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aerobic gram positive rods Flashcards

1
Q

name the aerobic gram positive rods

A 
bacillus spp. (bacillus cereus, bacillus anthracis)
corynebacterium spp. (corynebacterium diphtheriae, c. ulcerans, c. jeikeium, c. minutissimum)
listeria monocytogenes
nocardia asteroides
erisypelothrix rhusopathiae
rhodococcus equi
arcanobacterium haemolyticum
lactobacillus spp.
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2
Q

bacillus cereus: histology

A

large gram positive rods, spores are often visible within the bacterium

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3
Q

bacillus cereus: culture

A

grows well on blood agar aerobically

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4
Q

bacillus cereus: transmission

A

food poisoning (classically fried rice, preformed toxin heat stable)

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5
Q

bacillus cereus: clinical presentations

A

food poisoning:
rapid onset - vomitting
slow onset - diarrhoea and abdominal pain

post traumatic ophthalmitis

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6
Q

bacillus cereus: diagnosis

A

culture from food or stool (most people simply recover)

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7
Q

bacillus cereus: prevention

A

refridgerate cooked rice, cook thoroughly

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8
Q

bacillus anthracis: histology + character

A

large gram positive rods with pink stained capsule (mcfadyean’s stain), spores are often visible within the bacterium

infects animals, especially herbivores

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9
Q

bacillus anthracis: culture

A

grows well on blood agat aerobically

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10
Q

bacillus anthracis: transmission

A

zoonosis: large amounts of resistant spores can live up to years and are releases when an infected animal dies

also carried on animal products like bone meals and hide (bone and skin)

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11
Q

bacillus anthracis: virulence factors

A 
antiphagocytic capsule, made of protein and not polysaccharides
protective antigen
edema factor (toxins)
lethal factor (toxins)
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12
Q

bacillus anthracis: clinical presentations

A

anthrax
cutaneous anthrax: when spores are introduced into skin, forms eschars surrounded by a ring of vesicles and an area of edema
respiratory anthrax: when spores are inhaled, causes severe haemorrhagic infection and pneumonia
intestinal anthrax: when infected animal is ingested, causes haemorrhagic diarrhoea

**note: used in biological warfare

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13
Q

bacillus anthracis: diagnosis

A

culture (blood, vesicle fluid, sputum)

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14
Q

bacillus anthracis: treatment

A

penicillin, ciprofloxacin

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15
Q

corynebacterium diphtheriae: histology + character

A

resembles chinese characters

infects upper respiratory tract, throat, larynx, trachea + skin

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16
Q

corynebacterium diphtheriae: culture

A

tinsdale’s medium, grows as brown colonies with brawn halos

elek plate: precipitin line indicates toxigenic strain

17
Q

corynebacterium diphtheriae: transmission

A

respiratory droplets, spread aided by asymptomatic carriers

18
Q

corynebacterium diphtheriae: virulence factors

A

diphtheria toxin: in bacterium infected by a bacteriophage virus carrying the gene (hence not all strains are toxigenic), enters cell cytoplasm and inactivates elongation factor 2 (EF2) which results in blocking of protein synthesis

19
Q

corynebacterium diphtheriae: clinical presentations

A

diphtheria

local effects of toxin: pseudomembrane formation (dirty white, becomes darker with time); infected area becomes red and swollen - airway obstruction and bullneck where tissues of the neck become very swollen

distant effects of toxin: myocarditis, peripheral neuritis which will lead to weakness or paralysis of muscle groups including the respiratory muscles

20
Q

corynebacterium diphtheriae: diagnosis

A

must be clinical - need for early treatment
culture with selective medium + perform biochemical tests + elek test to check for toxin production (toxigenic strain)
mass spectroscopy

21
Q

corynebacterium diphtheriae: treatment

A

diphtheria antiserum (neutralises the toxin), erythromycin (clears throat carriage)

22
Q

corynebacterium diphtheriae: prevention

A

vaccine (diphtheria toxoid) in national childhood immunisation schedule

23
Q

others - c. ulcerans, c. jeikeium, c. minutissimum: clinical presentations

A

c. ulcerans - throat lesions similar to diphtheria since they produce the same toxin; line associated
c. jeikeium - multi resistant, nosocomial infections
c. minutissimum - erythrasma (fluoresces coral pink under the wood’s lamp), affects the axilla, groin and neck

24
Q

lysteria monocytogenes: histology + character

A

short gram positive rods that could be mistaken for a coccus

cold enhancement (able to multiply even in the cold), intracellular bacteria

25
Q

lysteria monocytogenes: culture

A

beta haemolytic colonies

26
Q

lysteria monocytogenes: transmission

A

food-borne

27
Q

lysteria monocytogenes: clinical presentations

A

infections in pregnancy and neonates: mother may suffer from flu-like illness, abortion or premature labour, neonate may be born dead, severely ill with multisystem involvement or go on to develop early onset listeriosis or late onet meningitis

infections in other patients (typically immunosuppressed):
meningitis
bacteraemia
endocarditis

28
Q

lysteria monocytogenes: diagnosis

A

pregnancy/neonatal - culture: blood, high vaginal swab, amniotic fluid, baby skin swabs
meningitis: culture from csf, blood, typical changes in white cell count and chemistry of csf

29
Q

lysteria monocytogenes: treatment

A

ampicillin with/without gentamicin

*resistant to all cephalosporins

30
Q

norcadia asteroides: histology + character

A

gram positive branching beaded filaments that looks like a chain of cocci but it’s a poor staining rod

found in soil and other environmental sources

31
Q

norcadia asteroides: clinical presentations

A

nosocomial infections (in developed countries): typically in immunocompromised and aids patients, sometimes not so obvious lung infections followed by disseminated infection with abscesses in various organs including brain

non-opportunistic infections (in tropical countries):
madura’s foot - chronic destructive infetion of bone and soft tissues following inoculation into skin with improper footwear

32
Q

norcadia asteroides: diagnosis

A

culture - sputum, pus, blood

33
Q

norcadia asteroides: treatment

A

co-trimoxazole (for months or longer)

34
Q

erysipelothrix rhusopathiae: clinical presentations

A

erysipeloid - cellulitis with blue-red discolouration of skin of fingers typically, especially in those who handle meat/fish/marine animals

35
Q

rhodococcus equi: clinical presentations

A

lung infection in immunocompromised, including aids (acquired from animals)

36
Q

arcanobacterium haemolyticum: clinical presentations

A

unusual cause of sore throat, may be accompanied by skin rash resembling scarlet fever

37
Q

lactobacillus spp.: character

A

normal flora of the oral, gut (probiotics), vagina

*increase in numbers at puberty lowers pH, protective mechanism)

38
Q

lactobacillus spp.: clinical presentations

A

dental caries

microb (12 decks)

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