Prevalence of extended spectrum β-lactamase-producing clinical isolates of Klebsiella pneumoniae in intensive care unit patients of a tertiary care hospital


Aim: To identify the extended-spectrum β-lactamase producing Klebsiella pneumoniae (ESBL-KP) isolated from intensive care unit (ICU) patients of a tertiary care hospital. Materials and Methods: Seventy Klebsiella pneumoniae clinical isolates from ICU patients were screened for ESBL production. All were confirmed for ESBL production by potentiated disc diffusion test. Minimum inhibitory concentrationby agar dilution technique was performed. Sensitivity to other group of drugs was determined by Kirby-Bauer method against ciprofloxacin, amikacin, co-trimoxazole. Results: In all, 74% of the isolates were ESBL-KP; 57% were from blood samples. Coresistance to other group of drugs ranged from 63 to 83%. Conclusion: There is a high prevalence of ESBL-KP. The prompt reporting of ESBL producing bacteria is necessary to prevent their dissemination. This alarms for strict infection control measures to be practised in hospital settings.

Keywords: Extended-spectrum β-lactamases, Intensive Care Unit, Klebsiella pneumoniae

How to cite this article:
Harakuni S, Karadesai S G, Mutnal M B, Metgud S C. Prevalence of extended spectrum β-lactamase-producing clinical isolates of Klebsiella pneumoniae in intensive care unit patients of a tertiary care hospital. Ann Trop Med Public Health 2011;4:96-8
How to cite this URL:
Harakuni S, Karadesai S G, Mutnal M B, Metgud S C. Prevalence of extended spectrum β-lactamase-producing clinical isolates of Klebsiella pneumoniae in intensive care unit patients of a tertiary care hospital. Ann Trop Med Public Health [serial online] 2011 [cited 2020 Sep 23];4:96-8. Available from:

Cephalosporins have evolved to a great extent, with four generations of drugs. They have broad spectrum of activity, against both gram positive and gram negative bacteria. They are widely used in intensive care units (ICUs) The emergence of extended-spectrum β-lactamases (ESBL) producing gram negative bacilli is a threat to therapeutic administration of cephalosporins. There is plasmid-mediated coresistance to other group of antibiotics, also, in ESBL-producing bacteria. [1],[2]

Among the various bacteria, Klebsiella pneumoniae is most prevalent. Klebsiella pneumoniae is an opportunistic pathogen, which mainly causes infection in immunocompromised patients. Klebsiella pneumoniae is the commonest isolate from cases of neonatal sepsis accounting for great mortality rate. [3],[4] The prevalence of ESBL-producing bacteria is being increasingly reported from various parts of the world. [4],[5],[6],[7] Thus, this study was undertaken to evaluate the prevalence of ESBL-KP among patients reporting to the ICU of our tertiary care institute.

Materials and Methods

This study was conducted in the Department of Microbiology, of a tertiary care hospital. Seventy Klebsiella pneumoniae clinical isolates were screened from ICU patients admitted from January to December 2004. The isolates were from blood, sputum, pus, catheters, endotracheal tip, and exudates.

All the isolates were characterized to species level using standard procedures. [8] Antibiotic susceptibility testing against Clinical Laboratory Standards Institute recommended panel was performed by Kirby-Bauer disc diffusion method. Each strain was screened for ESBL production against cefotaxime (30 mg) and ceftazidime (30 mg) discs (Hi Media, Mumbai). All the isolates were confirmed for ESBL production by potentiated disc diffusion test and minimum inhibitory concentration (MIC) reduction on agar dilution method as recommended by Clinical Laboratory Standards Institute. [9]

The controls for all the confirmatory tests were  Escherichia More Details coli-ATCC 251922 and Klebsiella pneumoniae-ATCC 700603.

Potentiate disc diffusion technique

The Mueller-Hinton agar plate was inoculated with broth adjusted to 0.5 Mc Ferlands standard. The discs containing ceftazidime (30 mg), ceftazidime/clavulanic acid (30/10 mg), cefotaxime (30 mg), and cefotaxime/clavulanic acid (30/10 mg) were placed on the inoculated plate, with the distance between them being minimum of 40 mm. The plate was incubated overnight at 37°C. [5] If the zone of inhibition of cephalosporin/clavulanic acid is ≥5 mm than zone of inhibition of plain cephalosporin disc, the strain is considered to be ESBL-KP.

MIC by agar dilution technique

MIC of each strain was determined against ceftazidime, ceftazidime/clavulanic acid, cefotaxime, and cefotaxime/clavulanic acid. The range of dilutions of ceftazidime (256-0.016 mg/mL) and cefotaxime (256-0.008 mg/mL), with and without clavulanic acid was prepared. The turbidity of each strain was adjusted to get 10 7 CFU/mL. The spot inoculation of 0.1 mL of the adjusted broth was done on various concentration agar plates. The plates were incubated overnight at 37°C. [5] MIC of >2 mg/mL, in plates with plain cephalosporin, is considered to be ESBL producer. The reduction of MIC by ≥3 two-fold dilutions, in plates with clavulanic acid in comparison with plates with plain cephalosporins, is considered as ESBL-KP.

All the isolates were tested for the sensitivity against ciprifloxacin (5 mg), amikacin (30 mg), and co-trimoxazole (25 mg) (Hi Media). Multidrug resistance pattern was determined in all the isolates. A multidrug resistant isolate was defined as resistance to two or more drugs or drug classes of therapeutic relevance. [10]


Among 70 isolates, 52 (74%) were ESBL-KP. The number of Klebsiella pneumoniae isolated from various samples and their distribution are shown in [Table 1]. Most of the samples were blood (51); 40(57%) of them were ESBL-KP.

Table 1: Distribution of isolates among various samples from ICU patients

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All the ESBL-KP were multidrug resistant. Resistance was seen in one or two other group of drugs along with cephalosporins. Coresistance to other group of drugs was seen between 63 and 83% [Table 2].

Table 2: Resistance to other group of drugs among the isolates

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The patients in ICU are more predilicted to colonization and infection by the various pathogens. Klebsiella pneumoniae is one such pathogen that colonizes and causes infection in such patients. The species is commonest isolate from cases of neonatal sepsis accounting for great number of mortality rate. [3],[4] Klebsiella pneumoniae is the species in which the ESBL enzymes have been most commonly reported around the world. [11],[12] ICUs are the wards where large amount of empiric treatment including broad-spectrum antibiotics are used. Thus, this study was undertaken to know the prevalence of ESBL-KP in ICU at our institute.

Various samples such as blood, sputum, pus, catheter tips, endotracheal tips, and suctions were received for culture. ESBL-KP were isolated from 52 (74%) samples. Fifty-one samples were blood from septicemia patients, from different ICUs. Forty-five blood samples were from neonatal ICU, 36 of them were ESBL-KP. The high prevalence of ESBL-KP in septicemic individuals, majority being neonates, causes concern. The next to blood are indwelling catheter tips, 9 of them being colonized by ESBL-KP. These catheters are known to act as foci for systemic infections. The catheters will act as platform of colonization by other opportunistic pathogens. The ESBL trait plasmids can be transferred to the other species; this will herald the dissemination of ESBL organisms in systemic infection. As most of ESBL-KP are multidrug resistant, there will be great limitation over the choice of drug for treating the septicemia patients.

Coresistance to other group of drugs is quoted by other studies. [1],[2],[4] In our study, also the high prevalence of coresistance is observed against ciprofloxacin (78%), amikacin (63%), and co-trimoxazole (83%), that is in coordinance with other studies. [1],[2],[13] The molecular level detection of genes responsible for coresistance to other drugs was not feasible at our settings. But there are studies that quote the possible probable genes carried by ESBL-producing organisms. Alteration in membrane permeability has been accounted for concurrent resistance to fluroquinilones. [2] A conjugative plasmid, IncL/M, was found in another study conferring resistance to aminoglycosides. [1]

The development and spread of ESBLs have been most likely to be accounted to the inappropriate use of extended-spectrum β-lactums. [11],[14] Infection with strains expressing ESBL are a challenge for both microbiologists and clinicians as they are having less therapeutic options. Thus, antibiotic policies are mandatory and are to be strictly adhered to. Specifying the indications for use or cycling classes of antibiotics are some of the options to limit the selective pressure on nosocomial flora. [15]


The authors are thankful to Dr. M K Lalitha, for allowing to carry out the MIC by agar dilution method at Department of Microbiology, CMC Vellore.

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11. Peña C, Pujol M, Ardanuy C, Ricart A, Pallares R, Liñares J, et al. Epidemiology and Successful control of a large outbreak due to Klebsiella pneumoniae producing extended-spectrum b-lactamases. Antimicrob Agents Chemother 1998;42:53-8.
12. Jacoby GA, Sutton L. Properties of plasmids responsible for production of extended-spectrum b-lactamases. Antimicrob Agents Chemother 1991;35:164-9.
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1755-6783.85760


[Table 1], [Table 2]

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