Prevalence of Methicillin Resistant Staphylococureus in veterinarians: an international view.

Mireille WH Wulf1 , Marit Sørum2 , Arie van Nes3 , Robert Skov2, Willem JG Melchers1, Corné HW Klaassen4, Andreas Voss1,4

1 Dept. Medical Microbiology, Radboud University Nijmegen Medical Centre, 2 Staphylococcus Laboratory, Statens Serum Institut, Copenhagen, Denmark, 3 Dept. Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University,

4 Dept. Medical Microbiology and Infectious Diseases, Canisius Wilhelmina Hospital, Nijmegen

Contact with livestock is a risk factor for MRSA-carriage in Dutch veterinarians and pig farmers. The “pig-type” MRSA strains are all non-typable by standard PFGE typing with SmaI due to the presence of a novel DNA methylation enzyme. Spa-typing of these strains showed that they belonged to a number of closely related spa-types (t011, t034, t108, t567, t571), corresponding to multi-locus sequence type (MLST) ST398.

These strains were first observed in the Netherlands in 2003 and are increasing in frequency.To investigate if contact with pigs might be a risk factor for MRSA carriage in other countries than the Netherlands, people attending an international conference on pig health in Denmark (IPVS) were screened.

Nose-throat swabs were taken from a sample of 272 IPVS participants. All were asked to answer a questionnaire about their contact with animals and the personal protective measures they use when entering stables.

Cultures were incubated in semi-selective Tryptone Soy broth containing 2,5% NaCl, 3.0 mg/L cefoxitin and 10 mg/L aztreonam (SSI Diagnostika, Hillerød, Denmark) and after 24 hrs sub-cultured on 5% sheep blood agar plates and MRSA-ID agar plates (bioMerieux, La Balme Les Grottes, France).

MecA gen PCR, typing by pulsed-field gel electrophoresis with SmaI and spa-typing were performed.

Table 1: Main characteristics of particpants

transmission of MRSA from pigs to care-takers appears to be an international problem that may create a new reservoir for community acquired MRSA in humans in Europe and beyond

a new zoonotic source of MRSA can have a severe impact on the epidemiology of MRSA and consequently on the control, especially in the current low prevalence countries using “Search and Destroy” to control MRSA.

Table 2: MRSA carriers per country including typing results

ResultsResults

Fig. 1. Distribution of participants and MRSA carriers from Europe

ConclusionsConclusions

• The overall prevalence of MRSA carriage was 12.5%.

• A significantly increased risk of MRSA carriage (OR 16.3; CI 3.75 to 70.6) was found for frequent pig contact (daily ora minimum of 5 hours/week) compared to seldom contact (less than once/month)

• 31 of 34 strains (91%) were non-typable by PFGE and corresponded to MLST398

• 26 (76%) strains belonged to identical spa-types found in Dutch pigs and pig farmers (corresponding to MLST 398)

• Protective measures, especially use of a mask, had no influence on the rate of MRSA colonization. “Statistically”, not wearing a mask was protective with an OR of 0.38 (CI 0.12 to 0.99)

Country Nr /country

MRSA pos (%) Spa-types (n)

Belgium 6 1 (16) t011Canada 16 1 (6) t034

Denmark 29 1 (3) t022*France 6 1 (16) t111#

Germany 39 13 (33) t011(8) t034 (4) t108Italy 13 8 (61) t108, t899(5), t1730Spain 11 2 (18) t011

Thailand 9 1(11) t034

Non-carriers (n=238)

MRSA carriers (n=34)

Mean age 42 (range 22-69)

42 (range 28-75)

Male 70% 80%Veterinarian 85% 97%Frequency of pig contact

frequentsometimesseldom

47%35%18%

94%6%0

Use of protective equipment

gownglovesmask

63%27%31%

50%74%56%

Recent hospital stay 5 (2%) 1 (3%)MRSA in family member 5 (2%) 1 (3%)

Number of MRSA carriers vs. number of participants per European country projected on the back-ground of the proportion of invasive MRSA isolates.

In the Netherlands, veterinarians in contact with pigs and pig farmers were found to have a higher risk of methicillin resistant S. aureus (MRSA) carriage than the general population. Identical strains were found in pig farmers, pig veterinarians and pigs. The objective of this study was to investigate if contact with pigs is a risk factor for MRSA carriage in an international setting.

272 attendants of an international conference on pig health were screened for MRSA carriage by nasal and throat swabs. A questionnaire was included about the type of animal contacts and possible exposure to known MRSA risk factors and the protective measures taken while entering stables.

Thirty-four participants from nine countries carried MRSA (12,5%). Thirty-one of these strains were non-typable by PFGE using SmaI. All the non-typable strains belonged to closely related spa-types (t011,t034, t108, t571,t567,t899) which correspond to MLST 398. All of the above mentioned spa-types, with exception of t899, have also been found either in Dutch pigs, pig farmers and/or veterinarians. The use of masks, gowns and gloves did not protect the user from acquiring MRSA.

Transmission of MRSA from pigs to care-takers appears to be an international problem, creating a new reservoir for community acquired MRSA in humans in Europe, and beyond. The rise of a new zoonotic source of MRSA can have a severe impact on the epidemiology of community acquired MRSA and may have consequences for the control of MRSA, especially in the current low prevalence countries using search and destroy policies.

AbstractAbstract

IntroductionIntroduction

MethodsMethods*corresponds to MLST ST22, a common CA-MRSA in Denmark.

#corresponds to MLST ST5

EARSS annual report 2004