Acidification of drinking water inhibits indirect transmission, but not direct transmission of Campylobacter between broilers.

In this study the effect of acidification of the drinking water of broiler chickens on both direct and indirect transmission of Campylobacter was evaluated. In the direct transmission experiment both susceptible and inoculated animals were housed together. In the indirect transmission experiment the susceptible animals were spatially separated from the inoculated animals and no direct animal to animal contact was possible. The transmission parameter ß was estimated for the groups supplied with acidified drinking water and for the control groups. The results showed that acidification of the drinking water had no effect on direct transmission (ß=3.7 day(-1) for both control and treatment). Indirect transmission however was influenced by acidification of the drinking water. A significant decrease in transmission was observed (p<0.05), with control vs. treatment point estimates being ß=0.075 day(-1) vs. ß=0.011 day(-1). Apart from providing quantitative estimations of both direct and indirect transmission of Campylobacter in broilers, this study also demonstrates the use of an experimental setup for indirect transmission of Campylobacter between broilers to assess the efficacy of candidate measures to reduce transmission.

Prevalence of Salmonella in the broiler supply chain in The Netherlands.

This article presents detailed information on Salmonella prevalence throughout the broiler supply chain in The Netherlands, based on results from a national monitoring program. Data were collected during the period 2002 through 2005 and from six sampling points in the chain, covering hatchery up to and including processing. Trends in Salmonella prevalence over years and seasons were analyzed as well as the effect of slaughterhouse capacity on these trends. In addition, correlations between the occurrence of Salmonella at the various sampling points were calculated. The results showed a decreasing trend of Salmonella prevalence from 2002 through 2005 at all sampling points. A seasonal effect on the occurrence of Salmonella was found at the broiler farm, with a higher prevalence during the third and fourth quarter of the year (July through December). The higher the capacity of the slaughterhouse, the lower Salmonella prevalence on arrival at the slaughterhouse and the higher the prevalence at the end of slaughter and the end of processing. The detailed insights obtained in this study could be used to focus future field and experimental research on the prevention and control of Salmonella in the broiler supply chain. Results presented could also be used in risk assessment studies.

Campylobacter prevalence in the broiler supply chain in the Netherlands.

After a national control program, data on Campylobacter prevalence in the broiler supply chain in the Netherlands were gathered for 3 sampling points: departure of broiler farm and arrival and departure of the slaughterhouse. Monitoring data from this control program for 2002 to 2005 were analyzed to find correlations and possible trends in the data. As expected, the greatest correlations were found between adjacent sampling points. A high correlation was expected between number of animals slaughtered and Campylobacter prevalence, because it is assumed that larger companies will have greater hygiene standards due to better implication of food safety regulations. However, statistical analysis showed that there was no clear correlation between company size and Campylobacter prevalence. Data analysis further identified an increasing trend in Campylobacter prevalence at departure of slaughterhouse from 2002 to 2005 with strong seasonality at all 3 sampling points. Measures to control Campylobacter, therefore, need to be reconsidered and possibly intensified to achieve a reduction in Campylobacter positives.

Presence of Salmonella and Campylobacter spp. in wild small mammals on organic farms.

The presence of Salmonella and Campylobacter spp. in rodents and insectivores (n = 282) was investigated on organic farms. Infections were encountered in house mice (8 of 83 Campylobacter positive and 1 of 83 Salmonella sp. strain Livingstone positive) and brown rats (1 of 8 Campylobacter positive) but not in other species. No shared Campylobacter genotypes were found between rodent and pig manure isolates. Effective on-farm rodent management is recommended.

Quantifying transmission of Campylobacter spp. among broilers.

Campylobacter species are frequently identified as a cause of human gastroenteritis, often from eating or mishandling contaminated poultry products. Quantitative knowledge of transmission of Campylobacter in broiler flocks is necessary, as this may help to determine the moment of introduction of Campylobacter in broiler flocks more precisely. The aim of this study was to determine the transmission rate parameter in broiler flocks. Four experiments were performed, each with four Campylobacter-inoculated chicks housed with 396 contact chicks per group. Colonization was monitored by regularly testing fecal samples for Campylobacter. A mathematical model was used to quantify the transmission rate, which was determined to be 1.04 new cases per colonized chick per day. This would imply that, for example, in a flock of 20,000 broilers, the prevalence of Campylobacter would increase from 5% to 95% within 6 days after Campylobacter introduction. The model and the estimated transmission rate parameter can be used to develop a suitable sampling scheme to determine transmission in commercial broiler flocks, to estimate whether control measures can reduce the transmission rate, or to estimate when Campylobacter was introduced into a colonized broiler flock on the basis of the time course of transmission in the flock.

Computer-assisted analysis and epidemiological value of genotyping methods for Campylobacter jejuni and Campylobacter coli.

For epidemiological tracing of the thermotolerant Campylobacter species C. jejuni and C. coli, reliable and highly discriminatory typing techniques are necessary. In this study the genotyping techniques of flagellin typing (flaA typing), pulsed-field gel electrophoresis (PFGE), automated ribotyping, and amplified fragment length polymorphism (AFLP) fingerprinting were compared. The following aspects were compared: computer-assisted analysis, discriminatory power, and use for epidemiological typing of campylobacters. A set of 50 campylobacter poultry isolates from The Netherlands and neighboring countries was analyzed. Computer-assisted analysis made cluster analysis possible and eased the designation of different genotypes. AFLP fingerprinting was the most discriminatory technique, identifying 41 distinct genotypes, while PFGE identified 38 different types, flaA typing discriminated 31 different types, and ribotyping discriminated 26 different types. Furthermore, AFLP analysis was the most suitable method for computer-assisted data analysis. In some cases combining the results of AFLP fingerprinting, PFGE, and flaA typing increased our ability to differentiate strains that appeared genetically related. We conclude that AFLP is a highly discriminatory typing method and well suited for computer-assisted data analysis; however, for optimal typing of campylobacters, a combination of multiple typing methods is needed.

Aspects of epidemiology of Campylobacter in poultry.

Campylobacter bacteria, which in humans cause infections with severe symptoms of diarrhoea, are mainly transmitted by food, especially poultry meat products. Several studies on Campylobacter colonization in breeders, laying hens, and broilers were carried out. Isolates were serotyped, using a modification of the Penner system, in order to identify epidemiological factors contributing to the Campylobacter colonization of poultry. No evidence was found for vertical transmission from breeder flocks via the hatchery to progeny, nor for horizontal transmission from one broiler flock to the next via persistent contamination of the broiler house. The major route for Campylobacter colonization of poultry is horizontal transmission from the environment. Pigs and poultry flocks (broilers, laying hens, and breeders), and to a lesser extent sheep and cattle, were found to be potential sources of Campylobacter contamination. Horizontal intervention procedures at the farm level have to be studied further to evaluate the effectiveness of strict hygienic practices during the whole production period. Screening for antibiotic resistance revealed 181 out of 617 Campylobacter isolates (29%), originating from a large number of broiler flocks, to be quinolone resistant. Quinolone treatment of Campylobacter colonized broiler chicks was found to induce quinolone resistance under experimental conditions. Therefore, quinolone treatment should not be seen as an answer to the problem of Campylobacter colonization in poultry flocks.

Antibiotic susceptibility of campylobacter isolates from sewage and poultry abattoir drain water.

In this study, the in vitro susceptibility of 209 campylobacter strains to the quinolones nalidixic acid, flumequine, ciprofloxacin, enrofloxacin, and to ampicillin, tetracycline and erythromycin was tested by the disk diffusion method. The strains were isolated from poultry abattoir effluent (DWA) and two sewage purification plants (SPA and SPB). Sewage purification plant SPA received mixed sewage, including that from a poultry abattoir, whereas SPB did not receive sewage from any meat-processing industry. The quinolone resistance of the DWA isolates ranged from 28% for enrofloxacin to 50% for nalidixic acid. The strains isolated from the sewage purification plants were more susceptible to the quinolones with a range of 11-18% quinolone resistance for SPB isolates to 17-33% quinolone resistance for SPA isolates. The susceptibility criteria as recommended by National Committee Clinical Laboratory Standards (USA) cannot readily be employed for campylobacter isolates. This investigation shows that the resistance of campylobacter bacteria is highest in the plant receiving sewage from a poultry slaughterhouse. Monitoring of antibiotic resistance of aquatic Campylobacter spp. is important, as surface waters are recognized as possible sources of infection.

Penner serotyping of Campylobacter isolates from poultry, with absorbed pooled antisera.

The Penner serotyping system, based on detection of heat-stable antigens with a passive haemagglutination technique, was used in studies on Campylobacter epidemiology in poultry. Preparation of specific antisera by absorption allowed the use of pooled antisera. Over 80% of the Campylobacter isolates were typable with this modified Penner serotyping system. Typability of strains was clearly affected by storage of the strains before actual typing. Extracted antigens appeared to be stable for at least 6 months at 4 degrees C. Therefore, it is advisable to store extracted antigens from freshly isolated Campylobacter strains instead of reculturing frozen-stored strains, when actual typing cannot be performed directly after primary isolation. Untypability of isolates may partly be explained by the detection of Campylobacter serovars not yet represented in the serotyping system. Experiments on repeated serotyping of several Campylobacter strains did not suggest any serovar instability within the strains.

Discrepancy between Penner serotyping and polymerase chain reaction fingerprinting of Campylobacter isolated from poultry and other animal sources.

Thirty-four Campylobacter jejuni or coli strains, isolated from various livestock and darkling beetles from two Dutch poultry farms during different broiler production cycles, were subjected to Penner serotyping and polymerase chain reaction (PCR) fingerprint analysis. Ten different Penner serotypes were determined in the isolates. Visual scoring of the PCR fingerprints resulted in 14 clearly different profiles. Some strains with identical Penner serotypes exhibited different PCR fingerprints and conversely strains with different serotypes produced identical PCR fingerprints. Discrepancies between Penner serotyping and PCR fingerprinting were most obvious between isolates from different animal sources. Indications for the occurrence of genomic rearrangements were found. The inconsistency between serotyping and fingerprinting of Campylobacter strains suggests that conventional typing methods should be used in combination with fingerprinting if the epidemiological factors that contribute to Campylobacter colonization of live chickens are to be assessed reliably.

Epidemiology of Campylobacter spp. at two Dutch broiler farms.

Broiler flocks on two Dutch poultry farms were screened weekly for the presence of campylobacter in fresh caecal droppings during eight consecutive production cycles. Hatchery and fresh litter samples were taken at the start of each new cycle. Water, feed, insects, and faeces of domestic animals, present on the farms were also included in the sampling. Penner serotyping of isolates was used to identify epidemiological factors that contribute to campylobacter colonization in the broiler flocks. Generally, broiler flocks became colonized with campylobacter at about 3-4 weeks of age with isolation percentages of 100%, and stayed colonized up to slaughter. A similar pattern of serotypes was found within the various broiler houses on one farm during one production cycle. New flocks generally showed also a new pattern of serotypes. Most serotypes isolated from the laying hens, pigs, sheep and cattle were different from those isolated from the broilers at the same time. Campylobacter serotypes from darkling beetles inside the broiler houses were identical to the ones isolated from the broilers. No campylobacter was isolated from any of the hatchery, water, feed or fresh litter samples. Conclusive evidence of transmission routes was not found, but results certainly point towards horizontal transmission from the environment. Horizontal transmission from one broiler flock to the next one via a persistent contamination within the broiler house, as well as vertical transmission from breeder flocks via the hatchery to progeny, did not seem to be very likely.

Campylobacter bacteria in breeder flocks.

Nine Dutch breeder farms with a total of 43 separately housed flocks were examined for the presence of Campylobacter spp. and Salmonella spp. Penner serotyping of Campylobacter isolates was used to identify epidemiological factors contributing to the Campylobacter infection of these breeder flocks. Campylobacter was isolated from 29 of the 43 flocks (67%), and Salmonella was isolated from 12 flocks (28%). Two of the nine farms were both Campylobacter- and Salmonella-free at the time of sampling. Two other farms were Salmonella-free but Campylobacter-positive. A total of 330 Campylobacter isolates were serotyped, and 19 different Campylobacter serotypes were isolated in this study. Some similarities were observed in the patterns of serotype occurrence in houses of a given farm. Campylobacter colonization of breeder flocks indicates a potential role of vertical transmission via the egg to progeny. However, serotyping results did not support a vertical transmission route via the egg. Therefore, breeder flocks have to be recognized as another reservoir of Campylobacter, and it is more appropriate to consider them a potential risk factor in horizontal transmission routes.

In vitro susceptibility of Campylobacter and Salmonella isolates from broilers to quinolones, ampicillin, tetracycline, and erythromycin.

Recently, an increased resistance of Campylobacter to fluoroquinolones, a newer class of antimicrobial agents in both human and veterinary medicine, has been reported. Campylobacter isolates (617) from 150 broiler flocks were tested for their susceptibility to cephalothin (control), ampicillin, tetracycline, erythromycin, and the quinolones nalidixic acid, flumequine, enrofloxacin, and ciprofloxacin by a disc diffusion method. Almost complete cross-resistance was found between the quinolones tested. Campylobacter isolates (181, 29%), originating from 55 flocks (37%), were quinolone resistant. Salmonella isolates (94) from 40 flocks were also tested for their antimicrobial susceptibility. Eight isolates (8.5%), from three broiler flocks (7.5%), showed resistance to nalidixic acid and flumequine (and tetracycline), but not to ciprofloxacin or enrofloxacin.

Cecal carriage of Campylobacter and Salmonella in Dutch broiler flocks at slaughter: a one-year study.

From March 1992 to March 1993, 187 Dutch broiler flocks were screened to assess their Campylobacter and Salmonella carriage. Every 4 wk at least 10 flocks, at three different slaughterhouses, were screened for presence of these bacteria. Twenty-five cecal samples were taken from each flock. Campylobacter spp. were isolated from 153 out of 187 broiler flocks (82%). Campylobacter carriage of flocks showed seasonal variation, with the highest contamination rate (100%) during the period June to September and the lowest (50%) in March. Salmonella carriage of the flocks did not show a distinct seasonal variation. Salmonella spp. were isolated from 49 out of 181 broiler flocks (27%). A positive correlation was found between Campylobacter and Salmonella colonization within flocks. Data on farming conditions and husbandry practices were studied to identify possible risk factors for Campylobacter and Salmonella colonization of Dutch broiler flocks.

Prevention of colonization by Salmonella enteritidis PT4 in broiler chickens.

Field experiments in The Netherlands and in Scandinavian countries have shown that an undefined microflora originating from SPF adult poultry will reduce considerably the colonization of young chicks by Salmonella. A commercial product from this so-called Nurmi concept, Broilact, was studied for its effectiveness in preventing infection of broilers with Salmonella enteritidis PT4 (S.e.). Two trials were carried out, in which the birds were exposed to S.e. via 'seeder' birds placed among them. The trial period was 21 days and each week one third of the chicks was killed and their caecal contents examined for salmonellas. The results of the first trial can be summarized as follows. (1) After 2 weeks the number of 'seeder' birds carrying the Salmonella decreased sharply; (2) the proportion of infected chicks in the Broilact-treated group was lower than in the non-treated group; (3) Counts of S.e. in the non-treated group were higher than in the Broilact group. Results of the second trial were comparable, although no salmonellas could be isolated after the second week.