A recent request for scripts for FAK ABX (antibiotics) caused me to review the topic. Here are my thoughts, comments welcome. This a from a US (Midwestern) standpoint – some variability due to location would be expected. This is for use when formal medical care would be > 48 hours away. Use is assumed to be otherwise healthy adults.
Disclaimer: this is meant to be a topical review of the subject and not to be construed as medical advice.

Diseases:

Community acquired pneumonia (CAP):
The most commonly identified pathogens are Streptococcus pneumoniae (accounts for 66% of fatal cases), Haemophilus influenzae, and atypical organisms (ie, Chlamydia pneumoniae, Mycoplasma pneumoniae, Legionella sp).
Empiric treatment:
Macrolide (azithromycin 500 mg PO once, then 250 mg once/day; clarithromycin 250to 500 mg PO bid; or extended-release clarithromycin 1 g once/day) or
Doxycycline 100 mg PO bid (if allergic to macrolide) or
Antipneumococcal fluoroquinolone‡(levofloxacin ) PO.
http://www.merck.com/mmpe/sec05/ch052/ch052b.html#CIHHGHHH
BUT 25%+ (and increasing)isolates of S. pneumoniae are resistant to macrolides.


Acute Sinusitis:
Common pathogens are Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis .
Empiric therapy:
A synthetic penicillin is used-most commonly amoxicillin (such as Amoxil, Polymox, Trimox). People allergic to penicillin can take a sulfur-containing antibiotic called trimethoprim/sulfamethoxazole or TMP/SMX (such as Bactrim, Cotrim, Septra).
http://www.webmd.com/a-to-z-guides/sinus-infection


Skin and superficial wound infections:
Most common bacterial infection are due to Staphylococcus aureus and Streptococcus pyogenes.
Empiric treatment:
cephalexin:250 mg orally every 6 hours or 500 mg orally every 12 hours
http://www.clevelandclinicmeded.com/medi...kin-infections/
http://www.drugs.com/cephalexin.html


Skin fungal infections:
Three fungal genera—Trichophyton, Microsporum, and Epidermophyton—account for the vast majority of infections
Empiric treatment:
topical treatment with terbinafine (Lamisil), clotrimazole (Lotrimin, Mycelex), or econazole (Spectazole) cream is adequate when applied twice daily for 6 to 8 weeks.
http://www.clevelandclinicmeded.com/medi...kin-infections/


Tick Borne Rickettsial Disease (TBRD)
Most common infection (US) are due to Ehrlichial and Rickettsia species
Empiric treatment:
Appropriate antibiotic treatment should be initiated immediately when there is a suspicion of a tick borne rickettsial disease (TBRD) on the basis of clinical and epidemiologic findings. Treatment should not be delayed until laboratory confirmation is obtained.
Doxycycline is the drug of choice for treatment of all TBRD in children and adults. The recommended dose is 100 mg per dose administered twice daily (orally or intravenously) for adults or 2.2 mg/kg body weight per dose administered twice daily (orally or intravenously) for children weighing < 100 lbs. (45.4 kg).
http://www.cdc.gov/ticks/index.html

Travelers diarrhea:
The most common causative agent isolated in countries surveyed has been enterotoxigenic Escherichia coli (ETEC). ETEC produce watery diarrhea with associated cramps and low-grade or no fever. Besides ETEC and other bacterial pathogens, a variety of viral and parasitic enteric pathogens also are potential causative agents.
Empiric treatment:
Prophylaxis: bismuth subsalicylate taken as either 2 tablets 4 times daily or 2 fluid ounces 4 times daily reduces the incidence of travelers' diarrhea.
ABX:fluoroquinolones are the drugs of choice. Commonly prescribed regimens are 500 mg of ciprofloxacin twice a day or 400 mg of norfloxacin twice a day for 3-5 days. Trimethoprim-sulfamethoxazole and doxycycline are no longer recommended because of the high level of resistance to these agents. Bismuth subsalicylate also may be used as treatment: 1 fluid ounce or 2 262 mg tablets every 30 minutes for up to eight doses in a 24-hour period, which can be repeated on a second day. If diarrhea persists despite therapy, travelers should be evaluated by a doctor and treated for possible parasitic infection.
http://www.cdc.gov/NCIDOD/DBMD/DISEASEINFO/travelersdiarrhea_g.htm


UTI (urinary tract infection):
Is usually caused by Escherichia coli (E. coli).
Empiric treatment:
Amoxicillin (Amoxil, Trimox), Ciprofloxacin (Cipro), Levofloxacin (Levaquin), Sulfamethoxazole-trimethoprim (Bactrim), or doxycycline for 3 to 10 days.
http://www.mayoclinic.com/health/urinary-tract-infection/DS00286



SOOO:
Amoxicillin will cover Sinusitis, UTI
Cephalexin will cover Skin infections , UTI Upper respiratory infections (not drug of choice)
Doxycycline will cover CAP, TBRD, UTI
Levofloxacin will cover CAP, travelers diarrhea, UTI
Marcolides provide decreasing coverage for CAP


Doxycyline and levofloxacin would cover the broadest range with 2 agents with consideration to addition of cephalexin and maybe amoxicillin for the broadest coverge overall.