Characterization of Antibacterial Activities of Eastern Subterranean Termite, Reticulitermes flavipes, against Human Pathogens.

Yuan Zeng,Xing Ping Hu,Sang-Jin Suh,Erjun Ling

doi:10.1371/journal.pone.0162249

Abstract

The emergence and dissemination of multidrug resistant bacterial pathogens necessitate research to find new antimicrobials against these organisms. We investigated antimicrobial production by eastern subterranean termites, Reticulitermes flavipes, against a panel of bacteria including three multidrug resistant (MDR) and four non-MDR human pathogens. We determined that the crude extract of naïve termites had a broad-spectrum activity against the non-MDR bacteria but it was ineffective against the three MDR pathogens Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus (MRSA), and Acinetobacter baumannii. Heat or trypsin treatment resulted in a complete loss of activity suggesting that antibacterial activity was proteinaceous in nature. The antimicrobial activity changed dramatically when the termites were fed with either heat-killed P. aeruginosa or MRSA. Heat-killed P. aeruginosa induced activity against P. aeruginosa and MRSA while maintaining or slightly increasing activity against non-MDR bacteria. Heat-killed MRSA induced activity specifically against MRSA, altered the activity against two other Gram-positive bacteria, and inhibited activity against three Gram-negative bacteria. Neither the naïve termites nor the termites challenged with heat-killed pathogens produced antibacterial activity against A. baumannii. Further investigation demonstrated that hemolymph, not the hindgut, was the primary source of antibiotic activity. This suggests that the termite produces these antibacterial activities and not the hindgut microbiota. Two-dimensional gel electrophoretic analyses of 493 hemolymph protein spots indicated that a total of 38 and 65 proteins were differentially expressed at least 2.5-fold upon being fed with P. aeruginosa and MRSA, respectively. Our results provide the first evidence of constitutive and inducible activities produced by R. flavipes against human bacterial pathogens.

Highlights

In recent years, insects have been recognized for having potent immune defenses that produce constitutive and inducible antimicrobial compounds to combat various pathogens [1]
In order to understand the biological range of antibacterial activity of R. flavipes cellfree extract (CFE), we tested a panel of non-multidrug resistant (MDR) and MDR human bacterial pathogens for their susceptibility
The CFE prepared from the whole body of naïve termite displayed significant inhibitory activity against the five non-MDR bacteria (Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and E. coli K12) but it was inactive against the three MDR pathogens (Table 2)

Summary

Introduction

Insects have been recognized for having potent immune defenses that produce constitutive and inducible antimicrobial compounds to combat various pathogens [1]. They have been targeted as a potential source of antimicrobial compounds [2, 3]. When pathogens break through morphological barriers, insects evoke innate immune responses comprised of cellular and humoral reactions. Cellular reactions are hemocyte-mediated and include phagocytosis and encapsulation, while humoral reactions involve the production of antimicrobial proteins and activation of enzymatic cascades [5]. Reported insect AMPs include lysozymes, cecropins, attacins, defensins, and proline rich peptides [6, 7]

Methods

Results

Conclusion