Effect of pH on the morphology of Staphylococcus aureus
Mirza, J.; Kim, Y.; Lorian, V.
Drugs under Experimental and Clinical Research 11(3): 149-153
1985
ISSN/ISBN: 0378-6501 PMID: 3915285 Document Number: 257966
Nineteen strains of Staphylococcus aureus (10 sensitive and 9 resistant to oxacillin) were grown for four hours on membranes placed on trypticase soy agar at pH 5, 5.5, 6, 6.5, 7.1, 7.5, 7.8 and 8.3. The morphology was observed by interference phase contrast and by electron microscopy. All strains grown at pH 6 to 7.5 produced cocci of normal size. When grown at pH 5, 5.5, 7.8 and 8.3, however, seven of the oxacillin-resistant strains and seven of the oxacillin-sensitive strains produced bacterial cells 1.5 to 2 micron in diameter. These cells consist of a cluster of staphylococci held together by multiple thick cross walls. Their structure is similar to that of staphylococci grown in the presence of subminimum inhibitory concentrations of beta-lactam antibiotics, which inhibit autolysis of cross walls. It appears that autolysis of cross walls of S. aureus is also inhibited by a low or a high pH.