Micro Flashcards
what bug is this
Neisseria gonorrhea
How does the presentation and epidemiology of pneumonia from mycoplasma pneumoniae differ from that of legionella pneumophila?
In common, they both do not show up well or at all on Gram stain.
Mycoplasma pneumoniae infection causes tracheobronchitis or walking pneumonia. However, symptoms of infection are typically subacute and mild. The presence of high fever and confusion makes an alternate diagnosis far more likely.
Legionella pneumophila infection is typically marked by high fever and fatigue followed by significant gastrointestinal, pulmonary, and constitutional symptoms.
T/F: B cell deficiencies result in recurrent Bacterial infections whereas deficient T cells result in recurrent viral and fungal infections
TRUE
what is cholera toxin
Cholera toxin stimulates adenylate cyclase via activation of Gs → increased cyclic AMP → increased ion (mainly chloride) and water secretion into the intestinal lumen → profuse liquid stools
what is shiga toxin
A toxin produced by Shigella spp., which inhibits the 60S subunit of ribosomes by cleavage of adenine in rRNA (ribosomal RNA). Causes enterocyte damage and bloody diarrhea. Similar to the Shiga-like toxin produced by EHEC (enterohemorrhagic E. coli)
what is an endotoxin
A lipopolysaccharide found in the outer cell membrane of several gram-negative bacteria. Consists of O antigen, a core polysaccharide, and lipid A. Released by living bacteria through membrane blebbing and upon bacterial cell death, inducing host release of IL-1, IL-6, and TNF-α, which cause fever and hypotension leading to septic shock. Can also trigger the coagulation cascade, leading to disseminated intravascular coagulation (DIC).
pertussis toxin
pertussis toxin binds to and activates adenylate cyclase by permanently inhibiting Gi
impairs phagocytosis, allowing the bacteria to survive
Pertussis toxin is responsible for most of the systemic manifestations associated with whooping cough (e.g. hypoglycemia, lymphocytosis, modulation of host immune response).
in what population does Group B strep mostly occur
babies (pneumonia, meningitis, sepsis) mn: B for Babies
it is otherwise a common bacteria of the vagina, so pregnant pts are screened at 35-37 weeks gestation to make sure they don’t have it.
anthrax toxin
an exotoxin consisting of protective antigen,lethal factor,and edema factor
lethal factor mechanism: inactivation of protein kinase signals macrophages to release TNF-alpha –>
tetanus toxin vs botulinum toxin
both tetanus and botulinum toxins (both from clostridium spp) are proteases that cleave the SNARE proteins, a component of the N-ethylmaleimide-sensitive factor attachment protein receptor complex, —> impairs vesicular fusion –> no neurotransmitter released
Tetanospasmin spreads by retrograde axonal transport CNS and blocks release of GABA and glycine in spinal cord –> tetanic paralysis
botulinum toxin inibits ACh release at NMJ
what toxin does C perfringens produce
α-toxin, which is a phospholipase
what’s the pathogen and what infections does it cause
Listeria monocytogenes
Amnionitis, septicemia, and spontaneous abortion in pregnant patients;granulomatosis infantiseptica;meningitis immunocompromised patients,neonates,and older adults;mild,self-limiting gastroenteritis in healthy individuals.
what’s the pathogen and what infections does it cause
Nocardia
pulmonary infections in immunecompromised (pulmonary nocardiosis), cutaneous infections, can spread to CNS causing cerebral abscess
what’s the pathogen and what infections does it cause
actinomyces
oral facial abscesses (a/w cavities or oromaxillary trauma), and PID with IUD use
what’s the pathogen and what infections does it cause
mycobacteria
causes TB
induces release of TNF-alpha and produces sulfatides (prevent phagolysosome fusion)
young pt with fever, severe sore throat, lymphadenopathy, and purulent tonsillar exudates.
what’s the dx?
streptococcal pharyngitis
note the LACK of cough
M protein is found on the surface of what pathogen
Group A Streptococci such as S pyogenes
diptheria toxin
what is the pathogen and what infection(s) does it cause
diphtheria (club shaped gram positive rods)
Diphtheria presents with pharyngitis, cervical adenopathy, low-grade fever, and a characteristic gray-white pseudomembrane. Cardiac involvement can be seen 1 to 2 weeks after the onset of symptoms and can result in potentially life-threatening myocarditis and cardiomyopathy
mn: “i’m gonna dip into the club”
Immunosuppressed patient with ring-enhancing brain lesion and the attached histopath, what’s the dx
Toxoplasma gondii
Toxoplasma is an intracellular protozoan parasite in humans.
Approximately 70% of the population of the United States is seropositive, so reactivation of cysts held in latency by a normal immune response becomes commonplace as the immune response declines.
Cats act as the definitive host of the parasite and shed infectious forms in their feces.
Epstein-Barr virus (EBV). It is characterized by
a positive heterophile test (monospot), fever, pharyngitis, and lymphadenopathy.
Importantly, a monospot would be negative in a patient with CMV infectious mononucleosis. EBV serology can be assessed with tests for the viral capsid antigen (VCA),
which pathogens exhibit Retroviral infection of T cells what what dzs are assoc.
HIV and human T-cell leukemia-lymphoma virus (HTLV), which are associated with non-Hodgkin lymphoma and adult T-cell leukemia/lymphoma, respectively.
which virus is most commonly implicated in myocarditis in an otherwise healthy pt
cocksackie B (mn: the heart (Cardio) is like a Sack (sack-)
this is also responsible for pericarditis which is even more so like a sack
what’s the pathogen
branching septate hyphae at a narrow angle –> Aspergillus (fungi)
opportunistic fungal infection a/w immunocompromised individuals, those with chronic ganulomatous dz (neutrophil dysfunction)
positive heterophile antibody test indicates what pathogen
EBV
“eosinophilic intranuclear inclusion bodies and multinucleated giant cells visible on Tzanck smear of epithelial cells”. what type of infection does this describe
HSV type 1
______________ is the only pathogenic fungus that has a polysaccharide capsule. The capsule appears red on mucicarmine stain and as a clear unstained zone with India ink
Cryptococcus neoformans is the only pathogenic fungus that has a polysaccharide capsule. The capsule appears red on mucicarmine stain and as a clear unstained zone with India ink
__________________ is the most common etiologic agent in subacute bacterial endocarditis following dental work.
S viridans
__________ is part of the normal flora of the colon, and bacteremia or endocarditis caused by it is associated with colonic cancer in ~25% of cases.
S gallolyticus (formerly S. Bovis)
what’s the pathogen?
roundworm (ascaris lumbricoides)
what are the cephalosporin resistant organisms (mn: LAME)
Listereria Monocytogenes
Atypicals (mycoplasma, Chlamydia) (b/c no cell wall)
MRSA
Enterococci
what’s the pathogen
Coccidioides Immitis
mn: the shape of the particples inside are like a bunch of little Cs and there’s 3 Cs in Coccidiodes
what’s the pathogen
aspergillus (branching at 45 degrees pathognomonic)
commonly causes pulmonary dz in immunocompromised pts
has only one form (mold) as pictured
what’s the pathogen
what’s the pathogen
blastomyces dermatitidis
“round yeast with broad-based budding. These yeasts have thick, doubly refractive walls.”
what’s the pathogen
cryptococcus neoformans
“yeast with a thick capsule and clear halo on india ink”
a/w meningitis among immunocompromised
mn: thick capsule = deep within the crypt
what’s the pathogen
CMV
“prominent intranuclear inclusions surrounded by a clear halo”
what’s the pathogen
histoplasmosis capsulatum
“small oval yeast within macrophages”
n.b differentiated from coccidiodes (bottom photo) by the fact that they are NOT spheres
what’s the pathogen
Rhizopus (mucormycosis)
typically cause rhino-orbito-cerebral mucormycosis but can cause lung disease in immunocompromised patients
what’s the pathogen
This peripheral blood smear comes from a patient with malaria. This infection happens to be with Plasmodium vivax. At the arrow is a RBC with a malarial parasite in the shape of a ring. Three other RBC’s in this smear are also infected with a ring trophozoite.
T or F: you don’t get postherpetic neuralgia with HSV
TRUE, only with VZV (ch/by painful vesicular rash in dermatomal pattern
What’s the pathogen
acute phase of Trypanosoma cruzi from the triatomine bug (endemic in latin america) –> causes Chagas dz
Chagas disease is divided into 2 phases:
The acute phase (8-12 weeks after transmission) is characterized by circulating trypomastigotes that are detectable on blood microscopy. Most patients are asymptomatic, but a minority develop nonspecific symptoms (eg, fever, malaise, anorexia) and inflammation/swelling at the site of inoculation (eg, eye swelling following conjunctival inoculation).
The chronic phase begins when the immune system eliminates circulating parasitemia, leading to resolution of acute symptoms. Patients subsequently develop a prolonged asymptomatic phase (“indeterminate form”), whereby serology is positive for T cruzi, but there are no symptoms, signs, detectable parasitemia, or indications of end-organ damage. After 1-3 decades, a minority of those with asymptomatic chronic infection develop end-organ disease of the heart or gastrointestinal system.
Chronic Chagas cardiomyopathy is the most common complication of Chagas disease. It is thought to be caused by chronic, low-grade, parasite-mediated myocarditis, which leads to the progressive destruction of cardiac fibers and subsequent cardiac fibrosis. Common complications include biventricular heart failure, cardiac arrhythmias (particularly ventricular arrhythmias), and ventricular aneurysm with intracardiac thrombus (leads to thromboembolic disease/stroke).
what is the MOA of Shiga toxin
Shiga-like toxins inhibit 28S on the 60S ribosome subunit and disrupt cellular protein synthesis. –> effacement of enterocyte microvilli and apoptosis of enterocytes
This is the type of ecoli in EHEC (bloody diarrhea)
what is the pathogenicity of uropathogenic E. Coli
Uropathogenic E coli (UPEC) use a special kind of fimbriae called P pili to attach to the urinary tract and create a biofilm to evade immunologic recognition and eradication. In addition, they use hemolysin to invade tissues and move up the urinary tract to cause anything from cystitis to pyelonephritis as the bacteria advance.
what is the mechanism of pathogenicity of the type of E. Coli that causes neonatal meningitis
The most common gram-negative bacteria to cause neonatal meningitis is E coli. Strains with the K1 capsule cause the majority of the infections, and this is due to their ability to bind to neuroreceptors that have higher affinities for the K1 capsule. This allows the E coli to penetrate the blood-brain barrier, resulting in colonization and infections such as meningitis.
They inhibit phagocytosis and complement mediated lysis
what is the mechanism of pathogenicity of ETEC (travelers diarrhea
Enterotoxigenic E coli (ETEC) use fimbriae to attach to the brush border of the small intestines, causing what is commonly known as traveler’s diarrhea. Once attached, ETEC release two types of enterotoxins: heat labile (cAMP-inducing toxin) and heat-stable (cGMP-inducing toxin). Both alter the enzyme cascades in intestinal cells, resulting in increased cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). This results in hypermotility of the small intestine and the increased release of water and electrolytes, leading to diarrhea (Figure 5). ETEC do not invade intestinal cells and cause noninflammatory diarrhea.
oval, budding yeast with pseudohyphae and branching at right angles describes what pathogen
candida
vs mucor/rhizopus which also branch at right angles, but do not have budding and are stained with color.
pt with pneumonia sx and this lung biopsy stain
what’s the pathogen
pneomocystis jirovecii causing causes Pneumocystis pneumonia
which pathogens are a/w dental carries
strep mutans and strep mitis (viridans sp)
mn: d for dental and Dextrans (which facilitates binding to tooth enamel and formation of fibrin-plt deposits on heart valves
what pathogens are a/w keratitis from contact lens use
Pseudomonas aeruginosa is the most common cause of bacterial keratitis in contact lens users (> 60% of cases)
but also, staph
which pathogens produce IgA protease (virulence factor)
S. pneumoniae, H. influenzae, and Neisseria spp
which pathogen is most a/w sepsis and circulatory collapse (e.g. DIC) in previoulsy healthy young individuals
N. Meningitidis (d/t lipo-oligosacharride in cell wall = virulence factor)
which one is amebiasis
which one is giardia
top = Entamoeba histolytica (amebiasis) –> bloody diarrhea with incubation period of 1-4 weeks
bottom = giardia –> non-bloody diarrhea, with incubation period of 1-2 weeks
bloody diarrhea in absence of fecal leukocytes is suggestive of what etiology
amebiasis (because these organisms destroy leukocytes)
chief sx in infection with Entamoeba histolytica
Entamoeba histolytica is an amoeba that causes colitis characterized by trophozoites and flask-shaped ulcers on biopsy. It can occasionally (~1%) invade the colonic wall and disseminate through the blood to the liver, brain, or lungs. A single amebic liver abscess is the most common extraintestinal manifestation.
