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Microbiology 1 > Microbiology 2- Bacterial Diseases > Flashcards

Microbiology 2- Bacterial Diseases Flashcards

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1
Q

What are the sources and roots of human bacterial infection

A

Intrinsic
Extrinsic
Mythical- toilet seats, space, cold- misconceptions

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2
Q

What are the sources of intrinsic infection

A 
Non-sterile sites in the body:
Nasal cavity & sinuses
Upper Respiratory tract
Stomach
Skin
Mouth
Small
Intestine/biliary tract
Large intestine
Lower genital tract (vagina)
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3
Q

Which parts of the body are usually sterile

A

Stomach and small intestine- due to stomach acid.

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4
Q

List some of the bacteria found in the Nasal cavity and sinuses (Upper Respiratory Tract)

A

Staphylococcus spp.

S. pneumoniae

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5
Q

List some of the bacteria found on the skin

A

Staphylococcus epidermidis

Staphylococcus aureus

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6
Q

List some of the bacteria found in the mouth

A

Streptococcus spp

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7
Q

List some of the bacteria found in the small intestine/bilary tract

A

Escherichia coli

Bacteroides ap.

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8
Q

List some of the bacteria found in the large intestine

A

Enterococci
Strep group B
Anaerobes

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9
Q

List some of the bacteria found in the lower genital tract (vagina)

A

Lactobacillus

Strep group B

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10
Q

What are the two routes of infection (portals of entry)

A

Expected- e.g. normal (harmless) microbiota entering via an expected route
(newborn infant and maternal microbiota)
Unexpected- e.g. normal (harmless) microbiota entering unusual site OR
pathogenic microbiota entering any site

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11
Q

What is the portal of entry for pathogens of the upper respiratory tract

A

Mouth and nose

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12
Q

What are the characteristics of the pathogens that target the upper respiratory tract

A

Usually extrinsically-acquired from other people as respiratory tract droplets or airborne
Hand transmission can act as intermediate

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13
Q

List some of the bacterial diseases of the upper respiratory tract

A

Streptococcus spp (dental bacteria)
Streptococcus pneumoniae
Streptococcus pyogenes
Neisseria meningitidis

Staphylococcus aureus
(MSSA and MRSA

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14
Q

What is MRSA

A

A sub-set of S.Aureus

Antibiotic resistance S.Aureus

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15
Q

What are the disease consequences of bacterial pathogens acquired by the upper respiratory tract

A

Upper respiratory tract infection- Pharyngitis
Tonsillitis
Sinusitis

Spread to adjacent tissues
Middle ear infection
Brain abscess
Meningitis

Lower respiratory tract infection
Bronchitis
Pneumonia
Pneumonitis
Empyema

Spread to bloodstream

Bacteraemia eg pneumococcal bacteremia; meningococcal bacteremia

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16
Q

Why are upper respiratory tract bacterial pathogens able to cause diseases in the brain

A

Bones at the bottom of the skull are thin, hence bacteria in the sinus can spread to the brain easily, causing a brain abscess or meningitis.

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17
Q

What is Sepsis

A

Organ failure dysfunction in response to infection, variable with different bacteria.

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18
Q

What are the portals of entry for the urogenital tract

A 
Extrinsic sources- urinary catheters to help pass urine- bypasses normal protection- extrinsic bacteria can infect the bladder by travelling up the catheter.
Bladder
Large 
intestine
Intrinisic Sources
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19
Q

How is the bladder connected to the outside world

A

Urinary bladder connected to the outside world by urethra to the penis or vagina ( shorter in females).
Also connected to the rectum (exit of LI).

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20
Q

Describe the bacterial pathogens that usually infect the urinary tract

A

Usually intrinsic bacteria that infect the urinary tract - from the large intestine. (Escherichia coli
Bacteroides ap.
Proteus spp
Klebsiella)

Extrinisic bacteria can infect the urinary tract
Nosocomial transmission via catheters
Escherichia coli
Klebsiella spp

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21
Q

What are the pathogens that usually infect the genital tract

A

Intrinsic pathogens that infect the genital tract- usually from the large intestine (Streptococcus group B (pregnancy)
Candida/yeast)

Extrinisic infections that infect the genital tract

Sexually transmitted
Neisseria gonorrhoeae
Chlamydia trachomatis
Treponema pallidum (syphilis)
HIV, HSV (viruses)
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22
Q

What are the infectious disease consequences of urogenital tract infection

A

Urinary tract infection- Cystitis
Pyelonephritis

Spread to bloodstream
Bacteraemia
E.g. E. coli bacteremia

Genital tract infection
Gonococcal urethritis
Pelvic inflammatory disease
Tubo-ovarian abscess

Pregnancy-related infection
Neonatal group B strep infection
Neonatal gonococcal conjunctivitis

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23
Q

Which part of the body is cystitis limited to

A

The bladder

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24
Q

What is Pyelonephritis

A

bacteria travels from bladder to kidney via ureter- can spread to the bloodstream.

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25
Q

What are the consequences of gonorrhoea

A

Can spread to the fallopian tubes- abscess- infertility.

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26
Q

Describe how broken skin can act as a portal of entry.

A

Surgery/any wound
Skin diseases incl. varicella, eczema burns,athletes foot, pressure sores…..
IVDA- intravenous drug abuse
Insect bites- not directly- people scratch- skin breaks

Bites-human and animal
i.v. cannulae
(intravenous portal of entry)

Bacteria have virulence- wait for break in skin and infect the body.

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27
Q

List some of the bacteria that infect broken skin

A

Skin & mouth bacteria:

Staphylococcus aureus
Streptococcus pyogenes

Recent antibiotics/hospital
MRSA, Pseudomonas

Surgery/bowel flora exposure
All the above + Gram negatives

28
Q

Describe some of the unusual pathogens that target broken skin

A

Pasteurella multocida from dog bites
Aeromonas hydrophilia from medicinal leeches
Clostridium perfringens from soil

29
Q

What are the consequences of infection via broken skin

A 
Superficial infection
Cellulitis- red and inflamed skin
Abscess- collection of pus
Fasciitis
Myositis
Gangrene/necrotic infection
Bacteremia
30
Q

What is the portal of entry for bacteria of the GI tract

A 
‘faeco-oral route’
Contaminated food & water
Escherichia coli (travellers diarrhoea/EPEC/EHEC)
Campylobacter jejuni (food poisoning)
Shigella spp(dysentery)
Vibrio cholerae (cholera)
Salmonella enterica (food poisoning)
Salmonella typhi (typhoid)
Listeria monocytogenes
Clostridium difficile
31
Q

Describe the disease consequences of bacteria acquired by the GI tract

A 
Diarrhoeal illnesses 
Vomiting only (eg toxins)
‘D & V’
Diarrhoea only
Dysentery- bloody diarrhoea (suggests invasive infection)
Bacteremic/systemic infections
Typhoid (S. typhi)
Listeriosis (L. monocytogenes)
Salmonellosis and septic arthritis, aortitis

Toxin-mediated disease
D & V (eg S. aureus enterotoxin)
Neurological (eg botulism)

32
Q

What is meant by pathogenic bacteria

A

Bacteria that cause disease

33
Q

What are the two types of pathogenic bacteria, give examples of each

A

True
eg Staphylococcus aureus from skin causing large abscess and bacteremia

Opportunistic
Eg Staphylococcus epidermidis from skin causing prosthetic hip joint infection

34
Q

What are commensal bacteria

A

Bacteria that do not cause disease- Eg Lactobacillus in vagina and GI

35
Q

What is meant by pathogenicity

A

The ability to cause disease

36
Q

What two factors affect pathogenicity

A

Infectivity and Virulence

37
Q

What is meant by infectivity, what factors effect infectivity

A

General features favoring infection
Infectious dose
Transmission to host
Ability to colonise host
Tropism– Find unique niche (in or outside cells)
Replicate
Immune Evasion at site of colonisation or niche

38
Q

What is meant by virulence, what factors effect virulence

A 
Features that enhance disease causation
Toxin production
Enzymes that degrade host molecules
Interruption of normal host processes
Complete immune evasion
39
Q

What is meant by infectious dose

A

The infectious dose is the number of bacteria required to initiate an infection

40
Q

What is the infectious dose affected by

A

Route of transmission

Ability to colonise host-

Tropism and motility

Replication speed

Immune evasion at site

41
Q

Describe how the route of transmission can affect infectious dose

A

Stomach acid means high doses often req. Use of antacid lowers infectious dose eg C. difficile, Vibrio cholerae easily killed by acid

42
Q

Describe how the ability to colonise the host can affect infectious dose

A

Enteropathogenic E. coli “EPEC” type 3 secretion for adherence (pedestals

43
Q

Describe how tropism and motility can affect infectious dose

A

Vibrio cholerae. High infective dose

But flagella motility may help reach gut epithelium

44
Q

Describe how replication speed and immune evasion at site can affect infectious dose

A

Mycobacterium tuberculosis. Low infective dose. Very low replication rate. Able to survive inside macrophages and resist killing

45
Q

What is a key characteristic of bacteria with low infectious dose

A

Ability to resist phagocytic killing.

46
Q

Define virulence

A

Features that enhance disease causation

47
Q

Using the example of S. pneumoniae- explain some features that enhance disease causation (virulence)

A

Toxin production eg Pneumolysin: cholesterol-dependent pore-forming toxin affecting lung architecture

Degradation of host molecules eg Hyaluronan lyase- degrades host hyaluronic acid matrix for nutrition and ? spread

48
Q

Explain virulence using the example of

A

S. aureus
Interference with host cell function eg Superantigens made by S. aureus interfering with normal T cell function

Immune evasion eg S. aureus leukocidins leading to neutrophil death and abscesses

49
Q

What are superantigens

A

T cell proliferation- tricks the body into thinking its a self cell
Cytokine Release- sepsis and organ failure

50
Q

List some diseases spread by droplet infection via the mouth

A

Tonsillitis.
Streptococcus pyogenes
Meningococcal septicaemia
Neisseria meningitidis colonises nasopharynx asymptomatically before invading epithelial then endothelial cells

51
Q

What is a disease spread by faecal-oral transmission

A

Cholera

52
Q

Describe the pathogenicity of Vibrio Cholerae

A

Enormous infective dose 106- 1010

Flagella used to penetrate mucus

Then makes 2 component toxin A + B

Binds to GM gangliosides on gut

Triggers cAMP

Chloride efflux

Na and water follow

Profuse diarrhoea “Rice water stools”

53
Q

Describe the transmission of pathogens from the GI tract to the UG tract and its consequences for neonates

A

Genital tract colonisation with group B strep (from GI tract)- Harmless 30-40% of women
leading to invasive group B strep infection in neonates: meningitis, septicaemia, death

54
Q

What is S. aureus and how does it cause disease

A

S. aureus produces a family of Leukocidins

=toxins which destroy neutrophils, producing characteristic pus

55
Q

List some pathogenic gram negative bacteria

A

Neisseria (meningitidis and gonorrhoeae)

Haemophilus influenzae

Escherichia coli (EPEC, EHEC, ETEC, UPEC)
Salmonella spp.,
Vibrio cholerae
Shigella

56
Q

List some pathogenic gram positive bacteria

A 
Staphylococcus  aureus 
Streptococcus
Group A= S. pyogenes
Group B=S. agalactiae
Viridans strep=dental bacteria
Pneumococcus=S. pneumoniae

Clostridium (difficile, tetani, botulinum, pergringens)
Listeria spp.

57
Q

Describe some opportunistic gram negative bacteria

A

Pseudomonas aeruginosa
eg indwelling long-term urinary catheters and multiple UTI’s previously treated with antibiotic
Acinetobacter baumanii
eg open battlefield trauma heavy prophylaxis with broad spectrum antibiotics followed by ICU stay and nosocomial transmission

58
Q

Describe some opportunistic gram positive bacteira

A

Staphylococcus epidermidis
eg prosthetic joint and valve infections, metalwork, central line infections
Enterococcus faecalis
eg abnormal heart valves

59
Q

What is meant by opportunistic pathogens

A

only cause disease when the conditions are permissive.

60
Q

What usually causes vomiting

A

Swallowing the toxins, not the bacteria- C.Difficile.

61
Q

Can soft tissue be infected

A

Yes, connective tissues such as skin as well as muscle can be infected. Results in pain and fever- difficult to see if its an infection.

62
Q

Describe the growth of bacteria in acute disease

A

Rapid growth in tissues to produce the effect of disease before a protective immune response can be mounted.

63
Q

Describe the growth of bacteria in chronic disease

A

Slow growth at all stages- leading to a reduced stimulation of the immune system.

64
Q

What is meant by a carrier state

A

Resistant stationary phase

65
Q

Which mineral is essential to bacteria

A

Iron

66
Q

Describe the mucous surface interactions of bacteria

A

Rapid growth to overcome receptors that could block contact on the epithelial surfaces.

67
Q

Describe the primary lodgement of bacteria in tissues

A

Rapid growth of a small number of bacterial invaders to replace loss inflicted by host defences in inflammatory response to bacterial invasion.

Microbiology 1 (9 decks)

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