Several potentially pathogenic bacteria have the capacity to cause respiratory symptoms, resulting from initial interactions with epithelial cells of the oral and nasal mucosa and various parts of the lung. General features of infection by these organisms include proliferation and spread of the bacteria with resultant cellular damage, often aided by products of bacterial virulence genes, and the induction of excessive proinflammatory cytokines, which can lead to chronic inflammation. A herbal medicine with bactericidal and anti-inflammatory properties could provide benefits to individuals suffering from respiratory symptoms, and certain preparations of EP possess these activities, in addition to their antiviral activities described above. Results are summarized in .
Antimicrobial effects of EP.
(Group A streptococcus, or GAS) is responsible for widespread infections, ranging from hundreds of millions of relatively mild cases of pharyngitis globally, to more severe toxic shock syndromes and necrotizing fasciitis (“flesh-eating disease”), the more severe symptoms being ascribed to inflammatory cytokines (“cytokine storms”). In addition several Streptococcal
gene products or virulence factors have been described which aid the bacteria in persistence in oral epithelia and saliva and dissemination to other tissues [63
]. Consequently the dual actions of EP in killing the bacteria and reversing their proinflammatory activities could be a significant aid in combating such infections.
is part of the normal naso-pharyngeal flora. Recently additional pathogenic strains have been associated with otitis media, chronic bronchitis, and pneumonia. Initial interaction with epithelial cells can result in proinflammatory cytokine secretion, via toll receptors and other mediators [66
]. EP can kill this organism readily and also inhibit the cytokine induction in bronchial epithelial cells ().
associated with Legionnaires' disease and sometimes more severe cases of pneumonia, is widely distributed in water and soil, from which the organism can be inhaled as an aerosol and once inside alveolar macrophages localizes in a relatively resistant vacuole, in which it replicates [68
]. The organism is however very sensitive to EP, and its induction of proinflammatory cytokines is inhibited by EP treatment ().
has long been recognized as part of the normal skin flora, but Methicillin-resistant (MRSA) strains have been associated in recent years with increased frequency of hospital-acquired infections, resulting in severe pneumonia [70
]. Preparations of EP had relatively little effect on growth of MRSA or MSSA (methicillin sensitive S. aureus
) but were very effective in inhibiting the proinflammatory response to the bacteria, indicating at least partial benefits in counteracting the detrimental effects of MRSA infection. Klebsiella pneumoniae
, often associated with antibiotic resistant pneumonia, was also relatively resistant to the bactericidal effects of EP, as were Mycobacterium smegmatis
and several other bacterial opportunists [62
Several conclusions were drawn from these results: (i) EP and other Echinacea extracts were selective in their antibacterial activities; (ii) different organisms showed significant differences in their patterns of sensitivity; (iii) there were no correlations between chemical composition of extracts, in terms of known marker compounds, and their corresponding antibacterial activities; (iv) different preparations of Echinacea showed markedly different effects on bacteria, indicating that EP has distinct mechanisms of action against each bacterium; (v) in general EP can reverse the stimulation of proinflammatory cytokines regardless of the inducing bacterium or virus.
In addition to the studies with live bacteria, several groups have examined the effects of EP on the stimulation of inflammatory mediators by bacterial lipopolysaccharide (LPS usually derived from Escherichia coli
) in various human and mouse cell cultures (see below, Section 12
). Such models can serve as useful tests for anti-inflammatory agents [23
], although they do not necessarily represent live bacteria. These studies together indicate that EP is effectively a general anti-inflammatory agent and should be capable of ameliorating many of the symptoms of respiratory infections.