Microbe

"Microbe" - what is it, definition of the term

A microbe is a microscopic living entity encompassing bacteria, archaea, viruses, fungi, and protists; it cannot be resolved without magnification and may exist independently or within host organisms. In rodent species such as rats and mice, these organisms can function as commensals, opportunistic pathogens, or vectors of disease, influencing host physiology and epidemiology through metabolic interactions, immune modulation, and transmission cycles.

Detailed information

Microorganisms inhabiting rodents constitute a diverse community that includes bacteria, viruses, fungi, and protozoa. In laboratory and wild populations, these agents affect health, experimental outcomes, and zoonotic risk.

Bacterial species commonly isolated from rats and mice encompass:

• Salmonella spp., causing enteric disease and serving as a model for gastrointestinal infection studies.
• Helicobacter spp., especially H. hepaticus and H. bilis, which colonize the liver and intestine and can trigger inflammatory lesions.
• Streptococcus spp., including S. pneumoniae, responsible for respiratory infections.
• Clostridium spp., producing toxins that lead to colitis in susceptible strains.

Viral agents frequently encountered include:

• Lymphocytic choriomeningitis virus (LCMV), transmitted vertically and horizontally, capable of persistent infection and neuroinvasion.
• Rat coronavirus (RCV) and mouse hepatitis virus (MHV), both causing enteric and respiratory pathology.
• Hantaviruses, harbored by wild rodents, capable of spillover to humans and resulting in hemorrhagic fever with renal syndrome.

Fungal contaminants such as Candida spp. and Aspergillus spp. may colonize mucosal surfaces, especially in immunocompromised animals, leading to opportunistic infections. Protozoan parasites, including Giardia and Entamoeba species, are detected in fecal samples and can induce diarrheal disease.

The resident microbiota of the gastrointestinal tract shapes immune development, metabolic function, and drug metabolism. Dominant bacterial phyla include Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Dysbiosis, defined by shifts in relative abundance, correlates with obesity, inflammatory bowel disease models, and susceptibility to infectious agents.

Transmission routes comprise direct contact, aerosolized particles, contaminated bedding, feed, and water. Strict barrier practices—sterile housing, filtered air, autoclaved supplies—reduce inadvertent exposure. Routine surveillance programs employ culture, PCR, serology, and next‑generation sequencing to detect pathogens at subclinical levels.

In experimental contexts, specific microorganisms serve as disease models. Salmonella infection mimics human typhoid fever; LCMV infection illustrates chronic viral persistence; Helicobacter infection reproduces colitis. Researchers manipulate germ‑free or gnotobiotic rodents to assess microbiome contributions to phenotype.

Control measures include:

1. Routine health monitoring with defined pathogen panels.
2. Quarantine of new arrivals and thorough decontamination of transport containers.
3. Use of individually ventilated cages to limit aerosol spread.
4. Implementation of antimicrobial regimens only when justified by diagnostic results.

Understanding the spectrum of microscopic organisms associated with rats and mice is essential for maintaining colony health, ensuring experimental validity, and preventing zoonotic transmission.