How to identify & Confirm Klebsiella in Laboratory



The genus klebsiella is another member of the group enterobacteriaceae and many of them are resistant to many antibiotics.



Klebsiella are gram negative lactose fermenting bacilli which have distinctive features of the presence of polysaccharide capsule and absence of motility.so that it gives characteristic glistening, mucoid colonies due to their capsule. And also it contain several types of pilli which aid in adherence to respiratory and urinary epithelium. K.pneumoniae is the most common organism of this genus, which can cause lobar pneumonia. Also K.oxytoca, K.granulomatis and K.variicola are known as other human pathogenic organisms.

Generally they are facultative anerobic organisms and responsible for variety of human infections such as, bacteremia, hepatic infections and many unusual infections including endocarditis, peritonitis, necrotizing fasciitis, pyomyositis etc. Klebsiella pulmonary infections are characterized by extensive hemorrhagic consolidation of lungs. However, advance age, diabetes, chronic respiratory disease and alcoholism may act as predisposing factors for Klebsiella infections.



As you know first we need to look the colony morphology. klebsiella spp grow readily on ordinary media and show characteristic large glistning ,mucoid colonies with yeasty odor. Since it is a lactose fermenter, the colonies on macConkey agar is pink and pink pigment usually diffusing in to the surrounding agar.

gram stain



The gram stain show gram negative rod which is similar to other coliforms.

The oxidase test and the motility give negativity. here the motility test is important because klebsiella is non motile while other commonly encountered lactose fermenting coliforms( E.coli, Enterobacter and Citrobacter) are motile.

Also we can look for the KIA reaction which is A/A gas-negative and H2S negative. Other biochemical tests that we can use include,

  • indole test – negative
  • lysine decarboxylase- positive
  • urease test- positive
  • methyl red –usually negative and Voges –proskauer- positive
  • simmons’ citrate-positive

Many other sugar fermentation results can also be used for the diagnosis. But above biochemicals are the commonly used tests in clinical laboratory set up. ABST for the isolated pathogens should be done along with the clinical history since Antibiotics are the treatment for Klebsiella infections.

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