Improved micropropagation of Bacopa monnieri (L.) Wettst. (Plantaginaceae) and antimicrobial activity of in vitro and ex vitro raised plants against multidrug-resistant clinical isolates of urinary tract infecting (UTI) and respiratory tract infecting (RTI) bacteria

Abstract Background Nowadays the multidrug-resistant (MDR) bacterial pathogens are a major concern of the medical science. Medicinal plants may be considered as new sources for producing antibacterial agents. The present study aimed to standardize an improved method for micropropagation and in vitro biomass production of Bacopa monnieri. Second aim is to evaluate the antimicrobial potency of in vitro cultured and ex vitro field grown micropropagated plants against different MDR clinical isolates of human urinary tract infecting (UTI) and respiratory tract infecting (RTI) pathogens. Methods Micropropagation of B. monnieri were performed following standard tissue culture method. The role of 6-benzylaminopurine (BAP), kinetin and spermidine on multiple shoot induction were evaluated. Antimicrobial activity of ethanol, methanol and acetone extract of in vitro and ex vitro plants of B. monnieri were screened by agar cup method against five MDR-UTI bacteria, four MDR-RTI bacteria and three microbial type culture collection (MTCC) bacteria and two fungi. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and minimum fungicidal concentration (MFC) were also determined. Results Synergistic effect of BAP and spermidine had improved shoot induction with a maximum of 123.8 shoot-buds per explant. Optimum micropropagation with 34.9 elongated shoots per explant was recorded in Murashige and Skoog medium containing 1.5 mg/L BAP and 2.0 mM spermidine. Methanolic extract of ex vitro plants showed maximum activity against MDR-UTI strain of Escherichia coli (sample-9) [ZI 18 ± 0.68 mm, MIC 2.5 μg/mL, MBC 5.0 μg/mL]. Acetone extract of ex vitro plant exhibited maximum inhibition against MDR-RTI strain of Klebsiella pneumoniae (sample-38) [ZI 14 ± 0.22 mm, MIC 5.0 μg/mL, MBC 7.5 μg/mL]. The extracts of B. monnieri were bactericidal rather than bacteriostatic against all UTI and RTI bacteria tested. Conclusions The present manuscript demonstrated an efficient in vitro method for large scale biomass production of B. monnieri. Furthermore, the methanolic extract of B. monnieri have potential antimicrobial activity against clinical isolates of MDR-UTI and MDR-RTI bacterial strains. Hence this plant may further use to treat these infectious diseases. The comparative results show ex vitro grown plants have slightly better antimicrobial activities as compared to the in vitro plants