Bacteria (Part II) Flashcards
What is the alpha-hemolytic encapsulated gram-positive bacteria?
streptococcus pneumoniae
how is streptococcus pneumoniae typically seen?
as diplococci or short chains
where does streptococcus pneumoniae colonize?
in the nasopharynx
what is the purpose of the capsule in streptococcus pneumoniae?
it provides a level of defense against direct phagocytosis by macrophages and inhibits complement activation
how can the swollen capsule of streptococcus pneumoniae be seen?
by the addition of the anti-capsular antibodies, which is the basis for the quelling test
what is streptococcus pneumoniae sensitive for?
optochin
what is the virulence factor for streptococcus pneumoniae?
IgA protease
what is so significant about streptococcus pneumoniae/ what does streptococcus pneumoniae cause?
it is the most common cause of community acquired PNA
how does PNA caused by streptococcus pneumoniae present?
lobar consolidative pattern where the entire lung lobe is involved with the pneumonic process with high fever, cough, SOB and chest pain
who is most at risk for streptococcus pneumoniae PNA?
elderly (older than 65)
what are the risk factors associated with getting streptococcus pneumoniae PNA?
COPD, smoking, previous influenza infection, immunocompromise, asplenia
What diseases can streptococcus pneumoniae cause?
pneumococcal PNA, meningitis, otitis media
what is the number 1 cause of meningitis in young children?
streptococcal pneumoniae
what is the classic triad of meningitis caused by streptococcus pneumoniae?
high fever, nuchal rigidity, and abnormal mental status change
what is the most common cause of meningitis in neonates?
streptococcus agalactiae, Escherichia coli, and listeria monocytogenes
what is the most common cause of meningitis in adolescence and very young adulthood?
Neisseria meningitides
What are the most common bacterial causes of otitis media?
streptococcus pneumoniae, Haemophilus influenzae, and moraxella catarrhalis
what is the only gram positive bacteria that commonly causes otitis media?
streptococcus pneumoniae
what are encapsulated bacteria cleared by?
the spleen
encapsulated bacteria can cause severe disease in asplenic patients. What are the top 3 encapsulated bacteria to remeber?
streptococcus pneumoniae, haemophilus influenza (type B), and Neisseria meningitis
what can cause asplenia or hyposplenism?
trauma, neoplasia or other disorders such as sickle cell anemia where entrapment of RBCs by the spleen leads to splenic infarction
where do the viridans group streptococci colonize?
gastrointestinal tract and the oral cavity
what diseases do the viridans group streptococci cause?
dental caries (cavities), subacute bacterial endocarditis, abscess in the brain and liver
What is the most well known member of the viridans group to cause dental caries?
streptococcus mutans
what is the most well known member of the viridans group to cause various abscesses (typically in the immunodeficient)?
streptococcus anginosus
what are the symptoms associated with the subacute endocarditis caused by viridans group streptococci?
insidious onset of low grade fevers, weakness, night sweats, loss of appetite, and weight loss
what is a typical clinical history of someone with a subacute endocarditis caused by viridans group streptococci?
endocarditis following an invasive dental procedure which allows the organisms to spread hematogenously to the heart valves
besides the viridans group streptococci, what is another cause of subacute bacterial endocarditis?
the HACEK organism (mouth colonizers)
what do enterococci appear morphologically similar to?
streptococci on gram stain (they appear as gram positive cocci in chains)
what are the enterococci part of (normal)?
normal bowel flora and nosocomial infections which are essentially hospital based opportunistic infections
what do enterococci grow on?
bile and 6.5% NaCl (salt)
what are the most important members of the normal bowel flora? (2)
Enterococci faecalis and enterococci facium
what diseases do enterococci cause?
wound infections, urinary tract infections, biliary tract infections, subacute endocarditis
what does the group D non-enterococci grow on?
bile but not 6.5% NaCl (salt)
what is the most important member of the group D non-enterococci group?
streptococcus bovis
what is streptococcus bovis strongly associated with?
colon cancer
what are the two major oxygen loving (aerobic) species in the spore-forming gram positive bacilli group?
Bacillus cereus and bacillus anthracis
what is bacillus cereus responsible for?
diarrheal illness
what is bacillus anthracis responsible for?
anthrax
what are 4 anaerobic clostridium species in the spore-forming gram positive bacilli group?
clostridium difficile, clostridium botulinum, clostridium tetani, and clostridium perfringens
what is a special characteristic of bacillus cereus?
the spores are extremely heat resistant- it can persist despite being exposed to cooking temperatures
what happens once bacillus cereus contaminates food?
the spores germinate within the food to create bacterial forms which then can elaborate enterotoxins
what is one of the enterotoxins created once the bacillus cereus spores germinate?
heat stabile toxin- it is not neutralized through simple reheating
what is the disease caused by heat stabile toxin?
emetic disease: nausea/vomiting, abdominal cramps within 1-3 hours of toxin ingestion
what is a classic example of a food contaminated with bacillus cereus?
reheated rice
besides the heat stabile toxin, bacillus cereus can also release what other toxin? and what does this toxin cause?
heat labile toxin; causes diarrheal disease: watery diarrhea, nausea, abdominal cramps
how is the diarrheal toxin released by bacillus cereus different from the emetic toxin?
the diarrheal toxin is heat labile and a had a longer incubation period (of at least 8 hours)
what are the spores of bacillus anthracis resistant to?
environmental changes such as drying, heating, and chemicals
where are spores of bacillus anthracis found?
on herbivore animals/products (hides) and in soil
what are the virulence factors associated with bacillus anthracis?
plasmid encoded: (pX01, pX02)
what is a person who handles herbivore animals/products skins contaminated with bacillus anthracis at risk for?
the development of cutaneous anthrax
how does cutaneous anthrax begin?
it starts as a localized disease, with a black ulcerated necrotic lesion termed “malignant pustule”
what happens if cutaneous anthrax is not treated?
more widespread infection can occur with systemic signs (painful lymphadenopathy and edema), which can lead to death
what are the other forms of anthrax? (not cutaneous anthrax)
inhalational anthrax, gastrointestinal anthrax, and injectional anthrax
what occurs with inhalational anthrax?
a spore is inhaled, and it remains latent in the lower airways where macrophages ingest and transport them to the mediastinal lymph nodes. There can be a prolonged latent period (> 2 months); symptoms like fever and myalgia occur first but within 3 days there is mediastinal hemorrhage followed by respiratory failure and sepsis
what is a key finding of inhalational anthrax?
mediastinal widening due to the mediastinal hemorrhage (can be seen on chest x ray)
what are all clostridium species?
gram positive, anaerobic spore forming rods
what is clostridium difficile the causative organism of?
antibiotic associated colitis
why does clostridium difficile infection usually follow a course of antibiotics?
antibiotics kill the normal gastrointestinal flora which makes it easier for C diff to cause infection because it no longer has to compete with the normal flora
how is c. difficile infection caused?
bacterial spores through fecal oral contamination
what are the virulence factors associated with c difficile?
Toxin A and Toxin B
what are the effects of toxin A released from c. difficile?
increase in inflammation and fluid secretion (diarrhea)
what are the effects of toxin B released from c difficile?
cytotoxic to colonic epithelial cells
what is the disease associated with c difficile?
non-bloody diarrhea, abdominal pain, and fever
what are the pathological key findings associated with c difficile?
pseudomembranous colitis- a colitis which grossly shows exudative yellowish colonic plaques
how can c difficile be detected?
through nucleic acid testing or detection of its toxins in the stool
what can clostridium botulinum spores contaminate?
food
what happens when clostridium botulinum grows from the spores that are on food?
it elaborates a neurotoxin, which causes botulism
what are the classic examples of food products that cause botulism?
poorly performed at-home canned food, smoked fish, and raw HONEY
what is the effect of the neurotoxin that is released from C. botulinum?
it inhibits the release of acetylcholine at the neuromuscular junction blocking the cholinergic neuromuscular innervation of both striated and smooth muscle
what happens when the neurotoxin that is released by C. botulinum is ingested by the adult?
bilateral cranial neuropathies and descending muscle weakness can occur which can ultimately lead to respiratory paralysis and death
how does infantile botulism present?
with constipation which progresses in a couple of days to difficulty swallowing and muscle weakness; generalized hypotonia can occur giving rise to “floppy baby syndrome”
how do infants get botulism?
consumption of spores from honey and infant powder
where is clostridium tetani found?
in soil everywhere
what is clostridium tetani associated with?
deep puncture wounds
what is clostridium tetani notable for producing?
a potent neurotoxin which inactivates glycine and GABA causing sustained muscle contraction
what is the result of the neurotoxin released by clostridium tetani?
severe muscle spasms, autonomic instability, risus saronicus, lockjaw, opisthotonos
how does autonomic instability present?
sweating, tachycardia, labile blood pressure (both hyper and hypotension)
what is opisthotonos?
arching of head, neck, and spine/body
where are clostridium perfringens spores found? and what can they contaminate?
in soil–> they can contaminate deep wounds/ trauma
what does clostridium perfringens cause?
gas gangrene (essentially starts as a cellulitis that can progress to myonecrosis which is necrosis of the muscle)
what is one clue to the diagnosis of clostridium perfringens in less obvious cases?
on palpation, one can often reveal crackling as there are small pockets of gas trapped in the tissue (this is crepitus)
what do the virulence factors released by clostridium perfringens cause?
hemolysis and hemorrhage
historically, gas gangrene was seen in when?
in World War I and II
if there is clostridial perfringes food contamination, what occurs?
diarrhea, abdominal cramps, necrotizing enteritis (super rare)
what is corynebacterium diphtheriae notable for?
it shape- namely that of a pleomorphic club shaped rod
what is corynebacterium diphtheriae cultured on for identification?
specialized media (Loeffler’s medium)
what virulence factors does corynebacterium diphtheriae produce?
an AB exotoxin
what are the nonspecific manifestations seen with corynebacterium disease?
fever, headache, malaise, cough, adenopathy
what is the key finding of corynebacterium disease? aka the key effect of AB toxin
pharyngitis with pseudomembrane formation (yellow/gray inflammatory exudate–> DO NOT SCRAPE, will cause a systemic absorption of toxin)
with systemic absorption, what does AB toxin affect?
the heart and nerves–> leads to myocarditis (dysrhythmias, AV conduction block) and neural involvement (cranial and peripheral nerve palsies)
what is rhodococcus equi?
a gram positive, partially acid fast pleomorphic clubbed rod, facultative intracellular bacteria
where is rhodococcus equi found?
in a variety of mammals, manure, soil
what does rhodococcus equi cause?
pulmonary disease in the immunocompromised and it can cause abscess cavities with prominent air fluid levels on chest x-ray
what might a chest x-ray look like of a person infected with rhodococcus equi?
upper lung nodules and cavities with air-fluid levels
what is listeria monocytogenes?
a gram positive anaerobic intracellular facultative anaerobic rod; grows at cooler temperatures
where is listeria monocytogenes found?
in contaminated dairy products (milk, soft cheeses), meat (deli and hot dogs), sprouts
who is at risk for getting listeria monocytogenes?
pregnant women–> there is a high risk of infection of baby
what does listeria monocytogenes cause in the healthy?
mild influenza-like illness often with an acute self-limited gastroenteritis termed Listeriosis
what does listeria monocytogenes infection cause in the fetus and neonate? (2)
1) widespread granulomatous infantiseptica (often fatal results in stillbirth) 2) Neonatal meningitis with septicemia via fecal contamination (occurs later like 2-3 weeks after birth)
Like group B strep, listeria monocytogenes can also cause what?
sepsis in the mother
what effect does listeria monocytogenes have on older adults and the immunocompromised, including those that are taking immunosuppressive medicines like corticosteroids?
meningitis
What are the three gram negative diplococci?
neisseria meningitis, neisseria gonorrhea, and moraxella cararrhalis
how can the gram negative diplococci be grown?
on heat lysed blood agar termed “chocolate agar”
what is the Thayer-Martin or VPN agar plate?
the vancomycin, polymyxin, and nystatin plate- it selects for neisseria growth only
where does neisseria meningitis colonize?
in the nasopharynx
What are the major virulence factors of N. meningitis?
a capsule, IgA protease, and pili; it also contains an endotoxin on its outer cell membrane- LPS
what are the susceptible populations for neisseria meningitis infection?
neonates (1/2-2 years), military recruits, college students (dorms), and asplenia/hyposplenia patients
what diseases can be caused by neisseria meningitis?
meningitis and meningococcemia
what is meningococcemia?
meningitis+ septicemia
what does meningococcemia cause?
waterhouse-friderichsen syndrome
what is waterhouse-friderichsen syndrome?
bilateral adrenal hemorrhage with insufficiency, severe hypotension, disseminated intravascular thrombosis, death
what is neisseria gonorrhoeae?
facultative anaerobic and facultative intracellular gram negative diplococci
what is the second most common bacterial sexually transmitted disease? And what is it behind
neisseria gonorrhoeae; behind chlamydia
what are the virulence factors of neisseria gonorrhoeae?
IgA1 protease, pili, opa proteins
what is the purpose of the pili virulence factor?
it allows the organism to adhere to non-ciliated cells
What diseases does neisseria gonorrhoeae cause in men?
urethritis and acute epididymitis
what are the symptoms of urethritis in men?
discharge and dysuria
what are the symptoms of acute epididymitis in men?
posterior testicular pain and swelling
what diseases does neisseria gonorrhoeae cause in women?
urethritis, cervicitis, pelvic inflammatory disease and perihepatitis
what are the symptoms of urethritis in women?
typically asymptomatic, if there are any symptoms it would be dysuria
what are the symptoms of cervicitis?
typically asymptomatic, but if there are symptoms it will be itching and discharge
what is pelvic inflammatory disease?
infection of the uterus, fallopian tubes, ovaries–> can cause sterility, can present with pelvic/abdominal pain
in some women, neisseria gonorrhoeae affects the liver- how so?
perihepatitis (Fitz-Hugh-Curtis syndrome): inflammation of the liver capsule; presents as sharp right upper quadrant pleuritic pain
how does neisseria gonorrhoeae affect both men and women?
disseminated gonococcal infection–> septic arthritis
how does neisseria gonorrhoeae affect infants?
ophthalmia neonatorum–> neonatal conjunctivitis
what is moraxella catarrhalis?
a gram negative aerobic diplococcus
what is the most common disease caused by moraxella catarrhalis?
otitis media
Besides otitis media, what is another disease that can be caused by moraxella catarrhalis, and who is susceptible to this disease?
can cause bronchopneumonia in elderly patients
what are the gram negative enteric bacteria? (description)
a very diverse group of pathogenic bacteria; many enterics are bacteria that arise from the gastrointestinal tract to cause disease
what is the broad breakdown of the enterics? (list 4)
the enterobacteriaceae, the pseudomonadaceae, the bacteriodaceae, the vibrionaceae
what is the effect when a pathogenic organism involves the intestine, but does not invade the bowel wall?
it causes watery diarrhea
what is the effect when bacteria invades the intestinal epithelium?
direct epithelial cell death can result–> causes bloody diarrhea
what are 2 examples of organisms that cause watery diarrhea (lack of invasion)?
enterotoxigenic E. coli and Vibrio cholera
what are 3 examples of organisms that can cause intestinal epithelium invasion/death leading to fever, bloody diarrhea, and abdominal cramps?
enterohemorrhagic and enteroinvasive E. coli and Shigella
what happens when the bacteria invade the lymph nodes and get into the blood stream?
bloody diarrhea can occur as well as fever and abdominal pain; ultimately if bacteria enter the blood stream, bacteremia with sepsis can occur
what are 3 examples of organisms that can cause invasion into the lymph nodes and blood stream?
salmonella typhi, yersinia enterocolitica, and campylobacter jejuni
