Microbiology -- A 68 Year Old Man with Fevers


Tissue obtained from the CT-guided biopsy of the pleural based right lower lobe mass grew moderate amounts of gram-positive coccobacillary organisms (Image 13). The colonies were rather small, white and slightly mucoid with slight beta-hemolysis after 24 hours of aerobic growth on 5% sheep blood agar (Image 14). Biochemically, the organism was capable of hydrolyzing urea (Image 15) but unable to hydrolyze casein, tyrosine, or xanthine (Image 16). While the colonies remained white and mucoid on continued cultivation on 5% sheep blood agar , a distinctive pink-salmon coloration was noted on the casein/tyrosine/xanthine plate (Image 16). The organism was subcultured to tap water agar where rudimentary branching of its substrate hyphae without aerial hyphae was observed (Image 17). Cross-streaking the organism with Staphylococcus aureus resulted in the accentuation of the beta-hemolysin zone (Image 18). Subsequent blood and bronchoalveolar fluid cultures grew the same organism.


Antimicrobial sensitivity testing (performed by Richard J. Wallace Jr. at the mycobacterial/nocardia research laboratory at the University of Texas Health Center) yielded the following results:

Amikacin     X
Ampicillin     X
Augmentin   X  
Cefmetazole X    
Cefotaxime   X  
Cefoxitin X    
Ceftizoxime   X  
Ceftriaxone X    
Ciprofloxacin X    
Clarithromycin X    
Doxycycline   X  
Gentamicin   X  
Imipenem X    
Kanamycin     X
Minocycline X    
Ofloxacin     X
Sulfisoxazole X    
Tobramycin X    
Trimethoprim Sulfamethoxazole X    
Vancomycin X    



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