SG6: Infectious Disease Flashcards
What clinical signs, symptoms, and laboratory tests are consistent with pneumonia?
- Fever, tachypnea, tachycardia, a productive cough, and a change in the amount or character of the sputum are common in patients with pneumonia.
- pleuritic (knifelike) chest pain and examination of the chest shows splinting and an inspiratory lag on the right side during inspiration.
- hypoxemic (low PO2 of 68 mmHg).
What are the major causative organisms of community-acquired pneumonia?
Streptococcus pneumoniae remains the most commonly identified pathogen in community-acquired pneumonia.
Atypical pathogens (Mycoplasma, Legionella, and Chlamydia) account for 10% to 20% of all cases.
How should A.T. be treated? Describe risk stratification. Should A.T. be admitted to hospital?
The initial management decision after the diagnosis of CAP is to determine the site of care: outpatient, hospitalization in a medical ward, or admission to an ICU.
Prognostic models: Pneumonia Severity Index (PSI) and CURB-65
PSI stratifies patients into five risk categories. Taking into account AT’s age, history of chronic renal insufficiency, RR, and altered mental status,
A.T. is admitted to hospital. What is the recommended treatment for AT? What is the recommended treatment for outpatients?
Treatment should be started empirically with antibiotics pending identification of the etiologic bacteria. The choice should be guided by the results of the sputum Gram stain, patient age, medical history, concomitant diseases, place of residence, and clinical signs and symptoms.
OUTPATIENT TREATMENT
1. Previously healthy and no use of antimicrobials within the previous 3 months
- A macrolide
- Doxycyline
- Presence of comorbidities such as chronic heart, lung, liver or renal disease; diabetes mellitus; alcoholism; malignancies; asplenia; immunosuppressing conditions or use of immunosuppressing drugs; or use of antimicrobials within the previous 3 months (in which case an alternative from a different class should be selected)
- A respiratory fluoroquinolone (moxifloxacin, gemifloxacin, or levofloxacin)
- A β-lactam plus a macrolide
II. INPATIENTS, NON-ICU TREATMENT
- A respiratory fluoroquinolone A β-lactam plus a macrolide
III. INPATIENTS, ICU TREATMENT
- A β-lactam (cefotaxime, ceftriaxone, or ampicillin-sulbactam) plus either azithromycin or a respiratory fluoroquinolone.
- For penicillin-allergic patients, a respiratory fluoroquinolone and aztreonam are recommended.
C. diff colitis rx
- Oral metronidazole (DOC) and oral vancomycin have similar efficacy
- If the patient is unable to tolerate PO, metronidazole may be administered IV. IV vancomycin is ineffective for CDAD (100% renal excretion).
- Fidaxomicin may be an appropriate therapy in patients with recurrent C Difficile infection, or perhaps as initial therapy in patients at high risk of developing recurrent disease, although parameters for its most appropriate use are still being defined.
What is the recommended treatment for infective endocarditis?
For acutely ill patients empirical therapy may be necessary. Such empirical therapy should be administered ONLY after 3 sets of blood cultures have been obtained from separate venipunctures (avoid FN).
- prosthetic valve: vanco + Gentamycin (+Rifampin)
- Linezolid or daptomycin are options for patients with intolerance to vancomycin or resistant organisms.
Penicillin-Susceptible Strains (MIC <0.12 μg/mL)
- Penicillin G or Ceftriaxone or
- Penicillin G plus gentamicin or
- Ceftriaxone plus gentamicin
Relatively Penicillin-Resistant Strains (MIC > 0.12 and < 0.5 μg/mL)
- Penicillin G high dose plus gentamicin or
- Ceftriaxone plus gentamicin
Strains with MIC > 0.5 μg/mL
- Ampicillin plus gentamicin or
- Penicillin G high dose plus gentamicin
What are the main indications of aminoglycosides? What is the rationale of combining a β-lactam antibiotic with an aminoglycoside?
Antibacterial spectrum of the aminoglycosides is directed primarily against aerobic gram-negative bacteria.
Aminoglycosides are almost always used in combination with β-lactam antibiotics to extend coverage to include potential gram-positive pathogens and to take advantage of the synergism between these two classes of drugs: β-lactams inhibit cell wall synthesis and thereby increase the permeability of the bacterium to the aminoglycosides.
What are the potential adverse effects of aminoglycosides?
- Nephrotoxicity: Generally reversible. Usually occurs after 5-7 days of therapy. Risk factors: dehydration, age, dose, duration, concurrent nephrotoxins, liver disease.
- Ototoxicity: Often irreversible. Both cochlear and vestibular toxicity occur.
What are the therapeutic options for treating S. aureus endocarditis?
Oxacillin-Susceptible Strains
- Nonpenicillin-Allergic Patients: Nafcillin or oxacillin with optional addition of gentamicin
- Penicillin-allergic (nonanaphylactoid) patients: Cefazolin with optional addition of gentamicin
Oxacillin-Resistant Strains
- Vancomycin
Cardiac Conditions for which Prophylaxis is Recommended
- Prosthetic cardiac valves
- Previous infective endocarditis
- Congenital heart disease (CHD)
- Cardiac transplant recipients with valvulopathy
Recommended Endocarditis Prophylaxis During Oral-Dental Or Respiratory Tract Procedures
- Standard Regimen: Amoxicillin (oral)
- Allergic to penicillin (oral): Clindamycin or Cephalexin or Azithromycin or clarithromycin
- Allergic to penicillin: Clindamycin IV or Cefazolin IV
What are the major causative organisms of acute pharyngitis?
- Acute pharyngitis is most common in children 5 to 15 years of age and is rare before 3 years of age.
- The etiology is typically viral, but bacteria such as group A streptococci (GAS, Streptococcus pyogenes), groups C and G streptococci, Neisseria gonorrhoeae, Mycoplasma pneumoniae, and Chlamydia pneumoniae may also cause pharyngitis in children.
GAS vs viral pharyngitis
GAS tonsillopharyngitis: sudden onset of throat pain, fever, headache, abdominal pain, nausea, vomiting, tonsillopharyngeal edema, enlarged anterior cervical lymph nodes, soft palate petechiae, and a scarlatiniform rash.
Viral: rhinorrhea, cough, conjunctivitis, and viral rash.
GAS pharyngitis rx
- Penicillin V remains the treatment of choice because of its proven efficacy and safety, its narrow spectrum, and its low cost. Penicillin-resistant GAS has never been documented.
- Amoxicillin is often used in place of penicillin V as oral therapy for young children; the efficacy appears to be equal. This choice is primarily related to acceptance of the taste of the suspension.
- Most oral antibiotics must be administered for 10 days to achieve maximal rates of pharyngeal eradication of GAS.
- Intramuscular benzathine penicillin G therapy is preferred for patients deemed unlikely to complete a full 10-day course of oral therapy.
- In patients with a type I hypersensitivity to penicillins, azithromycin, clarithromycin, or clindamycin may be used.
- In those with a non–type I allergy to penicillin, a first-generation cephalosporin (e.g. cephalexin) may be considered.
Syphillis rx?
- Recommended therapy is a single IM dose of benzathine penicillin G.
- Parenteral penicillin G is the only therapy with documented efficacy for syphilis during pregnancy.
- Penicillin-allergic Pt: Doxycylcine
