The concomitant development of poly(vinyl chloride)-related biofilm and antimicrobial resistance in relation to ventilator-associated pneumonia

Ventilator-associated pneumonia is a major cause of death in intensive care patients and the endotracheal tube, commonly fabricated from poly(vinyl ch loride) (PVC), is acknowledged as a significant factor in this. Bacteria co lonise the biomaterial, thereby adopting a sessile mode of growth that prog resses to the establishment of an antibiotic-resistant biofilm by the accre tion of a protective glycocalyx. This study examined the sequential steps i nvolved in the formation of biofilm on PVC by atomic force microscopy and t he concomitant development of resistance to an antibiotic (ceftazidime) and to a non-antibiotic antimicrobial agent (hexetidine). Staphylococcus aureu s and Pseudomonas aeruginosa isolated from ET tube biofilm were employed. T he surface microrugosity of bacteria growing in sessile mode on PVC decreas ed significantly (p < 0.05) over the period 4, 24 48 h and 5 d. The progres sive accretion of bacterial glycocalyx was readily visualised in micrograph s leading to a smoother surface topography with time. The minimum inhibitor y concentrations (MIC) and minimum bactericidal concentrations (MBC) for ce ftazidime and hexetidine against planktonic (suspension) S. aureus were low er than for Ps. aeruginosa. Furthermore, sessile populations of S. aureus a nd Ps. aeruginosa on PVC exhibited greater resistance to both ceftazidime a nd hexetidine when compared to planktonic bacterial growth. The efficacy of the agents, determined by kill kinetics, against sessile bacteria was depe ndent on age, with established biofilms (greater than or equal to 24 h) sig nificantly more resistant (p < 0.05) than early sessile populations (less t han or equal to 4 h). Importantly, for practice, even newly colonised bacte ria (1 h) were significantly more resistant to antibiotic than planktonic b acteria. Hexetidine was significantly more active (p < 0.05) than ceftazidi me on biofilms of both isolates, irrespective of age, with total kill withi n 24 h treatment. Hexetidine may offer promise in the resolution of infecti on associated with PVC endotracheal tubes. (C) 2001 Elsevier Science Ltd. A ll rights reserved.