Scientists at the Royal Melbourne Hospital (RMH) and Doherty Institute have used whole genome sequencing to discover that the transmission of tuberculosis (TB) commonly occurs beyond household contacts in Victoria, in social or other settings.

Mycobacterium tuberculosis bacteria microscopy
Mycobacterium tuberculosis

In a recent paper published in The Lancet Regional Health - Western Pacific, scientists at the Mycobacterium Reference Laboratory (MRL) at the Victorian Infectious Disease Reference Laboratory (VIDRL) and Microbiological Diagnostic Unit Public Health Laboratory (MDU PHL) at the Institute worked in conjunction with the Victorian Tuberculosis Program to explore the genetic codes of Mycobacterium tuberculosis (Mtb) in Victoria over a four-year period and found that most tuberculosis cases were acquired outside the household.

Lead author and epidemiologist at the Victorian Tuberculosis Program at the RMH and Doherty institute, Dr Katie Dale, said the findings broaden our understanding of TB transmission.

“Transmission between TB cases and their household contacts is commonly observed, but our understanding of TB transmission would be incomplete if it is only informed by easily observed events between known contacts,” Dr Dale said.

“The advantage of whole genome sequencing is that it can reveal TB transmission between individuals we would never otherwise have linked, so it can give us a better picture of all TB transmission in a low-incidence setting,” Dr Dale said.

“We found that transmission among young adults in social settings was common, but our results also indicated that 41 per cent of local Mycobacterium tuberculosis transmission occurred between individuals with no identified connections.”

Dr Dale hopes the findings will inform tuberculosis management and contact tracing in the future.

“Understanding the relative importance of household versus extra-household transmission emphasises the need for broad contact tracing investigations, and the possible benefit of directing prevention efforts to certain demographic groups.”

Dr Dale and her team plan to establish and evaluate national consensus standards for how the insights gained from whole genome sequencing data can best inform and guide programmatic responses in the future.

Mobile Stroke Unit with Ambulance Victoria paramedic and the RMH Stroke team
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