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P.O.D own flashcards > Classification of pathogenic bacteria > Flashcards

Classification of pathogenic bacteria Flashcards

1
Q

Bacteria- what are they?

A

major group of micro-organisms causing disease
mainly single-celled prokaryotes
most reproduce by binary fission

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2
Q

What is a major threat to public health currently?

A

drug resistance

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3
Q

Why are gram positive and negative bacteria important clinically?

A

Different classes of antibiotics are effective against Gram positive and Gram negative bacteria -> targeted treatment.

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4
Q

Staphylococci

A

aerobic gram-positive cocci that cause pus formation. Group together in grape-like clusters

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5
Q

Streptococci

A

a genus of gram-positive coccus- group together in chains

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6
Q

Enterococci

A

a Gram-positive bacterium inhabiting the GI tracts of humans and other mammals. Group together in chains

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7
Q

Define coccus

A

any spherical or roughly spherical bacterium

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8
Q

What is the coagulase test?

A

used to distinguish between staphylococci species

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9
Q

What does it mean to be coagulase positive?

A

Staphylococcus aureus present- MSSA or MRSA skin infections.
Commensal organism carried in nose, axilla, perineum. A major human pathogen!
Wide range of disease from boils/abscesses and soft tissue infections to septicaemia and osteomyelitis.

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10
Q

Commensal bacteria?

A

are part of the normal flora in the mouth.

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11
Q

Why is Staphylococcus commonly resistant to penicillin?

A

strands of staphylococcus can produce penicillinase that resists use of penicillin to fight infection.

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12
Q

Aerobic gram positive cocci

A

staphylococci
streptococci
and enterococci

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13
Q

What is a blood agar test for?

A

used to determine types of streptococci (a type of gram positive cocci)

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14
Q

Which organism turns blood agar green?

A

α-haemolytic streptococci

partial haemolysis- splitting of red blood cells

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15
Q

which organism turns blood agar clear?

A

β- haemolytic streptococci (complete haemolysis)

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16
Q

organism has no effect on blood agar colour?

A

non-haemolytic streptococci

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17
Q

disease caused by streptococci pneumoniae (pneumococcus)

A

pneumonia, meningitis, septicemia

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18
Q

Infection caused by viridans streptococci (oral commensal bacteria)

A

cause infective endocarditis (infection of heart valves)

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19
Q

Two types of α-haemolytic streptococci

A

Streptococcus pneumoniae (pneumococcus) and Viridans streptococci

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20
Q

What can β- haemolytic streptococci be divided into?

A

divided into groups A-G

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21
Q

How are β- haemolytic streptococci further identified?

A

by carbohydrate surface antigens

Lancefield Group

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22
Q

Which groups of β- haemolytic streptococci are most clinically important?

A

A, B, F and D

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23
Q

Group A streptococci

A

Streptococcus pyogenes- a major ‘flesh eating’ pathogen

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24
Q

Group B streptococci

A

Streptococcus agalactiae
Neonatal sepsis:- Meningitis, Bacteraemia (in the blood)
Also responsible for invasive infections in adults (often older and underlying factors e.g. diabetes, liver disease / alcohol abuse etc

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25
Q

Group D streptococci

A

Now re-classified as Enterococcus spp. e.f Enterococcus faecalis.
often non-haemolytic i.e no effect on colour of blood agar. Found in the gut as normal commensal bacteria. Cause UTI’s and endocarditis

26
Q

Gram positive bacilli can be…

A

aerobic or anaerobic

27
Q

Clostridium difficile

A
  • ‘difficult’ to culture.
  • Important cause of diarrhoea, associated with toxin production and potentially fatal.
  • Increased risk with antibiotic use and anything else that disrupts the normal gut flora.
  • Spread / transmitted via spores.
  • Detect antigen & toxin in stool sample by ELISA
28
Q

Four common and clinically important Gram Positive bacteria?

A

Staphylococcus aureus
Streptococcus pyogenes
Streptococcus pneumoniae
Clostridium difficile

29
Q

Bacteria are also broadly classified according

to what morphology (shape) under the microscope

A 
Cocci = round.
Bacilli = rod-shaped.
30
Q

Clinically significant Gram Negative bacteria?

A 
Coliforms 
Neisseria spp
Moraxella spp
Haemophilus influenzae
Campylobacter spp.
and Helicobacter spp.
Bacteroides and other anaerobes
31
Q

Neisseria spp types

A

Neisseria meningitidis

32
Q

Clinically significant bacteria which are not readily identified by Gram staining?

A

Mycobacteria
Spirochaetes
Chlamydia

33
Q

Neisseria meningitidis

A

Meningitis – inflammation of the meninges and septicaemia. Often life threatening

34
Q

Neisseria gonorrhoeae

A

Causes urethritis in men and pelvic inflammatory disease in women. Sexually transmitted.

35
Q

Moraxella catarrhalis

A

Causative agent of respiratory tract infections.

Especially in those with underlying lung pathology

36
Q

What is a coliform?

A

organisms which are in the family Enterobacteriaceae

37
Q

Gram negative bacteria are usually found where?

A

Mainly commensals of the human large intestine.

38
Q

What is a useful preliminary test in classifying Gram negative bacilli?

A

Lactose fermentation as these bacteria can ferment the sugar lactose

39
Q

E.coli

A

Gram negative bacilli
Human and animal reservoirs.
Ferments lactose.
Strains vary considerably in disease potential.
Important cause of urinary tract infection (UTI).

40
Q

Enterotoxogenic E.coli

A

commonest cause of traveller’s diarrhoea

41
Q

Enterohaemorrhagic E.coli

A

bloody diarrhoea

42
Q

Campylobacter spp.

A

strain of gram negative bacteria
Spread via faecal-oral route.
Foul smelling -> bloody diarrhoea
Commonest cause of bacterial diarrhoea in UK

43
Q

Helicobacter pylori

A

Curved rods
Natural habitat is human stomach.
Damages mucosa and causes ulcers.
Strong risk factor for gastric adenocarcinoma (malignant tumour)

44
Q

oral anaerobes

A

Important in aetiology of periodontal disease and

may be part of polymicrobial dental abscesses

45
Q

Salmonella spp

A

salmonella enterica
salmonella typhi
doesn’t ferment lactose

salmonella enterica:- Self-limiting enterocolitis with or without bloody diarrhoea. Second commonest cause of bacterial diarrhoea in UK. Can be invasive (enter bloodstream)
Salmonella typhi:- cause of typhoid fever

46
Q

Miscellaneous bacteria

A

this bacteria cannot be:-
stained with Gram’s method.
cultured by standard methods

47
Q

mycobacteria:- Mycobacterium tuberculosis

A

Tb caused by this bacteria

also has a link with HIV

48
Q

way of diagnosing Tb?

A

rapid diagnostic nucleic acid amplification tests

49
Q

Mycobacterium leprae

A

Causes leprosy
This bacterium cannot be cultured
Mainly India, Nepal, Brazil
Attacks peripheral nerves

50
Q

Spirochaetes

A

Long, spiral-shaped bacteria.
Not easily visualised by light microscopy.
Very difficult to culture
Often diagnosed by serology

51
Q

Common spirochaete diseases

A

Treponema pallidum= Syphilis
Borrelia burgdorferi= Lyme disease
Leptospira interrogans= Leptospirosis- kidney infection

52
Q

Syphilis stages

A

primary- skin lesion
secondary- generalised systemic illness and rash
tertiary- years after primary symptoms CNS
latent
congenital- stillbirth, neonatal death or disease

53
Q

diagnosis and management of syphilis

A

serology, nucleic acid amplification tests
(NAAT)
Management – antibiotics, contact tracing and
screening

54
Q

Chlamydia

A

Culture only in cell lines (do not grow on agar).

Can be diagnosed by serology.

55
Q

respiratory chlamydia infection

A 
Chlamydophila pneumoniae
Chlamydophila psittaci (psittacosis) - contact with birds
56
Q

Ophthalmic and genital tract chlamydia infection

A

Chlamydia trachomatis
– Trachoma (tropical eye infections)
– Genital and neonatal infection
Neonatal infections

57
Q

Diagnosis of Chlamydia trachomatis

A

nucleic acid amplification tests (NAAT) on first void urine (first urine excreted in the morning)
vulval/vaginal swabs

58
Q

What causes syphilis?

A

Treponema pallidum

59
Q

bio film

A

a mucous layer with colony of bacteria that lies on a solid surface
e.g on a catheter

60
Q

frimbriae

A

short hair like fibres enabling adhesion of bacterial cell onto surfaces

61
Q

capsule

A

has H20- prevents dessication

enhances ability to cause disease- virulence factor

P.O.D own flashcards (34 decks)

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