Microbes

Question 1

General classes of organisms that can cause infectious disease

Answer 1

Bacteria
Fungi (eukaryote)
Protozoa (Eukaryote)
Arthropods (eukaryote)
Helminths (eukaryote)
Viruses
Prions

Question 2

Names of unicellular and multicellular fungi

Answer 2

Yeast; Hyphae (mold)

Question 3

Examples of parasites and their class

Answer 3

Scabies mite (arthropod)
Malaria (protozoan)
Giardia (protozoan)
Trichuriasis trichuria (AKA whipworm, helminth)

Question 4

Disease associated with prions

Answer 4

spongiform encephalopathies including:
Kuru
Creutzfeldt-Jacob Disease (CJD)
Mad Cow Disease

Question 5

Relative size of medically important organisms

Answer 5

virus < bacteria < protozoa < helminths

Question 6

Serogroup, serotype, biotype are all synonymous with…

Answer 6

strain

Question 7

Classification of bacteria is according to…

Answer 7

gram + or -, shape, respiration, reproduction (spores?)

Question 8

Classification of viruses is according to…

Answer 8

nucleic acid type and sense, presence of envelope, symmetry

Question 9

Pathogenicity vs.Virulence

Answer 9

Pathogenicity: the quality of being pathogenic
Virulence: the intensity of the pathogenicity

Question 10

Contrast colonization and infection

Answer 10

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Question 11

Medical examples of mutualism, commensalism and parasitism

Answer 11

Mutualism: gut bacteria that make vitamin K for us
Commensalism: gut bacteria that get a free place to live
Parasitism: worms

Question 12

Strict pathogens vs. opportunistic pathogens

Answer 12

Strict pathogens always cause disease, opportunistic pathogens are not normally pathogenic, but can become so in abnormal situations (e.g. in immunocompromised individuals)

Question 13

Development of normal flora

Answer 13

skin, oropharynx and GI are colonized during passage through birth canal and first few days of life (including breastmilk)

Question 14

Influences on normal flora

Answer 14

oxygen levels
antibacterial substances (e..g lysozyme)
Other flora

Question 15

Benefits of normal flora

Answer 15

Food metabolism
Produce vitamins (B and K)
Normal immune system development
Exclusion of pathogenic microbes via competition of secretiong of toxic metabolites

Question 16

Examples of bacterial metabolites that alter their environment

Answer 16

Lactobacilli –> acidic env. in vagina
Bifidobacterium–> decrese gastric pH in breastfed infants
Bacteriocins (antibacterial factors)

Question 17

Probiotics vs. Prebiotics

Answer 17

Live bacteria (e..g bifidobacterium, lactobacillus) (…can also be fecal transplant)

Non- digestable food ingredients that stimulate the growth of a select group of microbes (e.g soluble and dietary fiber, inulin)

Question 18

Examples of immunocompromised individuals

Answer 18

Bone marrow transplant pts are on prophylactic antibiotics

HIV/AIDS

Question 19

Routes of entry and examples of pathogens that use said route

Answer 19

Ingestion (Salmonella)
Inhalation (Mycobactrium tuberculosis)
Trauma (Clostridium tetani)
Needlestick (Staph. aureus)
Arthropod bite (Rickettsia)
Sexual (Neisseria gonorrhoeae)

Question 20

What is the most basic determinant of cell susceptibility to a pathogen

Answer 20

Presence or absence of receptor molecules used by that pathogen to bind and/or enter cells

Question 21

Important differences between intracelluar and extracellular pathogens

Answer 21

Intracelluar: don’t travel as far, are protected from some host defenses and its harder to get antimicrobial drugs to them

Extracellular: can travel farther because growth and reproduction not constrained by host cells.. More vulnerable to drugs and host defenses

Question 22

Factors affecting transmission

Answer 22

Number of microbes shed (** affected by host responses like coughing, sneezing, diarrhea)
stabiility of microbe in env (e.g spores)
infectious dose (**affected by route)
Microbial genetics (e.g. strain)

Question 23

Basic types of organism to organism transmission

Answer 23

1) Human- Human (respiratory/salivary, fecal-oral, venereal)
2) Vertebrate-Human (zoonoses)
3) Arthropod-Human or Invertebrate human

Question 24

Types of vertical transmission

Answer 24

Prenatal (placental): rubella, cytomegalovirus, syphillis, toxoplasmosis
Perinatal: gonococcal/chlamydial conjunctivits, Hep B
Postnatal: Hep B, HIV, HTLV1
Germline: retroviruses

Question 25

Carrier vs. active carrier vs. convalescent carrier vs. healthy carrier vs. incabatory carrier vs. casual/acute/transient carrier vs. chronic carrier

Answer 25

Carrier= infected individual who is a potential source of infection Active carriers have the disease Convalescnet carriers have recovered from disease Healthy carriers do not become ill (e.g. typhoid Mary) Incubatory carriers have not become ill yet Casual/acute/transient carriers harbor the pathogen for a brief time Chronic carriers harbor pathogen for a long time Incubatory c

Question 26

fomite vs vector

Answer 26

Fomites are inanimate objects that harbor pathogenic organims (e.g bedding, utensils...) Vectors are organisms that spread the pathogen from one host to another

Question 27

``` Sporadic disease vs. Endemic disease vs. Hyperendemic disease vs. Epidemic disease vs. Pandemic disease ```

Answer 27

Sporadic: occurs occasionally at irregular intervals Endemic: steady, low frequency, regular interval (e.g. common cold during the year) Hyperendemic: increase in occurence beyond endemic (e.g. common cold during winter) Epidemic: large increase in occurence beyond what was expected (e.g. H1N1) Pandemic: and epidemic in a very large population and region (e.g. HIV)

Question 28

Cell wall structure of gram positive, gram negative, mycobacteria and mycoplasm

Answer 28

Gram Positive: cytoplasmic membrane + thick peptidoglycan wall Gram Negative: cytoplasmic membrane, thin peptidoglycan, outer membrane Mycobacteria: cytoplasmic membrane, thin peptidoglycan, outer sheath of mycolic acid Mycoplasm: no cell wall

Question 29

Clinically relevant endospore forming bacteria

Answer 29

Clostridia (C. difficile, C. tetani, C. botulinum, C. perfringens) Bacillus (B. antracis)

Question 30

Phases of bacterial growth curve

Answer 30

Lag, Logarithmic, Stationary, Death

Question 31

Important AB resistant bacteria

Answer 31

MRSA (methycillin resistant Staph. aureus resistant to all beta-lactams) VRSA (vancomysin resistant Staph. aureus) VRE (vancomysin resistant entercocci)

Question 32

5 sites of infection

Answer 32

``` SSTI Respiratory GI Urogenital Sterile Sites ```

Question 33

5 potential pathogens

Answer 33

``` Virus Typical bacteria Atypical bacteria Fungi Parasites ```

Question 34

Best ways to collect a urine sample

Answer 34

Midstream is usually better than first catch (except for chlamydia) is better than catherter (AKA foley)

Question 35

Percent contamination of blood samples

Answer 35

2-5%

Question 36

5 detection methods

Answer 36

Direct: - Microscopy - Culture - Antigen - Nucleic acid Indirect: -host immune response (antibodies)

Question 37

Usefulness of Gram stain

Answer 37

- Can identify organism based on size/shape - Can see the relative number of immune cells present - NOT useful for stool samples

Question 38

Usefulness of C&S

Answer 38

- Can identify organism - Can do sensitivity testing - Can strain-type (unlike Gram stain)

Question 39

Usefulness of PCR

Answer 39

- Sensitive, specific and fast | - Cannot identify living organisms

Question 40

Usefulness of antigen tests

Answer 40

-Can detect pathogen proteins and toxins

Question 41

Usefulness of antibody testing

Answer 41

- detects chronic or latent infection - sensitive and specific - presence of infection inferred, not directly observed

Question 42

How viruses, typical bacteria, atypical bacteria, fungi and parasites are typically detected

Answer 42

``` Viruses: nucleic acid and serology Typical Bacteria: microscopy & culture Fungi: Microscopy & culture Parasites: microscopy Atypical bacteria: microscope &culture &other methods ```

Question 43

What elevated procalcitonin indicates

Answer 43

Bacteremia

Question 44

The 4 indications for urine culture

Answer 44

- complicated infection - failure to respond to Tx - Atypical symptoms - Recurrent symptoms

Question 45

How often do mixed urine infections happen?

Answer 45

Rarely! 95% chance it's contamination. 5% of the time it is a mixed infection.