Microorganisms are ubiquitous in our environment, including indoor air, and do not necessarily constitute a health hazard. Depending on the individual, the concentration at which contamination becomes a threat to health is unknown
. Inanimate surfaces and noncritical equipment have often been described as the source for outbreaks of nosocomial infections
[27–29]. The aim of this work was to evaluate, in a Portuguese hospital facility, the number and diversity of microorganisms that persist on inanimate surfaces and noncritical equipment, able to grow on the selective media for P. aeruginosa and relate them with the presence of the opportunistic pathogen P. aeruginosa.
Data is available on the microbial composition of dust from different environments, showing Gram-positive as dominants, with the most abundant phylum being Firmicutes
. However, other studies on the microbial diversity of the environmental surfaces are mainly evaluating the bacterial counts on cloths and other equipment from medical personnel
In the present study, PIA medium was used to recover microorganisms from noncritical equipment and from surfaces, dry or wet. PIA is an isolation medium selective and differential for P. aeruginosa, since this species has innate resistance to low Irgasan concentrations
. Nevertheless, 10 different bacterial genera of Gram negative and Gram positive bacteria were isolated in the medium which seems to indicate that these organisms are resistant to the biocide and could possibly have multidrug efflux systems to extrude the antimicrobial Triclosan (Irgasan) as it occurs in P. aeruginosa. This conclusion is supported by the detection of clonal isolates from different sampling times. The presence of this toxic in many household antibacterial products and antiseptics can probably select for microorganisms able to resist to low concentrations of this biocide
. Many Gram-negative species were isolated, which is according to previous reports showing that strains from Acinetobacter spp., Klebsiella spp., Shigella spp., E. coli, P. aeruginosa, or S. marcescens are able to survive for months on surfaces
. These species are among the most frequent isolates from patients with nosocomially acquired infections
. Moreover, all isolates from this work are resistant to the disinfectant Triclosan, on the other hand, not all the microorganisms present in the environment were isolated.
P. aeruginosa is described to persist from 6 hours to 16 months on surfaces and its persistence was related with humidity conditions
[32, 33]. P. aeruginosa was also found in the present work, as part of the microbial community of surfaces with high moister and also in the biofilm of taps. Even though, ubiquitous in the environment, the prevalence of this species in the community is less than in the hospital, and cases of severe community-acquired infection are rare
. Pseudomonas have been implicated in different clinical syndromes and diseases transmitted mostly directly by aerosols or indirectly by moist environmental surfaces via hands of health-care workers
[12, 35]. In the present work, biofilm tap water was the major environmental source of pseudomonads in the healthcare facility. This conclusion is in agreement with previous findings where biofilms, sink and patient room design were involved in the propagation of a P. aeruginosa outbreak
. Moreover, humidity (wet materials) improved the presence of high numbers of different bacteria species which are clinically important opportunistic organisms as other Pseudomonas as P. mosselii, P. putida, P. alcaligenes, Citrobacter braakii, C. freundii, E. faecalis, S. maltophilia, N. subflava, as found before
In the hospital studied S. maltophilia was isolated nine times in the sinks and in the biofilm of the taps, E. faecalis and S. nematodiphila were repeatedly isolated, two times each, in tap water biofilms, and S. marcescens and Enterobacter spp. were also isolated during the present study. The described genera were reported to be responsible for healthcare–associated episodes of colonization, including respiratory and urinary tracks, bloodstream infections and pneumonia
[5, 12, 38]. E. faecalis, S. nematodiphila, S. marcescens and Enterobacter spp. are commonly associated with transmission by hand carriage and hand transfer
The different type of materials tested did not reveal a consistent (high or low) contamination level. Some investigators reported that the type of material has no influence on the persistence of bacteria, other described a longer bacterial persistence on plastic, others on steel, or a shorter survival on copper
[2, 3, 32, 40]. The statistical analysis of the results based on the contamination level, number of times contaminated and type of material, grouped samples on the base of the group of persons that manipulated the equipment, on the presence or absence of humidity and contact with tap water, but not based on their type of material. This study used a selective medium with a disinfectant to evaluate the microbial colonization of the surfaces and noncritical equipment, revealing the prevalence of a diverse group of microbial species with mechanisms of resistance to the antiseptic, most of them with potential to be involved in nosocomial infections.