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Typing and characterization of antimicrobial resistance in methicillin-resistant Staphylococcus aureus ST398 from pigs including detection of clindamycin resistance mediated by linA gene

Abstract number: P1033

Aspiroz C., Lozano C., Ruiz-Larrea F., Zarazaga M., Torres C.

Introduction and Objective: Methicillin resistant Staphylococcus aureus (MRSA) isolates of sequence type ST398 have been identified to colonize and cause infections in animals and humans, especially in people in contact with pigs. The aim of this study was to characterize the resistance phenotypes and genotypes of MRSA isolated from pigs of a farm where one swine worker infected (skin lesion) and colonized by MRSA ST398 was previously detected (Aspiroz et al. SEIMC, 2009).

Methods: Nasal swabs were collected from 12 pigs of the farm and selective culture for MRSA recovery was performed on ORSAB agar plates (OXOID) and one isolate per positive sample was characterized. MRSA identification was confirmed by PCR of nuc and mecA genes. Antimicrobial susceptibility was determined by VITEK-2 system (bioMérieux) and by disc-diffusion method. MLST, SCCmec, agr and spa-typing was performed by PCR and sequencing. The presence of ermA, ermB, ermC, mrsA, linA, tet(K), tet(L), tet(M), tet(O), ant(4'), aph(3'), aac(6')-aph(2') and dfrK genes as well as PVL (lukF/lukS) genes were tested by PCR, and in some cases also by sequencing.

Results: MRSA ST398 were obtained from 11 of the 12 nasal swabs (91.6%). All 11 MRSA isolates showed resistance to tetracycline and were negative for PVL, and ten of them showed resistance to cotrimoxazole. Seven isolates were typed as spa-t108, SCCmecV and presented an unusual macrolide/lincosamides resistance phenotype: resistance to clindamycin and susceptibility to erythromycin and harboured linA in addition to tet(L), and dfrK genes. The four remaining MRSA-ST398 isolates were typed as spa-t011 and SCCmecIVa, and presented different resistance phenotypes, harbouring the following genes (number of isolates): ermA (2), ermB (2), ermC (2), tet(L) (11), tet(M) (5), dfrK (10), ant(4') (4), aph(3') (4), and aac(6')-aph(2') (3).

Conclusions:

1A high rate of colonization by MRSA ST398 is detected in pigs, being t011 and t108 the spa-types detected.

2MRSA ST398 presents a wide diversity of antimicrobial resistance phenotypes harbouring a high variety of resistance genes.

3The unusual pattern of erythromycin susceptibility and clindamycin resistance detected in 7 of 11 MRSA ST398 was mediated by linA, being this gene the first time found in a ST398 isolate.

4Clindamycin resistance can compromise treatment of skin lesions caused by MRSA ST398 of animal origin.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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