Effect of Cold Shock on Growth and Antibiotics Susceptibility Patterns of Staphylococcus aureus, Klebsiella pneumoniae and Shigella dysenteriae

Abstract

This work was carried out to study the effect of cold shock on the growth of Staphylococcus aureus, Shigella dysentiea and Klebsiella pneumoniea moreover; evaluation of minimum inhibitory concentration of amoxicillin, cephalexin, ceftriaxone, ciprofloxacin, chloramphinicol and co-trimoxazole antibiotics with these organisms before and after cold shock. Serial dilutions were performed from an overnight nutrient broth for s.aureus, s.dyseteriae and k.pneumoniae. The diluted sample was placed on the center of a solid cooled nutrient agar medium and then spread. After incubation at 37 ̊c over night the colonies were counted each bacterium represent a colony forming unit (CFU). The colonies were counted according to Mils and Misra (1938) method, this method was done before and after cold shock. The results of counting for s.aureus, s.dysenteriae and k. pneumoniae is decreased after cold shock than before cold shock that indicate the cold shock is affect on bacterial growth. For MIC plates of Mueller Hinton agar were inoculated will bacterial suspension of shocked and non shocked bacteria different concentrations of MIC test strips HiComb from range A and B of (amoxicillin, ceftriaxon, cephlexine, ciprofloxacin, chloramphinicol and cotrimoxazole) were applicated after 24 h of incubation the MIC was determined from the highest dilution of the antibiotics showing no growth, the results for s.aureus with amoxicillin, ceftriaxon, cephlexine, chloramphinicol and cotrimoxazole before and after cold shock are not different but with ciprofloxacin was different before cold shock 7.5mcg and after 3mcg. Results of s.dysenteriae with amoxicillin, ceftriaxon, ciprofloxacin, chloramphinicol and cotrimoxazole were not different but with cephalexine before cold shock 30mcg and after cold shock 60mcg it’s become more resistant after cold shock. The MIC before and after cold were not different except in some cases.