By: Dr. Geoffrey Modest
A review article in NEJM on community acquired pneumonia (see DOI: 10.1056/NEJMra1312885). Some points:
–Pneumococcal pneumonia (from staph pneumoniae) was 95% of cases of pneumonia in pre-antibiotic era, now 10-15% [though the studies cited were predominantly for patients hospitalized with community-acquired pneumonia (CAP). I suspect that for the vast majority, we just don’t know — partly because we do not get cultures or even gram stains of people coming in with “walking pneumonia” and not hospitalized, partly because the etiology may be different in those with non-hospitalized cases, and partly because the etiology may vary dramatically from one area to another]
–Changes in ecology likely related to use of pneumococcal vaccine in adults, near universal use of conjugate vaccine in kids, and decreased smoking (vs. in Europe and other places, where less widespread use of vaccine and higher rates of smoking, pneumococcus assoc with more CAP).
–Other CAP causes in US include H flu, staph, moraxella catarrhalis, psuedomonas aeruginosa and gram negatives; mycoplasma and chlymydophila pneumoniae vary widely, in part depending on diagnostic testing used. For COPD, P. aeruginosa and gram negatives more common, esp. in those on steroids.
–During influenza, more viral pneumonia but also more bacterial super infections [including staph]
–Other viruses important (RSV, parainfluenza, metapneumovirus, adeno, corona, rhinoviruses), causing both pneumonia and secondary bacterial infections
–In terms of presentation, important to remember that some (esp. elderly) do not cough, produce sputum, or have elevated white count, and 30% (esp. elderly) are afebrile when hospitalized [?? even more in those seen in outpatient settings]
–Workup: authors favor gram stain (but need good specimen, with >10 inflammatory cells for each epithelial cell), culture, blood cultures, urine testing for legionella and pneumococcal antigens, PCR for mycoplasma and chlamydophila, and serum procalcitonin (since if –??outpatient vs. inpatient treatment: there are an array of validated instruments to help determine if patient should be hospitalized (see here for the Pneumonia Severity Index. But can also use the CURB-65 and the IDSA/ATS guidelines)
–Empiric therapy: IDSA/ATS guidelines — for those without coexisting disease (eg chronic heart, lung, liver, or renal disease; diabetes; alcoholism; cancer or immunosuppressing conditions; or use of antibiotics in past 3 months), use a macrolide (if <25% of pneumococcal in community have high-level resistance) or doxycycline. For those with coexisting disease, use levofloxacin/moxifloxacin alone or a beta-lactam (eg amoxacillin-clavulanate) plus a macrolide (this regimen works 90% of the time). The authors favor a bata-lactam, since most clinicians do not know the prevalent resistance patterns, pneumococcus is more susceptible to penicillins than macrolides, and if not prompt response, can always substitute macrolide or doxy. And they would choose a beta-lactam, since 1/3 of h. flu and majority of Mor. catarrhalis are resistant to penicillins. For IDSA/ATS guidelines, see here.
–Duration of therapy: 5 days are as good as 10 (though it seems that clinicians have increased duration from 10 to 14 days!!). So they recommend 5-7 days