Chickens and cattle as sources of sporadic domestically acquired Campylobacter jejuni infections in Finland

Genomic Relatedness, Antibiotic Resistance and Virulence Traits of Campylobacter jejuni HS19 Isolates From Cattle in China Indicate Pathogenic Potential

Although campylobacteriosis is a zoonotic foodborne illness, high-risk isolates from animal sources are rarely characterized, and the pathogenic potential of zoonotic strains remains an obstacle to effective intervention against human infection. HS19 has been acknowledged as a maker serotype represented by Campylobacter jejuni (C. jejuni) isolates from patients with post-infection Guillain-Barré syndrome (GBS), which is circulation in developed countries. However, a previous serotype epidemiological study of C. jejuni isolates in an animal population revealed that HS19 was also prevalent in isolates from cattle in China. In this study, to investigate the hazardous potential of zoonotic strains, 14 HS19 isolates from cattle were systematically characterized both by genotype and phenotype. The results showed that all of these cattle isolates belonged to the ST-22 complex, a high-risk lineage represented by 77.2% HS19 clinical isolates from patients worldwide in the PubMLST database, indicating that the ST-22 complex is the prominent clonal complex of HS19 isolates, as well as the possibility of clonal spread of HS19 isolates across different regions and hosts. Nevertheless, these cattle strains clustered closely with the HS19 isolates from patients, suggesting a remarkable phylogenetic relatedness and genomic similarity. Importantly, both tetracycline genes tet(O) and gyrA (T86I) reached a higher proportional representation among the cattle isolates than among the human clinical isolates. A worrying level of multidrug resistance (MDR) was observed in all the cattle isolates, and two MDR profiles of the cattle isolates also existed in human clinical isolates. Notably, although shared with the same serotype HS19 and sequence type ST-22, 35.7% of cattle isolates induced severe gastrointestinal pathology in the IL-10^–/– C57BL/6 mice model, indicating that some bacteria could change due to host adaptation to induce a disease epidemic, thus the associated genetic elements deserve further investigation. In this study, HS19 isolates from cattle were first characterized by a systematic evaluation of bacterial genomics and in vitro virulence, which improved our understanding of the potential zoonotic hazard from food animal isolates with high-risk serotypes, and provided critical information for the development of targeted C. jejuni mitigation strategies.

Tracing isolates from domestic human Campylobacter jejuni infections to chicken slaughter batches and swimming water using whole-genome multilocus sequence typing

Campylobacter jejuni is the leading cause of bacterial gastroenteritis and chicken is considered a major reservoir and source of human campylobacteriosis. In this study, we investigated temporally related Finnish human (n=95), chicken (n=83) and swimming water (n=20) C. jejuni isolates collected during the seasonal peak in 2012 using multilocus sequence typing (MLST) and whole-genome MLST (wgMLST). Our objective was to trace domestic human C. jejuni infections to C. jejuni isolates from chicken slaughter batches and swimming water. At MLST level, 79% of the sequence types (STs) of the human isolates overlapped with chicken STs suggesting chicken as an important reservoir. Four STs, the ST-45, ST-230, ST-267 and ST-677, covered 75% of the human and 64% of the chicken isolates. In addition, 50% of the swimming water isolates comprised ST-45, ST-230 and ST-677. Further wgMLST analysis of the isolates within STs, accounting their temporal relationship, revealed that 22 of the human isolates (24%) were traceable back to C. jejuni positive chicken slaughter batches. None of the human isolates were traced back to swimming water, which was rather sporadically sampled. The highly discriminatory wgMLST, together with the patient background information and temporal relationship data with possible sources, offers a new, accurate approach to trace back the origin of domestic campylobacteriosis. Our results suggest that potentially a substantial proportion of campylobacteriosis cases during the seasonal peak most probably are due to other sources than chicken meat consumption. These findings warrant further wgMLST-based studies to reassess the role of other reservoirs in the Campylobacter epidemiology both in Finland and elsewhere.

Antimicrobial Resistance and Multilocus Sequence Types of Finnish Campylobacter jejuni Isolates from Multiple Sources

Antimicrobial susceptibility was determined for 805 domestic Campylobacter jejuni isolates obtained from broilers (n = 459), bovines (n = 120), human patients (n = 95), natural waters (n = 80), wild birds (n = 35) and zoo animals/enclosures (n = 16) with known multilocus sequence types (MLST) for 450 isolates. The minimum inhibitory concentration (MIC) values for erythromycin, tetracycline, streptomycin, gentamicin and the quinolones ciprofloxacin and nalidixic acid were determined with the VetMIC method. MICs were compared with MLST types to find possible associations between sequence type and resistance. The proportions of resistant isolates were 5% (broilers), 6.3% (natural waters), 11.4% (wild birds), 11.6% (human patients), 16.7% (bovines) and 31.3% (zoo). The most common resistance among the human and bovine isolates was quinolone resistance alone while resistance to streptomycin alone was most often detected among the broiler isolates and tetracycline resistance was most commonly observed in the wild bird, water and zoo isolates. No or negligible resistance to erythromycin or gentamicin was detected. In all data, 12/26 of the tetracycline-resistant isolates were also resistant to streptomycin (P < 0.001) and the clonal complex (CC) ST-1034 CC showed a high proportion of 75% (9/12) of tetracycline-resistant isolates, most originating from the zoo and broilers with closely associated MLST types from these sources. No association between quinolone resistance and MLST type was seen. The low percentage of resistant isolates among the domestic Campylobacter infections is most probably due to the long-term controlled use of antimicrobials. However, the higher percentage of tetracycline resistance observed among the zoo isolates could present a risk for zoo visitors of acquisition of resistant C. jejuni. The resistance pattern of tetracycline and streptomycin most often found in ST-1034 CC could indicate a common resistance acquisition mechanism commonly present in this CC. Overall, MLST typing was found to be a useful method in recognition of potential genetic lineages associated with resistance.

A five-year study on prevalence and antimicrobial resistance of Campylobacter from poultry carcasses in Poland

During 2009-2013 a total of 2114 swab samples collected from broiler carcasses in all 16 voivodeships (administrative districts) of Poland were examined for the presence of Campylobacter jejuni and Campylobacter coli. The antimicrobial resistance of the isolates to ciprofloxacin, tetracycline and erythromycin using the MIC method was also tested. It was found that 1151 (54.4%) carcasses were contaminated with Campylobacter, with 50% of C. jejuni and C. coli species isolated from positive samples. The temporal trend in the prevalence of Campylobacter-positive samples demonstrated that the highest percentage of carcasses was contaminated during the first year of the survey (70.5%) whereas in the last year (2013) only 36.3% of broilers contained these bacteria. Antimicrobial resistance analysis showed that overall 939 (81.6%) of isolates were resistant to ciprofloxacin, 646 (56.1%) to tetracycline but only 28 (2.4%) to erythromycin. Significant differences in resistance profiles between C. jejuni and C. coli were observed with greater resistance level observed in the latter species. Furthermore, a significant increase in the percentage of C. jejuni resistant to ciprofloxacin (from 59.6% in 2009 to 85.9% in 2014) and to tetracycline (from 23.2% to 70.4%, respectively) was identified. Only 20 (1.7%) Campylobacter isolates displayed a multiresistance pattern.

Predominant Campylobacter jejuni sequence types persist in Finnish chicken production

Consumption and handling of chicken meat are well-known risk factors for acquiring campylobacteriosis. This study aimed to describe the Campylobacter jejuni population in Finnish chickens and to investigate the distribution of C. jejuni genotypes on Finnish chicken farms over a period of several years. We included 89.8% of the total C. jejuni population recovered in Finnish poultry during 2004, 2006, 2007, 2008, and 2012 and used multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) to characterize the 380 isolates. The typing data was combined with isolate information on collection-time and farm of origin. The C. jejuni prevalence in chicken slaughter batches was low (mean 3.0%, CI95% [1.8%, 4.2%]), and approximately a quarter of Finnish chicken farms delivered at least one positive chicken batch yearly. In general, the C. jejuni population was diverse as represented by a total of 63 sequence types (ST), but certain predominant MLST lineages were identified. ST-45 clonal complex (CC) accounted for 53% of the isolates while ST-21 CC and ST-677 CC covered 11% and 9% of the isolates, respectively. Less than half of the Campylobacter positive farms (40.3%) delivered C. jejuni-contaminated batches in multiple years, but the genotypes (ST and PFGE types) generally varied from year to year. Therefore, no evidence for a persistent C. jejuni source for the colonization of Finnish chickens emerged. Finnish chicken farms are infrequently contaminated with C. jejuni compared to other European Union (EU) countries, making Finland a valuable model for further epidemiological studies of the C. jejuni in poultry flocks.

Comparison of Campylobacter jejuni pulsotypes isolated from humans and poultry in Split and Dalmatia County, Croatia

Consumption of poultry is considered to be an important source of human infection with Campylobacter. In the period from 2008 to 2010, 50 isolates of Campylobacter jejuni from human faeces were analysed and compared with 61 isolates from poultry by pulsed field gel electrophoresis using SmaI and KpnI. Based on the analysis of SmaI macrorestriction profiles, 86 isolates (77.5 %) were assigned to 15 S clusters: 31 (62 %) from humans and 55 from poultry (90.2 %). Altogether 21 isolates (19 %) exhibited macrorestriction profiles common to both humans and poultry after restriction with SmaI and KpnI. A total of five identical pulsotypes were isolated from both poultry and patients and one of them appeared in eight different locations in the time interval of one year. These results indicate that poultry could be an important source of Campylobacter infection in Split and Dalmatia County which is the biggest County in Croatia and the most important tourist destination.

Campylobacter jejuni prevalence and hygienic quality of retail bovine ground meat in Finland

Detection of common genotypes of Campylobacter jejuni among Finnish human and bovine isolates, suggested that bovines may be a source for zoonotic Camp. jejuni infection. In addition, a Finnish epidemiological study implied the tasting and eating raw or undercooked beef as risk factors for acquiring campylobacteriosis. We therefore performed a study on the occurrence of Camp. jejuni in retail bovine ground meat in Helsinki by the use of both cultivation and PCR. During 2011 and 2012, 175 bovine ground meat samples were collected. None of the samples were Campylobacter positive by cultivation, and only one sample (0.6%) was Camp. jejuni positive by the use of PCR on template extracted directly from ground meat. According to our findings, Finnish bovine ground meat is an unlikely source for human campylobacteriosis. Additionally, the hygienic quality of bovine ground meat at retail level was screened and found to be good when monitored by aerobic micro-organisms, total thermotolerant coliforms and Eshericha coli.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides the first data on the occurrence of the zoonotic pathogen Campylobacter jejuni in Finnish bovine ground meat. This knowledge is important as part of future Campylobacter risk assessment, management and monitoring programs, particularly when assessing the relative attribution of poultry, pork and bovine meat to the burden of human campylobacteriosis. According to our results, Finnish bovine ground meat at retail level is of good hygienic quality.

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.

Respiratory proteins contribute differentially to Campylobacter jejuni's survival and in vitro interaction with hosts' intestinal cells

Background

The genetic features that facilitate Campylobacter jejuni’s adaptation to a wide range of environments are not completely defined. However, whole genome expression studies showed that respiratory proteins (RPs) were differentially expressed under varying conditions and stresses, suggesting further unidentified roles for RPs in C. jejuni’s adaptation. Therefore, our objectives were to characterize the contributions of selected RPs to C. jejuni’s i- key survival phenotypes under different temperature (37°C vs. 42°C) and oxygen (microaerobic, ambient, and oxygen-limited/anaerobic) conditions and ii- its interactions with intestinal epithelial cells from disparate hosts (human vs. chickens).

Results

C. jejuni mutant strains with individual deletions that targeted five RPs; nitrate reductase (ΔnapA), nitrite reductase (ΔnrfA), formate dehydrogenase (ΔfdhA), hydrogenase (ΔhydB), and methylmenaquinol:fumarate reductase (ΔmfrA) were used in this study. We show that only the ΔfdhA exhibited a decrease in motility; however, incubation at 42°C significantly reduced the deficiency in the ΔfdhA’s motility as compared to 37°C. Under all tested conditions, the ΔmfrA showed a decreased susceptibility to hydrogen peroxide (H₂O₂), while the ΔnapA and the ΔfdhA showed significantly increased susceptibility to the oxidant as compared to the wildtype. Further, the susceptibility of the ΔnapA to H₂O₂ was significantly more pronounced at 37°C. The biofilm formation capability of individual RP mutants varied as compared to the wildtype. However, the impact of the deletion of certain RPs affected biofilm formation in a manner that was dependent on temperature and/or oxygen concentration. For example, the ΔmfrA displayed significantly deficient and increased biofilm formation under microaerobic conditions at 37°C and 42°C, respectively. However, under anaerobic conditions, the ΔmfrA was only significantly impaired in biofilm formation at 42°C. Additionally, the RPs mutants showed differential ability for infecting and surviving in human intestinal cell lines (INT-407) and primary chicken intestinal epithelial cells, respectively. Notably, the ΔfdhA and the ΔhydB were deficient in interacting with both cell types, while the ΔmfrA displayed impairments only in adherence to and invasion of INT-407. Scanning electron microscopy showed that the ΔhydB and the ΔfdhA exhibited filamentous and bulging (almost spherical) cell shapes, respectively, which might be indicative of defects in cell division.

Conclusions

We conclude that the RPs contribute to C. jejuni’s motility, H₂O₂ resistance, biofilm formation, and in vitro interactions with hosts’ intestinal cells. Further, the impact of certain RPs varied in response to incubation temperature and/or oxygen concentration. Therefore, RPs may facilitate the prevalence of C. jejuni in a variety of niches, contributing to the pathogen’s remarkable potential for adaptation.

From farm to fork follow-up of thermotolerant campylobacters throughout the broiler production chain and in human cases in a Hungarian county during a ten-months period

A study tracking thermotolerant campylobacters from the setting of the broilers throughout the whole rearing period, slaughter and sale of chicken products in five consecutive broiler rotations of the same henhouse as well as in two different other farms was conducted in a well-defined geographic area (Hajdú-Bihar county, Hungary) between March 2006 and Feb 2007. All notified cases of human campylobacteriosis in this area during the study period were also included. One hundred and one, 44, 23 and 282 Campylobacter jejuni and 13, 15, 20 and 60C. coli were isolated from broiler houses, slaughterhouses, retail shops and human samples, respectively. Sixty-two isolates collected from broilers or their environment selected from different flocks (57C. jejuni, 5C. coli), 92 isolates collected from abattoirs and retail shops (72C. jejuni, 20C. coli), as well as 85 randomly selected human isolates (74C. jejuni, 11C. coli) were subjected to PFGE analysis using restriction enzymes KpnI and SmaI. Sixty-six of the isolates produced unique Sma-Kpn profiles; the majority (46) of these were of human origin. The remaining isolates formed PFGE clusters of between 2-25 isolates with 14 (12C. jejuni and 2C. coli) main clusters comprised of five or more isolates with identical KpnI-SmaI patterns. Two genetic clones of C. jejuni (clone A, n=25; clone B, n=20) included 18% of isolates from different sources. Generally, isolates from one cluster were found in 1-3 different flocks, notably, clone B was present in three rotations including those from the two independent farms. Six of the seven investigated flocks had one or two characteristic prevalent clones. Transmission of clones between consecutive flocks was frequently seen. Spread of both C. jejuni and C. coli was traced multiple times along the food chain; eight C. jejuni, but no C. coli clones were detected both in broilers and humans. These data suggest that broilers were the major source for C. jejuni but not for C. coli in the studied area and period. For C. jejuni the carryover of strains between consecutive flocks may be a common event, but the strain is eventually replaced by another and consecutive carryover events seem to be infrequent. The majority of the human disease was due to nonepidemic strains; some clones were transmitted from more than one broiler flocks (including epidemiologically unrelated flocks) to humans multiple times.

Identification of persistent subtypes of Campylobacter jejuni by pulsed-field gel electrophoresis in Finland

The genetic diversity of Campylobacter jejuni strains isolated from Finnish patients was studied by typing 508 strains by pulsed-field gel electrophoresis: 311 were isolated from domestically acquired infections and 197 from travel-related infections. The strains were systematically selected from a larger collection of previously serotyped strains isolated during two 1-year sampling periods. The four most common SmaI profiles accounted for 45% of the domestic strains but only 3% of the travel-related strains. Of the domestic strains, 69% belonged to SmaI subtypes found during both sampling periods. The predominating SmaI subtypes and strains that were not digested by SmaI were typed by KpnI. Analyzing the temporal diversity of the pulsed-field gel electrophoresis profiles revealed six common persistent SmaI/KpnI subtypes among the domestic strains. Five of them have been identified in cattle, and two in chickens with a temporal association with human infections.

Multilocus sequence types of Finnish bovine Campylobacter jejuni isolates and their attribution to human infections

BACKGROUND

Campylobacter jejuni is the most common bacterial cause of human gastroenteritis worldwide. Due to the sporadic nature of infection, sources often remain unknown. Multilocus sequence typing (MLST) has been successfully applied to population genetics of Campylobacter jejuni and mathematical modelling can be applied to the sequence data. Here, we analysed the population structure of a total of 250 Finnish C. jejuni isolates from bovines, poultry meat and humans collected in 2003 using a combination of Bayesian clustering (BAPS software) and phylogenetic analysis.

RESULTS

In the first phase we analysed sequence types (STs) of 102 Finnish bovine C. jejuni isolates by MLST and found a high diversity totalling 50 STs of which nearly half were novel. In the second phase we included MLST data from domestic human isolates as well as poultry C. jejuni isolates from the same time period. Between the human and bovine isolates we found an overlap of 72.2%, while 69% of the human isolates were overlapping with the chicken isolates. In the BAPS analysis 44.3% of the human isolates were found in bovine-associated BAPS clusters and 45.4% of the human isolates were found in the poultry-associated BAPS cluster. BAPS reflected the phylogeny of our data very well.

CONCLUSIONS

These findings suggest that bovines and poultry were equally important as reservoirs for human C. jejuni infections in Finland in 2003. Our results differ from those obtained in other countries where poultry has been identified as the most important source for human infections. The low prevalence of C. jejuni in poultry flocks in Finland could explain the lower attribution of human infection to poultry. Of the human isolates 10.3% were found in clusters not associated with any host which warrants further investigation, with particular focus on waterborne transmission routes and companion animals.

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.