There are several different types of bacteria that can cause urinary tract infections, or UTIs. The species Staphylococcus saprophyticus is a common cause in young women, according to "Harrison's Principles of Internal Medicine." Although it is in the same genus as Staphylococcus aureus, the species that causes antibiotic-resistance staph infections, Staphylococcus saprophyticus has yet to develop significant resistance to any of the antibiotics in common use. Therefore, almost any antibiotic is effective against a staph-related UTI, though the best antibiotics are those that concentrate in the urine.
Bactrim
Bactrim, the trade name for a combination of the sulfa drugs sulfamethoxazole and trimethoprim, is an antibiotic commonly used for UTIs. It is highly effective for that purpose because the two drugs concentrate in the urine and together they are much more effective than either is separately, according to "Principles of Pharmacology." It is also inexpensive and available in either single or double strength tablets. Bactrim treatment for uncomplicated UTIs typically lasts for three days, although in some circumstances a seven-day course is used.
Fluoroquinolones
Antibiotics from the fluoroquinolone class, which includes drugs such as ciprofloxacin, or Cipro, and lexofloxacin, or Levaquin, are also commonly used to treat UTIs. They are effective against many bacteria, including Staph saprophyticus, and like Bactrim, are concentrated in the urine, according to "Principles of Pharmacology." If fluoroquinolones are over used, their broad spectrum of activity can lead to antibiotic resistance in intestinal bacteria, which can potentially cause a severe form of diarrhea. Because of this, they are most commonly used as an alternative drug for treating UTIs in patients with allergies to sulfa drugs. Like Bactrim, fuoroquinolone treatment for uncomplicated UTIs usually lasts for three days, with seven days being indicated in some cases.
Amoxicillin
Amoxicillin is another antibiotic that concentrates in the urine, making it useful for treating UTIs, according to "Principles of Pharmacology." Amoxicillin is most commonly used for complicated UTIs, such as those occurring in diabetic patients or those infections that have lasted for more than seven days. It can be used either orally or intravenously, which means that treatment can begin with oral administration and then move to IV if necessary. Because amoxicillin is mostly used for more complicated UTIs, the typical course of treatment lasts for seven days rather than three. Amoxicillin is in the same class of antibiotics as penicillin, and sometimes patients who are allergic to penicillin have a cross-allergy to amoxicillin.
References
- "Harrison's Principles of Internal Medicine" 16th edition; Dennis L. Kasper, et al., ed.; 2005
- "Principles of Pharmacology"; David E. Golan, et. al., eds.; 2005
