aerobic gram positive rods Flashcards
name the aerobic gram positive rods
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.
bacillus cereus: histology
large gram positive rods, spores are often visible within the bacterium
bacillus cereus: culture
grows well on blood agar aerobically
bacillus cereus: transmission
food poisoning (classically fried rice, preformed toxin heat stable)
bacillus cereus: clinical presentations
food poisoning:
rapid onset - vomitting
slow onset - diarrhoea and abdominal pain
post traumatic ophthalmitis
bacillus cereus: diagnosis
culture from food or stool (most people simply recover)
bacillus cereus: prevention
refridgerate cooked rice, cook thoroughly
bacillus anthracis: histology + character
large gram positive rods with pink stained capsule (mcfadyean’s stain), spores are often visible within the bacterium
infects animals, especially herbivores
bacillus anthracis: culture
grows well on blood agat aerobically
bacillus anthracis: transmission
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)
bacillus anthracis: virulence factors
antiphagocytic capsule, made of protein and not polysaccharides protective antigen edema factor (toxins) lethal factor (toxins)
bacillus anthracis: clinical presentations
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
bacillus anthracis: diagnosis
culture (blood, vesicle fluid, sputum)
bacillus anthracis: treatment
penicillin, ciprofloxacin
corynebacterium diphtheriae: histology + character
resembles chinese characters
infects upper respiratory tract, throat, larynx, trachea + skin
corynebacterium diphtheriae: culture
tinsdale’s medium, grows as brown colonies with brawn halos
elek plate: precipitin line indicates toxigenic strain
corynebacterium diphtheriae: transmission
respiratory droplets, spread aided by asymptomatic carriers
corynebacterium diphtheriae: virulence factors
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
corynebacterium diphtheriae: clinical presentations
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
corynebacterium diphtheriae: diagnosis
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
corynebacterium diphtheriae: treatment
diphtheria antiserum (neutralises the toxin), erythromycin (clears throat carriage)
corynebacterium diphtheriae: prevention
vaccine (diphtheria toxoid) in national childhood immunisation schedule
others - c. ulcerans, c. jeikeium, c. minutissimum: clinical presentations
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
lysteria monocytogenes: histology + character
short gram positive rods that could be mistaken for a coccus
cold enhancement (able to multiply even in the cold), intracellular bacteria
lysteria monocytogenes: culture
beta haemolytic colonies
lysteria monocytogenes: transmission
food-borne
lysteria monocytogenes: clinical presentations
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
lysteria monocytogenes: diagnosis
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
lysteria monocytogenes: treatment
ampicillin with/without gentamicin
*resistant to all cephalosporins
norcadia asteroides: histology + character
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
norcadia asteroides: clinical presentations
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
norcadia asteroides: diagnosis
culture - sputum, pus, blood
norcadia asteroides: treatment
co-trimoxazole (for months or longer)
erysipelothrix rhusopathiae: clinical presentations
erysipeloid - cellulitis with blue-red discolouration of skin of fingers typically, especially in those who handle meat/fish/marine animals
rhodococcus equi: clinical presentations
lung infection in immunocompromised, including aids (acquired from animals)
arcanobacterium haemolyticum: clinical presentations
unusual cause of sore throat, may be accompanied by skin rash resembling scarlet fever
lactobacillus spp.: character
normal flora of the oral, gut (probiotics), vagina
*increase in numbers at puberty lowers pH, protective mechanism)
lactobacillus spp.: clinical presentations
dental caries
