Shewanella putrefaciens from Clinical Specimens and Environmental Samples. Biofilm Formation & Eradication

Aims: To investigate occurrence of Shewanella putrefaciens in clinical and environmental sources, to determine antimicrobial susceptibility profiles of isolates and to determine the efficacy of minimum inhibitory concentration (MIC) and lesser concentrations of the most effective antibiotic and the most commonly used biocides in Iraqi hospitals: Povidone–iodine and Sapton, to inhibit or eradicate biofilms produced by recovering isolates.
Methodology: Three hundred and twenty samples collected from clinical specimens (n=173) and environmental sources (n=320) at Thi Qar General Hospital / Iraq were processed by standard tech-niques to isolate and identify S. putrefaciens. Antimicrobial sensitivity toward eight antibiotics was de¬termined. Adhesion and biofilm formation assays were performed by recovered strains grown artificially in 96-well microtiter plates and measured spectrophotometrically. Minimum inhibition concentration and lesser concentrations of ciprofloxacin and the biocides: Povidone – iodine and Sapton for inhibition or eradication of biofilm were investigated.
Results: Eleven S. putrefaciens isolates (3.4%) were identified from clinical (5 isolates, 2.9%) and environmental (6 isolates, 4%) sources. Multiresistant isolates were evident, though ciprofloxacin was the only antibiotic effective against all isolates. Ear isolate demonstrated the highest degree of attachment followed by that of sewage isolate. Bacterial ability to produce biofilm was reduced up to 42.7%, 56.9% and 64.4% of the total biomass when exposed to 1/4MIC, 1/2MIC and MIC respectively. Biofilm formation was reduced up to 65.8 % and 48.7% of total biomass by exposing to Povidone-Iodine and Sapton respectively.
Conclusion: The penetration ability and the removal and killing efficacies of ciprofloxacin and the two biocides against biofilms formed in microtiter plates by S. putrefaciens although evident, but none of the above antimicrobial agents led to the total biofilm removal and/or killing. Hence, multidrug resistant S. putrefaciens have a tremendous challenge accompanied with the formation and persistence of bacterial biofilms particularly when adhere to medical devices or damaged tissue can become the cause of persistent infections.