63. Nobbling the Nonfermentors: Stenotrophomonas maltophilia

*Stenotrophomonas maltophilia* is an opportunistic, multidrug-resistant, non-fermenting gram-negative pathogen frequently encountered in intensive care units and immunocompromised populations. It possesses intrinsic resistance to most beta-lactams and aminoglycosides due to chromosomal L1 and L2 beta-lactamases and robust efflux pump systems. Clinical management is complicated by a lack of standardized susceptibility breakpoints and the unreliability of automated testing systems, often necessitating reliance on historical data or broth microdilution. First-line treatment typically involves high-dose cotrimoxazole, often combined with agents like minocycline, levofloxacin, or ceftazidime-avibactam plus aztreonam. Because the organism frequently colonizes patients with chronic respiratory conditions or those exposed to carbapenem pressure, clinicians must distinguish between colonization and true infection, particularly in polymicrobial scenarios where *Stenotrophomonas* may act as a biofilm-promoting partner to *Pseudomonas aeruginosa*.