Comparative diffusion assay to assess efficacy of topical antimicrobial agents against Pseudomonas aeruginosa in burns care

Annals of Clinical Microbiology and Antimicrobials, Jun 2011

Background Severely burned patients may develop life-threatening nosocomial infections due to Pseudomonas aeruginosa, which can exhibit a high-level of resistance to antimicrobial drugs and has a propensity to cause nosocomial outbreaks. Antiseptic and topical antimicrobial compounds constitute major resources for burns care but in vitro testing of their activity is not performed in practice. Results In our burn unit, a P. aeruginosa clone multiresistant to antibiotics colonized or infected 26 patients over a 2-year period. This resident clone was characterized by PCR based on ERIC sequences. We investigated the susceptibility of the resident clone to silver sulphadiazine and to the main topical antimicrobial agents currently used in the burn unit. We proposed an optimized diffusion assay used for comparative analysis of P. aeruginosa strains. The resident clone displayed lower susceptibility to silver sulphadiazine and cerium silver sulphadiazine than strains unrelated to the resident clone in the unit or unrelated to the burn unit. Conclusions The diffusion assay developed herein detects differences in behaviour against antimicrobials between tested strains and a reference population. The method could be proposed for use in semi-routine practice of medical microbiology.

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Comparative diffusion assay to assess efficacy of topical antimicrobial agents against Pseudomonas aeruginosa in burns care

Annals of Clinical Microbiology and Antimicrobials Comparative diffusion assay to assess efficacy of topical antimicrobial agents against Pseudomonas aeruginosa in burns care Fabien Aujoulat 0 3 Franoise Lebreton 2 Sara Romano 0 1 3 Milena Delage 0 3 Hlne Marchandin 0 3 4 Monique Brabet 2 Franoise Bricard 1 Sylvain Godreuil 4 Sylvie Parer 1 Estelle Jumas-Bilak 0 1 3 0 Universite Montpellier 1, UMR5119, Unite de Bacteriologie, Faculte de Pharmacie , 15, Avenue Charles Flahault, BP 14491, 34093 Montpellier Cedex 5 , France 1 Centre Hospitalier Regional Universitaire de Montpellier, Hopital La Colombiere, Service d'Hygiene Hospitaliere , 39 avenue Charles Flahault, 34295 Montpellier Cedex 5 , France 2 Centre Hospitalier Regional Universitaire de Montpellier, Service des Brules, Hopital Lapeyronie , 371 Avenue du Doyen Gaston Giraud, 34295 Montpellier Cedex 5 , France 3 Universite Montpellier 1, UMR5119, Unite de Bacteriologie, Faculte de Pharmacie , 15, Avenue Charles Flahault, BP 14491, 34093 Montpellier Cedex 5 , France 4 Centre Hospitalier Regional Universitaire de Montpellier, Laboratoire de Bacteriologie, Hopital Arnaud de Villeneuve, , 371 Avenue du Doyen Gaston Giraud, 34295 Montpellier Cedex 5 , France Background: Severely burned patients may develop life-threatening nosocomial infections due to Pseudomonas aeruginosa, which can exhibit a high-level of resistance to antimicrobial drugs and has a propensity to cause nosocomial outbreaks. Antiseptic and topical antimicrobial compounds constitute major resources for burns care but in vitro testing of their activity is not performed in practice. Results: In our burn unit, a P. aeruginosa clone multiresistant to antibiotics colonized or infected 26 patients over a 2-year period. This resident clone was characterized by PCR based on ERIC sequences. We investigated the susceptibility of the resident clone to silver sulphadiazine and to the main topical antimicrobial agents currently used in the burn unit. We proposed an optimized diffusion assay used for comparative analysis of P. aeruginosa strains. The resident clone displayed lower susceptibility to silver sulphadiazine and cerium silver sulphadiazine than strains unrelated to the resident clone in the unit or unrelated to the burn unit. Conclusions: The diffusion assay developed herein detects differences in behaviour against antimicrobials between tested strains and a reference population. The method could be proposed for use in semi-routine practice of medical microbiology. Pseudomonas aeruginosa; burns; silver sulphadiazine; antiseptics; ERIC-PCR; diffusion assay - Background The current techniques of resuscitation, surgery and wound care have significantly improved the morbidity and the mortality of patients with burn wounds [1]. However, severely burned patients may still develop life-threatening nosocomial infections that remain a major challenge for burn teams [2]. The most frequent infections are wound infections, pneumonia, bloodstream and urinary tract infections [2,3]. Among the nosocomial pathogens, Pseudomonas aeruginosa from the patients endogenous microflora and/or from the environment represents the most common isolated bacteria in many centres [2,4,5]. Infections with P. aeruginosa are particularly problematic since this bacterium exhibits inherent tolerance to several antimicrobial agents and can acquire additional resistance mechanisms turning inefficient all current antimicrobial drugs [6,7]. Antiseptic and topical antimicrobial compounds represent major resources in the therapeutic arsenal available for burns care. It is widely recognized that these agents have played a significant role in decreasing the overall fatality rate in burn units. Some of them such as povidone-iodine and chlorhexidine are used for antisepsis during wound care, therapeutic bathes, debridement and surgery. Others, prepared as ointment or unguent, provide antimicrobial effects associated to the mechanic protection of the wound. For example, the use of cerium nitratesilver sulphadiazine that forms a leather-like eschar on burn wounds allows surgical treatment to be delayed and enables sequential excision and grafting [8-10]. This wound treatment policy is supposed to improve the patient survival [8,11] and is increasingly used. Resistance of P. aeruginosa to silver sulphadiazine has been previously documented [12]. In our unit, a P. aeruginosa clone multiresistant to antibiotics colonized or infected 26 patients over a 2-year period. Silver sulphadiazine susceptibility of this clone was questioned owing to long-time colonization or to refractory infections of the wounds. We comparatively investigated the susceptibility of the resident clone and unrelated P. aeruginosa strains to silver sulphadiazine and to the main topical antimicrobial agents currently used in the burn unit. For this purpose, we developed an optimized rapid method based on diffusion assay. This method appears suitable for semi-routine in (...truncated)


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Fabien Aujoulat, Françoise Lebreton, Sara Romano, Milena Delage, Hélène Marchandin, Monique Brabet, Françoise Bricard, Sylvain Godreuil, Sylvie Parer, Estelle Jumas-Bilak. Comparative diffusion assay to assess efficacy of topical antimicrobial agents against Pseudomonas aeruginosa in burns care, Annals of Clinical Microbiology and Antimicrobials, 2011, pp. 27, 10, DOI: 10.1186/1476-0711-10-27