Abstract
BackgroundCommunity-Associated Methicillin Resistant Staphylococcus aureus (CA-MRSA) has traditionally been related to skin and soft tissue infections in healthy young patients. However, it has now emerged as responsible for severe infections worldwide, for which vancomycin is one of the mainstays of treatment. Infective endocarditis (IE) due to CA-MRSA with heterogeneous vancomycin-intermediate susceptibility-(h-VISA) has been recently reported, associated to an epidemic USA 300 CA-MRSA clone.Case PresentationWe describe the occurrence of h-VISA phenotype in a case of IE caused by a strain belonging to an epidemic CA-MRSA clone, distinct from USA300, for the first time in Argentina. The isolate h-VISA (SaB2) was recovered from a patient with persistent bacteraemia after a 7-day therapy with vancomycin, which evolved to fatal case of IE complicated with brain abscesses. The initial isolate-(SaB1) was fully vancomycin susceptible (VSSA). Although MRSA SaB2 was vancomycin susceptible (≤2 μg/ml) by MIC (agar and broth dilution, E-test and VITEK 2), a slight increase of MIC values between SaB1 and SaB2 isolates was detected by the four MIC methods, particularly for teicoplanin. Moreover, Sab2 was classified as h-VISA by three different screening methods [MHA5T-screening agar, Macromethod-E-test-(MET) and by GRD E-test] and confirmed by population analysis profile-(PAP). In addition, a significant increase in cell-wall thickness was revealed for SaB2 by electron microscopy. Molecular typing showed that both strains, SaB1 and SaB2, belonged to ST5 lineage, carried SCCmecIV, lacked Panton-Valentine leukocidin-(PVL) genes and had indistinguishable PFGE patterns (subtype I2), thereby confirming their isogenic nature. In addition, they were clonally related to the epidemic CA-MRSA clone (pulsotype I) detected in our country.ConclusionsThis report demonstrates the ability of this epidemic CA-MRSA clone, disseminated in some regions of Argentina, to produce severe and rapidly fatal infections such as IE, in addition to its ability to acquire low-level vancomycin resistance; for these reasons, it constitutes a new challenge for the Healthcare System of this country.
Highlights
Community-Associated Methicillin Resistant Staphylococcus aureus (CA-MRSA) has traditionally been related to skin and soft tissue infections in healthy young patients
This report demonstrates the ability of this epidemic CA-MRSA clone, disseminated in some regions of Argentina, to produce severe and rapidly fatal infections such as Infective endocarditis (IE), in addition to its ability to acquire low-level vancomycin resistance; for these reasons, it constitutes a new challenge for the Healthcare System of this country
The worldwide increase of CA-MRSA infections is due to the dissemination of some epidemic CA-MRSA clones harboring pvl genes (PVL+), with a specific geographical pattern, these are frequently designated by their multilocus sequence type (MLST) or by their pulsed field gel electrophoresis (PFGE) pattern (ST1, ST8-USA300, ST30, ST59, ST93 and ST80) [1,2,3,4]
Summary
This report demonstrates the ability of this epidemic CA-MRSA clone, disseminated in some regions of Argentina, to cause severe and rapidly fatal infections such as infective endocarditis, in addition to its capacity to acquire low-level vancomycin resistance; for this reason, it has become a challenge for the healthcare system in our country. Additional file 1: Table S1: Antimicrobial susceptibility profile of urine-(SaU) isolate and blood isolates obtained before-(SaB1) and during-(SaB2) vancomycin therapy. Additional file 2: Figure S1: MRI (two slices) showing brain abscesses (white arrows) in a patient with CA-MRSA infective endocarditis. Additional file 3: Figure S2: Vancomycin population analysis profiles of initial isolate-(SaB1)-VSSA and after persistent bacteremia isolate-(SaB2)-h-VISA, despite vancomycin therapy SaB1: initial isolate, prior to vancomycin therapy. Additional file 4: Figure S3: PFGE-Analysis confirmed the clonality of the clinical isolates (SaU-SaB1-SaB2), belonging to CA-MRSA clone ST5-IV-PVL+. Sma I restriction patterns were indistinguishable for SaU (urine isolate), SaB1 (initial blood isolate) and SaB2 (later blood isolate), 1-5: five derivatives from SaB2 in PAPs (CIM ≥4 μg/ml), PFGE DNA pattern of representative of major clonal types belonging to ST5 lineage, both CA and HA-MRSA from Argentina, to be compared with subtype I2 CA-MRSA (ST5-IV-PVL): CA-MRSA I1 (ST5-IV-PVL+), HA-MRSA A1-Cordobes/Chilean clone (ST5-I) and HA-MRSA C1 Pediatric clone (ST100-IV). NC: NCTC 8325 control strain L: DNA molecular size markers in kb (lambda DNA ladder, Promega)
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