Pseudomonas putida and Pseudomonas fluorescens Species Group Recovery from Human Homes Varies Seasonally and by Environment

Abstract

By shedding light on variation in time as well as in space, long-term biogeographic studies can help us define organisms’ distribution patterns and understand their underlying drivers. Here we examine distributions of Pseudomonas in and around 15 human homes, focusing on the P. putida and P. fluorescens species groups. We describe recovery from 10,941 samples collected during up to 8 visits per home, occurring on average 2.6 times per year. We collected a mean of 141 samples per visit, from sites in most rooms of the house, from the surrounding yards, and from human and pet occupants. We recovered Pseudomonas in 9.7% of samples, with the majority of isolates being from the P. putida and P. fluorescens species groups (approximately 62% and 23% of Pseudomonas samples recovered respectively). Although representatives of both groups were recovered from every season, every house, and every type of environment sampled, recovery was highly variable across houses and samplings. Whereas recovery of P. putida group was higher in summer and fall than in winter and spring, P. fluorescens group isolates were most often recovered in spring. P. putida group recovery from soils was substantially higher than its recovery from all other environment types, while higher P. fluorescens group recovery from soils than from other sites was much less pronounced. Both species groups were recovered from skin and upper respiratory tract samples from healthy humans and pets, although this occurred infrequently. This study indicates that even species that are able to survive under a broad range of conditions can be rare and variable in their distributions in space and in time. For such groups, determining patterns and causes of stochastic and seasonal variability may be more important for understanding the processes driving their biogeography than the identity of the types of environments in which they can be found.

Metabolic profiles of household Pseudomonas species groups.

“…Several studies have documented the microbial composition of habitats associated with built environments such as: biofilms in domestic drains (McBain et al 2003), human body sites (Costello et al 2009), public restroom surfaces (Flores et al 2011), multiple sites in and around human homes (Ojima et al 2002;Sinclair and Gerba, 2010;Remold et al 2011;Purdy-Gibson et al 2014;Remold et al 2015), indoor and outdoor air (Kembel et al 2012) and on surfaces of fresh fruits and vegetables (Leff and Fierer, 2013). Bacterial species that have been isolated from human homes include Coliforms (Ruslin et al 1998;Ojima et al 2002), E. coli and Staphylococcus aureus (Ojima et al 2002;Medrano-Feliz et al 2010), and P. aeruginosa (Ojima et al 2002;McBain et al 2003;Remold et al 2011;Purdy-Gibson et al 2014).…”

“…The Pseudomonas strains used in these studies were drawn from the larger Pseudomonas study strain collection (Purdy-Gibson et al 2014;Remold et al 2015).…”

“…Strains were isolated between 2007 and 2012. Strains were isolated from several human associated environments such as: soils, household drains, surfaces, water, humans and an animal (one animal isolate) (H&A), kitchen sponges, and trash (Purdy-Gibson et al 2014;Remold et al 2015). The sampling and identification is described in detail in Purdy-Gibson et al, (2014) and Remold et al, (2015).…”

“…Strains were isolated from several human associated environments such as: soils, household drains, surfaces, water, humans and an animal (one animal isolate) (H&A), kitchen sponges, and trash (Purdy-Gibson et al 2014;Remold et al 2015). The sampling and identification is described in detail in Purdy-Gibson et al, (2014) and Remold et al, (2015). Briefly, strains were isolated by swab-sampling areas in the human home, streaking for isolation on Pseudomonas isolation agar (PIA), re-streaking for isolation of a single colony of each distinct colony morphology from each sampled site, and freezing in 12-15% glycerol in LB medium.…”

“…Briefly, strains were isolated by swab-sampling areas in the human home, streaking for isolation on Pseudomonas isolation agar (PIA), re-streaking for isolation of a single colony of each distinct colony morphology from each sampled site, and freezing in 12-15% glycerol in LB medium. Strains were then identified by sequencing at least 500 base pairs of the 16S ribosomal DNA, and comparing this sequence with the Bioinfo 1200 database (Purdy-Gibson et al 2014;Remold et al 2015).…”