In vitro serial passage of Staphylococcus aureus: changes in physiology, virulence factor production, and agr nucleotide sequence. J Bacteriol 2002 Mar;184(5):1430-7
Date
02/15/2002Pubmed ID
11844774Pubmed Central ID
PMC134861DOI
10.1128/JB.184.5.1430-1437.2002Scopus ID
2-s2.0-0036175120 (requires institutional sign-in at Scopus site) 149 CitationsAbstract
Recently, we observed that Staphylococcus aureus strains newly isolated from patients had twofold-higher aconitase activity than a strain passaged extensively in vitro, leading us to hypothesize that aconitase specific activity decreases over time during in vitro passage. To test this hypothesis, a strain recovered from a patient with toxic shock syndrome was serially passaged for 6 weeks, and the aconitase activity was measured. Aconitase specific activity decreased 38% (P < 0.001) by the sixth week in culture. During serial passage, S. aureus existed as a heterogeneous population with two colony types that had pronounced (wild type) or negligible zones of beta-hemolytic activity. The cell density-sensing accessory gene regulatory (agr) system regulates beta-hemolytic activity. Surprisingly, the percentage of colonies with a wild-type beta-hemolytic phenotype correlated strongly with aconitase specific activity (rho = 0.96), suggesting a common cause of the decreased aconitase specific activity and the variation in percentage of beta-hemolytic colonies. The loss of the beta-hemolytic phenotype also coincided with the occurrence of mutations in the agrC coding region or the intergenic region between agrC and agrA in the derivative strains. Our results demonstrate that in vitro growth is sufficient to result in mutations within the agr operon. Additionally, our results demonstrate that S. aureus undergoes significant phenotypic and genotypic changes during serial passage and suggest that vigilance should be used when extrapolating data obtained from the study of high-passage strains.
Author List
Somerville GA, Beres SB, Fitzgerald JR, DeLeo FR, Cole RL, Hoff JS, Musser JMAuthor
Jessica Hoff PhD Assistant Professor in the Pathology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Aconitate HydrataseBacterial Proteins
Bacterial Toxins
Base Sequence
Culture Media
Gene Expression Regulation, Bacterial
Hemolysin Proteins
Hemolysis
Humans
Oligonucleotide Array Sequence Analysis
Operon
Serial Passage
Shock, Septic
Staphylococcal Infections
Staphylococcal Protein A
Staphylococcus aureus
Time Factors
Trans-Activators
Virulence
