Biological features of biofilm-forming ability of Acinetobacter baumannii strains derived from 121 elderly patients with hospital-acquired pneumonia

This study is to investigate a biological activity of Acinetobacter baumannii isolates from sputum specimens of 121 elderly patients with hospital-acquired pneumonia. The ability of the isolates to form biofilms was quantitatively assessed by crystal violet staining, and adhesive property was examined using Giemsa staining. Biofilm-forming ability by the isolates was employed to test antimicrobial resistance and examine sources and clinical manifestations. The isolates grew as biofilm on abiotic surface at the indicated temperatures after a 48 h of incubation. 27.3 % of the isolates were strongly biofilm-positive in the samples, and 84.8 % displayed high adhesion ability (P < 0.05). All of the isolates showed antibiotic resistance at different levels, and the isolates produced strong biofilm exhibited low-level resistance to gentamicin, minocycline and ceftazidime (P < 0.05). The patients' experience in ICU, use of antibiotics and estimation of APACHE II (< 17) were related to incidence of strong biofilm formation with no clinical manifestations found in the study. All clinical isolates are able to form biofilms which refer to adhesive efficiency and antibiotic resistance. Patient experiences in ICU surveillance, use of antibiotics and APACHE II scores are involved in biofilm-forming ability by the nosocomial pathogen derived from the hospitalized patients.