Last Friday Jarne van Hattem presented findings on ESBL carriage in Dutch travelers returning from ESBL-rich countries at our NCOH meeting and the next day the results appeared in Lancet ID. A great study; quantifying things we already thought, extending our knowledge on risk factors and providing new information on the public health aspects of these imported bacteria. They concluded that acquistion and spread are “substantial and worrisome”. Too bad: all the quantified knowledge lost in 2 meaningless words.
In short, they studied 2001 travelers (ESBL carriage before travel 6.1%) and 34.3% of the non-carriers acquired ESBL during travel; especially in southern Asia (75.1%). Risk fators for acquisition: persisting diarrhea, ciprofloxacin use and eating street food. The median duration of carriage after return was 30 days and 11.3% was still colonized ater 1 year. This implies that returning travelers (depending on region) must be considered at risk for ESBL-carriage (no matter whether they have additonal risk factors) during a certain period of time. Yet, median duration of carriage is short and after 1 year that risk is fairly close to the ESBL-prevalence in the Dutch population.
Is this carriage a health risk for travelers? With >500,000 Dutch travelers to ESBL high-endemicity regions per year, many will acquire (according to what we can detect) ESBL, but how many will develop infections caused by these ESBL-producing bugs? That now is a burning question.
Is this import of ESBL a risk for the Dutch public, that we intend to protect against infections caused by AMR? They also investigated the occurrence of within-household transmission of these bacteria in 215 non-travelling household members and quantified rates with a Markov model. The figure that got most attention was the “12% probability of transmitting ESBL-E to another household member”. Yet, much more informative is the actual transmission rate from which one can derive the effective R0. This rate was 0,0013/carriage day and the calculated effective R0 was around 0.2 (Martin Bootsma personal communication), which might include some overestimation due to false-positive transmission events (no molecular typing). An R0 of 0.2 seems not enough to cause continued transmission – leading to endemicity – coming from these sources, especially since transmission to the next ring (to non-household members) will be less effective. Simply said: returning travelers their household members seem to be – in the Netherlands – dead-end roads for ESBL-producing bacteria. That could be expressed as reassuring.
*Title stolen from Gary Brooker