Transcript Spore Forming and Non-Spore Forming Gram

Spore Forming and Non-Spore
Forming Gram-positive Bacilli
SBM 2044
Medical Microbiology
Second year UG of BBiomedic Sc
Spores
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Why do bacteria produce spores?
Survival
Classification
Definition = a resting cell, highly resistant
to dessication, heat, and chemical agents;
when returned to favourable conditions
bacteria re-activated, the spores
germinate to produce single vegetative
cells.
SF Bacteria- Bacillus
• Aerobic, G+ rods in chains, spores are located in
center of the non-motile bacilli
• Found in soil, water, air and vegetation
• Spores are viable for decades.
• B. cereus – produce enterotoxin and cause food
poisoning.
• B. anthracis – infection in human through injured
skin (cutaneous anthrax), mucous membranes
(GI anthrax), or inhalation of spores into lung.
Bacillus anthracis
SF Bacteria- Bacillus
• Spores germinate in the tissue of entry,
and growth of vegetative organisms result
in formation of a gelatinous oedema and
congestion.
• Spread via lymphatics to bloodstream and
multiply freely in blood and tissues.
• Capsulated, poly-D-glutamic acid capsule
is antiphagocytic
SF Bacteria- Bacillus
• Anthrax toxin is made up of three proteins:
• Protective antigen (PA), edema factor (EF)
and lethal factor (LF).
• Treatment: ciprofloxacin, penicillin G along
with gentamicin and streptomycin.
SF Bacteria - Clostridium
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Anaerobic, G+, motile rods
Many decompose proteins of form toxins.
Found in soil, animal faeces.
Spores is placed centrally, subterminally or
terminally; most species are motile with
flagella.
SF Bacteria - Clostridium
• Many form colonies with a zone of haemolysis
on blood agar. C perfringens typically produce
multiple zones of haemolysis around colonies.
SF Bacteria - Clostridium
• C botulinum causes botulism
• -Distinguished by antigenic type of toxin
• Spores are resistant to 100C for many hours,
diminished at acid pH or high salt.
• Toxin - 7 antigenic varieties (A →G). A, B, E (F)
mainly harmful to human.
• Botulinum toxin is absorbed from gut and binds
to receptors of presynaptic nervous system and
cranial nerves.
• Lethal dose to human 1-2 µg.
SF Bacteria - Clostridium
• Pathogenesis
• Most cases, through ingestion of uncooked
food.
• Toxin acts by blocking release of acetylcholine
at synapses and neuromuscular junctions →
flacid paralysis.
• Symptoms such as visual disturbances,
inability to swallow, speech problem; seldom
with no apparent GI symptoms; no fever.
SF Bacteria - Clostridium
• ‘floppy baby’ = infant botulism. C botulinum
spores in babies’ food.
• Treatment – antitoxins raised in horses.
• Trivalent (A, B, E) antitoxin must be promptly
administered intravenously with precautions;
plus adequate ventilations.
SF Bacteria - Clostridium
• Clostridium tetani cause tetanus.
• Distinguishable by specific flagellar antigens.
• Toxin binds to receptors on the presynaptic
membranes of motor neurons.
NSF bacteria
• Generally, members of normal flora of skin and
mucous membranes of humans.
Aerobic G+ with High
G+C content,
irregularly shaped
Corynebacterium
Propionibacterium
Actinomyces
Rhodococcus
Aerobic G+ with lower
G+C content,
regularly shaped
Listeria
Lactobacillus
Clostridium
Bacillus
Corynebacterium diphtheriae
• Infects nasopharynx or skin
• Mostly grow aerobically, non-motile
• Irregular swellings/clubbed-shaped; granules
within rod stained with aniline dyes.
Corynebacterium diphtheriae
• Blood agar+potassium tellurite, tellurite is
reduced intracellularly
Corynebacterium diphtheriae
• In respiratory wounds, skin of infected
person; spread by droplets or contact to
susceptible individuals
• Diphtheria toxin (Dt) is a heat-labile
Inhibits polypeptide chain
elongation, by inactivating EF2 (with NAD)
This abrupt arrest of protein
synthesis results in necrotizing
and neurotoxic effects of Dt.
Transporting A into
cell
Corynebacterium diphtheriae
• Pathogenesis is based upon: (1) the ability of a
given strain of C diphtheriae to colonize in the
nasopharyngeal cavity and/or on the skin, and
(2) its ability to produce diphtheria toxin.
• Pathology: Dt absorbed into mucous
membranes, causing destruction of epith and
superficial inflammatory response. Necrotic
epith embedded in exuding fibrin+RBC+WBC=
grayish “pseudomembrane”
• Disease is principally result of the action of toxin
formed rather than invasion by the organism
Corynebacterium diphtheriae
• Vaccination confers protection against disease
by production of antibodies to the diphtheria
toxin. The vaccine is produced from purified
inactivated toxin from a strain of C. diphtheriae.
• Diphtheriae antitoxin (DTP) administered to
infants, and followed by boosters.
• Treatment rapid suppression of toxin-producing
bacteria by antimicrobial drugs at the earliest
diagnosis of diphtheria.
Listeria monocytogenes
• Small/Short, G+,peritrichous flagella, rod. Grow
on Mueller-Hinton agar (better in sheep bloodsmall zone of haemolysis); facultative anaerobe,
motile at room temp, catalase +
• Listeriosis results from ingestion of contaminated
food such as cheese and vegie; primarily affects
pregnant women, newborns, those with
weakened immune system.
• Able to multiply at low temp,
hence accumulate in contaminated food stored in refrigerator.
Steps in the invasion
of cells and
intracellular spread by
L. monocytogenes.
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The bacterium apparently invades via the intestinal mucosa. It is thought to attach to
intestinal cells by means of D-galactose residues on the bacterial surface which adhere to
D-galactose receptors on susceptible intestinal cells The bacterium is taken up by induced
phagocytosis, which is thought to be mediated by a membrane associated protein called
internalin. Once ingested the bacterium produces listeriolysin to escape from the
phagosome. The bacterium then multiplies rapidly in the cytoplasm and moves through the
cytoplasm to invade adjacent cells by polymerizing actin to form long tails.
Actinomycetes
• Form chains or filaments, facultative
anaerobes (+CO2)
• Actinomycosis is a chronic suppurative
and granulomatous infection that produces
pyogenic lesions with interconnecting
sinus tracts that contain granules. Most
cases due to A israelii, A naeslundii.
• Commonly affecting cervicofacial, thoracic
and abdominal actinomycosis.
References
• http://textbookofbacteriology.net/
• http://www.gsbs.utmb.edu/microbook/
• Brooks’ Jawetz Medical Microbiology
• Puan Intan Azura Shahdan
• Room F2/A/2/73
Pseudomonad, Pasteurella
• Pasteurella – short G- rods with bipolar
staining. Animals are their natural hosts in
most cases.
Vibrios
Helicobacter pylori
Gram-positive
Cocci
Bacilli
F=fastidious, SF=spore-forming
Gram-negative