|Year : 2019 | Volume
| Issue : 4 | Page : 593-594
Emerging atypical non-lactose-fermenting phenotypic variants of klebsiella pneumoniae and escherichia coli in admitted patients of a trauma centre
Vijeta Bajpai1, Purva Mathur2
1 Department of Microbiology, JPNATC, All India Institute of Medical Sciences, New Delhi, India
2 Department of Laboratory Medicine, JPNATC, All India Institute of Medical Sciences, New Delhi, India
|Date of Submission||14-Feb-2020|
|Date of Acceptance||26-Mar-2020|
|Date of Web Publication||18-May-2020|
Department of Laboratory Medicine, JPNATC, All India Institute of Medical Sciences, New Delhi
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Bajpai V, Mathur P. Emerging atypical non-lactose-fermenting phenotypic variants of klebsiella pneumoniae and escherichia coli in admitted patients of a trauma centre. Indian J Med Microbiol 2019;37:593-4
|How to cite this URL:|
Bajpai V, Mathur P. Emerging atypical non-lactose-fermenting phenotypic variants of klebsiella pneumoniae and escherichia coli in admitted patients of a trauma centre. Indian J Med Microbiol [serial online] 2019 [cited 2020 May 27];37:593-4. Available from: http://www.ijmm.org/text.asp?2019/37/4/593/284533
Klebsiella pneumoniae and Escherichia coli are facultative anaerobic, Gram-negative bacilli that ferment lactose and produce pink-pigmented colonies in MacConkey agar media. Up to 10% of E. coli isolates have historically been reported to be slow or non-lactose-fermenting variants that are termed as 'inactive', but non-lactose-fermenting K. pneumoniae strains are not known. Phenotypically, atypical colony morphological and unusual biochemical characteristics of these non-lactose fermenting are a challenge for clinical microbiologists to identify and suggest the therapeutic options to clinicians. This communication reports a sudden occurrence of 'atypical' phenotype of K. pneumoniae and E. coli at our centre.
The findings were observed at the Department of Microbiology of Jai-Prakash Narayan Apex Trauma Centre, All India Institute of Medical Science, New Delhi. All consecutive isolates of non-lactose, slow-fermenting (having atypical morphology) E. coli and K. pneumoniae from various clinical samples were studied for confirmatory identification and antimicrobial sensitivity by VITEK 2 (BioMeriux, Germany) and MALDI-TOF (BioMeriux, Germany). Patient's demographic details and clinical details were followed up.
We found three nonlactose-fermenting isolates (two K. pneumoniae and one E. coli) from 2 pus samples and one urine sample, respectively. Unlike the usual phenotypic morphology of K. pneumoniae (large shiny, mucoid and dark pink in colour), our three isolates of K. pneumoniae were small-to-medium size in appearance, shiny, non-lactose fermenting on MacConkey agar media [Figure 1]. On comparison of biochemical properties (VITEK-2), it was found that these atypical strains were negative for urease production, beta-galactosidase production, beta-xylosidase production, proline A utilisation and tyrosine A utilisation and positive for malate and lactate assimilation test in contrast to the ATCC control K. pneumoniae strain. On comparison of biochemical reactions of E. coli (VITEK-2), it was found that the atypical E. coli was negative for lactate alkalisation, alpha-galactosidase production and tyrosine A utilisation test. [Table 1] shows the comparison of various biochemical properties of various isolates of K. pneumoniae and E. coli. Our findings also highlighted that one of the atypical K. pneumoniae isolates was a pan-drug-resistant strain including colistin.
This change in phenotypic expression in K. pneumoniae and E. coli may be due to morphological plasticity, which is a survival strategy adopted in response to environmental stresses, such as antimicrobial exposure and other mechanical constraints. This phenomenon is well known in uropathogenic E. coli strains but is highly uncommon in K. pneumoniae strains. These observations challenge our traditional views of microbiological identification and testing and thus could drive the development of new and improved approaches to control multidrug-resistant bacteria in clinical settings.
Our study highlights that bacterial colony characteristics must be observed meticulously. To avoid misidentification of atypical variants of K. pneumoniae and E. coli, automated identification system is useful in clinical laboratory settings. For confirm identification, the atypical strains must be subjected to whole-genome sequencing, which will also help us identifying the genetic mechanism behind their morphological plasticity and phenotypic heterogenecity.
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Conflicts of interest
There are no conflicts of interest.
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