doi.org/10.36721/PJPS.2020.33.5.REG.1933-1937.1 Pak. J. Pharm. Sci., Vol.33, No.5, September 2020, pp.1933-1937 1933 Co-infection with Pseudomonas aeruginosa impacts virulence of Staphylococcus aureus and intensifies the severity of infection Affhan Shoaib 1 *, Nazir Ahmed Lone 1 and Xin Yi 2 1 Department of Bioscience, Barrett Hodgson University, Karachi, Pakistan 2 Department of Biotechnology, Dalian Medical University, Dalian, PR China Abstract: Multi-specie infections display diverse interactions among pathogens that influence the severity of disease. Staphylococcus aureus and Pseudomonas aeruginosa are the two most important opportunistic, nosocomial and drug- resistant pathogens. Poly-infections due to S. aureus and P. aeruginosa are more destructive and result in worse patient outcome than mono-infection. The two organisms are commonly isolated from cystic fibrosis respiratory cultures. Studies demonstrated that S. aureus pre-colonization among cystic fibrosis patients is a hazardous for beginning P. aeruginosa aviation route infection. This work meant to explore the impact of P. aeruginosa on the destructiveness of S. aureus and the level of disease's seriousness by utilizing in-vitro co-culture and host cell model. The outcomes showed that P. aeruginosa outcompetes and suppresses the growth of S. aureus when co-cultured. The host factors expression profile indicated elevated expression of TNFα, IL-6 and IL-12, recommending the unique mechanism of host cell healing inhibition by multispecies. Co-infection resulted in significant increase in IL-8 together with the 10-fold induction of iNOS expression when contrast with S. aureus mono-infection. This indicates that the presence of P. aeruginosa heads the infection towards more severity and complications and delays cell healing process. Keywords: P. aeruginosa; S. aureus, co-infection, inter-specie interactions. INTRODUCTION Most of the infections occur due to multi-specie colonization by pathogens and within such multi-species infections, pathogens unveil distinctive communications that affect the severity of disease. In spite of the fact that this reality has been acknowledged since the time of Pasteur, vast majority of investigations have been centered around a mono-bacterial species grown in isolation (Pasteur and Joubert, 1877). A little is known about interspecies interactions in poly-microbial infections. S. aureus and P. aeruginosa are the two most important opportunistic, nosocomial and antibiotic resistant pathogens. Research literature proposes that S. aureus and P. aeruginosa poly-infections are more destructive and/or result in worse patient outcomes than mono-infections (Pastar et al., 2013; Rosenbluth et al., 2004; Hendricks et al., 2001). P. aeruginosa is a Gram-negative bacterium with high level of adaptability and the bacterium is unsusceptible to many antimicrobials (Pearson et al., 2000). P. aeruginosa is an opportunistic bacterium that out-competes other species such as S. aureus in cystic fibrosis lung, becoming dominant and difficult to eradicate. S. aureus is one of the most important Gram positive opportunists, causes a range of infections from skin to food-borne illnesses and other frightful infections (Lowy, 1998). From 1995 to 2005, the infection prevalence of S. aureus in children with cystic fibrosis increased from 39.5% to 63% (Razvi et al., 2009). S. aureus infections are mostly acquired during childhood, initiate changes in the lungs of CF patients that allow P. aeruginosa to finally infect these patients which all add to a worse patient outcome (Sagel et al., 2009; Hauser et al., 2011; Cystic Fibrosis Foundation, 2014). Negative relationship between P. aeruginosa and S. aureus during adolescent years and young adulthood have brought into light several studies with respect to inter- microbial interactions of these two life forms (Ruger et al., 2014; Baldan et al., 2014; Fugere et al., 2014; Park et al., 2012). These pathogens are ordinarily isolated from respiratory cultures of cystic fibrosis and it has been shown that risk factors for introductory P. aeruginosa respiratory infection in patients with cystic fibrosis include pre-colonization of S. aureus (Hoffman et al., 2006; Maselli et al., 2003). Herein we concentrated on inter-specie interactions of two medically important human pathogenic bacteria by utilizing an in-vitro host cell model. Present study is aimed to explore the impact of P. aeruginosa on the growth and virulence of S. aureus and the level of infection’s severity. Our data suggests that S. aureus is negatively impacted by the presence of P. aeruginosa and co-infection by these pathogens make the condition more frightful. MATERIALS AND METHODS Microorganisms and culture growth conditions S. aureus ATCC 25923 and P. aeruginosa ATCC 27853 were obtained from American type culture collection. They were cultured in LB broth and incubated at 37°C. *Corresponding author: e-mail: microphilia@outlook.com