Diversity of the virulence and genomic backgrounds in clinical isolates of Staphylococcus aureus collected in a Spanish hospital 1992 to 2006

Abstract number: P1409

Argudin M.A., Mendoza M.C., Vazquez F., Martin M.C., Rodicio M.R.

Staphylococcus aureus is an important human pathogen. The major virulence factors involved in pathogenesis are controlled by the agr (accessory gene regulator) quorum-sensing system. In this work, we studied the relationship between virulence (V) and genetic backgrounds of 30 non-invasive and 31 invasive isolates recovered in the Monte Naranco Hospital (Asturias, Spain) over 1992 to 2006. All isolates were typed by SmaI macrorestriction-PFGE followed by UPGMA-cluster analysis, and the V-gene profile was determined by PCR with primers specific for toxins and agr genes. In meticillin resistant isolates, the type of SSCmec was also identified.

The 61 isolates displayed 42 PFGE profiles, falling into 8 clusters and 11 branches, at S=0.6. One major cluster (15 SmaI-profiles including 25 invasive isolates) and 7 minor clusters (6 with non-invasive, and one with invasive isolates) were revealed. i) All isolates were positive for the hemolysin hla and hld genes and the leukotoxin lukED gene. The prevalent profile was hla-hlb-hld-hlg-hlg-variant (92%) with lukPV (26%). ii) 92% of the isolates were also positive for exfoliative toxins genes (et). The prevalent was etb, which appeared either alone (41%) or in combination with eta (20%), etd (26%) or both (5%). iii) 29.5% was positive for tst, present only in invasive isolates and frequently associated to agr group III. iv) 98% was positive for classic enterotoxin genes (se), all of them carrying the enterotoxin gene cluster (egc), in addition to other se-genes. Statistically significant differences between invasive and non-invasive isolates were: sea (45% vs. 93%), seb (6.5% vs. 47%), sec (87% vs. 50%), see (0% vs. 13%), and seu (55% vs. 0%). Regarding the agr type, invasive isolates carried agr group III (35%), while 20% of non-invasive isolates were positive for both agr group I and II (and possibly carried an agr-hybrid). Among the meticillin-resistant isolates, 71.4% within the invasive group contained SSCmec IVc, while the non-invasive group carried SSCmec I, SSCmec III or recombinant derivatives.

In summary, S. aureus causing invasive and non-invasive diseases in a Spanish Hospital were distributed in different genomic types. Despite of important differences in the genetic background, isolates of both groups are in possession of a very high number of common virulence factors. However, genes encoding potent virulence factors (lukPV, eta and tst) were more frequently found in the invasive isolates.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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