Inhibiting biofilm formation by Klebsiella pneumoniae B5055 using an iron antagonizing molecule and a bacteriophage

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Date: July 26, 2013
From: BMC Microbiology(Vol. 13, Issue 1)
Publisher: BioMed Central Ltd.
Document Type: Report
Length: 4,542 words
Lexile Measure: 1850L

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Author(s): Sanjay Chhibber1 , Deepika Nag1 and Shruti Bansal1

Background

Biofilms are cell-cell or solid surface-attached assemblages of microbes that are entrenched in a hydrated, self-produced matrix [1]. Bacteria growing in biofilms exhibit increased resistance to antimicrobials and host immune response compared to their freeliving, planktonic counterparts due to several reasons like restricted penetration of antimicrobials into a biofilm, decreased growth rate, and expression of possible resistance genes [2]. Klebsiella pneumoniae is an important biofilm forming organism responsible for a wide range of infections placing it among the eight most important nosocomial pathogens [3]. The threat of antibiotic resistance and their inability in breaking the biofilm structure has increased the likelihood that novel strategies for preventing or delaying the biofilm growth mode are urgently needed [4].

Bacteriophages infect bacteria, hijack their machinery, replicate intracellularly and are released by host cell lysis. They offer various advantages over antibiotics as antibiofilm agents because of their specific, non-toxic, self replicating and self limiting nature [5, 6]. Phage borne depolymerases degrade biofilm exopolysaccharide matrix that acts as a barrier for antimicrobials, infect the organisms and cause extensive biofilm disruption [7]. Since phages are rapidly removed from circulation once injected/ingested, are unable to penetrate the older biofilms which contain large number of metabolically inactive cells [8] thus it can be said that either phages or antibiotics when used alone do not stand a chance especially against biofilm associated bacterial infections. Therefore, treating biofilms with combinations of chemically distinct antimicrobials might be an effective strategy to kill some of these different cell types.

Iron is an essential factor in bacterial growth participating in oxygen and electron transport processes, essential for biofilm formation in bacteria [9, 10] where it regulates surface motility, promotes biofilm formation by stabilizing the polysaccharide matrix [11] and is considered critical for transition from planktonic to sessile existence. Thus, reducing iron availability has been proposed as a potential means to impair biofilm development by K . pneumoniae , Pseudomonas aeruginosa , Escherichia coli etc. [12-15]. In light of this emerging perspective, we undertook the present study to explore the possibility of using an iron antagonizing molecule and a bacteriophage alone as well as in combination to inhibit biofilm formation by K . pneumoniae B5055.

Methods

Bacterial strain, phages and growth conditions

K . pneumoniae B5055 (O1:K2) obtained originally from Dr. Mathia Trautmann, Department of Medical Microbiology and Hygiene, University of Ulm, Germany; KPO1K2 and NDP, depolymerase and non-depolymerase producing phages against K . pneumoniae B5055, previously characterized in our laboratory [16-18] were used in the present study. As reported earlier by Verma et al. [16] phage KPO1K2 possesses icosahedral head with pentagonal nature with apex to apex head diameter of about 39 nm. It has a genome of 42 kbps, a short noncontractile tail (10 nm) and a T7 like structural protein pattern suggesting its inclusion into family Podoviridae with a designation of T7-like lytic bacteriophage.

The titre of the bacteriophage preparation was estimated by the soft agar overlay method [19] and was expressed as plaque forming...

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Gale Document Number: GALE|A534561078