Aetiological factors of vascular grafts infection and their antimicrobial susceptibility

Abstract number: 1134_02_281

Niedzwiadek J., Mazur E., Misztal S., Ziemba B., Terlecki P., Ligieza J., Koziol-Montewka M., Wronski J.

Objectives:

Vascular graft infection proved to be the most dangerous complication in vascular surgery patients. The aim of our study was the identification of microorganisms causing vascular graft infections and the evaluation of their antimicrobial susceptibility. 25 patients with infected vascular grafts, treated in Vascular Surgery Department, took part in our research. In 76% of patients, the late type of infection was recognized, in 24% of patients the infection was qualified as early.

Methods:

Purulent discharge obtained from the fistula was inoculated on the bacteriological media. Antimicrobial susceptibility was assessed by disc-diffusion method.

Results:

Staphylococcus aureus and Pseudomonas aeruginosa, present in 16,7% of patients, proved to be the most frequently isolated microorganisms. Staphylococcus epidermidis and E. coli were isolated in 13.3% and 10% of patients, respectively. Mixed infection, caused by two distinct bacteria, occurred in 20% of patients; in all cases one species belonged to Gram-positive, and the second one to Gram-negative bacteria. In 50% of patients with early type infection different species of Gram-negative rods were present, in 37.5% of patients, Staph. aureus and Staph. epidermidis were isolated, Enterococcus faecalis occurred in 12.5% of patients. In late type infection Gram-negative rods were isolated from 54.5% of patients and Gram-positive bacteria from 31.5% of patients. The most frequently isolated species appeared to be Pseudomonas aeruginosa. In one patient Candida crusei was isolated.

The isolated species of bacteria varied depending on the degree of infection (according to Shilagy and Samson). In IIIA degree of infection Staph. epidermidis and E. coli were present in 67.7% and 33.0% of patients, respectively. Pseudomonas aeruginosa and Staph. aureus were isolated in 21,1% of patients with IIIB degree of infection. Various species of Gram-negative rods were isolated from 80% of patients with IIIC degree of graft infection.

Conclusions:

Most isolated bacteria appeared to possess the resistance patterns typical for hospital flora; among them methicillin-resistant Staph. aureus (MRSA) and methicillin-resistant coagulase-negative Saphylococci (MRCNS) strains, Gram-negative rods producing extended spectrum of beta-lactamases (ESBL) or AmpC beta-lactamases, and Enterococcus faecalis with high level of aminoglicosides resistance (HLAR).