Naturally occurring dermatitis associated with Staphylococcus aureus in DS-Nh mice

Area of Science:

• Veterinary Dermatology
• Microbiology
• Animal Pathology

Background:

• A naturally occurring dermatitis epizootic affected all mice (DS-Nh strain) housed under conventional conditions.
• The dermatitis primarily impacted the face, neck, and shoulders, irrespective of mouse age or sex.

Purpose of the Study:

• To identify the causative agent of the observed dermatitis epizootic in DS-Nh mice.
• To characterize the clinical and histopathological features of the disease.
• To confirm the etiological role of the isolated bacteria through experimental induction.

Main Methods:

• Clinical observation of affected mice.
• Histopathological examination of skin lesions, including inflammatory cell infiltration, parakeratosis, and amyloidosis.
• Bacteriological culture and isolation of causative agents from skin lesions.
• Experimental inoculation of isolated bacteria into healthy mice to reproduce the disease.

Main Results:

• Affected mice exhibited chronic dermatitis with characteristic histopathological findings.
• Gram-positive cocci clusters were consistently found in lesioned tissues.
• Coagulase-positive Staphylococcus aureus (S. aureus) was isolated in pure culture from all affected mice.
• Experimental induction with S. aureus isolates resulted in disease indistinguishable from natural cases.

Conclusions:

• Staphylococcus aureus is strongly implicated as the causative agent of the observed dermatitis epizootic in DS-Nh mice.
• The study highlights S. aureus as a potential cause of contagious dermatitis in laboratory mouse colonies.
• This finding is crucial for maintaining the health and integrity of research animal populations.