gram-positive bacteria and was horizontally transferred between C. coli and C. jejuni via natural transformation. Furthermore, the erm(B)-positive isolate ZC113 was resistant to all clinically important antibiotics used for treating campylobacteriosis and is essentially multidrug-resistant Campylobacter.

CONCLUSIONS

To the best of our knowledge, this is the first report of a horizontally transferable macrolide resistance mechanism in thermophilic Campylobacter. Surveillance of erm(B) and its associated MDRGI in both C. coli and C. jejuni is urgently warranted.

Foodborne Campylobacter: infections, metabolism, pathogenesis and reservoirs

Campylobacter species are a leading cause of bacterial-derived foodborne illnesses worldwide. The emergence of this bacterial group as a significant causative agent of human disease and their propensity to carry antibiotic resistance elements that allows them to resist antibacterial therapy make them a serious public health threat. Campylobacter jejuni and Campylobacter coli are considered to be the most important enteropathogens of this genus and their ability to colonize and survive in a wide variety of animal species and habitats make them extremely difficult to control. This article reviews the historical and emerging importance of this bacterial group and addresses aspects of the human infections they cause, their metabolism and pathogenesis, and their natural reservoirs in order to address the need for appropriate food safety regulations and interventions.

Source attribution of human Campylobacter isolates by MLST and fla-typing and association of genotypes with quinolone resistance

Campylobacteriosis is the most frequent zoonosis in developed countries and various domestic animals can function as reservoir for the main pathogens Campylobacter jejuni and Campylobacter coli. In the present study we compared population structures of 730 C. jejuni and C. coli from human cases, 610 chicken, 159 dog, 360 pig and 23 cattle isolates collected between 2001 and 2012 in Switzerland. All isolates had been typed with multi locus sequence typing (MLST) and flaB-typing and their genotypic resistance to quinolones was determined. We used complementary approaches by testing for differences between isolates from different hosts with the proportion similarity as well as the fixation index and by attributing the source of the human isolates with Bayesian assignment using the software STRUCTURE. Analyses were done with MLST and flaB data in parallel and both typing methods were tested for associations of genotypes with quinolone resistance. Results obtained with MLST and flaB data corresponded remarkably well, both indicating chickens as the main source for human infection for both Campylobacter species. Based on MLST, 70.9% of the human cases were attributed to chickens, 19.3% to cattle, 8.6% to dogs and 1.2% to pigs. Furthermore we found a host independent association between sequence type (ST) and quinolone resistance. The most notable were ST-45, all isolates of which were susceptible, while for ST-464 all were resistant.

Genotypes and antibiotic resistance of canine Campylobacter jejuni isolates

Campylobacter jejuni is the most important cause of bacterial gastroenteritis in humans. It is a commensal in many wild and domestic animals, including dogs. Whereas genotypes of human and chicken C. jejuni isolates have been described in some detail, only little information on canine C. jejuni genotypes is available. To gain more information on genotypes of canine C. jejuni and their zoonotic potential, isolates from routine diagnostics of diarrheic dogs as well as isolates of a prevalence study in non-diarrheic dogs were analyzed. Prevalence of thermophilic Campylobacter among non-diarrheic dogs was 6.3% for C. jejuni, 5.9% for Campylobacter upsaliensis and 0.7% for Campylobacter coli. The C. jejuni isolates were genotyped by multi locus sequence typing (MLST) and flaB typing. Resistance to macrolides and quinolones was genetically determined in parallel. Within the 134 genotyped C. jejuni isolates 57 different sequence types (ST) were found. Five STs were previously unrecognized. The most common STs were ST-48 (11.2%), ST-45 (10.5%) and ST-21 (6.0%). Whereas no macrolide resistance was found, 28 isolates (20.9%) were resistant to quinolones. ST-45 was significantly more prevalent in diarrheic than in non-diarrheic dogs. Within the common time frame of isolation 94% of the canine isolates had a ST that was also found in human clinical isolates. In conclusion, prevalence of C. jejuni in Swiss dogs is low but there is a large genetic overlap between dog and human isolates. Given the close contact between human and dogs, the latter should not be ignored as a potential source of human campylobacteriosis.

Prevalence and antimicrobial resistance of Campylobacter spp. isolated from poultry carcasses in Poland

The purpose of the present study was to determine the prevalence of Campylobacter in poultry carcasses at slaughter in Poland. For the isolated strains, resistance to selected antibiotics and the associated genetic determinants were identified. A total of 498 Campylobacter isolates were obtained from 802 poultry samples during the 2-year study period. Strains were identified to species with the PCR method; 53.6% of the strains were Campylobacter jejuni and 46.4% were Campylobacter coli. A high percentage of the tested Campylobacter strains were resistant to ciprofloxacin and nalidixic acid (74.1 and 73.5%, respectively) followed by tetracycline (47.4%) and streptomycin (20.5%). Only one C. jejuni and two C. coli isolates were resistant to gentamicin. Seventy-nine (15.9%) of the 498 strains were resistant to three or more classes of antibiotics examined. Higher levels of resistance, irrespective of the antimicrobial agent tested, were found within the C. coli group. Almost all strains resistant to quinolones (99.5%) and to tetracycline (99.6%) carried the Thr-86-to-Ile mutation in the gyrA gene and possessed the tet(O) marker, respectively. All isolates resistant to erythromycin had the A2075G mutation in the 23S rRNA gene. These results reveal that poultry carcasses in Poland are a reservoir of potentially pathogenic and antimicrobial-resistant Campylobacter strains for humans, which may pose a public health risk.

Antimicrobial resistance in campylobacter: susceptibility testing methods and resistance trends

Most Campylobacter infections are self-limiting but antimicrobial treatment (e.g., macrolides, fluoroquinolones) is necessary in severe or prolonged cases. Susceptibility testing continues to play a critical role in guiding therapy and epidemiological monitoring of resistance. The methods of choice for Campylobacter recommended by the Clinical and Laboratory Standards Institute (CLSI) are agar dilution and broth microdilution, while a disk diffusion method was recently standardized by the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Macrolides, quinolones, and tetracyclines are among the common antimicrobials recommended for testing. Molecular determination of Campylobacter resistance via DNA sequencing or PCR-based methods has been performed. High levels of resistance to tetracycline and ciprofloxacin are frequently reported by many national surveillance programs, but resistance to erythromycin and gentamicin in Campylobacter jejuni remains low. Nonetheless, variations in susceptibility observed over time underscore the need for continued public health monitoring of Campylobacter resistance from humans, animals, and food.

High-resolution transcriptome maps reveal strain-specific regulatory features of multiple Campylobacter jejuni isolates

Campylobacter jejuni is currently the leading cause of bacterial gastroenteritis in humans. Comparison of multiple Campylobacter strains revealed a high genetic and phenotypic diversity. However, little is known about differences in transcriptome organization, gene expression, and small RNA (sRNA) repertoires. Here we present the first comparative primary transcriptome analysis based on the differential RNA-seq (dRNA-seq) of four C. jejuni isolates. Our approach includes a novel, generic method for the automated annotation of transcriptional start sites (TSS), which allowed us to provide genome-wide promoter maps in the analyzed strains. These global TSS maps are refined through the integration of a SuperGenome approach that allows for a comparative TSS annotation by mapping RNA-seq data of multiple strains into a common coordinate system derived from a whole-genome alignment. Considering the steadily increasing amount of RNA-seq studies, our automated TSS annotation will not only facilitate transcriptome annotation for a wider range of pro- and eukaryotes but can also be adapted for the analysis among different growth or stress conditions. Our comparative dRNA-seq analysis revealed conservation of most TSS, but also single-nucleotide-polymorphisms (SNP) in promoter regions, which lead to strain-specific transcriptional output. Furthermore, we identified strain-specific sRNA repertoires that could contribute to differential gene regulation among strains. In addition, we identified a novel minimal CRISPR-system in Campylobacter of the type-II CRISPR subtype, which relies on the host factor RNase III and a trans-encoded sRNA for maturation of crRNAs. This minimal system of Campylobacter, which seems active in only some strains, employs a unique maturation pathway, since the crRNAs are transcribed from individual promoters in the upstream repeats and thereby minimize the requirements for the maturation machinery. Overall, our study provides new insights into strain-specific transcriptome organization and sRNAs, and reveals genes that could modulate phenotypic variation among strains despite high conservation at the DNA level.

Distribution of colonization and antimicrobial resistance genes in Campylobacter jejuni isolated from chicken

Campylobacter jejuni is an important worldwide foodborne pathogen commonly found as a commensal organism in poultry that can reach high numbers within the gut after colonization. Although information regarding some genes involved in colonization is available, little is known about their distribution in strains isolated specifically from chickens and whether there is a linkage between antimicrobial resistance (AMR) and colonization genes. To assess the distribution and relevance of genes associated with chicken colonization and AMR, a C. jejuni microarray was created to detect 254 genes of interest in colonization and AMR including variants. DNA derived from chicken-specific Campylobacter isolates collected in 2003 (n=29) and 2008 (n=28) was hybridized to the microarray and compared. Hybridization results showed variable colonization-associated gene presence. Acquired AMR genes were low in prevalence whereas chemotaxis receptors, arsenic resistance genes, as well as genes from the cell envelope and flagella functional groups were highly variable in their presence. Strains clustered into two groups, each linked to different control strains, 81116 and NCTC11168. Clustering was found to be independent of collection time. We also show that AMR weakly associated with the CJ0628 and arsR genes. Although other studies have implicated numerous genes associated with C. jejuni chicken colonization, our data on chicken-specific isolates suggest the opposite. The enormous variability in presumed colonization gene prevalence in our chicken isolates suggests that many are of lesser importance than previously thought. Alternatively, this also suggests that combinations of genes may be required for natural colonization of chicken intestines.

In vitro characterization of aggregation and adhesion properties of viable and heat-killed forms of two probiotic Lactobacillus strains and interaction with foodborne zoonotic bacteria, especially Campylobacter jejuni

Bacterial aggregation and/or adhesion are key factors for colonization of the digestive ecosystem and the ability of probiotic strains to exclude pathogens. In the present study, two probiotic strains, Lactobacillus rhamnosus CNCM-I-3698 and Lactobacillus farciminis CNCM-I-3699, were evaluated as viable or heat-killed forms and compared with probiotic reference Lactobacillus strains (Lb. rhamnosus GG and Lb. farciminis CIP 103136). The autoaggregation potential of both forms was higher than that of reference strains and twice that of pathogenic strains. The coaggregation potential of these two beneficial micro-organisms was evaluated against several pathogenic agents that threaten the global safety of the feed/food chain: Escherichia coli, Salmonella spp., Campylobacter spp. and Listeria monocytogenes. The strongest coaggregative interactions were demonstrated with Campylobacter spp. by a coaggregation test, confirmed by electron microscopic examination for the two forms. Viable forms were investigated for the nature of the bacterial cell-surface molecules involved, by sugar reversal tests and chemical and enzymic pretreatments. The results suggest that the coaggregation between both probiotic strains and C. jejuni CIP 70.2(T) is mediated by a carbohydrate-lectin interaction. The autoaggregation potential of the two probiotics decreased upon exposure to proteinase, SDS or LiCl, showing that proteinaceous components on the surface of the two lactobacilli play an important role in this interaction. Adhesion abilities of both Lactobacillus strains were also demonstrated at significant levels on Caco-2 cells, mucin and extracellular matrix material. Both viable and heat-killed forms of the two probiotic lactobacilli inhibited the attachment of C. jejuni CIP 70.2(T) to mucin. In conclusion, in vitro assays showed that Lb. rhamnosus CNCM-I-3698 and Lb. farciminis CNCM-I-3699, as viable or heat-killed forms, are adherent to different intestinal matrix models and are highly aggregative in vitro with pathogens, especially Campylobacter spp., the most commonly reported zoonotic agent in the European Union. This study supports the need for further in vivo investigations to demonstrate the potential food safety benefits of Lb. rhamnosus CNCM-I-3698 and Lb. farciminis CNCM-I-3699, live or heat-killed, in the global feed/food chain.

Resistance to bile salts and sodium deoxycholate in macrolide- and fluoroquinolone-susceptible and resistant Campylobacter jejuni and Campylobacter coli strains

Campylobacter are the most commonly reported bacterial causes of human gastroenteritis, and they are becoming increasingly resistant to antibiotics, including macrolides and fluoroquinolones, those most frequently used for the treatment of campylobacteriosis. Active efflux mechanisms are involved in resistance of Campylobacter to a broad spectrum of antimicrobials, and are also essential for Campylobacter colonization in the animal intestine, through mediation of bile resistance. Acquisition of antibiotic resistance through resistance-conferring mutations can impose a fitness cost of Campylobacter. The aim of the present study was to determine whether macrolide and fluoroquinolone resistance in Campylobacter affects their tolerance to bile salts and sodium deoxycholate through the most frequent resistance-conferring mutations. Antimicrobial efflux was studied on the basis of restored sensitivity in the presence of the efflux-pump inhibitors (EPIs) phenylalanine-arginine beta-naphthylamide (PAβN) and 1-(1-naphthylmethyl)-piperazine. In the 15 Campylobacter jejuni and 23 Campylobacter coli strains examined here, both of these EPIs partially reversed the resistance to bile salts and sodium deoxycholate. Erythromycin-sensitive C. coli strains were more resistant to bile salts and sodium deoxycholate than erythromycin-resistant strains. PAβN had greater effects on bile salt and sodium deoxycholate resistance in these erythromycin-resistant strains compared to erythromycin-sensitive strains. However, no differences were seen between the ciprofloxacin-sensitive and ciprofloxacin-resistant strains.

Comparative characterization of the virulence gene clusters (lipooligosaccharide [LOS] and capsular polysaccharide [CPS]) for Campylobacter coli, Campylobacter jejuni subsp. jejuni and related Campylobacter species

Campylobacter jejuni subsp. jejuni and Campylobacter coli are leading causes of gastroenteritis, with virulence linked to cell surface carbohydrate diversity. Although the associated gene clusters are well studied for C. jejuni subsp. jejuni, C. coli has been largely neglected. Here we provide comparative analysis of the lipooligosaccharide (LOS) and capsular polysaccharide (CPS) gene clusters, using genome and cluster sequence data for 36 C. coli strains, 67 C. jejuni subsp. jejuni strains and ten additional Campylobacter species. Similar to C. jejuni subsp. jejuni, C. coli showed high LOS/CPS gene diversity, with each cluster delineated into eight gene content classes. This diversity was predominantly due to extensive gene gain/loss, with the lateral transfer of genes likely occurring both within and between species and also between the LOS and CPS. Additional mechanisms responsible for LOS/CPS diversity included phase-variable homopolymeric repeats, gene duplication/inactivation, and possibly host environment selection pressure. Analyses also showed that (i) strains of C. coli and Campylobacter upsaliensis possessed genes homologous to the sialic acid genes implicated in the neurological disorder Guillain-Barré syndrome (GBS), and (ii) C. coli LOS classes were differentiated between bovine and poultry hosts, potentially aiding post infection source tracking.

Prevalence and Antimicrobial Resistance of Thermophilic Campylobacter Isolated from Chicken in Côte d'Ivoire

Thermophilic Campylobacters are major causes of gastroenteritis in human. The main risk factor of infection is consumption of contaminated or by cross-contaminated poultry meat. In Côte d'Ivoire, gastroenteritis is usually observed but no case of human campylobacteriosis has been formally reported to date. The aims of this study were to determine prevalence and antimicrobial resistance of Campylobacter jejuni and Campylobacter coli isolated from chickens ceaca in commercial slaughter in Abidjan. Between May and November 2009, one hundred and nineteen (119) chicken caeca samples were collected and analyzed by passive filtration method followed by molecular identification (PCR). From these 119 samples, 76 (63.8%) were positive to Campylobacter tests. Among the positive colonies, 51.3% were C. jejuni and 48.7% were C. coli. Of the 39 C. jejuni isolates, 79.5%, 38.5%, 17.9%, 10.3%, and 7.7% were, respectively, resistant, to nalidixic acid, ciprofloxacin, amoxicillin, erythromycin, and gentamicin. Among the 37 isolates of C. coli, 78.4%, 43.2%, 13.5%, 8.1%, and 0% were resistant, respectively, to the same antibiotics. In conclusion, we reported in this study the presence of high Campylobacter contamination of the studied chickens. Molecular identification of the bacteria was performed and determination of high resistance to antimicrobials of the fluoroquinolone family was revealed.

Chromosomal tet(O)-harboring regions in Campylobacter coli isolates from turkeys and swine

In turkey-derived Campylobacter coli isolates of a unique lineage (cluster II), the tetracycline resistance determinant tet(O) was chromosomal and was part of a gene cassette (transposon) interrupting a Campylobacter jejuni-associated putative citrate transporter gene. In contrast, the swine-derived C. coli strain 6461 harbored a chromosomal tet(O) in a different genomic location.

Identification of a novel genomic island conferring resistance to multiple aminoglycoside antibiotics in Campylobacter coli

Historically, the incidence of gentamicin resistance in Campylobacter has been very low, but recent studies reported a high prevalence of gentamicin-resistant Campylobacter isolated from food-producing animals in China. The reason for the high prevalence was unknown and was addressed in this study. PCR screening identified aminoglycoside resistance genes aphA-3 and aphA-7 and the aadE-sat4-aphA-3 cluster among 41 Campylobacter isolates from broiler chickens. Importantly, a novel genomic island carrying multiple aminoglycoside resistance genes was identified in 26 aminoglycoside resistant Campylobacter coli strains. Sequence analysis revealed that the genomic island was inserted between cadF and COO1582 on the C. coli chromosome and consists of 14 open reading frames (ORFs), including 6 genes (the aadE-sat4-aphA-3 cluster, aacA-aphD, aac, and aadE) encoding aminoglycoside-modifying enzymes. Analysis by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing indicated that the C. coli isolates carrying this unique genomic island were clonal, and the clone of PFGE subtype III and sequence type (ST) 1625 was particularly predominant among the C. coli isolates examined, suggesting that clonal expansion may be involved in dissemination of this resistance island. Additionally, we were able to transfer this genomic island from C. coli to a Campylobacter jejuni strain using natural transformation under laboratory conditions, and the transfer resulted in a drastic increase in aminoglycoside resistance in the recipient strain. These findings identify a previously undescribed genomic island that confers resistance to multiple aminoglycoside antibiotics. Since aminoglycoside antibiotics are used for treating occasional systemic infections caused by Campylobacter, the emergence and spread of this antibiotic resistance genomic island represent a potential concern for public health.

Examination of nanoparticle inactivation of Campylobacter jejuni biofilms using infrared and Raman spectroscopies

AIMS

To investigate inactivation effect and mechanism of zinc oxide nanoparticles (ZnO NPs) activity against Campylobacter jejuni biofilms.

METHODS AND RESULTS

ZnO NPs with concentrations of 0, 0·6, 1·2 and 6 mmol l(-1) were employed in antimicrobial tests against Camp. jejuni planktonic cells and biofilms. Campylobacter jejuni sessile cells in biofilms were more resistant to a low concentration of ZnO NPs when compared to planktonic cells. The ZnO NPs penetrated the extracellular polymeric substance (EPS) without damage to the EPS and directly interacted with the sessile bacterial cells, as determined using infrared spectroscopy and scanning electron microscopy. Raman spectroscopy shows alterations in quinone structures and damage to nucleic acids following Camp. jejuni treatment with ZnO NPs. The mechanism of DNA damage is most likely due to the generation of reactive oxygen species (ROS). Spectroscopic-based partial least squares regression (PLSR) models could predict the number of surviving sessile cell numbers within a bacterial biofilm (≥log 4 CFU, root mean square error of estimation <0·36) from Fourier transform infrared (FT-IR) spectral measurements.

CONCLUSIONS

ZnO NPs were found to have antimicrobial activity against Camp. jejuni biofilms. ZnO NPs penetrated the biofilm EPS within 1 h without damaging it and interacted directly with sessile cells in biofilms. Alterations in the DNA/RNA bases, which are owing to the generation of ROS, appear to result in Camp. jejuni cell death.

SIGNIFICANCE AND IMPACT OF THE STUDY

ZnO NPs may offer a realistic strategy to eliminate Camp. jejuni biofilms in the environment.

Antimicrobial resistance of emerging foodborne pathogens: status quo and global trends

Emerging foodborne pathogens are challenging subjects of food microbiology with their antibiotic resistance and their impact on public health. Campylobacter jejuni, Salmonella spp. and Verotoxigenic Escherichia coli (VTEC) are significant emerging food pathogens, globally. The decrease in supply and increase in demand lead developed countries to produce animal products with a higher efficiency. The massive production has caused the increase of the significant foodborne diseases. The strict control of food starting from farm to fork has been held by different regulations. Official measures have been applied to combat these pathogens. In 2005 EU declared that, an EU-wide ban on the use of antibiotics as growth promoters in animal feed would be applied on 1 January 2006. The ban is the final step in the phasing out of antibiotics used for non-medical purposes. It is a part of the Commission's strategy to tackle the emergence of bacteria and other microbes resistant to antibiotics, due to their overexploitation or misuse. As the awareness raises more countries banned application of antibiotics as growth promoter, but the resistance of the emerging foodborne pathogens do not represent decrease. Currently, the main concern of food safety is counter measures against resistant bugs.

FdhTU-modulated formate dehydrogenase expression and electron donor availability enhance recovery of Campylobacter jejuni following host cell infection

Campylobacter jejuni is a food-borne bacterial pathogen that colonizes the intestinal tract and causes severe gastroenteritis. Interaction with host epithelial cells is thought to enhance severity of disease, and the ability of C. jejuni to modulate its metabolism in different in vivo and environmental niches contributes to its success as a pathogen. A C. jejuni operon comprising two genes that we designated fdhT (CJJ81176_1492) and fdhU (CJJ81176_1493) is conserved in many bacterial species. Deletion of fdhT or fdhU in C. jejuni resulted in apparent defects in adherence and/or invasion of Caco-2 epithelial cells when assessed by CFU enumeration on standard Mueller-Hinton agar. However, fluorescence microscopy indicated that each mutant invaded cells at wild-type levels, instead suggesting roles for FdhTU in either intracellular survival or postinvasion recovery. The loss of fdhU caused reduced mRNA levels of formate dehydrogenase (FDH) genes and a severe defect in FDH activity. Cell infection phenotypes of a mutant deleted for the FdhA subunit of FDH and an ΔfdhU ΔfdhA double mutant were similar to those of a ΔfdhU mutant, which likewise suggested that FdhU and FdhA function in the same pathway. Cell infection assays followed by CFU enumeration on plates supplemented with sodium sulfite abolished the ΔfdhU and ΔfdhA mutant defects and resulted in significantly enhanced recovery of all strains, including wild type, at the invasion and intracellular survival time points. Collectively, our data indicate that FdhTU and FDH are required for optimal recovery following cell infection and suggest that C. jejuni alters its metabolic potential in the intracellular environment.

Prevalence, quantification and antimicrobial resistance of Campylobacter spp. on chicken neck-skins at points of slaughter in 5 major cities located on 4 continents

Quantitative data on Campylobacter contamination of food are lacking, notably in developing countries. We assessed Campylobacter contamination of chicken neck-skins at points of slaughter in 5 major cities in Africa (Dakar in Senegal, Yaounde in Cameroon), Oceania (Noumea in New Caledonia), the Indian Ocean (Antananarivo in Madagascar) and Asia (Ho Chi Minh City (HCMC) in Vietnam. One hundred and fifty slaughtered chickens were collected in each of the 5 major cities from semi-industrial abattoirs or markets (direct slaughter by the seller), and 65.5% (491/750) were found to be Campylobacter-positive. Two cities, Yaounde and Noumea, demonstrated high prevalence Campylobacter detection rates (92.7% and 96.7% respectively) in contrast with HCMC (15.3%). Four species were identified among 633 isolates, namely C. jejuni (48.3%), C. coli (37.3%), C. lari (11.7%) and C. upsaliensis (1%). HCMC was the only city with C. lari isolation as was Antananarivo for C. upsaliensis. C. coli was highly prevalent only in Yaounde (69.5%). Among the 491 samples positive in Campylobacter detection, 329 were also positive with the enumeration method. The number of Campylobacter colony-forming units (CFU) per gram of neck-skin in samples positive in enumeration was high (mean of the log(10): 3.2 log(10) CFU/g, arithmetic mean: 7900CFU/g). All the cities showed close enumeration means except HCMC with a 1.81 log(10) CFU/g mean for positive samples. Semi-industrial abattoir was linked to a significant lower count of Campylobacter contamination than direct slaughter by the seller (p=0.006). On 546 isolates (546/633, 86.3%) tested for antibiotic susceptibility, resistance to erythromycin, ampicillin and ciprofloxacin was observed for respectively 11%, 19% and 50%. HCMC was the city where antibiotic resistant rates were the highest (95%, p=0.014). Considering the 329 positive chickens in Campylobacter enumeration, the mean number of resistant isolates to at least 2 different antibiotic families (19.8%), may be estimated ca. 1500CFU/g; the corresponding mean of the log(10) would be 2.5 log(10)CFU/g. As chickens are sold at slaughter and brought directly at home to be cooked, these data suggest a high probability of cross-contamination. A substantial proportion of isolates are drug-resistant, which could lead to potential public health issues. Health authorities should consider measures to reduce Campylobacter contamination of chicken during farming and at slaughter, and to provide appropriate food hygiene education. Further studies are needed in particular to investigate food-handling practices in domestic kitchens.

Antimicrobial effect of diallyl sulphide on Campylobacter jejuni biofilms

OBJECTIVES

Bacterial biofilms pose significant food safety risks because of their attachment to fomites and food surfaces, including fresh produce surfaces. The purpose of this study was to systematically investigate the activity of selected antimicrobials on Campylobacter jejuni biofilms.

METHODS

C. jejuni biofilms and planktonic cells were treated with ciprofloxacin, erythromycin and diallyl sulphide and examined using infrared and Raman spectroscopies coupled with imaging analysis.

RESULTS

Diallyl sulphide eliminated planktonic cells and sessile cells in biofilms at a concentration that was at least 100-fold less than used for either ciprofloxacin or erythromycin on the basis of molarity. Distinct cell lysis was observed in diallyl sulphide-treated planktonic cells using immunoblot analysis and was confirmed by a rapid decrease in cellular ATP. Two phases of C. jejuni biofilm recalcitrance modes against ciprofloxacin and erythromycin were validated using vibrational spectroscopies: (i) an initial hindered adsorption into biofilm extracellular polymeric substance (EPS) and delivery of antibiotics to sessile cells within biofilms; and (ii) a different interaction between sessile cells in a biofilm compared with their planktonic counterparts. Diallyl sulphide destroyed the EPS structure of the C. jejuni biofilm, after which the sessile cells were killed in a similar manner as planktonic cells. Spectroscopic models can predict the survival of sessile cells within biofilms.

CONCLUSIONS

Diallyl sulphide elicits strong antimicrobial activity against planktonic and sessile C. jejuni and may have applications for reducing the prevalence of this microbe in foods, biofilm reduction and, potentially, as an alternative chemotherapeutic agent for multidrug-resistant bacterial strains.

Analysis of risk factors associated with antibiotic-resistant Escherichia coli

Antimicrobial-resistant bacteria represent a major threat to human and animal health. We compared equine fecal samples (n=264) from 138 horses from hospital and nonhospital (livery stable and riding school) premises in North West England to determine the prevalence of Escherichia coli, Salmonella, and Campylobacter and rates of antimicrobial-resistant E. coli strains. Campylobacter jejuni was detected only in hospitalized horses (1.1%), and no Salmonella was identified. Data analysis of the horses' management and veterinary treatments (Tx) identified risk factors associated with shedding of antimicrobial-resistant E. coli. The hospital was the major source of resistant and multi-drug-resistant (MDR) E. coli. Moreover, shedding of antimicrobial-resistant E. coli was associated significantly with hospitalization for a gastrointestinal problem (odds ratio [OR]:±95% confidence intervals=8.50:1.79-40.32), receipt of oral antimicrobial Tx (OR=3.52:1.11-11.10), multiple antimicrobial Tx in hospital (OR/Tx=1.05:1.01-1.09), or geldings (OR=4.62:1.23-17.46). Interestingly, intravenous antimicrobial Tx was negatively associated with shedding of antimicrobial-resistant E. coli (OR=0.18:0.04-0.76). MDR E. coli was associated with hospitalization, antimicrobial Tx in hospital (OR/Tx=3.65:1.54-8.68), and increased age (OR/year=1.11:1.03-1.19). Thus, equine hospitals in this geographic location appear to be an important source of antimicrobial-resistant and MDR E. coli strains, but unlikely reservoirs of Salmonella or Campylobacter. Thus, it is important to moderate antimicrobial Tx given to hospitalized horses to lessen exposure and fecal shedding of resistant pathogens.

Characterization of the dehydratase WcbK and the reductase WcaG involved in GDP-6-deoxy-manno-heptose biosynthesis in Campylobacter jejuni

The capsule of Campylobacter jejuni strain 81-176 comprises the unusual 6-deoxy-α-D-altro-heptose, whose biosynthesis and function are not known. In the present study, we characterized enzymes of the capsular cluster, WcbK and WcaG, to determine their role in 6-deoxy-altro-heptose synthesis. These enzymes are similar to the Yersinia pseudotuberculosis GDP-manno-heptose dehydratase/reductase DmhA/DmhB that we characterized previously. Capillary electrophoresis and MS analyses showed that WcbK is a GDP-manno-heptose dehydratase whose product can be reduced by WcaG, and that WcbK/WcaG can use the substrate GDP-mannose, although with lower efficiency than heptose. Comparison of kinetic parameters for WcbK and DmhA indicated that the relaxed substrate specificity of WcbK comes at the expense of catalytic performance on GDP-manno-heptose. Moreover, although WcbK/WcaG and DmhA/DmhB are involved in altro- versus manno-heptose synthesis respectively, the enzymes can be used interchangeably in mixed reactions. NMR spectroscopy analyses indicated conservation of the sugar manno configuration during catalysis by WcbK/WcaG. Therefore additional capsular enzymes may perform the C3 epimerization necessary to generate 6-deoxy-altro-heptose. Finally, a conserved residue (Thr(187) in WcbK) potentially involved in substrate specificity was identified by structural modelling of mannose and heptose dehydratases. Site-directed mutagenesis and kinetic analyses demonstrated its importance for enzymatic activity on heptose and mannose substrates.

Enteropathogenic bacteria in dogs and cats: diagnosis, epidemiology, treatment, and control

This report offers a consensus opinion on the diagnosis, epidemiology, treatment, and control of the primary enteropathogenic bacteria in dogs and cats, with an emphasis on Clostridium difficile, Clostridium perfringens, Campylobacter spp., Salmonella spp., and Escherichia coli associated with granulomatous colitis in Boxers. Veterinarians are challenged when attempting to diagnose animals with suspected bacterial-associated diarrhea because well-scrutinized practice guidelines that provide objective recommendations for implementing fecal testing are lacking. This problem is compounded by similar isolation rates for putative bacterial enteropathogens in animals with and without diarrhea, and by the lack of consensus among veterinary diagnostic laboratories as to which diagnostic assays should be utilized. Most bacterial enteropathogens are associated with self-limiting diarrhea, and injudicious administration of antimicrobials could be more harmful than beneficial. Salmonella and Campylobacter are well-documented zoonoses, but antimicrobial administration is not routinely advocated in uncomplicated cases and supportive therapy is recommended. Basic practices of isolation, use of appropriate protective equipment, and proper cleaning and disinfection are the mainstays of control. Handwashing with soap and water is preferred over use of alcohol-based hand sanitizers because spores of C. difficile and C. perfringens are alcohol-resistant, but susceptible to bleach (1:10 to 1:20 dilution of regular household bleach) and accelerated hydrogen peroxide. The implementation of practice guidelines in combination with the integration of validated molecular-based testing and conventional testing is pivotal if we are to optimize the identification and management of enteropathogenic bacteria in dogs and cats.

Genotypes and antibiotic resistances of Campylobacter jejuni and Campylobacter coli isolates from domestic and travel-associated human cases

Multilocus sequence typing (MLST) extended with flaB typing of 425 Campylobacter jejuni isolates and 42 Campylobacter coli isolates revealed quite a low overlap between human isolates from travel-associated and domestic cases in Switzerland. Men were more frequently affected by Campylobacter than women, but strains from women and, overall, from travel-associated cases showed mutations conferring quinolone resistance more frequently than strains from men and domestic cases, respectively.

Campylobacter spp. as a Foodborne Pathogen: A Review

Campylobacter is well recognized as the leading cause of bacterial foodborne diarrheal disease worldwide. Symptoms can range from mild to serious infections of the children and the elderly and permanent neurological symptoms. The organism is a cytochrome oxidase positive, microaerophilic, curved Gram-negative rod exhibiting corkscrew motility and is carried in the intestine of many wild and domestic animals, particularly avian species including poultry. Intestinal colonization results in healthy animals as carriers. In contrast with the most recent published reviews that cover specific aspects of Campylobacter/campylobacteriosis, this broad review aims at elucidating and discussing the (i) genus Campylobacter, growth and survival characteristics; (ii) detection, isolation and confirmation of Campylobacter; (iii) campylobacteriosis and presence of virulence factors; and (iv) colonization of poultry and control strategies.

Genotypes and antibiotic resistance of Campylobacter coli in fattening pigs

Campylobacter coli is a food-borne zoonotic pathogen causing human gastroenteritis worldwide. The organism is a commensal in the intestine of many food production animals including fattening pigs. The role of the pig as a potential reservoir for C. coli affecting human either directly or via poultry has hardly been investigated and genetic characterization of porcine strains is needed to address this question. For this aim multilocus sequence typing (MLST) and flaB typing was applied to 256 C. coli isolates from faeces of fattening pig collected during 2009 at different slaughterhouses in Switzerland. In addition genotypic resistances towards macrolides and quinolones based on point mutations in the 23S rRNA and gyrA genes, respectively, were determined. Of the 67 sequence types (STs) obtained by MLST, 37 were found for the first time. flaB typing revealed 46 different types with 14 of them being novel and was useful to further differentiate strains with an identical ST. Quinolone resistance was detected in 33.6% and macrolide resistance was found in 10.6% of isolates. Comparison with 99 C. coli pig isolates from 2001 revealed a significant decrease in antibiotic resistance towards both groups of antibiotics and there was high overlap between genotypes of 2001 and 2009. Little overlap of porcine genotypes was found with 97 C. coli isolates from poultry collected 2008, however, macrolide resistance was significantly higher in pig isolates. In conclusion, C. coli from Swiss pig are heterogeneous containing many novel STs, findings that could reflect the partitioned Swiss pig production with almost no international breed exchange. The antibiotic resistance echoes the use of corresponding drugs in the Swiss livestock production and indicates the efficacy of restrictive application of antibiotics in order to reduce resistances.

Ciprofloxacin-resistant Campylobacter persists in raw retail chicken after the fluoroquinolone ban

In 2005, the FDA withdrew approval for the use of fluoroquinolones in live poultry production. To assess any changes in countable numbers of ciprofloxacin-resistant Campylobacter before and after the fluoroquinolone withdrawal, retail whole raw chicken carcasses (RTCC) purchased in Northwest Arkansas from 2004 to 2006 were sampled for this purpose. Using a previously published direct-plating method developed in our laboratory, we quantified trends of Campylobacter and ciprofloxacin-resistant Campylobacter loads by direct plating whole chicken carcass rinses on Campylobacter agar (CA) or Campylobacter agar containing 8.6 mg/ml ciprofloxacin (CCA). Countable populations of Campylobacter were recovered from 74, 96, and 63% of carcasses sampled in 2004, 2005, and 2006 respectively. The percentages of carcasses with minimum detectable levels of ciprofloxacin-resistant Campylobacter were 20, 42 and 33%, sampled in 2004, 2005 and 2006, respectively. Our 3 year analysis in one geographical area indicated a persistence of Campylobacter and ciprofloxacin-resistant Campylobacter on retail raw chicken carcasses despite the cessation of fluoroquinolone use in poultry production.

Antimicrobial edible apple films inactivate antibiotic resistant and susceptible Campylobacter jejuni strains on chicken breast

Campylobacter jejuni is the leading cause of bacterial diarrheal illness worldwide. Many strains are now becoming multidrug resistant. Apple-based edible films containing carvacrol and cinnamaldehyde were evaluated for bactericidal activity against antibiotic resistant and susceptible C. jejuni strains on chicken. Retail chicken breast samples inoculated with D28a and H2a (resistant strains) and A24a (a sensitive strain) were wrapped in apple films containing cinnamaldehyde or carvacrol at 0.5%, 1.5%, and 3% concentrations, and then incubated at 4 or 23 °C for 72 h. Immediately after wrapping and at 72 h, samples were plated for enumeration of viable C. jejuni. The antimicrobial films exhibited dose- and temperature-dependent bactericidal activity against all strains. Films with ≥1.5% cinnamaldehyde reduced populations of all strains to below detection at 23 °C at 72 h. At 4 °C with cinnamaldehyde, reductions were variable for all strains, ranging from 0.2 to 2.5 logs and 1.8 to 6.0 logs at 1.5% and 3.0%, respectively. Films with 3% carvacrol reduced populations of A24a and H2a to below detection, and D28a by 2.4 logs at 23 °C and 72 h. A 0.5-log reduction was observed for both A24a and D28a, and 0.9 logs for H2a at 4 °C at 3% carvacrol. Reductions ranged from 1.1 to 1.9 logs and 0.4 to 1.2 logs with 1.5% and 0.5% carvacrol at 23 °C, respectively. The films with cinnamaldehyde were more effective than carvacrol films. Reductions at 23 °C were greater than those at 4 °C. Our results showed that antimicrobial apple films have the potential to reduce C. jejuni on chicken and therefore, the risk of campylobacteriosis. Possible mechanisms of antimicrobial effects are discussed.

PRACTICAL APPLICATION

  Apple antimicrobial films could potentially be used in retail food packaging to reduce C. jejuni commonly present on food.

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.

Antimicrobial resistance in Campylobacter coli isolated from pigs in two provinces of China

The aim of this study was to determine the prevalence, antimicrobial resistance and molecular epidemiology of Campylobacter coli isolated from swine in China. A total of 190 C. coli isolates obtained from two slaughter houses and ten conventional pig farms in Shandong (SD, n=95) and Ningxia (NX, n=95) provinces were tested for their susceptibility to 14 antimicrobials. A high prevalence (>95%) of ciprofloxacin and tetracycline-resistant strains was observed in both SD and NX. The erythromycin and clindamycin resistance rates of C. coli from NX (ERY: 54.7% CLI: 43.2%) were higher than those from SD (ERY: 37.9%, CLI: 35.8%). A significant difference (P<0.05) was observed in erythromycin resistance rate, but not (P>0.05) in clindamycin resistance rate. while the resistance rates of ampicillin and kanamycin in NX (AMP: 34.7%, KAN: 43.2%) were significantly lower (P<0.05) than those in SD (AMP: 51.6%, KAN: 71.6%). None of the tested isolates were resistant to phenicols. The majority of the isolates from both provinces (SD: 80% and NX: 73.7%) showed multi-drug resistance profiles. The point mutations of A2075G in the 23S rRNA and C257T in the gyrA gene were detected in 98% (87/89) of macrolide resistant isolates and all ciprofloxacin resistant isolates, respectively. In addition, all tetracycline-resistant isolates harbored the tet(O) gene. The high prevalence of antimicrobial resistance in C. coli strains derived from pigs in China was observed and was likely due to the extensive use of various antimicrobials. Prudent use of antimicrobial agents on farms should be further emphasized to control the dissemination of antimicrobial resistant C. coli.

Comparison of genotypes and antibiotic resistance of Campylobacter jejuni isolated from humans and slaughtered chickens in Switzerland

AIMS

To get an overview of genotypes and antibiotic resistances in Swiss Campylobacter jejuni implicated in human gastroenteritis and to examine the association with isolates from chickens.

METHODS AND RESULTS

Multilocus sequence typing (MLST) and flaB typing were applied to 136 human clinical isolates. Phenotypic resistance to 12 antimicrobials and genotypic resistance to macrolides and quinolones were determined. MLST resulted in 35 known and six new sequence types (ST). The flaB analysis revealed 35 different types, which - in combination with MLST - increased the resolution of the typing approach. Resistance to quinolones, tetracycline and ampicillin was found in 37·5, 33·1 and 8·1% of the isolates, respectively, whereas macrolide resistance was found only once. Genotypic and phenotypic resistance correlated in all cases. A comparison to Camp. jejuni isolated from slaughtered chickens was performed. While 86% of the quinolone-sensitive human isolates showed overlapping MLST-flaB types with those of chicken origin, resistant strains showed only 39% of matching types.

CONCLUSION

Mainly quinolone-sensitive Camp. jejuni strains implicated in human campylobacteriosis showed matching genotypes with isolates originating from chickens.

SIGNIFICANCE AND IMPACT OF THE STUDY

A large proportion of human cases in Switzerland are likely to originate from domestic chickens, confirming that prevention measures in the poultry production are important.

Genotype and antibiotic resistance analyses of Campylobacter isolates from ceca and carcasses of slaughtered broiler flocks

To obtain genetic information about Campylobacter jejuni and Campylobacter coli from broilers and carcasses at slaughterhouses, we analyzed and compared 340 isolates that were collected in 2008 from the cecum right after slaughter or from the neck skin after processing. We performed rpoB sequence-based identification, multilocus sequence typing (MLST), and flaB sequence-based typing; we additionally analyzed mutations within the 23S rRNA and gyrA genes that confer resistance to macrolide and quinolone antibiotics, respectively. The rpoB-based identification resulted in a distribution of 72.0% C. jejuni and 28.0% C. coli. The MLST analysis revealed that there were 59 known sequence types (STs) and 6 newly defined STs. Most of the STs were grouped into 4 clonal complexes (CC) that are typical for poultry (CC21, CC45, CC257, and CC828), and these represented 61.8% of all of the investigated isolates. The analysis of 95 isolates from the cecum and from the corresponding carcass neck skin covered 44 different STs, and 54.7% of the pairs had matching genotypes. The data indicate that cross-contamination from various sources during slaughter may occur, although the majority of Campylobacter contamination on carcasses appeared to originate from the slaughtered flock itself. Mutations in the 23S rRNA gene were found in 3.1% of C. coli isolates, although no mutations were found in C. jejuni isolates. Mutations in the gyrA gene were observed in 18.9% of C. jejuni and 26.8% of C. coli isolates, which included two C. coli strains that carried mutations conferring resistance to both classes of antibiotics. A relationship between specific genotypes and antibiotic resistance/susceptibility was observed.

Fluoroquinolone resistance in campylobacter

Campylobacter is a commensal in poultry, and therefore, poultry and poultry products are major sources of Campylobacter infections in humans. Fluoroquinolones inhibit the growth of Campylobacter and other microorganisms by binding to bacterial DNA gyrase and DNA topoisomerase IV. These enzymes are associated with bacterial transcription, replication, and chromosome condensation and segregation. Selection pressure in the presence of fluoroquinolones rapidly leads to resistance in Campylobacter, due to the selection for mutations in DNA gyrase. Fluoroquinolone-resistant campylobacters have been found in poultry feces and carcasses, and in retail poultry meat products in most areas of the world. In addition, other food animals and the meat products from those animals have been shown contaminated with fluoroquinolone-resistant campylobacters. Even the removal of fluoroquinolones from use in treating animal diseases has not entirely eliminated the presence of resistant Campylobacter jejuni and Campylobacter coli from animals and animal products. Human exposure to Campylobacter infection could be reduced by using strategies that decrease colonization of chickens by the pathogen.

Prevalence and antimicrobial resistance in Campylobacter spp. isolated from retail chicken in two health units in Ontario

Campylobacter is an important enteric pathogen of humans and can cause diarrhea, fever, and abdominal pain. Campylobacter infections have frequently been associated with the handling and consumption of raw and undercooked poultry. Antimicrobial resistance among Campylobacter strains is of concern in the treatment of campylobacteriosis in vulnerable populations. A 2-year multidisciplinary study was conducted in the Perth and Wellington-Dufferin-Guelph public health units in Ontario, Canada, to investigate the prevalence and antimicrobial resistance of Campylobacter spp. in retail chicken. Retail chicken samples were collected from randomly selected stores in these health units. Resulting Campylobacter isolates were tested for susceptibility to amoxicillin-clavulanic acid (AMC), ampicillin (AMP), chloramphenicol (CHL), ciprofloxacin (CIP), clindamycin (CLI), erythromycin (ERY), gentamicin (GEN), nalidixic acid (NAL), tetracycline (TCY), and trimethoprim-sulfamethoxazole (SXT) using the E test. The prevalence of Campylobacter in 1,256 retail chicken samples was 59.6%. Of these positive samples, 9% contained Campylobacter coli, 1% contained Campylobacter lari, and 90% contained Campylobacter jejuni. Of the chicken isolates that were resistant to one or more antimicrobial agents, 301 isolates (40%) were resistant to one agent, 374 (50%) were resistant to two, 39 (5%) were resistant to three, 20 (3%) were resistant to four, and 6 (1%) were resistant to five. Nine isolates (1%) were susceptible to all antimicrobial agents tested. All isolates were susceptible to AMC, CHL, and GEN. Less than 10% of isolates were resistant to NAL, CIP, CLI, ERY, and AMP. Resistance to TCY was common (56%). No isolates had a resistance pattern that included all three antimicrobials important in the treatment of human campylobacteriosis (CIP, ERY, and TCY); however, 24 isolates (3.2%) were resistant to at least two of these antimicrobials.

Antimicrobial resistance in Campylobacter coli selected by tylosin treatment at a pig farm

Limited knowledge is available regarding the dynamics of macrolide resistance under farm conditions with natural Campylobacter populations. We examined the dynamics of antimicrobial resistance in Campylobacter coli at a large pig farm. Faeces were sampled from untreated sows and piglets (n=57), weaned pigs treated with tylosin (n=68) and pigs of the same group 3-5 weeks after withdrawal of tylosin (n=15). Additionally, 48 weaned pigs were sampled after tylosin had not been administered for 7 months at the farm. MICs for seven antimicrobials were determined, isolates were genotyped by PFGE and mutations conferring macrolide resistance were identified. Resistance to at least one antimicrobial agent was higher (P<0.001) in the isolates from the treated pigs (30 of 56) than in those from the untreated animals (2 of 40). Resistance to ciprofloxacin, erythromycin, nalidixic acid and streptomycin was higher (P<0.05) in the isolates from the treated pigs than in those from the untreated animals. All 14 erythromycin-resistant isolates studied (MIC ≥ 512 μg/ml) contained mutation A2075G in 23S rRNA. Resistance against at least one antimicrobial was significantly lower (P<0.05) when tylosin had not been administered for 7 months. Resistance to erythromycin and streptomycin also decreased (P<0.05). PFGE analysis revealed a change of genotypes induced by tylosin treatment. In conclusion, tylosin treatment of pigs selected for a high-level of resistance to erythromycin and resistance to ciprofloxacin, nalidixic acid and streptomycin also increased in C. coli isolates within a few days.

Prevalence and patterns of antimicrobial resistance in Campylobacter spp isolated from pigs reared under antimicrobial-free and conventional production methods in eight states in the Midwestern United States

OBJECTIVE

To compare apparent prevalence and patterns of antimicrobial resistance in Campylobacter spp in feces collected from pigs reared with antimicrobial-free versus conventional production methods in 8 states in the Midwestern United States.

DESIGN

Cross-sectional study.

SAMPLE POPULATION

95 swine farms that used antimicrobial-free (n = 35) or conventional (60) production methods.

PROCEDURES

Fecal samples from 15 pigs/farm were collected. Biochemical and multiplex-PCR analyses were used to identify Campylobacter spp. The minimal inhibitory concentrations of erythromycin, azithromycin, ciprofloxacin, nalidixic acid, gentamicin, and tetracycline for these organisms were determined by use of a commercially available antimicrobial gradient strip. The data were analyzed by use of population-averaged statistical models.

RESULTS

Campylobacter spp were isolated from 512 of 1,422 pigs. A subset (n = 464) of the 512 isolates was available for antimicrobial susceptibility testing. The apparent prevalence of Campylobacter spp isolates from pigs on conventional farms (35.8%) and antimicrobial-free farms (36.4%) did not differ significantly. Resistances to azithromycin, erythromycin, and tetracycline were significantly higher on conventional farms (70.0%, 68.3%, and 74.5%, respectively) than antimicrobial-free farms (20.1%, 21.3%, and 48.8%, respectively). Resistances to azithromycin, erythromycin, and tetracycline declined as the number of years that a farm was antimicrobial-free increased.

CONCLUSIONS AND CLINICAL RELEVANCE

Production method did not affect the apparent prevalence of Campylobacter spp on swine farms. However, antimicrobial-free farms had a significantly lower prevalence of antimicrobial resistance. Although cessation of antimicrobial drug use will lower resistance over time, investigation of other interventions designed to reduce resistance levels is warranted.

Antimicrobial susceptibility of clinical Campylobacter isolates collected at a German university hospital during the period 2006-2008

A total of 113 clinical Campylobacter strains (105 C. jejuni, 7 C. coli, 1 C. lari) were collected between 2006 and 2008 and tested for antimicrobial susceptibility to erythromycin, ciprofloxacin, doxycycline and meropenem. Of all the Campylobacter isolates, 52.2% were resistant to ciprofloxacin and 38.0% to doxycycline. None of them was resistant to erythromycin or meropenem. However, 51.3% of all Campylobacter isolates were intermediate susceptible to erythromycin (minimum inhibitory concentration 1-4 mg/l). These data confirm the value of macrolides as the drugs of choice for the treatment of severe Campylobacter infections.

Expanded multilocus sequence typing and comparative genomic hybridization of Campylobacter coli isolates from multiple hosts

The purpose of this work was to evaluate the evolutionary history of Campylobacter coli isolates derived from multiple host sources and to use microarray comparative genomic hybridization to assess whether there are particular genes comprising the dispensable portion of the genome that are more commonly associated with certain host species. Genotyping and ClonalFrame analyses of an expanded 16-gene multilocus sequence typing (MLST) data set involving 85 isolates from 4 different hosts species tentatively supported the development of C. coli host-preferred groups and suggested that recombination has played various roles in their diversification; however, geography could not be excluded as a contributing factor underlying the history of some of the groups. Population genetic analyses of the C. coli pubMLST database by use of STRUCTURE suggested that isolates from swine form a relatively homogeneous genetic group, that chicken and human isolates show considerable genetic overlap, that isolates from ducks and wild birds have similarity with environmental water samples and that turkey isolates have a connection with human infection similar to that observed for chickens. Analysis of molecular variance (AMOVA) was performed on these same data and suggested that host species was a significant factor in explaining genetic variation and that macrogeography (North America, Europe, and the United Kingdom) was not. The microarray comparative genomic hybridization data suggested that there were combinations of genes more commonly associated with isolates derived from particular hosts and, combined with the results on evolutionary history, suggest that this is due to a combination of common ancestry in some cases and lateral gene transfer in others.

Prevalence and antimicrobial resistance of Campylobacter isolates in broilers from China

The prevalence and antimicrobial resistance of Campylobacter spp. in broiler chickens were determined in Shandong Province, China. In total, 275 Campylobacter isolates were obtained from 767 broiler cecal samples, including 208 Campylobacter jejuni, 53 Campylobacter coli, and 14 unidentified Campylobacter isolates. Minimal inhibitory concentrations of 11 antimicrobial agents were determined using the agar dilution method recommended by CLSI. More than 98% of the tested Campylobacter isolates were resistant to quinolones (nalidixic acid, ciprofloxacin and enrofloxacin) and tetracyclines (tetracycline and doxycycline). The C. jejuni isolates also exhibited a high rate of resistance to phenicol antibiotics and a moderate rate of resistance to macrolides and gentamicin. On the contrary, the C. coli isolates showed a high-level resistance to macrolides and gentamicin and little resistance to phenicol antibiotics. The vast majority of the Campylobacter isolates were classified as multidrug resistant. These findings reveal a broad extent of antimicrobial resistance in Campylobacter isolates from poultry in China and underline the need for prudent use of antibiotics in poultry production to minimize the spread of antibiotic resistant Campylobacter.