K pneumoniae: Introduction, Classification, Pathogenicity, Laboratory Diagnosis and Treatment

K pneumoniae: Introduction, Classification, Pathogenicity, Laboratory Diagnosis and Treatment

Introduction of K pneumoniae

Klebsiella is from the surname of  German-Swiss microbiologist Edwin Klebs (1834–1913). Klebsiella is a genus of Gram-negative, oxidase-negative, fimbriated, non -motile, non-sporing rod-shaped bacteria with a prominent polysaccharide-based capsule and having size o,f   0.5 -0.8 µm wide to 1 -2  µm. They are found everywhere in nature and also in bacterial flora in our intestines. K pneumoniae scientific classification is as follows

  • Domain: Bacteria
  • Phylum: Proteobacteria
  • Class: Gammaproteobacteria
  • Order: Enterobacterales
  • Family: Enterobacteriaceae
  • Genus: Klebsiella
  • Species:  pneumoniae
  • Subspecies of Klebsiella pneumoniae are-
  • Klebsiella pneumoniae subspecies ozaenae
  • Klebsiella pneumoniae subspecies  pneumoniae
  • Klebsiella pneumoniae subspecies rhinoscleromatis

Pathogenicity of K pneumoniae

K pneumoniae may cause severe bronchopneumonia, urinary tract infections, nosocomial infections, wound infections, septicemia, meningitis, and rarely diarrhea too.

Isolation of K pneumoniae  in Laboratory 

Klebsiella pneumoniae isolated from septicemic patient blood culture; on the basis of the following tests:-

Blood culture bottle incubated into Bactec.

After 23 hours of incubation, Bactec indicated positive.

The positive bottle was then sub-cultured into solid media Chocolate agar, blood agar, and MacConkey agar.

After overnight incubation, growth was seen in all three plates.

K pneumoniae on MacConkey’s agar

On MacConkey agar, the colonies appeared large, mucoid, and pink in color.

The mucoid nature of colonies is due to capsular material produced by the organisms.

Gram stain

Short thick Gram-negative rods

Motility by hanging drop preparation method


Biochemical tests of Klebsiella pneumoniae on MacConkey’s agar

Catalase test -Positive

Oxidase -Negative

Nitrate reduction test- Reduced to nitrite

Triple Sugar Iron  (TSI) agar


No hydrogen sulfide (H2S) production

Production of gas

Motility Indole Urease (MIU) test

Non-motile because of only strict growth around the stab line

Urea hydrolyzation test– positive

Indole -Negative

Note: Klebsiella oxytoca is indole positive.

Citrate Utilization Test


Fermentation of sugars (glucose, lactose, and mannitol )- acid and gas

Methyl red test-Negative

Voges-Proskauer test-Positive

Lysine decarboxylase test-Positive

Antibiotic sensitivity test

The antibiotic sensitivity test was also suggestive for Klebsiella pneumoniae because of ampicillin resistance which is intrinsically resistant.

The following antibiotics are used for antibiotics sensitivity testing-

  • Gentamycin
  • Doxycycline
  • Ciprofloxacin
  • Ofloxacin 
  • Levofloxacin 
  • Nitrofurantoin  ( in case of pf urine only)
  • Chloramphenicol
  • Cotrimoxazole
  • Ceftriaxone 
  • Cefotaxime
  • Cefixime
  • Meropenem 
  • Amikacin 
  • Aztreonam 
  • Penicillin tazobactam 
  • Ceftazidime 
  • Cefepime 
  • Imipenem 
  • Tobramycin
  • Colistin (E-strip) 
  • Polymyxin B (E-strip) 

Treatment of K pneumoniae

Clinical isolates of Klebsiella pneumoniae are resistant to a wide range of antimicrobial agents like ampicillin, Amoxycillin, and carbenicillin. This resistance is due to the R plasmid present in these organisms. Organisms are usually sensitive to cephalosporins, trimethoprim, nitrofurantoin, amoxicillin-clavulanic acid, and aminoglycosides. However, plasmid-mediated resistance to gentamycin and various cephalosporins has been reported in hospital strains.

#Related Videos

Klebsiella pneumoniae Mucoid lactose fermenter colonies on Macconkey agar and Biochemical Tests-

Another beautiful mucoid colony morphology of K pneumoniae is shown below video clip-

Further Readings

  1. Bailey & Scott’s Diagnostic Microbiology. Editors: Bettey A. Forbes, Daniel F. Sahm & Alice S. Weissfeld, 12th ed 2007, Publisher Elsevier.
  2. Clinical Microbiology Procedure Handbook Vol. I & II, Chief in editor H.D. Isenberg, Albert Einstein College of Medicine, New York, Publisher ASM (American Society for Microbiology), Washington DC.
  3. Colour Atlas and Textbook of Diagnostic Microbiology. Editors: Koneman E.W., Allen D.D., Dowell V.R. Jr, and Sommers H.M.
  4. Cowan & Steel’s Manual for identification of Medical Bacteria. Editors: G.I. Barron & R.K. Felthani, 3rd ed 1993, Publisher Cambridge University Press.
  5. Jawetz, Melnick and Adelberg’s Medical Microbiology. Editors: Geo. F. Brook, Janet S. Butel & Stephen A. Morse, 21st ed 1998, Publisher Appleton & Lance, Co Stamford Connecticut.
  6. Mackie and Mc Cartney Practical Medical Microbiology. Editors: J.G. Colle, A.G. Fraser, B.P. Marmion, A. Simmous, 4th ed, Publisher Churchill Living Stone, New York, Melborne, Sans Franscisco 1996.
  7.  Manual of Clinical Microbiology. Editors: P.R. Murray, E. J. Baron, M. A. Pfaller, F. C. Tenover and R. H. Yolken, 7th ed 2005, Publisher ASM, USA
  8.  Textbook of Diagnostic Microbiology. Editors: Connie R. Mahon, Donald G. Lehman & George Manuselis, 3rd edition2007, Publisher Elsevier.
  9. Topley & Wilsons Principle of Bacteriology Vol I, Editors: M.T. Parker & L.H. Collier, 8th ed 1990, Publisher Edward Arnold publication, London.
  10. District Laboratory Practice in  Tropical Countries  –  Part-2-   Monica Cheesebrough-   2nd Edn Update
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