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Systemic Bacteriology Flashcards

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1
Q

what are the 4 ways you can classify microorganisms?

A
  1. appearance (shape, size, arrangement, cell wall - gram+/-)
  2. growth requirements
  3. enzyme/metabolic tests
    4.molecular tests
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2
Q

what types of appearance can help classify microorganisms?

A

-shape
-size
-arrangement
-Cell Wall i.e. gram +/-

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3
Q

what types of growth requirements can help classify microorganisms?

A

-aerobic/anaerobic
-requirement for blood products (serum proteins)
- sensitivity to agents (NaCl, Bile, K tellurite)

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4
Q

what types of enzyme/metabolic tests can help classify microorganisms?

A

-coagulase test
-catalase test
-haemolysis (streptococci only)
-biochemical profiling (e.g. carbs metabolised)

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5
Q

what types of molecular tests can help classify microorganisms?

A

-immunological tests (antigentesting) e.g. immunoassay, ELISA, agglutination, western blot
-DNA sequencing (qPCR or 16sRNA)
-protein profiling e.g.MALDI TOF

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6
Q

what are some of the different appearances you see when looking in microscope?

A

-pure culture or polymorph (pure sample or lots of different organisms)
-shape, size, grouping (clumps/chains)
-structures
-staining (Gram, fleurochromes)

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7
Q

what are the common shapes of bacterial cells?

A
  1. cocci (spheres)
  2. Bacilli (rods)
  3. Spirichaetes
  4. Spirillium
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8
Q

what is streptococcus?

A

when there’s a division of cocci in one plane -> forming chains

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9
Q

what is staphyloccus shape?

A

division of cocci in 3 planes to produce clumps

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10
Q

what is diplococci?

A

individual or attached (2) cocci

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11
Q

describe the shape of bacilli?

A

rod-shaped bacteria
= elongation in 1 plane
=parallel cell division
=cell poles

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12
Q

when are chains of bacilli more common?

A

in gram +
(in both but predominantly gram + and gram -)

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13
Q

what is fusiform?

A

long slender rods & species including emerging pathogens in GI tract, mouth, head & neck

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14
Q

what are curved rods?

A

-slightly curved rods
-Gram -
example = vibrio cholerae

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15
Q

what are 2 types of spiral shaped?

A

rigid spiral shape = spirillium

flexible spiral bacterium = spirochaetes (more coiled)

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16
Q

what are spores?

A

inert survival structures (environmental mechanism to cope with starvation)
-they’re very small and can easily spread
*resistant to physical & chemical challenge

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17
Q

what is structure of spore?

A

-very small
-has chromosomes
-spore coat
-metabolically inert

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18
Q

what is Gram stain?

A

retention of crystal violet & iodine complex by gram -positive bacteria
= it’s a simple method that distinguishes between 2 major classes of pathogenic bacteria according to cell wall structure

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19
Q

which type of cell wall retains dye and why?

A

gram-positive retains dye because has peptidoglycan on outside of cell wall (only plasma membrane then thick layer of peptidoglycan)
whereas gram negative has peptidoglycan within wall (has plasma membrane then thin layer of petpidoglycan then surface membrane)

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20
Q

what is the procedure of a gram stain?

A
  1. prepare a heat fixed film of bacteria on a glass slide
  2. stain with crystal violet for 1 min and rinse with water
  3. treat with Gram’s iodine for 1 min & rinse with water
  4. briefly decolourize with acetone & ethanol (a few seconds)
  5. counter stain with basic fuchsin or safranin (pink dye) for 1 min and rinse with water
  6. blot dry and view under oil immersion
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21
Q

what are the limitations of gram staining?

A

not all microorganisms stain well:
1. mycobacterium tuberculosis (lipid rich/waxy cell so doesn’t take up stain)
2. Treponema pallidum (spirochaete organism that causes syphilis)

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22
Q

what are obligate aeorobes?

A
  • bacteria require oxygen (helps classify them)
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23
Q

what are obligate anaerobes?

A

-bacteria killed by oxygen (helps classify them)

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24
Q

what are facultative anaerobes?

A

bacteria that tolerate oxygen

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25
Q

what are aerobic bacteria?

A

they are bacteria that grow in oxygen/air

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26
Q

what are capnophillic bacteria?

A

prefer high CO2 levels

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27
Q

what is selective media?

A

presence of specific substance permits the growth of one organism over another

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28
Q

what are 2 examples of selective media?

A
  1. mannitol salt agar (MSS) = 7.5% salt allows preferential isolation of straphylococci
  2. salmonella-shigella (SS) = bile salts inhibit coliforms
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29
Q

what is differential media?

A

incorporation of chemicals produces visable changes in colonies that facilitate identification (differentiation)

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30
Q

what are 2 examples of differential media?

A
  1. MacConkey agar = allows identification of Enetrobacteriaceae
  2. eosin & methylene blue = allows identification of lactose fermenters e.g. E.coli
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31
Q

what can you use to know what type of bacteria it is?

A
  1. immediate examination
  2. sometimes structures under microscope (like spores and gram-/+)
  3. aerobic or anaerobic
  4. what it grows on (media)
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32
Q

what is haemolysis?

A

destruction of red blood cells

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33
Q

what is beta hemolysis?

A

destruction of red blood cells, erythrocytes suspended in media is being destroyed so tells you toxin being produced and gives indication that bacteria does a lot of damage

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34
Q

what is alpha hemolysis?

A

damage to outer surface of erythrocytes so some iron accessed so see changes in colour to green ish (harder to see on media) - gives indication of degree of damage done by bacteria

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35
Q

what is gamma hemolysis?

A

no hemolysis -> normal
-gives indication of degree of damage done by bacteria

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36
Q

what is metabolic profiling?

A

-a type of biochemical characterisation that is about what the bacteria is able to do

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37
Q

what are some examples of metabolic profiling?

A

-utilisation of carbon sources(helpful in understanding how they obtain energy and build essential molecules through metabolic processes)
-utilisation of amino acids (help understand protein synthesis, energy production and lots more)
-exo-enzyme production (catalase, coagulase, hydrolysis of lipis, urease) - organism’s ability to break down complex substrates in its environment

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38
Q

what is process of identification now?

A

you take your media then make into solution then put into machine that makes up a profile

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39
Q

what are serological tests?

A
  • another method to identify bacteria by use of antibody/antigen interaction (specificity)
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40
Q

what are examples of serological tests?

A

-host immune response to antigen by the raising antibodies
-antibodies specific to microbe/virus or single component (monoclonal)
-detect presence of IgM antibiotics to virus
-demonstrate in vitro by agglutination reaction
-rapid detection of viruses e.g. lateral flow

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41
Q

what is agglutination reaction?

A

type of serological test where you add antibody (blood cell) and mix with antigen and if antigen-antibody complex formed then you know what it is

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42
Q

what is qPCR?

A
  • PCR for virus
    -same process (heat to denature, anneal of primers to template, extension of primers and replication)
    -gives another level of identification by turning weak/poor sample into significant signal
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43
Q

what is 16sRNA?

A

RNA component of haloenzyme, a molecular clock & fingerprint species
-something that’s required (it’s different depending on type - so you can amplify sequence to help see what type)

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44
Q

what does MALDI-TOF stand for?

A

Matric Assisted Laser Desorption Ionization Time-Of-Flight

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45
Q

why is MALDI-TOF good?

A

powerful (99% correct)
rapid (6 minutes)
precise (species, sub species, sometimes strain level)
cost effective (17-32% cost of conventional techniques)

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46
Q

what does MALDI-TOF do?

A

= powerful analytical technique used for the identification of biomolecules, particularly proteins and peptides, widely employed in microbiology for the rapid and accurate identification of microorganisms, including bacteria, fungi, and viruses

  • Generates a series of ions from a sample dependent on its constituents
  • mass analyser = Separates the ions according to mass & charge
  • detection device = Detects the spectrum of proteins released from a sample
  • Results in characteristic signature
    • Require a reference
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47
Q

what is microbiome?

A

community, or it’s associated genetic material, associated with host during health
-includes potential pathogens

48
Q

how does microbiome help protection?

A

→Excludes pathogens or controls/competes

→Supports host, digestion & immune response

49
Q

what is pathogenesis?

A

process by which an infection leads to disease
-> endogenous bacteria shifting to parasitic lifestyle (requires adpatation/change)

50
Q

what are endogenous and exogenous bacteria?

A

endogenous = always present, part of normal internal ecosystem (bacterial flora)

exogenous = not normal, arise from superficial tissues

51
Q

what is a pathogen?

A

→a harmful organism that produces a pathology

→Virulence, & virulence factors

52
Q

what is commensal/nutualism/symbiosis?

A

→an organism that is part of the normal flora

→often mutualistic relationship

→endogenous
(symbiotic relationship)

53
Q

what is an opportunistic pathogen?

A

an organism that causes infection when opportunity/change in natural immunity arises
e.g. an immunocompromised individual
(can be become pathogenic and can also colonise normally)

54
Q

what is a contaminant?

A

an organism that is growing in culture by accident

55
Q

what is virulence?

A

measure of capacity of a microbe to cause damage to the host

56
Q

what is the name of the model system that virulence is usually determines in?

A

mouse respiratory model
- shows lethal dose & infectious dose

57
Q

what are some examples of protozoan diseases of man and how many people do they affect?

A
  • malaria = 3.3 billion
  • GI infections
  • toxoplasma = 2 billion (it’s a pathogen that changes behaviour of host)
  • leishmaniasis = 150 million
58
Q

what are some examples of fungal infections?

A

candida spp. = yeast budding = from skin infection to candidaemia (candida species in blood)

aspergillus spp. = moulds = infections in immunocomprimised

59
Q

what do aerobic gram negative cocci appear as on gram film?

A

neisseria mengitidis and neisseria gonorrhea often appear as diplococci (in pairs)

  • not always though
60
Q

what are aerobic gram negative cocci?

A

A group of gram-negative bacteria
(i think i only need to know neisseria meningitidis and neisseria gonorhoea)

61
Q

what are the 2 pathogenic aerobic gram negative cocci?

A
  1. Neisseria meningitidis = commonest cause of bacterial meningitis
  2. Neisseria gonorrhoeae = causes gonorrhoea, a sexually transmitted infection
62
Q

what is the most common bacteria?

A

e.coli = escherichia coli

63
Q

what is enterobacteriaceae?

A

a global population of gram negative bacteria in GI tract
=many are part of normal bowel flora

64
Q

what is enterobacteriac?

A

a sub group of enterobacteriaceae (which is gram - population in GI tract)
enterobacteriaceae = has big range (some good, some bad) , e.coli is example

65
Q

what is coliform?

A

term used to describe species of gram negative bacilli that look like e.coli on gram film and when cultured on blood agar (e.coli is a species of colifrom)

66
Q

how are e.coli differentiated from each other?

A

-Biochemical reactions
-Antigenic structure of cell wall (serotyping)
-O antigens (cell wall) and H antigen (flagella)

67
Q

How do enterobacteriaceae grow best?

A

aerobically but they can also grow anaerobically

68
Q

what is the first line antibiotic used for treatment of infections caused by coliforms?

A

gentamicin

69
Q

what happens when coliform gets into normally sterile site?

A

causes serious infection
e.g. urinary tract infection, peritonitis, biliary tract infection

70
Q

why do patients with coliform sepsis become unwell very quickly?

A

because of the endotoxin released from gram negative cell wall when bacteria die

71
Q

what do endotoxins do?

A

bind to receptors on macrophages, B cells & other cells that stimulate release of acute phase cytokines

72
Q

what are endotoxins?

A

atoxinpresent inside agram -ve bacterial cell wall that is released when bacteriadisintegrates

73
Q

what is structure of outer membrane of gram negative bacteria?

A
  • Assymetric membrane
  • Lipopolysaccharides (LPS) (endotoxin is a type of LPS)
  • Peptidoglycan
  • Lipoproteins
74
Q

what is sepsis?

A

a host immune response to severe infection mediated by LPS/endotoxin via host immune system

75
Q

what are some symptoms of sepsis?

A
  • Small blood vessels become “leaky” and lose fluid into the tissues
  • Lower blood volume requires heart to work harder to maintain oxygenation of tissues (↑HR)
  • Poor tissue oxygen perfusion mean blood supply to less essential organs (skin, kidneys, liver) is shut down to try to maintain blood supply to brain
  • Blood clotting system is activated causing blood clotting in tiny blood vessels→ uses up all clotting factors→ increased risk of haemorrhage

-fever production

76
Q

what is normal body temp?

A

37 degrees C

77
Q

what is fever temp?

A

above 38 degrees C

78
Q

what temp do most human pathogens grow best? what happens when temp increased?

A

37 degrees C
- when temp increased, growth starts to slow

79
Q

describe fever production?

A
  1. antigen or endotoxins interact with macrophages
  2. macrophages release cytokines into blood stream
  3. cytokines travel to anterior hypothalamus (cytokines also stimulate adverse effects of sepsis)
  4. prostoglandin E is released which increases bodies thermal set point
  5. body now percieves as cold and starts to shiver
  6. increased survival from infection
80
Q

what are the stages of sepsis?

A

infection -> sepsis -> severe sepsis -> septic shock

-very quickly deteriates (tops 4 hours)

81
Q

why does body produce fever?

A

it’s an adaptive response and is considered benificial in fighting infection

82
Q

how can a fever be harmful in young children?

A

could cause febrile convulsions in young children

83
Q

what are key examples of gram positive pathogens & their common themes?

A

streptococcus = pneumonia, GAS, oral streps

Enterococcus =Enteric infections

Staphylococcus =Nosocomial & community = Skin infections & biofilms

Clostridia (Clostridioides) = Anaerobic bacilli

84
Q

what is the most significant pathogenic streptococci?

A

group A streptococcus - leads to numerous types of diseases

85
Q

what are some examples of diseases resulting from Group A streptococcus?

A
  • Streptococcus pyogenes (strep throat & other infections)
  • ß-haemolytic (complete lysis (destruction of cell membrane) of red blood cells)
  • Streptococcal sore throat (Scarlet fever)
  • Invasive diseases e.g. necrotising fasciitis
  • Puerperal sepsis (infection of pregnant & post natal women)

=can lead to rheumatic fever/invasive disease

86
Q

what is pneumonia?

A

An acute inflammation of the lungs, often caused by inhaled pneumococci of the species Streptococcus pneumoniae. The alveoli and bronchiles of the lung become plugged with a fibrous exudate.

87
Q

what does streptococcus pneumoniae cause?

A

pneumonia & also severe forms of meningitis

88
Q

what is streptococcus pneumoniae?

A

gram positive alpha-haemolytic cocci (short chains or pairs)
- part of normal upper respiratory tract flora in many people

89
Q

can vaccines tackle streptococcus pneumoniae?

A

there are 90+ different types, there are vaccines for the 23 most common types

=majority of UK strains are sensitive to penicillin

90
Q

what is enterococci?

A

the most important group of non-haemolytic streptococci (but enterococci & streptococci are different things)(gram +ve)

=part of normal bowel flora

91
Q

how harmful is enterococcus?

A

not particularly pathogenic but cause problems if they get into normally sterile site
- common cause of urinary tract infection (UTI)

92
Q

are vaccines effective on enterococci?

A
  • Most strains of E. faecalis are sensitive to amoxicillin (but not to penicillin)
  • Some very antibiotic-resistant strains of E. faecium “VRE” (vancomycin resistant enterococci) can cause “outbreaks” of infections in hospital
93
Q

what is appearance of straphylococcus?

A

often arranged in clusters or clumps like a bunch of grapes

94
Q

what is straphylococcus?

A
  • gram positive
    -non motile
    -aerobe & facultative aerobe
  • catalase positive (usuallly)
  • oxidase negative
95
Q

what are types of staphylococci?

A

s. aerus
s. epidermidis
e. saprophiticus

96
Q

what are clostridiodes?

A
  • spores central to spread
  • have ability to avoid antimicrobials
  • gram positive anaerobic bacilli
  • part of normal bowel flora (human & animal) - found in faeces and soil
    -produce spores that survive outside body for many months
97
Q

how does clostridiodes cause severe tissue damage?

A

produce exotoxins

98
Q

what are 3 types of clostridiodes and what do they cause?

A
  • Clostridioides difficile– causes antibiotic-associated diarrhoea, esp. in the elderly
  • Clostridium perfringens – causes “gas” gangerene, a severe soft tissue infection following contamination of a wound
  • Clostridium tetani– causes tetanus, a usually fatal paralytic illness
99
Q

what colour does gram +ve stain?

A

purple

100
Q

what colour does gram -ve stain?

A

pink

101
Q

what are exotoxins?

A

usually gram +ve bacteria
- produced inside cell and exported from it

102
Q

what does microaerophillic mean?

A

reduced oxygen & increased carbon dioxide

103
Q

what is classification of streptococcus?

A
  • gram +ve
  • aerobic
  • cocci chains
  • alpha haemolytic = strep pneumoniae & strep viridans
  • beta haemolytic = Group A & B strep
  • non (gamma) haemolytic = enterococcus
104
Q

what are
a) strep pneumoniae?
b) strep viridans?

A

they’re both alpha haemolytic type of streptococcus
a) pneumonia & meningitis
b) endocarditis

105
Q

what are group A & B strep?

A

they’re beta haemolysis streptococcus
a) group A = throat & skin infection
b)group B = neonatal meningitis

106
Q

what is enterococcus?

A

non- haemolytic streptococcus that is normal gut commensal but can cause UTI’s
(also gram +ve, aerobic & cocci chains like streptococcus)

107
Q

what is staphylococcus?

A
  • gram +ve
  • cocci clusters
  • coagulase +ve = golden colour = staph aerus
  • coagulase -ve = white = staph epidermis
108
Q

what is staph epidermis?

A

coagulase -ve staphylococcus
= normal skin commensal
= can cause IV line infections

109
Q

what is staph aerus and what antibiotic is used to treat it?

A

coagulase +ve staphylococcus
= wound & skin infection
= common cause of bacteraemia (bacteria in blood)

-> flucloxacillin treats

110
Q

what is campylobacter identification factors? (like gram, shape, etc)

A

gram -ve
- microaerophillic
- small curved bacilli

111
Q

what is nesseria gonorrhea and nesseria menigitidus?

A
  • important gram -ve
  • cocci
  • aerobic
    neisseria gonorrhea = gonorrhea
    neisseria mengitidus = menigitus
112
Q

what are some identification/classification factors of coliforms?

A
  • aerobic
  • gram -ve
  • large bacilli
    then divides to gut commensals and gut pathogens
113
Q

what are gut commensal coliforms?

A
  • escherichia coli (UTI)
  • klebsiella sp (wound infection)
  • proteus sp (wound infection)
114
Q

what are gut pathogen coliforms? (examples)

A
  • salmonella spp
  • shigella sp
  • e.coli 0157
115
Q

what is clostridium identification factors?

A
  • gram +ve
  • bacilli
  • anaerobic
  • produce exotoxin

cl tetani (tetanus)
cl perfringes (GAS gangrene)
cl difficile (antibiotic associated colitis)

116
Q

what is first line antibiotic of infection for anaerobes?

A

metranidazole

Microbiology (6 decks)

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