Gram Staining: a Comparison of Two Automated Systems and Manual Staining

Abstract

Various Gram staining automated systems are available to accelerate and standardize the staining process but a systematic comparison of different systems is largely lacking. The objective of this study was to evaluate two devices in comparison to manual Gram staining. Clinical samples (n=500, University Hospital Münster, Germany, May-June 2020) were simultaneously Gram stained manually and with two automated Gram strainers (PREVI® Color Gram, bioMérieux and ColorAX2, Axonlab). The quality was assessed based on four criteria: (i) homogeneous staining of bacteria/fungi, (ii) uniform staining of the background, (iii) absence of staining artifacts and (iv) congruency between culture and microscopy. Each criterion was rated with “0” (absence) or “1” (presence) point to calculate a quality score (0–4 points). The costs for each staining procedure were calculated based on consumables and hands-on time (applying the average wage of a laboratory technician in the public service for Germany and the US). The mean (±SD) quality scores were comparable for manual staining (3.06±0.91) and PREVI® Color Gram (3.04±0.90, p=0.6) while significantly lower scores were achieved by ColorAX2 (2.57±1.09, p<0.0001). The total cost per Gram staining was 1.13 €/1.34 $ (PREVI® Color Gram), 0.80 €/0.83 $ (manual) and 0.60 €/0.71 $ (ColorAX2), respectively. The quality and costs per slide vary significantly between instruments of different manufacturers.

Identification, characteristics and rice growth promotion of a highly efficient cellulolytic bacterial strain, Cellulomonas iranensis ZJW-6, isolated from paddy soil in central China

“…The morphology of the bacterium ZJW-6 cultured on an LB solid plate was investigated, and Gram-staining was performed as described by Froböse et al (2020) . Cellulomonas iranensis ZJW-6 was Gram-positive and grew as a tiny, yellowish-green colony on agar, which was consistent with the Cellulomonas iranensis ’ description by Elberson et al (2000a) .…”

Antibiotic sensitivity test of Escherichia coli and Staphylococcus aureus isolated from the reproductive tract of dairy cows

“…Gram staining of the 15 samples showed all colony samples in the form of short rods (coccobacilli) and were classified as Gramnegative bacteria indicated by pink cell colour. E. coli bacteria could not maintain violet crystal dyes during the Gram staining process due to the structure of the cell wall (Froböse et al, 2020). Gram-negative bacterial cell walls did not contain teichoic acid and because they contained only a small amount of peptidoglycans, therefore, the Gram-negative bacteria cell walls were more susceptible to mechanical damage (Sudrajad et al, 2018).…”

Comparison of an automated DNA extraction and 16S rDNA real time PCR/sequencing diagnostic method using optimized reagents with culture during a 15-month study using specimens from sterile body sites

“…Generally, microscopy was not performed for all implant-associated infections based on the specifications of a review [ 16 ]. For other clinical specimens, classical Gram staining of original clinical specimens was performed manually with commercial reagents (Biomerieux, Switzerland) [ 17 ]. Cultures were identified with MALDI-TOF [ 18 ].…”