Antibiotics do not help with severity or duration but may decrease infectivity.
A reasonable guideline is to treat persons aged >1 year within 3 weeks of cough onset and infants aged <1 year and pregnant women (especially near term) within 6 weeks of cough onset. 
TMP--SMZ should not be administered to pregnant women, nursing mothers, or infants aged <2 months.
The following regemins are for active disease or postexposure prophylaxis.  If a patient is has confirmed disease and is likely to be in contact with infants or pregnant women then the patient should be treated as up to 6-8 weeks after the onset of their illness.
Same antibiotics for active disease and postexposure prophylaxis
Azithromycin 10mg/kg (max 500mg/day) daily x 5 days
Azithromycin 10mg/kg (max 500mg/day) daily x 5 days
if > 6 months old then day 2-5 of treatment should be reduced to 5mg/kg (250mg/day max)
TMP/SMX 4mg/kg PO BID daily for 14 days (if > 2 months old)
if > 6 months old then day 2-5 of treatment should be reduced to 5mg/kg (250mg/day max)
any of the following antibiotics are acceptable although azithromycin is most commonly prescribed
Azithromycin 500mg PO once daily for day #1 then 250mg PO once daily for days #2-5
Clarithromycin 500mg BID x7 days
Erythromycin 500mg QID x7 days
Pulmonary antibiotics
Thoracic lavage
Thoracentesis
Thoracotomy
Thoracotomy 
Needle thoracostomy
Lung recruitment maneuver
ENT antibiotics