Comparison of Mono and Biphasic Culture Media in Isolating Bacteria from Blood and evaluation Bu-Ali Hospital Lab Quality

Blood Culture is an important diagnostic method in infectious diseases and has positive results in 30%- 50% and even to 80% of cases due to sample volume. In Bu-Ali Hospital, Tehran, it decreases to 2-3%. In this survey, quality of hospital lab and difference between Mono and Biphasic culture media in isolating bacteria from blood of patients suggestive of sepsis were evaluated.106 (48 F + 58 M) newly admitted patients with impression of sepsis as SIRS (Systemic Inflammatory Response Syndrome) (36˚C >OT>38.3˚C, tachycardia more than 100/min, leukocytosis with shift to left or leucopenia) with infectious source were sampled for culture (5ml blood 3 times in 1 Biphasic and 2 Monophasic media) in the infectious ward. One Monophasic Media in hospital lab and the two other (1 Monophasic + 1 Biphasic Media) in Reference Laboratory of Iran, Research Center were handled. Media were quality-controlled at beginning and in the middle of study by NCCLS (National Committee for Clinical Lab Standard) with ATCC (American Type Culture Collection) samples. Sampling, transfer, and handling were all in standard conditions usually used in hospital. Results were compared by Fisher Exact Test. Clinical diagnosis were bacterial in 84 (79%), and nonbacterial in 22 (21%) patients at admission. 57 (54%) patients had not used antibiotics in the past 72 hours. In Monophasic Media of hospital lab 2 (1.9%) positive cultures (S. epidermidis) one with history of Erythromycin use were reported. In both Monophasic and Biphasic Media in reference lab 3 (2.8%) positive cultures (2 S.epidermidis, 1 E. coli) were reported equally, one with history of Erythromycin use. Growth Index in both Monophasic and Biphasic Media were standard in quality control. Qualities of Mono and Biphasic Media in growing bacteria were alike and Biphasic Media had no superiority to Monophasic Media in routine bacterial isolation. Positive culture in both labs had no significant statistical difference. So, negative results are not due to media and laboratorial fields, and it is needed to educate and evaluate two other fields: Sampling and Transferring. Also, we may have more positive cultures by increasing blood samples from 5 to 20 ml which can be compared in next studies.