Wk 9: Microbiology highlights Flashcards by Morgan Evans

Nearly all bacteria have what 2 things? How do they differ in G+ and G- cells?

1) An inner plasma membrane
2) A cell wall made of peptidoglycan
Much thicker in gram+ bacteria than in gram-

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Gram _______ bacteria have an additional outer membrane that’s an asymmetric bilayer with ______________________ on the outside

negative; lipopolysaccharide (LPS)

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What happens when you apply lipid detergent (e.g., alcohol) in gram staining in G+ and G- organisms?

1) In gram-, outer membrane is washed away (bc of only having thin cell wall (more permeable)) + crystal violet in cell is also washed away > cell becomes colorless
2) Gram+ retain the crystal violet in cell because of the thicker cell wall > appear purple

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Give a notable example of acid-fast bacteria

Mycobacterium (e.g., M. tuberculosis)

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Gram Negative bacteria:
1) What in outer membrane is a potent endotoxin?
2) LPS is highly antigenic and leads to a ____________ inflammatory response (gram- sepsis).
3) G- bacteria causes __________ local tissue damage.
4) The outer membrane of Gram- bacteria also makes them ____________ resistant to many antibiotics compared to Gram+.

1) LPS
2) systemic
3) limited
4) more

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Gram-Positive Bacteria:
1) Do they have local tissue damage?
2) What does it cause less of than gram-negative?

1) Yes; kills the tissue it is infecting
2) Less systemic disease

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What are the three basic groups of bacteria based on shape?

1) Cocci (round/spheres)
-pairs (diplococci), chains (strep), or clusters (staph)
2) Bacilli (rods)
3) Spirochetes (spiral shaped)

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Classical Categorization of Medically Important Bacteria: list the 2 groups that both have rigid, thick cell walls

1) Extracellular (free-living)
-Gram+ cocci and rods
-Gram- cocci and rods
2) Obligate intracellular parasites (non-free living)

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List/ describe the 2 main types of Staph (Clusters) [staphylococci]

1) Staphylococcus aureus (coag. +)
-MRSA and MSSA
2) Staph. epidermidis (coag. -)

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Strep (Chains) [streptococci]: List/ describe the 3 groups

1) Strep. Pyogenes + Strep. Agalactiae = complete hemolysis
2) Strep. viridans +Strep. pneumoniae = incomplete
3) Enterococcus = no hemolysis

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1) What are the 2 main groups of G+ cocci?
2) What are the 2 main groups of G+ rods?
3) What are the 2 main groups of G- [diplo]cocci?

1) Staph (Clusters) + Strep (Chains)
2) Spore-forming + non-spore-forming
3) Neisseria + Moraxella
-incl. n meningitidis + n. gonorrhea

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List and describe the 3 groups of facultative (can grow with or without free oxygen) G- rods

1) Resp. organisms: Haemophilus influenzae, Bordetella pertussis, Legionella pneumophila.
2) Zoonotic organisms: Brucella canis, Francisella, Pasteurella, Yersinia pestis, Toxoplasma gondii (cats)
3) Enteric (intestinal) and related organisms:
a) Enterobacter, Serratia, Klebsiella, Proteus, Helicobacter pylori
b) Diarrhea (Sx):
-Watery: ETEC E. coli, cholera, salmonella
-Bloody: EHEC E. coli, Shigella, campylobacter

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True or false: The only spore-forming bacteria are gram positive rods

True

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What are the 2 main groups of spore-forming bacteria? List whether each is anerobic or aerobic, and list members of each

1) Bacillus (aerobic): bacillus anthracis and cerus
2) Clostridium (anaerobic)
-Clostridium perfringens
-Clostridium tetani
-Clostridium botulinum
-Clostridium difficile

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List 4 examples of non-spore-forming G+ rods

1) Actinomyces
2) Nocardia
3) Listeria
4) Corynebacterium (e.g., C. diphtheriae)

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List the 2 main groups of G- diplococci

1) Neisseria (meningitidis and gonorrhoeae)
2) Moraxella (M. catarrhalis)
(both typically diplococci)

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Give examples of facultative G- rods

1) Haemophilus (H. influenzae)
2) Bordetella (B. pertussis)
3) Legionella (L. pneuomophila)
4) Brucella (B. canis)
5) Francisella
6) Pasteurella
7) Yersinia (Y. pestis)
8) Toxoplasma gondii
9) Enterobacter, serratia, klebsiella, proteus, Helicobacter
10) Enterotoxigenic Escherichia coli (E. coli)
11) V. Cholera
12) Salmonella + Shigella
13) Campylobacter

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List important exmaples of spirochetes (G- bacteria)

1) Treponema pallidum
2) Borrelia (B. burgdorferi)
3) Leptospira

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1) Give an example of a bacteria without a cell wall (not visible on gram stain)
2) Give an example of Acid-Fast Bacteria/Bacilli (AFB)

1) Mycoplasma (M. pneumoniae)
2) Mycobacterium (TB and leprosy)

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There are various methods for determining _________/_________ of bacteria to antibiotics, such as ___________ methods (e.g., broth microdilution)

sensitivity/resistance; dilution

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1) What do quantitative dilution methods determine?
2) How are these ranges classified?

1) MIC (minimum inhibitory concentration)
2) Into susceptible, intermediate, or resistant categories

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What are 2 ways to test for antibiotic susceptibility?

1) Quantitative dilution method
2) Kirby-Bauer method (disk diffusion test)

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What does the Kirby-Bauer method (disk diffusion test) show?

Diameter of inhibited growth measured = “Zone of inhibition” (ZOI)
(larger area of clarity = more effective)

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Is the Kirby-Bauer method (disk diffusion test) more qualitative or quantitative? Explain

Qualitative; relationship of ZOI diameter is not always linear to MIC

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As susceptibility of the organism to the drug ↑, what do ZOI and MIC do? **"very important"**

↑ ZOI and ↓ MIC

What do S and R mean on a C&S (culture & sensitivity)

S = susceptible/sensitive R = resistant

Give 4 examples of diagnostic studies for Entamoeba histolytica (protozoa)

1) E. histolytica-specific stool antigen test 2) Stool microscopy 3) Sigmoidoscopy (may supplement microscopy) -biopsy 4) Blood serologic testing

What is Entamoeba histolytica known for?

Liver abscesses

True or false: Blood serologic testing for entamoeba histolytica doesn't differentiate acute vs chronic

True

1) What protozoa can cause malabsorption-induced steatorrhea? 2) What does this organism look like on a stool specimen? 3) What immunoassay tests are now widely used with a almost perfect sensitivity/ specificity?

1) Giardia lamblia 2) Double-nucleated flagellated organisms 3) Stool antigen

Toxoplasma gondii: 1) Is an ____________________ protozoan, esp found in _________. 2) What is the most important diagnostic method? 3) What can this pathogen cause? (2 things)

1) obligate intracellular; cats 2) Serology using Anti-toxoplasma IgM and IgG antibodies 3) Congenital infection and reactivate in immunocompromised

Trichomonas vaginalis: How was it traditionally diagnosed?

Microscopic “wet mount”; motile flagellates

What causes malaria? What 4 species specifically? List the key facts of each

Plasmodium: 1) P. falciparum: most fatal 2) P. malariae: 72hr (longer) life cycle 3&4) P. ovale + P. vivax: dormant + relapse

List the 3 general stages of malaria

1) Sporozoite infects liver 2) Merozoites infect RBCs 3) Also forms gametocytes

Malaria: 1) Can be dx'd with light microscopy examination of Giemsa-stained ______________ 2) Or with ______________ tests that detect parasite antigens (but do NOT quantify the degree)

1) blood smear 2) Rapid antigen tests

Give an example of a molecular test used to Dx malaria and how it works

Nucleic acid tests (e.g., PCR): amplify parasite DNA

True or false: Malaria can cause anemia

True

1) What are viruses contained in? 2) What else are they sometimes contained in? What are they called if they aren't contained in this?

1) Capsid 2) Envelope (stolen from host cell); naked

True or false: there are both DNA and RNA viruses

True

What is the general life cycle of a virus? (3 steps)

1) Invade 2) Replicate 3) Exit

1) How do naked viruses invade? 2) What abt enveloped viruses?

1) Attach and penetrate using capsid proteins, then uncoats and releases genome 2) Glycoproteins facilitate plasma membrane fusion

1) How/ when do naked viruses exit? 2) When do enveloped viruses exit?

1) Until host cell ruptures; cytolytic + will be an acute process 2) Acute, chronic, or latent

1) Epstein-Barr Virus (EBV) is the most common cause of what? 2) How is it diagnosed?

1) Infectious mononucleosis (IM) 2) Atypical lymphocytosis + heterophile antibody test (e.g., Monospot) or EBV-specific antibody testing

EBV 1) What is a downside to Heterophile antibody test (e.g., mononucleosis spot test [Monospot])? **(know this)** 2) What is the gold standard for diagnosis of EBV-associated IM?

1) Can be falsely negative in early illness and in kids <4 yo. (e.g., first several weeks) 2) EBV-specific antibodies (IgM and IgG antibodies):

1) Low-risk HPVs mostly cause what? 2) What abt high-risk?

1) No disease 2) Cancer (particular strains 16 and 18)

1) What are the 2 main groups of HPV-related cancers? 2) The HPV vaccine ________________ protects against infection from nine HPV types (nonavalent) 3) HPV infection with some types is characterized by __________ on the invaded tissue

1) Anogenital and oropharynx 2) Gardasil 9 (2-part series, boys and girls, starting between ages 9-12) 3) warts

Human Papillomavirus (HPV): 1) Which 2 strains cause plantar (feet)/common hand warts? 2) Which cause ~90% of anogenital warts (condylomata acuminata)?

1) HPV 1, 2 2) HPV 6, 11

Human Papillomavirus (HPV): 1) How is it usually diagnosed? 2) What is the one example of lab tests being useful?

1) Clinically 2) Cervical cancer screening

1) What causes influenza (the flu)? 2) What kind of illness is it?

1) Orthomyxovirus (don't confuse w. H. influenza) 2) Acute febrile respiratory

List the lab tests available for influenza (the flu)

1) Molecular assays (e.g., nucleic acid) 2) Antigen detection assays: not v. sensitive 3) Viral culture

Varicella-Zoster Virus (VZV): 1) What is the initial infection called? 2) What abt reactivation?

1) Chicken pox (varicella) 2) Shingles (herpes zoster)

Varicella-Zoster Virus (VZV): Is usually a __________ diagnosis, but __________ testing may be used to determine if an individual is susceptible to infection/requires immunization (e.g., healthcare workers born in U.S. after 1980)

clinical; serologic

What causes rabies?

Rhabdovirus

Cytomegalovirus (CMV): 1) Can cause clinical presentations in __________ pts, and can also cause ___________ infections. 2) Can it usually be diagnosed on clinical grounds alone?

1) immunocompromised; congenital 2) No

Describe diagnostic tests for CMV

1) Viral replication: quantitative PCR preferred -ex: for Dx/ monitoring immunocompromised or reactivation 2) Tissue-invasive disease: Intracytoplasmic inclusions (“owls’ eyes”) 3) Serology: dx primary infection in immunocompetent pts 4) Cultures

1) What is preferred to Dx CMV? 2) What can it look like on tissue biopsy?

1) Quantitative PCR 2) Intracytoplasmic inclusions (“owls’ eyes”)

Herpes Simplex Virus (HSV) 1) How is it usually diagnosed, clinically or not? Explain 2) What are the 2 ways to Dx? 3) Which Dx method is most sensitive?

1) Usually clinically but should be confirmed with lab testing 2) Generally through PCR (preferred) or viral culture from active lesion. 3) PCR

Tzanck smear tests for what? What does it do?

Confirms herpetic lesion, cannot differentiate between VZV and HSV

When is an appropriate situation to use HSV serology?

Dx if no active lesions

List 2 viruses that can be Dxs via Tzanck Smear

HSV and VZV

Tzanck Smear: 1) Shows ____________________ cells with HSV or VZV. 2) Can it distinguish between HSV-1, HSV-2, and VZV?

1) “multinucleated giant cells” 2) No

Give 3 examples of STIs

1) Trichomonas 2) HSV 3) HPV

Treponema pallidum (spirochete) causes what?

Syphilis

1) What is the recommended approach to Dx syphilis? 2) What 2 things should it include? Explain

1) Serology 2) Nontreponemal and treponemal antibody tests -Either type of test can be used for initial screening (in pt w. no Hx)

Syphilis: 1) If the initial screening is positive, what is needed? 2) What abt if negative? 3) Can false positives or negatives occur?

1) Confirmatory testing; potential for false positives 2) No additional tests (unless possible recent exposure) 3) False-positives may occur (esp nontreponemal tests); may be falsely negative (in early disease or advanced immunosuppression)

What are the 2 kinds of serology tests for syphilis? Give examples of each ("know examples")

**1) Nontreponemal: RPR, VDRL 2) Treponemal: TP-EIA, FTA-ABS** (T. pallidum enzyme immunoassay, fluorescent treponemal antibody absorption)

Gonorrhea: 1) What is the test of choice? 2) What are the preferred specimen types for urogenital infections? 3) What can culture determine?

1) Nucleic acid amplification testing (NAAT) 2) Vaginal swabs in females; first-catch urine in males 3) Antibiotic susceptibility

True or false: chlamydia and gonorrhea have the same preferred test and specimen types

True

Which bacteria is an example of a Gram- rod? a. N. gonorrhoeae b. E. coli c. Staph. aureus d. Strep

b. E. coli

What has a Tzank smear historically been used for? a. HSV b. VSV c. RSV d. TVV

a. HSV [and VZV]

Which STI has motile flagellated organisms on a wet mount? a. gonorrhea b. chlamydia c. trichomonas d. syphilis

c. trichomonas

Trichomonas is what type pathogen?

Protozoa

List 3 (G-) spirochetes

1) Treponema (e.g., T. pallidum) 2) Borrelia (e.g., B. burgdorferi 3) Leptospira

Toxoplasma gondii is a _________________ but trophozoites appears as pink-purple rods when stained

protozoan

G- rods: 1) Give an example of aerobic 2) Anerobic? 3) Obligate intracellular?

1) Pseudomonas 2) Bacteroides 3) Chlamydia trachomatis + Ricketssia

1) Give an example of a bacteria without cell walls (not visible on gram stain). 2) Give an example of a Acid-Fast Bacteria/Bacilli (AFB)

1) Mycoplasma 2) Mycobacterium (M. tuberculosis + M. leprae)

Wk 9: Microbiology highlights Flashcards

(76 cards)