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[Y1] Pathology > Bacterial infections > Flashcards

Bacterial infections Flashcards

1
Q

Microbiological hazard categories: what is hazard group 1?

A

A biological agent that is unlikely to cause human disease

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2
Q

Microbiological hazard categories: what is hazard group 2?

A

A biological agent that can cause human disease and may be a hazard to employees; it is unlikely to spread to the community and there is usually an effective prophylaxis or treatment available

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3
Q

Microbiological hazard categories: what is hazard group 3?

A

A biological agent that can cause severe human disease and presents a serious hazard to employees; it may present a risk of spreading to the community but there is usually effective prophylaxis or treatment available

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4
Q

Microbiological hazard categories: what is hazard group 4?

A

A biological agent that causes severe human disease and is a serious hazard to employees; it is likely to spread to the community and there is usually no effective prophylaxis or treatment available

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5
Q

what percentage of bacterial species are human pathogens?

A

<0.02% but likely <0.0001%

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6
Q

how many known human pathogens are there?

A

<100

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7
Q

how many bacterial species are there (known)?

A

> 5000

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8
Q

why do bacteria cause infections?

A

Body provides favourable niche in which to reproduce; human tissues provide nutrients and reduced competition for resources

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9
Q

why do not all bacteria cause infections?

A
  • not favourable environment for all species
  • immune system prevents most bacteria from colonizing
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10
Q

what 6 places can bacteria infect?

A
  • central nervous sytem
  • gastrointestinal tract
  • multisystem
  • respiratory tract
  • skin and muscle
  • urogenital tract
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11
Q

name 2 bacterial infections that affect the central nervous system

A
  • Neisseria meningitidis
  • Haemophilus influenzae
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12
Q

name 4 bacterial infections that affect the gastrointestinal tract

A
  • Escherichia coli
  • Shigella
  • Salmonella
  • Campylobacter jejuni
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13
Q

name 2 bacterial infections that affect multiple systems

A
  • Borrelia burgdorferi
  • Yersinia pestis
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14
Q

name 3 bacterial infections that affect the respiratory tract

A
  • Streptococcus pyogenes
  • Streptococcus pneumoniae
  • Mycobacterium tuberculosis
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15
Q

name 2 bacterial infections that affect the skin and muscle

A
  • Staphylococcus aureus
  • Streptococcus pyogenes
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16
Q

name 3 bacterial infections that affect the urogenital tract

A
  • Escherichia coli
  • Proteus mirabilis
  • Chlamydia trachomatis
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17
Q

what is airborne transmission?

A

Spread by aerosolized droplets (sneezing, coughing) and fomites

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18
Q

name 2 airborne conditions

A
  • Bordetella pertussis: Whooping cough
  • Mycobacterium tuburculosis: Tuberculosis
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19
Q

what are the 2 types of ingestion transmission conditions?

A
  • infection: pathogen reaches gastrointestinal tract and rapidly multiplies
  • intoxication: Ingestion of toxins produced by bacteria (typically results in acute vomiting 1-6 h post ingestion)
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20
Q

what are 3 examples of vectors in vector-borne transmission?

A
  • ticks
  • lice
  • fleas
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21
Q

what are 4 types of direct contact transmission?

A
  • skin wounds
  • scratch/bite
  • nasal secretions and shed skin
  • sexual intercourse (STIs)
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22
Q

what catagory pathogen is B. anthracis? why?

A
  • Catagory 3
  • Considered a dangerous bioterrorism threat. No human transmission, danger is due to production of toxins and resistant endospores.
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23
Q

what is the zeihl-neelsen stain used for?

A

bacteriological staining method used to identify acid-fast organisms, including Mycobacteria
- bacteria are stained red/pink

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24
Q

what do virulence factors enable?

A

pathogenic bacteria to colonise, invade and replicate within host organism
- E.g. adhesins and fimbriae, capsule, exoenzymes, toxins

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25
Q

what are virulence factors?

A

the molecules that assist the bacterium colonize the host at the cellular level

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26
Q

what are 2 functions of virulence factor?

A
  • Some of these enable the bacteria to avoid or overcome the immune response
  • Some bacteria produce toxins that help to overcome immune response and enable them to invade cells / access nutrients
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27
Q

give 6 methods to prevent bacterial infections

A
  • hygine and sanitation (water treatment)
  • vaccines (DTaP, MenACWY)
  • prophylaxis (antibiotics, immunotherapy)
  • safe sex
  • insecticides (vector control)
  • quarantine and contact tracing
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28
Q

what are the 4 types of vaccines?

A
  • inactivated
  • attenuated
  • subunit
  • toxoid
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29
Q

what are the 2 ways to detect bacterial infections?

A
  • patient presentation (signs and symptoms)
  • samples taken from sputum, blood, urine, stools
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30
Q

give 6 example of bacterial infection symptoms

A
  • fever
  • vomiting
  • diarrhoea
  • cough
  • rash
  • pus/exudate
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31
Q

give 5 tests for sample that can be used to diagnose bacterial infections

A
  • urine dip-stick test
  • microbial culture (colony morphology, selective media)
  • microscope (cellular morphology, differential stain)
  • biochemical tests
  • molecular diagnostics (e.g. PCR)
  • serological diagnostics (e.g. ELISA)
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32
Q

what are 4 treatments of bacterial infections?

A
  • topical disinfectant (chlorhexidine)
  • surgery / debridement
  • antimicrobial coatings (silver nanoparticles in wound dressings)
  • antibiotics
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33
Q

what are antibiotics that inhibit growth called?

A

bacteriostatic

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34
Q

what are antibiotics that cause bacterial death called?

A

bactericidal

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35
Q

why is clavulanic acid given along side penicillin?

A

to inactivate B-lactamases

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36
Q

why are combinations of antibiotics used to treat bacterial infections?

A

may help prevent evolution of resistance and treat infections caused by MDR bacteria

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37
Q

what type of bacteria is Myobacterium tuberculosis?

A

weak gram positive rod

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38
Q

when was Myobacterium tuberculosis discovered and by who?

A

Robert Kock (1882)

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39
Q

what disease does Myobacterium tuberculosis cause?

A

tuberculosis

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40
Q

what is unique about Myobacteria?

A

have a unique cell wall structure with high concentration of mycolic acid

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41
Q

what is the growth rate of Myobacterium tuberculosis?

A

Slow growing (generation time approx. 16 hr) – takes 10 – 14 days to culture in lab

42
Q

only __% of TB infections lead to disease, __% latent infections

A

only 5% of TB infections lead to disease, 95% latent infections

43
Q

what percentage of TB cases are fatal wihtout treatment?

A

50%

44
Q

how does TB stay latent in the body?

A
  • Immune response involves formation of granulomas (“tubercles”) consisting of macrophages, lymphocytes and epithelioid cells which trap the bacteria
  • Mtb survive inside granulomas and become dormant, but can be reactivated to cause active infection if untreated
45
Q

what are 5 symptoms of TB?

A
  • fever
  • night sweats
  • weight loss
  • cough
  • cavities in lung
46
Q

what percentage of TB cases are in the lungs?

A

in the lungs (pulmonary TB)

47
Q

where else can TB affect? (give 6)

A

extrapulmonary TB:
- lymphatics
- kidneys
- urogenital tract
- CNS
- bones
- blood vessels

48
Q

how do you detect TB with a stain?

A

Use Ziehl Neelsen stain to differentiate acid-fast bacteria:
- Sample stained with carbolfuschin stain and heated – all cells stain red/pink
- rinse with alcohol
- bacteria left red/pink (due to high concentrations of mycolic acids in cells)
- non-acid fast bacteria are decolourised

49
Q

how do you detect TB with the mantoux test?

A
  • 0.1 ml of PPD injected into the forearm to produce a small bleb
  • Localised hardening (“induration”) indicates hypersensitivity
  • positive test indicates infection or previous infection/vaccination
50
Q

how do you detect TB with an X-ray?

A

Cavities seen as radio-opaque patches in lower parts of lung

51
Q

what is the treatment for people with TB?

A

Triple therapy over 6 months of:
- isoniazid
- pyrazinamide
- rifampicin / rifampin

52
Q

what is the function of isoniazid for treating TB?

A

interferes with mycolic acid cell wall synthesis

53
Q

what is the function of Pyrazinamide for treating TB?

A

action unknown, but converted to active form in the liver, pyrazinoic acid

54
Q

what is the function of Rifampicin / Rifampin for treating TB?

A

inhibits transcription by binding to β-subunit of RNA polymerase

55
Q

what is the suggest treatment for people who have been in close contact with TB?

A

Prophylaxis for 1 year with Isoniazid

56
Q

how many people are currently infected with TB globally?

A

2 billion people currently infected globally (latent TB, do not transmit)

57
Q

how many people fell ill with TB in 2019?

A

10 million

58
Q

who discovered E.coli? when?

A

Discovered in 1885 by German biologist Theodor Escherich

59
Q

what type of bacteria is E.coli?

A

Gram negative rod, Enterobacteriaceae
Facultative anaerobe

60
Q

how many E.coli are in stool?

A

100 billion - 10 trillion

61
Q

where is E.coli found in the body?

A
  • colonises intestinal lumen soon after birth
  • attach to intestinal mucosa via fimbriae
62
Q

where do pathogenic strains of E.coli infect the body?

A

gastrointestinal tract

63
Q

who can non-pathogenic E.coli cause disease in?

A

immunocompromised

64
Q

what is EPEC?

A

EPEC: Enteropathogenic E. coli
- attach and destroy microvilli of SMALL intestine
- do not produce toxins

65
Q

what is ETEC?

A

ETEC: Enterotoxigenic E. coli
- bind receptors of cells in SMALL intestine
- make heat labile enterotoxins (LT), similar to cholera toxin
- make heat stable enterotoxins (ST) which activate guanylate cyclase → increased guanosine monophosphate → increased fluid secretion

66
Q

what 6 types of E.coli cause gastroenteritis?

A
  • EPEC
  • ETEC
  • EHEC
  • EIEC
  • EAEC
  • DAEC
67
Q

what is EHEC?

A

EHEC: Enterohaemorrhagic E. coli
- makes verotoxin (Shiga toxin) which acts on intestinal epithelium
- O157:H7 causes haemorrhagic colitis (HC), destruction of the mucosa and hemolytic-uremic syndrome (HUS)

68
Q

what is EIEC?

A

EIEC: Enteroinvasive E. coli
- attach to mucosa of LARGE intestine
- invade cell by endocytosis
- lyse endocytic vacuole and spread to neighbouring cells – destruction and blood

69
Q

what is EAEC?

A

EAEC: Enteroaggregative E. coli
- aggregate on SMALL intestine cells via fimbriae
- produce labile toxins
- problem for children in developing countries
- E. coli O104:H4 caused outbreak in Germany 2011 killing 32 people – acquired Shiga toxin via HGT

70
Q

what is DAEC?

A

DAEC: Diffusely adherent E. coli
- produce alpha hemolysin and cytotoxic necrotizing factor 1
- problem for children

71
Q

what is gastroenterisitis?

A

Disturbance of the normal electrolyte and water balance of the small intestine; often occurs due to production of toxins e.g. shiga toxin

72
Q

name 5 symptoms of gastroenteritis

A
  • Watery diarrhoea, possibly with blood (Leads to dehydration)
  • Vomiting
  • Mild fever
  • Stomach cramps
  • Some cases lead to haemorrhagic colitis or haemolytic-uremic syndrome, can cause renal failure
73
Q

how is gastroenteritis dectected?

A

using a stool sample

74
Q

what are the 2 diagnostic methods to diagnose gastroenteritis?

A

1.Cultured on sorbitol MacConkey agar
- Colonies that fail to produce acid from sorbitol (white) are tested with specific antisera to cell wall components to confirm specific strain e.g. O157:H7

  1. Molecular diagnostics e.g. PCR for Shiga toxin
75
Q

how do you treat gastroenteritis?

A
  • Rehydration (water & electrolytes)
  • Antibiotics in some cases
76
Q

why don’t you use antibiotics on EHEC 0157:H7?

A

they promote toxin release

77
Q

how do you prevent gastroenteritis?

A

Cook food well and avoid untreated water
Personal hygiene - hand washing

78
Q

who discovered Yersinia pestis? when?

A

Discovered in 1894 by Alexandre Yersin and Kitasato Shibasaburo

79
Q

what type of bacteria is Yersinia pestis?

A

Gram negative rod, Enterobacteriaceae

80
Q

what illness does Yersinia pestis cause?

A

Causes plague (plaga, Latin for pest), also called Black Death due to black areas on skin caused by subcutaneous haemorrhages

81
Q

how do you get the plague from Yersinia pestis?

A
  • Vectored by fleas that are carried by rodents, wild animals (bubonic)
  • Once established, it can spread from person to person by aerosolized droplets (pneumonic)
82
Q

what were the 3 plague pandemics? when?

A
  • The Plague of Justinian: first plague pandemic AD 541-542
  • The Black Death (1328-1351): Large scale plague occurred in Europe
    - Followed trade routes, rats and rodents carrying fleas with the bacterial pathogen inside them
  • Third plague pandemic (1855-1860): China, Hong Kong, India
83
Q

what is the bubonic plague?

A

Spread from bite site via lymphatics to lymph nodes
Enlarged lymph nodes “buboes” (bubo, Latin for swelling)

84
Q

what is septicemic plague?

A

If large numbers of bacteria enter bloodstream it causes septicemia, hemorrhagic illness, multisystem failure, death within 3-5 days

85
Q

what is pneumonic plague?

A

has almost 100% mortality if untreated within 12 h

86
Q

what are the symptoms of each plague?

A

Sudden onset of fever, headache, weakness
- Bubonic plague: Enlarged lymph nodes “buboes”
- Septicemic plague: subcutaneous haemorrhaging “black death”
- Pneumonic plague: rapidly developing pneumonia, chest pain

87
Q

what 4 laboratory tests can be used to diagnose the plague?

A
  • Culturing, Gram stain / microscopy
  • Biochemical tests
  • Molecular diagnostics – PCR for F1 antigen
  • Serological diagnostics – F1 antigen by ELISA
88
Q

how do you treat plague?

A

antibiotics

89
Q

what 3 antibiotics are used to treat plague? function?

A
  • Streptomycin – prevents translation by binding to 30S ribosomal subunit
  • Chloramphenicol – bacteriostatic, binds to peptidyltransferase component of 50S ribosomal subunit – stops aa chain elongation
  • Tetracycline antibiotics – inhibit protein synthesis (prevent aminoacyl-tRNA binding to ribosome)
90
Q

what 4 things can be done to prevent plague?

A
  • Quarantine
  • Control flea and rodent populations
  • Prophylaxis with tetracycline if visiting affected area
  • Partially effective vaccine with formalin-killed bacteria (USP Plague vaccine), used for high risk people e.g. military
91
Q

who discovered Neisseria gonorrhoeae? when?

A

discovered in 1876 by Albert Neisser

92
Q

what type of bacteria is Neisseria gonorrhoeae?

A

gram negative diplococci

93
Q

what bacteria causes gonorrhoea (“the clap”)?

A

Neisseria gonorrhoeae

94
Q

how does Neissseria gonorrhoeae enter the body?

A

by vaginal/oral/anal sex

95
Q

how does Neissseria gonorrhoeae not get washed away by body fluids?

A

Attach to mucosal cells by pili and Opa proteins, prevent washing away by urine or discharge

96
Q

where doe Gonorrhoea go in the body?

A
  • Spread through cervix of women and urethra of men
  • IgA protease resists antibodies
  • Invade non-ciliated epithelial cells by phagocytosis
  • Can survive and proliferate in phagocytic cells
97
Q

what 4 things can gonorrhoea cause due to the inflamatory response?

A

Causes:
- urethritis
- cervicitis
- proctitis
- laryngitis

98
Q

what are gonorrhea symptoms in males and females?

A

Males more likely to be symptomatic:
- Pain during ejaculation or urination with yellow or creamy discharge

50% of women asymptomatic or mild symptoms:
- Complications include pelvic inflammatory diseases (PID) and infertility
- Neonates can develop ophthalmia neonatorum (conjunctivitis of the newborn)

99
Q

how do you treat gonorrhea?

A

antibiotics

100
Q

what are the antibiotics used to treat gonorrhoea? function?

A
  • Ceftriaxone – cephalosporin 𝛽-lactam - inhibits peptidoglycan biosynthesis by binding to transpeptidases
  • Azithromycin - bacteriostatic, binds to peptidyltransferase component of 50S ribosomal subunit – stops aa chain elongation
101
Q

how do you prevent the spread of gonorrhoea?

A
  • Contact tracing - important to communicate infection to sexual partner(s)
  • Safe sex (inc. oral)

[Y1] Pathology (10 decks)

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