Microbio Flashcards
What is the pathogenic mechanism for Shigella infection
Mucosal invasion of M cells
Three vulnerable populations for Shigella
Kids
men who have sex with men
adults in nursing facilities
The host inflammatory response against Shigella is largely mediated by
Neutrophils
What best explains lack of protective immunity agaiinst Neisseiria infections?
High variability of microbial surface antigenic structure
The Hib vaccine protects against
Encapsulated Haemophilus influenza meningitis
Non-encapsulated H influenzae cause
otitis media, sinusitis and bronchitis in little children
which part of the US is Blastomyces dermatitidis found?
Mississippi and Ohio River valleys
Symptoms of Blastomyces infection in immunocompetent
granuloma formation, mimics pneumonia
Mucor species is characteristic of patients with
neutropenia, burns or diabetes mellitus (diabetic ketoacidosis)
Risk factors for pneumocystis jirovecii infection in HIV pt
CD4 <200; oropharyngeal candidiasis
Prophylaxis for pneumocystitis jirovecii infection in HIV pt
Trimethoprim-sulfamethoxazole
Risk factors for Toxoplasma gondii infection in HIV pts
CD4 <100
Positive Toxoplasma IG antibody
Prophylaxis for Toxoplasma gondii in HIV pts
Trimethoprim-sulfamethoxazole
Risk factor for Mycobacterium avium infection in HIV pt
CD4 <50
Prophylaxis against Mycobacterium avium in HIV pt
Azithromycin
Risk factor for Histoplasma capsulatum infection in HIV pts
CD4 <150
Ohio and Mississippi river valley
Prophylaxis for Histoplasma infection in HIV pts
Itraconazole
How to distinguish TB infection from Mycoplasma avium complex infection in HIV patient?
MAC more likely presents with reticuloendothelial symptoms like hepatosplenomegaly, elevated alkaline phosphatase and LDH and anemia; grows best at 41C
What is the major virulence factor for Haemohphilus influenzae type b?
Polyribosylribitol phosphate (PRP) capsule that binds H1 and prevents complement deposition
How does diphtheria exotoxin function
Inhibits protein synthesis by ADP-ribosylation (inhibition) of intracellular EF-2
what does Diphtheria toxin cause morphologically
Respiratory cell necrosis with formation of fibrinous, coagulative exudates
Degradation of lecithin by lecithinase is a function of which pathogen
C. perfringens (causes gas gangrene)
Shiga toxin (Shigella) and Shiga-like toxin (EHEC) causes protein synthesis inhibition by
inactivation of 60s ribosomal subunit
How does pertussis AB exotoxin function
Catalyzes ribosylation of G protein alpha1 subunits leading to increased cAMP production.
Consequences of Pertussis exotoxiin
Increased insulin production, lymphocyte and neutrophil dysfunction and increased sensitivity to histamine
Example of a selective medium
Thayer-Martin VCN (identify Neisseiria species and fungi)
Example of differential media
MacConkey agar and Eosin methylene blue to culture enteric organisms (ferment lactose- pink on M, black on E)
Example and purpose of reducing media
Thioglycolate broth, culture anaeorbic organisms
What is the major virulence factor for Strep pyogenes
Protein M; inhibits phagocytosis and activation of complement
Most common cause of retinitis in HIV-positive patients
CMV
Treatment for CMV retinitis
Gancliclovir (guanine nucleoside analog with greater activity against CMV DNA polymerase)
Clarithromycin treatment for HIV patients
Mycobacterium avium complex
Flucytocine treats
Fungal infections including cryptococcal infections
Treats hepatitis B and C, hairy cell leukemia, condyloma acuminatum and Kaposi’s sarcoma
Leukocyte interferon alpha
Treats pneumocystis pneumonia
Pentamidine
Which cells play a key role in Myocobacterium tuberculosis infection?
CD4+ T cells, which recruit macrophages that form Langhans giant cells (have multple nuclei organized in shape of horseshoe)
Acute treatment of Corynebacterium diptheriae
- Diptheria antitoxin (passive immunization)
- Penicillin or erythromycin
- DPT vaccine
The clinical consequence of C. diptheria are due to
Exotoxin
S. Aureus uses this enzyme to activate prothrombin, convert fibrinogen to fibrin and protect itself against phagocytosis
Coagulase
Lecithinase (alpha toxin) is the major virulence factor for which pathogen
C. perfringens
Has phospholipase C activity that increases platelet aggregation and adherence molecule expression on leukocytes and endothelial cells, causing vasocclusion and necrosis of affected tissues
Lecithinase (alpha toxin) of C. perfringens
Oral thrush, interstitial pneumonia and severe lymphopenia in first year of life suggests
Vertical transmission of HIV from mother to child
Treatment for HIV pregnant woman to avoid vertical transmission
2 Reverse transcriptase inhibitors + protease inhibitor/non-nucleoside RT inhibitor, or integrase inhibitor
Which anti-HIV therapy is teratogenic?
Efavirenz in first 8 weeks
Zidovudine usage in infants is for
HIV prophylaxis if they were born to HIV-infected mothers
NRTI therapy that is associated with hypersensitivity reaction in individuals with HLA-B*57:01 allele
Abacavir
NNRTIs associated with Stevens-Johnson syndrome and toxic epidermal necrolysis and abnormal LFTs
Efavirenz and Nevirapine
NRTI associated with asymptomatic macular rash on palms or soles
Emtricitabine
HIV therapy that causes hyperglycemia, GI symptoms and lipodystrophy
Protease inhibitors (lopinavir)
White patches on retina in patient with pneumocystis pneumonia implies
CMV retinitis (pts with CD4 <50)
Standard tx for Chlamydia
Macrolide (azithromycin– protein synthesis inhibitor) and Cephalosporin
Why is probenecid co-administered with Penicillin in treatment of neurosyphillis or gonorrhea?
Inhibits organic ion transporters in kidney and renal tubular secretion of Penicillin– Increases penicillin serum concentration
Function of M protein on Streptococcus bacteria
Prevents opsonization and destruction by complement
Function of Protein A in Staph Aureus
Binds Fc of immunogloblulins to prevent opsonization
