ACTION OF NEWER DISINFECTANTS ON MULTIDRUG RESISTANT BACTERIA

Abstract

BACKGROUND: Current procedures for infection control in hospital environments have not been successful in curbing the rise in infections by multi-drug-resistant (MDR) pathogens. Emergence of resistance to chemical disinfectants is increasing steadily and has been reported worldwide. So prevention of multidrug-resistant health care associated infections (HAI) has become a priority issue and great challenge to clinicians. This requires appropriate sterilization and disinfection procedures and strict adherence to protocol in infection control policy. There is a need to evaluate the efficacy of newer disinfectants which have come into the market for better control of HAI. AIMS AND OBJECTIVES: The aim of this study was to evaluate and compare disinfection efficacy of three newer disinfectants– Novacide (didecyldimethylammonium chloride and polyhexamethylene biguanide), Silvicide a strong oxidizing agent (hydrogen peroxide and silver nitrate) and Virkon, a powerful oxidizing agent (a stabilized blend of peroxygen compounds and potassium salts), pitting them against two time-honored conventional disinfectants phenol and lysol and testing them against common MDR clinical isolates, reference strains and spores. MATERIALS AND METHODS: All the disinfectants at different dilutions were tested for bactericidal efficacy by liquid suspension time-kill tests. A heavy initial microbial load was simulated by preparing bacterial inoculum. Numbers of viable cells were counted and reduction in microbial colony counts before and after disinfectant exposure was expressed as log reduction. RESULTS: Among the disinfectants, Novacide was most effective. All clinical MDR bacterial isolates and reference strains were killed within 30 seconds of exposure at 0.156% solution, whereas spores got killed after 30 minutes of exposure at 2.5% solution which is the recommended concentration. For Silvicide all vegetative bacteria were killed at 5% solution after 20 minutes contact time and at 20% solution after 10 minutes contact time where recommended concentration is 20%. Spores also were killed at 20% solution after 1 hour contact time. Virkon was very effective for vegetative bacteria at 1% solution (which is the recommended concentration), killing within 30 seconds, but for exerting sporicidal action took 2 hours contact time. The conventional disinfectant phenol has currently restricted use because of its corrosive nature and high toxicity but still is considered as standard disinfectant for microbicidal efficacy testing methods. Lysol, the most widely used hospital disinfectant was found to be least effective among the five disinfectants. Both phenol and Lysol exerted poor sporicidal effect. CONCLUSION: Novacide is the most effective disinfectant in our study. Also Silvicide and Virkon being sporicidal agent can be considered as high level disinfectant, but Virkon required much greater time exposure inappropriate for routine hospital uses including instrument disinfection, floor cleaning and waste disposal.