[In vitro study to evaluate the antibacterial activity of a combination of the haulm of nasturtium (Tropaeoli majoris herba) and of the roots of horseradish (Armoraciae rusticanae radix)].

OBJECTIVE

To evaluate the in-vitro antimicrobial properties of a commercialized preparation (Angocin Anti-Infekt N) containing a combination of the haulm of nasturtium (Tropaeoli majoris herba; N) and of the roots of horseradish (Armoraciae rusticanae radix; H). This preparation can be used to treat upper respiratory tract (URTI) and urinary tract infections (UTI). The active ingredients are volatile mustard oils, which are activated in the gastrointestinal tract after oral intake. Previous research has shown mustard oils derived from either N or H to possess antibacterial activity.

METHODS

In order to assess the antimicrobial capacity of phytotherapeutic compounds containing volatile mustard oils, a modified gas-test was used. Native preparations of N and H were applied to the lids of Columbia agar plates (ratio N:H = 2.5:1) and mixed with sterile H20. Thirteen different bacterial species including Haemophilus influenzae, Moraxella catarrhalis, Escherichia coli, Pseudomonas aeruginosa, Streptococcus pyogenes, methicillin-susceptible and resistant Staphylococcus aureus (MSSA, MRSA) were tested (20 isolates each). The test organisms were plated onto the blood agar plates and placed above the native preparations. The plates were sealed with adhesive tape and incubated at 37 degrees C. Following incubation of 24 h and 92 h, colony forming units (CFU) were counted and the minimal inhibitory concentrationg (MIC90) was determined for each bacterial species.

RESULTS

Relevant antimicrobial activities of the combined native preparations were found against H. influenzae (MIC90 50 mg N / 20 mg H), M. catarrhalis (100 mg N / 40 mg H), E. coli (400 mg N / 160 mg H), P aeruginosa (400 mg N / 160 mg H), MSSA (400 mg N 1 160 mg H), MRSA (400 mg N / 160 mg H), and S. pyogenes (400 mg N / 160 mg H).

CONCLUSIONS

Antimicrobial testing of a combination of N and H revealed broad antibacterial activities against clinically relevant pathogens covering both gram-positive and gram-negative organisms, thus confirming previous reports of the antibacterial properties of mustard oils. Additionally, this study demonstrated that the combination of N and H leads to synergistic activity in terms of improved Pseudomonas-susceptibility compared to the previous reported activities of the single compounds. Thus, these results prove that there is a rational basis for treatment of URTI and UTI with a combination of N and H.