In clinical microbiology laboratories, blood cultures are important to find out the pathogens causing bacteremia or fungemia [1]. The blood culture using automated blood culture systems with continuous monitoring method provides results within five days. Ruiz-Giardin et al. [2] stated that the median time of growth detection was 12.72 hours in the bacteremia patients. However, Qian et al. [3] reported that the time to positivity was significantly shorter in false-positive cases, mostly less than a day (< 24 hours) than in truepositive bacteremia cases, all more than a day (> 24 hours). In our study, two cases both showed positive signals in less than 6 hours. There is a slight time difference between two studies with ours, but it should be aware that the earlier signal more chance of being false signal. Therefore, distinguishing between true and false bacteremia is crucial for early treatment after right microorganism identification in a patient with sepsis. Blood cultures detected as positive by the automated blood culture system but no bacteria in Gram stain by microscopy and no growth on subculture are considered as false-positive. Hyperleukocytosis or the presence of fastidious bacteria have been considered frequent causes of false-positives, but unexplained cases remain to be explored [4–6]. Ziegler et al. [7] found out that false-positive rates of blood cultures using blood culture systems were between 1.4% and 6.2%. BacT/Alert Virtuo (bioMérieux) system based on colorimetric detection by pH sensors of produced CO₂ by growing microorganisms. Positive signals appeared in automated blood culture systems due to hyperleukocytosis may contribute to false-positive culture results as the metabolism of leukocytes also could generate CO₂ and resulted in increases of CO₂ [7]. Direct identification of culture positive bottles by molecular methods is applicable and could be considered to differentiate the true and false positives. However, it needs extra work and expense in routine microbiology laboratories [3]. Therefore, most laboratories do not use additional molecular tests for identification as in our laboratory. We considered the first case the very first experience in the clinical microbiology laboratory of our hospital. Still we might have missed the cases and were unaware of the abnormal findings. Therefore, we recommend specific procedures to deal with the suspicion of false-positive cases. Using an automated blood culture system, we often find no bacteria in Gram stain by microscopy when positive signal flagged bottles were processed. First, we recommend checking the reading graph to see whether a peak appeared within a few hours of incubation. If a peak was observed, secondly, the laboratory test results should be reviewed for leukocytosis (neutrophilia) and the presence of other signs to consider true bacteremia. Third, additional blood culture incubation should be sustained until five days with subculture on the agar under CO₂ to enhance the growth of fastidious bacteria. Finally, Gram stain examination on the blood culture media and subculture on an agar plate is recommended to exclude the false negative.