Modeling Klebsiella pneumoniae Pathogenesis by Infection of the Wax Moth Galleria mellonella

Abstract

The implementation of infection models that approximate human disease is essential for understanding pathogenesis at the molecular level and for testing new therapies before they are entered into clinical stages. Insects are increasingly being used as surrogate hosts because they share, with mammals, essential aspects of the innate immune response to infections. We examined whether the larva of the wax moth Galleria mellonella could be used as a host model to conceptually approximate Klebsiella pneumoniae-triggered pneumonia. We report that the G. mellonella model is capable of distinguishing between pathogenic and nonpathogenic Klebsiella strains. Moreover, K. pneumoniae infection of G. mellonella models some of the known features of Klebsiella-induced pneumonia, i.e., cell death associated with bacterial replication, avoidance of phagocytosis by phagocytes, and the attenuation of host defense responses, chiefly the production of antimicrobial factors. Similar to the case for the mouse pneumonia model, activation of innate responses improved G. mellonella survival against subsequent Klebsiella challenge. Virulence factors necessary in the mouse pneumonia model were also implicated in the Galleria model. We found that mutants lacking capsule polysaccharide, lipid A decorations, or the outer membrane proteins OmpA and OmpK36 were attenuated in Galleria. All mutants activated G. mellonella defensive responses. The Galleria model also allowed us to monitor Klebsiella gene expression. The expression levels of cps and the loci implicated in lipid A remodeling peaked during the first hours postinfection, in a PhoPQ-and PmrAB-governed process. Taken together, these results support the utility of G. mellonella as a surrogate host for assessing infections with K. pneumoniae. In 1890, Robert Koch formulated Koch's postulates as general guidelines for identifying disease-causing organisms. One century later, Stanley Falkow established the molecular version of Koch's postulates, this time to guide the identification of microbial genes encoding virulence factors. One of the key points of the molecular postulates is to test the virulence of a microorganism with an inactivated candidate virulence gene in an appropriate animal model. Therefore, the use of animal models to identify the virulence factors of human pathogens is indispensable. Currently, identification and characterization of novel virulence factors rely largely on assessing mutant bacteria for growth in the organs of infected mice. The dependence on mouse infection models limits large-scale analysis of virulence due to the large number of animals needed to obtain statistically significant results.To circumvent these issues, the search for alternative host models is ongoing. Ideally, these alternative models should be easy to maintain and infect, should be amenable to genetic manipulation, and should model aspects of vertebrate defenses upon infection, chiefly the immune response. The immune defense consists of two main parts, an innate and an adaptive response, wit...

Mechanisms of Increased Resistance to Chlorhexidine and Cross-Resistance to Colistin following Exposure of Klebsiella pneumoniae Clinical Isolates to Chlorhexidine

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Eugenol in combination with lactic acid bacteria attenuates Listeria monocytogenes virulence in vitro and in invertebrate model Galleria mellonella

“…Consequently, insect models have been proposed as cost-effective and easy alternatives that generate valid data on microbial virulence (Jander et al, 2000;Mylonakis et al, 2005). Larvae of the greater wax moth (Galleria mellonella) have been used to study microbial pathogenesis in a wide array of organisms, including Pseudomonas aeruginosa (Jander et al, 2000;Miyata et al, 2003), Burkholderia cepacia (Seed & Dennis, 2008), Burkholderia mallei (Schell et al, 2008), Bacillus cereus (Fedhila et al, 2006), Acinetobacter baumannii (Peleg et al, 2009), Klebsiella pneumoniae (Insua et al, 2013), several pathogenic fungi (Cotter et al, 2000;Mylonakis et al, 2005;Reeves et al, 2004) and Listeria monocytogenes (Joyce et al, 2010;Mukherjee et al, 2010Mukherjee et al, , 2011.…”

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