title: Using color histograms and SPA-LDA to classify bacteria.
abstract: In this work, a new approach is proposed to verify the differentiating characteristics of five bacteria (Escherichia coli, Enterococcus faecalis, Streptococcus salivarius, Streptococcus oralis, and Staphylococcus aureus) by using digital images obtained with a simple webcam and variable selection by the Successive Projections Algorithm associated with Linear Discriminant Analysis (SPA-LDA). In this sense, color histograms in the red-green-blue (RGB), hue-saturation-value (HSV), and grayscale channels and their combinations were used as input data, and statistically evaluated by using different multivariate classifiers (Soft Independent Modeling by Class Analogy (SIMCA), Principal Component Analysis-Linear Discriminant Analysis (PCA-LDA), Partial Least Squares Discriminant Analysis (PLS-DA) and Successive Projections Algorithm-Linear Discriminant Analysis (SPA-LDA)). The bacteria strains were cultivated in a nutritive blood agar base layer for 24 h by following the Brazilian Pharmacopoeia, maintaining the status of cell growth and the nature of nutrient solutions under the same conditions. The best result in classification was obtained by using RGB and SPA-LDA, which reached 94 and 100 % of classification accuracy in the training and test sets, respectively. This result is extremely positive from the viewpoint of routine clinical analyses, because it avoids bacterial identification based on phenotypic identification of the causative organism using Gram staining, culture, and biochemical proofs. Therefore, the proposed method presents inherent advantages, promoting a simpler, faster, and low-cost alternative for bacterial identification.
authors.affiliation: Centro de Ciência e Tecnologia, Laboratório de Química Analítica e Quimiometria (LQAQ), Universidade Estadual da Paraíba, CEP 58.429-500, Campina Grande, Paraíba, Brazil.
authors.forename: Valber Elias
authors.initials: VE
authors.lastname: de Almeida
authors.forename: Gean Bezerra
authors.initials: GB
authors.lastname: da Costa
authors.forename: David Douglas
authors.initials: DD
authors.lastname: de Sousa Fernandes
authors.forename: Paulo Henrique
authors.initials: PH
authors.lastname: Gonçalves Dias Diniz
authors.forename: Deysiane
authors.initials: D
authors.lastname: Brandão
authors.forename: Ana Claudia Dantas
authors.initials: AC
authors.lastname: de Medeiros
authors.forename: Germano
authors.initials: G
authors.lastname: Véras
mesh_terms: D001419:Bacteria / Q000737:chemistry* / Q000145:classification* / Q000302:isolation & purification; D015373:Bacterial Typing Techniques / Q000295:instrumentation / Q000379:methods*; D016002:Discriminant Analysis; D016018:Least-Squares Analysis; D010781:Photography / Q000295:instrumentation / Q000379:methods*