Micro 1 Flashcards
Route of entry for S. aureus meningitis
direct inoculation of surgical procedure or postoperatively through the wound - common in neurosurgical pts
Facultatively intracellular, motile, gram-positive rod that is the 3rd most common cause of meningitis in neonates
Listeria monocytogenes
also causes meningitis in IC pts and elderly
What are the CSF findings in bacterial meningitis?
- increased neutrophils
- increased protein
- decreased glucose
Lancet-shaped gram-positive cocci in pairs
Streptococcus pneumoniae
Leading cause of CAP, otitis media, and meningitis in adults
S. pneumo
What food poisoning is most commonly associated with mayonnaise-containing food like potato or macaroni salad?
S. aureus staphyloenterotoxemia containing highly heat-stable preformed enterotoxin
What are 4 strains of bacteria that result from exotoxin formed after ingestion of the contaminated food?
- ETEC and V. cholera: watery diarrhea
- EHEC and shigella: bloody diarrhea
What are 5 bacteria that invade the gut mucosa?
- Salmonella spp
- Shigella
- Yersinia enterocolitica
- EIEC
- C. jejuni
What is the mode of transmission for staphylococcal food poisoning?
food handler innoculating food with S. aureus and allowing food to incubate at room temperature
Multinulcated giant cells with some intranuclear inclusions + a clinical Hx of vesiculoulcerative gingivitis/lesions of oral mucous membranes and cervical lymphadenopathy in children ages 1-3
HSV1: herpetic gingivostomatitis
may be VZV, but HSV-1 more likely
Reactivation of what virus produces interstitial pneumonitis, retinitis, hepatitis, colitis, and/or generalized disease?
CMV
What could a chronic, transforming latent EBV virus resultin?
B-cell lymphoma
What are two examples of slow viruses that are degenerative disorders of the CNS?
SSPE nd progressive multifocal leukoencephalopathy
Neutropenia associated with leukemias and lymphomas are associated with what monomorphic mold?
Invasive aspergillosis
What is the mode of transmission of invasive aspergillosis?
hematogenous spread - tissue infarcts in skin, paranasal sinuses, kidneys, endocardium, and brain
Oval budding yeast with pseudohyphae (elongated yeast cells)
Candida albicans
Oval budding yeast with a thick capsule and india ink stain of CSF revealing wide clear zone around nucleus
Cryptococcus neoformans
What leads to the autoimmune response of rheumatic fever?
molecular mimicry between bacterial antigens and self antigens
What are the early and late findings of rheumatic fever?
early: migratory arthritis, pancarditis, subQ nodules, erythema multiforme, and sydenham chorea
late: mitral stenosis with rare involvement of aortic valve
Prevention of rheumatic fever complications
prompt Tx of streptococcal pharyngitis with penicillin
Do all strains of S. pyogenes have the ability to result in PSGN?
No, only the nephritogenic strains
What is the recommended treatment for methicillin-resistant S. epidermidis?
Vancomycin combined with rifampin or gentamicin or both
What are the complications of S. epidermidis endocarditis after valve replacement if untreated?
intracardiac abscess formation, dehiscence of the prosthetic valve from the heart, and septic embolization
What are 3 B-lactamase resistant penicillins?
methicillin, oxacillin, and nafcillin
Why is the anaerobic environment within a can conducive to C. botulism?
It allows spore germination and organism growth
is the botulism toxin actively secreted by the bacteria?
NO!!!!!!!!!!
The botulinum toxin produced by the vegetative bacteria remains intracellular until autolysis releases the potent neurotoxin into the food
What are the clinical manifestations of the 3Ds associated with botulism?
diplopia, dysphagia, and dysphonia
12-46h after consumption
What are the Tx strategies for botulism?
antitoxin for circulating toxin and
supportive measures like intubation and mechanical ventilation for diaphragmatic paralysis
What kind of infection is B. fragilis found in?
intraabdominal abscess - often polymicrobial with B. fragilis and E. coli being the most prominent
-B. fragilis is an anaerobic, gram negative bacillus
What kind of S. pneumo vaccine is given to children <2yo?
7-valent conjugated vaccine which contains polysaccharide antigens that are protein-coupled in order to stimulate the T cell immune response
6 live, attenuated vaccines?
MMR, rotavirus, VZV, and Sabin polio vaccine
Recombinant surface protein vaccine?
HBV
4 killed bacteria vaccines?
anthrax, cholera, pertussis, and plague
4 killed viral vaccines?
HAV, influenza, rabies, and Salk polio
2 inactivated toxin vaccines?
diptheria and tetanus
unconjugated polysaccharide vaccine that does not stimulate a helper T response
pneumococcal vaccine
Pt with COPD presents with high fever with relative bradycardia, headache and confusion, and watery diarrhea. Labs show hyponatremia, gram stain with many neutrophils but few or no organisms. What is the Dx and Tx
Legionella - respiratory FQs or newer macrolides
San Joaquin Valley Fever
Coccidioidomycosis
Why is mycoplasma pneumoniae often accompanied with a mild anemia?
Mycoplasma can cause hemolysis d/t antigenic similarity between itself and cell membranes of RBCs. When the immune system ounts a response against M. pneumoniae antigens, it also destroys some RBCs. After the infection has been eliminated and the immune system is no longer activated (faded), anemia resolves.
What are 4 notable intracellular organisms?
Salmonella, N. gonorrhoeae, Chlamydia (obligate), and Rickettsia (obligate)
What is the Tx for obligate intracellular protozoan that commonly infects HIV pts and shows spherical lesions in brain on MRI?
Toxo - Pyrimethamine and Sulfadiazine
-TMP-SMX for prophylaxis
How are the presentations different for oral candidiasis and oral hairy leukoplakia?
Oral thrush is found in denture wearers, diabetics, and IC pts. It can be scraped off.
Tocacco use can cause leukoplakia, a precancerous lesion that manifests as white patches that cannot be scraped off.
What are 4 naturally competent bacteria that undergo direct uptake of naked DNA from the environment via transformation?
- S. pneumo
- H. flu
- N. gonorrhoeae & meningitidis
How do nonvirulent, non-capsule-forming strains of S. pneumo acquire genes that code for capsule?
transformation
A 25yo female presents to clinic with lower abdominal pain and scant bloody vaginal discharge. She als has a fever, rebound ab tenderness, purulent endocervical discharge, and cerivcal motion and adnexal tenderness on bimanual exam. She has been sexually active with multiple partners without using condoms. She has orthostatic hypotension and has a positive pregnancy test. What is most likely Dx and causitive agent? What is she most at risk for?
PID - either N. gonorrhoeae or C. trachomatis
-She is at risk for ectopic pregnancy
What is the most likely route of entry of Neisseria meningococci into the blood and what virulence factors does it use?
Meningococci have pili which mediate adherence and penetration of mucosal epithelium and pharyngeal colonization. IgA protease facilitates survival or organisms in mucosa by destroying IgA Abs.
How do meningogoccal pili play a role in the route of entry into the body?
They are responsible for epithelial attachment to the nasopharynx.
Cell receptor for CMV
cellular integrins
Cell receptor for EBV
CR2 (CD21)
Cell receptor for HIV
CD4 and CXCR4/CCR5
Cell receptor for Rabies
nAChR
Cell receptor for Rhinovirus
ICAM1 (CD54)
Single-stranded RNA viruses enveloped by a bullet-shaped capsule studded by glycoprotein spikes that bind to nicotinic ACh receptors
Rabies
The vaccine that provides protection against H. flu contains PRP capsular polysaccharide of H. flu type b as well as diptheria toxoid. The conjugated diptheria toxoid to the polysaccharide in this faction functions to:
increase immunogenicity - the additional protection form the protein-PRP polysaccharide conjugate vaccine results from T-cell dependent stimulation of B-lymphocytes to undergo class switching from IgM –> IgG
What is the MOA of doxycycline, tetracycline, and minocycline?
antibiotics that inhibit the bacterial 30S ribosomal subunit
What is the MOA of chloramphenicol?
It is an anti-ribosomal antibiotic that acts to inhibit the 50S bacterial ribosomal subunit
What are the only classes of antibiotics that diminish the ability of gram positive and gram negative bacteria to survive in osmotic stress?
Penicillins, cephalosporins, and vancomycin - disrupts peptidoglycan cell wall
How do picornaviridae replicate?
They produce a polyprotein product that is cleaved by a specific viral protease which converts their polycistronic mRNA into monocistronic mRNA
Classic triad for congenital toxoplasmosis
hydrocephalus, intracranial calcifications, and chorioretinitis
How is congenital toxoplasmosis transmitted?
Transplacentally (in utero) - the fetus is affected only if the mother is infected during the first 6 mo. of pregnancy
What are the functions of the two toxins in C. diff?
- Toxin A (enterotoxin): acts as a neutrophil chemoattractant leading to mucosal inflammation, loss of water into the gut lumen (producing diarrhea), and mucosal death
- Toxin B (cytotoxin): causes actin depolymerization, loss of cellular cytoskeleton integrity, cell death, and mucosal necrosis
How do the toxins of Shigella (Shiga toxin) and EHEC (Shiga-like toxin) cause bloody diarrhea?
They inhibit ribosomal protein synthesis
What are the main functions of Group A strep M Protein?
It inhibits phagocytosis and complement activation, mediates bacterial adherence, and is the target of type-specific humoral immunity to S. pyogenes
Walking pneumonia with CXR that looks much worse than clinical presentation and organism requires cholesterol to grow
Mycoplasma - cell membrane is composed of single cholesterol-rich phospholipid bilayer
What are the 5 important steps to prevent central venous catheter infections?
- proper hand washing
- full barrier precautions during insertion of central line
- chlorhexidine for skin disinfection
- avoidance of femoral insertion site
- removal of catheter(s) when no longer needed
MOA of alcohol (isopropanol, ethanol) disinfectant
disruption of cell membranes and denaturation of proteins
MOA of Chlorhexidine disinfectant
disruption of cell membranes and coagulation of cytoplasm
-antiseptic of choice for many surgical and percutaneous procedures
MOA of hydrogen peroxide disinfectant
produces destructive free radicals that oxidize cellular components; sporicidal
-excellent for fomites
MOA of iodine disinfectant
halogenation of proteins and nucleic acids; sporicidal
What infection is strongly associated with AIDS-related primary CNS lymphoma
latent EBV infection composed of B-lymphocytes
How is listeria transmitted to cause neonatal meningitis?
transplacentally or via vaginal contact
gram positive rod with V or L formations with tumbling motility
listeria monocytogenes
What is the most common cause of acute bacterial arthritis in sexually active young adults?
N. gonorrHOeae
dem bitches be hos
What is the most common cause of septic arthritis in children and non-sexually active adults?
S. aureus
Broad-based budding encapsulated yeast endemic to Great Lakes, OH, and MS River valey present in soil and rotten organic matter
Blastomyces
What is the best method to Dx C. diff colitis?
PCR detection of toxin A and B genes in the stool
What things besides syphilis does VDRL test positive for?
V: viruses (mono and hepatitis) D: drugs R: rheumatic fever L: lupus and leprosy -requires mixture of cardiolipin, lecithin, and cholesterol
What are the 3 components of LPS and which one is responsible for the toxic properties of LPS that leads to gram-negative septic shock?
O antigen, core polysaccharide, and Lipid A
*Lipid A is responsible
How does Lipid A induce shcock?
It activates macrophages and granuloctes and production of endogenous pyrogens and inflammatory mediators like IL-1, TNF-a, and IFN
What E. coli virulence factor is important for neonatal meningitis?
K-1 capsule antigen
What are clue cells?
vaginal squamous epithelial cells covered in small dark particles (G. vaginalis) in BV
What is the Tx for BV?
oral metronidazole
How does S. typhi invade the gut mucosa?
S. typhi penetrate the gut mucosa via transporters on enterocytes and via phagocytosis by M cells in Peyer patches
What are the clinical manifestations of S. typhi?
mild abdominal cramping with low grade fever and diarrhea OR constipation initially; subsequently pt can develop rose spots on abdomen, HSmegaly and recolonization of the gut leading to hemorrhagic diarrhea and sepsis with bowel perforation
How does TSST-1 activate a widespread T cell response?
It interacts with the MHC molecules on APCs and the variable region of the T lymphocyte receptor which leads to release of IL-2 from T cells and IL-1 NAD tnf FROM MACROPAHGES
How do the causative factors of PSGN and Rheumatic Fever differ?
PSGN can be caused by GAS impetigo or streptococcal pharyngitis, whereas rheumatic fever is only associated with streptococcal pharyngitis
4 autoimmune disorders associated with HLA-B27
PAIR P: psoriatic arthritis A: ankylosing spondylitis I: IBD R: reactive arthritis
alpha-hemolytic, optochin-resistant
Viridans strep
beta-hemolytic, bacitracin-resistant
Strep agalactiae
gamma-hemolytic, growth in bile AND 6.5% NaCl
Enterococci
gamma -hemolytic, growth in bile but NOT 6.5% NaCl
Nonenterococci S. bovis
What is the classic triad for congenital rubella?
congenital cataracts (white pupils), sensory-neural deafness, and PDA -can also present with microcephaly and MR
Why is a live, attenuated vaccine frequently more effective than a viral component or killed vaccine?
Viral component/killed vaccine induce only humoral immunity, whereas live-attenuated vaccines induce both humoral and CMI
What is leukocyte IFN-a currently approved to treat? How does it work?
HBV, HCV, hairy cell leukemia, condyloma acuminatum, and KS
-it inhibits various stages of viral RNA and DNA synthesis
What kind of viruses can be destroyed by ether?
enveloped viruces (nonenveloped - resistant to ether)
