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  Table of Contents  
Year : 2012  |  Volume : 30  |  Issue : 4  |  Page : 485-486

Changing susceptibility patterns of nonfermenting Gram-negative bacilli

Department of Medical Microbiology, PGIMER, Chandigarh, India

Date of Submission16-Mar-2012
Date of Acceptance29-Mar-2012
Date of Web Publication24-Nov-2012

Correspondence Address:
V Gautam
Department of Medical Microbiology, PGIMER, Chandigarh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0255-0857.103785

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How to cite this article:
Arora S, Gautam V, Ray P. Changing susceptibility patterns of nonfermenting Gram-negative bacilli. Indian J Med Microbiol 2012;30:485-6

How to cite this URL:
Arora S, Gautam V, Ray P. Changing susceptibility patterns of nonfermenting Gram-negative bacilli. Indian J Med Microbiol [serial online] 2012 [cited 2020 Oct 24];30:485-6. Available from:

Dear Editor,

Nonfermenting Gram-negative bacilli (NFGNBs) are primarily opportunistic pathogens and pose a significant challenge because of their multiple, intrinsic or acquired drug resistance. Burkholderia cepacia complex (BCC) and Stenotrophomonas maltophilia are lysine decarboxylase-positive NFGNBs, characterized by their inherently contrasting susceptibility pattern to that of Pseudomonas aeruginosa.[1] Only a few studies from India provide the antimicrobial susceptibility data of NFGNBs. [2]

We present the susceptibility profile of NFGNBs isolated from blood specimens using automated blood culture system (BACTEC 9240) during January 2010-September 2011. The isolates were identified by conventional phenotypic methods [1],[3] and subjected to susceptibility testing using Kirby-Bauer disc diffusion method as per CLSI (2010) guidelines. [4] Various antibiotics used were co-trimoxazole (1.25 μg/23.75 μg), tetracycline (30 μg) and levofloxacin (5 μg) for S. maltophilia and in addition, meropenem (10 μg) and ceftazidime (30 μg) for BCC (levofloxacin was not used in BCC). For P. aeruginosa and Acinetobacter spp., ceftazidime (30 μg), cefotaxime (30 μg), gentamicin (10 μg), amikacin (30 μg), ciprofloxacin (5 μg) and cefoperazone-sulbactam combination (75 μg/10 μg) (Hi Media, Mumbai) were used.  Escherichia More Details coli ATCC 25922 and P. aeruginosa ATCC 27853 were used as the control strains.

Out of the total positive (n=9662) blood cultures, 18% (1781/9662) grew NFGNBs. Acinetobacter spp. (62%) was the most common followed by P. aeruginosa (18%), BCC (5%) and S. maltophilia (3%). 12% (221/1781) of the NFGNBs could not be identified. The percentage susceptibility of NFGNBs against various antimicrobial agents is shown in [Table 1]. In BCC isolates, meropenem and ceftazidime showed the highest sensitivity (83% each) followed by co-trimoxazole (80%) while tetracycline was the least effective (18%). S. maltophilia showed highest susceptibility to levofloxacin (84%) followed by co-trimoxazole (70%) and tetracycline (41%). Similar pattern was shown by Goel et al.[5] in case of Acinetobacter spp. However, in case of P. aeruginosa, susceptibility percentage was comparable against third generation cephalosporins only, higher against aminoglycosides and flouroquinolones in our isolates and comparatively lower against β-lactam/inhibitor combinations. Resistance rates of 3-82% to aminoglycosides, 19-74% to fluoroquinolones, 8-34% to b-lactam/inhibitor combinations and 17-74% to carbapenems among nonfermenters have been reported worldwide, indicating wide variation worldwide.
Table:1 Susceptibility pattern of various NFGNBs

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We observed increasing rate of NFGNB infections in our institute (from 10% in April 2007-March 2009 [2] to 18% in January 2010-September 2011). Acinetobacter spp. has remained the most common NFGNB during these years and did not show any significant difference in antimicrobial susceptibility when compared to 2007-2009. [2] In case of P. aeruginosa, ciprofloxacin sensitivity increased from 46% to 58% while that of cefotaxime and cefoperazone-sulbactam decreased from 41% and 73% to 27% and 37%, respectively. In BCC, meropenem sensitivity increased markedly from 60 to 83% and that of tetracycline decreased from 45 to 18%. In S. maltophilia, increasing resistance was observed against cotrimoxazole (9-30%) which is a matter of concern. However, tetracycline showed improved susceptibility from 34 to 41%. Based on the emerging abuse of antibiotics and bacterial resistance, therapy should only be advocated, as far as possible, after culture and sensitivity has been performed. It becomes important for the clinicians to remain updated with the current susceptibility profile of the various pathogens so that empirical therapy can be started accordingly.

 ~ References Top

1.Gautam V, Ray P, Vandamme P, Chatterjee SS, Das A, Sharma K, et al. Identification of lysine positive non-fermenting gram negative bacilli (Stenotrophomonas maltophilia and Burkholderia cepacia complex). Indian J Med Microbiol 2009;27:128-33.  Back to cited text no. 1
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2.Samanta P, Gautam V, Thapar R, Ray P. Emerging resistance of non-fermenting gram negative bacilli in a tertiary care centre. Indian J Pathol Microbiol 2011;54:666-7.  Back to cited text no. 2
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3.Collee JG, Miles RS, Watt B. Tests for the identification of bacteria. In: Collee JG, Fraser AG, Marmion BP, Simmons A, editors. Mackie and McCartney Practical Medical Microbiology. 14 th ed., vol. 2. London: Churchill Livingstone; 1996. p. 131-49.  Back to cited text no. 3
4.Clinical and Laboratory Standards Institute: Performance standards for antimicrobial susceptibility testing; twenteeth informational supplement M100-S20. Wayne: Clinical and Laboratory Standards Institute; 2010.  Back to cited text no. 4
5.Goel N, Wattal C, Oberoi JK, Raveendran R, Datta S, Prasad KJ. Trend analysis of antimicrobial consumption and development of resistance in non-fermenters in a tertiary care hospital in Delhi, India. J Antimicrob Chemother 2011;66:1625-30.  Back to cited text no. 5


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