Does age acquired immunity confer selective protection to common serotypes of Campylobacter jejuni?

Clinical and microbiological findings of recurrent Campylobacter spp. gastroenteritis in a tertiary care hospital

INTRODUCTION

Campylobacter spp. is the leading cause of bacterial enteritis in industrialized countries, but the literature about its recurrence is scarce. The objective of this study is to analyze a case series of recurrent campylobacteriosis in adult and pediatric patients.

METHODS

During a two-year period, the demographic, clinical and microbiological data were collected retrospectively from patients who met the clinical criteria of recurrent Campylobacter spp. gastroenteritis. Enteropathogens were identified by a multiplex-PCR gastrointestinal pathogens panel. When Campylobacter spp. was detected, the stool sample was cultured in specific medium and tested for antibiotic susceptibility.

RESULTS

Twenty-four (2.03%) out of 1180 patients with Campylobacter spp. positive-PCR met the inclusion criteria. Thirteen patients suffered from underlying diseases, and 11 had no known risk factors but they were all pediatric patients. From the 24 patients were documented 70 episodes. One patient had two episodes of bacteremia. Coinfection/co-detection with other enteropathogens was found in 10 patients being Giardia intestinalis the most frequent. Twelve (22.6%) out of 53 isolates were resistant to macrolides. One patient had two isolates of multi-drug resistant C. coli, only susceptible to gentamicin.

CONCLUSION

The results suggest the presence of underlying diseases in most adult patients with recurrent Campylobacter spp. infections, particularly primary immunodeficiency. Most of the pediatric patients with recurrent campylobacteriosis lack of known risk factors. Concomitant detection with other enteropathogens was common. The resistance to macrolides was much higher as compared with previous reported rates.

Progress toward the Development of Glycan-Based Vaccines against Campylobacteriosis

As one of the main causes of bacterial diarrhea and a major risk factor for triggering Guillain-Barré autoimmune syndrome, campylobacteriosis, that is, Campylobacter spp. infections, represents a major health issue worldwide. There is thus a pressing need for developing an effective and broad-coverage campylobacteriosis vaccine. Campylobacter jejuni, an encapsulated, multidrug resistant Gram-negative bacterium, expresses virulence-associated capsular polysaccharides (CPSs), which constitute exquisite targets for the design of glycoconjugate vaccines. In that context, synthetic carbohydrate chemistry acts as a crucial enabling technology for the preparation of homogeneous constructs while allowing antigenic epitopes to be deciphered and probed at the molecular level. This review aims at covering recent developments in CPS-based campylobacteriosis vaccines as well as in the total syntheses of C. jejuni-related mono- and oligosaccharide mimics.

Distribution of Capsular Types of Campylobacter jejuni Isolates from Symptomatic and Asymptomatic Children in Peru

Campylobacter jejuni is the leading bacterial cause of diarrhea worldwide. A capsular polysaccharide (CPS) conjugate vaccine is under development and requires determination of the valency. However, distribution of CPS types circulating globally is presently poorly described. We aimed to determine whether CPS type distribution in Peru differs from that in other endemic regions. We used a multiplex polymerase chain reaction (PCR) assay for the detection of CPS encoding genes capable of distinguishing all 35 CPS types on Campylobacter isolates in two prospective communities based studies conducted in cohorts of children less than 59 months of age in Peru. Results showed that CPS type HS4 complex was the most prevalent, followed by HS3 complex and HS15. Differences in CPS type for symptomatology were not statistically significant. Most subjects demonstrated repeated infections over time with different CPS types, suggesting that CPS types may confer of a level of homologous protective immunity. In this dataset, some differences in CPS type distribution were observed in comparison to other low-middle income countries. Further studies need to be conducted in endemic areas to increase our knowledge of CPS type distribution and guide vaccine development.

A six-year epidemiological surveillance study in Split-Dalmatia County, Croatia: urban versus rural differences in human campylobacteriosis incidence

Data from population-based laboratory surveillance were used to examine the epidemiological pattern of campylobacteriosis in a sentinel site, Split-Dalmatia County (SDC),Croatia, from 2007 to 2012, and to evaluate the association between disease incidence and demographic, geographical, climatic, agricultural, and microbiological factors. A total of 2658 laboratory-confirmed Campylobacter infections were recorded. Overall mean incidence was 96/100,000, ranging from 61/100,000 in rural to 131/100,000 in urban areas; rates were highest in the age group 0-4 years. Overall mean and age- and sex-specific incidences were significantly higher in urban versus rural areas (p < 0.01). The number of infections peaked in early summer, and was correlated with higher average monthly temperature (r = 0.58) and lower humidity (r = - 0.27), but not with precipitation. Incidence was not associated with agricultural activities. A distinct campylobacteriosis pattern with consistently higher urban versus rural incidence was observed, which may help formulate further preventive measures.

Epidemiology of Campylobacter Infections among Children in Egypt

Campylobacter is a frequently isolated bacterial pathogen among children with diarrhea. Data are lacking on the distribution and spectrum of disease associated with Campylobacter species and Campylobacter jejuni capsular polysaccharide (CPS) types. This information is essential because current vaccine research seeks to target specific CPS types. An effective CPS-conjugate vaccine will need to cover CPS types that are both common and associated with severe disease. The US Naval Medical Research Unit-3 conducted several prospective cohort studies researching diarrheal disease in Egypt from 1995 to 2003. In total, 1,057 children were enrolled and followed to a maximum age of 36 months. We analyzed Campylobacter-positive stool samples that were collected while subjects were symptomatic, along with corresponding clinical data. Of 441 Campylobacter isolates, 322 represented primary infections (189 C. jejuni, 127 Campylobacter coli, six unspeciated). There were 19 C. jejuni CPS types identified; eight accounted for 63.5% of primary C. jejuni infections. We also screened for the presence of the type-6 secretion system (T6SS), a putative virulence determinant. The T6SS was found in 18.0% of C. coli isolates and 57.6% of C. jejuni isolates (P < 0.001), and was not uniformly distributed among CPS types (P < 0.001). Strains with the T6SS were not associated with more severe disease. Clinical presentations across species and CPS types appeared similar. This study adds to the growing epidemiological data and also provides some analysis of the clinical spectrum associated with infection by specific Campylobacter species, C. jejuni capsule types, and possible virulence determinants.

Campylobacteriosis in returning travellers and potential secondary transmission of exotic strains

SUMMARY

Multilocus sequence types (STs) were determined for 232 and 737 Campylobacter jejuni/coli isolates from Dutch travellers and domestically acquired cases, respectively. Putative risk factors for travel-related campylobacteriosis, and for domestically acquired campylobacteriosis caused by exotic STs (putatively carried by returning travellers), were investigated. Travelling to Asia, Africa, Latin America and the Caribbean, and Southern Europe significantly increased the risk of acquiring campylobacteriosis compared to travelling within Western Europe. Besides eating chicken, using antacids, and having chronic enteropathies, we identified eating vegetable salad outside Europe, drinking bottled water in high-risk destinations, and handling/eating undercooked pork as possible risk factors for travel-related campylobacteriosis. Factors associated with domestically acquired campylobacteriosis caused by exotic STs involved predominantly person-to-person contacts around popular holiday periods. We concluded that putative determinants of travel-related campylobacteriosis differ from those of domestically acquired infections and that returning travellers may carry several exotic strains that might subsequently spread to domestic populations even through limited person-to-person transmission.

Increased incidence of Campylobacter spp. infection and high rates among children, Israel

During 1999-2010, the annual incidence of Campylobacter spp. infection in Israel increased from 31.04 to 90.99 cases/100,000 population, a yearly increase of 10.24%. Children <2 years of age were disproportionally affected; incidence in this age group (356.12 cases/100,000 population) was >26-fold higher than for the 30-<50 age group.

Molecular epidemiology of human Campylobacter jejuni shows association between seasonal and international patterns of disease

We sought to explain seasonality and other aspects of Campylobacter jejuni epidemiology by integrating population genetic and epidemiological analysis in a large 3-year longitudinal, two-centre, population-based study. Epidemiological information was collected for 1505 isolates, which were multilocus sequence-typed. Analyses compared pathogen population structure between areas, over time, and between clinical presentations. Pooled analysis was performed with published international datasets. Subtype association with virulence was not observed. UK sites had nearly identical C. jejuni populations. A clade formed by ST45 and ST283 clonal complexes showed a summer peak. This clade was common in a Finnish dataset but not in New Zealand and Australian collections, countries with less marked seasonality. The UK, New Zealand and Australian collections were otherwise similar. These findings map to known in-vitro differences of this clade. This identifies a target for studies to elucidate the drivers of the summer peak in human C. jejuni infection.

Do patients with recurrent episodes of campylobacteriosis differ from those with a single disease event?

BACKGROUND

Although Campylobacter is the leading cause of reported bacterial gastro-enteritis in industrialized countries, little is known on its recurrence. The objective of this study is to describe the risk and the patient characteristics of recurrent episodes of human campylobacteriosis reported in Quebec.

METHODS

Laboratory-confirmed cases of campylobacteriosis reported in the province of Quebec, Canada, through ongoing surveillance between 1996 and 2006 were analyzed. The risk of having a recurrent episode of campylobacteriosis was described using life table estimates. Logistic regression was used to assess if gender, age and patient residential location were associated with an increased risk of recurrence.

RESULTS

Compared to the baseline risk, the risk for a recurrent disease event was higher for a period of four years and followed a decreasing trend. This increased risk of a recurrent event was similar across gender, but higher for people from rural areas and lower for children under four years of age.

CONCLUSIONS

These results may suggest the absence of durable immunity or clinical resilience following a first episode of campylobacteriosis and periodical re-exposure, at least among cases reported through the surveillance system.

Update on human Campylobacter jejuni infections

PURPOSE OF REVIEW

The present review will update the reader to the clinical, epidemiological and immunologic advances in the field of human campylobacteriosis.

RECENT FINDINGS

New advances in human campylobacteriosis include an increased appreciation of the role of Campylobacter jejuni in postinfectious sequelae, a broadened understanding of Campylobacter-associated disease burden and the interplay between host immunity and bacterial factors. Antibiotic management has also become more complex: C. jejuni has undergone a rapid increase in resistance to the fluoroquinolone antibiotics and concurrently, postinfectious irritable bowel syndrome has been associated with a longer duration of untreated infection. In anticipation of new candidate C. jejuni vaccines, progress in understanding human immune responses to infection has been made via human experimental infections. These tightly controlled studies have also increased our understanding of the natural history of campylobacteriosis as well as observations of recrudescent infection following treatment with C. jejuni-sensitive antibiotics.

SUMMARY

As one of the most common agents of bacterial gastroenteritis and a major health burden for both developing world and industrialized nations, Campylobacter infections remain a high priority for research efforts to improve prevention and management. Priorities for the future include vaccine development, pathogen-specific immunity and identification of risk factors for postinfectious sequelae.

Population-based surveillance study of Campylobacter infections in Finland

The annual incidence in 14,361 campylobacteriosis cases reported in Finland in 2002-2005 varied between 61 and 76/100,000 population. The mean incidence was highest (148/100,000) in the 25-29 years age group and lowest (range 21-24/100,000) in children aged 5-14 years and patients aged ≥75 years. The number of domestic cases was low in winter and peaked in summer. A total of 622 strains isolated from domestic infections and 785 foreign travel-related strains were serotyped. Serotypes Pen 3 and Pen 37 had the strongest association with travel-related infections (96%, P<0·001), and Pen 6,7, Pen 12 and Pen 27 were significantly associated with domestic infections (>70% domestic within each serotype, P<0·001). Pen 2 and Pen 1,44 were less common in older than in younger patients. Of domestic strains, a higher proportion of Pen 2 strains was isolated in winter (18%) compared to the other serotypes (0-10%).

Food-borne diseases - the challenges of 20 years ago still persist while new ones continue to emerge

The burden of diseases caused by food-borne pathogens remains largely unknown. Importantly data indicating trends in food-borne infectious intestinal disease is limited to a few industrialised countries, and even fewer pathogens. It has been predicted that the importance of diarrhoeal disease, mainly due to contaminated food and water, as a cause of death will decline worldwide. Evidence for such a downward trend is limited. This prediction presumes that improvements in the production and retail of microbiologically safe food will be sustained in the developed world and, moreover, will be rolled out to those countries of the developing world increasingly producing food for a global market. In this review evidence is presented to indicate that the microbiological safety of food remains a dynamic situation heavily influenced by multiple factors along the food chain from farm to fork. Sustaining food safety standards will depend on constant vigilance maintained by monitoring and surveillance but, with the rising importance of other food-related issues, such as food security, obesity and climate change, competition for resources in the future to enable this may be fierce. In addition the pathogen populations relevant to food safety are not static. Food is an excellent vehicle by which many pathogens (bacteria, viruses/prions and parasites) can reach an appropriate colonisation site in a new host. Although food production practices change, the well-recognised food-borne pathogens, such as Salmonella spp. and Escherichia coli, seem able to evolve to exploit novel opportunities, for example fresh produce, and even generate new public health challenges, for example antimicrobial resistance. In addition, previously unknown food-borne pathogens, many of which are zoonotic, are constantly emerging. Current understanding of the trends in food-borne diseases for bacterial, viral and parasitic pathogens has been reviewed. The bacterial pathogens are exemplified by those well-recognized by policy makers; i.e. Salmonella, Campylobacter, E. coli and Listeria monocytogenes. Antimicrobial resistance in several bacterial food-borne pathogens (Salmonella, Campylobacter, Shigella and Vibrio spp., methicillin resistant Staphylcoccus aureas, E. coli and Enterococci) has been discussed as a separate topic because of its relative importance to policy issues. Awareness and surveillance of viral food-borne pathogens is generally poor but emphasis is placed on Norovirus, Hepatitis A, rotaviruses and newly emerging viruses such as SARS. Many food-borne parasitic pathogens are known (for example Ascaris, Cryptosporidia and Trichinella) but few of these are effectively monitored in foods, livestock and wildlife and their epidemiology through the food-chain is poorly understood. The lessons learned and future challenges in each topic are debated. It is clear that one overall challenge is the generation and maintenance of constructive dialogue and collaboration between public health, veterinary and food safety experts, bringing together multidisciplinary skills and multi-pathogen expertise. Such collaboration is essential to monitor changing trends in the well-recognised diseases and detect emerging pathogens. It will also be necessary understand the multiple interactions these pathogens have with their environments during transmission along the food chain in order to develop effective prevention and control strategies.

Assessment of the duration of protection in Campylobacter jejuni experimental infection in humans

A human Campylobacter jejuni infection model provided controlled exposure to assess vaccine efficacy and investigate protective immunity for this important diarrheal pathogen. A well-characterized outbreak strain, C. jejuni 81-176, was investigated using a volunteer experimental infection model to evaluate the dose range and duration of protection. Healthy Campylobacter-seronegative adults received C. jejuni strain 81-176 via oral inoculation of 10(5), 10(7), or 10(9) CFU (5 adults/dose), which was followed by clinical and immunological monitoring. Based on dose range clinical outcomes, the 10(9)-CFU dose (n = 31) was used to assess homologous protection at 28 to 49 days (short-term veterans [STV]; n = 8) or 1 year (long-term veterans [LTV]; n = 7) after primary infection. An illness dose effect was observed for naïve subjects (with lower doses, 40 to 60% of the subjects were ill; with the 10(9)-CFU dose, 92% of the subjects were ill) along with complete protection for the STV group and attenuated illness for the LTV group (57%). Partial resistance to colonization was seen in STV (25% of the subjects were not infected; 3-log-lower maximum excretion level). Systemic and mucosal immune responses were robust in naïve subjects irrespective of the dose or the severity of illness. In contrast, in STV there was a lack of circulating antibody-secreting cells (ASC), reflecting the local mucosal effector responses. LTV exhibited comparable ASC responses to primary infection, and anamnestic fecal IgA responses likely contributed to self-resolving illness prior to antibiotic treatment. Campylobacter antigen-dependent production of gamma interferon by peripheral blood mononuclear cells was strongly associated with protection from illness, supporting the hypothesis that TH1 polarization has a primary role in acquired immunity to C. jejuni. This study revealed a C. jejuni dose-related increase in campylobacteriosis rates, evidence of complete short-term protection that waned with time, and immune response patterns associated with protection.

Immunity to Campylobacter: its role in risk assessment and epidemiology

Acquired immunity is an important factor in the epidemiology of campylobacteriosis in the developing world, apparently limiting symptomatic infection to children of less than two years. However, also in developed countries the highest incidence is observed in children under five years and the majority of Campylobacter infections are asymptomatic, which may be related to the effects of immunity and/or the ingested doses. Not accounting for immunity in epidemiological studies may lead to biased results due to the misclassification of Campylobacter-exposed but apparently healthy persons as unexposed. In risk assessment studies, health risks may be overestimated when immunity is neglected.

Genetic growth potential interacts with nutrition on the ability of mice to cope with Heligmosomoides bakeri infection

Artificial selection for improved productivity may reduce an animal's ability to cope with pathogens. Here, we used Roslin mice, uniquely divergently selected for high (ROH) and low (ROL) body weight, to assess interactive effects of differing growth potential and protein nutrition on host resilience and resistance. In a 2 x 2 x 6 factorial design, ROH and ROL mice were either sham-infected or infected with 250 L(3)Heligmosomoides bakeri and fed diets with 30, 80, 130, 180, 230 and 280 g crude protein per kg. The infected ROL-30 treatment resulted in clinical disease and was discontinued. In the remaining ROL mice, infection and feeding treatments did not affect growth but infection reduced weight gain in ROH-30, ROH-80 and ROH-130 mice. Although infection resulted in temporarily reduced food intake (anorexia) in both mouse lines, mean food intake over the whole experiment was reduced in ROH mice only. ROH mice excreted more worm eggs and had higher worm burdens, with relatively fewer female worms, than ROL mice. However, these resistance traits were not sensitive to dietary protein. These results support the view that selection for high growth may reduce the ability to cope with pathogens, and that improved protein nutrition may to some extent ameliorate this penalty.

Capsule polysaccharide conjugate vaccine against diarrheal disease caused by Campylobacter jejuni

The capsule polysaccharide (CPS) of Campylobacter jejuni is one of the few identified virulence determinants of this important human pathogen. Since CPS conjugate vaccines have been so effective against other mucosal pathogens, we evaluated this approach using CPSs from two strains of C. jejuni, 81-176 (HS23 and HS36 serotype complex) and CG8486 (HS4 serotype complex). The CPSs of 81-176 and CG8486 were independently linked to the carrier protein CRM(197) by reductive amination between an aldehyde(s), strategically created at the nonreducing end of each CPS, and accessible amines of CRM(197). In both cases, the CPS:CRM(197) ratio used was 2:1 by weight. Mass spectrometry and gel electrophoresis showed that on average, each glycoconjugate preparation contained, at least in part, two to five CPSs attached to one CRM(197). When administered subcutaneously to mice, these vaccines elicited robust immune responses and significantly reduced the disease following intranasal challenge with the homologous strains of C. jejuni. The CPS(81-176)-CRM(197) vaccine also provided 100% protection against diarrhea in the New World monkey Aotus nancymaae following orogastric challenge with C. jejuni 81-176.

Campylobacter immunity and coinfection following a large outbreak in a farming community

An outbreak of campylobacteriosis affected approximately one-half of 165 people attending an annual farmers' dance in Montrose, Scotland, in November 2005. Epidemiological investigations, including a cohort study (n = 164), identified chicken liver paté as the most likely vehicle of infection. Paté preparation involved deliberate undercooking of chicken livers by flash-frying, followed by mechanical homogenization. Typing of 32 Campylobacter strains (isolated from submitted stools) by multilocus sequence typing identified four distinct clades of Campylobacter jejuni. There was good agreement when isolates were typed by Penner serotyping, pulsed-field gel electrophoresis, and flaA short variable region sequencing but poorer agreement with phage and antibiotic susceptibility testing. At least three attendees were coinfected with two Campylobacter strains each. The outbreak was probably due to several livers contributing Campylobacter strains that survived undercooking and were dispersed throughout the paté. The study highlights improper culinary procedures as a potential human health risk and provides a striking counterexample to the "dominant outbreak strain" view of point source outbreaks of food-borne infections. It also demonstrates that previous exposure to biologically plausible sources of Campylobacter may confer protection against subsequent infection.

Campylobacter sugars sticking out

The amazing repertoire of glycoconjugates that are found in Campylobacter jejuni includes lipooligosaccharides mimicking human glycolipids, capsular polysaccharides with complex and unusual sugars, and proteins that are post-translationally modified with either O- or N-linked glycans. Thus, the glycome of this important food-borne pathogen is an excellent toolbox for glycobiologists to understand the fundamentals of these pathways and their role in host-microbe interactions, develop new techniques for glycobiology and exploit these pathways for novel diagnostics and therapeutics. The exciting surge in recent research activities will be summarized in this review.

Host-pathogen interactions in Campylobacter infections: the host perspective

Campylobacter is a major cause of acute bacterial diarrhea in humans worldwide. This study was aimed at summarizing the current understanding of host mechanisms involved in the defense against Campylobacter by evaluating data available from three sources: (i) epidemiological observations, (ii) observations of patients, and (iii) experimental observations including observations of animal models and human volunteer studies. Analysis of available data clearly indicates that an effective immune system is crucial for the host defense against Campylobacter infection. Innate, cell-mediated, and humoral immune responses are induced during Campylobacter infection, but the relative importance of these mechanisms in conferring protective immunity against reinfection is unclear. Frequent exposure to Campylobacter does lead to the induction of short-term protection against disease but most probably not against colonization. Recent progress in the development of more suitable animal models for studying Campylobacter infection has opened up possibilities to study the importance of innate and adaptive immunity during infection and in protection against reinfection. In addition, advances in genomics and proteomics technologies will enable more detailed molecular studies. Such studies combined with better integration of host and pathogen research driven by epidemiological findings may truly advance our understanding of Campylobacter infection in humans.

Has retail chicken played a role in the decline of human campylobacteriosis?

Between 2001 and 2006, the incidence of human Campylobacter infections decreased by 10 and 27% in Scotland and the Grampian region of Scotland, respectively. Contemporaneous collection and analyses of human and retail-chicken isolates from Grampian were carried out over a 10-week period in 2001 and again in 2006 in order to determine whether the fall in the incidence of human infections was related to the retail-chicken exposure route. Rates of carriage of Campylobacter on chicken carcasses from retail outlets in Grampian in 2001 and 2006 were estimated. Chicken-derived Campylobacter isolates from 2001 (n = 84) and 2006 (n = 105) and human-derived isolates from patients with clinical cases of infection in 2001 (n = 172) and 2006 (n = 119) were typed by multilocus sequence typing. We found no evidence for statistically significant changes in prevalence and counts per carcass. We found by rarefaction that although the degree of diversity in humans tended to be higher than that in chickens, these differences were not significant. The genetic distance between chicken and human isolates from 2001 according to sequence type, clonal complex (CC), or allele composition was not significant, whereas the distances between 2006 isolates at the CC and allele levels were significant. This difference was attributable to a lower proportion of CC-21's being found in retail-chicken isolates from 2006 than in chicken isolates from 2001. We conclude that human exposure to Campylobacter via retail chicken is important and that changes in the population structure of campylobacters in this reservoir need to be taken into account in investigating human infection.

PFGE genotyping and antimicrobial susceptibility of Campylobacter in retail poultry meat in Estonia

In the present study, the Campylobacter isolates from retail poultry meat in Estonia were sero- and genotyped, and the antimicrobial susceptibility was determined. Forty-eight chicken (36 Estonian, 12 imported) and 22 turkey (imported) Campylobacter isolates from 580 raw broiler chicken (396 Estonian, 184 imported) and 30 turkey (imported) meat samples were studied. Of the isolates, 64 were C. jejuni, 4 C. coli, and 2 Campylobacter spp. Penner serotyping of 54 C. jejuni isolates revealed 11 different serotypes, and 22% of the isolates were nontypeable by the commercial antisera. The most common serotypes O:1,44; O:21, and O:55 accounted for 28%, 13%, and 13% of the isolates, respectively. Differences in serotype distribution were seen for chicken and turkey isolates. Genotypic characterization of all Campylobacter isolates (n=70) was performed by pulsed-field gel electrophoresis (PFGE). SmaI and KpnI yielded 29 and 34 PFGE types, respectively, revealing high diversity among isolates. The serotype distribution did not show an association with the origin of the sample, but the majority of the isolates sharing a similar PFGE genotype originated from one country. High levels of resistance to ciprofloxacin (66%), nalidixic acid (66%), tetracycline (44%), ampicillin (34%), and erythromycin (14%) were detected among the 70 Campylobacter isolates. The simultaneous resistance to two or three antimicrobial agents occurred in 60% of the isolates. The Campylobacter isolates from turkey meat had higher resistance to ampicillin, ciprofloxacin, nalidixic acid, and tetracycline than those from chicken meat. None of the chicken isolates were resistant to gentamicin, and no turkey isolates to erythromycin or gentamicin.