Doctors usually prescribe broad-spectrum antibiotics to treat a range of bacterial infections. Narrow-spectrum antibiotics are effective only against certain types of bacteria. Some of onlinerxantibiotics.com antibiotics work against anaerobic bacteria, while others attack aerobic bacteria. Sometimes, doctors recommend these meds to prevent certain infections. Some of the most common bacterial infections treated by antibiotics include: Bronchitis; Acne; Traveler’s diarrhea; Conjunctivitis; Urinary tract infections; Skin or soft tissue infections; Otitis media; Upper respiratory tract infections; Sexually transmitted diseases; Streptococcal pharyngitis. How to Use Antibiotics Correctly In most cases, patients take antibiotics orally, but these drugs can be administered with injections or applied topically. Some antibiotics should be taken with meals, while others must be taken on an empty stomach. Most antibiotics start fighting infections within several hours.