Environmental contamination by vancomycin resistant enterococci (VRE) in Swedish broiler production

Background

Vancomycin resistant enterococci are a frequent cause of nosocomial infections and their presence among farm animals is unwanted. Using media supplemented with vancomycin an increase in the proportion of samples from Swedish broilers positive for vancomycin resistant enterococci has been detected. The situation at farm level is largely unknown. The aims of this study were to obtain baseline knowledge about environmental contamination with vancomycin resistant enterococci in Swedish broiler production and the association between environmental contamination and colonisation of birds.

Methods

Environmental samples were taken before, during and after a batch of broilers at three farms. Samples were cultured both qualitatively and semi-quantitatively for vancomycin resistant enterococci. In addition, caecal content from birds in the batch following at each farm was cultured qualitatively for vancomycin resistant enterococci.

Results

The number of samples positive for vancomycin resistant enterococci varied among the farms. Also the amount of vancomycin resistant enterococci in the positive samples and the proportion of caecal samples containing vancomycin resistant enterococci varied among the farms. Still, the temporal changes in environmental contamination followed a similar pattern in all farms.

Conclusion

Vancomycin resistant enterococci persist in the compartments even after cleaning and the temporal changes in environmental contamination were similar among farms. There were however differences among farms regarding both degree of contamination and proportion of birds colonized with vancomycin resistant enterococci. The proportion of colonized birds and the amount of vancomycin resistant enterococci in the compartments seems to be associated. If the factor(s) causing the differences among farms could be identified, it might be possible to reduce both the risk for colonisation by vancomycin resistant enterococci of the subsequent flock and the risk for spread of vancomycin resistant enterococci via the food chain to humans.     

Distribution and genetic relatedness of vancomycin-resistant enterococci (VRE) isolated from healthy slaughtered chickens in Hungary from 2001 to 2004

The presence of the vanA gene was determined in enterococci from healthy poultry, originating from the Hungarian resistance monitoring system between 2001 and 2004. Enterococci (n = 562) were collected from intestinal samples of slaughtered broiler chickens. The presence of van genes was detected by polymerase chain reaction (PCR). The vancomycin-resistant enterococcus (VRE) strains carried only the vanA gene. Genus- and species-level identification of the vanA gene carrier strains was carried out by PCR using specific primers. In 2001, 25 out of the 289 isolated strains (8.6%) were vanA carriers (1 Enterococcus mundtii, 13 E. durans and 11 E.faecium). In 2002 (n = 87), 20 (23%) strains were vanA positive (11 E. durans and 9 E. faecium). In 2003 and 2004, none of the strains (n = 95 and 91, respectively) were positive for the most common van genes. In 2003, there was only one strain for which higher minimum inhibitory concentrations (MIC) of vancomycin (4 mg/L) and teicoplanin (8 mg/L) were found. In 2004 there were three strains for which the MIC of vancomycin was 8 mg/L, and 2 strains and 1 strain with teicoplanin MICs of 4 mg/L and 8 mg/L, respectively. The potential similarity of these strains was studied by pulsed-field gel electrophoresis (PFGE). The VRE strains were not closely related to one another. The annual data of vancomycin resistance indicate an association between the recovery of vancomycin-resistant enterococci and the use of avoparcin in animal feeds. This study indicates that with the reduced use of antibiotics in food animals, it is possible to decrease the rate of resistant bacteria. Although the use of avoparcin had been banned in 1998, the VRE strains disappeared only five years later.     

Vancomycin for multi-drug resistant Enterococcus faecium cholangiohepatitis in a cat

A 12-year-old, neutered male domestic shorthair cat was evaluated with a life-long history of intermittent, predominantly small bowel diarrhea and a 3 day history of hematochezia. At presentation, the cat had increased liver enzyme activities and an inflammatory leukogram. Histopathology demonstrated inflammatory bowel disease (IBD), cholangiohepatitis and pancreatitis. The cholangiohepatitis was associated with a multi-drug resistant Enterococcus faecium. Gallbladder agenesis was also documented. Treatment with vancomycin was safely instituted for 10 days. Clinical signs resolved, however, cure of the bacterial cholangiohepatitis was not achieved. The risk of vancomycin resistant enterococci (VRE) in human and veterinary medicine is discussed.     

Survival rate of Suid herpesvirus (SuHV-1, Aujeszky's disease virus, ADV) in composted sewage sludge

Sewage sludge constitutes a source of valuable biogenic raw materials, but it is a carrier of many pathogenic microorganisms and viruses. Subjected to an effective sanitization by means of the process of composting, it is suitable to use in agriculture as fertilizers. The aim of this study was to observe the survival rate of Suid Herpesvirus under the influence of the temperature alone (water bath) as well as in sewage sludge subjected to the process of composting (pile). The samples were taken at different time intervals, and the virus titres were determined. The viruses survived considerably longer under laboratory conditions: at 30 degrees C as long as 21 days, at 40 degrees C - 93 hours, and at 50 degrees C - less than an hour. In the compost pile, in spite of the lack of the thermophylic phase, the total survival time of the viruses ranged from 34 to 44.5 hours, which indicates the vast importance of other physicochemical factors, apart from the temperature, contributing to virus inactivation.     

Evaluation of bovine spongiform encephalopathy (BSE) infection risk of cattle via sewage sludge from wastewater treatment facilities in slaughterhouses in Japan

Scattered SRM residues from BSE-infected cattle are possible to contaminate sewage during the slaughtering process in slaughterhouses. A proportion of the sludge discharged from wastewater treatment facilities at slaughterhouses has historically been processed into fertilizer. We therefore investigated the associated risk of BSE infection to cattle via sludge-derived fertilizer. Each stage of the process associated with BSE exposure was qualitatively evaluated and quantitative evaluations were subsequently performed using infectious dose as a unit of concern. Results of these qualitative evaluations indicated that installation of filter(s) at the drains to the wastewater treatment facilities has been undertaken by many slaughterhouses and has decreased the likelihood of SRM contamination of sewage. The level of sludge-derived fertilizer ingested by cattle was considered to be very low since the fertilizer is mixed with the ground soil, and the amount of soil ingested by cattle is likely to be small. Results from the quantitative analysis indicated the total infectious dose ingested by cattle in Japan from an infected cow has been estimated to be 5.5 x 10(-3) ID(50). Preventing scattering of SRM during the slaughtering process, installing filters to the drains with the removal of residues from the drain water and preventing the application of sludge-derived fertilizer to pasturelands would be effective to reduce the risk. Although the limited extent of available information, this study should provide useful indication for the development of an inclusive risk assessment for slaughterhouse sludge in the future.     

Parafilaria bovicola (Tubangui 1934) established in Swedish cattle

Parafilaria bovicola was recorded in Swedish cattle for the first time in 1978. The parasite causes carcass lesions with a maximum incidence from February to July but already in the previous November the carcass lesions appear regularly in the form of yellow oedema. In February and onward the oedema may be extensive with a greenish-yellow colour. The lesions are most prominent in bulls and more or less negligible in cows. However, the cows are considered to be important reservoirs for the parasite from one season to the next. Bleedings are seen from March until August and the infective larvae are transmitted to the cattle from early June by the intermediate host Musca autumnalis. Parafilaria lesions look remarkably like those caused by contusions during handling and transport previous to slaughter. Eosinophile infiltrations can be regarded as a constant diagnostic feature of parafilariosis.     

Tooth resorption in the Swedish Eurasion lynx (Lynx lynx)

The etiology of tooth resorption in the domestic cat remains unknown. The high prevalence and progressive nature of the disease complicates defining healthy control groups. In order to evaluate the possible influence of various life style changes on the prevalence of tooth resorption, healthy control groups are a prerequisite. This paper presents a prevalence study for tooth resorption in a free-ranging wild felidae population. Skulls from 46 free-ranging Eurasian lynx (Lynx lynx) were examined. The age of the animals had previously been estimated based on cementum annuli in the maxillary right canine tooth. The dental examination included both dental probing and radiographic imaging. Complicated fractures of the canine teeth were found in 9/46 (19.5%) skulls. In one fractured canine, apical root resorption and periapical lucency was detected. The root resorption was attributed to inflammatory resorption as a consequence of the initial dental trauma and necrotic pulp. No signs of tooth resorption were found in the remaining teeth. Supernumerary roots were detected in 18/46 skulls (39.1 %). Supernumerary "peg" teeth caudal to the mandibular first molar tooth were detected in 6/46 (13.0%) skulls. Although further studies on dental ultra-structure are needed, the Swedish Eurasian lynx may, in the future, be useful as a healthy comparative model for studies on the etiopathogenesis of tooth resorption in the domestic cat.     

Very low helminth infection in sheep grazed on pastures fertilised by sewage sludge or cattle slurry

Helminth infection acquired by lambs grazing on pastures fertilised either by urban sewage sludge or cattle slurry were studied in temperate Central Western France. The aim was to assess the risk of larval cestodoses in lambs after sewage application and of digestive tract nematode infection following the slurry application. Twenty-six sheep were allocated on two paddocks of 0.7 ha, one fertilised with sludge and the other with cattle slurry. The delay between application and actual grazing was 6 weeks; grazing on these paddocks extended from mid July to beginning of November 2002. The herbage biomass was slightly increased in the sludge paddock but it did not result in an increase of lamb live weight, compared with the slurry paddock. The lambs did not acquire cysticercosis or any other larval cestodoses in the sewage sludge group and only very limited infections with Cooperia spp. and Nematodirus spp. were observed in the slurry group. It was concluded that in our conditions the helminth risk was extremely low and was not a cause of restriction of the use of these biowastes.     

Phenotypic and genotypic characterization of antimicrobial resistance in faecal enterococci from wild boars (Sus scrofa)

The objective was to study the prevalence of antimicrobial resistance and the mechanisms implicated in faecal enterococci of wild boars in Portugal. One hundred and thirty-four enterococci (67 E. faecium, 54 E. hirae, 2 E. faecalis, 2 E. durans and 9 Enterococcus spp.) were recovered from 67 wild boars (two isolates/sample), and were further analysed. High percentages of resistance were detected for erythromycin, tetracycline, and ciprofloxacin (48.5%, 44.8%, and 17.9%, respectively), and lower values were observed for high-level-kanamycin, -streptomycin, chloramphenicol, and ampicillin resistance (9%, 6.7%, 4.5%, and 3.7%, respectively). No isolates showed vancomycin or high-level-gentamicin resistance. The erm(B), tet(M), aph(3')-IIIa, and ant(6)-I genes were demonstrated in all erythromycin-, tetracycline-, kanamycin-, and streptomycin-resistant isolates, respectively. Specific genes of Tn916/Tn1545 and Tn5397 transposons were detected in 78% and 47% of our tet(M)-positive enterococci, respectively. The tet(S) and tet(K) genes were detected in one isolate of E. faecium and E. hirae, respectively. Three E. faecium isolates showed quinupristin-dalfopristin resistance and the vat(E) gene was found in all of them showing the erm(B)-vat(E) linkage. Four E. faecium isolates showed ampicillin-resistance and all of them presented seven amino acid substitutions in PBP5 protein (461Q-->K, 470H-->Q, 485M-->A, 496N-->K, 499A-->T, 525E-->D, and 629E-->V), in relation with the reference one; a serine insertion at 466' position was found in three of the isolates. Faecal enterococci from wild boars harbour a variety of antimicrobial resistance mechanisms and could be a reservoir of antimicrobial resistance genes and resistant bacteria that could eventually be transmitted to other animals or even to humans.     

Element and polychlorinated biphenyl deposition and effects in sheep fed cabbage grown on municipal sewage sludge.

Sheep were fed a diet containing 30 per cent (dry weight) cabbage which had been grown on municipal sewage sludge from Syracuse, NY for 77 days. Slight increases were found in the concnetration of nickel in kidney, copper in liver and cadmium in certain animal organs as compared to those in sheep fed a control ration containing cabbage grown on soil. Polychlorinated biphenyls were also found at higher levels in the sludge-grown cabbage and in the livers of the respectively fed sheep as compared to controls. An increase in liver weight, proliferation of hepatic smooth endoplasmic reticulum and various degenerative changes were noted in the livers of the sheep fed the sludge-grown cabbage ration as compared to the controls.     

Effects of bites by the European adder (Vipera berus) in seven Swedish horses

The effects on seven horses of bites by the European adder (Vipera berus) are described and compared with previously available information. The clinical signs varied from local swelling and mild systemic signs to severe systemic signs, including systemic inflammatory response, severe tissue necrosis, ventricular tachycardia and dysphagia. Two of the horses were treated with 'Zagreb' antiserum, and three that were not treated with antiserum were euthanased owing to complications related to the bites.     

Occurrence of multidrug resistant Salmonella in antimicrobial-free (ABF) swine production systems

This cross-sectional study was conducted to determine the prevalence and antimicrobial resistance of Salmonella species in swine reared in the intensive (indoor) and extensive (outdoor) ABF production systems at farm and slaughter in North Carolina, U.S.A. We sampled a total of 279 pigs at farm (extensive 107; intensive 172) and collected 274 carcass swabs (extensive 124; intensive 150) at slaughter. Salmonella species were tested for their susceptibility against 12 antimicrobial agents using the Kirby-Bauer disk diffusion method. Serogrouping was done using polyvalent and group specific antisera. A total of 400 salmonellae were isolated in this study with a significantly higher Salmonella prevalence from the intensive (30%) than the extensive farms (0.9%) (P<0.001). At slaughter, significantly higher Salmonella was isolated at the pre- and post-evisceration stages from extensively (29% pre-evisceration and 33.3% post-evisceration) than the intensively (2% pre-evisceration and 6% post-evisceration) reared swine (P<0.001). The isolates were clustered in six serogroups including B, C, E1, E4, G and R. Highest frequency of antimicrobial resistance was observed against tetracycline (78.5%) and streptomycin (31.5%). A total of 13 antimicrobial resistance patterns were observed including the pentaresistant strains with ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline resistance pattern observed only among isolates from the intensive farms (n=28) and all were serotype Salmonella typhimurium var. Copenhagen. In conclusion, this study shows that multidrug resistant Salmonella are prevalent in ABF production systems despite the absence of antimicrobial selection pressure. In addition, it also highlights the possible role played by slaughterhouse and other environmental factors in the contamination and dissemination of antimicrobial resistant Salmonella in ABF production systems.