Symptomatology of Pathogenic Yersiniae

Welcome to another #micromeded! This week, I wanted to talk more about pathogenic Yersiniae. Interestingly, even though they all share a similar virulence plasmid, their epidemiology and symptomatology are very different!

In general, the diseases caused by Yersiniae can be classified as plague, those caused by Y. pestis, or yersiniosis, those cause by Y. enterocolitica or Y. pseudotuberculosis. Interestingly, Y. pseudotuberculosis has a genome that is nearly identical to Y. pestis, but without a few of the virulence plasmids. Yersiniosis usually causes a diarrheal disease with potential to spread through the lymph nodes and cause systemic disease.

Plague, on the other hand, is usually transmitted by infected fleas which inoculate the skin allowing the pathogen to spread to the draining lymph node by hitching a ride with dendritic cells or other white blood cells. From there, the pathogen causes expansion of the immune cells leading to the formation of a bubo (hence, bubonic plague). From there, the pathogen can get into the blood and cause sepsis (septicemic plague) and/or the lungs causing a severe lung infection.

Once in the lung, Y. pestis can be transmitted by air leading to rampant community spread. For these reasons, any case of plague (usually encountered in the Western US or in rural areas—hence, sylvatic cycle) is taken very seriously, so the patient’s conditions do not worsen leading to pneumonic plague and initiating the urban cycle (i.e.: respiratory spread).

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