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Foundations of Medicine > Classification of pathogenic bacteria- gram negatives > Flashcards

Classification of pathogenic bacteria- gram negatives Flashcards

1
Q

How are bacteria named?

A

genus and then species

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2
Q

What organism causes meningitis disease? (cocci)

A

Neisseria meningitidis (meningococcus)

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3
Q

What is meningitis?

A

inflammation of the meninges and septicaemia.

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4
Q

How could you diagnose meningitis?

A

CSF and Blood cultures

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5
Q

What bacteria causes urethritis in men and pelvic inflammatory disease in women? (cocci)

A

Neisseria gonorrhoeae

spread by sexual contact

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6
Q

What bacteria causes respiratory tract infections? (cocci)

A

moraxella catarrhalis

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7
Q

What are coliforms? (gram negative bacilli)

A

organisms which are in the family enterobacteriaceae

mainly commensals of large human intestine

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8
Q

What is used in preliminary identification?

A

Lactose fermentation is a useful preliminary test in classifying
Gram negative bacilli

CLED Agar gives colour change if lactose is fermented

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9
Q

What is Escherichia coli?

A

vast array of virulence mechanisms- pili, capsule, endotoxin and exotoxins

ferments lactose

over 160 serotypes based on O antigen (LPS)

Important cause of UTI but causes a wide spectrum

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10
Q

What is the E coli that is the commonest cause of traveller’s diarrrhoea?

A

Enterotoxogenic E.coli - produces toxins

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11
Q

What E coli gives rise to bloody diarrhoea?

A

Enterohaemorrhagic E.coli

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12
Q

What E coli is associated with haemolytic uraemic syndrome?

A

E coli O157

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13
Q

Describe salmonella spp?

A

Does not ferment lactose.

Second commonest cause of bacterial diarrhoea in UK.

Can be invasive i.e. enters bloodsteam

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14
Q

Describe salmonella typhi?

A

cause of typhoid fever
* Fever, constipation early stages.
* Organism can be isolated from blood cultures as well as faeces.
* Risk during foreign travel but vaccine available

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15
Q

What is Shigella spp?

A

cause of diarrhoea,dysentry

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16
Q

What is klebsiella spp?

A

cause of UTI and hospital acquired pneumonia

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17
Q

What is proteus spp?

A

Causes UTI – often associated with stones

18
Q

What is campylobacter spp?

A
  • Microaerophilic– likes low O2 .
  • Source is domestic animals and chickens.
  • Spread via faecal-oral route.
    content
  • Foul smelling -> bloody diarrhoea (incubation period 2-5
    days).
  • Commonest cause of bacterial diarrhoea in UK
19
Q

What is helicobacter pylori?

A
  • Curved rods.
  • Natural habitat is human stomach.
  • Damages mucosa and causes ulcers.
  • Strong risk factor for gastric adenocarcinoma
20
Q

What is haemophilus influenzae?

A
  • Cocco-bacilli (mixed appearance).
  • Causes respiratory tract infection (second to S. pneumoniae).
  • Capsulate form (type “b”) was formerly an important cause of
    meningitis in children (Hib conjugate vaccine)
21
Q

What is pseudomonas spp?

A
  • Water and soil coloniser – drains, sinks, mops.
  • May contaminate medical equipment.
  • Hospital acquired cause of sepsis: e.g. UTI,
    bacteraemia, pneumonia (rare).
  • Feared respiratory pathogen in cystic fibrosis.
  • Multi-drug resistance mechanisms.
  • Limited treatment options.
22
Q

What are anaerobes?

A
  • Often part of a polymicrobial infection.
  • Increasing importance and recognition.
  • Bacteriodes spp.
  • Prevotella
  • Porphyromonas
23
Q

What is bacteroides fragilis?

A
  • Part of normal colonic flora.
  • Causes intra-abdominal abscess.
  • May spread to other sites
24
Q

Give examples of oral anaerobes?

A

-Prevotella
* Porphyromonas e.g. P. gingivalis
* Pasteurella spp
* Capnocytophyga spp

25
Q

Why would bacteria not stain by gram method?

A

not all bacteria have same cell wall and some don’t have cell wall.

26
Q

Describe the acid and alcohol fast bacilli?

A

Resistant to decolourisation by acid or alcohol after staining with carbolfuchsin.
* Mycobacterium species are visualised with special
stains e.gZiehl-Neelsen(ZN) or Auramine

27
Q

Why are we interested in AAFBs? (mycobacteria)

A

the aetiological agent of tuberculosis , Mycrobacterium tuberculosis is an important member of the AAFB
-if clinician suspicious of tuberculosis- stained using special stains

28
Q

Laboratory identification of mycobacteria?

A
  • ZN or Auramine phenol (screening).
  • Does not identify species!!!
  • Culture required for ID.
  • New automated liquid culture.
  • Growth in 2-4 weeks.
  • Molecular detection and
    identification of MTB possible
29
Q

What is the disease that mycobacterium tuberculosis causes?

A

tuberculosis

30
Q

What disease is caused by mycobacterium leprae and what is its features?

A

leprosy
mycobacterium leprae cannot be cultured
attacks peripheral nerves

31
Q

Describe spirochaetes?

A
  • Long, spiral-shaped bacteria.
  • Not easily visualised by light microscopy.
  • Very difficult to culture (never Treponema pallidum).
  • Dark ground microscopy or immunofluorescence.
  • Often diagnosed by serology
32
Q

What diseases are caused by spirochaetes?

A

syphillis
lyme disease
leptospirosis

33
Q

Describe the stages of syphillus?

A
  • Primary syphilis: non-painful skin lesion (chancre) at the
    site of infection (skin or mucous membranes)
  • Secondary syphilis (6-8 weeks after primary symptoms):
    generalised systemic illness and rash
  • Latent phase: symptomatic episodes may occur
  • Tertiary syphilis (years after primary symptoms): central nervous system
  • Congenital syphilis: stillbirth, neonatal death or disease
34
Q

Describe the stages of lyme disease?

A
  • Transmitted by ticks.
  • Stage 1: Skin rash (erythema chronicum migrans) appears at the site of
    the tick bite.
  • Stage 2: Systemic illness occurs in some patients
    weeks or months later when patients suffer cardiac
    or neurological and musculoskeletal symptoms
  • Stage 3: Chronic disease, occurring years later when patients present with
    chronic skin, nervous system or joint abnormalities
  • Diagnosed by clinical assessment and serology (antibody detection)
35
Q

Describe leptospirosis?

A
  • Infects animals and concentrates in the kidneys.
  • Spread is via infected urine and other body fluids and
    tissues (zoonosis).
  • At-risk groups– sewage workers– watersports.
  • Range of clinical presentations– Weil’s disease – febrile illness with systemic upset, liver
    and renal failure, aseptic meningitis, 10 % mortality.
36
Q

Describe chlamydia?

A
  • Obligate intracellular bacteria.
  • Culture only in cell lines (do not grow on agar).
  • Can be diagnosed by serology.
37
Q

What are the chlamydia respiratory infections?

A

– Chlamydophila pneumoniae– Chlamydophila psittaci (psittacosis)- contact with birds.

38
Q

What is chalmydia trachomatis?

A

can cause trachoma and genital and neonatal infections

39
Q

What shape are bacilli bacteria?

A

rod shaped

40
Q
A

Foundations of Medicine (61 decks)

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