1. DBD Streptococcus Laboratory
There are exciting and varied areas of research to pursue in the Streptococcus laboratory. We focus upon the characterization of disease-causing streptococcal isolates and developing better molecular methods for carrying out this work. We are also developing and refining DNA sequence based systems for detecting and characterizing streptococcal pathogens from clinical sources and nasopharyngeal carriage. We monitor the effects of vaccine selective pressure upon the overall invasive pneumococcal population genetic structure as well as the emergence and evolution of specific clones. We support development of prevention strategies against beta-hemolytic streptococci and pneumococci through large scale, detailed strain surveillance. See http://www.cdc.gov/ncidod/biotech/strep/strepindex.htm for more information about the laboratory.
Carvalho, MD, Jagero G, Bigogo GM, Junghae M, Pimenta FC, Moura I, Roundtree A, Li Z, Conklin L, Feikin DR, Breiman RF, Whitney CG, Beall B. 2012. Potential non-pneumococcal confounding of PCR-based determination of serotype in carriage. J Clin Microbiol. 50:3146-7.
Massire C, RE Gertz, Jr., P Svoboda, K Levert, MS Reed. J Pohl, R Kreft, F Li, N White, R Ranken, LB Blyn, DJ Ecker, R Sampath, B Beall. 2012. Concurrent serotyping and genotyping of pneumococci by use of PCR and electrospray ionization mass spectrometry. J. Clin. Microbiol. 50:2018-25.
Srinivasan S, RE Gertz,Jr, PL Shewmaker, S Patrick, AS Chitnis, H O’Connell, I Benowitz, P Patel, AY Guh, J Noble-Wang, G Turabelidze, B Beall. 2012. Using PCR-based detection and genotyping to trace Streptococcus salivarius meningitis outbreak strain to oral flora of radiology physician assistant PLoS One. 7(2):e32169.
Beall BW., RE Gertz, Jr., RL Hulkower, CG Whitney, MR Moore, AB Brueggemann. 2011. Shifting Genetic Structure of Invasive Serotype 19A Pneumococci in the United States. J. Infect. Dis. 360-8.
Srinivasan V, du Plessis M, Beall B, McGee L. 2011. Quadriplex real time PCR assay for simultaneous detection of pneumococci and antibiotic resistance Diagnostic Microbiology and Infectious Disease. J. Med. Microbiol. 71:453-6.
Gertz, RE., Li Z, Pimenta FC, Jackson D, Juni BA, Lynfield R, Carvalho MD, Beall BW. 2010. Increased penicillin-nonsusceptibility of non-vaccine serotype (other than 19A and 6A) invasive pneumococci in post 7 valent conjugate vaccine era. J Infect Dis. 201:770-5.
2. DBD Understanding the molecular basis of virulence bias within the genus Legionella and developing new detection strategies.
The Legionella laboratory resides within the Respiratory Diseases Branch of the Division of Bacterial Diseases. Our main focus is the gamma-proteobacteria Legionella that are ubiquitous in fresh water environments worldwide and cause a severe form of pneumonia called Legionnaires’ disease. Even though there are more than 54 species known to belong to the genus Legionella, more than 90% of the isolates associated with Legionnaires’ disease belong to the species Legionella pneumophila and 79% of legionellosis cases are due to Legionella pneumophila serogroup 1 (Lp1). This phenomenon could be due to increased virulence of Lp1 strains or biased diagnostic techniques, the majority of which are focused on detection of Lp1 but not other species or serogroups of legionellae. We are interested in understanding the molecular basis for the increased virulence of Legionella pneumophila and Lp1 in general and of certain genotypes within Lp1 in particular. These include several genotypes identified during our sequence based typing (SBT) analysis of Lp1 isolates from our historic collection: we determined that some SBT types are associated with legionellosis outbreaks more frequently than others. In addition, we showed that more clinical than environmental Lp1 isolates carry the lag-1 gene, which is responsible for reactivity with monoclonal antibody 2 (MAb2) or “virulence-associated” epitope. A lag-1 mutant has been created by the allelic exchange technique in our lab and a comprehensive comparison of this mutant with its wild type counterpart is pending. We would also like to expand detection methods on other serogroups and species of legionellae. For that, we have sequenced over 30 non-Lp1 genomes and are in the process of annotation and characterization. The development of new, more comprehensive DNA-based diagnostic methods will help to obtain a more complete picture of the prevalence of legionellosis in the U.S. and worldwide.
Travis TC, Brown EW, Peruski LF, Siludjai D, Jorakate P, Salika P, Yang G, Kozak NA, Kodani M, Warner AK, Lucas CE, Thurman KA, Winchell JM, Thamthitiwat S, Fields BS. 2012. Survey of legionella species found in Thai soil. Int J Microbiol; 2012:218791
Silk BJ, Moore MR, Bergtholdt M, Gorwitz RJ, Kozak NA, Tha MM, Brown EW, Winchester JL, Labus BJ, Rowley P, Middaugh JP, Fields BS, Hicks LA. 2012. Eight years of Legionnaires' disease transmission in travellers to a condominium complex in Las Vegas, Nevada. Epidemiol Infect; Jan 4:1-10
Kozak NA, Buss M, Lucas CE, Frace M, Govil D, Travis T, Olsen-Rasmussen M, Benson RF, Fields BS. 2010. Virulence factors encoded by Legionella longbeachae identified on the basis of the genome sequence analysis of clinical isolate D-4968. J Bacteriol; 192(4):1030-44
Kozak NA, Benson RF, Brown E, Alexander NT, Taylor TH Jr, Shelton BG, Fields BS. 2009. Distribution of lag-1 alleles and sequence-based types among Legionella pneumophila serogroup 1 clinical and environmental isolates in the United States. J Clin Microbiol; 47(8):2525-35.