Question #22 explained
Which of the following organisms is sulfamethoxazole-trimethoprim (Bactrim, Septra) active against?
A. E. coli – CORRECT: SMX/TMP is widely used for urinary tract infection caused by E. coli, but beware increasing prevalence of resistance
B. Stenotrophomonas maltophilia – CORRECT: this organism can be resistant to SMX/TMP, but this drug is widely considered first-line against the non-fermenting Gram negative rod S. maltophilia
C. Nocardia spp. – CORRECT: there are many species of Nocardia and resistance patterns vary by species, however SMX/TMP is widely considered a first-line drug for these organisms
D. Methicillin-resistant Staphylococcus aureus (MRSA) – CORRECT: community-acquired MRSA is usually susceptible to SMX/TMP and clindamycin too, but beware resistance to SMX/TMP and clindamycin in healthcare-associated MRSA
E. Mycobacterium avid complex (MAC) – INCORRECT: while SMX/TMP is a go-to option for opportunistic infections caused by PCP and toxoplasma, it is not effective for MAC. Preferred therapy for MAC treatment is azithromycin or clarithromycin plus ethambutol.