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Novel and nasty Corynebacterium
Our Discovery
• A novel Corynebacterium sp.
• Associated with clinical disease and mortality in NSG and NOD SCID mice
• Highly contagious
IDEXX BioAnalytics
IDEXX BioAnalytics
A Newly Recognized Pathogen of Immunocompromised Mice
A novel Corynebacterium sp. distinct from C. bovis causes dermatitis and death in immunocompromised mice.
• Infected NOG and NSG mice develop thick skin with hyperkeratosis• Infected nude mice have slightly thick skin without scales• Testing for the bacterial disease can be accomplished by culture and PCR
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Clinical Syndrome in Infected Mice
NSG and NOG mice were used for xenograft passage
• Severely immunocompromised mice that lack functional T, B and NK lymphocytes• Noticed rough hair coats and dehydration• Colony tested negative for Corynebacterium bovis and other murine pathogens
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Diagnostic Findings
• Skin thickened & inflamed• Abundant keratin scales with bacterial colonization• Corynebacterium bovis negative (PCR & culture)
Keratin heavily colonized by Gram-positive bacterial rods
KERATIN SCALES
GRAM STAINED TISSUE
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BioAnalytics
Diagnostic Test Development
• Cultured a coryneform bacteria - Not C. bovis or mastiditis
• Confirmed as Corynebacterium by sequence analysis - 16S rRNA and rpoB genes sequenced
• Developed a specific PCR test
• Added unique spectra to the MALDI-TOF database
Detected Species Log(Score)
Corynebacterium sp. IBRM 27989.16.3C 2.206
Corynebacterium sp. 2.140
Lactobacillus reuteri DSM 20015 DSM 1.277
Rhizobium radiobacter B177 UFL 1.248
Lactobacillus aviarius spp aviarius DSM 20654 DSM 1.229
Bacteroides fraqilis MB 9009 05 THL 1.224
Corynebacterium mastitidis DSM 44354 DSM 1.190
Mix
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Infection Study Design
Sham GroupICR, nude & NOG mice: 50uL sterile PBS topically
Corynebacterium sp. Group
ICR, nude & NOG mice: typically 4x106 Corynebacterium sp. • Inoculated 50uL on dorsal cervical area • Dripped or swabbed on skin
Culture, PCR and tissue samples were taken at 4 and 6 weeks post-inoculation; halted study at 6 weeks due to declining health of mice
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Clinical Disease Reproduceability
NOG
Rough hair coats
Abundant scales
Dehydration
Thickened skin
Gram-positive rod-shaped
bacteria in lesions
ICR
Smooth hair coats
Normal hydration
No bacteria on skin
Nude
Minimal scales
Skin erythema
No dehydration
Thickened skin
Gram-positive rod-shaped
bacteria in lesions
SHAM CONTROL - NUDE INOCULATED - NUDE
Culture and PCR Summary
Corynebacterium sp TestingGroup Strain PI PeltPCR PeltCulture FecesPCR
Sham NOG 4wk 2/2- 2/2- 2/2-
Sham Nude 4wk 3/3- 3/3- 3/3-
Sham ICR 4wk 2/2- 2/2- 2/2-
Corynesp NOG 4wk 4/4+ 4/4+ 4/4+
Corynesp Nude 4wk 4/4+ 4/4+ 4/4+
Corynesp ICR 4wk 4/4- 4/4- 4/4-
Corynebacterium sp TestingGroup Strain PI PeltPCR PeltCulture FecesPCR
Sham NOG 6wk 2/2- 2/2- 2/2-
Sham Nude 6wk 3/3- 3/3- 3/3-
Sham ICR 6wk 2/2- 2/2- 2/2-
Coryne sp NOG 6wk 4/4+ 4/4+ 4/4+
Corynesp Nude 6wk 4/4+ 4/4+ 4/4+
Corynesp ICR 6wk 4/4- 4/4- 4/4-
• All inoculated nude and NOG mice became colonized
- Pelt swabs were positive by culture and PCR - Feces were positive by PCR
• Inoculated ICR mice resisted colonization• Sham-inoculated mice remained bacteria free
Corynebacterium sp. Testing
Corynebacterium sp. Testing
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Infection Studies to Reproduce Disease
ICR outbred mice
• Immunocompetent • Supports transient infection with C. bovis
Nude (Foxn1nu) mice
• Lack T lymphocytes • Develops disease from C. bovis
NOG (NOD.Cg-Prkdcscid Il2rgtm1Sug/JicTac)
• Lack T, B, NK lymphocytes; defective dendritic cell function • Develops disease from C. bovis
Study included three genotypes of female mice, 4-5 wks old
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Corynebacterium sp. Testing RecommendationsInclude Corynebacterium sp. when testing for C. bovis
Quarantine and Health Monitoring Programs • Test immunocompromised mouse colonies - Skin, fur or swab - Culture or PCR • Screen environmental samples by PCR
Diagnostic Investigations of sick Immunocompromised Animals
Bioligical Materials Screening by PCR - Implantable trumors - Cell lines
BioAnalytics© 2018 IDEXX Laboratories, Inc. All rights reserved. IBA-RE14 Coryne Presentation
Corynebacterium sp. Testing Recommendations
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BioAnalytics© 2018 IDEXX Laboratories, Inc. All rights reserved. IBA-RE14 Coryne Presentation