Acinetobacter pittii biofilm formation on inanimate surfaces after long-term desiccation

The survival of pathogenic micro-organisms in the healthcare environment has a major role in nosocomial infections. Among the responsible mechanisms enabling nosocomial pathogens to persist with these stress conditions is their ability to resist desiccation and to form biofilms.

To investigate the survival behaviour of Acinetobacter pittii isolates on inert surfaces and saline microcosms.

Five A. pittii clinical strains were spotted over white laboratory coat fragments, glass, and plastic surfaces, or inoculated into sterile saline and monitored at room temperature for a period of 43 days.

Although the permanence on solid surfaces negatively affected the culturability of the strains used, a fraction of stressed cells survived for at least the period of study. On average, A. pittii culturability was reduced by 77.3%, 80.9%, and 68.1% in white coat, plastic, and glass surfaces, respectively. However, ∼85.6% of the populations retain their culturability in saline solution. Culturability correlated with the presence of cells with an intact membrane, as demonstrated after live/dead staining. Supplementation of the culture medium with sodium pyruvate favoured the culturability of strains from all conditions; but, in general, A. pittii populations did not enter a viable but non-culturable state.

After long-term desiccation, all A. pittii strains retained, or even increased, their ability to form biofilms after they had been fed with nutrient media. This suggests that A. pittii may recover easily from desiccation and may express adherence factors to infect new hosts after rehydration.