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1

Tissue response to fungi (type, cells)

Mixed PMN + lymphocytes + macrophages +/- giant cells

2

Schistosoma genus, and tissue reaction

Schistosoma (genus of trematode) (blood flukes). S. Mansoni & S. Japonicum affect liver (hepatomegaly with portal HTN). S. Hematopium affects bladder (bladder cancer). Eggs induce fibrotic reaction. Chronic inflammation --> heals or resolves to scars.

3

Mechanisms of decreased T cell recognition in DNA viruses and herpes, in order to evade immune response

DNA Viruses (eg. HSV, CMV, EBV - alter localization of MHC-1 protein, impairing CD8 presentation). Herpesviruses can degrade MHC-II - Ag presentation to CD4 Th cells)

4

Furuncle

Skin abscess involving hair follicle and surrounding tissue. Risk: diabetes, obesity, immunocompromise, crowding with poor hygiene. Common on neck, face, buttocks, and armpit. Dx: clinical, swab for culture and sensitivity.

5

Lung Abscess

Localized area of SUPPURATIVE necrosis (neutrophils, necrotic debris). Risk: aspiration of gastric contents, bronchial obstruction, septic emboli, complication of bac. pneum, dental extraction.
Clinical: cough productive of foul-smelling, purulent sputum, FEVER, and finger clubbing, weight loss.

6

TSS

Intravag tampon, & others (skin wound, surgery, abortion). Longer leave in --> S. aureus growth --> release of exotoxin (superantigen) --> polyclonal T cell activation --> T cells release cytokines --> Diffuse rash, vasodilation, hypotension, death. Rash sunburn like, esp palms and soles.
Dx. Blood culture, cervical swabs.

7

Strep Pneumoniae aka Pneumococcal pneumoniae

LOBAR PNEUMONIA. Gram +v, lancet shaped diplococci. *IgA proteases. Most common cause of community acq pneumonia. Healthy adults
RIsk: DM, CHF, COPD, Absent spleen*
Clinical: fever, productive cough, chest pain, bloody sputum, consolidation, bronchial breath, late insp cackles.
Inv: CXR (gold std), blood/sputum culture.
Bronchioles and alv walls NOT DMGD. SPread via PORES OF KOHN.
I. Congestion II. Red hepatization.
III. Gray hepatization IV. resolutoin.
Complications (rare) --> lung abscesses, fibrosis (org), empyema.

8

LOBAR PNEUMONIA

Most common cause - Strep Pneumoniae
Also klebsiella and legionella
I. Congestion: exudate rich in fibrin, RBC, some PMN
II. Red hepatization: exudate RBC, fibrin, PMN. Lung consolidates
III. Gray hepatization: congestion disappears, PMN replaced by macrophages, WBCs
IV. Resolution - Macrophages clear debris.

Lobar pneumoinaL LOCALIZED to particular lobe, UNILATERAL
SEPTUM and ALVEOLAR walls are INTACT
Spreads through pores of kohn.

9

Bronchopneumonia

Patchy, Bilateral (usually). Begins ACUTE bronchitis, spreads locally. DESTRUCTION of bronchioles and alveoli. Coon in young, edlerly, bedridden.
Cause: Haem. influena, klebsiella (alcoholics), pseudomonas (CF), staph (post viral URTI), streptococci.
May lead to abscess formation, empyema, bacteremic dissemination.

10

Rheumatic fever

Infection with Group A, B heaeymolitic streptococci.
Type II HS reaction. Lag period 2-3 weeks post infectino - strep pharyngitis. Antibodies to M protein of bacteria cross react with tissue glycoprotein in skin, joints, heart. Deposited in tissues --> inflamm reaction.
Carditis: Aschoff Bodies in heart (granulomas with giant cells)
--> Fever, polyarthritis, carditis, chorea (syndenhams), skin nodules, erythema
ASO and ESR elevated
Rheumatic carditis --> chronic (mitral stenosis).

11

Post-strep glomerulonephritis

Initial strep infxn - skin or rarely sore throat.
Lag 1-4 weeks. Malaise, fever, oliguria, hematuria, azotemia (^ BUN, creatinine, v GFR ie decreased), HTN.
Immune complex (Type III HS) - ab to strep circulate, ag and ab. Deposit in BM of glomeruli. Complement activated --> actue inflamm. REsolves spont in most patients.

12

Components of pseudomembrane

Necrotic cells, bacteria, PMN, and exudate

13

Diphtheria toxin (Cornyebacterium diphtheria)

Gram +ve rod produces exotoxin. ADP ribosylation of EF-2, inactivating protein synthesis. Clin: Fever, dysphagia, Lymph enlargement (neck, Bull neck), laryngeal edema, gray material (pseudomembrane) covering tonsils and pharynx. = Necrotic cells, fibrin, bacteria, PMN, exudate.
From necrosis of mucosa --> pseudomembrane. Complications: myocarditis, heart failure, spinal nerve or recurrent laryngeal n. paralysis.

14

Pseudomembranous Colitis

Antibiotic associated - destroy normal flora. Clinda, cephalosporin, amoxicillin, ampicillin.
Etiology: C. difficile (gram + bacillus, normal resident) --> enterotoxins A and B, necrosis of mucosa.
Fever, ab cramps, diarrhea (water +/ blood).
Mucosal suppurative inflamm, vascular thrombosis, necrotic mucosa --> pseudomembrane (necrotic debris, PMNs, bactria, fibrin).
Invest: C diff toxins in stool

15

Pseudomembranous Colllitis commonly sen post use of which antibiotics

Clinda, cephalosporin, amoxicillin, ampicillin.

16

Clostridia Perfringens

Gram pos bacilli, anaerobic, produce spores found in soil. Invade traumatic and surgical wounds - 14 toxins, Alpha toxins (Lecithinase). Degrades lecithin (cell membrane), destroys RBCs, platlets, myonecrosis. Enzymes from necrotic tissue --> degradative --> produce gas in tissues.

17

Typhoid Fever (enteric fever)

Salmonella typhi (gram neg rod) or salmonella paratyphi (predom in travelers). Humans SOLE reservoir. Ingestion of contaminated food and water. Enters ileal wall --> M cells take up --> mononuclear cells engulf (lymphoid tissue) --> blood stream --> bacteremia. Blood --> organs. Liver - typhoid nodules with kupffer hyperplasia, hemorrhagic necrosis foci, macrophage collections (week 2). Enlarged, soft spleen - typhoid nodules. Mucosal necrosis week3
NO PMNS

18

Clinical features of enteric fever

Anorexia, fever, headache, abdominal pain, constipation, diarrhea +- skin rash (ROSE SPOTS), toxic appearance, BRADYCARDIA (due to ENDOTOXIN decreasing HR)

DX: CBC (leukopenia endotoxin effect on bone marrow).

19

Causes of gram negative sepsis

E. Coli (most common),H. influenza, pseudomonas auerguinosa, klebsiella, proteus and serratia

20

HSV-2

Remains latent in sensory ganglia. Fever, malaise, recurrent vesicles --> ulcers. HSV culture and Tzanck preparation --> see multinuc giant cells and eosinophilic intranuclear inclusions (cowdry type A). Complications incl meningitis in adults, encephalitis in neonates.

21

Cowdry A

Eosinophilic intranuclear inclusions with halo and marginated nucleus. Seen in HSV-1 HSV-2 and VZV.

22

Varicella Zoster virus

Airborne transmission. Exposure --> IgG pdn (lifelong immunity). Also cell-mediated immunity. Remains latent in DRG (see drg necrosis lab)
VESICULAR skin rash (lesions restricted to EPIDERMIS), fever, headaches, malaise.
Lab: viral culture, Tzanck smear from vesicles.
Complications: pneumonia, herpes zoster.
Cowdry type A, nuclear moulding, fused nuclei, giant cells

23

CMV infection

Common cause of pneumonia, in immunocopmromised. Common opportunistic viral pathogen inAIDs patients esp who get transplant (CD4 <50****)
Clin: pneumonitis (mononuclear infiltrates, foci of necrosis, and cytomegalic changes)
retinitis: blurring, double vision, cotton wool spots both eyes. Colitis: diarrhea. Esophagitis: odynophagia, fever, retrosternal chest pain
Dx. PCR assay viral culture and tissue section.enlarged alveolar macrophages, eosinophilic nuclear inclusions with halo.

24

Rabies

Raccoons, bats, wild dogs
Incubation period - depends on site of bit. Faster if closer to brain. Virus vinds preipheral nerves then by retrograde transport (dynein) enters DRG. and spinal cord -> brain. Encephalitis.
Prodrome: 2-10 daysadvanced infxn: CNS excitability, paral, hypersalivation, hydrophobia, convulsion.
Negri bodies: intracytoplasmic inclusions

25

Measles (rubeola)

RNA paramyxovirus. Inhalation of droplets -- virus enters lymph then enters blood. Fever, coryza (runny nose), conjunctivitis, koplik spots and cough. uncomplicated: lasts 7-10 days. Dx: serology for IgG or IgM
Measles giant cells (esp in lung)
Complciation: pneumonia, otitis media, encephalitis.

26

HPV viral warts

Viral warts. Exophytic, papillary architecture. Hyperkeratosis , acanthosis. Verruca vulgaris

27

Pneumocystis Jiroveci Pneumonia

P. Jiroveci: Risk factor advanced HIV infectino (<200 CD4), may affect severely malnourished children, organ transplant pts, chemotherapy. SOB, dry cough, hypoxia. DX: chest x ray, BAL (most accurate)

28

Cryptococcus neoformans

Budding yeast with narrow based buds, surrounded by thick capsule. Pigeon excreta.
Risk: HIV, organ transplant, leukemia, lymphomas.
Virulence: Polysacch capsule (inhibits phago, leukocyte migration, inflamm recruitment)
Primary lung disase (40%) - granulomatous inflamm with caseation. Do NOT have to be immunocompromised
Dissemination: meningitis and meningoencephalitis
Clin: fever, dry cough

29

Histoplasmosis

Histoplasma capsulatum. Most common systemic fungal infxn. Construction sites (ohio & mississippi). Spores in dust with excreta from bats, starlings, chickens. Weak immunity --> inhalation --> multiplication within macrophages --> organ spread via lymphatics.
Usually asymptomatic, flue like. Fever, fatigue, night sweats, dry cough. SIm to TB.
Acute primary pulmonary infxn, chronic granulomatous pulmonary disease, disseminated miliary disease.
D: CXR, CT, serology, BAL with comori methenamine silver tain, fine needle asp.

30

Mechanisms of Damage by foreign organisms

Direct tissue injury - impetigo
Exotoxins - enzymes (exfoliative toxin protease from S .aureus),A B toxins (diphtheria), superantigens (TSS), neurotoxins (C. Tétani), enterotoxins (C. Diff)
Endotoxins: LPS, LOS --> septic shock (DIC)
Vascular damage: ischemic injury (Rickettsia and fungi)
Indirect tissue injury: cells eath via host immune response ie Rheumatic heart disease