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Year : 2010  |  Volume : 53  |  Issue : 1  |  Page : 193-194
Epidemiology of extended spectrum β-lactamases in Serratia and Citrobacter species in North India

Department of Microbiology, Jawaharlal Nehru Medical College, A. M. U., Aligarh, India

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Date of Web Publication19-Jan-2010

How to cite this article:
Rizvi M, Fatima N, Shukla I, Malik A. Epidemiology of extended spectrum β-lactamases in Serratia and Citrobacter species in North India. Indian J Pathol Microbiol 2010;53:193-4

How to cite this URL:
Rizvi M, Fatima N, Shukla I, Malik A. Epidemiology of extended spectrum β-lactamases in Serratia and Citrobacter species in North India. Indian J Pathol Microbiol [serial online] 2010 [cited 2023 May 30];53:193-4. Available from:

In recent years, extended-spectrum beta-lactamases (ESBLs) have become more and more prevalent in species characterized by inducible class C cephalosporinase (AmpC) such as Citrobacter freundii and Serratia marcescens, which frequently segregate mutants with high-level constitutive production of AmpC enzymes. [1],[2] Although reported to be less common than AmpC hyperproduction, ESBLs among these species are emerging as a problem of grave concern. Although the resistance rates of Serratia sp and Citrobacter sp to third-generation cephalosporins are considerably high in India, studies on the resistance mechanisms to extended-spectrum cephalosporins among these species have been rarely performed here. [3],[4] Therefore, we aimed to study the resistance mechanism of extended-spectrum cephalosporins in clinical isolates and determine the prevalence rate of ESBLs in clinical isolates of Serratia and Citrobacter species which are rapidly emerging as significant multidrug resistant pathogens worldwide.

All consecutive isolates of Serratia spp and Citrobacter spp from various clinical specimens were studied for their drug resistance profiles for a period of six months from December 2007 to May 2008. Isolates were identified by standard biochemical techniques. [5] The isolates were tested against amikacin (30 µg), gentamicin (10 µg),ciprofloxacin (30 µg) gatifloxacin (5 µg), ofloxacin (5 µg),cefotaxime (30µg), ceftriaxone (30 µg), cefoperazone (Cs) 75 µg, cefoperazone sulbactam (Cfs) 75 µg, 1:1, cefixime (5 µg), netilmicin (30 µg), and tobramycin (10µg). All discs were obtained from Himedia, India. Cefoperazone sulbactam was used for confirmation of ESBL. ESBL producing Klebsiella pneumoniae ATCC 700603 and non ESBL producing  Escherichia More Details coli ATCC 25922 were used as positive and negative control.

Out of a total of 1923 single patient isolates of the family Enterobacteriaceae, 187 Serratia sp - 93 (49.7%) S. marcescens and remaining 94 (50.3%) other species and 212 Citrobacter sp - 54 (25.4 %) C. freundii, 91 (42.9 %), C. koseri and 67 (31.6 %) C. amalonaticus were isolated; 106 (56.6%) isolates of Serratia species were identified as ESBL producers, 67 (63.2%) were identified by all three inducers (cefoperazone- sulbactam, piperacillin- tazobactam, ceftazidime - clavulanic acid), 89 (83.9%) were identified as ESBLs by both cefoperazone sulbactam and piperacillin -tazobactam. Cefoperazone sulbactam alone identified 103 (97.1%) ESBLs and piperacillin - tazobactam identified 99 (93.3%) ESBLs. Ceftazidime - clavulanic acid identified 77 (72.6%) ESBLs alone. MIC 50 was 512 and the MIC range of cefoperazone sulbactam was >4096 - 4 mg/L respectively. The difference in MIC ratio of Cfs and Cs was eight-fold.

One hundred and thirty two (62.2%) of the Citrobacter sp were identified as ESBL producers. Cfs alone identified 126 (95.4%), piperacillin- tazobactam identified 119 (90.1%) in all and ceftazidime clavulanic acid alone identified 83 ESBL (62.8%) producers.MIC50 of cefoperazone sulbactam was > equal to 512 and the MIC range was 4096 -4 mg/L.

There is a greater need for informed antibiotic treatment guided by not only routine antimicrobial susceptibility but also by knowledge of the ESBL status of the isolate. Phenotypic detection of these resistance mechanisms though not confirmatory, are faster, far more cost effective, less labor intensive, not requiring a high level of technical expertise and thus easier to perform on a daily basis, not only in a resource poor country like India but also elsewhere; the outcome of which undoubtedly will be better patient care. Among the beta lactam/beta lactamase inhibitor combinations cefoperazone sulbactam was most sensitive against the ESBLs followed by piperacillin tazobactam. Another study reported better results of piperacillin-tazobactam (81.3%) than of cefoperazone sulbactam (76.06%) in Citrobacter sp. [6] It appears that different centers should individualize their drug policies.

   References Top

1.Livermore, D M, and D F J Brown. Detection of beta-lactamase mediated resistance. J Antimicrob Chemother 2001;84:S59-64.  Back to cited text no. 1      
2.Naumiuk L, Baraniak A, Gniadkowski M, Krawczyk B, Rybak B, Sadowy E, et al. Molecular epidemiology of Serratia marcescens in two hospitals in Danzig, Poland, over a 5-year period. J Clin Microbiol 2004;42:3108-16.  Back to cited text no. 2  [PUBMED]  [FULLTEXT]  
3.Shobha KL, Gowrish Rao S, Sigandhi Rao, Sreeja CK. Prevalence of extended spectrum Beta-lactamases in urinary isolates of Escherichia coli, Klebsiella and Citrobacter species and their antimicrobial suscepibility pattern in a tertiary care hospital. Indian Journal of the Practicing Doctor 2007;3:1-2.   Back to cited text no. 3      
4.Mohanty S, Singhal R , Sood S, Dhawan B, Kapil A, Das B. Citrobacter infections in a tertiary care hospital in Northern India. J Infect 2007;54:58-64.  Back to cited text no. 4      
5.P B Crichton. Enterobacteraceae. Escherichia, Klebsiella, Proteus and other genera. In: Collee JG, Fraser AG, Marmion BP, Simmons A, editor. Mackie and McCartney - Practical Medical Microbiology. 14 th ed. India. Churchill Livingstone 2006:361-84  Back to cited text no. 5      
6.Mohanty S, Singhal R, Sood S, Dhawan B, Das BK, Kapil A. Comparative in vitro activity of beta lactam/beta lactamase inhibitor combinations against gram negative bacteria. Indian J Med Res 2005;122:425-8.  Back to cited text no. 6  [PUBMED]  [FULLTEXT]  

Correspondence Address:
Meher Rizvi
Department of Microbiology, Jawaharlal Nehru Medical College, A. M. U., Aligarh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0377-4929.59237

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