The Natural Antimicrobial Carvacrol Inhibits Campylobacter jejuni Motility and Infection of Epithelial Cells

Background

Natural compounds with anti-microbial properties are attractive reagents to reduce the use of conventional antibiotics. Carvacrol, the main constituent of oregano oil, inhibits the growth of a variety of bacterial foodborne pathogens. As concentrations of carvacrol may vary in vivo or when used in animal feed, we here investigated the effect of subinhibitory concentrations of the compound on major virulence traits of the principal bacterial foodborne pathogen Campylobacter jejuni.

Methods/Principal Findings

Motility assays revealed that subinhibitory concentrations of carvacrol inhibited the motility of C. jejuni without affecting bacterial growth. Immunoblotting and electron microscopy showed that carvacrol-treated C. jejuni still expressed flagella. The loss of motility was not caused by reduced intracellular ATP levels. In vitro infection assays demonstrated that subinhibitory concentrations of carvacrol also abolished C. jejuni invasion of human epithelial cells. Bacterial uptake of invasive Escherichia coli was not blocked by carvacrol. Exposure of C. jejuni to carvacrol prior to infection also inhibited cellular infection, indicating that the inhibition of invasion was likely caused by an effect on the bacteria rather than inhibition of epithelial cell function.

Conclusions/Significance

Bacterial motility and invasion of eukaryotic cells are considered key steps in C. jejuni infection. Our results indicate that subinhibitory concentrations of carvacrol effectively block these virulence traits by interfering with flagella function without disturbing intracellular ATP levels. These results broaden the spectrum of anti-microbial activity of carvacrol and support the potential of the compound for use in novel infection prevention strategies.     

Antimicrobial Resistance Profiles of Campylobacter jejuni Isolates from Wild Birds in Sweden

In order to determine the occurrence and frequency of resistant strains of the bacterium Campylobacter jejuni and to establish baseline MICs in isolates from an environmental reservoir, the resistance profiles of 10 antimicrobial substances were determined for 137 C. jejuni isolates from wild birds in Sweden. Observed MICs were generally low, with only low to moderate incidence of resistance to the tested compounds. One isolate, however, was resistant to nalidixic acid and ciprofloxacin, indicating that quinolone-resistant genotypes of C. jejuni have the potential to spread to wild bird hosts.     

Effects of Subtherapeutic Administration of Antimicrobial Agents to Beef Cattle on the Prevalence of Antimicrobial Resistance in Campylobacter jejuni and Campylobacter hyointestinalis

The influence of antimicrobial agents on the development of antimicrobial resistance (AMR) in Campylobacter isolates recovered from 300 beef cattle maintained in an experimental feedlot was monitored over a 315-day period (11 sample times). Groups of calves were assigned to one of the following antimicrobial treatments: chlortetracycline and sulfamethazine (CS), chlortetracycline alone (Ct), virginiamycin, monensin, tylosin phosphate, and no antimicrobial agent (i.e., control treatment). In total, 3,283 fecal samples were processed for campylobacters over the course of the experiment. Of the 2,052 bacterial isolates recovered, 92% were Campylobacter (1,518 were Campylobacter hyointestinalis and 380 were C. jejuni). None of the antimicrobial treatments decreased the isolation frequency of C. jejuni relative to the control treatment. In contrast, C. hyointestinalis was isolated less frequently from animals treated with CS and to a lesser extent from animals treated with Ct. The majority (≥94%) of C. jejuni isolates were sensitive to ampicillin, erythromycin, and ciprofloxacin, but more isolates with resistance to tetracycline were recovered from animals fed Ct. All of the 1,500 isolates of C. hyointestinalis examined were sensitive to ciprofloxacin. In contrast, 11%, 10%, and 1% of these isolates were resistant to tetracycline, erythromycin, and ampicillin, respectively. The number of animals from which C. hyointestinalis isolates with resistance to erythromycin and tetracycline were recovered differed among the antimicrobial treatments. Only Ct administration increased the carriage rates of erythromycin-resistant isolates of C. hyointestinalis, and the inclusion of CS in the diet increased the number of animals from which tetracycline-resistant isolates were recovered. The majority of C. hyointestinalis isolates with resistance to tetracycline were obtained from cohorts within a single pen, and most of these isolates were recovered from cattle during feeding of a forage-based diet as opposed to a grain-based diet. The findings of this study show that the subtherapeutic administration of tetracycline, alone and in combination with sulfamethazine, to feedlot cattle can select for the carriage of resistant strains of Campylobacter species. Considering the widespread use of in-feed antimicrobial agents and the high frequency of beef cattle that shed campylobacters, the development of AMR should be monitored as part of an on-going surveillance program.     

Clonal Population Structure and Antimicrobial Resistance of Campylobacter jejuni in Chicken Meat from Belgium

Campylobacter jejuni is one of the most important causes of human diarrhea worldwide. In the present work, multilocus sequence typing was used to study the genotypic diversity of 145 C. jejuni isolates from 135 chicken meat preparations sampled across Belgium. Isolates were further typed by pulsed-field gel electrophoresis, and their susceptibilities to six antimicrobials were determined. Fifty-seven sequence types (STs) were identified; 26.8% of the total typed isolates were ST-50, ST-45, or ST-257, belonging to clonal complex CC-21, CC-45, or CC-257, respectively. One clonal group comprised 22% (32/145) of all isolates, originating from five different companies and isolated over seven sampling months. Additionally, 53.1% of C. jejuni isolates were resistant to ciprofloxacin, and 48.2% were resistant to tetracycline; 28.9% (42/145) of all isolates were resistant to both ciprofloxacin and tetracycline. The correlation between certain C. jejuni clonal groups and resistance to ciprofloxacin and tetracycline was notable. C. jejuni isolates assigned to CC-21 (n = 35) were frequently resistant to ciprofloxacin (65.7%) and tetracycline (40%); however, 90% (18/20) of the isolates assigned to CC-45 were pansusceptible. The present study demonstrates that certain C. jejuni genotypes recur frequently in the chicken meat supply. The results of molecular typing, combined with data on sample sources, indicate a possible dissemination of C. jejuni clones with high resistance to ciprofloxacin and/or tetracycline. Whether certain clonal groups are common in the environment and repeatedly infect Belgian broiler flocks or whether they have the potential to persist on farms or in slaughterhouses needs further investigation.Campylobacter jejuni is among the most common bacterial causes of human gastroenteritis worldwide (4, 23). Infected humans exhibit a range of clinical symptoms from mild, watery diarrhea to severe inflammatory diarrhea (14). In addition, C. jejuni has been identified as an important infectious trigger for Guillain-Barré syndrome, the most common cause of acute flaccid paralysis in polio-free regions (16). Another issue of concern regarding Campylobacter is the increase in antimicrobial resistance appearing in various regions around the world (1). Infection with an antimicrobial-resistant Campylobacter strain may lead to a suboptimal outcome of antimicrobial treatment or even to treatment failure (11).Consumption of contaminated water and raw milk has been implicated in campylobacteriosis outbreaks (23). However, the majority of human cases are sporadic, and consumption or mishandling of contaminated raw or undercooked poultry meat is believed to be an important source of infection. Risk assessment studies, outbreak investigations, and case-control reports all incriminate chicken meat as a major source, perhaps the major source, of food-borne transmission (14, 17, 32, 48). In Belgium in 1999, a controlled withdrawal of poultry products from sale due to alleged dioxin contamination resulted in a 40% reduction in the frequency of human campylobacteriosis (44). Thereafter and since the year 2000, the Campylobacter contamination of Belgian poultry carcasses and meat has been monitored by the Federal Agency for the Safety of the Food Chain, and the rate of positive samples is regarded as high. In 2006, 55.5% of cecal samples (n = 6,443) from Belgian broilers at slaughter tested positive for Campylobacter (3). In 2007, an industry-focused survey reported that 48% of Belgian chicken meat preparations (n = 656) were contaminated with Campylobacter (19).Molecular typing is an important tool in elucidating the diversity and transmission routes of Campylobacter isolates contaminating the food chain. In the United States, molecular analysis of Campylobacter spp. from poultry production and processing environments showed that many of the clones found within a flock are present in the final products, although the diversity of Campylobacter isolates in the final product was lower than that observed in the flock (22). Furthermore, numerous molecular epidemiological studies indicate that the genotypes of C. jejuni isolated from human cases overlap those of poultry origin (17, 47). Various molecular typing methods for the study of the population structure of Campylobacter are currently available (46). Among these, the multilocus sequence typing (MLST) approach is an emerging tool for research on the population structure and molecular epidemiology of Campylobacter. The technique is highly reproducible, portable, and easy to interpret, and results can be shared through a publicly accessible online database (31, 34). As such, MLST is becoming an important tool for studying the molecular epidemiology of Campylobacter in a global context. The accumulation of sequence typing data generated from different countries and settings could allow the creation of more-sophisticated models of the epidemiology and evolution of bacterial pathogens and the development of improved approaches for combating their spread (41).In Belgium, there is a paucity of information regarding the population structure of Campylobacter in the chicken meat supply. No population-based surveys have been conducted to investigate the molecular epidemiology of C. jejuni in chicken meat at points close to human consumption. In this study, MLST and pulsed-field gel electrophoresis (PFGE) were used to characterize the diversity of, and clonal relationships among, 145 C. jejuni isolates from Belgian chicken meat preparations. In addition, we characterized the antimicrobial resistance in this collection and correlated it with C. jejuni genotypes.     

Nucleases Encoded by the Integrated Elements CJIE2 and CJIE4 Inhibit Natural Transformation of Campylobacter jejuni

The species Campylobacter jejuni is naturally competent for DNA uptake; nevertheless, nonnaturally transformable strains do exist. For a subset of strains we previously showed that a periplasmic DNase, encoded by dns, inhibits natural transformation in C. jejuni. In the present study, genetic factors coding for DNase activity in the absence of dns were identified. DNA arrays indicated that nonnaturally transformable dns-negative strains contain putative DNA/RNA nonspecific endonucleases encoded by CJE0566 and CJE1441 of strain RM1221. These genes are located on C. jejuni integrated elements 2 and 4. Expression of CJE0566 and CJE1441 from strain RM1221 and a homologous gene from strain 07479 in DNase-negative Escherichia coli and C. jejuni strains indicated that these genes code for DNases. Genetic transfer of the genes to a naturally transformable C. jejuni strain resulted in a decreased efficiency of natural transformation. Modeling suggests that the C. jejuni DNases belong to the Serratia nuclease family. Overall, the data indicate that the acquisition of prophage-encoded DNA/RNA nonspecific endonucleases inhibits the natural transformability of C. jejuni through hydrolysis of DNA.Bacterial species display genetic diversity that can contribute to their capacity to adapt and survive in changing environments. One of the processes contributing to genetic diversity is horizontal gene transfer. This involves the acquisition of genetic material, ultimately resulting in insertion of the acquired DNA and/or deletion of existing genetic material (9). The ability to take up exogenous DNA is present in many bacteria (4, 30). In general, uptake of DNA during natural transformation involves binding of double-stranded DNA to bacterial surface components, followed by transport through the cytoplasmic membrane (5). Upon transport, one of the DNA strands is degraded into nucleotides, whereas the other strand enters the cytoplasm and may provide new characteristics to the host genome.One of the bacterial species naturally competent for DNA uptake is the human pathogen Campylobacter jejuni (32). Worldwide, C. jejuni is one of the most frequent causes of human bacterial gastroenteritis (3). In C. jejuni horizontal gene transfer can occur within a host, as witnessed in chickens infected with two C. jejuni strains carrying distinct genetic markers (7). The ability to acquire exogenous DNA contributes to the generation of genetic diversity in C. jejuni, which is reflected by the genotypic variation seen among strains (8, 29, 33).Thus far, several genes have been implicated in the process of natural transformation of C. jejuni (35). Yet not all C. jejuni strains are equally competent, since differences in natural transformation frequencies have been noted, and even nonnaturally transformable strains do exist (32, 34). Previously, we demonstrated that DNA-hydrolyzing activity inhibits natural transformation of C. jejuni and identified Dns as one of the responsible nucleases (13). Dns is encoded by a putative prophage present in C. jejuni strain RM1221, namely, C. jejuni integrated element 1 (CJIE1).The presence of DNase activity in C. jejuni has long been known and was in fact one of the criteria for Lior''s extended biotyping scheme for thermophilic campylobacters (21). Through identification of dns a genetic basis for DNase activity by a subset of C. jejuni strains has been provided, but the genetic factors responsible for DNase activity in dns-negative nonnaturally transformable C. jejuni strains are not yet known.In this study, we attempted to identify and functionally characterize an additional DNase-encoding gene(s) present in a subset of nonnaturally transformable DNase⁺ C. jejuni strains. Comparative genomic hybridization for DNase⁺/dns⁺ and DNase⁺/ dns-negative C. jejuni strains revealed three highly homologous genes encoded by the putative phage-related integrated elements CJIE2 and CJIE4. Functional analysis showed that these genes encode DNases that reduce the natural transformability of C. jejuni through hydrolysis of exogenous DNA.     

Antimicrobial resistance and plasmid profiles of Campylobacter jejuni and Campylobacter coli from human and animal sources

AIMS: The purpose of this study was to determine the susceptibility of Campylobacter jejuni and Campylobacter coli isolates to antimicrobial agents and to investigate the presence of plasmid DNA. METHODS AND RESULTS: A total of 15 clinical isolates from children faeces, and 29 animal isolates of Campylobacter jejuni (n=22) and Campylobacter coli (n=22) were tested for susceptibility to 9 antimicrobial agents using a disc diffusion method, and screened for the presence of plasmid DNA by agarose gel electrophoresis. Of the 44 isolates, 56.8% were resistant to sulphonamide, 25% to norfloxacin, 18.2% to erythromicin, ciprofloxacin and ampicillin, and 13.6% to tetracycline. All isolates were susceptible to gentamicin, chloramphenicol and cefotaxime. Plasmids were detected in one Camp. jejuni (4.54%) strain isolated from sheep and in six (27.27%) Camp. coli strains isolated from rhesus monkey(3), swine(2), and poultry(1) with sizes ranging from 3.4 to 50 kb. CONCLUSIONS: The majority of the human isolates were susceptible to antibiotics commonly used for the treatment of campylobacteriosis. SIGNIFICANCE AND IMPACT OF THE STUDY: The origin and spread of Campylobacter resistance to antibiotics are discussed, with particular respect to the current situation in Brazil.     

Prevalence of Campylobacter spp. in Cattle in Finland and Antimicrobial Susceptibilities of Bovine Campylobacter jejuni Strains

The study investigated the prevalence of Campylobacter spp. in Finnish cattle at slaughter and carcass contamination after slaughter. During the period January to December 2003, bovine rectal fecal samples (n = 952) and carcass surface samples (n = 948) from 12 out of 15 Finnish slaughterhouses were examined. In total, campylobacters were detected in 31.1% of fecal samples and in 3.5% of carcass surface samples. Campylobacter jejuni was isolated from 19.5%, Campylobacter coli from 2.2%, and presumptive Campylobacter hyointestinalis from 10.8% of fecal samples. Campylobacters were detected in 4.4% and 37.4% of the fecal samples examined both by direct culture and by enrichment (n = 730), respectively, suggesting a low level of campylobacters in the intestinal content. A slightly increasing trend was observed in the overall prevalence of campylobacters towards the end of summer and autumn. Seventeen different serotypes were detected among the fecal C. jejuni isolates using a set of 25 commercial antisera for serotyping heat-stable antigens (Penner) of C. jejuni by passive hemagglutination. The predominant serotypes, Pen2 and Pen4-complex, were isolated from 52% of the fecal samples. Subtyping by pulsed-field gel electrophoresis (SmaI) yielded 56 and 20 subtypes out of 330 fecal and 70 carcass C. jejuni isolates, respectively. MICs of ampicillin, enrofloxacin, erythromycin, gentamicin, nalidixic acid, and oxytetracycline for 187 C. jejuni isolates were determined using a commercial broth microdilution method. Sixteen (9%) of the isolates were resistant to at least one of the antimicrobials tested. Resistance to nalidixic acid was most commonly detected (6%). No multiresistance was observed.     

Characterization and Localization of the Campylobacter jejuni Transformation System Proteins CtsE,CtsP, and CtsX

The human pathogen Campylobacter jejuni is naturally competent for transformation with its own DNA. Genes required for efficient transformation in C. jejuni include those similar to components of type II secretion systems found in many Gram-negative bacteria (R. S. Wiesner, D. R. Hendrixson, and V. J. DiRita, J Bacteriol 185:5408–5418, 2003, http://dx.doi.org/10.1128/JB.185.18.5408-5418.2003). Two of these, ctsE and ctsP, encode proteins annotated as putative nucleotide binding nucleoside triphosphatases (NTPases) or nucleoside triphosphate (NTP) binding proteins. Here we demonstrate that the nucleotide binding motifs of both proteins are essential for their function in transformation of C. jejuni. Localization experiments demonstrated that CtsE is a soluble protein while CtsP is membrane associated in C. jejuni. A bacterial two-hybrid screen identified an interaction between CtsP and CtsX, an integral membrane protein also required for transformation. Topological analysis of CtsX by the use of LacZ and PhoA fusions demonstrated it to be a bitopic, integral membrane protein with a cytoplasmic amino terminus and a periplasmic carboxyl terminus. Notwithstanding its interaction with membrane-localized CtsX, CtsP inherently associates with the membrane, requiring neither CtsX nor several other Cts proteins for this association.     

Antimicrobial Susceptibility Profiles and Molecular Typing of Campylobacter jejuni and Campylobacter coli Isolates from Ducks in South Korea

Campylobacter is a food-borne zoonotic pathogen that causes human gastroenteritis worldwide. Campylobacter bacteria are commensal in the intestines of many food production animals, including ducks and chickens. The objective of the study was to determine the prevalence of Campylobacter species in domestic ducks, and the agar dilution method was used to determine resistance of the isolates to eight antibiotics. In addition, multilocus sequence typing (MLST) was performed to determine the sequence types (STs) of selected Campylobacter isolates. Between May and September 2012, 58 duck farms were analyzed, and 56 (96.6%) were positive for Campylobacter. Among the isolates, 82.1% were Campylobacter jejuni, 16.1% were C. coli, and one was unidentified by PCR. Of the 46 C. jejuni isolates, 87.0%, 10.9%, and 21.7% were resistant to ciprofloxacin, erythromycin, and azithromycin, respectively. Among the C. coli isolates, all 9 strains were resistant to ampicillin, and 77.8% and 33.3% were resistant to ciprofloxacin and azithromycin, respectively. The majority of the Campylobacter isolates were classified as multidrug resistant. Twenty-eight STs were identified, including 20 STs for C. jejuni and 8 STs for C. coli. The most common clonal complexes in C. jejuni were the ST-21 complex and the ST-45 complex, while the ST-828 complex predominated in C. coli. The majority of isolates were of STs noted in ducks and humans from earlier studies, along with seven STs previously associated only with human disease. These STs overlapped between duck and human isolates, indicating that Campylobacter isolates from ducks should be considered potential sources of human infection.     

Campylobacter jejuni FlpA Binds Fibronectin and Is Required for Maximal Host Cell Adherence

Campylobacter jejuni is one of the most frequent bacterial causes of food-borne gastrointestinal disease in developed countries. Previous work indicates that the binding of C. jejuni to human intestinal cells is crucial for host colonization and disease. Fibronectin (Fn), a major constituent of the extracellular matrix, is a ∼250-kDa glycoprotein present at regions of cell-to-cell contact in the intestinal epithelium. Fn is composed of three types of repeating units: type I (∼45 amino acids), type II (∼60 amino acids), and type III (∼90 amino acids). The deduced amino acid sequence of C. jejuni flpA (Cj1279c) contains at least three Fn type III domains. Based on the presence of the Fn type III domains, we hypothesized that FlpA contributes to the binding of C. jejuni to human INT 407 epithelial cells and Fn. We assessed the contribution of FlpA in C. jejuni binding to host cells by in vitro adherence assays with a C. jejuni wild-type strain and a C. jejuni flpA mutant and binding of purified FlpA protein to Fn by enzyme-linked immunosorbent assay (ELISA). Adherence assays revealed the binding of the C. jejuni flpA mutant to INT 407 epithelial cells was significantly reduced compared with that for a wild-type strain. In addition, rabbit polyclonal serum generated against FlpA blocked C. jejuni adherence to INT 407 cells in a concentration-dependent manner. Binding of FlpA to Fn was found to be dose dependent and saturable by ELISA, demonstrating the specificity of the interaction. Based on these data, we conclude that FlpA mediates C. jejuni attachment to host epithelial cells via Fn binding.Members of the genus Campylobacter are gram-negative, asaccharolytic, motile bacteria, which grow optimally in the laboratory at temperatures between 37 and 42°C under microaerophilic conditions. Although members of Campylobacter spp. were initially recognized to cause disease in sheep and cattle, Campylobacter jejuni was not recognized as a human pathogen until much later (25). Infection of humans with C. jejuni is characterized by a rapid onset of fever, abdominal cramps, and diarrhea. C. jejuni is now recognized as one of the leading bacterial causes of gastroenteritis in the world. In spite of the incidence of campylobacteriosis, relatively few C. jejuni virulence genes have been characterized, and our understanding of the virulence properties of C. jejuni is limited compared with that of other enteric pathogens, including Salmonella, Shigella, and Yersinia spp.The ability of C. jejuni to cause disease is a complex, multifactorial process. Virulence factors that contribute to the pathogenesis of C. jejuni are associated with motility, host (target) cell adherence, host cell invasion, protein secretion, alteration of host cell signaling pathways, induction of host cell death, evasion of host immune defenses, iron acquisition, and drug/detergent resistance (14, 18). The binding of C. jejuni to specific host cell ligands is hypothesized to play a fundamental role in host colonization and disease progression, since it prevents the organism''s clearance from the intestine by peristalsis and fluid flow. Fauchere et al. (5) reported that C. jejuni isolates recovered from individuals with fever and diarrhea adhered to cultured cells in greater numbers than isolates recovered from asymptomatic individuals. While there is no evidence indicating that C. jejuni produces fimbriae that assist in host colonization (7), a number of constitutively synthesized proteins have been proposed to act as adhesins. Bacterial adhesins are surface-exposed macromolecules that facilitate an organism''s binding to the host cell receptors. Known and putative C. jejuni adhesins include CadF, CapA, FlpA, and PorA (MOMP) (6).An emerging theme among pathogenic microorganisms is their ability to utilize host cell molecules during the infectious process to facilitate their binding and entry into host cells (27). More specifically, many bacterial pathogens have been found to bind to fibronectin (Fn), which in turn modifies host cell signaling pathways to the pathogen''s advantage. Fn exists as a dimer of nearly identical 250-kDa subunits that are linked by a pair of disulfide bonds near their C termini. Each Fn monomer is composed of three types of repeating units: type I (∼45 amino acids), type II (∼60 amino acids), and type III (∼90 amino acids) (22). In total, each monomer contains 12 type I repeats, two type II repeats, and 15 to 17 type III repeats. Fn participates in many cellular interactions, including tissue repair, embryogenesis, blood clotting, and cell migration/adhesion. Plasma Fn, which is synthesized by hepatocytes, is soluble (22). In contrast, Fn involved in host cell-extracellular matrix (ECM) interaction, which is synthesized by chondrocytes, fibroblasts, endothelial cells, macrophages, and certain epithelial cells, is present in an insoluble form (22). Fn serves as an adhesion molecule that anchors cells to ECM components, including collagen and other proteoglycan substrates.The bacterial proteins that bind to ECM components have been termed microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) (23). The C. jejuni CadF protein is a member of the MSCRAMM family and one of the most extensively characterized C. jejuni virulence determinants (10-12, 15, 16, 19-21, 24, 28). CadF mediates the binding of C. jejuni to Fn, promotes bacterium-host cell interactions, and facilitates the organism''s colonization of chickens (10, 11, 15, 16, 20, 21, 28). In addition to CadF, we recently reported that a mutation in Cj1279c resulted in a C. jejuni mutant that poorly colonized broiler chickens compared with a C. jejuni wild-type strain. The product encoded by the Cj1279c gene was termed Fibronectin-like protein A (FlpA) because the protein harbors Fn type III domains (6). The goal of this study was to characterize the binding properties of FlpA and to determine if this protein is a member of the MSCRAMM family. Here we provide experimental evidence that C. jejuni FlpA is surface exposed, promotes the bacterium''s attachment to host epithelial cells, and has Fn binding activity. Assays were also performed to determine if CadF and FlpA act cooperatively to promote binding of C. jejuni to host cells and Fn. We submit that the identification of a second MSCRAMM in C. jejuni highlights the importance of Fn binding in host colonization and disease.     

Serotyping of Campylobacter jejuni, Campylobacter coli, and Campylobacter laridis from domestic and wild animals

By using 50 unabsorbed antisera, we were able to serotype 272 (65.7%) of 414 thermotolerant campylobacters from wild and domestic animals, on the basis of heat-stable antigens identified by means of passive hemagglutination. Forty-two serotypes were recognized. The pattern of serotypes detected in the various animal species was compared to human clinical isolates by using the Czekanowski index (proportional similarity index). The highest degree of similarity to the clinical isolates was observed for the poultry isolates, followed by strains from wild birds, flies, and pigs (in order of decreasing similarity). The serotypes recovered most frequently from poultry (LAU 1 and LAU 2) were also most prevalent in Norwegian patients. In contrast, serotype LAU 35/44, the predominant porcine serotype, was never recovered from human clinical specimens. Flies captured in chicken farms and in piggeries harbored serotypes which were also commonly seen in chickens and pigs, respectively. Nine of the strains included in this study could not be ascribed to any defined species. All of these were resistant to nalidixic acid and did not produce H2S.     

Antimicrobial susceptibility of Campylobacter jejuni subsp. jejuni assessed by E-test and double dilution agar method in Southern Chile

The susceptibility patterns of 108 Campylobacter jejuni subsp. jejuni clinical strains, to six antimicrobial agents was determined by using the E-test and the double dilution agar methods. Using both methods, no strain was found to be resistant to ciprofloxacin, erythromycin and gentamicin, but two (1.8%) were resistant to tetracycline and all to aztreonam. Seven (6.5%) strains were resistant to ampicillin by the E-test and five (4.6%) by the double dilution agar method and by both methods. No great discrepancies were observed between both methods.     

Serotyping of Campylobacter jejuni, Campylobacter coli, and Campylobacter laridis from domestic and wild animals.

By using 50 unabsorbed antisera, we were able to serotype 272 (65.7%) of 414 thermotolerant campylobacters from wild and domestic animals, on the basis of heat-stable antigens identified by means of passive hemagglutination. Forty-two serotypes were recognized. The pattern of serotypes detected in the various animal species was compared to human clinical isolates by using the Czekanowski index (proportional similarity index). The highest degree of similarity to the clinical isolates was observed for the poultry isolates, followed by strains from wild birds, flies, and pigs (in order of decreasing similarity). The serotypes recovered most frequently from poultry (LAU 1 and LAU 2) were also most prevalent in Norwegian patients. In contrast, serotype LAU 35/44, the predominant porcine serotype, was never recovered from human clinical specimens. Flies captured in chicken farms and in piggeries harbored serotypes which were also commonly seen in chickens and pigs, respectively. Nine of the strains included in this study could not be ascribed to any defined species. All of these were resistant to nalidixic acid and did not produce H2S.     

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.