title: Depolymerase improves gentamicin efficacy during Klebsiella pneumoniae induced murine infection.
abstract: BACKGROUND
  Presence of capsule enhances the virulence of bacteria that cause pneumonia, meningitis, cystic fibrosis, dental caries, periodontitis. Capsule is an important virulence factor for Klebsiella pneumoniae and infections due to this pathogen have been associated with high mortality rates. In the present study, use of an Aeromonas punctata derived capsule depolymerase against K. pneumoniae, to reinstate the efficacy of gentamicin during pneumonia and septicemia was investigated.
  
  
  METHODS
  Depolymerase was administered in mice intraperitoneally (50 μg) alone as well in combination with gentamicin (1.5 mg/kg), 24 h post infection during acute lung infection and 6 h later during septicemia. Bacterial load, neutrophil infiltration and cytokine levels were estimated. The immunogenicity of protein was also studied.
  
  
  RESULTS
  In comparison to groups treated with gentamicin alone, combination treatment with depolymerase and gentamicin significantly reduced (P < 0.01) bacterial titer in the lungs, liver, kidney, spleen and blood of experimental animals. Highly significant reduction in neutrophil infiltration and levels of pro-inflammatory and anti-inflammatory cytokines was also observed. This indicated an efficient capsule removal by the enzyme, that improved gentamicin efficacy in vivo. Although the enzyme was found to be immunogenic, but no significant reduction in treatment efficacy was observed in the preimmunized as well as naïve mice. In addition, as confirmed through flow cytometry, the hyperimmune sera raised against the enzyme did not neutralize its activity.
  
  
  CONCLUSIONS
  The results confirm that administration of enzyme 'depolymerase' along with gentamicin not only checked the virulence of K. pneumoniae in vivo but it also increased its susceptibility to gentamicin at a lower concentration. Such a strategy would help to avoid exposure to higher concentration of gentamicin. Moreover, since this decapsulating protein does not possess a lytic activity therefore there would be no chances of development of bacterial resistance against it. Therefore, it should be studied further for its successful inclusion in our prophylactic/therapeutic regimes.
authors.forename: Shruti
authors.initials: S
authors.lastname: Bansal
authors.forename: Kusum
authors.initials: K
authors.lastname: Harjai
authors.affiliation: Department of Microbiology, Panjab University, Sector-14, Chandigarh 160014, India. sanjaychhibber8@gmail.com.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Chhibber
mesh_terms: D000333:Aeromonas / Q000737:chemistry / Q000201:enzymology*; D000818:Animals; D016207:Cytokines / Q000276:immunology; D005260:Female; D005839:Gentamicins / Q000008:administration & dosage*; D006801:Humans; D007155:Immunologic Factors / Q000008:administration & dosage; D007710:Klebsiella Infections / Q000188:drug therapy* / Q000276:immunology / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000201:enzymology* / Q000502:physiology; D008168:Lung / Q000276:immunology / Q000382:microbiology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D020556:Neutrophil Infiltration; D011133:Polysaccharide-Lyases / Q000008:administration & dosage*; D013047:Specific Pathogen-Free Organisms
chemical_list: D016207:Cytokines; D005839:Gentamicins; D007155:Immunologic Factors; D011133:Polysaccharide-Lyases