Antagonistic Activity of Lactobacillus acidophilus Against Acinetobacter baumannii Isolated from Feline Conjunctivitis in vitro, in Baghdad, Iraq

Abstract

Background: Acinetobacter baumannii is an opportunistic pathogen associated with nosocomial infections; it can cause ocular infections in animals and humans. In veterinary medicine, this bacterium has been increasingly reported in a variety of animal species, including companion animals, where it may lead to respiratory, conjunctivitis, urinary, and wound infections. In cats, A. baumannii has been implicated in conjunctivitis, often presenting with ocular discharge, redness, and discomfort. The growing concern lies in its ability to develop multidrug resistance, which limits therapeutic options. This situation underscores the need to investigate alternative antimicrobial strategies, such as the use of probiotic bacteria with potential inhibitory effects. Aims: This study aimed to isolate and identify Acinetobacter baumannii from feline conjunctivitis cases in Baghdad, Iraq, and to evaluate the antagonistic activity of Lactobacillus acidophilus against it in vitro Results: Out of 100 conjunctival swabs collected from cats between November 2024 and March 2025, Acinetobacter baumannii was isolated from 5 samples (5%). All isolates were oxidase-negative and catalase-positive, and identification was confirmed by the VITEK 2 system. Lactobacillus acidophilus obtained from commercial powder was successfully cultured and identified using the API 50 CHL system. Agar well diffusion assays revealed clear inhibition zones around the wells containing L. acidophilus, indicating a significant antagonistic effect against A. baumannii

Conclusions: This study successfully achieved its primary objective of isolating Acinetobacter baumannii from cases of feline conjunctivitis. The findings further highlight the potential application of Lactobacillus acidophilus as a probiotic agent against multidrug-resistant A. baumannii.