In vitro biofilm formation and antimicrobial susceptibility patterns of bacteria isolated from suspected external ocular infected patients attending Jimma University Medical Center eye clinic, southwest Ethiopia

Background: Ocular disease with its complications is a major public health problem which significantly impacts on quality of life in developing countries. An ocular infection due to microbial agents, can lead to reduced vision and blindness. This study was aimed to assess the antimicrobial susceptibility pattern and biofilm forming potential of bacteria isolated from suspected external ocular infected patients attending Jimma University Medical Center (JUMC). Method: A cross sectional facility based study was conducted on 319 suspect patients with external ocular infections from March 2017 to June 2017 at JUMC in Southwest Ethiopia. External ocular specimens were collected and standard operating procedures were followed to handle and culture throughout the study period. Antimicrobial susceptibility pattern of the isolates was determined by disk diffusion method according to CLSI 2015. Microtiter (96 wells) plate method was used to screen biofilm formation by measuring optical density at 570nm. Result: Out of 319 study participants with external ocular infection, the prevalence of bacterial pathogens was 46.1%. The predominant bacterial isolates were Coagulase negative staphylococcus (CoNS) (27.7%) followed by Staphylococcus aureus (19.7%). Among Gram negatives, Pseudomonas aeroginosa (6.8%) was the leading isolate. Increased antimicrobial resistance was observed for tetracycline (64%), erthromycin (66.7%) and penicillin (77.1%). Amoxicillin-clavulanic acid, ciprofloxacin and gentamicin were the most effective drugs for both Gram negative and Gram positive ranging from about 70 to 100% with the later two drugs for external ocular infections. Methicillin resistant S. aureus (MRSA) accounted for 13.8% of S. aureus isolates.. Multidrug resistance (MDR) accounted for 68.7%. The overall biofilm formation rate of bacterial ocular pathogens was 66.1%; with P. aeruginosa (40%), CoNS (34.1%) and S. aureus (31%) formed strong biofilm phenotype. Conclusion: The prevalence of bacterial isolates among external ocular infection was high. Almost all bacterial isolates were resistant to atleast one or more drugs. MDR pathogens were observed increasingly among biofilm formers or vice versa. Therefore, antimicrobial susceptibility testing should be practiced to guide treatment of external ocular cases and to control the emergence of drug resistant bacteria.