In vitro Multi-Species Biofilms of Methicillin-Resistant Staphylococcus aureus and Pseudomonas aeruginosa and Their Host Interaction during In vivo Colonization of an Otitis Media Rat Model.

Mukesh K Yadav,Yoon Young Go,Gi Jung Im,Jae-Jun Song,Sung-Won Chae

doi:10.3389/fcimb.2017.00125

Mukesh K Yadav, Yoon Young Go + Show 3 more

Open Access

https://doi.org/10.3389/fcimb.2017.00125

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Abstract

Staphylococcus aureus (SA) and Pseudomonas aeruginosa (PA) are known to cause biofilm-related infections. MRSA and PA have been frequently isolated from chronically infected wounds, cystic fibrosis, chronic suppurative otitis media (CSOM), and from indwelling medical devices, and these bacteria co-exist; however, their interaction with each-other or with the host is not well known. In this study, we investigated MRSA and PA multi-species biofilm communities in vitro and their interaction with the host during in vivo colonization using an OM rat-model. In-vitro biofilm formation and in-vivo colonization were studied using CV-microtiter plate assay and OM rat-model respectively. The biofilms were viewed under scanning electron microscope and bacteria were enumerated using cfu counts. The differential gene expressions of rat mucosa colonized with single or multi-species of MRSA or PA were studied using RNA-sequencing of total transcriptome. In multi-species in-vitro biofilms PA partially inhibited SA growth. However, no significant inhibition of MRSA was detected during in-vivo colonization of multi-species in rat bullae. A total of 1,797 genes were significantly (p < 0.05) differentially expressed in MRSA or PA or MRSA + PA colonized rat middle ear mucosa with respect to the control. The poly-microbial colonization of MRSA and PA induced the differential expression of a significant number of genes that are involved in immune response, inflammation, signaling, development, and defense; these were not expressed with single species colonization by either MRSA or PA. Genes involved in defense, immune response, inflammatory response, and developmental process were exclusively up-regulated, and genes that are involved in nervous system signaling, development and transmission, regulation of cell growth and development, anatomical and system development, and cell differentiation were down-regulated after multi-species inoculation. These results indicate that poly-microbial colonization induces a host response that is different from that induced by single species infection.

Highlights

Staphylococcus aureus and Pseudomonas aeruginosa (PA) are two major opportunistic pathogens that cause community-acquired and nosocomial infections
To assess the growth of methicillin-resistant S. aureus (MRSA) and PA in single and multi-species biofilms, in vitro single and multi-species biofilms were grown on polystyrene plates that allowed for bacterial attachment and biofilm formation
The OD570-values of single species biofilms of MRSA and PA were 0.7 and 1.8, respectively; that of the multi-species biofilm was 2.0. These results indicated that total biomass of multi-species biofilms were higher than that of single species biofilms, which might be because of the accumulation of extracellular polysaccharide (EPS) and cells from both species

Summary

Introduction

Staphylococcus aureus and Pseudomonas aeruginosa (PA) are two major opportunistic pathogens that cause community-acquired and nosocomial infections. S. aureus and PA are the most prevalent pathogens that colonize structurally abnormal airways such as those in cystic fibrosis (CF) and other chronic obstructive lung diseases (Lyczak et al, 2002; Hubert et al, 2013). They are frequently found together in chronic wound infections (Gjødsbøl et al, 2006; Fazli et al, 2009). As a result of the competitive interactions between S. aureus and PA, an altered colony morphology strains called small colony variants (SCVs) emerges Those SCVs are more persistent and more antibiotic-resistant strains than normal S. aureus (Nair et al, 2014)

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