Year : 2008 | Volume
: 51 | Issue : 3 | Page : 370--372
Extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in diabetic foot infections
Ami Y Varaiya, Jyotsana D Dogra, Manasi H Kulkarni, Pallavi N Bhalekar
Department of Microbiology, S. L. Raheja Hospital, Mumbai, India
Ami Y Varaiya
Department of Laboratory Medicine, S. L. Raheja Hospital, Mahim (West), Mumbai - 400 016
Aims: Diabetic foot lesions are a major medical, social, and economic problem and are the leading cause of hospitalization for patients with diabetes, worldwide. ESBL-producing bacteria may not be detectable by routine disc diffusion susceptibility test, leading to inappropriate use of antibiotics and treatment failure. There is not much information on ESBL-producing organisms causing diabetic foot infection. An attempt was therefore made to study the ESBL-producing Escherichia coli and Klebsiella pneumoniae in diabetic foot patients with type 2 diabetes mellitus. Materials and Methods: A total of 134 isolates of E. coli and K. pneumoniae were obtained from tissue, pus swab, and wound swab samples from diabetic foot ulcers submitted for routine microbiological analysis during the period January to December 2005 from patients with diabetic foot infections who had type 2 diabetes mellitus, attending S. L. Raheja Hospital. The above isolates were tested for antimicrobial susceptibility by disc diffusion technique according to clinical and laboratory standards institute (CLSI) guidelines. The screening for ESBL production was done by phenotypic confirmatory test using ceftazidime disc in the presence and absence of clavulanic acid as recommended by CLSI. Results: Among the 134 isolates, 54 (40.29%) were E. coli and 80 (59.70%) were K. pneumoniae; among which, ESBL production was detected in 31 (23.13%) isolates. Of these 31, 15 (48.38%) were E. coli and 16 (51.61%) were K. pneumoniae. All the ESBL-producing isolates were found to be 100% sensitive to carbapenem (imipenem and meropenem). Mortality was found to be 3.22%, the cause of death being septicemia leading to multiple organ failure. Conclusions: The prevalence of ESBLs among members of Enterobacteriaceae constitutes a serious threat to the current beta-lactam therapy, leading to treatment failure and consequent escalation of costs. There is an urgent need to emphasize rational use of drugs to minimize the misuse of available antimicrobials.
|How to cite this article:|
Varaiya AY, Dogra JD, Kulkarni MH, Bhalekar PN. Extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in diabetic foot infections.Indian J Pathol Microbiol 2008;51:370-372
|How to cite this URL:|
Varaiya AY, Dogra JD, Kulkarni MH, Bhalekar PN. Extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in diabetic foot infections. Indian J Pathol Microbiol [serial online] 2008 [cited 2020 Feb 19 ];51:370-372
Available from: http://www.ijpmonline.org/text.asp?2008/51/3/370/42513
Infection is a common sequel of diabetic foot ulceration and trauma, which, once established, progressively worsens and becomes more difficult to treat. Polymicrobial infections include aerobic gram-positive cocci ( Staphylococcus aureus ), gram-negative bacilli ( Escherichia coli, Klebsiella and Proteus species ), and anaerobes ( Bacteroides species and Peptostreptococcus ). 
Extended-spectrum beta-lactamases (ESBLs) are defined as beta-lactamases capable of hydrolyzing oxyimino-cephalosporins and are inhibited by beta-lactamase inhibitors. The first extended-spectrum beta-lactamase (ESBL) isolates were discovered in western Europe in mid-1980s. They are found in a variety of Enterobacteriaceae species; the majority of ESBL-producing strains are K. pneumoniae, K. oxytoca, and E. coli . 
Being plasmid mediated, they are easily transmitted among members of Enterobacteriaceae, thus facilitating the dissemination of resistance not only to beta-lactams but also to other commonly used antibiotics such as quinolones and aminoglycosides. The chromosomally mediated beta-lactamase production is mainly through expression of AmpC gene, which is either constitutive or inducible. 
In recent years, there has been an increase in the incidence and prevalence of ESBLs.
Currently there is paucity of data on ESBL-producing organisms from diabetic foot infections. Therefore, we carried out a study to find the occurrence of ESBL-producing gram-negative bacteria in diabetic foot infection with type 2 diabetes mellitus, and to determine the clinical outcome of these patients.
Materials and Methods
With universal safety precautions, samples were collected from patients admitted to S. L. Raheja Hospital, a tertiary care hospital for diabetic patients. The samples were transported to the laboratory without delay.
The specimens included 65 tissues, 63 pus swabs, 6 wound swabs from diabetic foot ulcers. All the samples were taken from inpatients. Patients with nonhealing diabetic foot ulcers for the preceding 2 weeks with empirical antibiotic treatment were included in the study.
Samples were cultured on brain heart infusion blood agar (BHIA) and Mac Conkey's agar. The specimens were processed for isolation and identification based on standard laboratory technique. 
Antimicrobial sensitivity testing was performed on Mueller Hinton agar plates with commercially available discs (Hi-Media, Mumbai) by Kirby Bauer disc diffusion method. The results were recorded and interpreted as per CLSI recommendations. 
ATCC Escherichia coli 25922 was used as a control.
Phenotypic confirmatory test
Combined disc diffusion method 
While performing antibiotic testing, ceftazidime (30 µg) and ceftazidime/clavulanic acid (30/10 µg) discs were placed on Mueller Hinton agar plate on which a 0.5 McFarland of test organism was swabbed. Organism was considered as ESBL producer if there was ≥ 5 mm increase in zone diameter of ceftazidime/clavulanate disc and that of ceftazidime disc alone.
Among the 134 isolates, 54 (40.29%) were E. coli and 80 (59.70%) were K. pneumoniae. Of these 134 strains tested by phenotypic confirmatory test, 31 (23.13%) were found to be ESBL producers, of which, 15 (48.38%) were E. coli and 16 (51.61%) were K. pneumoniae. Among these 31, 67.74% were males and 32.26% were females, M:F ratio being 2.1:1.
Antibiotic treatment was given according to the antibiotic susceptibility report [Table 1]. A combination of carbapenem, amikacin and pipracillin/tazobactam was given to the patients. The average hospital stay was 15 days.
Mortality was found to be 3.22%, the cause of death being septicemia due to multiple organ failure.
Enterobacteria are an important group in community- and hospital-acquired infections. They are common precipitants of sepsis by virtue of the inflammatory response, activated by endotoxins present in the gram-negative cell wall. Patients with diabetes mellitus and dialysis patients are at high risk for enterobacteria infection. It has been estimated that 15% of diabetic patients develop an ulcer on foot and ankle as a common sequel to trauma. The emergence of plasmid-mediated ESBLs among members of Enterobacteriaceae has increased worldwide.
Recent studies from India have reported prevalence of ESBL producers to be as high as 68%.  Babypadmini et al. have shown 40% of K. pneumoniae isolates and 41% of E. coli isolates to be ESBL producers in their study cohort.  Another study reported an incidence of 58% for ESBL-producing E. coli . 
Kumar et al. have reported 19.2% of E. coli isolates and 21.2% of K. pneumoniae isolates as ESBL producers. 
Currently there is paucity of data on the prevalence of ESBLs in diabetic foot infection. In a study conducted in Brazil, the prevalence was only 6% among E. coli isolates.  Arti Kapil et al. have reported 54.5% E. coli isolates to be ESBL producers, which have caused diabetic foot infections.  We report 51.61% of K. pneumoniae isolates and 48.38% of E. coli isolates to be ESBL producers.
Phenotypic confirmatory test was carried out using double disc diffusion test as recommended by CLSI, which is a very convenient method.  ESBL-producing E. coli and K. pneumoniae were found to be sensitive to carbapenem, making it the drug of choice for antibiotic treatment in ESBL infections.
The presence of ESBLs should be confirmed using E strip method.  It is a very sensitive and reproducible method. But as the E strips are very costly, this test was not carried out in our study. Manual minimum inhibitory concentration (MIC) was not carried out as it was time consuming and tedious for all the ESBL-producing clinical isolates obtained in the present study. A combination of carbapenem, amikacin, and pipracillin/tazobactam was given to the patients.
One patient expired due to septicemia leading to multiple organ failure, mortality rate being 3.22%.
Thus the prevalence of ESBLs among members of Enterobacteriaceae constitutes a serious threat to the current beta-lactam therapy, leading to treatment failure and consequent escalation of costs. There is an urgent need to emphasize rational use of drugs to minimize the misuse of available antimicrobials.
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