Molecular phylogenetic and biochemical characterization of Staphylococcus aureus isolates from non-sterile pharmaceutical cough formulations: An insight into genetic diversity.

BACKGROUND

Contamination of cough syrups not produced under sterile conditions is dangerous for users and can affect product quality.

METHODS

The bacterial quality was investigated in 15 cough syrup samples collected from Punjab, India (validity: January-June 2024). This was confirmed when contamination was measured via membrane filtration (0.45 μm pores) and microbes were grown on Tryptone Soya Agar, mannitol salt agar, Xylose Lysine Deoxycholate Agar and Eosin Methylene Blue Agar. The number of isolates (CFU/mL) was determined, and the isolates were identified using Gram staining, biochemical tests, and 16S-rRNA gene sequencing.

RESULTS

The presence of genetic variation among organisms was also evaluated. Only one out of 15 samples (6.66%) had levels higher than allowed, three others (20%) were near the limit, and the rest (73.33%) were below the United States Pharmacopeia (USP) limit ( 10³ CFU/mL) for bacterial contamination. Staphylococci sp. were present in syrups C, D, L, and O according to biochemical testing. The results for syrup C showed that Staphylococcus aureus (GenBank: PV137763) was above the level required by the USP. Genetic diversity analysis revealed six main haplotypes, with a high haplotype diversity (Hd= 0.8667) and nucleotide diversity (Pi = 0.09097), suggesting that the population is either expanding or undergoing purifying selection.

CONCLUSION

The majority of syrups were of good quality; however, there were contaminated samples, which raised doubts about how they were produced. It is recommended that good manufacturing practices be strictly enforced. Larger and ongoing quality control studies should be conducted to evaluate product safety.