Colonial morphology of staphylococci on Memphis agar: phase variation of slime production, resistance to beta-lactam antibiotics, and virulence.
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 (rho) but became non-slime-producing (epsilon) at a high frequency. The slime-producing rho variants were methicillin-resistant and more virulent than methicillin-susceptible epsilon variants in an endocarditis model. With S. saprophyticus, phase variation was of higher frequency. Nitrosoguanidine mutagenesis produced a stable blue epsilon form that was more virulent than the parent in a mouse model of urinary tract infection. Mutants with the blue epsilon phenotype differed from gold epsilon 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.
Christensen
G D
GD
Research Service, Harry S. Truman Memorial Veterans Hospital, Columbia, MO 65201.
Baddour
L M
LM
Madison
B M
BM
Parisi
J T
JT
Abraham
S N
SN
Hasty
D L
DL
Lowrance
J H
JH
Josephs
J A
JA
Simpson
W A
WA
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003470:Culture Media; D004195:Disease Models, Animal; D004352:Drug Resistance, Microbial; D004697:Endocarditis, Bacterial / Q000382:microbiology; D008297:Male; D051379:Mice; D008854:Microscopy, Electron; D009154:Mutation; D010587:Phagocytosis; D010641:Phenotype; D051381:Rats; D011919:Rats, Inbred Strains; D013203:Staphylococcal Infections / Q000382:microbiology*; D013210:Staphylococcus / Q000187:drug effects / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity; D013212:Staphylococcus epidermidis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity; D014552:Urinary Tract Infections / Q000382:microbiology; D014774:Virulence; D047090:beta-Lactams
D000900:Anti-Bacterial Agents; D003470:Culture Media; D047090:beta-Lactams