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Acquisition and persistence of methicillin-resistant Staphylococcus aureus Clonal Complex 398 during occupational exposure
Abstract number: O93
van Cleef B., Haenen A., van den Broek M., Huijsdens X.W., Mulders M., Kluytmans J.
Objective: To determine the risk of acquiring Methicillin-resistant Staphylococcus aureus Clonal Complex 398 (MRSA-CC398) after short-duration occupational exposure to pigs, and to determine the persistence of MRSA-CC398 colonisation after acquisition. Methods: In a pilot study on the prevalence of MRSA-CC398 in pig farms [1] veterinary sample takers were tested before, directly after and 24 hours after visiting the farm. These sample takers all had short contact with pigs and dust on the farms, and were therefore at risk of acquiring MRSA if it was present on the particular farm. Data on farm characteristics (i.e. kind of farm, number of pigs, other animals present, and hygiene measures), veterinary samples and nasal samples of sample takers were collected. MRSA isolates were typed by staphylococcal protein A (spa) typing. Results: Complete data sets (samples taken before, directly after and 24 hours after a visit) were collected on 141 visits by 29 sample takers visiting 50 farms. On 28 farms MRSA was collected from pigs or stable-dust (56%). These farms were visited 78 times by 23 different sample takers. One sample taker (#12) was positive for MRSA before visiting a farm, he was removed from the following analysis. Fifteen of the 78 (19%) visits to MRSA-positive farms resulted in acquisition of MRSA and 11/23 (48%) sample takers acquired MRSA at least once after visiting a positive farm. Of these 11 positive sample takers 2 acquired MRSA twice and 1 sample taker acquired MRSA three times after separate visits. Of the 15 acquisitions of MRSA, 13 were negative after 24 hours. The spa-types of MRSA isolates found on the farms and sample takers were grossly comparable. On the 32 negative farms, none of the 60 visits resulted in MRSA acquisition. For further information see the table. Discussion: MRSA-CC398 was acquired by 48% of the sample takers after occupational exposure in this study. However, in 11 of the 13 cases the strain was not recovered the next day, therefore acquisition was of short duration, posing a limited treat to human health. Some persons seemed to be more vulnerable to acquire MRSA during their work. The sample size of this study was too small to draw final conclusions concerning this inter-personal variation. This requires a more extensive study. Table. Positive MRSA-tests of sample takers. Tests were taken before, directly after and 24 hours after visiting a farm. MRSA-status is indicated as + (positive) and - (negative), spa-types are shown between brackets. | Sample | farm MRSA-status | MRSA-test (spa-type) |
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| taker | (spa-type) | before visit | directly after visit | 24 hours after visit |
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| 1 | + (t011) | - | + (t011) | - | | 2 | + (t011) | - | + (t011) | - | | 3 | + (t011) | - | + (t011) | - | | | + (t108) | - | + (t108) | - | | 4 | + (t108) | - | + (t108) | - | | | + (t011) | - | + (t011) | - | | | + (t108) | - | + (t108) | - | | 5 | + (t011) | - | + (t108)b | - | | 6 | + (t011, t108, t1456) | - | - | + (t108)c | | 7 | + (t011, t108, t2330) | - | + (t108) | - | | | + (t567) | - | + (t567) | - | | 8 | + (t108) | - | + (t108) | - | | 9 | + (t011) | - | + (t011) | + (t011)d | | 10 | + (t011) | - | + (t011) | - | | 11 | + (t108) | - | + (t108) | - | | 12a | + (t899) | + (t011) | + (t011) | + (t011) | | | + (t011) | + (t011) | + (t011) | + (t011) | | | - | + (t108) | + (t108) | + (t108) | aSample taker 12 has daily contact with poultry and is excluded from analysis.
bSample taker 5 reported no contact with livestock elsewhere than in this study at that moment (spa-types of sample taker 5 and farm are not corresponding).
cSample taker 6 tested MRSA-negative in following tests.
dSample taker 9 was not tested again. |
References1. Van den Broek et al. Methicillin-resistant Staphylococcus aureus in people living and working in pig farms. Epidemiol. Infect., published online 24 October 2008 (doi:10.1017/S0950268808001507).
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