E.A.M. Graat

Prevalence of livestock-associated MRSA in broiler flocks and risk factors for slaughterhouse personnel in The Netherlands.

To determine methicillin-resistant Staphylococcus aureus (MRSA) carriage in poultry and slaughterhouse personnel, 40 Dutch broiler flocks, in six slaughterhouses and 466 personnel were sampled. Of the employees, 26 were positive (5.6%), indicating a higher risk of exposure when compared to the general Dutch population (0.1%). This risk was significantly higher for personnel having contact with live animals (5.2%) - especially hanging broilers on the slaughterline (20.0%) - than for all other personnel (1.9%). Conventional electric stunning conferred a significantly higher risk of MRSA carriage for employees than CO2 stunning (9.7% vs. 2.0%). A total of 405 broilers were sampled upon their arrival at the slaughterhouse, of which 6.9% were positive. These broilers originated from 40 Dutch slaughter flocks of which 35.0% were positive. MRSA contamination in the different compartments of slaughterhouses increased during the production day, from 8% to 35%. Of the 119 MRSA isolates, predominantly livestock-associated MRSA ST398 was found, although 27.7% belonged to ST9 (spa type t1430). There is an increased risk of MRSA carriage in personnel working at broiler slaughterhouses, particularly those having contact with live animals.

Role of the Environment in the Transmission of Antimicrobial Resistance to Humans : A Review

To establish a possible role for the natural environment in the transmission of clinically relevant AMR bacteria to humans, a literature review was conducted to systematically collect and categorize evidence for human exposure to extended-spectrum β-lactamase-producing Enterobacteriaceae, methicillin-resistant Staphylococcus aureus, and vancomycin-resistant Enterococcus spp. in the environment. In total, 239 datasets adhered to inclusion criteria. AMR bacteria were detected at exposure-relevant sites (35/38), including recreational areas, drinking water, ambient air, and shellfish, and in fresh produce (8/16). More datasets were available for environmental compartments (139/157), including wildlife, water, soil, and air/dust. Quantitative data from exposure-relevant sites (6/35) and environmental compartments (11/139) were scarce. AMR bacteria were detected in the contamination sources (66/66) wastewater and manure, and molecular data supporting their transmission from wastewater to the environment (1/66) were found. The abundance of AMR bacteria at exposure-relevant sites suggests risk for human exposure. Of publications pertaining to both environmental and human isolates, however, only one compared isolates from samples that had a clear spatial and temporal relationship, and no direct evidence was found for transmission to humans through the environment. To what extent the environment, compared to the clinical and veterinary domains, contributes to human exposure needs to be quantified. AMR bacteria in the environment, including sites relevant for human exposure, originate from contamination sources. Intervention strategies targeted at these sources could therefore limit emission of AMR bacteria to the environment.

Prevalence and risk factor analysis of livestock associated MRSA-positive pig herds in The Netherlands

In 2005, methicillin-resistant Staphylococcus aureus was found in pig herds and in humans in contact with pigs. To determine the prevalence of, this now-called livestock-associated (LA) MRSA among pig herds in The Netherlands and to identify and quantify risk factors, an observational study of 202 pig herds was performed between 2007 and 2008. Five environmental wipes and 60 nasal swabs from each herd were collected, and microbiological analysis was performed on single environmental samples and pooled nasal samples. A herd was considered MRSA-positive if ≥1 sample tested positive. The prevalence of MRSA-positive herds was 67% in breeding herds and 71% in finishing herds. Multivariable logistic regression analysis was then performed on data from 171 breeding herds. The number of MRSA-positive herds increased from ∼30% at the start to ∼75% at the end of the study, most likely due to transmission between herds. The prevalence of MRSA increased with herd size, as ∼40% of smaller herds (<250 sows) were MRSA-positive compared to >80% of larger herds (>500 sows). Other risk factors (e.g. antimicrobial use, purchase of gilts and hygiene measures) were not significantly associated with MRSA, though associated with herd size. Herd size appeared to be a compilation of several factors, which made larger herds more often MRSA positive.

Extended-spectrum and AmpC β-lactamase-producing Escherichia coli in broilers and people living and/or working on broiler farms: prevalence, risk factors and molecular characteristics

OBJECTIVES The objectives of this study were to: estimate the prevalence of extended-spectrum β-lactamase (ESBL)- and AmpC β-lactamase-producing Escherichia coli carriage among broiler farmers, their family members and employees; identify and quantify risk factors for carriage, with an emphasis on contact with live broilers; and compare isolates from humans and broilers within farms with respect to molecular characteristics to gain insight into transmission routes. METHODS A cross-sectional prevalence study was conducted on 50 randomly selected Dutch broiler farms. Cloacal swabs were taken from 20 randomly chosen broilers. Faecal swabs were returned by 141 individuals living and/or working on 47 farms. ESBL/AmpC-producing E. coli were isolated and, for selected isolates, phylogenetic groups, plasmids and sequence types were determined. Questionnaires were used for risk factor analysis. RESULTS All sampled farms were positive, with 96.4% positive pooled broiler samples. The human prevalence was 19.1%, with 14.3% and 27.1% among individuals having a low and a high degree of contact with live broilers, respectively. Five pairs of human-broiler isolates had identical genes, plasmid families and E. coli sequence types, showing clonal transmission. Furthermore, similar ESBL/AmpC genes on the same plasmid families in different E. coli sequence types in humans and broilers hinted at horizontal gene transfer. CONCLUSIONS The prevalence among people on broiler farms was higher than in previous studies involving patients and the general population. Furthermore, an increased risk of carriage was shown among individuals having a high degree of contact with live broilers. The (relative) contribution of transmission routes that might play a role in the dissemination of ESBL/AmpC-encoding resistance genes to humans on broiler farms should be pursued in future studies.

MRSA CC398 in the pig production chain

In 2005, a distinct clone of methicillin resistant Staphylococcus aureus (MRSA CC398) was found in pigs and people in contact with pigs. The structure of the pig production chain in high technology pig husbandry enables pathogens to spread during animal trading, with an increasing prevalence in herds further down the chain. The objective of this study was to quantify the effect of the MRSA status of the supplying herd on the MRSA status of the receiving herd in order to gain more insight into the role of animal trading as a transmission route for MRSA CC398. Nasal samples (60-80 pigs per herd) were collected from 38 herds; in 20 herds, environmental samples were collected as well. Ten MRSA-positive herds (based on the results of nasal swabs of 10 individual pigs per herd) from a prior study were included in the data analysis. Herds were classified as MRSA positive if at least one sample tested positive. The 48 herds were part of 14 complete (40 herds) and 4 incomplete (8 herds) pig production chains. Fifty-six percent of the herds were classified as MRSA positive. MRSA-positive herds were observed at the start (breeding herds), middle (farrowing herds) and the end (finishing herds) of the pig production chain. All of the herds in 8 chains tested MRSA positive;, all of the herds in 5 chains tested MRSA negative and in the remaining 5 chains, MRSA-positive and MRSA-negative herds were detected. Seven spa types were found, which were all previously confirmed to belong to CC398. All of the isolates were susceptible to mupirocin, linezolid, rifampicin, fusidic acid and cotrimoxazole. Resistance against tetracycline, erythromycin and clindamycin was found in 100, 74 and 76% of the isolates, respectively. Seventy-nine percent of herds with a MRSA-positive supplier of pigs were MRSA positive, whereas 23% of herds with a MRSA-negative supplier were MRSA positive (OR=10.8; 95% CI: 1.5-110.1; P=0.011). The presence of entirely MRSA-positive and MRSA-negative chains and the strong association between the MRSA status of herds and their suppliers illustrates a large risk associated with purchasing pigs from MRSA-positive herds; a top-down strategy for future control programs is, therefore, a basic requirement. However, 23% of herds with a MRSA-negative supplier were MRSA positive and furthermore, 46% of the herds at the top of the pig production chain without a supplier tested MRSA positive. This underlined the need for the identification of additional risk factors for MRSA.

Seroprevalence and risk factors of Q fever in goats on commercial dairy goat farms in the Netherlands, 2009-2010

BackgroundThe aim of this study was to estimate the seroprevalence of Coxiella burnetii in dairy goat farms in the Netherlands and to identify risk factors for farm and goat seropositivity before mandatory vaccination started. We approached 334 eligible farms with more than 100 goats for serum sampling and a farm questionnaire. Per farm, median 21 goats were sampled. A farm was considered positive when at least one goat tested ELISA positive.ResultsIn total, 2,828 goat serum samples from 123 farms were available. Farm prevalence was 43.1% (95%CI: 34.3%-51.8%). Overall goat seroprevalence was 21.4% (95%CI: 19.9%-22.9%) and among the 53 positive farms 46.6% (95%CI: 43.8%-49.3%). Multivariable logistic regression analysis included 96 farms and showed that farm location within 8 kilometres proximity from a bulk milk PCR positive farm, location in a municipality with high cattle density (≥ 100 cattle per square kilometre), controlling nuisance animals through covering airspaces, presence of cats or dogs in the goat stable, straw imported from abroad or unknown origin and a herd size above 800 goats were independent risk factors associated with Q fever on farm level. At animal level almost identical risk factors were found, with use of windbreak curtain and artificial insemination as additional risk factors.ConclusionIn 2009-2010, the seroprevalence in dairy goats in the Netherlands increased on animal and farm level compared to a previous study in 2008. Risk factors suggest spread from relatively closely located bulk milk-infected small ruminant farms, next to introduction and spread from companion animals, imported straw and use of artificial insemination. In-depth studies investigating the role of artificial insemination and bedding material are needed, while simultaneously general biosecurity measures should be updated, such as avoiding companion animals and vermin entering the stables, next to advice on farm stable constructions on how to prevent introduction and minimize airborne transmission from affected dairy goat farms to prevent further spread to the near environment.

Prevalence of extended-spectrum β-lactamase-producing Enterobacteriaceae in humans living in municipalities with high and low broiler density

Prevalence of, and risk factors for, carriage of extended-spectrum β-lactamase (ESBL) -producing Enterobacteriaceae were determined for 1025 Dutch adults in municipalities with either high or low broiler densities. Overall prevalence of ESBL carriage was 5.1%. The hypothesis that individuals in areas with high broiler densities are at greater risk for ESBL carriage was rejected, as the risk was lower (OR = 0.45; p 0.009) for these individuals. Owning a horse increased the risk (OR = 4.69; p ≤0.0001), but horse owners often owned multiple species of companion animals. Routes of transmission from animals to humans in the community, and the role of poultry in this process, remain to be elucidated.

The effect of digital lesions and floor type on locomotion score in Dutch dairy cows

This study describes the effects of floor system, digital dermatitis (DD) and interdigital dermatitis and heel-horn erosion (IDHE) on locomotion performance in 225 dairy cows of 12 commercial dairy herds. Nine herds were kept in cubicle houses with concrete passageways (either solid, slatted, or grooved concrete) and three herds were kept in straw yards. Animals were at most five times examined at monthly intervals for lesion severity of DD and IDHE and for locomotion score. Locomotion score was rated on a scale ranging from 1 to 5 (from normal to severe) and disturbed locomotion (lameness) was defined as a score > or =3. A logistic regression model was used to analyze the 943 observations using lameness (yes/no) as outcome variable. The proportion of observations scored as lame (locomotion score > or =3) increased from 18% 1 month after trimming to 29% at 4 months after trimming. Severe lesions of DD and IDHE were associated with a significantly higher proportion of lame cows. The proportion of animals with disturbed locomotion increased from 16% to 40% as the severity of DD increased and from 17% to 30% with increasing severity of IDHE lesions. Locomotion performance highly differed between the cubicle house and straw yard group. Only 1% of all gaits in straw yard cows were scored as lame, while in cubicle housed cows these percentages varied from 24% to 46% with grooved floors showing the highest average locomotion score. Due to the extreme low incidence of lameness in straw yards, the statistical analysis had to be restricted to observations on concrete floors (n=744). The logistic regression model with lameness (yes/no) as dependent variable and random effects of cow and herd resulted in Odds Ratios for severe DD and IDHE of, respectively, 3.2 and 3.2, both significantly larger than unity. Cows housed at grooved concrete floors showed the highest OR of 6.5 compared to solid concrete floors. Recovery of lameness was poor as disturbance in gait lasted several months.

Modelling the effect of surveillance programmes on spread of bovine herpesvirus 1 between certified cattle herds.

For the eradication of an infectious agent, like bovine herpesvirus 1 (BHV-1), surveillance and certification can be used to reduce the transmission between herds. The goal of surveillance is that a certified herd that becomes infected is detected timely so that infection of several other certified herds is prevented. What counts is whether the reproduction ratio R, i.e. the average number of certified herds infected by one infected certified herd can be kept below 1. To support policy makers in making decisions about the minimal demands for a surveillance programme in an eradication campaign of BHV-1 in cattle, two mathematical models were investigated. With these models, the basic reproduction ratio between herds was calculated. The surveillance programmes were characterised with sample size, sampling frequency, test sensitivity, herd size, vaccination status, and contacts between herds. When R between herds is below 1, then the surveillance programme is sufficiently good to prevent spread of infection, provided that R is estimated well. In the model based on bulk milk testing sample size was replaced by a threshold at which bulk milk can be found positive. The R between herds was mainly influenced by the vaccination status, sampling frequency, and contacts between herds. Herd size moderately affected the outcome. Test sensitivity and sample size, however, were of minor importance. If herds of 50 cows became free of BHV-1 without vaccination, then spread of infection between herds might be prevented when animals within herds are sampled once a year (milk or blood samples). This frequency needs to be intensified, being twice a year, for larger herds and/or herds with extensive contacts with other herds. When bulk milk is sampled instead, sampling should be done at least every 5 months and more intensively, being each month, with larger herd sizes and more contacts between herds.

Prevalence of livestock-associated MRSA on Dutch broiler farms and in people living and/or working on these farms

This study aimed to determine the prevalence and risk factors for methicillin-resistant Staphylococcus aureus (MRSA) on 50 Dutch broiler farms. Of 145 persons living and/or working on these farms, eight tested positive for MRSA (5.5%). Investigation of 250 pooled throat samples of broilers and 755 dust samples resulted in four farms where MRSA-positive samples were present (8.0%). All isolates belonged to the CC398 complex. Living and/or working on a MRSA-positive farm was a risk for MRSA carriage; 66.7% of people on positive farms were MRSA positive vs. 1.5% on negative farms (P<0.0001). Due to the low number of positive farms and persons, and high similarity in farm management, it was impossible to draw statistically valid conclusions on other risk factors. For broiler farming, both farm and human MRSA prevalence seem much lower than for pig or veal farming. However, MRSA carriage in people living and/or working on broiler farms is higher compared to the general human population in The Netherlands (5.5% vs. <0.1%). As broiler husbandry systems are not unique to The Netherlands, this might imply that people in contact with live broilers are at risk for MRSA carriage worldwide.