Penicillin-susceptible Staphylococcus aureus bacteremia: Epidemiological and clinical relevance. Possible therapeutic implications

Abstract

Introduction: The increase in penicillin susceptibility among Staphylococcus aureus (SA-Pen^S) might have therapeutic relevance. We aimed to study the current situation in our environment.

Material and methods: Over a 2.5 years period, all SA isolates from bacteraemia in one hospital were analysed. For all isolates, antimicrobial susceptibility profile, beta-lactam resistance genes (blaZ, mecA) and Panton-Valentine leucocidine encoding-genes were studied. For SA-Pen^S-blaZ^negative isolates, spa-type, MLST and the presence of other resistance genes were studied.

Results: Among 84 patients with SA bacteraemia (35.7% MRSA and 64.3% MSSA), 77 were analysed; 22.2% of MSSA isolates were Pen^S and blaZ^negative (Pen-MIC≤0.03μg/ml) corresponding to 14.3% of the total SA. In MSSA-Pen^S-blaZ^negative isolates, eight spa-types and 7 clonal-complexes were detected.

Conclusion: A high prevalence of MRSA/SA and MSSA-Pen^S-blaZ^negative/MSSA was detected in blood cultures. Pen-MIC≤0,3μg/ml corresponded to MSSA-Pen^S-blaZ^negative. This situation raises therapeutic options which should be further evaluated in larger studies and clinical trials.

Keywords: Bacteremia; Bacteriemia; Penicilina; Penicillin; Staphylococcus aureus; blaZ.