Study of antibiotic resistance, production of ESBL and other virulence factors in enterobacterial strains isolated from nosocomial infections in cardiovascular devices inserted patients

Abstract number: 902_p1360

Lazar V.


Since 1980s, ESBL-producing microorganisms, mostly Enterobacteriaceae emerged in the whole world. The increasing use of broader-spectrum cephalosporins is one of the major factors responsible for the high rate of selection of ESBL-producing microorganisms in Romanian hospitals.


To establish the incidence of ESBL-producing enterobacterial strains isolated from cardiovascular devices (CDs) inserted patients in the intensive care unit of the Institute of Heart Disease ‘C.C. Iliescu’ and to correlate the ESBL production with other virulence factors and with the plasmidial profile of these strains.


Antibiotic susceptibility determined by the disc diffusion; double disc-diffusion for ESBL phenotype detection; in vitro study of adherence and invasion capacity to HeLa cells investigated by gentamycin-protection assay; adherence to an inert substrate evaluated by the slime test; other virulence factors: Kanagawa and sheep erythrocytes haemolysins, DNase, lipase, lecitinase, amylase, gelatinase, mucinase and caseinase, Congo red test were tested on specific media; plasmid DNA isolation by alkaline lysis method.


In our study enterobacterial strains are placed on the second place in the aetiology of infections in CDs inserted patients, after staphylococci. The incidence of the main antibiotic markers was: 65% for aminopenicillins, 60% for third generation cephalosporins, 20% for aminoglycosides and 25% for fluoroquinolones. The ESBL screening test was positive in 60% of these strains. The multi-resistance feature was not associated with the production of other enzymatic virulence factors, which proved to be very poor for the tested strains. In exchange, the adhesion to the inert and to the cellular substrate proved to be a general feature of ESBL-producing enterobacterial strains. The plasmid DNA analysis revealed the presence of variable number of plasmids (ranging from 2.5 kbp to 30 kbp) in 20% of strains.


All isolated enterobacterial strains proved to be multiple drug resistant and of great concern is the fact that the third generation cephalosporins resistance and ESBL-production were highly prevalent in these strains suggesting the emergence of nosocomial infections with b-lactamases producer strains. The genetic determinism was in the great majority of cases nonplasmidial. The resistance to b-lactams is probably accompanied by changes in the bacterial wall structure promoting the adhesins expression.


Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
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