# Isolation, Identification, and Antimicrobial Susceptibility of Exiguobacterium mexicanum from a Giraffe

## TL;DR

Scientists isolated a new strain of Exiguobacterium mexicanum from a dead giraffe and tested its response to various antibiotics.

## Contribution

First report of E. mexicanum isolated from a giraffe, with detailed antimicrobial susceptibility data for this species in this host.

## Key findings

- HN-1 strain of E. mexicanum was isolated from multiple organs of a deceased giraffe.
- The strain showed susceptibility to several antibiotics but resistance to oxacillin, penicillin, ciprofloxacin, and linezolid.

## Abstract

Exiguobacterium mexicanum (E. mexicanum) is a facultative anaerobic, Gram-positive bacterium within the genus Exiguobacterium. Although it is commonly found in diverse environments—including soil, water, and extreme habitats such as hot springs and permafrost—this species is rarely linked to infections in humans or animals. This study reports the isolation and characterization of a potentially pathogenic strain of E. mexicanum from a giraffe, along with its antimicrobial susceptibility profile, to inform clinical treatment strategies. The pathogenicity of Exiguobacterium species in wildlife remains poorly understood, with very few documented infections and limited data on host range, virulence factors, and resistance patterns. This gap underscores the significance of the current isolate, suggesting that E. mexicanum may represent an emerging pathogen in giraffes. Notably, despite the well-documented threats to giraffe populations, there have been no previous reports of E. mexicanum infection in this species, highlighting the novelty of our findings and emphasizing the need for further research into its potential role as a pathogen.

In May 2025, a female giraffe in poor body condition died unexpectedly at a zoo in Henan Province, China. A bacterial strain, designated HN-1, was isolated from the heart, liver, spleen, lungs, and kidneys of the deceased animal. After 24 h of incubation at 37 °C on Luria–Bertani (LB) agar, the colonies appeared round, smooth, pale yellow, translucent, and raised. Gram staining revealed that the isolate was a Gram-positive, rod-shaped, and non-spore-forming bacterium. Based on 16S rRNA gene sequencing, the strain showed more than 99.7% homology with reference sequences of E. mexicanum from various sources in GenBank. The results of the susceptibility test showed that E. mexicanum was susceptible to levofloxacin, clindamycin, chloramphenicol, trimethoprim, rifampicin, tetracycline, minocycline, gentamicin, erythromycin, and doxycycline, but resistant to oxacillin, penicillin, ciprofloxacin, and linezolid. These findings provide valuable insights for the diagnosis and treatment of infections caused by E. mexicanum in giraffes.