Data of de novo genome assembly of the Chlamydia psittaci strain isolated from the livestock in Volga Region, Russian Federation

Complete genome sequence of Chlamydia psittaci АМК-16, isolated from a small ruminant in the Middle Volga Region, Russia

We report the complete genome sequence of the Chlamydia psittaci АМК-16, recovered from the aborted caprine fetus during a case of chlamydia infection. This 1,152,497-bp genome with 7,552-bp cryptic plasmid provides novel insights into the genetic diversity of chlamydia agent strains particularly those causing the infection in small ruminants.

Whole genome sequencing characteristics of Chlamydia psittaci caprine AMK-16 strain, a promising killed whole cell veterinary vaccine candidate against chlamydia infection

Chlamydia psittaci is a primary zoonotic pathogen with a broad host range causing severe respiratory and reproductive system infection in animals and humans. To reduce the global burden of C. psittaci-associated diseases on animal welfare and health and to control the pathogen spread in husbandry, effective vaccines based on promising vaccine candidate(s) are required. Recently, the caprine C. psittaci AMK-16 strain (AMK-16) demonstrated a high level of protection (up to 80-100%) in outbred mice and pregnant rabbits immunized with these formaldehyde-inactivated bacteria against experimental chlamydial wild-type infection. This study investigated the molecular characteristics of AMK-16 by whole-genome sequencing followed by molecular typing, phylogenetic analysis and detection of main immunodominant protein(s) eliciting the immune response in mouse model. Similarly to other C. psittaci, AMK-16 harbored an extrachromosomal plasmid. The whole-genome phylogenetic analysis proved that AMK-16 strain belonging to ST28 clustered with only C. psittaci but not with Chlamydia abortus strains. However, AMK-16 possessed the insert which resulted from the recombination event as the additional single chromosome region of a 23,100 bp size with higher homology to C. abortus (98.38-99.94%) rather than to C. psittaci (92.06-92.55%). At least six of 16 CDSs were absent in AMK-16 plasticity zone and 41 CDSs in other loci compared with the reference C. psittaci 6BC strain. Two SNPs identified in the AMK-16 ompA sequence resulted in MOMP polymorphism followed by the formation of a novel genotype/subtype including three other C. psittaci strains else. AMK-16 MOMP provided marked specific cellular and humoral immune response in 100% of mice immunized with the inactivated AMK-16 bacteria. Both DnaK and GrpE encoded by the recombination region genes were less immunoreactive, inducing only a negligible T-cell murine immune response, while homologous antibodies could be detected in 50% and 30% of immunized mice, respectively. Thus, AMK-16 could be a promising vaccine candidate for the development of a killed whole cell vaccine against chlamydiosis in livestock.

[Type III secretory protein SINC of Chlamydia psittaci promotes host cell autophagy by activating the MAPK/ERK signaling pathway]

OBJECTIVE

To investigate the effects of SINC, a secreted protein of Chlamydia psittaci, on autophagy of host cells and the role of MAPK/ERK signaling pathway in mediating SINC-induced autophagy.

METHODS

RAW 264.7 cells treated with recombinant SINC were examined for changes in expression levels of LC3-II, Beclin-1, phosphorylated and total ERK1/2 using Western blotting. The expression level of LC3 in the treated cells was detected using immunofluorescence analysis, and the formation of autophagosomes and autolysosomes was observed with transmission electron microscopy (TEM). The effect of pretreatment with U0126 (a specific ERK inhibitor) on the expression levels of LC3-II and Beclin-1 in RAW 264.7 cells exposed to different concentrations of SINC was examined using Western blotting, and LC3 puncta in the cells was detected with immunofluorescence analysis.

RESULTS

The expression levels of LC3-II and Beclin-1 were the highest in RAW 264.7 cells treated with 2 μg/mL SINC for 12h. Immunofluorescence analysis showed exposure to SINC significantly increased the number of cells containing LC3 puncta, where the presence of autophagosomes and autolysosomes was detected. Exposure to 2 μg/mL SINC for 15 min resulted in the most significant increase of the ratios of p-ERK1/2/ERK1/2 in RAW 264.7 cells. Pretreatment of the cells with U0126 prior to SINC exposure significantly decreased the ratio of p-ERK1/2/ERK1/2, lowered the expression levels of LC3-II and Beclin-1, and decreased LC3 aggregation in the cells.

CONCLUSIONS

SINC exposure can induce autophagy in RAW 264.7 cells by activating the MAPK/ERK signaling pathway.

Chlamydia abortus Isolation and Identification in Aborted Ovine Fetus in Mari El Republic of Russia

Reproductive disorders, presumably caused by Chlamydia abortus, are common among the ovine population of the Mari El Republic, Russia. C. abortus infection was determined by serologic testing or isolation and detection of the organism by PCR and direct immunofluorescence in tissue samples. Rams, ewes, and lambs (10 individuals each) were randomly chosen for serological testing by the complement fixation test and 7 of 30 (23%) animals tested were positive. Tissue samples were collected from ewes and aborted fetuses for isolation by inoculating chicken embryo yolk sacs (n = 41). The same samples were analyzed by PCR using commercial and in-house PCR kits and by direct immunofluorescence. C. abortus was detected in 58.5% of samples using PCR and in 60.9% of the samples by direct immunofluorescence. Five Chlamydia isolates were cultured in egg yolk sacs and adapted for growth in cell cultures. Phylogenetic analysis showed no substantial difference between Russian isolates and those from other parts of the world. The results of the study further demonstrate the usefulness of PCR for detection of C. abortus as a faster, simpler, and more reliable approach in comparison to culturing the organism and underscoring the necessity of screening for chlamydiosis as a cause of ovine abortion.

Chlamydia psittaci in Faecal Samples of Feral Pigeons (Columba livia forma urbana) in Urban Areas of Lublin city, Poland

Pigeons are a typical host and natural reservoir of Chlamydia psittaci, the etiological agent of avian chlamydiosis, considered as a neglected zoonotic diseases. The aim of the study was to determine the prevalence of C. psittaci in faecal samples of feral pigeons (Columba livia forma urbana) as a potential source of infection related to the presence of synanthropic birds in urban areas. A total of 143 samples of dry and fresh faeces of feral pigeons, were collected in the city of Lublin (Poland), from April to September 2021. Molecular detection of C. psittaci was performed by nested-PCR and real-time PCR, confirmed by sequencing. Among the collected samples, 5 positive results were obtained in nested-PCR (3.5%), while in real-time PCR, the number of positive samples increased to 11 (7.7%). The positive samples showed 100% identity to the C. psittaci strain AMK (CP047319.1). C. psittaci was found in 7 out of 111 (6.3%) faecal samples collected in public places, and in 4 out of 32 (12.5%) samples from the nesting site (4.9% and 2.8% among a total of 143 samples, respectively). The infection was detected in both dry and fresh faeces (9.1% and 4.5%, respectively). The highest number of positive results was obtained in June—5 (3.5%). Feral pigeons occurring in urban areas are a natural reservoir of C. psittaci posing a potential risk of zoonotic infections. However, further studies on exposure to contaminated pigeon faeces in terms of occupational and non-occupational risk of chlamydiosis are needed.