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Flashcards in Microbes Deck (45):
1

General classes of organisms that can cause infectious disease

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

2

Names of unicellular and multicellular fungi

Yeast; Hyphae (mold)

3

Examples of parasites and their class

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

4

Disease associated with prions

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

5

Relative size of medically important organisms

virus < bacteria < protozoa < helminths

6

Serogroup, serotype, biotype are all synonymous with...

strain

7

Classification of bacteria is according to...

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

8

Classification of viruses is according to...

nucleic acid type and sense, presence of envelope, symmetry

9

Pathogenicity vs.Virulence

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

10

Contrast colonization and infection

??????

11

Medical examples of mutualism, commensalism and parasitism

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

12

Strict pathogens vs. opportunistic pathogens

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

13

Development of normal flora

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

14

Influences on normal flora

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

15

Benefits of normal flora

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

16

Examples of bacterial metabolites that alter their environment

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

17

Probiotics vs. Prebiotics

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)

18

Examples of immunocompromised individuals

Bone marrow transplant pts are on prophylactic antibiotics
HIV/AIDS

19

Routes of entry and examples of pathogens that use said route

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

20

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

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

21

Important differences between intracelluar and extracellular pathogens

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

22

Factors affecting transmission

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)

23

Basic types of organism to organism transmission

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

24

Types of vertical transmission

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

25

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

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

26

fomite vs vector

Fomites are inanimate objects that harbor pathogenic organims (e.g bedding, utensils...)

Vectors are organisms that spread the pathogen from one host to another

27

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

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)

28

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

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

29

Clinically relevant endospore forming bacteria

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

30

Phases of bacterial growth curve

Lag, Logarithmic, Stationary, Death

31

Important AB resistant bacteria

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

32

5 sites of infection

SSTI
Respiratory
GI
Urogenital
Sterile Sites

33

5 potential pathogens

Virus
Typical bacteria
Atypical bacteria
Fungi
Parasites

34

Best ways to collect a urine sample

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

35

Percent contamination of blood samples

2-5%

36

5 detection methods

Direct:
-Microscopy
-Culture
-Antigen
-Nucleic acid

Indirect:
-host immune response (antibodies)

37

Usefulness of Gram stain

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

38

Usefulness of C&S

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

39

Usefulness of PCR

-Sensitive, specific and fast
-Cannot identify living organisms

40

Usefulness of antigen tests

-Can detect pathogen proteins and toxins

41

Usefulness of antibody testing

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

42

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

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

43

What elevated procalcitonin indicates

Bacteremia

44

The 4 indications for urine culture

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

45

How often do mixed urine infections happen?

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