Genomic signature of multi-drug resistant Salmonella typhi related to the massive outbreak in Zambia year 2010 to 2012

Abstract

Background: The interepidemic meningococcal infection (MI) period inMoscowhas been going since the 1989. Outbreaks of general forms of MI (GFMI) were registered in 1996, 2003, 2008 with their morbidity rates per 100,000 persons (MR) of 4.23, 3.63 and 2.59. In 2012 MR was at 1.56. Methods & Materials: Meningococcus strains isolated from GFMI patients in Moscow Infectious Diseasaes Clinic were serogrouped, and the specifics of the immunological structure of the population of Moscow were defined. Results: The predominance of meningococcal serogroup A (MSA)was shown. The highestMSAdensitywas registered in 1996, 2003, 2008 (78.6, 61.5, 76.2%%). MSA density increased in2009 2012 (47.7 83.7%%). The study of the immunological structure of the population using passive hemagglutination test showed, that in 1993-2003 the number of MSA seropositive persons was high (70-90%). The study conducted in 2004-2012 using enzyme immunoassay allowed both to estimate the state of immunity and indirectly asses the MSA circulation. The presence in the blood serum of IgM antibodies indicates a fresh infection; IgG a previous infection and the presence of immunity; IgM+ IgG a fresh infection or reinfection. The years 2004 2005 marked significant MSA circulation with a small amount of non-immune individuals. The proportion of adults with IgM, IgM+ IgG antibodies was 65%, with IgG 24%. In the years 2006-2010 the proportion of individuals with IgM, IgM+ IgG, IgG decreased and the proportion of seronegative individuals increased. The year 2011 resumed the tendency for the growth of the proportionofpersonswith IgM, IgM+ IgGantibodies. In2012 it reached 21.9% in adults and 15.6% in children. Proportion of persons with IgG antibodies decreased to less than 2%. Seronegative were 76.4% of adults and 83.1% of children. Conclusion: The sporadic incidence of MI in Moscow does not diminishMSA’s significance in the structure of GFMI. There is a tendency towards increased MSA circulation with the parallel large amount of non-immune individuals. The studies have to be continued in order to assess changes in the epidemiological situation and at the first sign of trouble to carry out adequate preventive measures.