Colonial Morphology of Staphylococci on Memphis Agar: Phase Variation of Slime Production, Resistance to β-Lactam Antibiotics, and Virulence

• Published in: The Journal of infectious diseases 1990-06, Vol.161 (6), p.1153-1169
• Main Authors: Christensen, Gordon D., Baddour, Larry M., Madison, Bereneice M., Parisi, Joseph T., Abraham, Soman N., Hasty, David L., Lowrance, Jon H., Josephs, Joseph A., Andrew Simpson, W.
• Format: Article
• Language: English
• Subjects: Animals; Anti-Bacterial Agents - pharmacology; Bacteriophages; beta-Lactams; Culture Media; Disease Models, Animal; Drug Resistance, Microbial; Endocarditis, Bacterial - microbiology; Genetic variation; Infections; Insect colonies; Major Articles; Male; Mice; Microscopy, Electron; Mutation; Phagocytosis; Phenotype; Phenotypes; Phenotypic variation; Rats; Rats, Inbred Strains; Staphylococcal Infections - microbiology; Staphylococcus; Staphylococcus - drug effects; Staphylococcus - genetics; Staphylococcus - growth & development; Staphylococcus - pathogenicity; Staphylococcus epidermidis - drug effects; Staphylococcus epidermidis - genetics; Staphylococcus epidermidis - growth & development; Staphylococcus epidermidis - pathogenicity; Staphylococcus saprophyticus; Urinary bladder; Urinary Tract Infections - microbiology; Vegetation; Virulence
• ISSN: 0022-1899; 1537-6613
• DOI: 10.1093/infdis/161.6.1153

The growth of Staphylococcus epidermidis sensu stricto and Staphylococcus saprophyticus on Memphis agar yielded up to 6 morphotypes with each strain. With S. epidermidis, one morphotype produced slime (ρ) but became non-slime-producing (ε) at a high frequency. The slime-producing ρ variants were methicillin-resistant and more virulent than methicillin-susceptible ε variants in an endocarditis model. With S. saprophyticus, phase variation was of higher frequency. Nitrosoguanidine mutagenesis produced a stable blue ε form that wasmore virulent than the parent in a mouse model of urinary tract infection. Mutants with the blue ε phenotype differed from gold ε parents in a variety of phenotypic properties, including increased resistance to oxacillin. These staphylococcal species have a high frequency of phase variation: Phase variants differ in antibiotic resistance and virulence, which is only partially correlated with suggested virulence factors such as slime production.