Differences in growth characteristics and elementary body associated cytotoxicity between Chlamydia trachomatis oculogenital serovars D and H and Chlamydia muridarum.
OBJECTIVE
In vitro growth and elementary body (EB) associated cytotoxicity of two Chlamydia trachomatis strains belonging to serovars D and H and C muridarum were compared to identify difference(s) that correlate with virulence variations between these strains in the mouse model of human female genital tract infection, and phenotypic characteristics that could explain human epidemiological data on serovar prevalence and levels of shedding during serovar D and H infection.


METHODS
Replication cycle kinetics, inclusion characteristics, and EB associated cytotoxicity were assessed in McCoy cell monolayers using culture, light microscopy, and lactate dehydrogenase release.


RESULTS
Over 72 hours, more rapid production and release of inclusion forming units (ifu) allowed C muridarum to initiate two replication rounds, resulting in 4-8 times more ifu/input unit of infection than with serovars D and H. Although C muridarum EBs were significantly more cytotoxic to McCoy cell monolayers than serovar D at moderate and high multiplicity of infection ratios (MOI), serovar H EBs were significantly more cytotoxic than C muridarum, even at the lowest MOI tested.


CONCLUSIONS
These phenotypic differences are consistent with the more invasive course and severe pathological outcome of infection in mice infected with C muridarum, providing an objective basis for questioning the appropriateness of C muridarum as a surrogate for the human biovar of C trachomatis in the murine model of female genital tract infection. The differences seen between the human strains could help explain human epidemiological data relating to differences in prevalence and level of shedding that occurs during infection with oculogenital serovars D and H.
Lyons
J M
JM
Department of Infectious Diseases, City of Hope National Medical Center and Beckman Research Institute, Duarte, California 91010, USA. jlyons@coh.org
Ito
J I
JI
Peña
A S
AS
Morré
S A
SA
D002453:Cell Cycle / Q000502:physiology; D002690:Chlamydia Infections / Q000382:microbiology; D023502:Chlamydia muridarum / Q000254:growth & development* / Q000472:pathogenicity; D002692:Chlamydia trachomatis / Q000254:growth & development* / Q000472:pathogenicity; D003470:Culture Media; D003603:Cytotoxins / Q000032:analysis; D005260:Female; D005831:Genital Diseases, Female / Q000382:microbiology; D006801:Humans; D002479:Inclusion Bodies / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D012703:Serotyping; D014774:Virulence
D003470:Culture Media; D003603:Cytotoxins; D007770:L-Lactate Dehydrogenase