My postdoctoral research focuses on persistence in the opportunistic pathogen Pseudomonas aeruginosa.

My graduate work focused on determining the effects of the use of antimicrobials administered by mass medication in the New Zealand poultry industry on the development of antimicrobial resistance, using enterococci as the indicator organism. This research represented the first report of vancomycin-resistant enterococci (VRE) isolated from food animals in New Zealand. VRE were only isolated from poultry suppliers that were using or had previously used the antimicrobial compound avoparcin (a glycopeptide antimicrobial with the same mode of action as vancomycin). After surveying poultry farms from across the country it was found that two years after the withdrawal of avoparcin, VRE were still present in broiler chickens making up approximately 5.8% of enterococci from this source. A clonal lineage of vancomycin-resistant Enterococcus faecalis was found to be present in poultry from all major suppliers, and was also found in supermarket chicken, humans and dogs in New Zealand. In this study it was also noted that large numbers of enterococci had MICs >= 256 μg/ml to bacitracin, and as the genetic basis for bacitracin resistance in enterococci had not been elucidated, this phenotype was further investigated. Two genes, specifically bcrA and bcrB, were identified as essential for the resistance phenotype using transposon mutagenesis and encode a putative ABC transporter. In the same operon a third gene, bcrD, was identified which encodes a putative undecaprenol kinase. Upstream of these is a fourth gene, bcrR, encoding a putative regulatory protein, which is membrane-bound. This gene is necessary for transciption of the bcrABD operon and preliminary data suggested that BcrR interacted with the promoter region of this operon.

My first postdoctoral position also focused on the bacterium Enterococcus faecalis. The Enterococcus faecalis pathogenicity island (PAI) encodes 129 predicted ORFs, and contains the virulence traits, Esp, cytolysin, and aggregation substance. The presence of phage-related integration proteins, conjugative plasmid derived sequences and direct repeats flanking the island, suggest that the element may in fact be mobile as a unit.To test this hypothesis, three E. faecalis V583 strain derivatives were constructed by single crossover integration of a tetracycline resistance plasmid, p3TET, into several loci within the PAI. Interestingly, transfer of the entire PAI was detected from all three constructs with similar transfer frequencies, however, inactivation of the integrase, excisionase, and conjugation genes and no effect on transfer, and five different classes of transconjugant were apparent, as judged by Pulsed-Field gel electrophoresis (PFGE). Comparative genome hybridisation was used to confirm that the entire PAI had transferred, and restriction fragment length polymorphisms (RFLP) and SNP mapping was used to determine the borders of the transferred DNA (between 285 to 857-kb). To determine whether other regions of the chromosome could also transfer, and whether a transfer gradient was present a collection of genome wide, integration mutants were tested for transfer of tetracycline resistance, and each mating yielded transconjugants (transfer rates ranging from 1.09 x 10-5 to 9.06 x 10-11). Further characterization of these transconjugants revealed that multiple types of transfer events could occur from the same locus, and that the tetracycline resistance marker could be chromosomally located or plasmid-borne in the recipient strain. To determine the role that the resident plasmids (pTEF1 and pTEF2) play in chromosomal DNA transfer, the plasmid-free strain OG1RF was marked with tetM, (OG1RF::pJMM42erlA). Transfer of tetracycline resistance was only detected in OG1RF::pJMM42erlA carrying either pTEF1 or pTEF2, and not in the plasmid-free parental strain. In addition, a plasmid-free variant of V583 was found to lack the ability to transfer an integrated tetracycline resistance marker. Deletion of the oriTs, relaxase genes, or TraG-homologues of both pTEF1 and pTEF2, abolished transfer, and because oriT's act in cis, suggest that recombination of plasmid and chromosomal DNA is essential for transfer to occur. Recombination events between IS256 sequences on pTEF1, pTEF2 and the chromosome were detected using PCR, further supporting a model of plasmid and chromosomal recombination and subsequent transfer of chromosomal DNA.

Publications:

Original Articles:

Manson, J.M., Smith, J.M.B., and Cook, G.M. Isolation and characterization of vancomycin-resistant enterococci from chickens in New Zealand. New Zealand Medical Journal 2001;114:456.

Manson, J. M., Keis, S., Smith, J.M.B. and Cook, G.M. A clonal lineage of VanA-type Enterococcus faecalis predominates in vancomycin-resistant enterococci isolated in New Zealand. Antimicrobial Agents and Chemotherapy 2003;47:204-210.

Manson, J.M., Keis, S., Smith, J.M.B. and Cook, G.M. Characterization of a vancomycin-resistant Enterococcus faecalis (VREF) isolate from a dog with mastitis: Further evidence of a clonal lineage of VREF in New Zealand. Journal of Clinical Microbiology 2003;41:3331-3333.

Manson, J. M., Smith, J.M.B. and Cook, G.M. Persistence of Vancomycin-Resistant Enterococci in New Zealand Broilers after the Discontinuation of Avoparcin Use. Applied and Environmental Microbiology 2004;70:5764-5768.

Manson, J. M., Keis, S., Smith, J.M.B. and Cook, G.M. Acquired bacitracin resistance in Enterococcus faecalis is mediated by an ABC transporter and a novel regulatory protein BcrR. Antimicrobial Agents and Chemotherapy 2004;48:3743-3748.

Dufour, M., J. M. Manson, P. J. Bremer, J. Dufour, G. M. Cook, and R. S. Simmonds. Characterization of Monolaurin Resistance in Enterococcus faecalis. Applied and Environmental Microbiology 2007:73:5507-5515.

Gauntlett, J. C., S. Gebhard, S. Keis, J. M. Manson, K. M. Pos, and G. M. Cook. Molecular analysis of BcrR: A membrane-bound bacitracin sensor and DNA-binding protein from Enterococcus faecalis. Journal of Biological Chemistry 2008:283:8591-8600.

Commentaries:

Cook, G.M., J.M. Manson, and J.M.B. Smith. Time to ban all non-therapeutic use of antimicrobials in New Zealand animals. New Zealand Biosciences 2003;12:38-41.

Cook, G.M., J.M. Manson, and J.M.B. Smith. First report of vancomycin-resistant enterococci from poultry in New Zealand. Antibiotics Chemotherapy 2001;5:16-19.

Manson, J. M. and M. S. Gilmore. Pathogenicity island integrase cross-talk: a potential new tool for virulence modulation. Molecular Microbiology (2006); 61(3):555-559.

Book Chapters:

Manson, J. M. and M. S. Gilmore.2006. Pathogenomics of Enterococcus faecalis, p. 125-148 In Hacker. J., Dobrindt, U., and W. Göbel (ed.), Pathogenomics: Genome Analysis of Pathogenic Microbes. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Manson, J. M., M. Rauch, and M. S. Gilmore. The Commensal Microbiology of the Gastrointestinal Tract. Advances in Experimental Medicine and Biology. 2008; 635:15-28.