micro Flashcards
woman with a painful vaginal ulcer and bilateral inguinal lymphadenopathy. negative tzanck and VDRL.
dx and tx?
haemophilus ducreyi, chancroid
tx - ceftriaxone or azithromhcin
virus with the leading risk for developing hepatocellular carcinoma?
hepatitis b
kaposi sarcoma belongs go which viral family?
hhv 8
herpes viruses incl hsv1 hsv2 and roseola (hhv6), EBV, CMV, and varicella
CSF for bacterial meningitis will have what characteristics?
high opening pressure
high protein
pleocytosis with PMN predominance
low glucose
previously healthy pt with a history significant only for mitral valve prolapse presenting with endocarditis like symptoms
strep viridans:
s. mutans
s. sanguinis
s. oralis
s. mitis
tx for hhv8?
alpha interferon
oxidasd negative motile GNR that is beta hemolytic on macconkey agar but light green with black centers on hektoen agar
salmonella
pt with new palpitations, chest pain, systolic murmur (mitral regurg), elevated cardiac enzymes. bx would show diffuse myocardial defeneration and necrosis with inflammatory infiltrate
cozsackie virus
naked ssrna
h. pylori infection is a risk factor for?
gastric adenocaecinoma and b-cell hodgkin gastric lymphoma (AKA MALT lymphoma)
most h. pylori infections are asymptomatic (not manifesting as PUD in the majority)
what PPE is recommended in a ptmwith c. diff?
non sterile gloves and gown
also must use soap and water to wash hands. alcohol based sanitizer is not sufficient
a pt with chronic granulomatous dz are at increased risk of infection with organisms with which feature?
catalase positive organisms
pt is NADPH osidase deficient
s. aureus, burkholderia cepacia, serratia, nocardia, aspergillus
what is burkholderia cepacia?
catalase positive, non lactose fermenter, gram neg cocobaccilli
opportunistic pathogen causing pneumonia in immune compromised hosts(cf, cgd)
a pt presents with mycoplasma pneumonia and anemia. he is given azithromhcin and both symptoms improve. why?
m. pneumoniae can cause intravascular hemolytic anemia due to similar Ags and cold agglutinins. the anemia resolves when the cold agglutinin IgM levels lower.
m. pneumo is also associated with stevens-johnson syndrome, arthralgia, encephalitis, arrythmia, and bullous myringitis
an infant presents to the er following a seizure and a 12 hour history of fever. 3 days after discharge she develops a maculopapular rassh on her trunk. dx?
roseola (hhv6)
the key is a high fever followed by a maculopapular rash on the trunk 3-5 days later
tx = supportive
unvaccinated kid presents with fever, runny nose, cough, bilateral conjunctival injection, and small white spots with erythematous base on buccal mucosa. dx and likely to develop what additional symptom?
rubeola (measles)
maculopapular rash
a pt with a history of smoking and alcohol abuse presents with malaise and cough with 2 month duration. yellow sputum with streaks of blood. poor dentition, ginivitis, and large submandibular nodes. ronchi in right upper lobe.
actinomycosis
systemic infection occurs when mucosa is disrupted (poor dentition)
pulmonary actinmycosis can follow aspiration.
dx - filamentous branching pattern
tx -penicillin
a kid presenting with epiglottitis probably has what in his history?
missed his H. flu vaccine.
presence of pyrrolidonyl arylamidase is associated with?
Strep pyogenes
PYR positive
pt on chemo presents with skin patches with an ulcerated appearance and occasional necrotic center.
increased PTT, neutropenia
psuedomonas aeruginosa
ecthyma gangrenosum is caused by psuedomona bacteremia
pt is newly diagnosed with CML and begins tx. later presents with HA and an eye problem. PE shows tenderness of paranasal sinus, left orbit swelling, cellulitis, mild proptosis, ptosis. bx shows hyphae with acute angles
aspergillus fumigatus
Nicotinic blockade (diplopia, dysphagia) and muscarinic blockade (dry mouth) is suggestive of
The 3 D’s suggests Ingestion of C. botulinum toxin
Inhibits ACh release
Can be partially overcome by high-rate repetitive nerve stimulation (CMAP)
Tx of a pt with a recent heart valve replacement pt that has cultures poitive for cat + coag - Staph
Staph epidermidis
Vanco
Kidney transplant patient with pleuretic chest pain, cough, and low grade fever. Infiltrate in lower lobe of lung. Not responding to abx. Brnchoalveolar lavage reveals red round organism on mucicarmine staining
Cryptococcus neoformans
This is the only pathogenic fungi with a polysaccharid capsule (virulence factor). Stains red with mucicarmine
Can present as meningoencephalitis or lung dz in immunocompromised
Characteristics of scarlet fever (S. pyrogenes
fever, pharyngitis, sandpaper-like rash, circumoral pallor, strawberry tongue
Physical characteristics of candida
Pseudohyphae with bloastoconidia
Physical characteristics of blastomyces
Yeast with distinctive broad-based budding
Physical characteristics of Coccidioides
Spherules with endospores
Physical characteristics of cryptococcus
Capsule (India ink stain)
Physical chracteristics of Histoplasma
Small oval yeast within macrophages
Nearly all Candida infections can be treated with
fluconazole
Woman with recurrent transient pulmonary infiltrates and history of bronchial asthma, especially in winter. She does use albuterol. Labs demonstrate Eosinophilia. CT shows proximal bronchiectasis.
Aspergillus fumigatus
Allergic bronchopulmonary aspergillosis
Pts with a history of asthma or CF are prone to allergic hypersensitivity reaction to the fungus.
Pt with persistant fever, chills, fatigue, dyspnea for 10 days. History significant for splenectomy and recent travel to Conneticut. Bilateral infiltrates on CXR. Labs show normocytic normochromic anemia with a cross-shaped intraerythrocytic inclusion
Babesiosis
Tick borne infection (like borrelia)
Coinfection is common
Live cycle of Hep B
dsDNA -> +RNA template -> dsDNA progeny
Apiration pneumonia
Lung parenchyma infection
Aspiration of oral microbes (anaerobes)
Presents days after aspiration with fever, cough, and sputum. Usually in RLL and can progress to abscess
Tx - Clindamycin
Aspiration pneumonitis
Lung parenchyman inflammation
Aspiration of gastric contents presenting hours after event. Range os symptoms and CXR infiltrates resolve without abx
Tx - supportive
Farm worker presenting with shortness of breath, fatigue, myalgia, and severe retroobital headaches. Elevated ALT/AST and throbocytopenia
Coxiella burnetii
Q fever - acute phase
Inhalation of bacteria from animal waste
Fatal if untreated and progressis to infective endocarditis
A female pt presents with pelvic pain, fever, and chills following a D&C 2 days ago. On PE she has lower abdominal tenderness, an open os, foul-smelling tissue in vaginal canal and moderate CVA tenderness
Septic abortion = infection of the retained products of conception in the uterus
S. aureus is the most common cause but can also be E. coli, Group B strep
Organisms usually stay in the placenta but pt can become septic if they enter the intervillous space
Tx - abx and surgical evacuation
Can have long term complications (Asherman syndrome) involving adhesions in the uterus leading to amenorrhea and infertility
Co innoculation of H. flu and S. aureus allows H. flu to grow larger colonies on sheeps blood agar. Why?
S. Aureus provides NAD+ (Factor V) “satellite phenomenon”
Hemattin (Factor X) will be released from lysed RBC’s
How do you manage a pt with a recent staph infection that presents with fever and tenderness over the upper lumbar vertebrae without overlying skin changes?
Pt probably has vertebral osteomyelitis. Hmatogenous spread. Initial evaluation should include blood cultures and MRI of the spine.
If soil is heated to 100C for 15 min what bacteria could survive?
Bacillus anthracis
Just because it’s in the soil in the form of a spores. Spore forming bacteria can survive boiling water
reovirus with dsRNA
Rotavirus
Flu-like febrile illness with myalgia, joint pain, retro-orbital pain, bleeding, rash, thrombocytopenia, leukopenia, and elevated LFT’s following travel to mexico
Dengue Hemorrhagic fever
Do have life long immunity following infection, but can get a secondary infection with a different serotype and can cause a more severe illness
Sexually active female pt with UTI. Organism is Gram + cocci, catalase +
S. saprophyticus
Also noboviocin resistant
Pt being treated for Hodgkins dz presents with fever, chills, and malaise. Culture grows Gram positive rods with a very narrow zone of beta hemolysis on blood agar and grow well in the cold.
Listeria monocytogenes
Need cell-mediated immunity to clear them
Tumbling motility at 22C
A neonate presents with clenched muscles and difficulty feeding following an uncomplicated home delivery. The umbilical cord with covered with soil. Other than hygienic umbilical cord care, what other strategy could have prevented the condition?
Neonatal tetanus
Prevent with: good hygienic umbilical care and vaccination of the pregnant mom
A grandfather had HA, myalgia, malaise, cough, and throat pain and was set home on conservative management. He presents 5 days later with dyspnea, chest pain, and productive cough and is admitted
Pt initially had influenza
Elderly pts can develop a secondary bacterial pneumonia due to damaged mucocilliary epithelium. Generally acquire Strep pneumo, Staph aureus, or H. flu
How does Corynebacterium diphtheriae acquire virulence?
Transduction or lysogenization of exotoxin (Tox gene)
A pt with C. diff is placed on a po macrocyclic abx that is bacteriocidal and minimal systemic absorption
Fidaxomicin
inhibits RNA polymerase
What is the most important factor in the pathogenesis of Shigella dysentery
Mucosal invasion (M cells that overlie Peyer’s patches)
The virulence in rabies is due to its ability to bind which receptor?
Nicotinic Acethlcholine receptors
A kid has a 2 day history of diarrhea and his puppy had diarrhea about a week ago. Kid is up to date on vax. Stool is negative for ova and parasites
Campylobacter jejuni can be transmitted from animal to human.
Yersinia too
Abdominal pain can mimic appendicitis
What is malignant otitis externa?
Severe ear infection seen in DM pts. Presents with ssevere ear pain and drainage and granulation tissue. Can progress to osteomyelitis of the skull
Pseudomonas aeruginosa - non lactose fermenting, oxidase +, Motile GNR
Tx - Ciprofloxacin
A pt with recent viral esophagitis and pneumocystis pneumonia is presenting with meningitis. CSF has high protein and pleocytosis. Positive latex agglutination for soluble polysaccharide Ag
Pt likely has HIV
Meningitis due to cryptococcus neoformans
Light microscopy of CSF would reveal budding yeast.
The adult version of the S. pneumo vaccine contains which components?
Outer polysaccharide covering
This is found in both the conjugate and unconjugated vaccines
A pt with pyelonephritis has a culture positive for motile Gram negative rods demonstrating a green metallic sheen on eosin methylene blue (EMB) agar and hemolysis on blood agar
E. coli
Major virulence factor in UTIs = Fimbrial Ag
What perinatal care should be given to prevent a Strep aglactiae infection in a neonate?
Interpartum ampicillin
pt presents with fever and jar pain. PE shows a swelling of the postauricular area extending to the angle of the mandible. Dx?
Parotitis ( due to dehydration, intubation)
S. aureus
Elevated amylase confirms dx
Where is the primary site of ribosome synthesis and assembly?
nucleolus
All ribsomal rRNA is made here except 5S
A double stranded linear segmented RNA virus?
Rotavirus
Vector in Trypanosoma cruzi?
Reduviid bug
A gram + diplococci that causes pneumonia
S. pneumo
Staghorn calculi are formed by?
Urease producing microorganisms Staph species Ureaplasma Proteus (most common) Klebsiella Pseudomonas
What is a worrisome complication of mucormycosis?
Meningitis
A pt presents with right upper quadrant pain, jaundice, and fever
Bacterial cholangitis
Long history of gallstones causes blockage of the bile duct leading to infection.
Bacterial infection of bile duct. Usually enteric GNR
Most common cause of osteomyelitis in a healthy child
S. aureus
Most likely cause of meningitis in a 2 day old infant?
Group B strep
Most common cause in kids
A female is brought to the ED for suspected appendicitis, but US revealed that the mass was within the pelvic cavity. She needs a different emergent surgical procedure
Chlamydia
Causes scarring of the fallopian tubes leading to ectopic pregnancy
A viral cause of seizures in an HIV pt with a CD count of 150
HSV 1 or HSV 2
Good alternative to treat gram + organisms in a pt allergic to penicillin
Macrolides (erythromycin)
a pt has a sore throat, hoarseness, productive cough, and elevated gamma-glutamyltransferase level. CXR shows lobar pneumor. Tx = cefuroxime. Dx?
Klebsiella pneumoniae
Nosocomial and CA pnumonia
Chronic alcoholics have elevated gamma-glutamyltransferase
GN encapsulated rod on sputum smear
mucoid colonies on MacConkey
tx = second gen cephalosporin and an aminoglycoside
A homosexual man with steatorrhea
Giardia
Viruses of the reoviridae family have what characteristics?
ds segmented RNA with icosahedral nucleocapsids
IE - rotavirus, coltivirus
What step of proteins translation does C. dpitheriae’s toxin inhibit?
EF2 toxin
inhibits elongation (translocation)
Complexes with GTP to bind the ribosome
a pt with a history of mitral valve prolapse presents with subacute endocarditis that are throwing microemboli in the hands (Janeway, Osler), retina (Roth spots) dx?
Step veridians
Most commone cause of SAE in the setting of mitral valve prolapse
A pt with Aschoff nodules and a new murmur
Rheumatic heart dz
10 y/o with seizures, poor school performance, CSF findings consistent with viral infection. Respiratory secretions + multinucleated giant cells with intracytoplasmic and intranuclear inclusions. Rash on the trunk
Measles
I a pt has a penicillin allergy they should receive?
Erythromycin
Macrolide against Gram + and Gram -
A neonate presents with conjunctivitis on day 13 of life. Dx?
Chlamydia trachomatic (D-K) at risk of getting pneumonia
Trismus is?
Lock jaw
Seen in tetanus
Tenesmus?
Sensation of needing to empty the bowel although there is no stool to pass. Inflammatory dz of the bowel
Ziehl-Neelsen stain is used for?
Acid fast bacteria (M. TB)
Schistosoma haematobium causes which type of bladder cancer?
Squamous cell carcinoma (SCC)
Keratin pearls on bx
Which other organism carries a toxin with a similar MOA as Bacillis anthracis?
Edema factor = increase in intracellular cAMP
Also seen in cholera toxin
Germ tube postivie fungus
Candida albicans
Germ tube = hypahe
Germ tube negative fungus
histoplasmosis, blastomycosis, coccidioidomycosis
HIV pt (CD4 = 22) with hemiparesis, visual defects, cognitive impairment. Negative LP but bright spots are seen on the MRI. Dx?
JC virus
Multifocal leukoencephalopathy
CD4
Regan Lowe medium is used for?
Bordetella pertusis
Culture from a calcium alginate swab (bacteria do not transfer well on cotton)
What infection can occur when an HIV pts CD4 count drops
Disseminated Mycobacterium avium-intracellulare infection
TB like dz
Azithromycin prophylaxis
A 12 y/o presents with mental status changes characteristic of encephalitis x 1 wk. CSF has elevated WBCs, mildly elevated protein, and RBCs. CT show focal unilateral pathology of the temporal lobe. Dx?
Encephalitis due to HSV1
elevated proteins + RBCs in CSF = HSV1 encephalitis
A poultry farmer in ohio presents with pneumonia. XR lesion in the upper lung lobe and hilar lymphadenopathy. Dx?
Histoplasmosis
Ohio and Mississippi river valley
Found in bat droppings
7 y/o immigrant presents with red itchy eyes with swelling, cough, runny nose. Oral cavity has small lesions with white centers. Dx?
Rubeola (measles)
2 C’s - cough, coryza, conjunctivitis, and Koplick spots
Expect to see a rash 1-2 days after the appearance of the Koplik spots that will start at the head and move its way down
What is the neurological syndrome associated with Rubeola infection
Subacute Sclerosing panencephalitis (SSPE)
Occurs 7-9 years after Rubeola infection
Personality changes, lethargy, difficulty in school, odd behavior. Can progress to dementia, myoclonic jerking, and eventual flaccidity a decorticate rigidity.
After a camping trip that included interaction with many types of animals a pt presents with RUQ pain, nausea, and vommiting. An enlarged liver with a cyst is found. Dx and Tx?
Echinococcus granulosus
Albendazole
parasitic tapeworm in feces (dog)
Albendazole inhibits tubule polymerization. Cannot go straight to surgery b/c the contents of the cysts causes anaphylactic shock
Which organisms cause struvite stones?
Urease positive Proteus Klebsiella Staphylococcus Ureaplasma Pseudomonas Alkaline urine with multiple magnesium ammonium phosphate crystals
What is the MOA of enfuvirtide?
Prevent entry of viral particles into the target host cell (gp41 mediated fusion)
What is the MOA of rltegravir?
Inhibits integrase and prevents viral integration into the host genome
MOA of maraviroc?
entry inhibitor
Binds CCR-5 on T cells and monocytes and block its interaction with gp120
Specific test for Syphillus infection?
Fluorescent treponemal antibody absorption test
VDRL and RPR are more sensitive but less specific
Virulence factor that allow S. pneumo to colonize the lung?
IgA protease
cleaves secretory IgA Ab in mucosal surfaces allowing for bacterial colonization
Which bacteria have lipopolysaccharide?
outter membrane of Gram-negative bacteria. Induces a strong immune response by the host
Pt presents with high fever, black vomitus (dark-colored blood in the vomitus as a result of GI bleeding), jaundice, HA, and back pain. Dx?
Yellow fever, flavivirus
Dx with rtPCR
Bx = councilman bodies (acidophilic inclusions in liver), but bx is usually not recommended due to bleeding risk
How is be facial n. palsy differentiated from stroke?
If the pt can furrow the brow - stroke
if the whole half of the face is paralyzed - borrelia
What syx are found in the second phase of Borrelia infection?
CN VII palsy, transient arthralgias, aV nodal block, secondary annular rash, carditis
Tx - doxycycline
However, if pt has cardio or neuro involvement tx with IV ceftriaxone
What makes Bells palsy different from facial n. palsy?
Bells palsy is idiopathic origin
Facial n. palsy is a known cause (ie borrelia)
A woman presents with a vaginal infection due to candida following a course of tetracycline. Why?
Loss of gram + faculative anaerobes
Lactobacilli make up the normal vaginal flora
Dx - KOH prep
What type of Hypersensitivity rxn is PSGN
Type III (Arthus rxn) Ag-Ab complexes are deposited in the GBM and activates complement
What is a type II HS rxn?
Ab mediated but IgG binds Ag on the surface of a target cell - autoimmune
In CMV retinitis, what would be a late finding in the dz?
Retinal detachment
CMv is a common cause of blindness in AIDS pts
Presents with rapidly diminishing sight and on fundoscopy cotton-wool exudates, necrotizing retinitis, perivascular hemorrhages, and ultimately retinal detachment
Tx - ganciclovir and foscarnet
Which two toxicities are associated with isoniazid use?
Neurotoxicity (Add B6)
Hepatotoxicity
Infectious cause of CHF in a pt with no RF’s?
Coxsackie B
Icosahedral member of the picornaviridae family
Which two agars can be used to culture Bordetella pertussis?
Bordet-Gengou (potato) agar
Regan-Lowe medium
Transfer with calcium alginate swab
Major cause of viral pink eye?
Adenovirus
Naked icosahedral dsDNa
Self-limited, no tx
When would you use Loffler medium?
Corynebacterium diptheriae
Maraviroc prevents?
CCR-5 binding to gp120
Enfuvirtide prevents?
gp41 mediated fusion
Why does Hep D need Hep B?
Coating of the viral particles
HDV needs HBV sAg so that it can enter future hosts
When Aspergillus forms a fungus ball within a preexisting cavity, what is this process?
Colonizing
Causes a lung hypersensitivty rxn in allergic bronchopulmonary aspergillosis in individuals with asthma
PSGN is which type of HS rxn?
Type III = Ag - Ab complexes leading to complement activation
Type II = Ab mediated
What is a clue cell made of and which infection does it suggest?
Clue cell = epithelial cell covered with gram-variable rods
Gardnerella vaginalis
Thin off-white discharge with fishy odor, imbalance of vaginal flora, see clue cells on wet mount
pH > 4.5, + whiff test (amine odor with KOH)
Tx - metronidazole or clindamycin
In TB cord factor is?
A virulence factor
Inhibits PMNs, destroys mitochondria, and increases release of TNF
8 y/o presents with rapid and irregular movements of his hands and funny faces. He also has several circular, faintly erythematous lesions on his abdomen. What is the mechanism?
Cross-reactivity of Ab against bacterial and host Ag
Anti-M Ab cross-react and attack cardiace and CNS Ag
If a person has Anti-HBs Ab then they?
Have been vaccinated against HBV
Why add clavulanic acid to amoxicillin treatments?
Decrease drug cleavage by bacterial cells
Sulbactam and tazobactam are beta-lactamase inhibitors.
Expands amoxicillin specturm of actitivy to include stains of B-lactamase synthesizing bacteria
MOA of zidovudine?
Inhibits 3’-5’ phosphodiester bond formation
Nucleoside reverse transcriptase inhibitor
Thymidine analog (no 3’OH group)
A pt tests positive for HBsAG and elevated LFTs. The most likely outcome of the infection is?
Complete resolution
95% of HBV infected adults have acute hepatitis with mild or subclinical syx that eventually completely resolve
What mechanism do bacteria use to become resistant to rifampin?
Alter structure of enzymes involved in bacterial RNA synthesis
Inhibits bacterial RNA polymerase
Red-orange body fluids
Inhibits transcription
Pt presents with a urethral dischage that is rich in neutrophils with intracellular gram negative diplococci. He is given IM ceftriaxone but his syx do not improve. What tx should he receive next?
PO azithromycin
It should have been assumed that he had a co-infection of neisseria and chlamydia and he should have received ceftriaxone + doxy or azithromycin
Tx for enterobius?
Albendazole
Scotch tape test worm
Pyrantel pamoate - 2nd line
What is the mechanism for naficillin tx is Staph aureus?
Poor interaction with binding proteins
Altered penicillin-binding protein in the peptidoglycan cell wall that does not bind beta-lactams effectively
Elderly pt presents with acute mental status change, seizure, HA, focal neurologic deficits. CSF reveals hemorrhagic lymphocytic pleocytosis with NL glucose. ABN MRI signal in the temporal lobes. Dx?
HSV encephalitis
Tx - acyclovir
A pt with methicillin-resistant S. aureus and started on an IV abx. A week later he has mascle pains and elevated creatine phosphokinase that resolves with d/c. What is the MOA of the abx?
Maintenance of membrane potential
Daptomycin - gram positive organisms. Causes depolarization of bacterial cellular membrane and inhibition of DNA, RNA, and protein synthesis. Dapto is associated with increased creatine phosphokinase and increased incidence of myopathy
A pt with primary TB infection is put on Isoniazid monotherapy. This would result in?
Selective survival of bacterial cells secondary to gene mutation
Active TB is never treated with monotherapy due to the fast emergence of mycobacterial abx resistance from rapid, selective gene mutations.
A strain of Candida develops a mutation in the enzyme responsible for synthesizing a fungal cell wall polysaccharide. This strain would be resistant to?
Caspofungin
Inhibits the synthesis of the polysaccharide glucan
Azoles, Ampho - inhibits ergosterol in the cell MEMBRANE
What lab findings would suggest that a HBV pt has progressed to chronic HBV?
If HBeAg persists for several months and host anti-HbeAg remains low, suspect chronic HBV with high infectivity
Which antifungal causes a decrease in ergosterol incorporation into the cell membrane
Nystatin Polyene antifungals (ampho, nystatin) act by binding ergosterol in the funagl cell membrane
MOA of Triazoles
Inhibit ergosterol synthesis
-azoles
MOA of Fluctosine
Converted to 5-fluorouracil interferes with fungal RNA and protein synthesis
HIV pt presents with esophageal hyperemia and linear ulcerations. Dx?
CMV
HIV pt presents with patches of adherent grey/white pseudomembranes on endoscopy. Dx?
Candida
HIV pt presents with small vesicle and “punched-out” ulcers on endoscopy. Dx?
HSV-1
Pseudomonas treatments
Penicillins - ticarcillin, piperacillin
Cephalosporins - ceftazidime, cefepime
aminoglycosides - amikacin, gentamicin, tobramycin
fluoroquinolones - ciprofloxacin, levofloxacin
Monobactams, carbapenems
Pt presents with mono syx with 30% atypical lymphocytes. Serum fails to agglutinate horse RBCs. Dx?
CMV
+ agglutination (monospot) would suggest EBV
other causes of monospot negative mono are HHV6, HIV, and toxo
A DM pt presents with a black eschar around his nasal cavity. What test would confirm the dx?
Mucosal bx
Mucormycosis
Pathogenecity of H. flu depends on?
antiphagocytic polysaccharide capsule
Primary causes of hepatic abscesses?
underdeveloped country - parasitic (Entamoeba, echnococcal)
Developed country - bacterial (S. aureus)
Pt in the north east presents with flu like syx on intraerythrocytic inclusions on smear. Dx?
Babesiosis
Ixodes tick vector
Maltese cross
Pt with a UTI has gram-positive cocci in chains. Dx?
Enterococcus gram positive cocci in pairs or chains No hemolysis on blood again (gamma) Pyrrolidonyl arymlamidase (PYR) + Grow in bile and 6.5 % NaCl Negative nitrites on UA
S. pneumo vaccine for adults includes which component?
Outer polysaccharide covering
Induces a T cell independent response
Also N. meningitidis and H. flu
S. pneumo vaccine for kids contains?
Conjugate vaccine = polysaccharide material attached to a protein Ag, more robust T cell response
Pt has a lung bx with spherules packed with endospores. Dx and recent hx includes?
Coccidioides
Recent travel to Arizona
Fungus passed through bird droppings?
Cryptococcus - pigeons, immunocompromised meningitis
Histoplasma - Mississippi and Ohio river basins, bird and bat droppings. Hx of cleaning bird coops or caving
Fungal rhinosinusitis with acute angles and septations
Aspergillus
Occurs in immunocompromised pt
Granuloma formation in the lung
V-shaped, narrow branching hyphae
Septations look like little bubbles within the organism on bx
Monomorphic, grows on decaying vegetation
Tx - Amphotericin
What process is most important for eliminating Listeria from the body?
Cell-Mediated Immunity
Intracellular bacteria are protected from circulating immune factors (Ab). Listeria is able to live within the macrophage with the action of listeriolysin O (pore-forming toxin selectively activated within acidified phagosomes)
Beta hemolytic (narrow), tumbling motility, grows at cold temps
Neonates are especially susceptible up to 3 months of age due to naive cell-mediated immunity
Contaminated dairy products
Skin lesions following the lymph nodes following a thorn prick
Sporothrix schenckii
Bx = granuloma with histiocytes, multinucleated giant cells, PMNs, surrounded by plasma cells
Forms subQ noddules and ulcers along the lymphatics
Dx - by culture
Tx - Itraconazole
EBV binds which host cell receptor for entry?
CD 21
Parvovirus binds which host cell receptor for entry?
RBC P Ag
Small ovoid bodies with Macrophages
Histoplasma
Seen in BM bx of immunocompromised
Hyphae on sabouraud agar
Can be dx’d with immunoassay and serology
nonlactose-fermenting, oxidase +, motile, GNR
Pseudomonas
Causes malignant otitis externa in elderly DM pts
Exquisite ear pain and drainage with granulation tissue in the ear canal
Doubly refractile wall with single broad-based bud
Blastomyces
Ohio miss river
Thick walled spherule filled with endospore
Coccidioides
Southwest
PYR +
Enterococcus
Strep pyogenes
CMV infection during pregnancy increases the risk of what to the unborn fetus?
Chorioretinitis Sensorineural deafness Seizures Jaundice Microcephaly
HHV 6 is? Syx?
Roseola
Occurs in
flulike illness + myalgias + retro-orbital pain + recent travel hx
Classic dengue fever
If pt also has thrombocytopenia and petechiae - Dengue hemorrhagic fever
ssRNA viruses with 4 serotypes, Flavirus
Why is HCV considered genetically unstable?
Lacks proofreading 3’-5’ exonuclease activity in its RNA polymerase
Glycoprotein sequences also have a hypervariable region prone to mutation
Bartonella causes cat scratch fever and?
Bacillary angiomatosis in the immune compromised, culture negative endocarditis
Axiallary lymphadenopathy is common
Noneveloped ssDNA virus?
Parvo
Most common Catalse Problem organisms?
S. aureus Burkholderia Serratia Nocardia Aspergillus Beware of these in a pt with Chronic Granulomatous dz (NADPH oxidase deficiency)
All rRNA (except 5S) is transcribed in the?
Nucleolus
Dense round structure
Contains ribosomal DNA, newly transcribed rRNA, and ribosomal proteins
Why do asplenic pts have more severe syx?
Defect in systemic bacterial clearance
Fxn of spleen red pulp = 1. Filter blood, 2. Site of opsonizing Ab synthesis (esp important for clearing encapsulated species)
Asplenic pts are prone to infection by encapsulated organisms (S. pneumo, H. flu, Neisseria)
What are the key characteristics of HSV encephalitis?
Potentially fatal complication of primary dz or reactivation
Necrosis of temporal lobe causing aphasia, personality changes, and classic syx of encephalitis
Changes in host range of a virus are usually due to a mutation in the?
Surface glycoprotein
Mediates virion attachment and fusion
STD with Deep, purulent painful ulcers with matted/suppurative lymphadenitis?
Chancroid
Haemophilus ducreyi
Dx - Gram stain, culture, PCR
STD with Painless, progressive, red serpiginous ulcerative lesions without lymphadenopathy
Klebsiella granulomatis
Dx - Gram stain, culture (tough), Bx (Donovan bodies)
Pt presents with vomiting two hours after ingesting a food with mayo. Dx?
S. aureus
Exotoxin was formed prior to ingestion
B. cereus also creates a stable exotoxin but look for hx of eating reheated rice
Diplopia
Dysphagia
Dysphonia
Botulism (12-36 hrs post consumption)
Dysphonia = difficulty speaking
Toxin prevents release of ACh
PE - tonsilar erythema with exudates
Microscopy - clumped Fram + bacter with polar granules that stain deeply with aniline dyes
Corynebacterium diphtheriae
Inhibits host cell protein synthesis by catalyzing the ADP-ribosylation of host cell elongation factor-2
Nonmotile, unencapsulated GPR found in cumps. Cytoplasm contains metachromatic granules that stain with aniline dyes (methylene blue)
Cause of cephalosporin resistant meningitis in a kid
Listeria
1st line tx = ampicillin
Causes dz in those with deficient cell-mediated immunity (kids and immunocompromised)
Cephalosporins would cover - H. flu, Neisseria, Srep agalactiae, strep pneumo)
HBV genome replication cycle
dsDNA -> + RNA -> dsDNA progeny
Replicates via reverse transcription
Genome, syx, tx, and route of transmission of adenovirus
Genome - dsDNA
syx - red eyes in croseded quarters (camp, military, dorms)
tx - supportive
transmission - direct contact, fecal-oral, respiratory droplets
HIV pt presents with tonic clonic seizure and two ring-enhancing focal lesion with surrounding edema in R frontal lobe. Dx?
Toxo - multiple ring-enhancing lesions with mass efect
Tx - Pyrimethamine + sulfadiazine, or pyr + clindamycin if allergic to sulfa drugs
Also add leucovorin (folinic acid)
Atypical pneumonia + watery diarrhea + smoking hx + recent travel on a cruise
Legionella
hyponatremia
Suspect gonorrhea and tx with?
Macrolide (chlamydia) and 3rd generation cephalosporin (ceftriaxone) (gonorrhea)
Morphology of Bordetella pertussis
Gram-neg coccobacillus
Which cell type secretes IFN gamma in a quantiferon test?
Th1
Macrophages secrete IL-2
Pt presents with pruritic rash (worse at night) on the palmsa. excoriations with small crusted red papules. Dx?
Scabies
Dx with skin scrapings from lesions showing mites, ova, and feces
MOA of isoniazid
Inhibits mycolic acid synthesis
Pathogen loses its acid fastness and stop proliferating
MOA of rifampin?
Inhibit bacterial DNA dependent RNA pol
Major virulence factor in epiglottitis?
Polyribosylribitol phosphaste
component of H. flu’s capsule
A virus is identified to have a membrane envelope with a similar composition as its host. What could it be?
CMV, EBV, HHV etc
Herpesviruses bud through and acquire the lipid bilayer envelope from the host cell nuclear membrane
Most other viruses bud through the host membrane without acquiring a phospholipid membrane
Immigrant presents with tonic-clonic seizure. On MRI there is a cyst in the left sylvian fissure that has minimal enhancement and no associated edema. Dx and mode of transmission?
Neurocysticerosis
Ingestion of Taenia solium (pork tapeworm) eggs from the stool of tapeworm carriers (fecal oral route)
Common cause of seizures in central and south america
NOTE - eating contaminated meat does not cause neuro syx, just tapeworm infestation, nbd
What is used to treat rabies?
Inactivated vaccine
syx - agitation and muscle spasms progressing to coma
Infant with irritability, poor feeding vomiting, large head circumference. white-yellow chorioretinal lesions bilaterally. Enlarged ventricles with intracranial calcifcation on CT. Dx?
Toxo
Torches infection
Hydrocephay + intracranial calcification + chorioretinits
Agar for C. diptheria?
Cysteine-tellurite agair
Loffler’s medium
(kid laughing at the telle)
How can you distinguish between toxo and Neurocysticercosis (Taenia solium) on seizure pt?
Immunocomp pt - Toxo
Travel to South America - Taenia
How does TB’s cord factor establish virulence?
PMN inhibition
Mitochondrial destruction
TNF release
E. coli is able to cause sepsis by entering through the?
Urinary tract
Fimbriae are essential for colonization
Cause of fulminant hepatitis in pregnant women?
Hep E Unenveloped, ssRNA Fecal-oral Asia, Africa, Mexico No chronic dz Higher mortality in preggo's
Fxn of the virulence factor found in the Peptidoglycan wall of S. aureus?
Protein A
binds the Fc portion of IgG -> impairs complement activation, opsonization, phagocytosis
Congenital rubella syndrome
classic triad = white pupils (congenital cataracts) + sensory-neural deafness, PDA
But also microcephaly, deafness
prevent with live MMR vax
Older woman is presenting with encephalitis, meningitis, flaccid paralysis, and a rash. dx?
West Nile virus (Flavivirus) Encephalitis + flaccid paralysis + rash \+ ssRNA Mosquito borne, see transmission in the sumer Tx - supportive
Tx plan for cryptococcal meningitis?
Amphotericin B + flucytosine
followed by long term fluconazole
MOA of C. diff toxin?
Compromises the cytoskeleton integrity of intestinal mucosal cells
Disrupt actin cytoskeletal structure and intracellular signaling
toxin A - causes more inflammation and fluid secretion (enterotoxin)
Toxin B - is more cytotoxic
Why does HDV need HBV?
Coating of viral particles
Non lactose fermenting GNR causing syx in a pt with an indwelling catheter?
Pseudomonas aeruginosa
If you see viral gastroenteritis in US school kids assume it is?
Norovirus
Rotavirus has similar syx but rarely seen in the US due to vax’s
Most likely route of infection of Listeria in immunocompromised?
Contaminated food
Water borne gastroenteritis with high mortality in Asian countries. Oxidase-positive GN bacilli that grow well on highly alkaline selective media?
Vibrio
Thiosulfate citrate bile salts sucrose again (TCBS)
Pts with achlorhydria (low gastric acid production) can get the disease from a lower infectious dose (this includes taking omeprazole)
Following an influena infection a pt presents with pneumonia due to?
Bacterial pneumonia
S. pneumo > S. aureus > H. flu
Pt presents with appendicitis. Most likely organism?
Usually polymicrobial with Bacteroides fragilis and E. coli
Botulinum toxin blocks?
Presynaptic excocytosis of ACh vesicles
In Mycoplasma pneumo, which Ab’s cause the hemolytic anemia?
Cold agglutinins
While in central america a pt develops watery diarrhea with cramps n/v that resolves two days later w/o abx?
ETEC "traveler's diarrhea" Heat labile (LT) and/or heat stable (sT) enterotoxins are endoded on a plasmid LT = cholera like toxin, increases intracellular cAMP in gut mucosal cells by activating Gs ST = increases cGMP
Tx for pseudomonas?
cephalosporins (Cefepime, ceftazidime)
Penicillins (ticarcillin, piperacillin)
Pt has dysuria and hematuria 2 weeks after visiting africa. U/S bilateral hydronephrosis and bladder wall thickening. Dx?
Schistosomiasis haematobium
Transmitted by snails
S. japonicum and S. mansoni cause intestinal and hepatic schistosomiasis
Lobar pneumonia in an alcholoic is caused by?
Aspiration of oropharyngeal contents (anaerobic bacteria: Fusobacterium, Peptostreptococcus, Bacteroides)
Common cause of lung abscesses
A baby born to a mom that was infected by HBV during the third trimester is likely to have elevated levels of what in her serum?
HBeAg
Infected neonates are at high risk for chronic infection but are usually asymptomatic with very minor clinical findings
Pt has pneumonia in the RUL. Encapsulated GNR that ferments lactose
Klebsiella pneumoniae
Linear ulcerations in immunocompromised?
CMV
Infection post dog bite that has mouse like odor on culture?
Pasteurella multocida
Tc - amoxicillin + clavulanate
A woman has a stillbirth at 18 weeks gestation that has pleural effusion, pulmonary hypoplasia and ascites. Dx?
Parvo
Nonenveloped ssDNA
Mom had reported arthralgias
Fetal hydrops = pleural effusion with secondary pulmonary hyoplasia and ascites
Grayish white vaginal discharge
Fishy odor
Clue cells
Gardenella
Anaerbobic gram variable rod
Add KOH = whiff test
Tx - metronidazole, clindamycin
MOA of edema factor
Adenylate cyclase that increases intracellular cAMP -> PMN and macrophage dysfunction and tissue edema
Found in Bacillus anthracis and Bordetella pertusis
Infant presents with winter cough and difficulty breathing. Diffuse expiratory wheezes and scattered rales throughout
RSV
How do we prevent vertical transmission of HIV1?
Antiretroviral therapy
All HIV + moms should take ART regardless of CD4 count or viral load
2 NRTs + protease inhibitor/NNRT/integrase
Infants will generally receive several weeks of zidovudine
Group A strep is resistant to phagocytic killing when placed in fresh human blood. This could be overcome by adding Ab against?
Protein M - major virulence factor, inhibits phagocytosis and activation of complement
NOT:
Streptolysin O - lyses RBCs
Steptokinin - catalyzes plasminogen to plasmin to facilitate strep spread
A medium containing vancomycin, colistin, nystatin, and trimethoprim favors growth of?
Neisseria gonorrhoeae
Thayer-Martin selective medium
Chocolate agar + Vanco, colistin, nystatin, trimethoprim
Which cause of gastroenteritis has a small infectious dose?
Shigella flexneri
Also entamoeba and Giardia
Most important factor in pathogenesis of Shigella?
Mucosal invasion
Non-motile, non-lactose fermenting organism
Mucosal invasion of M cells that overlie Peyer’s patches
Pt develops parotitis following intubation. What serum marker would be useful in dx?
Elevated Amylase (nut lipase WNL to rule out pancreatitis) Typically in post op or post intubated elderly pts. Usually S. aureus
Pneumonia + intranuclear cytoplasmic inclusion bodies in a post lung transplant pt?
CMV
enveloped dsDNA virus
Owl’s eyes
How do you treat C. diptheriae?
Passive immunization
aedes aegypti transmit which 2 diseases?
Dengue Fever - retrorbital pain + joint and muscle pain
Chikungunya - Flu like + polyarthralgias + rash
Filamentous bacteria with pulmonary, skin, and CNS syx?
Nocardia
Pt with flu like illness, retroorbital headace with recent exposure to animal waste (farm animals)
Coxiella burnetii
Q fever
HSV1 acquires acyclovir resistance from co culture with HSV 2 and the progeny continue to be resistant. What is the mechanism?
Recombination
Gene exchange through cross over
Can’t be phenotypic mixing because the progeny would have lost resistance
A strain of M. TB has decreased activity of intracellular catalase peroxidase. It would be resistant to?
Isoniazid
INH prevents mycolic acid synthesis and INH must be processed by mycobacterial catalase peroxidase for the drug to be activated within the bacteria
