Infectious Diseases Flashcards
what is selective IgA deficiency
most common primary immunodeficiency
*symptoms: recurrent sinopulmonary and gastrointestinal infection due to absence of secretory IgA
silicosis impairs the __________ of cell-mediated immunity.
macrophage effector arm
- internalized silica particles disrupt macrophage phagolysosomes to release the particles and viable mycobateria
mechanism of action of cromolyn and nedocromil
inhibit mast cell degranulation
prevent release of preformed chemical mediators
essential pathogenic mechanism for Shigella infection
mucosal invasioin- they invade the gastrointestinal mucosa, particularly the M cells that overlie Peyer’s patches–> induce apoptosis of host cell and spread to adjacent cells
Listeria is not sensitive to _________ so it an be treated with ________
cephalosporins; ampicillin
mechanism of action of diphtheria exotoxin
ribosylation inactivates elongation factor-2, thereby inhibiting protein synthesis and causing cell death
recurrences of genital herpes can be reduced with _______
daily treatment of oral valacyclovir, acyclovir, or famciclovir
how to prevent congenital rubella syndrome
vaccination with live-attenuated rubella virus vaccine
first-line treatment for Enterobiasis (enterobius vermicularis) aka pinworm for perianal itching in kids
Albendazole
or pyrantel pamoate for pregnant patients
bacteria that are resistance to drugs that attack the peptidoglycan cell wall (d-alanine-D-alanine analog)
Mycoplasma genus since they lack peptidoglycan cell walls
an be treated with anti-ribosomal agents (eg, tetracycline, macrolides)
Bacillary angiomatosis can be caused by _______ infection
bartonella henselae
*red-purple papular skin lesions ( can be fatal)
virulence factor for Haemophilus influenzae type b (Hib)
polyribosylribitol phosphate= capsule component
Hib is the most common cause of epiglottitis–> presents with fever, stridor, and dyspnea
Hepatitis B virus is a _____ virus
replication sequence:
DNA;
double-stranded DNA–> +RNA template –> double-stranded DNA progeny
serum marks that would help confirm acute bacterial parotitis due to Staphylococcus aureus
elevated serum amylase level
most common laboratory abnormality seen with Legionella pneumonia that is different from other pneumonia is ______
hyponatremia
treatment of acute Corynbacterium diphtheriae requires administration of (in order of importance):
1) diphtheria antitoxin (passive immunization)
2) Penicillin or erythromycin
3) DPT vaccine (active immunization)
what is septic abortion and what (2) organisms may cause it?
any type of abortion resulting in infected retained products of conception in the uterine cavity
*Stapylococcus aureus and Escherichia coli
blastomyces dermatitidis
dimorphic fungus in tissue as round or oval yeasts with thick walls and broad-based bud!
- endemic in SE USA
- lung=primary site
- skin and bone=major sites of dissmination
how do most enveloped nucleocapsid viruses acquire their lipid bilayer envelope?
exception to this?
by budding through the plasma membrane of the host cell
exception: herpesviruses— bud through ad acquire their envelope from the host cell nuclear membrane
what immune system process is needed to to eliminate intracellular organisms?
cell-mediated immunity
-immunocompromised, pregnancy, infants, elderlies are at risk of having serious infections from these organisms since they have compromised cell-mediated immunity
_____________ are normally present in human mouth and are major contributors to tooth decay and initiation of dental caries
viridans streptococci
- can cause bacterial endocarditis, deep wound infections, ab abscesses, and septicemia
- produce dextrans that aid them in colonizing host surfaces
______ is associated with bird and bat droppings in caves in Mississippi and Ohio River basins
Histoplasma capsulatum
______ = dimorphic fungus endemic to SW USA and exists in environment as mold (with hyphae) that forms spores that turn into spherules in lungs
Coccidioides immitis
alpha-amanitin, found in Amanita phalloides aka death cap mushroom) inhibits _________
RNA polymerase II (halting mRNA synthesis)
*cause severe hepatotoxicity
how can tertiary syphilis result in thoracic aortic aneurysm?
vasa vasorum endarteritis and oblitertion–> inflammation, ischemia, and weakening of adventitia
why add clavulanic acid to amoxicillin?
to decrease amoxicillin cleavage by bacterial cells
*clavulanic acid is a beta-lactamase inhibitor–>so when combined with a beta-lactamase susceptible antibiotic allows it to retain efficacy against the bacterium
adenovirus
caused by double-stranded DNA genome transmitted via direct contact, fecal-oral route or respiratory droplets
self-limiting
actue onset of fever, cough, congestion, pharyngitis, and conjunctivitis
what are transposons
mobile genetic elements that can mediate DNA transfer from plasmids to a bacterial chromosome, move genetic material from one position to another along a bacterial chromosome, or transfer genes from a bacterial chromosome to a plasmid
how does nonvirulent strains of S pneumoniae that do not form a capsule can acquire the genes that code fo the capsule and therefore gain virulence?
through a process called transformation (allows bacterium to take up exogenous DNA fragments and integrate them into its genome)
Aedes aegypti mosquitoes can transmit viruses that cause _____ and ______ (and their symptoms?)
dengue fever; chikungunya
DF: acute febrile illness with headaches, retro-orbital pain, and joint and muscle pain
Chikungunya: febrile illness with flulike symptoms, polyarthralgias, and diffuse macular rash
treatment for trichomonas vaginitis and bacterial vaginosis
metronidazole (disulfiram-like reaction after alcohol consumption)
how does lipid A from lipopolysaccharide of gram-negative baceria’s outer membrane induces endotoxic septic shock
activation of macrophages and granulocytes
- -> synthesis of endogenous pyrogens (IL-1, prostaglandins, and inflammatory mediators
- ->symptoms of septic shock
what is lipid A
region of the lipopolysaccharide (LPS) that makes up the outer membrane of gram-negative bacteria.
(toxic component of LPS)
endotoxin: found in the outer membrane
parvovirus B19 replicates in ______ (cell type) precursors in the _________
erythrocyte; bone marrow
erythema infectiosum, slapped-cheek rash
HSV infection can be diagnosed using
PCR, direct fluorescence antibody, viral culture (low sensitivity), or Tzanck smear (showing multinucleated giant cells)
clinical findings of Epstein-Barr virus induced mononucleosis
fever, profound fatique, lymphadenopathy, lymphocytosis, splenomegaly
first line therapy for Lyme disease
doxycycline (a tetracycline)
teratogen– cause teeth staining and also contraindicated in kids age <8
in HIV replication cycle, only the _____ (gag, pol, and env) polyprotein product is glycosylated to _______ and proteolytically cleaved to form _____ and _____
env; gp160; gp120; gp41
gp120 and gp41 work together to help the virus attach by binding to the CD4 receptor of cells
HSV infection can be diagnosed using
PCR, direct fluorescence antibody, viral culture (low sensitivity), or Tzanck smear (showing multinucleated giant cells)
how comes vaccination against Neisseria gonorrhoeae is hard to do?
Gonococci use their pili to adhere to mucosal epithelium
use antigenic variation to modify the pilus protein to avoid host defneses
acute bacterial arthritis in sexually active young adults is commonly caused by
Neisseria gonorrhoeae
associated with disseminated gonococcal infection that leads to septic arthritis
Echinococcus granulosus
- most common cause of hydatid cysts (“eggshell calcification”) in liver
- spilling of cyst contents–> anaphylactic shock
- from dog and sheep
_____ and ______ act by ribosylating and inactivating elongation factor-2, inhibiting host cell protein synthesis and causing cell death
Diphetheria toxin; pseudomonal exotoxin A
most important virulence factor that uropathogenic E coli express
P fimbriae
without it, E coli can’t bind to uroepithelial cells
clinical presentation of tertiary syphilis
cardiovascular involvement and gummas (neurosyphilis can occur at any stage of infection)
gummas= necrotizing granulomas on skin, mucosa, subcutaneous tissue, and bones and within other organs
STD that is initially characterized by painless ulcers with later progression to painful inguinal lymphadenopathy (“buboes”) and ulceration
Chlamydia trachomatis
its inclusion bodies can be seen in host cell cytoplasm
Zidovudine (AZT)
nucleoside reverse transcriptase inhibitor used to treat HIV infection–> make 3’-5’ phosphodiester bond formation impossible
______, _______, and ______ are able to disrupt the peptidoglycan cell wall of gram-positive and gram-negative organisms
penicillins, cephalosporins, and vancomycin
if meningitis due to Neisseria meningitidis (what is the gram and shape), would antibiotic chemoprophylaxis be indicated?
YES-rifampin
-negative diplococcci (cocci in pairs)
what is the most common outcome in HBV-infected adults
> 95% get acute hepatitis with mild or subclinical symptoms that eventually completely resolve
trimethoprim, methotrexate, and pyrimethamine inhibit
dihydrofolate reductase (DHFR)
- trimthoprim-restricts bacterial growth through DHFR
- methotrexate targets rapidly proliferating human cells by halting DNA synthesis through DHFR
- Pyrimethamine treat malaria and toxoplasmosis by inhibiting parasitic DHFR
pelvic inflammatory disease
frequently caused by Neisseria gonorrhoeae and Chlamydia trachomatis
- if severe or untreated–> fallopian tube scarring–> infertility
- treat with both 3rd gen cephalosporin and azithromycin or doxycycline
mucormycosis
infection due to Rhizopus, Mucor, and Absidia species
paranasal sinus involvement in a diabetic or immunosuppressed patient
irregular, broad nonseptate hyphae that branch at right angles
description of Streptococcus pyogenes (Group A streptococci)
gram-positive cocci in chains, catalase-negative, beta-hemolytic, pyrrolidonyl arylamidase positive (PYR-positive)
Secretory IgA’s purpose on mucosal surfaces
bind and inhibit the action of pili and other cell surface antigens involved in bacterial adherence to mucosa–> inhibit mucosal colonization by microorganism
treatment of cryptococcal meningitis
amphotericin B and flucytosine, followed by long-term fluconazole
Actinomyces israelii
- gram positive
- normal oral, GI, and reproductive flora
- cause oral/facial abscesses
*treat with long-term penicillin and surgical debridement
causative agent of syphilis
treponema pallidum
*spiral-shaped gram negative spirochete
use darkfield microscopy from a lesion to diagnose
HaEMOPhilus influenzae causes
Epiglottitis
Meningitis
Otitis media
Pneumonia
spores from Clostridium perfringens cause
food poisoning–> transient watery diarrhea
also cause clostridial myonecrosis (gas gangrene)
azoles mechanism of action
antifungal meds
Inhibit fungal sterol (ergosterol) synthesis by inhibiting the cytochrome P-450 enzyme that converts lanosterol to ergosterol.
neuroimagining of a patient iwth herpes simplex virus (HSV) encephalitis
abnormal MRI signal in the bilateral temporal lobes
mechanism of action of acyclovir
nucleoside analog that , once activated (monophosphorylate with viral thymidine kinase), competes with deoxyguanosine triphosphate for viral DNA polymerase to terminate viral DNA synthesis
Listeria monocytogenes is characterized by what symptoms and who gets affects
- gastroenteritis, septicemia, and meningoencephalitis
- neonatal meningitis
- patients with depressed cell-mediated immunity
outbreaks of infection associated with dairy products, raw fruits and vegetabes and processed meats
Listeria monocytogenes
neoplasm of endothelial cells seen in HIV/AIDS and transplant patients
Kaposi’s sarcoma
- can affect GI, skin, and lungs
- reddish/violet maculopapular lesions to raised hemorrhagic nodules or polypoid masses
- biopsy show spindle cells, neovascularization, and extravasated RBC
symptoms of typhoid fever from Salmonella Typhi
fever with relative bradycardia, watery diarrhea OR constipation, ab pain, salmon-colored rose spots on chest/ab, hemorrhagic enteritis with possible bowel perforation
host defense (2 immune system components) against Candida
1) T lymphocytes–prevent superifical Candida infection
2) Neutrophils- prevent hematogenous spread of Candida
Asymptomatic colonization of the ________________ is the most commonly MRSA-populated site in staff members
anterior nares or the nasopharynx
Parvovirus B19 can cause ___________ in pregnant women
hydrops fetalis
organisms that cause impetigo
- Staphylococcus aureus (most common)
* group A streptococcus (S pyogenes)
acute skin infections following dog bite associated with what organism
*Pasteurella multocida (mouse-like odor; can also happen with cat bite) *staphylococci *streptococci *Capnocytophaga canimorsus
light microscopy of Candida fungi
budding yeasts (single cells) with pseudohyphae
mechanism most likely responsible for the antiseptic properties of alcohols (isopropanol, ethanol)
disruption of cell membranes; denaturation of proteins
what is needed to convert acyclovir to active form
monophosphorylation of acyclovir by a viral thymidine kinase (first and rate-limiting step)
more effective against herpes simplex virus and varicella zoster virus than cytomegalovirus and Epstein-Barr virus
hepatitis E- who does it infect? is it bad?
- occurs mainly in young and middle-aged adults living in Asia, sub-Saharan Africa, and Mexico
- typically self-limited and not associated with chronic liver disease or carrier state
- high mortality rate with infected pregnant omen
septic shock - features
infection with hypotension, tachycardia, tachypnea, and elevated or decreased body temperature
most important mediator of sepsis
tumor necrosis factor alpha (TNF-alpha)
-an acute phase cytokine produced by activated macrophages
hepatitis E-characeristics of the virus
virus=unenveloped, single-stranded RNA spread through the fecal-oral route
why use both chloroquine and primaquine for treating malaria?
chloroquine- treatment of choice of uncomplicated malaria
primaquine` added with infection with P vivax and P ovale to eradicate the intrahepatic stages , which are responsible for relapses of malari
human herpesvirus 6 (HHV-6): clinical significance
- cause roseola infantum
- febrile seizures
- high fever for several days followed by an erythematous maculopapular rash (starts on the trunk and spreads to face and extremities)
common cause of seizures in patients from Central and South America
Neurocysticercosis cause by Taenia solium, the pork tapeworm
imaging would find cystic brain lesion
mechanism of action of aminoglycosides
interfere with aminoacyl binding site on 30S ribosomal subunit
- causes cell to misread mRNA–> can’t make protein
- gain resistance by methylation of the aminoglycoside-binding portion of the ribosme
Clostridium tetani toxin mechanism of action
inhibit release of inhibitory neurotransmitters (GABA and glycine) from Renshaw cells in spinal cord
Clostridium tetani: how does the toxin travel in the body to cause problems
wound–> motor neuron axons–> spinal cord
Clostridium tetani- symptoms
Causes spastic paralysis, trismus (lockjaw), risus sardonicus (raised eyebrows and open grin), opisthotonos (spasms of spinal extensors)
areas of the face affected by cavernous sinus thrombosis
contiguous spread of an infection from the medial third of the face, sinuses (ethmoidal or sphenoidal) or teeth and ocular muccle
commonly caused by Staph aureus and streptococci
cysteine-tellurite agar used for
Corynebacterium diphtheriae, colonies are black in color, bacterium produces intracellular polyphosphate granules (metachromatic granules) detected with methylene blue staining
MacConkey agar used for
to grow enteric bacteria
bile salt-containing agar that restricts the growth of most Gram positive organisms
Q fever-what is it caused by?
zoonosis caused by Coxiella burnetti
inhalation of bacteria from air contaminated by animal waste (cattle/sheep amniotic fluid)
symptoms of Q fever
febrile illness (fever, fatigue, and myalgias), headaches (retroorbital and photophobia), pneumonia, normal keukocyte count, thrombocytopenia, increased liver enzymes
symptoms of trichomonas vaginalis
females vs males
female: vaginal burning, itching, urinary discomfort, and yellor/green vaginal discharge
male: urethritis… often aysymptomatic
what is Trichomonas vaginalis?
how to diagnose?
motile, flagellated protozoan; causes STI
saline microscopy (wet mount) of the discharge
protein A of Staphylococcus aureus
- virulence factor that forms part of the outer peptidoglycan layer
- binds Fc portion of IgG antibodies at complement-binding site, preventing complement activation
- prevent opsonization and phagocytosis
amphotericin B mechanism of action
binds the ergosterol of fungal cell membranes–> fungal cell lysis
binds to cholesterol too–> adverse effects (nephrotoxicity, hypokalemia, and hpomagesemia)
peniciillin and cephalosporin mechanism of action
- irreversibly binding to penicillin-binding proteins such as transpeptidases
- Block transpeptidase cross-linking of peptidoglycan in cell wall.
- Activate autolytic enzymes.
patients with CD4+ counts <50 cells/u should be administered prophylactic_________ to prevent mycobacterium avium complex (MAC)
azithromycin
HSV-1 and other herpesviruses are _________ and possess _______ genomes
enveloped; double-stranded DNA genomes
side effects of protease inhibitors (HIV antiretroviral meds)
hyperglycemia, lipodystrophy, and drug-drug interactions due to inhibition of cytochrome P450
mechanism of action- integrase inhibitor for antiviral therapy
disrupts HIV genome integration, prevent synthesis of viral mRNA
mechanism of action of isoniazid (INH)
inhibition of mycolic acid synthesis
need bacterial catalase peroxidase to convert to active form
mechanism of action of foscarnet
- Viral DNA/RNA polymerase inhibitor and HIV reverse transcriptase inhibitor. Binds to pyrophosphate-binding site of enzyme. Does not require any kinase activation.
- directly inhibits both DNA polymerase in herpesvirus and reverse transcriptase in HIV
- have to be given IV
Neisseria can be isolated by culture on __________ media such as the Thayer-martin VCN (vancomycin/colistin/nystatin) medium, which inhibits growth of contaminmants
selective
human papillomavirus- mechanism of action
integrate into the host genome and produce viral proteins E6 and E7–> interact with cell cycle regulatory proteins p53 and Rb, respectively
–> inhibit cell cycle regulation and evade of apoptosis
function of protein M of Streptococcus pyogenes
- inhibit phagocytosis and the activation of complement
- cytotoxic for neutrophils in serum and a mediator of bacterial attachment
- the target of type-specific humoral immunity to S. pyogenes
HBsAg
antigen found on surface of HBV; indicates hepatitis B infection
Anti-HBs
antibody to HBsAg; immunity due to vaccination or recover to hepatitis B
HBcAg
antigen associated with core of HBV
Anti-HBc
if IgM=acute/recent infection
IgG=prior exposure or chronic infection
HBeAg
indicates active viral replication and therefore high transmissibility and poorer prognosis
anti-HBe
indicates low transmissibility
ether and other organic solvents ______ the lipid bilayer that makes up the outer viral envelope
dissolve
–> loss of infectivity after exposure
mechanism of action of echinocandins (eg, caspofungin, micafungin)
antifungal medications that inhibit synthesis of polysaccharide glucan, an essential component of the fungal cell wall
side effect of ethambutol
optic neuropathy–> color blindness, central scotoma, and decreased visual acuity
reversible with discontinuation of drug
used to treat tuberculosis (RIPE-4 drug regimen)
allergic reaction to abacavir (nucleoside reverse transcriptase inhibitor used to treat HIV/AIDS is strongly associated with _______
HLA-B*57:01
this reaction is also called abacavir hypersensitivity reaction
adverse effects of aminoglycoside
ototoxicity (hearing loss, tinnitus) and nephrotoxicity
“fusion inhibitors” of antiretroviral medications
eg, enfuvirtide
drugs that selectively bind to the HIV transmembrane envelop protein gp41
*prevent conformational changes needed for viral membrane to fuse iwth the target cellular membrane
extended-spectrum beta lactamases produced by gram- negative bacteria–>
resistance to cephalosporins, penicillins, and other beta-lactam antibiotics
genes transmitted through plasmid conjugation
HPV tend to infect what type of epithelial cells
stratified squamous epithelium (anal canal, vagina, cervix, true vocal cords)
Haemophilus influenzae
(description of the bacteria, and what does it need to grow
gram-negative coccobacillus that requires oth X factor (hematin) and V factor (NAD+) to grow
what do IL-12 do?
stimulates the differentiation of “naive” T-helper cells into TH1
if deficient in IL-12–> won’t make IFN-gamma necessary for macrophages activation–> treated with IFN-gamma administration
what causes green discoloration of sputum during common bacterial infections?
presence of myeloperoxidase, a blue-green heme-based enzyme that is released from neutrophil azurophilic granules and forms hypochlorous acid (bleach)
acid-fast stain= the steps and what happens to those that are acid-fast
- apply aniline dye (eg, carbolfuchsin) to a smear and then decolorize with acid alcohol t
- Mycobacterium and Nocardia (weakly)= acid fast
sensitized TH2 cells secrete _____ and _____ and ______
IL-4; IL-13; IL-5
IL-4 and IL-13: promote B-lymphocyte class switching for IgE synethesis
IL-5: activates eosinophils and promotes IgA synthesis
why can’t Legionella pneumophila be detected on Gram stain
it is a gram-negative rod with a unique lipopolysaccharide chains on the outer membrane inhibiting the staining
what bugs can cause hepatic abscesses and how?
staph aureus- hematogenous seeding of the liver
enteric bacteria (e. coli, klebsiella, and enterococci)- ascend the bilitary tract, portal vein pyemia, or direct invasion from an adjacent area
mechanism of action of oseltamivir (Tamiflu)
neuraminidase inhibitor–> so block release of virus form infected cells
need to given within 48 hours of the onset of symptoms
which hepatitis virus is associated with hepatocellular carcinoma
B
side effect of isoniazid
heaptotoxicity, P-450 inhibition, drug-induced SLE, vitamin B6 deficiency, anion gap metabolic acidosis
what can be used as treatment of measles infection by reducing comorbidities, recovery time, and length of hospital?
vitamin A
why would proton pump inhibitor (omeprazole) increase the risk of getting Vibrio cholerae
vibrio cholerae is very sensitive to gastric acidity
so decreased gastric acid makes it easier for the infection to take place
how can Corynebacterium diphtheriae acquire virulence
via exotoxin encoded by beta-prophage
via bacteriophage-mediated “infection” with the Tox gene
daptomycin: mechanism, use, and adverse effects
lipopeptide antibiotic that disrupts cell membranes of gram positive coccid by creating transmembrane channels
for S. aureus skin infection
myopathy, rhabdomyolysis (increased creatine phosphokinase)
treatment for gonorrhea
ceftriaxone and azithromycin (a macrolide)
what is ganciclovir used for
antibiotic against cytomegalovirus- inhibit viral DNA polymerase
what type of virus can act as mRNA capable of using the host’s intracellular machinery for tranlation
purified RNA molecule that is single-stranded (SS) and positive (+) sense
treatment for oropharyngeal candidiasis in those who don’t have advanced immuodeficiency
nystatin- polyene antifungal and drug of choice for oropharyngeal candidiasis
bind to ergosterol in fungal cell membrane–> form pores and leakage of cell contents
nystatin not absorbed in GI and is administered as oral “swish and swallow” agent
what bacteria causes necrotizing fasciitis
Streptococcus pyogenes (group A strep)
lyme disease can be treated with doxycycline or
penicillin-type antibiotics such as cefriaxone
