A sputum culture from a cystic fibrosis patient grew Stenotrophomonas maltophila.A broth microdilution panel was inoculated.Antimicrobials tested included: ceftazidime,imipenem,ticarcillin-clavulanate,levofloxacin,and trimethoprim-sulfamethoxazole.After 20-hour incubation at 35°C in ambient air,no growth was seen in any well of the microtiter plate.Which of the following statements is true?
A)The isolate is susceptible to all antimicrobials tested.
B)The microdilution plate was incubated under incorrect conditions.
C)The test results are invalid and retesting would be recommended.
D)A Cefinase test for β-lactamase activity should be done as an adjunct to MIC results.

Question

Quizplus · Accepted Answer

Since there was no growth in the positive (i.e. ,growth control well)the test is invalid and would indicate that the organism did not grow or was not inoculated.The test is invalid and must be repeated.Furthermore,this organism is known to be highly resistant to many antimicrobials and have intrinsic resistance to imipenem.

A Sputum Culture from a Cystic Fibrosis Patient Grew Stenotrophomonas