bacteriology basics

Question 1

facultative anaerobe

Answer 1

can grow in presence of O2 and it’s absence

Question 2

Virulence

Answer 2

the degree of pathogenicity as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host

Question 3

Antigenic Switching

Answer 3

The altering of a microorganism’s surface antigens through genetic rearrangement, to elude detection by the host’s immune system

Question 4

Virulence factors

Answer 4

• capsule
• protein A
• enzymes (catalase, coagulase)
• hemolysins
• toxins

Question 5

spore forming bacteria

Answer 5

gram + rods ONLY!
-cell undergoes structural and metabolic changes to increase change of survival by forming then releasing endospores (parent cell lyses)

Question 6

spore (endospore)

Answer 6

contains copy of DNA, reduced metabolic activity, impermeable envelope (does not divide)

Question 7

2 types of endospore forming bacteria

Answer 7

• bacillis antracis (anthrax)

- clodstridium tetani (tetanus)

Question 8

Clinical signs of anaerobic infection

Answer 8

Abscess, necrosis of tissue, inflammation, cellulitis, fasciitis, colitis, diarrhea,

Question 9

Common aerobic infections

Answer 9

All Clostridiums

Question 10

How to diagnose anaerobic infection

Answer 10

Anaerobic culture on blood culture, clinical presentation, Stool sample

Question 11

clinical usefulness of bacteria subtyping

Answer 11

• Critical for understanding and tracking outbreaks.
• Allows for quicker treatment
• Example of subtyping: E. coli 0157 is a subtype E. coli

Question 12

Normal Flora

Answer 12

• bacteria typically found at various anatomical sites in the body, generally do not cause infection, varies by site, age, sex, diet, nutrition, site, weaning, eruption of teeth, onset/cessation of ovarian functions, etc.
• Synthesize vitamines, outcompete pathogens, aid in immunity

Question 13

normal flora in skin

Answer 13

• staph. epidermidis
• staph. aureus
• strep. pneumoniae
• strep. pyogenes
• corynebacteria
• mycobacteria

Question 14

normal flora in mouth/UR tract

Answer 14

-mouth: Streptococci, lactobacilli, staphylococci, corynebacteria, with great number of
anaerobic bacteria

-upper respiratory tract: sinuses sterile, nares heavily colonized with coagulase-negative
staphylococci & corynebacteria (carrier site of staph. aureus),

Question 15

normal flora in GI tract and rectum

Answer 15

• stomach: lactobacilli, helicobacter
• small intestine: enterococci, lactobacilli

-large intestine: enterobacteria, enterococcus faecalis, bacteroides, bifidobacterium,
eubacterium, peptococcus, peptostreptococcus, ruminococcus, clostridia, lactobacilli

Question 16

normal flora in genitelia

Answer 16

• anterior urethra: coagulase-negative staphylococci, enterococcus, viridans
• GI bacteria & corynebacteria

-vagina: corynebacteria, staphylococci, streptococci, E. coli, and lactobacilli (lactobacilli
produce lactic acid, low pH inhibits infection by pathogenic bacteria & yeast)

Question 17

normal flora in eye

Answer 17

-conj: staph epidermidis, staph A, Aerobic cornybacteria, Strep penumoniae, tears have lysozymes that keep populations in check

Question 18

normal flora in urinary bladder

Answer 18

-sterile normally (but can be contaminated -> staph, enterococcus, viridians strep, GI bacteria and corynebacteria)

Question 19

endotoxins

Answer 19

• lipopolysaccharides toxin produced by Gram Negative bacteria
• these toxins are generally cell bound and released only when the cell lyses.
• weakly toxic
• cause “septic shock”
• common bacteria: E. coli, Shigella, Salmonella, Neisserias, Yersinia Pestis

Question 20

exotoxins

Answer 20

• (protein) Toxins that are released extracellularly as the organism grows
• may travel from a focus of infection to distant part of the body and cause damage
• from gram + or -
• highly toxic

Question 21

virulence

Answer 21

• similar to pathogenicity (but quantifiable)
• these factors are characteristic of a bacterium that enhance its pathogenicity (properties that enable a microorg to establish self and replicate within host cell)
• how many organisms are required to cause disease in 50% of those exposed to pathogen

Question 22

pathogenicity

Answer 22

bacterium’s ability to establish itself and replicate on or within a specific host, causing disease

Question 23

infectious dose

Answer 23

Number of microorganisms required to cause infection in the hosts

Question 24

lethal dose

Answer 24

Number of microorganisms required to kill the host

Question 25

transmissibility

Answer 25

Droplets/airborne, direct physical contact, indirect physical contact, fecal-oral (common in peds)

Question 26

adherence to host cells

Answer 26

• Ligands on the bacteria bind with receptors on the host cell, there are two types of adherence:
• Non-specific adherence: attractive forces between cells allow interaction (hydrophilic/hydrophobic, electrostatic)
• Specific adherence: interaction between complementary surface molecules

Question 27

invasion of host cells and tissues

Answer 27

-invasins (proteins released by bact cells) can damage host cells and/or assist in growth and transmission of the bacteria; similar to exotoxins but generally don’t spread as far or produce cytotoxic effects

Question 28

ability to evade the host immune system

Answer 28

Bacteria can evade the host immune system by coating/covering itself with host proteins such as fibrin and Ig, mimicking host cells–thus not triggering the immune response.

Question 29

toxigenicity (endo/exotoxins)

Answer 29

Endotoxins: endotoxins are part of the outer membrane of the cell wall of Gram-negative bacteria; are released when the cell disintegrates. Also known as lipopolysaccharide (LPS).

-Exotoxins: toxin released by a living bacterial cell into the environment/area. Can impact/effect areas beyond where bacterial growth is located/where toxin was released.