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Journal of Clinical Microbiology, June 2001, p. 2151-2156, Vol. 39, No. 6
Research Laboratory on Biocompatibility of
Implant Materials, Rizzoli Orthopedic
Institute,1 and Experimental Pathology
Department, University of Bologna,2 Bologna, and
Laboratorio di Ultrastrutture, Istituto Superiore di
Sanità, Rome,3 Italy
Received 15 May 2000/Returned for modification 25 July
2000/Accepted 23 February 2001
Both Staphylococcus epidermidis and
Staphylococcus aureus are important causes of infections
associated with catheters and other medical devices. It has recently
been shown that not only S. epidermidis but also S. aureus can produce slime and carries the ica operon
responsible for slime production. In the operon, coexpression of
icaA and icaD is required for full slime
synthesis. In this study, the presence of icaA and
icaD was determined in a collection of 91 staphylococcal
(68 S. epidermidis and 23 S. aureus) strains
from intravenous catheter-associated infections, in 10 strains from the
skin and mucosa of healthy volunteers, and in two reference strains by
a PCR method. Slime-forming ability was tested on Congo red agar
plates; 49% of S. epidermidis strains from catheters and,
surprisingly, 61% of S. aureus strains were icaA and icaD positive and slime forming. All
the saprophytic strains turned out to be negative for both
icaA and icaD and also non-slime forming. Two
S. aureus and one S. epidermidis strain from
catheters, detected as icaA and icaD positive
by PCR analysis and as slime forming (black colonies) at 24 h on
Congo red agar, at 48 h exhibited tiny red spikes at the center of
black colonies. The onset of these variants could not be ascribed to a
mutagenic potential of Congo red, which, in the Ames test, was devoid
of mutagenicity. PCR analysis showed that these red variants were negative for both icaA and icaD and even
lacking the entire icaADBC operon. The data reported
indicate an important role of ica genes as a virulence
marker in staphylococcal infections from intravenous catheters.
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.6.2151-2156.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Presence of icaA and icaD
Genes and Slime Production in a Collection of Staphylococcal Strains
from Catheter-Associated Infections
*
Corresponding author. Mailing address: Laboratorio di
Biocompatibilità dei Materiali da Impianto, Istituti Ortopedici
Rizzoli, Via di Barbiano, 1/10, 40136 Bologna, Italy. Phone: 39 51 6366599. Fax: 39 51 6366599. E-mail for Carla Renata Arciola:
carlarenata.arciola{at}ior.it. E-mail for Lucio Montanaro:
luciomontanaro{at}alma.unibo.it.
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