Prevalence, Distribution, and Antimicrobial Susceptibility of Enterobacteriaceae and Non-Fermenting Gram-Negative Bacilli Isolated from Environmental Samples in a Veterinary Clinical Hospital in Madrid, Spain.

Abstract

Managing infections caused by multidrug-resistant Gram-negative bacilli is a major public health concern, particularly in hos-pitals where surfaces can act as reservoirs for resistant microorganisms. Identifying these bacteria in hospital environmentsis crucial for improving healthcare safety. This study aimed to analyse environmental samples from a veterinary hospital toidentify prevalent microorganisms and detect antimicrobial resistance patterns. A total of 183 surface samples were collectedfrom 26 areas at the Veterinary Clinical Hospital of Alfonso X el Sabio University in Madrid. The isolated strains were identified,and susceptibility profiles were determined via the disk diffusion method. Clonality analysis was performed using pulsed-fieldgel electrophoresis. In total, 109 strains were isolated: 76.15% from the Enterobacteriaceae family and 23.85% non-fermentingGram-negative bacilli. The isolates included Klebsiella, Enterobacter, Escherichia and Pseudomonas species, which could includehigh-risk clones, given their ability to carry several antimicrobial resistance genes. The equine area had the highest number ofisolates (n = 71), accounting for 65% of the total. High resistance indices were observed against at least five of the 16 antibioticstested, indicating significant multidrug resistance. Clonality analysis suggested potential cross-transmission within the facility.This study sampled hospital surfaces but not personnel or animals, making contamination sources unclear. Without resampling,the effectiveness of cleaning protocols remains uncertain. Results suggest that hospital staff play a key role in bacterial transmis-sion. The lack of specialised preventive measures in veterinary hospitals highlights a need for further research and improvement.