The influence of centrifugation and incubation temperatures on various veterinary and human chlamydial species.

The Chlamydiaceae are Gram-negative bacteria causing diseases in humans and in both, endothermic (mammals and birds) and poikilothermic (e.g. reptiles, amphibians) animals. As most chlamydial species described today were isolated from humans and endothermic animals, the commonly used culturing temperature in vitro is 37 °C, although the centrifugation temperature during experimental infection, a technique necessary to improve the infection rate, may vary from 25 to 37 °C. The aim of this study was to investigate the influence of different centrifugation (28° or 33 °C) and incubation temperatures (28 °C or 37 °C) on the average inclusion size, infectivity and ultrastructural morphology of human and animal chlamydial strains, as well as two recently described species originating from snakes, C. poikilothermis and C. serpentis, in LLC-MK2 cells at 48 h post infection. Infectivity and average inclusion size was reduced at an incubation temperature of 28 °C compared to 37 °C for all strains including C. poikilothermis, although the latter formed larger, fully matured inclusions at 28 °C in comparison to the other investigated Chlamydia species. C.psittaci displayed a shorter developmental cycle than the other species confirming previous studies. Higher centrifugation temperature increased the subsequent inclusion size of C. trachomatis, C. abortus and C. suis but not their infectivity, while the incubation temperature had no discernable effect on the morphology, inclusion size and infectivity of the other chlamydial strains. In conclusion, we found that all Chlamydia species are viable and can grow at low incubation temperatures, although all strains grew better and more rapidly at 37 °C compared to 28 °C.

Novel Chlamydia species isolated from snakes are temperature-sensitive and exhibit decreased susceptibility to azithromycin.

Chlamydia species have recently been recognized as emerging pathogens in snakes. However, isolation of novel snake chlamydiae is critical and their growth characteristics are largely unknown. In this study, two novel chlamydial species are described: Chlamydia serpentis and Chlamydia poikilothermis, isolated after attempts on 23 cloacal and choanal swabs from 18 PCR-positive captive snakes originating from different Swiss snake collections. Isolation success, growth curve and infectivity rates over a 48-hour time period were dependent on temperature (37 °C for C. serpentis, 28 °C for C. poikilothermis). C. serpentis and C. poikilothermis were sensitive to tetracycline and moxifloxacin during evaluation by in vitro antibiotic susceptibility assay but intermediate to resistant (2-4 µg/ml) to azithromycin. Whole genome sequencing of the isolates provided proof of the novel species status, and gives insights into the evolution of these branches of genus Chlamydia.

Chlamydiosis in Backyard Chickens (Gallus gallus) in Italy.

Until recently, Chlamydia psittaci was considered to be the only etiological agent of avian chlamydiosis, but two new avian species, Chlamydia gallinacea and Chlamydia avium, have recently been described in poultry and pigeons or psittacine birds, respectively. The aim of this study was to explore the occurrence of C. psittaci and C. gallinacea in backyard chickens in Italy. Cloacal swabs were taken from 160 asymptomatic chickens reared in 16 backyard farms. Samples were tested for C. psittaci and C. gallinacea by specific real-time polymerase chain reaction assays, with 24 (15%) of the 160 chickens resulting positive for C. gallinacea. To attempt chlamydial isolation, new samples were obtained from two farms harboring a high prevalence (60% and 70%, respectively) of C. gallinacea-positive chickens. In total, eight C. gallinacea and one C. psittaci isolates were successfully recovered from 13 chickens. C. gallinacea was confirmed to be the endemic chlamydial species in chickens, with a high ompA intraspecies diversity. The presence of viable C. psittaci and C. gallinacea demonstrated by isolation from chickens in backyard farms poses a potential public health problem.

Activity of synthetic peptides against Chlamydia.

The in vitro activity of six synthetic peptides against 36 strains of Chlamydia from different origins was investigated. Clavanin MO (CMO) proved to be the most active peptide, reducing the inclusion number of all Chlamydia strains from eight different species tested by ≥50% at 10 µg mL-1 . Mastoparan L showed an equal activity against C. trachomatis, C. pneumoniae, C. suis, and C. muridarum, but did not exert any inhibitory effect against C. psittaci, C. pecorum, C. abortus, and C. avium even at 80 µg mL-1 . These data suggest that CMO could be a promising compound in the prevention and treatment of chlamydial infections.