Module 9

Question 1

What is the smallest infectious agent?

Answer 1

Virus

Question 2

What types of viruses are there?

Answer 2

Bacteriophages

Plant

Animal

Question 3

What are the characteristics of viruses?

Answer 3

Only one type of nucleic acid (RNA or DNA)

30-300nm

Nucleic acid surrounded by capsid

Lipid envelope

May have glycoprotein spikes

Question 4

How do viruses replicate?

Answer 4

Intracellular parasites

Attachment to host

Penetration- pinocytosis/fusion

Uncoating- nucleic acid released

Viral synthesis using host cell enzymes

Assembly- nucleic acid and capsid combined with membrane and spikes

Release by cell lysis or virus is pinched off

Question 5

How are viral infections diagnosed?

Answer 5

Electron microscope- morphology

Culture grown in host cells

Serological ID with specific Abs

Nucleic acid probes

Question 6

What different Abs are used for serological ID?

Answer 6

IgM- short term, 1-2 weeks, peak at 3-6, gone at 2-3 months

IgG- long term, 1-2 days after IgM, peak at 4-12 weeks, remain for months/years

Question 7

What can be used to treat viral infections?

Answer 7

Antivirals and symptom management

Abacavir- HIV

Acyclovir- HSV I and II

Interferon

Question 8

What are the characteristics of Mycobacterium tuberculosis?

Answer 8

Acid fast

Rods that may be bent or branching

High lipid content in cell wall

Very slow growth

Obligate aerobes

Question 9

What stains are used for Mycobacterium tuberculosis? What are the results?

Answer 9

Ziehl Neelson- light mic

• AFB are red
• Everything else is blue/green

Fluorochrome stain- UV mic

• AFB are bright yellow/gold
• Other bacteria/cells are pale yellow
• Background is dark

Question 10

What are the fluorochrome stains used for Mycobacterium tuberculosis?

Answer 10

Auramine

Rhodamine

Question 11

What is used for rapid presumptive diagnosis of Mycobacterium tuberculosis?

Answer 11

Direct smears of sputum

Question 12

What stain shows more positive bacteria for Mycobacterium tuberculosis?

Answer 12

Fluorochrome- low power, larger field

Question 13

What culture is used for Mycobacterium tuberculosis?

Answer 13

Enriched with eggs, serum or albumin

Question 14

How does radio metric detection of Mycobacterium tuberculosis work?

Answer 14

Medium is enriched with C14 incorporated albumin

Radioactive carbon is detected in the airspace (10 days)

Question 15

What is the pathogenicity of Mycobacterium tuberculosis?

Answer 15

Lung disease, can spread to lymph glands, meninges, kidney, bone

Can lie dormant for decades

Question 16

What is the resistant strain of Mycobacterium tuberculosis?

Answer 16

XDR TB

Question 17

What is the treatment for Mycobacterium tuberculosis?

Answer 17

Isoniazid

Rifampin

Combo with pyrazinamide or streptomycin sulfate

Question 18

What specimens are available for Mycobacterium tuberculosis testing?

Answer 18

Sputum

Urine

Tissue

Spinal fluid

Question 19

What is the Mantoux test?

Answer 19

Screens for Abs against TB

If pos, follow with chest X-ray

Question 20

What causes syphilis?

Answer 20

Treponema pallidum

Question 21

What are the characteristics of Treponema?

Answer 21

Helical

Fibrils wrap around the cell wall, enclosed in sheath

Rotates in corkscrew fashion to move

Question 22

What is the progression of syphilis?

Answer 22

Primary- chancre 1-2 weeks after contact, clears up in 6 weeks

Secondary- bacteria invade bloodstream, 2-6 months after chancre

Tertiary- 10-20 years after primary, lesions in vital organs

Question 23

How is Treponema pallidum demonstrated?

Answer 23

Observe movement with dark field condenser

Question 24

What is the diagnosis for Treponema pallidum?

Answer 24

Serological test for reagin (non specific)

RPR is confirmed to be syphilis by fluorescent Ab and hemagglutination

Question 25

What is the treatment for Treponema pallidum?

Answer 25

Penicillin G Tetracycline

Question 26

What are the characteristics of Mycoplasma?

Answer 26

Lack cell wall Require sterols for growth and membrane function Slow growth

Question 27

What media will Mycoplasma grow on?

Answer 27

Enriched with yeast extract and serum

Question 28

What is the pathogenicity of Mycoplasma pneumoniae?

Answer 28

Primary atypical pneumonia (young people) Resolve without issue Results in cold agglutins

Question 29

What is the pathogenicity of Mycoplasma hominis and Ureaplasma urealyticum?

Answer 29

Genital infections that may cause sterility

Question 30

What is the treatment for Mycoplasma infections?

Answer 30

Tetracycline and erythromycin Can't target cell wall

Question 31

What is the diagnosis for Mycoplasma infections?

Answer 31

High titres of IgM (cold hemagglutinins) Specialized cultures DUO KIT for genital detection

Question 32

What are the characteristics of Chlamydia?

Answer 32

Obligate intracellular parasites Have RNA and DNA Gram negative type cell wall without peptidoglycan Binary fission

Question 33

What is the most common Chlamydia infection in humans?

Answer 33

Chlamydia trachomatis

Question 34

What is the life cycle of Chlamydia?

Answer 34

Attacks columnar epithelial cells Elementary bodies attach to cell receptors Endocytosis, EBs reorganized to form larger reticulate body (RB) RB divides, form inclusions Condense to form EBs Host cell ruptures, releasing EBs to infect cells

Question 35

What is the pathogenicity of Chlamydia trachomatis?

Answer 35

Trachoma- greatest single cause of blindness Lymphogranuloma venereum- genital lesion, spreads to lymph nodes STI- urethritis and cervicitis (most common in North America)

Question 36

How is Chlamydia cultured?

Answer 36

Only grown in suitable host cells Inoculate McCoy cells with EBs Detect growth by inclusions

Question 37

How else can Chlamydia be detected?

Answer 37

Direct fluorescent Ab- monoclonal Abs for EB and RB (bright green) Nucleic acid detection- gene probe for rRNA (combo for Chlamydia and gonorrhoea, follow with specific)