Free living amoeba (FLA) such as Acanthamoeba spp. are ubiquitous protozoa that have been isolated in virtually all environments in nature and in anthropogenic milieu globally (Saeed et al., 2012; Chow and Glaser, 2014; Lakhundi, Siddiqui and Khan, 2015; Fabres et al., 2016; Rubenina et al., 2017). FLA phagocytose microorganisms from the environment such as bacteria, algae, fungi, protozoa and particles rich in energy for nutrition (Gimenez et al., 2011; Aç et al., 2013; Ovrutsky et al., 2013; Cervero-Aragó et al., 2015; Fabres et al., 2016).
However, some amoeba resistant microorganisms (ARMs) resist amoebic killing and proliferate within FLA following phagocytosis. These ARMs are released into the environment as free pathogens or in vesicles (Greub and Raoult, 2004; Barnard, 2015). Common human pathogenic ARMs include bacteria of the families Pseudomonaceae, Enterobacteriaceae, Mycobacteraceae and Vibrionaceae, and viruses (Greub and Raoult, 2004; Aç et al., 2013; Ovrutsky et al., 2013; Guimaraes et al., 2016).
FLA hosting ARMs act as concealed niches of microorganisms that propagate continuous circulation of pathogens and drug resistant genes across hosts and the environment (da Rocha-Azevedo, Tanowitz and Marciano-Cabral, 2009; Lamrabet et al., 2012; Altayyar et al., 2016; Fabres et al., 2016). Other effects of FLA- ARMs interactions include ARMs enhanced pathogenicity and virulence, ARMs training against macrophages, protection against harsh conditions and contribution to nosocomial infections burden despite stringent infection control measures (Horn, 2001; Khan and Siddiqui, 2014; Fabres et al., 2016; Balczun and Scheid, 2017; Rubenina et al., 2017).
The most common FLA linked to human disease is Acanthamoeba spp. (Guimaraes et al., 2016; Balczun and Scheid, 2017). It has been isolated from water, soil, dust, hospital environment and equipment such as dental units, used contact lenses, ventilators, dialysis units and ocular wash stations (Moon et al. 2008; Marciano-Cabral & Cabral 2003;Jeong & Yu 2005; Lass et al. 2014; Teixeira et al. 2009). Isolates of Acanthamoeba spp. have also been obtained from infected human specimens such as the lungs, brain tissues, corneal biopsies, cerebral spinal fluid and genitourinary tracts (Szénási et al., 1998; Jeong and Yu, 2005; Dendana et al., 2008; Siddiqui and Khan, 2012).
Acanthamoeba sp. exists as trophozoites and cysts with the former being the pathogenic stage which is metabolically active and motile. The cyst is the dormant stage and it is formed at the end of growth cycle or in harsh environmental conditions. Cysts survive desiccation, temperature changes, disinfectants, biocides, radiation, chlorination, pH changes, antibiotics, osmotic pressure variations and reduced nutrients (Marciano-Cabral and Cabral, 2003a; Siripanth and Med, 2005; da Rocha-Azevedo, Tanowitz and Marciano-Cabral, 2009; Teixeira et al., 2009; Booton et al., 2010; Bertelli and Greub, 2012; Clarke et al., 2012; Cervero-Aragó et al., 2015; Chomicz et al., 2015; Hsueh and Gibson, 2015). They also act as reservoirs and sources of infections due to their ability to survive for several years in the environment (Marciano-Cabral and Cabral, 2003b; Essa et al., 2016). Both trophozoites and cysts have been isolated from the environment as well as from infected human tissues (Khan, 2003; da Rocha-Azevedo, Tanowitz and Marciano-Cabral, 2009).
Acanthamoeba spp. existence in hospital environment pose an explicit risk of expedient infections to the immunocompromised patients such as granulomatous amoebic encephalitis (GAE), sinusitis and skin lesions (Barnard, 2015; Shokri et al., 2016; Taravaud, Loiseau and Pomel, 2017; Souza, 2018). Amoebic keratitis is manifested among the immunocompetent individuals commonly in the contact lens users, patients with corneal injury and those living in places with inadequate water supply (Chappell et al., 2001; Khan, 2003; Booton et al., 2010; Clarke et al., 2012; Muchesa et al., 2014). Besides, Acanthamoeba spp. have been associated with more than 100 species of pathogenic bacteria which may be transmitted to humans and higher animals (Douesnard-Malo and Daigle, 2011; Gryseels et al., 2012; Aç et al., 2013; Fabres et al., 2016). Pseudomonas sp., a known ARM with high antibiotic and disinfectants resistance, increased virulence is also an etiologic agent of nosocomial infections (Lim and Webb, 2005).
The ubiquity of Pseudomonas sp. allows for its vast spread to patients from diverse sources including air, food, water, visitors, linen, contaminated medical personnel, contaminated surfaces and equipment such as catheters and ventilators which readily predisposes patients to nosocomial infections (Davane et al., 2014). Pseudomonas has been isolated from bacterial cultures as an etiologic agent of primary infections and/ or nosocomial infections from patients at Kenyatta National Hospital Intensive Care Unit (KNH ICU) (Njoki, 2009).
Nonetheless, since most infections are linked to well-known free pathogens, the role of FLA such as Acanthamoeba spp. and ARMs such as Pseudomonas spp. in disease burden is mostly overlooked (Khan and Siddiqui, 2014). This could be one of the reasons for the escalated rates of nosocomial infections despite stringent infection control measures (Altayyar et al., 2016). This is further complicated by the lack of information on FLA, ARMs and the possible effects of their interactions and the lack of awareness among healthcare personnel in Kenya. The study therefore sought to assess the prevalence of Acanthamoeba sp. and associated Pseudomonas sp. from selected surfaces and equipment in ICU at Kenyatta National Hospital (KNH), the largest teaching and referral hospital in East and Central Africa located in Nairobi, the capital city of Kenya, in order to inform infection control policy.