Pantoea agglomerans in Equine Ulcerative Keratitis - Prevalence and Comparative Efficacy of Four Topical Antiseptics

Sep 29, 2026

Uploaded by Jasmine

Objective: determine the minimal bactericidal concentration (MBC) and effective contact time of polyhexanide, povidone-iodine (PVP-I), hypochlorous acid (HOCl), and N-acetylcysteine (NAC) against Pantoea agglomerans, a pathogen repeatedly isolated in equine ulcerative keratitis. Isolates were collected from horses over 17 months; the most frequent strain was assessed in vitro. Each antiseptic was tested in triplicate and evaluated at defined exposure times (15 s to 5 min). Results identified rapid bactericidal action for polyhexanide, PVP-I, and HOCl, whereas NAC required higher concentrations and longer exposure. Conclusions support these agents, especially faster-acting options, as antibiotic alternatives within a One Health framework.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages10

Reading Time25 min

AccessFree to download

Abstract

Introduction

Background on equine ulcerative keratitis and bacterial genera

Rationale for alternative antiseptics to antibiotics

Materials and Methods

Study isolates and sampling design

In vitro determination of MBC and contact time

Veterinary Ophthalmology ORIGINAL REPORT OPEN ACCESS Pantoea agglomerans in Equine Ulcerative Keratitis: Prevalence and Comparative Efficacy of Four Topical Antiseptics Frederik Heun1 | Jessica Meißner2 | Ann-Kathrin Schieder3 | Bernhard Ohnesorge1 | Claudia Busse4 1Clinic for Horses, University of Veterinary Medicine Hannover, Hannover, Germany | 2Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany | 3LABOKLIN GmbH & co. KG, Bad Kissingen, Germany | 4Clinic for Small Animals, Department of Ophthalmology, University of Veterinary Medicine Hannover, Hannover, Germany Correspondence: Frederik Heun (frederik.heun@tiho-hannover.de) Received: 24 November 2024 | Revised: 8 May 2025 | Accepted: 12 June 2025 Keywords: eye | horse | hypochlorous acid | N-acetylcysteine | polyhexanide | PVP-iodine ABSTRACT Objective: To determine the minimal bactericidal concentration (MBC) and effective contact time of four topical antiseptics—polyhexanide, povidone-iodine (PVP-I), hypochlorous acid (HOCl), and N-acetylcysteine (NAC)—against Pantoea agglomerans, a pathogen frequently isolated in equine ulcerative keratitis. Animals Studied: Over a 17-month sampling period, clinical isolates were collected from horses with ulcerative keratitis. The most frequently isolated strain (Pantoea agglomerans, n = 14) was selected for in vitro analysis. Procedure(s): All isolates were used to determine the MBCs of the four antiseptics. Each was tested in triplicate at serial dilutions per isolate. Additionally, the requisite contact time for a bactericidal effect was evaluated at a supratherapeutic dilution for each substance with each isolate at defined time points ranging from 15 s to 5 min. Results: The MBCs of polyhexanide, PVP-I, HOCL, and NAC were 3.2ppm (0.00032%), 16 ppm (0.0016%), 0.8 ppm (0.00008%), and 3200 ppm (0.32%), respectively. Polyhexanide (6.4 ppm), PVP-I (64 ppm), and HOCL (6.4ppm) were effective within 15 s. NAC (6400 ppm) required 1–2 min to achieve bactericidal effects. Conclusions: All antiseptics tested demonstrated efficacy against P. agglomerans. Polyhexanide, PVP-I, and HOCl achieved rapid bactericidal activity, while NAC required higher concentrations and longer exposure. These results support the use of these agents—particularly the faster-acting three—as potential alternatives to antibiotics in treating equine ulcerative keratitis. They may aid the reduction of antibiotic use in line with the One Health approach. 1 | Introduction Ulcerative keratitis in horses is frequently associated with local bacterial infection [1, 2] . Studies of equine ulcerative keratitis in recent decades, for example, in Belgium [1], the United States (US) [3, 4], and Japan [5], have shown that Staphylococcus spp., Streptococcus spp. , and Pseudomonas spp. are the primary genera involved. Most publications suggest that the microflora of healthy equine eyes is dominated by Gram-positive bacteria [6–8] . However, a recent study from the United States using culture-independent, DNA-based detection methods showed that Gram-negative bacteria are more common on the ocular surface [9] . Pantoea agglomerans is a Gram-negative bacterium from the family Erwiniaceae. It is infrequently isolated from both healthy equine eyes and those with bacterial corneal ulceration [1–3, 6, 10] . A recent study | Bernhard Ohnesorge and Claudia Busse have contributed equally to this work. | | --- | | This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
© 2025 The Author(s). Veterinary Ophthalmology published by Wiley Periodicals LLC on behalf of American College of Veterinary Ophthalmologists. | Veterinary Ophthalmology, 2026; 29:e70044 1 of 10 [https://doi.org/10.1111/vop.70044](https://doi.org/10.1111/vop.70044) from Germany,

FAQs

What was the study’s primary objective?

To determine the minimal bactericidal concentration (MBC) and effective contact time of four topical antiseptics against Pantoea agglomerans.

How were the bacterial isolates selected and analyzed?

Clinical isolates were collected from horses with ulcerative keratitis over 17 months, and the most frequently isolated strain was used for in vitro testing.

Which antiseptics showed rapid bactericidal effects?

Polyhexanide, PVP-I, and HOCl achieved effective bactericidal action within about 15 seconds, based on the reported MBC and time-point results.

Sep 29, 2026

Uploaded by Jasmine