Related Experiment Video
Updated: Oct 29, 2025
Author Spotlight: Exploring the Antibacterial Effects of Zinc Oxide Nanoparticles in Overcoming Antibiotic Resistance
Published on: September 27, 2024
Penicillin susceptibility among invasive MSSA infections: a multicentre study in 16 Spanish hospitals
Olouwafemi Mistourath Mama1, Carmen Aspiroz2, Carmen Lozano1
1Área Bioquímica y Biología Molecular, Universidad de La Rioja, Madre de Dios 53, 26006, Logroño, Spain.
Objectives:
To determine the prevalence of penicillin susceptibility among MSSA causing bloodstream infections (BSIs) in 16 Spanish hospitals and to characterize the penicillin-susceptible MSSA (MSSA-PENS) isolates.
Methods:
A total of 1011 Staphylococcus aureus isolates were collected from blood cultures in 16 Spanish hospitals during 2018-19 (6-12 months) and their susceptibility to 18 antimicrobials was determined. The MSSA-PENS isolates were selected and examined by PCR to determine the presence of the blaZ gene, other resistance genes and the genes lukF/lukS-PV, eta, etb and tst. The immune evasion cluster (IEC) type was also analysed. All the MSSA-PENS isolates were submitted to S. aureus protein A (spa) typing and the clonal complexes (CCs) were assigned according to their spa type.
Results:
The prevalence of MSSA was 74.6% (754/1011) and 14.9% (151/1011) were MSSA-PENS-blaZnegative. MSSA-PENS-blaZnegative isolates (n = 151) were ascribed to 88 spa types and 11 CCs. The most frequent CCs were CC5 (35/151) and CC398 (25/151), with t002-CC5 and t571-CC398 being the most common lineages. Pan-susceptibility was identified in 117 of the 151 MSSA-PENS-blaZnegative isolates (77.5%). In the remaining isolates, erythromycin and clindamycin resistance was the most frequent resistance found, although tobramycin, ciprofloxacin, fusidic acid, mupirocin and/or tetracycline resistance was also detected. Thirty-eight MSSA-PENS-blaZnegative isolates were IEC negative and four isolates were Panton-Valentine leucocidin ('PVL') positive.
Conclusions:
A high penicillin susceptibility rate was detected among MSSA, opening therapeutic opportunities for BSIs. The emergence of new successful MSSA-PENS clones could be responsible for these data. The detection among MSSA-PENS-blaZnegative isolates of the clonal lineage CC398 or the absence of an IEC raises questions about their possible animal origin, requiring further analysis.
Insights
A high rate of penicillin susceptibility was found in Methicillin-Susceptible Staphylococcus aureus (MSSA) causing bloodstream infections (BSIs). This suggests new MSSA clones may be emerging, with some isolates potentially originating from animals.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Methicillin-Susceptible Staphylococcus aureus (MSSA) remains a significant cause of bloodstream infections (BSIs).
- Understanding the antimicrobial susceptibility patterns of MSSA is crucial for effective treatment strategies.
Purpose of the Study:
- To determine the prevalence of penicillin susceptibility among MSSA isolates causing BSIs in Spain.
- To characterize the genetic and clonal features of penicillin-susceptible MSSA (MSSA-PENS) isolates.
Main Methods:
- Collected 1011 Staphylococcus aureus isolates from blood cultures across 16 Spanish hospitals.
- Determined antimicrobial susceptibility, performed PCR for resistance and virulence genes (blaZ, lukF/lukS-PV, eta, etb, tst), analyzed immune evasion cluster (IEC) types, and conducted S. aureus protein A (spa) typing and clonal complex (CC) assignment.
Main Results:
- MSSA prevalence was 74.6%. Of these, 14.9% were penicillin-susceptible and blaZ-negative (MSSA-PENS-blaZnegative).
- MSSA-PENS-blaZnegative isolates belonged to 11 CCs, with CC5 and CC398 being most frequent. 77.5% were pan-susceptible.
- Other resistances included erythromycin, clindamycin, tobramycin, ciprofloxacin, fusidic acid, mupirocin, and tetracycline. Some isolates lacked IEC or were PVL-positive.
Conclusions:
- A high rate of penicillin susceptibility in MSSA causing BSIs offers therapeutic options.
- Emergence of successful MSSA-PENS clones is suggested.
- The presence of CC398 or absence of IEC in some isolates warrants further investigation into potential animal origins.
