The aim of this study was to investigate the in vitro activities of polymyxin B (PB) and rifampin (RIF) in combination with ampicillin/sulbactam (AS) or cefoperazone/sulbactam (CS) against 20 multidrug-resistant Acinetobacter baumannii (MDR-AB) isolates by the checkerboard and E-test methods. Fractional inhibitory concentration index (FICI) values were defined as synergy, FICI ≤ 0.5; additivity, 0.5 < FICI ≤ 1.0, indifference, 1.0 < FICI < 4.0; and antagonism, FICI ≥ 4. Synergistic interaction was detected only for the RIF + AS and RIF + CS combinations. While the most frequently detected interaction type for PB + AS or PB + CS combinations was indifference, some showed antagonistic interactions. The detection rate of synergy was significantly higher by the checkerboard than by the E-test method, and the detection rate of indifference was significantly higher by the E-test than by the checkerboard method for RIF + AS combination (P ≤ 0.0001). In addition, no statistically significant difference was detected between the checkerboard and E-test methods for the detection rates of interaction types for any of the other combinations (P > 0.05), except for PB + CS combination for the detection of additivity (P = 0.018). Owing to the high percentage of synergistic interactions between RIF and AS, we considered this combination as an effective therapeutic option for MDR-AB infections.

Objectives: Sterile body fluids (BFs) include key information for the diagnosis and monitoring of a variety of diseases. A cornerstone test is the total white blood cell (WBC) count, which comprises the differential of WBC of body fluid analysis. It is important to test automated hematology analyzers that should be verified using patient samples. The aim of this study is to compare both the performance of the Sysmex XN-1000 system’s body fluid module for cell counting and differentiation to the results of a cell counting chamber. Methods: This study was performed on 200 routinely laboratory sent BFs. Cell counts and differentiation were determined with both bright-lined Neubauer Cell Counting Chamber and Sysmex XN-1000 system body fluid mode. Results: The correlation coefficients of WBC count by two methods indicated very strong correlation (r≥0.90, p<0.0001) for any specimen except pleural fluid. According to Passing-Bablok regression analysis, Sysmex XN-1000 showed acceptable performance according to bias of the slope criteria (<±20%). Conclusions: The XN-1000 hematological analyzer’s body fluid mode can rapidly count and identify cells, and it can be used as a simple and rapid screening method for laboratory testing of sterile body fluids, particularly in laboratories with a massive quantity of biological fluids.