Indian Journal of Medical Sciences Medknow Publications on behalf of Indian Journal of Medical Sciences Trust ISSN: 0019-5359 EISSN: 1998-3654 Vol. 59, Num. 5, 2005, pp. 214-216

Indian Journal of Medical Sciences, Vol. 59, No. 5, May, 2005, pp. 214-216

Letter To Editor

Gentamicin resistance in biofilm producing pseudomonas aeruginosa causing catheter associated urinary tract infections

Suman Ethel, Varghese Sini, Jose Jolly

Department of Microbiology, Kasturba Medical College, Mangalore - 575001

Correspondence Address: Department of Microbiology, Kasturba Medical College, Mangalore - 575001, sumane2001@yahoo.com

Code Number: ms05033

Sir,

Catheters introduce an artificial substratum into the body and cause persistent infections. These recurrent infections are mainly due to the accumulation of mixed biofilms on the artificial surface of the catheter or other implant.

A biofilm on an indwelling urinary catheter consists of adherent microorganisms, their extracellular products and host components deposited on the catheter. Biofilm on urinary catheters results in persistent infections that are resistant to antimicrobial therapy.[1] We hereby report the antibiotic sensitivity pattern of 26 strains of Pseudomonas aeruginosa and correlate the resistance pattern with the ability to form biofilms.

A total of 26 strains of Pseudomonas aeruginosa showing significant count (>105 cfu/ml) were isolated from cases of catheter-associated urinary tract infections. Identification was done by routine biochemical reactions.[2] Antibiotic sensitivity was performed by Kirby Bauer disk diffusion method using antibiotic disks from Hi Media, India.[3] Biofilm production was done by the microtitre plate method of O′Toole and Kolter and quantitated spectrophotometrically using an ELISA reader.[4] Pseudomonas aeruginosa ATCC 27853 was used as the control organism. The amount of biofilm produced was correlated to antibiotic resistance. Statistical analysis was performed by the Kruskal-Wallis test, Mann Whitney U test and Fisher′s exact test.

Out of total 26 strains of Pseudomonas aeruginosa isolated from catheter-associated urinary tract infections, 11 were sensitive to Amikacin (42.3%), 12 were sensitive to Carbenicillin (46.2%), 14 were sensitive to Ceftazidime (53.8%), 9 were sensitive to Ciprofloxacin (34.6), 4 were sensitive to Gentamicin (15.4%), 21 were sensitive to Imipenem (81%), 11 were sensitive to Norfloxacin (42.3%) and 8 were sensitive to Piperacillin (30.8%). Twenty out of 26 strains of Pseudomonas aeruginosa were biofilm producers (76.92%). Eighteen out of 26 strains (69.23%) were multiresistant strains i.e. resistant to ≥3 antibiotics. Of these, 15 produced significant amount of biofilm (83.3%). Twenty-two out of 26 strains were resistant to Gentamicin of which 19 were biofilm producers (86.36%). Five out of 26 strains were resistant to Imipenem. Three of them exhibited resistance to all other antipseudomonal drugs (60%). However, all five of them were biofilm producers. Hence the highest percentage of resistance was seen to Gentamicin. It was observed that strains which showed resistance to Gentamicin also showed significant increase in biofilm production ( P = 0.01). However there was no significant correlation between biofilm production and resistance to other antibiotics. [Table - 1] shows the correlation between biofilm production in Pseudomonas aeruginosa and sensitivity to antibiotics.

Colonization by Gentamicin-resistant Pseudomonas aeruginosa has been reported in earlier studies.[5] Our study showed increased biofilm production in strains resistant to Gentamicin. This could be one of the reasons for the increased prevalence of Gentamicin-resistant infections which are seen clinically. Studies to find an effective antibiotic which can act on biofilms, particularly in catheter-associated urinary tract infections, is warranted.

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Copyright 2005 - Indian Journal of Medical Sciences

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