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phase2a medicine > microbiology (bacteria) > Flashcards

microbiology (bacteria) Flashcards

Information regarding bacteria that may come up as part of microbiology.

1
Q

bacterial shapes

A

cocci
bacilli
vibrio
spirochaete

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2
Q

ziehl-neelsen staining

A

used for Mycobacteria

acid-fast will stain pink/red

non acid-fast will stain blue

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3
Q

catalase test

A

staphylococci is catalase positive (will generate gas bubbles); streptococci is catalase negative (no reaction)

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4
Q

coagulase test

A

Staphylococcus aureus is coagulase positive (will clot when added to plasma); other Staphylococcus spp. are coagulase negative

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5
Q

oxidase test

A

bacteria that produce cytochrome oxidase are oxidase positive - e.g. Pseudomonas and Neisseria

positive result will turn black/purple in colour

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6
Q

optochin test

A

differentiates Strep. pneumonia from other alpha haemolytic Streptococci

Streptococci pneumonia + optochin will cause lysis

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7
Q

metronidazole

A

identifies sensitive anaerobes by inhibiting their growth on culture medium

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8
Q

MacConkey agar

A

isolates and identifies enteric bacteria

contains bile salts, lactose, and pH indicator

lactose fermenting bacteria will cause red/pink colony - Escherichia coli and Klebsiella

non-lactose fermenting bacteria will leave a clear colony - Salmonella, Shigella, and Pseudomonas

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9
Q

blood agar - haemolysis

A

alpha haemolysis - green - partial RBC and Hb breakdown - viridans

beta haemolytic - clear zones - complete erythrocyte lysis

non-haemolytic - no change

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10
Q

Lancefield grouping

A

differentiates between beta haemolytic Strep by detecting surface antigens

group A: Streptococcus pyogenes

group B: Stretococcus agalactiae

group D: Enterococcus

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11
Q

exotoxin

A

produced mostly by gram +ve bacteria

actively secreted toxins with a specific action (e.g. botulinum toxin)

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12
Q

endotoxin

A

a component of the cell wall that is released when bacteria are damaged

gram +ve: lipoteichoic acid
gram -ve: lipopolysaccharides

less specific actions include septic shock

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13
Q

gram positive bacterial groups

A 
Streptococcus 
Staphylococcus
Corynebacterium 
Listeria
Bacillus
Clostridium
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14
Q

Streptococcus

A 
chains or diplococci
gram +ve
catalase negative
alpha haemolytic: oralis, sanguis, mutans, mitis
beta haemolytic: progenies, agalactiae 
non-haemolytic: Enterococcus faecalis
Aerobic
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15
Q

Streptococcus pneumoniae

A

alpha haemolytic, diplococci, commensal of upper respiratory tract in 10-30%, droplet transmission
CAP, COPD exacerbation, sinusitis, otitis media
bacterial meningitis
treat with penicillin or erythromycin

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16
Q

Streptococcus Viridans (alpha haemolytic)

A

upper respiratory tract and GI tract commensal
bacterial endocarditis
dental caries
treat with penicillin/amoxicillin (erythromycin if allergic)
bacterial endocarditis treat with penicillin and gentomycin

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17
Q

Streptococcus pyogenes (group A ß-haemolytic)

A

upper respiratory tract commensal in 5%
transmission: airborne, respiratory secretions, hands
skin: cellulitis, necrotising fasciitis, impetigo, erysipelas, wound infections, scarlet fever
URTIs: pharyngitis (strep throat), tonsillitis, acute otitis media
invasive: sepsis
post-infective: rheumatic fever and glomerulonephritis
treat with penicillin/amoxicillin (erythromycin if allergic)

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18
Q

Streptococcus agalactiae (group B ß-haemolytic)

A

faecal commensal in 30-40% of population and vaginal in 10-30%
causes neonatal septicaemia and meningitis in children
causes UTIs, post-partum sepsis, bacterial endocarditis, and septicaemia in adults

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19
Q

Enterococcus (group D non-haemolytic, MacConkey growth)

A 
GI tract commensal 
infective endocarditis
UTI
wound infections
IV catheter infection
treat with penicillin/vancomycin
treat IE with penicillin/vancomycin + gentamicin
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20
Q

Staphylococcus

A

cocci in clumps
gram positive
catalase positive
S.aureus is coagulase positive; the others are coagulase negative
S.aureus has golden yellow colonies; S.epidermidis and S.saprophyticus have white colonies
aerobic

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21
Q

Staphylococcus aureus

A

coagulase positive
anterior nares in 20-30% of population
impetigo, paronychia, abscesses, cellulitis, wound/IV line infection
osteomyelitis and septic arthritis
septicaemia, conjunctivitis, IE, pneumonia
toxin mediated: toxic shock syndrome, scalded skin syndrome, and food poisoning
flucloxacillin
vancomycin for MRSA

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22
Q

Staphylococcus epidermidis

A

coagulase negative
skin and mucous membranes
foreign body infection or native valve endocarditis
treat with flucloxacillin (or vancomycin if resistant)

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23
Q

Staphylococcus saprophyticus

A

coagulase negative
UTIs in sexual active young women
treat with trimethoprim or flucloxacillin

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24
Q

Corynebacterium

A

bacilli
gram positive
aerobic
e.g. C.diptheriae

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25
Q

Corynebacterium diphtheriae

A

nasopharyngeal carriers
droplet spread
diphtheria toxin –> epithelial cell destruction and myocardial/neural cell damage –> bull neck lymphadenopathy and pseudomembrane covering tonsils
treat with erythromycin, diphtheria antitoxin and vaccination
less than 5 cases per year in UK (due to vaccination)

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26
Q

Listeria

A

bacilli
gram positive
aerobic
e.g. Listeria monocytogenes

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27
Q

Listeria monocytogenes

A

domestic animal faeces and food
transmission: contact with animals, ingestions, transplacentally, perinatally
miscarriage and stillbirth
can cause meningitis, pneumonia, encephalitis, and sepsis in neonates, the elderly, or the immunocompromised
treat with ampicillin/erythromycin and gentamicin

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28
Q

Bacillus

A 
bacilli
gram positive
spore forming
aeorbic
e.g. Bacillus anthracis, B. cereus
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29
Q

Bacillus anthracis

A

infected herbivore carcasses
transmission from handling infected materials (not from eating)
cutaneous lesions
anthrax may also be pulmonary or gastrointestinal
treat with ciprofloxacin or doxycycline

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30
Q

Bacillus cereus

A

foods (e.g. rice)
ingestion of infected foods
self-limiting

31
Q

Clostridium

A 
bacilli
gram positive
anaerobic
Clostridium tetani has terminal spores
C. perfringens is brick-shaped
32
Q

Clostridium perfringens

A

human gut commensal, skin, soil
gas gangrene, intra-abdominal sepsis, anaerobic cellulitis, food poisoning, septicaemia, post-abortion infection
treat with penicillin and clindamycin, and antitoxin

33
Q

Clostridium tetani

A

human and animal gut commensal, soil
spores entering open wounds
causes tetanus
treat with human tetanus immunoglobulin and benzodiazepines

34
Q

Clostridium difficile

A

faecal commensal in neonates and young children
spores via faecal oral route
causes pseudomembranous colitis (diarrhoea following abc therapy)
treat with vancomycin

35
Q

Clostridium botulinum

A

human and animal GI tracts, soil and plants
transmission from food ingestion and wound contamination
causes botulism - descending paralysis secondary to botulinum toxin
treat with vancomycin or metronidazole

36
Q

gram negative bacterial groups

A 
Neisseria
Coliforms (also Enterobacteriaceae)
Parvobacteria
Helicobacter
Vibrio
Pseudomonas
37
Q

Neisseria

A

gram negative diplococci
oxidase positive
aerobic
e.g. Neisseria meningitidis

38
Q

Neisseria meningitidis

A

nasopharynx in 5-20% or general population
transmission: droplets or direction mucosal contact
meningitis
septicaemia with purpuric skin rash
treat with benzylpenicillin or cefotaxime
treat close contacts with rifampicin, ciprofloxacin, or ceftriaxone
vaccine available for some strains

39
Q

Neisseria gonorrhoeae

A

transmission by direct mucosal contact
gonorrhoea, ophthalmia neonatorum, Reiter’s syndrome (urethritis, conjunctivitis, arthritis)
treat with ciprofloxacin or cefixime

40
Q

Coliforms (enterobacteriaceae)

A

gram negative bacilli
E.coli and Klebsiella pneumonia pink colonies on MacConkey agar
Salmonella type, paratyphoid, and enteritis clear colony on MacConkey
aerobic

41
Q

Escherichia coli

A

colonic commensal
faecal-oral route
diarrhoea, UTIs, pneumonia (HAP or neonatal), neonatal meningitis, haemolytic uraemia syndrome (anaemia, thrombocytopenia, oliguria, and renal failure)
treatment depends on site of infection - give trimethoprim for UTI and cephalosporins for pneumonia

42
Q

Klebsiella pneumoniae

A

HAP, UTI, neonatal meningitis (rare)

treat with cephalosporins

43
Q

Proteus mirabilis

A

faecal commensal
UTIs in young females
wound and IV catheter infection
treat with trimethoprim

44
Q

Salmonella typhi and paratyphi (A, B, and C)

A

faecal-oral route
typhoid and paratyphoid (enteric fever)
treat with ciprofloxacin

45
Q

Salmonella enteritidis

A

commensal of animal GI tracts - infection from inadequately cooked food contaminated with animal faeces
gastroenteritis ± bacteraemia
self-limiting

46
Q

Shigella dysenteriae

A

faecal-oral
bacillary dysentery
ciprofloxacin

47
Q

Parvobacteria

A

gram negative bacilli
aerobic
e.g. Haemophilus influensa, Bordatella pertussis, Campylobacter, Legionella pneumophila

48
Q

Haemophilus influenzae

A

type B (Hib) is most pathogenic but is now rare due to vaccine
upper respiratory tract commensal
acute epiglottis, meningitis, osteomyelitis, cellulitis, otitis media, septic arthritis, pneumonia
treat with cefotaxime or ceftriaxone

49
Q

Bordatella pertussis

A

non-commensal
inhalation of airborne droplet
whooping cough
treat with erythromycin

50
Q

Legionella pneumophila

A

warm water
inhalation or aerosolised droplet
Legionnaire’s disease: severe pneumonia and high fever
Pontiac fever: flu-like illness
treat with erythromycin, in severe cases give rifampicin or ciprofloxacin

51
Q

Campylobacter jejune and coli

A 
contaminated poultry or pork or unpasteurised milk 
gastroenteritis ±dysentery 
reactive arthritis
Guillain-Barré syndrome
self-limiting 
if severe, treat with ciprofloxacin
52
Q

Helicobacter

A

curved/spiral bacilli
gram negative
aerobic
e.g. H.pylori

53
Q

Helicobacter pylori

A 
faecal oral route
chronic gastritis 
duodenal and gastric ulcers
increased gastric cancer risk 
treat with clarithromycin and amoxicillin or metronidazole - also with PPI (omeprazole)
54
Q

Vibrio

A

vibrio shaped, gram negative
aerobic
e.g. Vibrio cholerae

55
Q

Vibrio cholerae

A

water, seafood, faecal-oral
cholera: rice water diarrhoea (up to 25 litres of fluid lost per day)
treat with rehydration and ciprofloxacin for severe cases

56
Q

Pseudomonas

A

gram negative bacilli
oxidase positive
aerobic
e.g. P. aeruginosa

57
Q

Pseudomonas aeruginosa

A 
moist environments, fruit and veg, faeces
hand borne and direct contact
pneumonia (esp. in CF pts)
wound, burn, and IV catheter infections
external otitis
folliculitis
UTIs (esp. with catheters)
treat with gentamicin or IV ceftazidime
treat with ciprofloxacin for children with CF and adults with bronchiectasis
58
Q

Chlamydia

A

no distinct bacterial shape
gram negative
intracellular
e.g. Chlamydia trachomatis, C.psittaci

59
Q

Chlamydia trachomatis

A 
mucosal contact
chlamydia
Trachoma: chronic follicular keratoconjunctivitis 
Reiter's syndrome
pelvic inflammatory disease
treat with doxycycline or azithromycin
60
Q

Chlamydia psittaci

A

pigeon fancier’s lung, atypical pneumonia

treat with tetracycline

61
Q

Coxiella

A

no staining - diagnosis by serology
intracellular
e.g. Coxiella burnetti

62
Q

Coxiella burnetti

A

cattle and sheep, inhaled in dust, unpasteurised milk, infected carcasses, droplet spread
Q-fever: flu-like illness, hepatitis ±splenomegaly
treat with tetracycline or doxycycline

63
Q

Rickettsia

A

no staining
intracellular
e.g. R.prowazeki, rickettsii, conorii, typhi, akari
transmission via arthropods (e.g. ticks)
causes typhus
treat with doxycycline, chloramphenicol, or tetracycline

64
Q

mycobacteria

A

acid fast bacilli
ziehl-neelson staining pink/red
Lowenstein-Jensen culture medium (up to 12 weeks)
e.g. M. tuberculosis, M. leprae

65
Q

Mycobacterium tuberculosis/africanum/bovis

A

aerosol droplets
tuberculosis
treatment: rifampicin and isoniazid for 6 months, ethambutol and pyrizinamide for first 2 months

66
Q

Mycobacterium leprae

A

aerosol droplet spread
leprosy
treat with rifampicin and dapsone

67
Q

Treponema

A

spirochaete
no staining
e.g. T. pallidum

68
Q

Treponema pallidum

A

sites of broken mucosa during sexual contact, congenital, blood transfusion
syphilis
treat with penicillin or doxycycline

69
Q

Borrelia

A

spirochaete
no staining
e.g. B. burdorferi

70
Q

Borrelia burdorferi

A

tick bites
Lyme disease
treat with doxycycline

71
Q

Leptospira

A

spirochaete
no staining
e.g. L. interrogans

72
Q

Leptospira interrogans

A

water and animals
open wounds, mucous membranes, conjunctivae
Leptospirosis ranges from fever to Weil’s disease
treat with doxycycline, benzylpenicillin, or amoxicillin

73
Q

Mycoplasma

A

no staining
very small organism without a cell wall
aerobic or facultative anaerobe
e.g. M. pneumoniae

74
Q

Mycoplasma pneumoniae

A 
droplet tranmission 
atypical pneumonia (commonly in young adults)
treat with erythromycin or doxycycline

phase2a medicine (53 decks)

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