|Year : 2012 | Volume
| Issue : 4 | Page : 485-486
Changing susceptibility patterns of nonfermenting Gram-negative bacilli
S Arora, V Gautam, P Ray
Department of Medical Microbiology, PGIMER, Chandigarh, India
|Date of Submission||16-Mar-2012|
|Date of Acceptance||29-Mar-2012|
|Date of Web Publication||24-Nov-2012|
Department of Medical Microbiology, PGIMER, Chandigarh
Source of Support: None, Conflict of Interest: None
|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 2019 Sep 16];30:485-6. Available from: http://www.ijmm.org/text.asp?2012/30/4/485/103785
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. Only a few studies from India provide the antimicrobial susceptibility data of NFGNBs. 
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 , and subjected to susceptibility testing using Kirby-Bauer disc diffusion method as per CLSI (2010) guidelines.  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. 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.
We observed increasing rate of NFGNB infections in our institute (from 10% in April 2007-March 2009  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.  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|| |
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