Infectious Disease – 3 (Lower Respiratory Tract)

In terms of infections, the lower respiratory tract diseases are Bronchitis & Pneumonia.  The former is easiest to deal with.

BRONCHITIS

Bacterial infections of the bronchi — No Such Thing!  Acute Bronchitis is always viral.  I hate to say “always,” but for practical purposes, here it applies.  Think of all your colleagues who “Give a Z-pack” (i.e. short-course azithromycin), & giggle under your breath.  What happens is that they hear rhonchi in the lungs, don’t call it “asthma,” wind up with an “–itis,” & are too chicken to not give an antibiotic.

First time episode, we shouldn’t say “asthma.”  But wheezes, rhonchi, or just a long expiratory phase, are all equivalent — it’s bronchospasm.  No fever, so it’s not a pneumonia [which gives rales].  Acute lower respiratory illness and no pneumonia = bronchitis = virus!!!  Give albuterol.

Actually, Pertussis is a form of bronchitis, though lung sounds are usually normal.  But treatment probably won’t help.  I reserve it for anyone with paroxysmal cough (maybe with post-tussive vomiting), not getting better, and especially contact with unimmunized infant.  It’s the latter who dies.  See our posting Acute Cough – 1 (at the end of post).

COPD patients, especially smokers, can have an Acute Exacerbation of Chronic Bronchitis.  If it includes purulent sputum (overgrowth of baseline airway colonization), treat with antibiotics.  The target Bugs: Pneumococcus & H. Flu.  The Drugs:

•  Amoxicillin              •  Azithromycin                                   •  Doxycycline
•  Cefuroxime              •  Amoxicillin + clavulanate                •  TMP-SMX
 

For patients with frequent recurrences, vary the antibiotic.  Respiratory quinolones like levofloxacin are also approved (and certainly marketed) for the condition, but OMG!!!  NEVER give them for anything but admission-sparing pneumonia.

Click here for Common Antibiotic Doses.  Onward to…

COMMUNITY-ACQUIRED PNEUMONIA (CAP)

We conceptualize CAP (standard abbreviation you’ll see in the literature) in terms of “Pyogenic” (“makes pus”) & “Atypical”.  The former has as its prototype Pneumococcal Pneumonia — abrupt onset, purulent sputum, lobar consolidation on CXR.  The latter is like Mycoplasma — more gradual onset, diffuse infiltrates on film.

Pyogenic Pneumonia  —  the Bugs

Common
•  Pneumococcus
•  H. flu
 
Uncommon
•  Strep pyogenes
•  Staph aureus
•  E. coli & other enterics
•  Klebsiella pneumoniae
•  Pseudomonas
 
 
VERY Rare (hopefully)
•  Anthrax, plague, tularemia, hantavirus, Q fever, SARS
Comments
> Community Acquired Pneumonia (CAP)
> CAP
 
 
> CAP, Complication of Influenza
> IV drug user; Complication of Influenza
> Nosocomial; debilitated
> Diabetes, cancer, alcoholics
> Underlying lung disorder; nosocomial; immunocompromomised
 
 
> Agents of Bioterrorism (Very ill; CXR variable)

“Atypical” Pneumonia  —  the Bugs

Common
•  Mycoplasma pneumoniae
•  Chlamydophila  pneumoniae
     – aka Chlamydia pneumoniae
•  Viral influenza
  
Less Common
•  Legionnaires’
 
 
•  Tuberculosis
•  Endemic fungi
     – histoplasmosis,
  blastomycosis
     – coccidioidomycisis
•  Psittacosis
•  Pneumocystis
Comments
> Usually youngish
> Usually middle-aged or older
 
> Anybody
  
 
> Common-source outbreaks
(e.g. water coolers)  [Usually ill enough to need admission]
> Lived in endemic areas
> Lived in endemic areas
     – Ohio River Valley, 3rd World
 
     – Calif. Central Valley, Arizona
> Parrot exposure
> AIDS, organ transplants, etc.

This is not to say that “Atypical” Pneumonia is milder.  For example, Pneumocystis has 100% mortality untreated.

The following discussion assumes the patient isn’t sick enough to warrant admission (see posting Acute Cough – 2).

Unfortunately, studies show that there’s no good way to distinguish the microbiologic etiology of CAP, not clinically nor radiographically!  That’s because Pneumococcus is easily overgrown in sputum, thus hard to culture out.  Two classic studies (which, alas, I cannot locate any more) —

  1. Among pts. with infiltrate on CXR & Pneumococcus in blood culture (can’t get a better gold standard than that), only 50% grew the bug in sputum.
  2. Everybody leaving a clinic (usually asymptomatic) was asked to spit in a cup; lab techs sought exhaustively (for purpose of study) & found Pneumococcus in 50% of specimens.

So major professional organizations recommend empiric treatment for CAP based on risk factors, but don’t quite agree among themselves.  DiagnosisDude also chimes in.

North American Treatment Guidelines *

Otherwise-Healthy Outpatients
  • Macrolides:  Azithromycin, Clarithromycin
  • Doxycycline (acceptable alternative)
Patients with Risk of Drug-Resistant Pneumococcus
  • Respiratory Fluoroquinolone (e.g. Levofloxacin)
  • Amoxicillin-clavulanate, high-dose (4 gm/d) plus a macrolide.
*  American Thoracic Society & Infectious Disease Society of America; Canadian Thoracic Society agrees.  Click for North Amer. CAP Guidelines.
¶  Risks of Drug-Resistant Pneumococcus:
•  Antibiotics within past 3 months    •  Hospitalization within past month
•  Alcoholism              •  Immunocompromise            •  Homeless Shelters
•  Long-term care facilities                  •  Multiple medical co-morbidities
•  Exposure to day-care (or to a child in day-care)
 

British Thoracic Society § and American Academy of Pediatrics  

  • Amoxicillin 500mg – 1,000 mg T.I.D. (90 mg/kg/d)
  • Pen-Allergic:   a macrolide
§  See Lim WS, Baudouin SV, George RC et al.  Thorax 2009;64 (Suppl 3):1-55. (couldn’t find a link for non-subscribers).
‡  Click for the AAP’s first-ever Pediatric CAP Guidelines.
 

Why the difference?????  The North Americans worry about “atypicals” like Mycoplasma and Chlamydophila [new name change from “Chlamydia pneumoniae,” so patients don’t think they got a sexually-transmitted pneumonia].  The Brits (& U.S. Peds) only care about the real killer — Streptococcus pneumoniae (Pneumococcus).

I should move to the U.K.  In my mind, only care about Pneumococcus.  It’s likely the main culprit.  Mycoplasma is usually self-limiting.  There are case reports of bad outcomes, but those are isolated.  The pediatric literature carries some suggestion that Mycoplasma may be causal of asthma, but no firm long-term data.

However, what is for sure is that more & more Pneumococcal resistance to azithromycin is emerging.  Rates are commonly >30%, I’ve anecdotally heard of up to 50%.  So do we opt to protect patients from ill-defined sequelae of Mycoplasma, or the known pre-antibiotic-era outcomes of untreated Pneumococcus?  Also, NEVER give azithromycin if there’s a chance of bacteremia, because the drug penetrates tissue but won’t treat the bloodstream.

What about patients with defined risks of drug-resistant Pneumococcus (see above)?  Rates commonly run 20% to beta-lactams, >30% to TMP-SMX and Macrolides.  For respiratory fluoroquinolones (levofloxacin, NOT ciprofloxacin or ofloxacin) they’re near 1%.  But the more we use them, the worse it’ll be.  One 2003 study found a third of ER patients treated with levofloxacin, half inappropriately.  Here we go again.  I save it for the elderly & those with multiple co-morbidities.

There’s also the new macrolide Telithromycin (Ketek®), with virtually no resistance to it.  But some patients have died of hepatotoxicity.  So it’s definitely 2nd-line (and only for pneumonia; never otitis or sinusitis).

I shouldn’t say this [purely anecdotal], but lots of clinicians in the San Francisco public sector (including me) use Doxycycline first-line for CAP.  For better or worse, it’s rarely included in studies.

Re: contact with kids in day-care, which I personally crossed off under risks for drug-resistant Pneumococcus.  It’s in the latest USA guidelines (presented 2006, published 2007, based on earlier studies).  But the Pediatric 2011 recommendations go with amoxicillin, & don’t even mention day-care.  That’s because routine use of Conjugate Vaccine (7-Valent, now 13-) has greatly reduced pediatric pneumococcal disease.  Of course, new serotypes will emerge (followed by new vaccines), but haven’t yet.  So if Peds gives Amoxicillin to all kids, we can certainly use it for adults in contact with them.

Last posting we noted the 2012 IDSA Guidelines for Sinusitis recommend Amoxicillin (perhaps with clavulanate) because of drug-resistant Pneumococcus.  They also recommend NOT to use macrolides or TMP-SMX.  Shouldn’t that also impact on recommendations for pneumonia?

And that’s it for Bugs & Drugs and the Lung.  See also our prior posts on Infectious Disease: Skin & Soft Tissue, Head & Neck, and organs Below the Diaphragm (UTIs, PID, & diverticulitis).

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