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Exposure to RB51: How to Reduce Risk of Infection

Exposure to RB51 can lead to brucellosis.

When an exposure occurs, determining if the risk is high or low is the first step.

For those at high risk, post-exposure prophylaxis (PEP) is recommended. Those with low risk exposures may also opt to take PEP.

PEP should include:

  • doxycycline (100mg)
  • taken orally, two times a day, for at least 21 days
  • consider addition of other suitable antimicrobials

Those with contraindications to doxycycline may use:

  • trimethoprim-sulfamethoxazole (160 mg/800mg)
  • orally, two times a day, for at least 21 days

Prophylaxis for exposure to Brucella species routinely consists of a combination of doxycycline and rifampin. RB51, however, is resistant to rifampin in vitro, so rifampin is not recommended.

Persons with contraindications to these antimicrobial agents should consult with their health care provider for alternative PEP.

Currently, there is no human serological test available for monitoring RB51 exposure.

Both those with high and low risk exposures should be monitored for the development of symptoms of brucellosis. Routine serologic tests for brucellosis will not be effective in monitoring for infection. Monitoring, from the last exposure, should include:

  • for 4 weeks: temperature should be actively monitored
  • for 6 months: broader symptoms of brucellosis should be passively monitored.

Persons potentially exposed to RB51 who develop symptoms should consult a health care provider.

If brucellosis occurs despite prophylaxis, treatment regimens would need to be selected based on antimicrobial susceptibility results.


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