QMAC-dRAST for the direct testing of antibiotic susceptibility for Enterobacterales in positive blood-culture broth: a comparison of the performances with the MicroScan system and direct disc diffusion testing methods.

OBJECTIVES: To evaluate the performances of the QMAC-dRAST GN (Gram-negative) kit for rapid antimicrobial sensitivity testing (AST) and two other methods, directly on positive blood-culture broth (PBCB), by comparison with a reference method: the MicroScan method based on broth microdilution on colonies isolated on PBCB subculture. METHODS: In total, 156 samples were collected prospectively from blood cultures positive for a Gram-negative rod. Each sample was tested with four AST techniques: (i) the QMAC dRAST GN kit, (ii) the disc diffusion (DD) method, (iii) the MicroScan method applied directly to PBCB; and (iv) MicroScan with isolates from PBCB subculture, as a reference. RESULTS: For 124 PBCB containing Enterobacterales, overall essential agreement (EA) and categorical agreement (CA) between the QMAC-dRAST on PBCB and the reference reached 95.7% and 93.5%, respectively. There were 3.0% very major errors (VME), 4.0% major errors (ME) and 2.8% minor errors (mE). A comparison of MicroScan on PBCB and the reference yielded 98.8% EA, 98.5% CA, and rates of 0.6% VME, 0.9% ME and 0.7% mE. The DD method on PBCB gave a CA of 95.8% and rates of 1.7% for VME, 2.0% for ME and 1.9% for mE. Results were obtained more rapidly for QMAC-dRAST (median of 6 h 37 min versus 18 h for the MicroScan and DD methods on PBCB). CONCLUSIONS: The QMAC-dRAST system provided rapid results well correlated with the reference method on PBCB containing Enterobacterales. Given the shorter time-to-results, the QMAC-dRAST system constitutes a fast and reliable alternative to conventional AST methods.

Tuberculosis in sickle cell disease patients.

OBJECTIVE: Tuberculosis (TB) disease has rarely been reported in patients with sickle cell disease, but it is associated with an increased risk of bacterial infections. In France, sickle cell disease is frequent in populations with the highest prevalence of TB disease. We aimed to highlight clinical aspects of TB disease in patients with sickle cell disease. PATIENTS AND METHODS: Over a 10-year period, we retrospectively included all adults with sickle cell disease who had a positive culture for Mycobacterium tuberculosis managed in the adult sickle cell center of Henri-Mondor hospital. Sickle cell patients with TB disease were matched for comparison to adults without hemoglobinopathy and with documented TB disease in a 1:2 ratio. Logistic regression mixed models were performed. RESULTS: Twelve patients with sickle cell disease and documented TB disease (median age: 29years; IQR [25-34]) were compared to 24 non-sickle cell patients (median age: 33years; IQR [27.5-38.5]). Baseline characteristics were similar between groups except for sickle cell disease. Ten of the 12 patients with sickle cell disease had pulmonary TB. TB disease characteristics were similar between sickle cell and non-sickle cell patients although sickle cell patients had fewer positive sputum smears for acid-fast bacilli (P=0.003) and fewer lung cavitations (P=0.03). CONCLUSIONS: TB disease in sickle cell patients was globally similar to non-sickle cell patients, even though less infectious. Regular follow-up in specialized centers might allow for earlier TB disease diagnosis in sickle cell patients.