Determinants for antimicrobial resistance genes in farm dust on 333 poultry and pig farms in nine European countries

Livestock feces with antimicrobial resistant bacteria reaches the farm floor, manure pit, farm land and wider environment by run off and aerosolization. Little research has been done on the role of dust in the spread of antimicrobial resistance (AMR) in farms. Concentrations and potential determinants of antimicrobial resistance genes (ARGs) in farm dust are at present not known. Therefore in this study absolute ARG levels, representing the levels people and animals might be exposed to, and relative abundances of ARGs, representing the levels in the bacterial population, were quantified in airborne farm dust using qPCR. Four ARGs were determined in 947 freshly settled farm dust samples, captured with electrostatic dustfall collectors (EDCs), from 174 poultry (broiler) and 159 pig farms across nine European countries. By using linear mixed modeling, associations with fecal ARG levels, antimicrobial use (AMU) and farm and animal related parameters were determined. Results show similar relative abundances in farm dust as in feces and a significant positive association (ranging between 0.21 and 0.82) between the two reservoirs. AMU in pigs was positively associated with ARG abundances in dust from the same stable. Higher biosecurity standards were associated with lower relative ARG abundances in poultry and higher relative ARG abundances in pigs. Lower absolute ARG levels in dust were driven by, among others, summer season and certain bedding materials for poultry, and lower animal density and summer season for pigs. This study indicates different pathways that contribute to shaping the dust resistome in livestock farms, related to dust generation, or affecting the bacterial microbiome. Farm dust is a large reservoir of ARGs from which transmission to bacteria in other reservoirs can possibly occur. The identified determinants of ARG abundances in farm dust can guide future research and potentially farm management policy.

Extended-spectrum β-lactamase- and pAmpC-producing Enterobacteriaceae among the general population in a livestock-dense area

OBJECTIVES

In the Netherlands there is an ongoing debate regarding environmental health risks of livestock farming for neighbouring residents. This explorative study aims to determine the prevalence of carriage of extended-spectrum β-lactamase and/or plasmid-mediated AmpC-producing Enterobacteriaceae (ESBL/pAmpC-E) in the general population living in a livestock-dense area, and to study associations between determinants, including exposure through contact with animals and the environment, and human carriage of ESBL/pAmpC-E.

METHODS

A cross-sectional study was performed among 2432 adults (aged 20-72 years) in 12 temporary research centres in the south of the Netherlands, consisting of a questionnaire and analysis of a faecal sample to assess carriage of ESBL/pAmpC-E. Risk factors were analysed using logistic regression.

RESULTS

The prevalence for carriage of ESBL/pAmpC-E was 4.5% (109/2432; 95% CI 3.7-5.4) ranging from 1.4% to 10.9% among the research centres. ESBL/pAmpC resistance genes were detected in Escherichia coli and Klebsiella pneumoniae isolates obtained from these 109 persons and the most common ESBL-resistance genes were bla_CTX-M-15, bla_CTX-M-14/17 and bla_CTX-M-1, originating from 76 participants. Travel in the previous 12 months to Africa, Asia or Latin America (OR 2.82; 95% CI 1.71-4.63), having kept cows for a hobby in the previous 5 years (OR 3.77; 95% CI 1.22-11.64), usage of proton-pump inhibitors (OR 1.84; 95% CI 1.05-3.23), and living within 1000 m of a mink farm (OR 2.26; 95% CI 1.28-3.98) were identified as risk factors. Exposure to poultry was not identified as a risk factor.

CONCLUSIONS

Overall, living in close proximity to livestock animals and farms does not seem to be a risk factor for carriage of ESBL/pAmpC-E.

Risk factors for persistence of livestock-associated MRSA and environmental exposure in veal calf farmers and their family members: an observational longitudinal study

OBJECTIVES

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) emergence is a major public health concern. This study was aimed at assessing risk factors for persistently carrying MRSA in veal calf farmers and their family members. We also evaluate the dynamics of MRSA environmental load during the veal-calf production cycle.

DESIGN

Observational, longitudinal, repeated cross-sectional study.

SETTING

52 veal calf farms in the Netherlands.

PARTICIPANTS

From the end of 2010 to the end of 2011, a total of 211 farmers, family members and employees were included in the study.

PRIMARY OUTCOME AND SECONDARY OUTCOME MEASURES

Nasal swabs were taken from participants on days 0, 4, 7 and week 12. A persistent MRSA carrier was defined as a person positive for MRSA on days 0, 4 and 7. Participants filled in an extensive questionnaire to identify potential risk factors and confounders. For estimation of MRSA prevalence in calves and environmental contamination, animal nasal swabs and Electrostatic Dust Collectors were taken on day 0 and week 12.

RESULTS

The presence of potential animal reservoirs (free-ranging farm cats and sheep) and the level of contact with veal calves was positively associated with persistent MRSA carriage. Interestingly, at the end of the study (week 12), there was a twofold rise in animal prevalence and a significantly higher MRSA environmental load in the stables was found on farms with MRSA carriers.

CONCLUSIONS

This study supports the hypothesis that environmental contamination with MRSA plays a role in the acquisition of MRSA in farmers and their household members and suggests that other animal species should also be targeted to implement effective control strategies.

Repeatability of bronchial hyperresponsiveness to adenosine-5'-monophosphate (AMP) by a short dosimeter protocol

BACKGROUND

To study bronchial responsiveness to adenosine 5'-monophosphate (AMP) in population surveys, repeatability of a rapid dosimetric method with quadrupling doses was evaluated.

METHODS

Volunteers with symptoms of airway respiratory allergy or asthma were invited for AMP challenges on two occasions. After each dose the fall in forced expiratory volume in one second (FEV(1)) compared with the post-saline value was determined. The cumulative doses of AMP needed to cause a fall in FEV(1) of 20% (PD(20)), 15% (PD(15)), and 10% (PD(10)) were calculated. Agreement was evaluated by means of kappa values. After excluding systematic differences in PD values on two occasions (t test), repeatability of a single estimation of the chosen PD values was calculated and expressed in doubling doses (DD).

RESULTS

In 28 of 76 subjects a PD(20) was estimated on the two visits, in 29 subjects a PD(15) was estimated, and in 32 a PD(10) was obtained. Kappa values for a positive threshold were 0.89 for a cut off level for a 20% fall in FEV(1), 0.78 for a 15% fall in FEV(1), and 0.76 for a fall in FEV(1) of 10%. The PD values did not differ between the two visits and 95% repeatability of a single estimation was +/-1.7 DD for PD(20), +/-2.2 DD for PD(15), and +/-2.4 DD for PD(10). The quadrupling dose method reduced time by 40% in non-hyperresponsive subjects and no adverse effects were observed.

CONCLUSION

The short dosimeter protocol with quadrupling doses for AMP challenges is a rapid, reproducible tool for estimating bronchial responsiveness in population surveys.

Health surveillance for occupational chronic obstructive pulmonary disease

Screening for lung disease in workers with a low prevalence of chronic obstructive pulmonary disease (COPD) is subject to debate. Examining all workers would lead to unacceptable costs. Surveillance of high-risk groups may be a useful alternative. Data from 314 workers exposed to dust were used to develop a prediction model. Data from a study comprising 96 rubber workers were used to validate the model's performance. COPD was defined as a ratio of forced expiratory volume in 1 second to forced vital capacity outside the 5th percentile. The accuracy of the model was evaluated by receiver operating characteristic curve analysis and by comparison of the observed versus predicted probabilities. Shortness of breath, wheeze, heavy smoking, and work-related lower respiratory symptoms were identified as independent determinants of having COPD. Workers with COPD can be distinguished from those without COPD on the basis of a medical/work-related questionnaire. Occupational physicians can develop a low-cost strategy for detecting workers at risk for COPD.

Increased levels of markers of microbial exposure in homes with indoor storage of organic household waste

As part of environmental management policies in Europe, separate collection of organic household waste and nonorganic household waste has become increasingly common. As waste is often stored indoors, this policy might increase microbial exposure in the home environment. In this study we evaluated the association between indoor storage of organic waste and levels of microbial agents in house dust. The levels of bacterial endotoxins, mold beta(1-->3)-glucans, and fungal extracellular polysaccharides (EPS) of Aspergillus and Penicillium species were determined in house dust extracts as markers of microbial exposure. House dust samples were collected in 99 homes in The Netherlands selected on the basis of whether separated organic waste was present in the house. In homes in which separated organic waste was stored indoors for 1 week or more the levels of endotoxin, EPS, and glucan were 3.2-, 7.6-, and 4. 6-fold higher, respectively (all P < 0.05), on both living room and kitchen floors than the levels in homes in which only nonorganic residual waste was stored indoors. Increased levels of endotoxin and EPS were observed, 2.6- and 2.1-fold (P < 0.1), respectively, when separated organic waste was stored indoors for 1 week or less, whereas storage of nonseparated waste indoors had no effect on microbial agent levels (P > 0.2). The presence of textile floor covering was another major determinant of microbial levels (P < 0.05). Our results indicate that increased microbial contaminant levels in homes are associated with indoor storage of separated organic waste. These increased levels might increase the risk of bioaerosol-related respiratory symptoms in susceptible people.

Occupationally related exposures and reduced semen quality: a case-control study

OBJECTIVE

To determine whether there is an association between abnormal semen parameters and occupational exposures to organic solvents, metals, and pesticides.

DESIGN

Case-control study using three case groups based on different cutoff values for semen parameters and one standard reference group.

SETTING

University Hospital Utrecht and University Hospital Rotterdam, the Netherlands.

PATIENT(S)

Male partners of couples having their first consultation at the two infertility clinics (n = 899).

INTERVENTION(S)

Men provided at least one semen sample. Occupational exposure was assessed with use of job-specific questionnaires, a job exposure matrix, and measurements of metals and metabolites of solvents in urine.

MAIN OUTCOME MEASURE(S)

Standard clinical semen analyses were used to define case groups and controls.

RESULT(S)

An association between aromatic solvents and reduced semen quality was demonstrated, irrespective of the exposure assessment method used. The associations were stronger if the case definition was based on stricter cutoff values for semen parameters. Risk estimates were higher if the analysis was restricted to primary infertile men. Exposure to other pollutants at the workplace was not associated with impaired semen quality.

CONCLUSION(S)

The findings indicated an association between aromatic solvent exposure and impaired semen parameters.

Second follow-up of a Dutch cohort occupationally exposed to phenoxy herbicides, chlorophenols, and contaminants

A retrospective cohort study of workers exposed to phenoxy herbicides, chlorophenols, and contaminants (2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other polychlorinated dioxins and furans) has been conducted in a chemical factory in the Netherlands. Male workers exposed to phenoxy herbicides or chlorophenols showed increased relative risks (adjusted for age, calendar period at end of follow-up, and time since first exposure/employment) for total mortality (relative risk (RR)=1.8, 95% confidence interval (CI) 1.2-2.5), cancer mortality (RR=4.1, 95% CI 1.8-9.0), respiratory cancer (RR=7.5, 95% CI 1.0-56.1), non-Hodgkin's lymphoma (RR=1.7, 95% CI 0.2-16.5), and ischemic heart diseases (RR=1.8, 95% CI 0.9-3.6) compared with an internal referent group of nonexposed workers. By using TCDD levels (predicted at the time of maximum exposure), based on extrapolated TCDD levels that were measured in a subset of the cohort, estimated relative risks for workers with medium and high TCDD levels were comparable with risks derived from the simple and earlier applied dichotomous exposure classification. In general, relative risks were highest in the highest category, indicating exposure-related increases in risk with TCDD level. In conclusion, results of this cohort study support the evidence of a high cancer risk in workers exposed to phenoxy herbicides, chlorophenols, and contaminants.

Second follow-up of a Dutch cohort occupationally exposed to phenoxy herbicides, chlorophenols, and contaminants

A retrospective cohort study of workers exposed to phenoxy herbicides, chlorophenols, and contaminants (2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other polychlorinated dioxins and furans) has been conducted in a chemical factory in the Netherlands. Male workers exposed to phenoxy herbicides or chlorophenols showed increased relative risks (adjusted for age, calendar period at end of follow-up, and time since first exposure/employment) for total mortality (relative risk (RR)=1.8, 95% confidence interval (CI) 1.2-2.5), cancer mortality (RR=4.1, 95% CI 1.8-9.0), respiratory cancer (RR=7.5, 95% CI 1.0-56.1), non-Hodgkin's lymphoma (RR=1.7, 95% CI 0.2-16.5), and ischemic heart diseases (RR=1.8, 95% CI 0.9-3.6) compared with an internal referent group of nonexposed workers. By using TCDD levels (predicted at the time of maximum exposure), based on extrapolated TCDD levels that were measured in a subset of the cohort, estimated relative risks for workers with medium and high TCDD levels were comparable with risks derived from the simple and earlier applied dichotomous exposure classification. In general, relative risks were highest in the highest category, indicating exposure-related increases in risk with TCDD level. In conclusion, results of this cohort study support the evidence of a high cancer risk in workers exposed to phenoxy herbicides, chlorophenols, and contaminants.

[Future increase of the incidence of mesothelioma due to occupational exposure to asbestos in the past]

OBJECTIVE

To estimate the future course of mesothelioma mortality as a result of occupational exposure to asbestos in the past.

DESIGN

Cohort age model.

SETTING

Department of Public Health, Erasmus University Rotterdam, the Netherlands.

METHODS

A cohort age model was developed, based upon age-specific rates of pleural mesothelioma mortality during 1969-1994. This model was linked to the future trend in mortality among Dutch men as projected by the Central Bureau for Statistics in order to predict the future course of mesothelioma mortality in the period 1995-2030.

RESULTS

In the next 35 years about 20,000 cases of pleural mesothelioma among men are expected. The projection results in a peak of annual male mesothelioma deaths of approximately 700 in about the year 2018. After 2020 the annual mortality will rapidly decline to about 450 cases in 2030. It is expected that this rapid decline will continue after 2030. In the 1943-1947 birth cohort pleural mesothelioma may account for 0.87% of all deaths. Exposure to asbestos at work largely explains this particular mortality pattern.

CONCLUSION

Exposure to asbestos at work has created an important public health problem among Dutch men.

Exposure-sensitization relationship for alpha-amylase allergens in the baking industry

Fungal alpha-amylase is an important occupational allergen in the bakery industry. Epidemiologic studies focusing on the relationship between alpha-amylase allergen exposure and work-related respiratory allergy, however, have not been reported yet. In this cross-sectional study, sensitization to occupational allergens and work-related symptoms were studied in 178 bakery workers and related to allergen exposure. Alpha-amylase allergen concentrations were measured in personal dust samples, using a sandwich enzyme immunoassay. All workers were categorized into groups on the basis of their job histories and the alpha-amylase exposure levels of their job titles. Of all workers 25% had one or more work-related symptoms. As much as 9% of the bakery workers showed a positive skin prick test reaction to fungal amylase, and in 8% amylase-specific IgE was demonstrated. Alpha-amylase exposure and atopy appeared to be the most important determinants of skin sensitization, with prevalence ratios for atopy of 20.8 (95% CI, 2.74 to 158) and for medium and high alpha-amylase exposure groups of 8.6 (95% CI, 1.01 to 74) and 15.9 (95% CI, 1.95 to 129), respectively. Furthermore, a positive association was found between positive skin prick tests to alpha-amylase and work-related respiratory symptoms. In conclusion, this study has shown that there is a strong and positive relationship between alpha-amylase allergen exposure levels in bakeries and specific sensitization in bakery workers.