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Survival of Staphylococcus aureus in oral administration liquid medicaments and influence of count medium on survival
C Vivar1, C de la Rosa, A Mosso
1Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense, Ciudad Universitaria, Madrid, Spain.
Abstract:
The survival of Staphylococcus aureus was studied in 30 oral administration liquid medicaments (15 syrups and 15 solutions) to determine the effectiveness of the preservatives, the influence of the culture medium used in the enumeration of the surviving microorganisms, and the loss of the enzyme coagulase, phosphatase, DNase (deoxyribonuclease), and thermonuclease. Samples were inoculated with 6.3-6.5 x 10(5) viable cells per milliliter and were stored at room temperature for 60 days. Aliquots were taken for analysis at 0, 15, 22, 30, and 60 days after samples were inoculated. The enumeration of S. aureus was made by most probable number method (MPN) with six liquid culture media: triptone soy (TS), TS with 10% NaCl (TSS), TS and TSS with 0.2% catalase, Mannitol salt, and Tellurite-mannitol-glycine. The survival of S. aureus was lower in solutions than in syrups, decreased with the storage time, and depended on the culture medium utilized in the enumeration. Nonselective media were more sensitive than selective ones; that is, a better percentage of recovery was achieved with TS and the catalase medium. The preservative was effective in 93.3% of the samples. Coagulase was the most stable enzyme and phosphatase, DNase, and thermonuclease disappeared during the storage period.
Insights
Preservatives in oral liquid medicines effectively inhibited Staphylococcus aureus in most cases. However, bacterial survival and enzyme activity varied based on formulation type, storage duration, and the culture media used for testing.
Area of Science:
- Microbiology
- Pharmaceutical Sciences
- Food Science
Background:
- Staphylococcus aureus is a common pathogen that can contaminate pharmaceutical products.
- Liquid oral medicaments require effective preservation to prevent microbial growth.
- Enzyme activity in bacteria can indicate viability and metabolic status.
Purpose of the Study:
- To evaluate the efficacy of preservatives against Staphylococcus aureus in oral liquid medicaments.
- To determine the impact of different culture media on enumerating surviving microorganisms.
- To assess the stability of bacterial enzymes (coagulase, phosphatase, DNase, thermonuclease) during storage.
Main Methods:
- Survival of Staphylococcus aureus was assessed in 15 syrups and 15 solutions over 60 days.
- Bacterial enumeration used the most probable number (MPN) method with six different liquid culture media.
- Enzyme activity (coagulase, phosphatase, DNase, thermonuclease) was monitored throughout the storage period.
Main Results:
- Preservatives were effective in 93.3% of the tested medicaments.
- Staphylococcus aureus survival was lower in solutions than syrups and decreased over time.
- Non-selective media (Triptone Soy and catalase medium) showed higher recovery rates than selective media.
- Coagulase was the most stable enzyme; phosphatase, DNase, and thermonuclease were lost during storage.
Conclusions:
- The effectiveness of preservatives against Staphylococcus aureus in oral liquid medicaments is generally high.
- Bacterial enumeration methods and formulation type significantly influence survival assessment.
- Enzyme stability varies, with coagulase being the most resilient marker.