The upper respiratory tract (URT) of humans is complex and interconnected region and comprises several major ecosystems including the oral cavity, oropharynx, nasal cavity, sinuses, nasopharynx and middle ear. Most of the anatomical locations within the URT are colonised with a normal bacterial microbiota, within which are often organisms having the potential to cause disease. The diseases of the URT are both varied and frequent in their occurrence, and conditions such as otitis media, rhinosinusitis and pharyngitis are sources of morbidity and mortality in adults and children in both developing and developed countries.
The study of diseases of the URT has traditionally been based on application of culture-based methods in which the infection-implicated organisms are first grown in vitro and then studied further. Ongoing advances in DNA-based techniques have led to the development of new molecular tools for the study of infectious diseases. One such technique is PCR-denaturing gradient gel electrophoresis (PCR-DGGE). This is a PCR-based tool that allows the investigation of microbial communities independent of culture. Although this technique has been applied extensively in the study of the gastrointestinal tract, the vagina and endodontic infections in humans, there have been few reports of its application to URT infections. PCR-DGGE was applied in the present study to investigate (a) the bacteria present in the middle ear of children suffering from otitis media with effusion (OME), (b) the microbiota associated with the sinuses in patients with chronic rhinosinusitis (CRS) and (c) perioperative changes in the bacterial population of the middle meatus of patients undergoing nasal or sinus surgery. The analysis of the middle ear fluid samples indicated an increased role in OME for the newly-discovered pathogen Alloiococcus otitidis and also the possible involvement of certain coryneform bacteria and coagulase-negative staphylococci in the aetiology of this condition. PCR-DGGE analysis of patients with CRS revealed a polymicrobial disease with considerable variability in the predominant species detected when multiple, serial samples were evaluated. The perioperative audit showed that when good clinical practice is adhered to, there was no apparent introduction of potentially-harmful organisms into the middle meatus.
Streptococcus salivarius is a common, commensal inhabitant of the oral cavity of humans and has also been shown to inhabit the nasopharynx of infants. S. salivarius is also a well known producer of bacteriocins with activity directed against Streptococcus pyogenes. One such strain, S. salivarius K12, is now marketed in New Zealand as the probiotic, K12 Throat Guard[TM]. In the present study, S. salivarius K12 was compared with two additional strongly-inhibitory S. salivarius (strains T18A and T30A) for activity against the common causative pathogens of otitis media. A paediatric formulation of strain K12 was also tested in a pilot clinical trial for its ability to colonise the URT of young children. Although the levels of colonisation of these subjects was not as high as typically obtained with use of the K12 Throat Guard[TM] formulation, it was considered that further development of the paediatric formulation is warranted, particularly with respect to use of a different pre-treatment regimen. In other studies, the molecular basis for the unusual in vitro inhibitory activity of S. salivarius strain T30A was investigated. Although this still remains unresolved, other observations made during the course of this study have led to the introduction of a schema for the division of inhibitory S. salivarius into three groups based on (a) their sensitivity to the lantibiotic salivaricin A and (b) the structure of their salivaricin A genetic locus. This grouping is analogous to the "rock-paper-scissors" system previously described for colicin-producing strains of E. coli.
Streptococcus pneumoniae is a major human pathogen responsible for a variety of diseases in humans. There have been very few reports of bacteriocin production by S. pneumoniae when compared to other streptococcal species. In the present study a putative cluster of bacteriocins encoded by the blp locus has been investigated. The distribution of the individual blp determinants within this locus was evaluated in a collection of S. pneumoniae strains using PCR. The blp genes were detected in 92% of 57 tested strains and a variant form (termed the B-form) of the cluster was identified that appeared to have arisen due to a genetic recombination event. In this case an approximately 250 bp portion of the blpMNO cluster appears to have recombined into blpK of the blpIJK cluster. Attempts were made to express the putative bacteriocin peptide genes in an Escherichia coli expression system. Failure to achieve expression was taken to indicate that these bacteriocin-like peptides may be toxic for the host producer cells under these test conditions. Future attempts to achieve expression of the Blp peptides, could explore the use of different fusion proteins, a Gram-positive expression host or a cell-free protein expression system.
| Identifer | oai:union.ndltd.org:ADTP/217734 |
| Date | January 2007 |
| Creators | Power, Daniel Aaron, n/a |
| Publisher | University of Otago. Department of Microbiology & Immunology |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://policy01.otago.ac.nz/policies/FMPro?-db=policies.fm&-format=viewpolicy.html&-lay=viewpolicy&-sortfield=Title&Type=Academic&-recid=33025&-find), Copyright Daniel Aaron Power |
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