Influenza Treatment & HAP/VAP Microbiology

Study Notes

Neuraminidase inhibitors should be given regardless of symptom onset or setting.
Adjunctive corticosteroids are not routinely added unless there's shock refractory to fluid resuscitation and vasopressor support; they are not beneficial in non-severe cases and have conflicting mortality benefit data in severe cases.
Continue antibiotics; consider discontinuation if cultures are negative, procalcitonin is low, and the patient shows early clinical stability.
Switch from IV to PO medication when the patient tolerates oral nutrition and medication, with no contraindications to oral therapy.
Afebrile for 48-72 hours and clinical stability are criteria for switching from IV to PO medication.

Common causative organisms include Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Acinetobacter, Stenotrophomonas maltophilia, and Enterobacteriaceae.

Empirical antibiotics should cover S. aureus, P. aeruginosa, and other gram-negative bacilli (e.g., piperacillin-tazobactam, cefepime, levofloxacin, imipenem, or meropenem).
Add an agent active against MRSA (vancomycin or linezolid) empirically if indicated.
For Pseudomonas coverage, two different antibiotic classes with activity against P. aeruginosa should be used empirically if there's prior IV antibiotic use within 90 days, high mortality risk (e.g., ventilatory support due to HAP, septic shock, structural lung disease), or if treatment failure is suspected. Otherwise, a single antibiotic with activity against P. aeruginosa may suffice.

Empirical antibiotics should cover S. aureus, P. aeruginosa, and other gram-negative bacilli (e.g., piperacillin-tazobactam, cefepime, levofloxacin, imipenem, or meropenem).
Add an agent active against MRSA (vancomycin or linezolid) empirically if there's prior IV antibiotic use within 90 days or epidemiologic data showing >10-20% of S. aureus as MRSA.

Three consecutive early morning sputum samples:
- Acid-fast bacilli smear
- Culture (2-4 or 8 weeks)
Chest radiography
Nucleic acid amplification (RNA and DNA).

Isoniazid (INH): Inhibits mycolic acid synthesis; adverse effects include peripheral neuropathy (pyridoxine may help) and hepatotoxicity.
Rifampicin: Inhibits bacterial RNA synthesis; adverse effects include reddish-orange discoloration of body fluids and potent CYP3A4 induction.

HIV-coinfected: Isoniazid 300mg/day for 9 months, or 900mg twice weekly for 9 months with directly observed therapy (DOT).
Non-HIV-infected: Isoniazid 300mg/day or 900mg twice weekly for 6-9 months (9 months preferred), rifampin 600mg/day for 4 months, or rifapentine 900mg plus isoniazid 900mg/week for 12 weeks (with DOT).

Affects any body part other than lungs; presents as slow organ function decline, low-grade fever, and organ-related symptoms.
Treatment uses four first-line medications (isoniazid, pyrazinamide, ethambutol, rifampicin) for two months, followed by continuation phase (duration varies by site).
Treatment duration: 9-12 months (CNS), 6-9 months (bone/joint), 6 months (other sites). Other medications such as ethionamide, levofloxacin, and/or streptomycin may be included.

Latent TB: 4-month rifampin (4R), 3-month isoniazid and rifampin (3HR), or 6- or 9-month isoniazid (6H or 9H).
Active TB: Isoniazid, rifampin, and ethambutol for 2 months, followed by isoniazid and rifampin for 7 months (9 months of INH, RIF, and EMB is also mentioned).
Pregnant women taking INH should take pyridoxine (vitamin B6) 25-50mg/day. The use of pyrazinamide during pregnancy is controversial. Experts suggest including it in cases of HIV co-infection, extrapulmonary or severe TB.

Peripheral Neuropathy: Pyridoxine (vitamin B6), 25-50mg/day with isoniazid for at-risk individuals; 100mg/day for existing neuropathy.
Optic Neuritis (from ethambutol): Baseline visual acuity and color discrimination tests, monthly color discrimination tests during treatment; discontinue ethambutol if visual abnormalities are found. If vision doesn't improve after stopping ethambutol, INH should also be stopped as it's a rare cause. A petechial rash is more concerning and suggests thrombocytopenia from a rifamycin (ie, RIF, RFB, RPT) hypersensitivity. Drugs are stopped if a generalized erythematous rash occurs.