Bacteria
Bacteria are single celled microorganisms, without a nucleus (prokaryotes), that can cause lots of morbidity and mortality. They are not infrequently seen by pathologists.
Actinobacteria
General
- A very large group of bacteria.
It includes:[1]
- Actinomycetes.
- Corynebacterium.
- Mycobacterium.
- Nocardia.
- Streptomyces.
Actinomycetes
General
- IUD needs to be removed if found on a pap test[2] - see gynecologic cytopathology.
- Gram-positive branching rods.
- Common in the tonsils.
- Part of the large Actinobacteria group.[1]
Notes:
- Mycete = fungus; these organisms have a fungus-like appearance.
Gross
- Yellow granules.[3]
Microscopic
- Branching rods.
- Typically form pink/purple granules ("sulfur granule") that is surrounded by inflammatory cells (lymphocytes or neutrophils).
DDx:
- Nocardia.
Notes:
- Sulfur granule may be seen grossly - yellow.[3]
Images:
Stains
- Gram +ve.
- AFB -ve.
- Nocardia +ve.
- PAS +ve.
- May be confused with a fungus!
Helicobacter pylori
- See Stomach.
Clostridium difficile
- Commonly C. difficile.
General
- Gram positive bacillus.
One virulent strain is:[5][6] BI/NAP1.
- Deletion of tcdC locus.
- Resistant to fluoroquinolones (gatifloxacin and moxifloxacin).
Chlamydia trachomatis
General
- Common.
- May cause lymphogranuloma venereum.
Note:
- Often co-exists with gonorrhea.
Microscopic
- Variable.
Lymphogranuloma venereum:
- See: Cat-scratch disease.
Mycobacterium tuberculosis
General
- Causes tuberculosis, abbreviated TB.
- May mimic a malignancy.
- Strong association with HIV.
Clinical features:
- Cough.
- Fever.
- Weight loss.
Tests:
Treatment:
- Multiple drugs for a long time (months).
- Commonly used drugs: isoniazid, rifampin, pyrazinamide, and ethambutol.
Gross
Ghon complex
Consists of two components:[7][8]
- Peripheral focus - subpleural, calcified.
- Central focus - the hilar lymph node that drains the peripheral focus.
Image:
Microscopic
Features:
- Necrotizing granulomas with rod-shaped bacteria.
Note:
- May be non-necrotizing.
Images:
- Tuberculosis - case 1 - several images (upmc.edu).
- Tuberculosis - case 2 - several images (upmc.edu).
- Tuberculosis - case 3 - several images (upmc.edu).
Stains
- Ziehl-Neelsen stain - red rod-shaped bacteria - key feature.
- Very small - must use 40x objective.
Image:
Molecular
- Can be diagnosed with PCR.
Mycobacterium leprae
General
- Causes leprosy.
Clinical:
- Nerve damage -> injuries -> disability.
Microscopic
Features:
- Granulomas with rod-shaped bacteria.
Stains
- Fite stain - red rod-shaped bacteria - key feature.
- Very small - must use 40x objective.
Image:
Coxiella burnetii
General
- Causes: Q fever.
Features:
- Intracellular bacterium.
- Gram negative.
Clinical:
- Flu-like symptoms.
Microscopic
Features:
- Fibrin ring granuloma.
- Epithelioid macrophages (i.e. a granuloma) surrounding a thin pink (fibrin) ring.
DDx:[10]
- Infections (Coxiella burnetii, CMV, EBV + others).
- Drug reaction.
- Malignancy (e.g. Hodgkin lymphoma[11]).
Images:
Bartonella henselae
General
Causative agent in:
Microscopic
Features - bacillary angiomatosis:
- Similar to pyogenic granuloma - see pyogenic granuloma.
Features - cat-scratch disease:
- Stellate granulomas.
See also
References
- ↑ 1.0 1.1 Ventura, M.; Canchaya, C.; Tauch, A.; Chandra, G.; Fitzgerald, GF.; Chater, KF.; van Sinderen, D. (Sep 2007). "Genomics of Actinobacteria: tracing the evolutionary history of an ancient phylum.". Microbiol Mol Biol Rev 71 (3): 495-548. doi:10.1128/MMBR.00005-07. PMC 2168647. PMID 17804669. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2168647/.
- ↑ Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 446. ISBN 978-0781765275.
- ↑ 3.0 3.1 3.2 URL: http://pathmicro.med.sc.edu/mycology/mycology-2.htm. Accessed on: 14 September 2011.
- ↑ URL: http://pathology.class.kmu.edu.tw/ch05/Slide42.htm . Accessed on: 14 September 2011.
- ↑ URL: http://www.medpagetoday.com/InfectiousDisease/PublicHealth/2254. Accessed on: 15 August 2011.
- ↑ McDonald, LC.; Killgore, GE.; Thompson, A.; Owens, RC.; Kazakova, SV.; Sambol, SP.; Johnson, S.; Gerding, DN. (Dec 2005). "An epidemic, toxin gene-variant strain of Clostridium difficile.". N Engl J Med 353 (23): 2433-41. doi:10.1056/NEJMoa051590. PMID 16322603.
- ↑ Rose, Alan G. (2008). Atlas of Gross Pathology with Histologic Correlation (1st ed.). Cambridge University Press. pp. 112. ISBN 978-0521868792.
- ↑ URL: http://pathhsw5m54.ucsf.edu/case32/image324.html. Accessed on: 27 February 2012.
- ↑ URL: http://www.medscape.com/viewarticle/576467_2. Accessed on: 2 January 2012.
- ↑ Tjwa M, De Hertogh G, Neuville B, Roskams T, Nevens F, Van Steenbergen W (2001). "Hepatic fibrin-ring granulomas in granulomatous hepatitis: report of four cases and review of the literature". Acta Clin Belg 56 (6): 341–8. PMID 11881318.
- ↑ de Bayser L, Roblot P, Ramassamy A, Silvain C, Levillain P, Becq-Giraudon B (July 1993). "Hepatic fibrin-ring granulomas in giant cell arteritis". Gastroenterology 105 (1): 272–3. PMID 8514044.