Detection and survival of Listeria monocytogenes in milk and dairy products.

Detection of L. monocytogenes in raw and pasteurized milk, Zabady, Karish, Domiati and Romi cheeses were done in this study using direct and cold enrichment methods. Out of 140 samples 3 samples were positive by cold enrichment and they were 2 of raw milk and one of Domiati cheese. Survival of L. monocytogenes was studied during heat treatment of milk by the sealed tube method of inactivation and it was found that L. monocytogenes inactivated completely at 60 degrees C for 15 minutes. There was a statistically inverse correlation between time of storage of dairy products and viable cell count of L. monocytogenes. PH played an important role in survival of that pathogen.

The importance of incubation temperature for detecting beta-lactam-resistant Staphylococcus aureus strains.

Sixty-six isolates of methicillin-resistant Staphylococcus aureus strains originating from Austria, Egypt, the Federal Republic of Germany and Switzerland were tested for their sensitivity to 12 beta-lactam antibiotics at both 30 degrees and 37 degrees C using the agar disk diffusion test. The MICs for six of the beta-lactam antibiotics were determined by the microdilution technique. Resistance to methicillin was always accompanied by resistance to several beta-lactam antibiotics. Resistance to all semi-synthetic penicillins and cephalosporins, including cefotaxime, was higher at 30 degrees C than at 37 degrees C. Cephalothin and cefamandole proved to be the most effective cephalosporin antibiotics against methicillin-resistant S. aureus strains. Newer cephalosporins, i.e. cefotaxime, cefoxitin and cefuroxime, exhibited only a low rate of activity against these strains. The occurrence of phage-type "85" in S. aureus strains from Austria, Egypt and Germany indicates that certain lysotypes are widespread.