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Microbiology > Unit 1: Bacterial Cultivation > Flashcards

Unit 1: Bacterial Cultivation Flashcards

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Biology 101 flashcards
1
Q

Media containing known quantities of each component

A

Defined Media

Defined carbon and nitrogen sources

Can eliminate variability between experiments

Usually has narrower range of growth than complex media (not very helpful if you don’t know what you have)

Usually more expensive than complex media

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2
Q

___________ media contains components not chemical defined

A

Complex media (ie yeast extract)

No exact formula

Usually has a broader range of growth than defined media

Usually less expensive than defined media

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3
Q

Complex media used for growing fungi

A

Potato extract agar - bacteria won’t grow on it

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4
Q

What is enriched media?

A

Complex media + growth factor(s)

Used for growing fastidious organisms (fussy or picky eaters who must have a certain factor to grow)

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5
Q

What is selective media?

A

Select against unwanted organisms

Growth of unwanted organisms is inhibited by some components (ex: an antibiotic)

Only certain organisms are able to grow

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6
Q

What is differential media?

A

Differentiates between organisms

Contains components that result in a visible change (color of colony, formation of precipitate etc)

Does not select for specific organisms or specifically inhibit growth

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7
Q

What is MacConkey agar and how is it used?

A 
Contains:
• Peptone
• *Lactose*
• Bile salts - inhibit Gram(+)
• Crystal violet - inhibit Gram(+)
• Neutral red - pH indicator

Differential AND selective

Used in enteric infections

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8
Q

What are fastidious organisms?

A

Can be high maintenance, picky eaters, and are often called “fussy” - need a complex diet

Difficult to grow in vitro

Requires addition of growth factors (enriched media required)

Examples: Haemophilus and Neisseria - require hemin and NAD for growth —> will not grow on blood agar plates, only on chocolate agar (lysed red blood cells)

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9
Q

Most pathogenic bacteria are ____________

A

Mesophiles - can live at ranges ~12-42˚C but optimized for 30-37˚C

Why? B/c that’s our body temp!

Lower temps: Psychrotrophs and Psychrophiles
High temps: Thermophiles and Hyperthermophiles

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10
Q

Different points on the growth rate curve for environmental factors

A

MIN = minimum value of parameter that supports growth of the microbe

OPT (peak) = value of parameter that supports optimum growth of the microbe

MAX = maximum value of parameter that supports growth of the microbe (NOTE - MAX ≠ maximum growth)

Different parameters affecting growth: temp, pH, O2, nutrients)

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11
Q

Low temperature challenges for bacteria

A

Loss of enzyme activity

Decrease in membrane fluidity

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12
Q

High temperature challenges for bacteria

A

Denaturing of structural proteins

Denaturing of enzymes

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13
Q

Diagnostic media for human pathogens usually at what pH?

A

7.0

Most pathogens affecting humans are neutrophiles - again, because they need to thrive at human body pH

Exceptions:
Acidophiles such as lactobacillus, coxiella burnetii
Alkaliphiles such as bacillus app., vibrio cholerae

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14
Q

What is the meaning of obligate?

A

Without an alternative
Limited to a narrow range of a given environmental parameter

Ex: Obligate aerobes require O2

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15
Q

What makes something a facultative species?

A

Has alternatives, capable of surviving in different conditions

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16
Q

Classification of microbes based upon oxygen requirement

A

Obligate/strict aerobes require oxygen, have enzymes for reactive O2 species (ROS)

Microaerophile require O2 but at lower levels, have ROS

Facultative aerobe/anaerobes do not require O2 but will use it if available, have ROS

Aerotolerant anaerobes neither require nor utilize O2, but do have ROS

Obligate/strict anaerobes - O2 is toxic, do not have ROS enzymes

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17
Q

Importance of ROS enzymes

A

Reactions with O2 often create reactive oxygen species (ROS) that can be toxic to cells. Without enzymes to counteract ROS, they can be lethal.

Examples of ROS enzymes: superoxide dismutase (SOD), catalase, perioxidase

Obligate anaerobes do not have ROS enzymes, so O2 is toxic

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18
Q

Growth of different microbes in liquid culture, based on O2 requirements

A

Obligate aerobes - growth will be at the top of the test tube

Obligate anaerobes - growth will be at the bottom of the test tube

Facultative anaerobes - growth will be throughout the test tube, with slight clustering at the top

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19
Q

Microbes that require high CO2 levels (3-5%) are classified as ….

A

Capnophiles

Examples - Neisseria, Haemophilus, Helicobacter, Capnocytophaga

Require special housing - candle jar, CO2 packet/incubator, automated systems

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20
Q

Microbes that require high salt

A

Halophiles

Obligate halophiles
• Extreme (15-30%) - Archaea
• Moderate (3-15%) - pseudomonas, staph aureus - b/c on the skin (think sweat)
• Slight (0.5-3%)

Facultative/halotolerant halophiles also exist

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21
Q

Microbes that require high osmolarity/sugar

A

Osmophiles

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22
Q

Microbes that have developed resistance to desiccation

A

Bacillus and Clostridium via spore formation

Mycobacterium via cell wall modification (mycolic acids)

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23
Q

The new gold standard for establishing the cause of an infection

A

PCR - invented 1983 by Kary Melli’s

Identifies cause of a disease using a single copy of DNA or RNA from a blood/tissue sample

Potential problems due to normal flora (microbiota)

24
Q

______________ involves a transient or permanently established microbial growth, but with NO interference with normal body functions

A

Colonization

25
Q

______________ involves a transient or permanently established microbial growth, but MAY manifest disease

A

Infection

26
Q

Abnormal condition of body structure(s) and function(s)

A

Disease

Occurs when interaction leads to pathogenesis
Results in damage to host
Can occur without presence of microbe

27
Q

Examples of toxins from microbes causing physiological changes

A

Intoxication

Clostridia and Staph species - toxins ingested from contaminated sources (food, Botox injections, drinks)

28
Q

Objective evidence of disease as noted by an observer

A

Signs

Changes due to disease, observed by a clinician

29
Q

The subjective evidence of disease as sensed by the patient

A

Symptoms

Changes due to disease, experienced by the patient

30
Q

_________ is sensed and observed, and therefore exists as both a sign and a symptom

A

Fever

31
Q

The five stages of disease

A 
Incubation period
Prodromal phase
Invasive phase (most severe signs and symptoms)
Decline phase
Convalescence period

Severity and duration of disease and each stage varies with pathogen, virulence, and host susceptibility

32
Q

Characteristics of the Incubation (preclinical) stage

A

Pathogen has entered the body
No signs or symptoms
Innate immune system has not been activated
Pathogen must be an infectious dose (inoculum, or number of microbes required for disease)
NOT contagious!!!

33
Q

Characteristics of Prodromal (warning) stage

A

Appearance of signs and symptoms (non specific - ie dry cough and slight fever)
Activation of the innate immune system
Pathogen numbers increase
Easily transmitted even before person realizes they are sick (Asymptomatic carriers)

34
Q

Characteristics of Acute stage

A

Aka Clinical Illness

Most severe time of illness
Characteristic signs/symptoms
Acquired immune system has been activated
Pathogen numbers are stationary
Communicable diseases are easily transmitted

35
Q

Differentiating between Acute and Chronic Disease

A

Acute: signs and symptoms develop rapidly, peak and decline

Chronic: Signs and symptoms persist, slow to move to decline phase

36
Q

Characteristics of the Decline stage

A

Illness still apparent but signs/symptoms dwindle
Immune system activity is reduced (antibodies formed)
Pathogen is cleared from host
Can be contagious if individual becomes a carrier

37
Q

Characteristics of Convalescent stage

A 
Patient returning to full health
Signs/symptoms end
No immune system activity to pathogen
Pathogen cleared from host 
Not contagious (no pathogen)
38
Q

What are opportunistic pathogens

A

Organisms can be part of the patient’s normal flora
Do not produce disease in normal setting
Establish disease when introduced to unprotected site (ie blood, tissues), via injury (burns) or if immune system is compromised.

39
Q

What are virulent pathogens

A

Strict pathogens - always associated with disease

Signs/symptoms due to host inflammatory response or direct damage to or loss of tissues/organs

40
Q

How do bacterial metabolites function as mechanisms of bacterial virulence?

A

Acids, gases, or other byproducts of metabolism formed during bacterial growth serve to directly damage host tissues

Ex - Streptococcus mutants produces lactic acid which results in dental caries

41
Q

How do Invasins function as mechanisms of bacterial virulence?

A

Aka “Spreading factors”
Proteins or enzymes that act locally to damage host cells
Affect tissue matrices and intracellular spaces (“soften”)
• Allows for the spread and replication of the bacterium
• Host cell/tissue damage can result in pathological characteristics
• Examples: Hyaluronidase depolymerizes hyaluronic acid (connective tissue); Collagenase breaks down collagen; Neuraminidase degrades neuraminidase acid (intracellular glue); Streptokinase and Staphylokinase both act as fibrinolysins (break down blood clots)

42
Q

How do adhesins work as mechanisms of bacterial virulence

A

Bind pathogens to receptors on host cells and tissues
Most bind to carbohydrate moieties (glycoproteins)
Types of adhesins:
• Glycocalyx material - capsule and slime layers (create biofilms)
• Fimbriae and pili - attach to specific host molecules (ie - Neisseria gonorrhoeae attaches to conjunctiva)
• Afimbrial adhesins - proteins associated with cell envelope

43
Q

How do toxins function as mechanisms of bacterial virulence?

A

Toxins resemble enzymes - proteins with high activity and specificity, are heat labile

44
Q

What are exotoxins?

A

Found in both gram (-) and gram (+) cells
Proteins that are toxic to cells, usually direct in action
Secreted into the extracellular fluid, or associated with the bacterial cell surface
Bind host cell receptors

45
Q

What are enterotoxins?

A

Same as exotoxins but cause GI signs and symptoms (ie vomiting, nausea, diarrhea)

Example - Rotavirus NSP4 - causes infantile diarrhea

46
Q

The 2 major categories of exo/enterotoxins

A 
A-B Exotoxins
Two domains or subunits:
• A - enzymatic component, ATTACKS cell
• B - BINDS toxin to host receptor
After binding (B), A is transported into cell
Can form toxoids (inactivated toxins)
47
Q

Examples of A-B exotoxins

A

Corynebacterium diptheriae stops host cell protein synthesis

Clostridium botulinum prevents release of ACh at synapses —> flaccid paralysis

Clostridium tetani prevents inhibitory neurotransmitter release —> spastic paralysis

48
Q

What are superantigens

A

Toxins that activate up to 40% T cells in the absence of antigen, resulting in massive release of cytokines

49
Q

Examples of membrane active exotoxins

A

Proteases - destroy protein in host cell (cell membrane)

Lipases - destroy lipids in cell membrane

Hemolysins - form pores in RBCs and phagocytes

50
Q

What are endotoxins?

A

LPS of gram (-) organisms
Not very toxic until released
O antigen - polysaccharide that is immunogenicity
Lipid A component - toxicity

51
Q

Other examples of virulence mechanisms

A

1) Spread from primary site of infection - cytotoxic effects span larger area than focus of infection
2) Encapsulation - blocks phagocytosis (ex - S. pneumo)
3) Inactivation of antibody - S. pneumo secretes IgA degrading proteases, S. aureus binds to Fc region of IgG
4) Intracellular growth and escape detection - M. tuberculosis is a facultative intracellular bacterium

52
Q

What is evasion by antigenic variation?

A

Ability of microbe to change epitomes, present new antigens to immune system, or initiate new disease cycle to increase virulence

53
Q

Accumulation of genetic mutations —> alterations in protein products and variability in population

A

Antigenic Drift

Forms antigenically distinct strains

Example: E.coli O157:H7 - over 157 different O antigens
Influenza virus - minor mutations in protein spikes, evelope

54
Q

Reassortment of viral genome in a cell infected by 2 or more strains

A

Antigenic shift

Example: Influenza A - combination of two or more strains can produce a new subtype of virus —> pandemic

55
Q

Genetic conversion/shuffling due to recombination within a group of genes

A

Antigenic switching

Results in new surface antigen, but no change in biological function

Examples: Pili, fimbriae, surface glycoproteins
Pili of N.gonnorhoeae always present but antigenic structure changes

Microbiology (6 decks)

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