Urinary Tract Infections Sulfamethoxazole and Trimethoprim Injection is indicated in the treatment of severe or complicated urinary tract infections in adults and pediatric patients two months of age and older due to susceptible strains of Escherichia coli, Klebsiella species, Enterobacter species, Morganella morganii, Proteus mirabilis and Proteus vulgaris when oral administration of Sulfamethoxazole and Trimethoprim Injection is not feasible and when the organism is not susceptible to single-agent antibacterials effective in the urinary tract. To reduce the development of drug-resistant bacteria and maintain the effectiveness of Sulfamethoxazole and Trimethoprim Injection and other antibacterial drugs, Sulfamethoxazole and Trimethoprim Injection should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to empiric selection of therapy. Although appropriate culture and susceptibility studies should be performed, therapy may be started while awaiting the results of these studies. Shigellosis Sulfamethoxazole and Trimethoprim Injection is indicated in the treatment of enteritis caused by susceptible strains of Shigella flexneri and Shigella sonnei in adults and pediatric patients two months of age and older. Sulfamethoxazole and Trimethoprim Injection is a combination of sulfamethoxazole, a sulfonamide antimicrobial, and trimethoprim, a dihydrofolate reductase inhibitor antibacterial, indicated in adults and pediatric patients two months of age and older for treatment of infections caused by designated, susceptible bacteria. Pneumocystis jirovecii Pneumonia. Pneumocystis jirovecii Pneumonia Sulfamethoxazole and Trimethoprim Injection is indicated in the treatment of Pneumocystis jirovecii pneumonia in adults and pediatric patients two months of age and older.