Transmission through air as a possible route of exposure for MRSA.

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is highly prevalent in pigs and veal calves. The environment and air in pig and veal calf barns is often contaminated with LA-MRSA, and can act as a transmission source for humans. This study explores exposure-response relationships between sequence type 398 (ST398) MRSA air exposure level and nasal ST398 MRSA carriage in people working and/or living on farms. Samples and data were used from three longitudinal field studies in pig and veal calf farm populations. Samples consisted of nasal swabs from the human participants and electrostatic dust fall collectors capturing airborne settled dust in barns. In both multivariate and mutually adjusted analyses, a strong association was found between nasal ST398 MRSA carriage in people working in the barns for >20 h per week and MRSA air levels. In people working in the barns < 20 h per week there was a strong association between nasal carriage and number of working hours. Exposure to ST398 MRSA in barn air seems to be an important determinant for nasal carriage, especially in the highly exposed group of farmers, next to duration of contact with animals. Intervention measures should therefore probably also target reduction of ST398 MRSA air levels.

Effects of Reducing Antimicrobial Use and Applying a Cleaning and Disinfection Program in Veal Calf Farming: Experiences from an Intervention Study to Control Livestock-Associated MRSA.

With the ultimate aim of containing the emergence of resistant bacteria, a Dutch policy was set in place in 2010 promoting a reduction of antimicrobial use (AMU) in food-producing animals. In this context, a study evaluated strategies to curb livestock-associated methicillin resistant Staphylococcus aureus (LA-MRSA). Fifty-one veal calf farms were assigned to one of 3 study arms: RAB farms reducing antimicrobials by protocol; RAB-CD farms reducing antimicrobials by protocol and applying a cleaning and disinfection program; and Control farms without interventions. MRSA carriage was tested in week 0 and week 12 of 2 consecutive production cycles in farmers, family members and veal calves. Interventions were validated and a cyclic rise in MRSA-prevalence in animals was shown with a more moderate increase in RAB farms. Prevalence in humans declined parallel over time in the study arms but RAB farms were at the lowest MRSA levels from the beginning of the study. In RAB-CD farms, human and animal prevalence did not differ from Control farms and MRSA air loads were significantly higher than in the other study arms. Mimicking the national trend, an overall AMU decrease (daily dosages per animal per cycle (DDDA/C)) was observed over 4 pre-study and the 2 study cycles; this trend did not have a significant effect on a set of evaluated farm technical parameters. AMU was positively associated with MRSA across study arms (ORs per 10 DDDA/C increase = 1.26 for both humans (p = 0.07) and animals (p = 0.12 in first cycle)). These results suggest that AMU reduction might be a good strategy for curbing MRSA in veal calf farming, however the specific cleaning and disinfecting program in RAB-CD farms was not effective. The drop in MRSA prevalence in people during the study could be attributed to the observed long-term AMU decreasing trend.

Livestock-associated MRSA in household members of pig farmers: transmission and dynamics of carriage, a prospective cohort study.

This prospective cohort study describes carriage of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in household members from 49 farrowing pig farms in the Netherlands (2010-2011). Of 171 household members, 4% were persistent MRSA nasal carriers, and the MRSA prevalence on any given sampling moment was 10% (range 7-11%). Working in the stables (of which 98% was MRSA-positive, prevalence ratio (PR) = 2.11 per 10 hours), working with sows (PR=1.97), and living with an MRSA-positive pig farmer (PR=4.63) were significant determinants for MRSA carriage. Significant protective factors were carriage of methicillin-susceptible Staphylococcus aureus (MSSA) (PR=0.50), and wearing a facemask when working in the stables (37% decreased prevalence). All MRSA strains during the study period were known livestock-associated types. The bacteriophage φ3 was not found in household members. Transmission from pigs and the environment appeared to be important determinants; human-to-human transmission could not sufficiently be differentiated. Wearing a facemask when working in the stables and carriage of MSSA are potential interventional targets.

Low incidence of livestock-associated methicillin-resistant Staphylococcus aureus bacteraemia in The Netherlands in 2009.

Methicillin-resistant Staphylococcus aureus (MRSA) is a worldwide problem in both hospitals and communities all over the world. In 2003, a new MRSA clade emerged with a reservoir in pigs and veal calves: livestock-associated MRSA (LA-MRSA). We wanted to estimate the incidence of bacteraemias due to LA-MRSA using national surveillance data from 2009 in the Netherlands. We found a low incidence of LA-MRSA and MRSA bacteraemia episodes, compared to bacteraemias caused by all S. aureus (0.04, 0.18 and 19.3 episodes of bacteraemia per 100,000 inhabitants per year, respectively). LA-MRSA and MRSA were uncommon compared to numbers from other countries as well. MRSA in general and LA-MRSA in specific does not appear to be a public health problem in the Netherlands now. The low incidence of LA-MRSA bacteraemia episodes may best be explained by differences in the populations affected by LA-MRSA versus other MRSA. However, reduced virulence of the strain involved, and the effectiveness of the search and destroy policy might play a role as well.

Dynamic of livestock-associated methicillin-resistant Staphylococcus aureus CC398 in pig farm households: a pilot study.

The aim of this study was to determine the long-term carriage rates and transmission dynamics of methicillin-resistant Staphylococcus aureus (MRSA) in pig farmers and their household members. During a 6-month period in 2009-2010, 4 pig farms in Denmark, Belgium, and the Netherlands, respectively, were studied for the presence of MRSA. The proportion of persistent carriers was significantly higher among farmers than among household members (87% vs. 11%) and significantly higher in household members from Belgium compared to those from Denmark and the Netherlands (29% vs. 0% vs. 6%). Determinant analysis of MRSA carriage revealed that pig contact was the most important determinant for MRSA carriage among household members and that the increased MRSA carriage rate observed among household members from Belgium is linked to country-specific differences in pig exposure. These findings demonstrated that even in pig farms with very high carriage rates of MRSA both in livestock and farmers, the risk for household members to acquire MRSA is limited and still depends strongly on pig exposure. By restricting access to the stables and exposure to pigs, MRSA acquisition by household members could be greatly reduced.

Cross border comparison of MRSA bacteraemia between The Netherlands and North Rhine-Westphalia (Germany): a cross-sectional study.

BACKGROUND: We describe the impact of methicillin-resistant Staphylococcus aureus (MRSA) in two neighbouring regions in Europe with a comparable population size, North Rhine-Westphalia (NRW) in Germany and the Netherlands. METHODOLOGY/PRINCIPAL FINDINGS: We compared the occurrence of MRSA in blood cultures from surveillance systems. In the Netherlands in 2009, 14 of 1,510 (0.9%) Staphylococcus aureus bacteraemia episodes under surveillance were MRSA. Extrapolation using the number of clinical admissions results in a total of 29 MRSA bacteraemia episodes in the Netherlands or 1.8 episodes per 1,000,000 inhabitants. In 2010 in NRW, 1,029 MRSA bacteraemias were reported, resulting in 57.6 episodes of MRSA bacteraemia per 1,000,000 inhabitants: a 32-fold higher incidence than in the Netherlands. CONCLUSION/SIGNIFICANCE: Based on an estimated attributable mortality of 15%, the Dutch approach would save approximately 150 lives per year by the prevention of bacteraemia only.

Livestock-associated methicillin-resistant Staphylococcus aureus in humans, Europe.

To estimate the proportion of methicillin-resistant Staphylococcus aureus (MRSA) isolates from humans that were sequence type (ST) 398, we surveyed 24 laboratories in 17 countries in Europe in 2007. Livestock-associated MRSA ST398 accounted for only a small proportion of MRSA isolates from humans; most were from the Netherlands, Belgium, Denmark, and Austria.

Persistence of livestock-associated methicillin-resistant Staphylococcus aureus in field workers after short-term occupational exposure to pigs and veal calves.

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) carriage in pig and veal calf farmers in the Netherlands is estimated at 25 to 35%. However, no information is available about MRSA carriage in humans after short-term occupational exposure to pigs or veal calves. This study examines the prevalence and duration of MRSA acquisition after short-term intensive exposure to pigs or veal calves for persons not exposed to livestock on a daily basis. The study was performed with field workers who took samples from the animals or the animal houses in studies on MRSA prevalence in pig and veal farms. They were tested for MRSA by taking nasal samples before, directly after, and 24 h after they visited the farms. There were 199 sampling moments from visits to 118 MRSA-positive farms. Thirty-four of these visits (17%) resulted in the acquisition of MRSA. Thirty-one persons (94%) appeared negative again after 24 h. There were 62 visits to 34 MRSA-negative farms; none of the field workers acquired MRSA during these visits. Except for that from one person, all spa types found in the field workers were identical to those found in the animals or in the dust in animal houses and belonged to the livestock-associated clone. In conclusion, MRSA is frequently present after short-term occupational exposure, but in most cases the strain is lost again after 24 h.

Maternal dietary B vitamin intake, other than folate, and the association with orofacial cleft in the offspring.

BACKGROUND: Periconceptional folic acid supplementation is suggested to prevent orofacial clefts (OFCs). Other B vitamins however may be beneficial as well. AIM OF THE STUDY: To investigate the maternal periconceptional dietary intake of thiamine, riboflavin, niacin, pyridoxine and cobalamin in association with the occurrence of OFC. METHODS: Two hundred and six mothers of a child with nonsyndromic OFC and 203 control mothers filled out a general questionnaire and a food frequency questionnaire around 14 months postpartum as a proxy for periconceptional intake. After exclusion of known pregnant and lactating mothers, those who reported to have altered their diet compared to the periconceptional period, and mothers with incidental folic acid supplement use periconceptionally, data of 182 OFC mothers and 173 controls were analysed. After logarithmic transformation, geometric means (P5-P95) were calculated and compared between the groups. After subsequent adjustment for energy, quintiles of dietary B vitamin intake were created. RESULTS: The periconceptional intake of thiamine, niacin and pyridoxine was significantly lower in mothers of an OFC child. A trend towards risk reduction for OFC with increasing dietary intake was demonstrated for thiamine (p = 0.04) and pyridoxine (p = 0.03). Risk reductions were only demonstrated in women using folic acid supplements periconceptionally. Supplement users tended to consume a diet richer in B vitamins. CONCLUSIONS: Periconceptional intake of thiamine, niacin and pyridoxine seems to contribute to the prevention of OFC.