Purpose: To investigate the susceptibility of bacterial contaminants recovered from cosmetics to preservatives and antibiotics.

Methods: Nine bacterial isolates recovered from various brands of commercially available cosmetics marketed in Jordan were tested for their susceptibility pattern against two paraben esters and two formaldehyde donors in addition to nine commonly used antibiotics. The biocidal effect for three preservatives was tested at 0.2 % concentration while the fourth was determined at a strength of 0.3 %. Antibiotic sensitivity test was carried out using standard disc diffusion method.

Results: Isolates of Pseudomonas aeruginosa exhibited high resistance pattern to most of the tested preservatives and antibiotics; only one isolate was sensitive to imidazolidinyl urea while others were resistant to the 4 preservatives tested. Each of these isolates exhibited resistance to at least 5 antibiotics. Other organisms, including Escherichia coli and Staphylococcus aureus, were resistant to the class of preservatives used in the various formulations from which they were recovered and demonstrated resistance to fewer antibiotics. Coagulase-negative staphylococci were the most sensitive to both categories of antimicrobials used. One isolate was sensitive to all preservatives whereas the same isolate was resistant to only co-trimoxazole. Ciprofloxacin and norfloxacin demonstrated the highest in vitro antimicrobial effect against the contaminants investigated.

Conclusion: The bacterial contaminants of cosmetics exhibited variable cross resistance between preservatives and antibiotics. This cross resistance was species- and even strain-specific.