Improving bacterial smear detection with Wright-Giemsa staining: A multicenter study in clinical microbiology laboratories

Improvement in bacterial detection in smear is needed because pathogens in smears and positive blood cultures (PBCs) can be missed by microscopy if Gram staining is used. This study assessed the efficacy of Wright-Giemsa staining in remedying bacterial detection failures. We conducted a prospective multicenter study involving 5667 sputum specimens and 5502 PBCs collected from five distinct centers. When initial Gram staining did not identify bacteria, Wright-Giemsa staining was performed. The study also analyzed cases of missed detections and the undetected microorganism types. Among the sputum specimens, 3.0 % (170 cases) that were negative for Gram staining were successfully identified using Wright-Giemsa staining, revealing 321 previously undetected microbial forms. Of the PBCs, 5.1 % (283 cases) exhibited no microorganisms upon initial Gram staining, and subsequent Wright-Giemsa staining identified bacteria in 119 PBCs (42.0 % of the 283 cases). Culture identification further confirmed the bacterial presence in 77 PBCs (64.7 % of the 119 cases). The predominant contaminants were coagulase-negative staphylococci, Micrococcus spp., Corynebacterium spp., and alpha-hemolytic streptococci, which accounted for 64.9 % of the total isolates. For both specimens, the missed detection rate in primary hospitals was significantly higher than in regional central hospitals (p < 0.001). Incorporating Wright-Giemsa staining can substantially decrease the missed detection rate in bacterial smears, potentially harmonizing inter-laboratory discrepancies. For Gram-staining-negative sputum specimens or PBCs, Wright-Giemsa staining may enhances detection in microbiology laboratories, particularly in primary hospitals with limited specimens or diagnostic experience.