Livestock-associated MRSA responsible for human colonisation and infection in a northern region of Italy

Abstract number: P898

Monaco M., Pedroni M., Sanchini A., Bonomini A., Milanesi B., Pantosti A.

Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) has become a pathogen of increasing importance in health-care settings (HA-MRSA) and in community (CA-MRSA). Livestock-Associated MRSA (LA-MRSA) belonging to ST398 lineage, common among pigs and other animals, emerged in Central and Northern Europe, becoming a new risk factor for MRSA among farm workers. Strains belonging to ST398 can be responsible for human infections, mainly in areas with high livestock-farming. The aim of this study was to investigate the occurrence of LA-MRSA human colonization and infections in a Northern region of Italy with high density of pig and cattle farming.

Methods: In the period March-April 2010, at Manerbio Hospital (Lombardia Region) in the North of Italy, 879 nasal swabs were sampled from patients submitted to a pre-admission screening. In the period March-August 2010, at the same Hospital, MRSA isolated from outpatients infections were collected. By PCR assays, the species S. aureus, methicillin-resistance and the presence of Panton-Valentine (PVL) toxin genes were confirmed. Molecular characterization included SCCmec typing, spa typing and, on selected strains, multi-locus sequence typing (MLST).

Results: Out of 879 nasal swabs examined, 9 (1%) yielded MRSA. No strains were positive for PVL toxin genes. Six isolates harboured SCCmec type IV and 3 strains SCCmec type V. Five strains were assigned to t899 (3 isolates), t108 (1 isolate) and t2922 (1 isolate), all belonging to ST398 and therefore categorized as LA-MRSA. Three strains were t008-ST8 and 1 strain was t688-ST5, likely of hospital origin. A total of 10 MRSA were detected from outpatient infections of which 9 were skin and soft tissue infections (SSTI). Of these, 4 strains were PVL positive CA-MRSA which harboured SCCmec type IV (3 strains), type V (1 strain) and belonged to different clones (t005-ST5, t008-ST8, t021-ST8 and t7445-ST772). Other 5 strains were PVL negative, SCCmec type IV, t008 (2 strains), t127 (2 strains) and t515 (1 strain). One MRSA from ear infection was PVL negative, SCCmec type IV, t899 and ST398, hence categorized as LA-MRSA.

Conclusion: In areas with high density of pig and cattle farming LA-MRSA is able to colonize the population and also to produce infections along with typical and more common CA-MRSA. Since animal contact is an established risk factor for LA-MRSA, close surveillance combined to appropriate control measures should be employed to avoid LA-MRSA spread.

Session Details

Date: 07/05/2011
Time: 00:00-00:00
Session name: Abstracts of 21st ECCMID / 27th ICC
Location: Milan, Italy, 7 - 10 May 2011
Presentation type:
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