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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
Group D streptococci
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
Gram positive bacilli can be...
aerobic or anaerobic
27
Clostridium difficile
- '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
Four common and clinically important Gram Positive bacteria?
Staphylococcus aureus Streptococcus pyogenes Streptococcus pneumoniae Clostridium difficile
29
Bacteria are also broadly classified according | to what morphology (shape) under the microscope
``` Cocci = round. Bacilli = rod-shaped. ```
30
Clinically significant Gram Negative bacteria?
``` Coliforms Neisseria spp Moraxella spp Haemophilus influenzae Campylobacter spp. and Helicobacter spp. Bacteroides and other anaerobes ```
31
Neisseria spp types
Neisseria meningitidis
32
Clinically significant bacteria which are not readily identified by Gram staining?
Mycobacteria Spirochaetes Chlamydia
33
Neisseria meningitidis
Meningitis – inflammation of the meninges and septicaemia. Often life threatening
34
Neisseria gonorrhoeae
Causes urethritis in men and pelvic inflammatory disease in women. Sexually transmitted.
35
Moraxella catarrhalis
Causative agent of respiratory tract infections. | Especially in those with underlying lung pathology
36
What is a coliform?
organisms which are in the family Enterobacteriaceae
37
Gram negative bacteria are usually found where?
Mainly commensals of the human large intestine.
38
What is a useful preliminary test in classifying Gram negative bacilli?
Lactose fermentation as these bacteria can ferment the sugar lactose
39
E.coli
Gram negative bacilli Human and animal reservoirs. Ferments lactose. Strains vary considerably in disease potential. Important cause of urinary tract infection (UTI).
40
Enterotoxogenic E.coli
commonest cause of traveller’s diarrhoea
41
Enterohaemorrhagic E.coli
bloody diarrhoea
42
Campylobacter spp.
strain of gram negative bacteria Spread via faecal-oral route. Foul smelling -> bloody diarrhoea Commonest cause of bacterial diarrhoea in UK
43
Helicobacter pylori
Curved rods Natural habitat is human stomach. Damages mucosa and causes ulcers. Strong risk factor for gastric adenocarcinoma (malignant tumour)
44
oral anaerobes
Important in aetiology of periodontal disease and | may be part of polymicrobial dental abscesses
45
Salmonella spp
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
Miscellaneous bacteria
this bacteria cannot be:- stained with Gram’s method. cultured by standard methods
47
mycobacteria:- Mycobacterium tuberculosis
Tb caused by this bacteria | also has a link with HIV
48
way of diagnosing Tb?
rapid diagnostic nucleic acid amplification tests
49
Mycobacterium leprae
Causes leprosy This bacterium cannot be cultured Mainly India, Nepal, Brazil Attacks peripheral nerves
50
Spirochaetes
Long, spiral-shaped bacteria. Not easily visualised by light microscopy. Very difficult to culture Often diagnosed by serology
51
Common spirochaete diseases
Treponema pallidum= Syphilis Borrelia burgdorferi= Lyme disease Leptospira interrogans= Leptospirosis- kidney infection
52
Syphilis stages
primary- skin lesion secondary- generalised systemic illness and rash tertiary- years after primary symptoms CNS latent congenital- stillbirth, neonatal death or disease
53
diagnosis and management of syphilis
serology, nucleic acid amplification tests (NAAT) Management – antibiotics, contact tracing and screening
54
Chlamydia
Culture only in cell lines (do not grow on agar). | Can be diagnosed by serology.
55
respiratory chlamydia infection
``` Chlamydophila pneumoniae Chlamydophila psittaci (psittacosis) - contact with birds ```
56
Ophthalmic and genital tract chlamydia infection
Chlamydia trachomatis – Trachoma (tropical eye infections) – Genital and neonatal infection Neonatal infections
57
Diagnosis of Chlamydia trachomatis
nucleic acid amplification tests (NAAT) on first void urine (first urine excreted in the morning) vulval/vaginal swabs
58
What causes syphilis?
Treponema pallidum
59
bio film
a mucous layer with colony of bacteria that lies on a solid surface e.g on a catheter
60
frimbriae
short hair like fibres enabling adhesion of bacterial cell onto surfaces
61
capsule
has H20- prevents dessication | enhances ability to cause disease- virulence factor

P.O.D own flashcards (34 decks)

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