Antibacterial Activity of ZnO Nanoparticles against ESBL and Amp-C Producing Gram Negative Isolates from Superficial Wound Infections

Antimicrobial drug resistance is a growing threat and a topic of intense research worldwide. Due to the extensive use of lactam antibiotics over the last several decades in clinical practice, various lactamases have emerged. The predominant mechanism for resistance to the -lactam antibiotics in Gram-negative bacteria is the Antibiotic resistance has become a serious problem that challenges the health of hospitalized patients. It is making a growing number of infections virtually untreatable. Therefore there is strong incentive to develop new bactericides. It is well known that inorganic nanomaterials are good antimicrobial agents. This study was done to look for antibacterial potentials of Zinc oxide nanoparticles to bacterial isolates of superficial skin infections. Total of 62 gram negative isolates from superficial wound infections were taken, which included 40 E. coli, 18 P. aeruginosa and 4 Klebsiella spp. Antibiotic susceptibility was done by Kirby Bauer disc diffusion method. MIC and MBC of ZnO nanoparticles against these isolates were calculated by agar dilution and broth dilution methods respectively and compared with that of standard strains. The bacterial growth curves were also plotted for 24 hours against these nanoparticles. Concentrations of ZnO nanoparticles used were 1000μg/ml, 2000μg/ml, 4000μg/ml, 8000μg/ml, 16000μg/ml and 32000μg/ml. Out of 62 isolates, 48 (77.7%) were multidrug resistant, 24 (38.7%) were AmpC producers while 26 (41.9%) were ESBL. The plotting of growth curves showed significant inhibition of growth at all concentrations. There was almost no rise in growth curve for 10hrs at concentrations of 1000μg/ml. MIC and MBC of standard strains were 1000μg/ml and 16000μg/ml respectively. Sixteen isolates showed MIC at 1000μg/ml while MBC at 4000μg/ml. Eighteen isolates showed MIC at 8000μg/ml while MBC at 16000μg/ml. ZnO nanoparticles can be used externally in the form of ointments, lotions and surface coating agents to prevent microorganisms from attaching, colonizing and spreading of bacterial infections. K e y w o r d s