title: Clinical and molecular characteristics of infections with CO2-dependent small-colony variants of Staphylococcus aureus.
abstract: Most Staphylococcus aureus small-colony variants (SCVs) are auxotrophs for menadione, hemin, or thymidine but rarely for CO(2). We conducted a prospective investigation of all clinical cases of CO(2)-dependent S. aureus during a 3-year period. We found 14 CO(2)-dependent isolates of S. aureus from 14 patients that fulfilled all requirements to be considered SCVs, 9 of which were methicillin resistant. The clinical presentations included four cases of catheter-related bacteremia, one complicated by endocarditis; two deep infections (mediastinitis and spondylodiscitis); four wound infections; two respiratory infections; and two cases of nasal colonization. Pulsed-field gel electrophoresis typing showed that the 14 isolates were distributed into 4 types corresponding to sequence types ST125-agr group II (agrII), ST30-agrIII, ST34-agrIII, and ST45-agrI. An array hybridization technique performed on the 14 CO(2)-dependent isolates and 20 S. aureus isolates with normal phenotype and representing the same sequence types showed that all possessed the enterotoxin gene cluster egc, as well as the genes for alpha-hemolysin and delta-hemolysin; biofilm genes icaA, icaC, and icaD; several microbial surface components recognizing adhesive matrix molecules (MSCRAMM) genes (clfA, clfB, ebh, eno, fib, ebpS, sdrC, and vw); and the isaB gene. Our study confirms the importance of CO(2)-dependent SCVs of S. aureus as significant pathogens. Clinical microbiologists should be aware of this kind of auxotrophy because recovery and identification are challenging and not routine. Further studies are necessary to determine the incidence of CO(2) auxotrophs of S. aureus, the factors that select these strains in the host, and the genetic basis of this type of auxotrophy.
authors.affiliation: Servicio de Microbiología, Hospital Universitario 12 de Octubre, Avenida de Córdoba sn, Madrid 28041, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Gómez-González
authors.forename: Joshi
authors.initials: J
authors.lastname: Acosta
authors.forename: Jennifer
authors.initials: J
authors.lastname: Villa
authors.forename: Laura
authors.initials: L
authors.lastname: Barrado
authors.forename: Francisca
authors.initials: F
authors.lastname: Sanz
authors.forename: M Angeles
authors.initials: MA
authors.lastname: Orellana
authors.forename: Joaquín R
authors.initials: JR
authors.lastname: Otero
authors.forename: Fernando
authors.initials: F
authors.lastname: Chaves
mesh_terms: D000368:Aged; D016470:Bacteremia / Q000382:microbiology / Q000473:pathology; D015373:Bacterial Typing Techniques; D002245:Carbon Dioxide / Q000378:metabolism*; D002353:Carrier State / Q000382:microbiology; D055499:Catheter-Related Infections / Q000382:microbiology / Q000473:pathology; D016172:DNA Fingerprinting; D015299:Discitis / Q000382:microbiology / Q000473:pathology; D016521:Electrophoresis, Gel, Pulsed-Field; D004697:Endocarditis, Bacterial / Q000382:microbiology / Q000473:pathology; D005838:Genotype; D006801:Humans; D008297:Male; D008480:Mediastinitis / Q000382:microbiology / Q000473:pathology; D046228:Microarray Analysis; D008875:Middle Aged; D009666:Nose / Q000382:microbiology; D012141:Respiratory Tract Infections / Q000382:microbiology / Q000473:pathology; D013203:Staphylococcal Infections / Q000382:microbiology* / Q000473:pathology*; D013211:Staphylococcus aureus / Q000254:growth & development* / Q000302:isolation & purification* / Q000378:metabolism; D037521:Virulence Factors / Q000235:genetics; D014946:Wound Infection / Q000382:microbiology / Q000473:pathology
chemical_list: D037521:Virulence Factors; D002245:Carbon Dioxide