Moraxella catarrhalis - pathogen or commensal
Type of Spiritual Experience
After a sudden increase in ambient temperature, which is termed heat shock, bacteria respond by expressing a specific set of genes whose protein products are designed to mainly cope with heat-induced alterations of protein conformation. This heat shock response comprises the expression of protein chaperones and proteases, and is under central control of an alternative sigma factor (sigma 32) which acts as a master regulator that specifically directs RNA polymerase to transcribe from the heat shock promotors. In a similar manner, bacteria express a well-defined set of proteins after a rapid decrease in temperature, which is termed cold shock. This protein set, however, is different from that expressed under heat shock conditions and predominantly comprises proteins such as helicases, nucleases, and ribosome-associated components that directly or indirectly interact with the biological information molecules DNA and RNA.
A description of the experience
Adv Exp Med Biol. 2011;697:107-16. doi: 10.1007/978-1-4419-7185-2_9.
Moraxella catarrhalis - pathogen or commensal?
1Department of Pediatrics and Institute for Infectious Diseases, University of Bern, Inselspital, Bern, Switzerland. email@example.com
Moraxella catarrhalis is an exclusively human commensal and mucosal pathogen. Its role as a disease-causing organism has long been questioned.
Today, it is recognized as one of the major causes of acute otitis media in children, and its relative frequency of isolation from both the nasopharynx and the middle ear cavity has increased since the introduction of the heptavalent pneumococcal conjugate vaccine, which is associated with a shift in the composition of the nasopharyngeal flora in infants and young children.
Although otitis media caused by M. catarrhalis is generally believed to be mild in comparison with pneumococcal disease, numerous putative virulence factors have now been identified and it has been shown that several surface components of M. catarrhalis induce mucosal inflammation.
In adults with chronic obstructive pulmonary disease (COPD), M. catarrhalis is now a well-established trigger of approximately 10% of acute inflammatory exacerbations.
Although the so-called cold shock response is a well-described bacterial stress response in species such as Escherichia coli, Bacillus subtilis or - more recently - Staphylococcus aureus, M. catarrhalis is the only typical nasopharyngeal pathogen in which this response has been investigated.
Indeed, a 3-h 26°C cold shock, which may occur physiologically, when humans inspire cold air for prolonged periods of time, increases epithelial cell adherence and enhances proinflammatory host responses and may thus contribute to the symptoms referred to as common cold, which typically are attributed to viral infections.