Bacterial Infections Part 2 Flashcards Preview

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Flashcards in Bacterial Infections Part 2 Deck (32):
1

Pseudomonas Infection

- P.aeruginosa, opportunistic aerobic Gram-negative bacillus.
- Seen in those with CF, burns, neutropenia, and is often a hospital-acquired infection.
- Causes corneal keratitis in contact lens wearers and external otitis (swimmer's ear).

2

Pseudomonas Infection Virulence Factors

- Pili and adherence proteins that bind to epithelial cells and lung mucin.
- Endotoxin that cause gram-neg sepsis.
- Exotoxin A that inhibits protein synthesis like Diptheria.
- Phospholipase C that lyses red cells and degrades surfactant and an elastase that degrades IgG and ECM.
- In those with CF, secretes an exopolysaccharide (alginate) that forms a slimy biofilm that protects bacteria.

3

Pseudomonas Findings

- Skin infections give rise to well-demarcated necrotic and hemorrhagic skin lesions, exthyma gangrenous.

4

Plague

- Yersinia, gram-neg facultative intracellular bacterium.
- Pestis causes plague, transmitted from rodents to humans by aerosols or fleas.
- Enteocolitica and pseudo tuberculosis cause fecal-oral transmitted ileitis and mesenteric lymphadenitis.

5

Yersinia Virulence

- Toxins called Yops are injected into host by a syringe-like mechanism, they block phagocytosis and cytokine production.
- A biofild obstructs the flea GI tract, causing it to throw up prior to feeding and thus infection ensues.

6

Yersinia Findings

- Massive lymph node involvement (buboes), pneumonia, and sepsis, with extensive bacterial proliferation, tissue necrosis, and neutrophilic infiltrates.

7

Granuloma Inguinale

- STI caused by Klebsiella (encapsulated coccobacillus)
- Begins as a papule on genitalia or elsewhere that ulcerates and granulates to form a soft, painless mass with prominent epithelial hyperplasia at borders.
- Lesion may scar and cause strictures.

8

Tuberculosis

- Second leading cause of death worldwide (after HIV)
- Transmitted via aerosol.
- Virulence is based on the properties of its waxy cell wall made of mycolic acid.

9

Tuberculosis Findings

- TH1 mediated delayed hypersensitivity response that activates macrophages via interferon gamma to promote endocytosis and killing via NO, promote cidal activity through TNF production, surround microbes with granulomatous inflammation.
- Caseating granulomas are characteristic, central necrosis surrounded by lymphocytes and activated macrophages.

10

Tuberculosis Caseating Granulomas

Formed in response to infection typically involved the lung apex and draining lymph node; these are called a Ghon complex.

11

Leprosy

- Also called Hansen's Disease.
- Waxy cell wall made of mycolic acid: M. Leprae.
- Inhaled M, Leprae are phagocytized by pulmonary macrophages and spread hematogenously.
- Secretes no toxins, virulence from cell wall.

12

Tuberculoid Leprosy

- TH1 response (IFN-gamma)
- Granulomatous inflammation-few bacilli.
- Insidious, dry, scaly skin lesions lacking sensation, peripheral nerve involvement and local anesthesia with skin and muscle atrophy that increase risk of chronic ulcers and autoamputation.

13

Lepromatous (anergic) Leprosy

- Relatively ineffective TH2 response.
- Large collections of lipid-laden macrophages overstuffed with bacilli.
- Disfiguring cutaneous thickening and nodules, with nervous system damage due to mycobacterial invasion into perineural macrophages and Schwann cells.
- TESTES are extensively involved = STERILITY.

14

Spirochetes

- Gram-negative, corkscrew-shaped bacteria with flagella.

15

Syphillis

- Treponema pallidum (venereal or transplacental)
- Delayed TH1 hypersensitivity.

16

Primary Syphillis

- Occurs 3 weeks after contact.
- Firm, contender, raised, red lesion (chancre) forms on the penis, cervix, vaginal wall, or anus (self heals).
- Visible with silver or immunofluorescent stain.
- Exudate composed of plasma cells, macrophages, and lymphocytes.

17

Secondary Syphillis

- Spread and proliferation of spirochetes in skin (including palms and soles) and mucocutaneous tissues (especially mouth).
- Lesions are painless and contain infectious spirochetes.
- Lymphadenopathy, mild fever, malaise, and weight loss are common.

18

Tertiary Syphillis

- Cardiovascular syphilis (>80%) results in aortitis with aortic root and arch aneurysms and aortic valve insufficiency.
- Neurosyphilis can be symptomatic (tabes dorsal is) or asymptomatic.
- Benign Tertiary is associated with necrotic rubbery masses (gummas) which form in various sites.

19

Congenital Syphilis

- Early congenital syphilis includes nasal discharge, a bullous rash with skin sloughing, hepatomegaly, and skeletal deformities.
- Late congenital manifestations include notched central incisors, deafness, and interstitial keratitis with blindness (Hutchinson triad).

20

Relapsing Fever

- Insect transmitted spirochetal diseases caused by Borrelia species. Seen in blood smears during febrile periods.
- Fever, headache, and fatigue, followed by DIC and multi organ failure.
- Caused by body louse.

21

Lyme Disease

- Caused by B. Burgdorferi (spirochetes) transmitted from rodents to Ixodes ticks.
-B. burgdorferi evade immunity through antigenic variation. Pathology due to host immune response.

22

Lyme Disease Stages

- Stage one: Erythema chronic migrans (red targets), fever, and lymphadenopathy.
- Stage two: Hematogenous spread, skin lesions, migratory joint and muscle pain, cardiac arrhythmias, and meningitis.
- Stage 3: encephalitis and polyneuropathy, occasionally a destructive arthritis.

23

Clostridium

- Gram-pos bacillus anaerobes that produce spores in soil.
- Causes cellulitis and muscle necrosis in wounds, food poisoning, and small bowel infection in ischemic or neutropenic patients.

24

Costridium Perfringens Toxins

- Alpha-toxin: contains phospholipase C, which degrades erythrocyte, muscle and platelet cell membranes and sphigomyelinase which causes nerve sheath damage.
- Enterotoxin lyses GI epithelial cells and disrupts tight junctions, causing diarrhea.

25

C. Tetani

- In wounds, releases a neurotoxin that causes tetanus - convulsive contractions of skeletal muscles - by blocking the GABA.

26

C. Botulinum

- Grows in canned foods, neurotoxin that causes flaccid paralysis of respiratory and skeletal muscles by blocking acetylcholine release.
- Botox used in cosmetic surgery.

27

C. Difficile

- Overgrows other intestinal flora in antibiotic treated patients. Releases two glucose transferase toxins:
--Toxin A stimulates chemokine production to recruit leukocytes.
--Toxin B (used for diagnosis) causes cytopathic effects in cultured cells.

28

Chlamydia

- Small gram-neg bacteria.
- Metabolically inactive but infectious spore-like elementary body (EB) is internalized by receptor-mediated endocytosis.
- Inside host cell endosomes, the EB differentiates into the metabolically active reticulate body (RB).

29

Chlamydial Types

- A, B, C: Trachoma, an ocular infection in children.
- D-K: STIs, most common STI

30

Chlamydial Findings

- Mucopurulent discharge containing neutrophils but no visible organisms by gram stain.

31

Rickettsial Infections

- Caused by gram-neg bacilli transmitted by arthropods.
- Primarily infect endothelial cells, causing endothelial swelling, thrombosis, and vessel wall necrosis.
- NKC and cytotoxic T-cells necessary to contain and eradicate infection.

32

Rickettsial Types and Trasmissions

- Epidemic Typhus (Rickettsia prowazekii) transmitted by body lice. (Skin necrosis and gangrene)
- Rocky Mountain Spotted Fever (R. rickettsii) transmitted by dog ticks. (Hemorrhagic RASH)