  The plants, Althaea officinalis, Tilia cordata and Psidium guaja have been
used traditionally to treat respiratory infection symptoms. Flowers of A.
officinalis and leaves of T. cordata and P. guaja have been used to treat
cough, sore throat, catarrh, oral and pharyngeal mucosa irritation. Therefore,
this study was designed to examine the antibacterial and antibiofilm effects of
these plants individually as well as in combination, as a formula against
respiratory infections causing pathogens. The tested pathogens were Extended
Spectrum Beta-Lactamase producing Escherichia coli (ESBL), Beta-Lactamase
producing Escherichia coli (BL), Beta-Lactamase producing Klebsiella pneumoniae
(BL), Beta-Lactamase producing Pseudomonas aeruginosa (BL), Enterobacter
cloacae, and Beta-Lactamase producing Staphylococcus aureus (BL). The tested
plants were extracted using ethanol and then fractionated using different
polarity solvents (hexane, ethyl acetate and water). Disc diffusion and
microdilution (Minimum Inhibitory Concentration) methods were used to evaluate
the antibacterial activity while the antibiofilm activity was tested using
crystal violet assay. The results showed that A. officinalis and T. cordata
extracts and fractions exhibited weak antibacterial activity having MIC values
ranged from 6.25 to 12.5 mg/mL. P. guaja exhibited moderate antibacterial
activity with MIC values ranged from 6.25 to 1.56 mg/mL. Combination between
these plants extracts and fractions in equal proportion provides stronger
antibacterial (with MIC values ranged from 6.25 to 0.8 mg/mL) and antibiofilm
activities (MBIC50 was 0.2 mg/mL). Therefore, this study provides a valuable
scientific knowledge to support the use of plants in combination rather than
individually.
