Antimicrobial mechanisms against Acinetobacter calcoaceticus of rat polymorphonuclear leukocyte granule extract

Abstract

The antimicrobial mechanisms of rat polymorphonuclear leukocyte granule extract and isolated extract fractions against Acinetobacter calcoaceticus were examined. Crude granule extract and a fraction containing low-molecular-weight cationic peptides (peak D) reduced the viability of A. calcoaceticus and inhibited the uptake of radiolabeled macromolecule precursors by cells. The inhibitory activity observed with peak D was not as great as that of crude granule extract containing equivalent amounts of peak D protein. Crude extract also inhibited incorporation of uracil into trichloroacetic acid-precipitable material, while no isolated fraction, including peak D, had any substantial effect on incorporation. The antimicrobial activities of crude granule extract were more sensitive to boiling than those of isolated peak D. Preincubation of A. calcoaceticus with either crude granule extract or a fraction (peak B) possessing proteolytic activity but lacking any antimicrobial activity caused cells to become sensitive to a subinhibitory concentration of actinomycin D, suggesting that granule extract and peak B increase the outer membrane permeability of A. calcoaceticus. The antimicrobial granule extract fraction, peak D, did not affect outer membrane permeability. These results suggest that rat polymorphonuclear leukocyte granule extract reduces the viability of A. calcoaceticus by inhibiting the transport and incorporation of macromolecule precursors and that either whole granule extract is required for complete antimicrobial activity or an unidentified component is responsible for antimicrobial activity in addition to peak D. The granule extract activity that increases outer membrane permeability does not appear to be directly responsible for the observed decrease in viability.

Purification and antimicrobial properties of three defensins from rat neutrophils

“…These included S. aureus 502A, two gram-negative bacteria, two fungi, and, to a lesser extent, an enveloped virus. Because we purified RatNP-1, -3, and -4 to homogeneity and we used different microbial targets and assay conditions, it is not possible to compare our studies directly with those of Modrzakowski et al (17,18,25,28). Nevertheless, our data confirm their report that cationic, lowmolecular-weight antimicrobial peptides exist in rat PMN.…”

“…Although defensins have not heretofore been described in rat PMN, Modrzakowski et al reported that an extract prepared from rat PMN exerted antibacterial activity against certain bacteria (17,18,24,25,28), and they associated the activity of these extracts with small cationic peptides. Because rats are widely used in experimental models of infection, precise characterization of their antimicrobial effector molecules is desirable.…”

Neutropenia exacerbates infection by Acinetobacter baumannii clinical isolates in a murine wound model

“…Clinical studies have shown that A. baumannii is one of the most frequently isolated gram-negative bacteria in neutropenic febrile patients in nosocomial settings, ( Karim et al, 1991 ; Fukuta et al, 2013 ; Yadegarynia et al, 2013 ; Kim et al, 2014 ) particularly after prolonged hospitalization ( Wisplinghoff et al, 2004 ). Previous studies have also shown that neutrophils ( van Faassen et al, 2007 ; Qiu et al, 2009 ) and neutrophil-recruiting chemokines ( Zhao et al, 2011 ) are present at the site of A. baumannii infection, and neutrophil granule extract is bactericidal to other species of Acinetobacter ( Loeffelholz and Modrzakowski, 1988 ). However, the contribution of neutrophils in host resistance to cutaneous A. baumannii infection has not been directly investigated.…”