Wk 9: Microbiology highlights Flashcards
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-
Gram _______ bacteria have an additional outer membrane that’s an asymmetric bilayer with ______________________ on the outside
negative; lipopolysaccharide (LPS)
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
Give a notable example of acid-fast bacteria
Mycobacterium (e.g., M. tuberculosis)
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
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
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)
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)
List/ describe the 2 main types of Staph (Clusters) [staphylococci]
1) Staphylococcus aureus (coag. +)
-MRSA and MSSA
2) Staph. epidermidis (coag. -)
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
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
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
True or false: The only spore-forming bacteria are gram positive rods
True
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
List 4 examples of non-spore-forming G+ rods
1) Actinomyces
2) Nocardia
3) Listeria
4) Corynebacterium (e.g., C. diphtheriae)
List the 2 main groups of G- diplococci
1) Neisseria (meningitidis and gonorrhoeae)
2) Moraxella (M. catarrhalis)
(both typically diplococci)
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
List important exmaples of spirochetes (G- bacteria)
1) Treponema pallidum
2) Borrelia (B. burgdorferi)
3) Leptospira
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)
There are various methods for determining _________/_________ of bacteria to antibiotics, such as ___________ methods (e.g., broth microdilution)
sensitivity/resistance; dilution
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
What are 2 ways to test for antibiotic susceptibility?
1) Quantitative dilution method
2) Kirby-Bauer method (disk diffusion test)
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)
Is the Kirby-Bauer method (disk diffusion test) more qualitative or quantitative? Explain
Qualitative; relationship of ZOI diameter is not always linear to MIC
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 HPVsmostly 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 fromnine 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)
