Vaccines a Valuable Tool in Fight Against Antibiotic Resistance

Typhoid and other invasive salmonelloses are becoming more difficult to treat. Researchers like Sabin partner Dr. Samuel Kariuki keep looking for answers.

In the new supplement from the Sabin-led Coalition Against Typhoid (CaT) on Open Forum Infectious Diseases, research from the 12th International Conference on Typhoid and Other Invasive Salmonelloses shows progress in diagnostics and vaccine development for some of the life-threatening diseases caused by salmonella bacteria.

Increasing antibiotic resistance, however, is causing new concern, including for nontyphoidal salmonella (NTS), one of the most common causes of diarrhea globally. With no vaccine available yet for NTS, health advocates note the critical importance of water, sanitation, and hygiene (WASH) solutions as vaccines and treatments continue to be developed. Here, Dr. Samuel M. Kariuki, director of research and development at the Kenya Medical Research Institute and honorary faculty at the Wellcome Sanger Institute, gives an update on the NTS research he presented at the conference.

Please summarize any updates or new information on nontyphoidal salmonella since you presented at the “Nontyphoidal Salmonella Invasive Disease: Challenges and Solutions” session during the International Conference on Typhoid and Other Invasive Salmonelloses?

We recently showed that children who carry invasive strains of multidrug-resistant Nontyphoidal Salmonella without showing symptoms can shed the bacteria in their stool intermittently for up to 4 months. The follow-up part of this carriage study is still ongoing, but what this tells us is the potential for carriers in the population to act as reservoirs and sources of transmission of this pathogen to vulnerable children who may be malnourished/with HIV or have other concomitant immune-suppressive conditions.

How is the increase in antimicrobial resistance (AMR) a continuing challenge in combating nontyphoidal Salmonella?

The increase in prevalence of AMR in our settings is a real challenge to management of NTS and other severe infections. We are faced with a situation where we have literally no options available for treatment as the more effective alternatives (such as fourth generation cephalosporins) are unaffordable and often not commonly available.

“The best option in the face of the severity of disease caused by invasive NTS and with so many drugs becoming ineffective due to resistance is use of vaccines for prevention and control.”

Dr. Samuel Kariuki

Director, Research and Development

Kenya Medical Research Institute

What solutions are you focused on and how do you hope they will help?

We are currently focused on understanding the long-term carriage dynamics of multi-drug resistant NTS in young children in endemic settings, and how this carriage will inform vaccine coverage when the vaccines are rolled out. In addition, we are using whole genome sequencing to understand changes/evolution over time for the pathogen as this will determine the stability and effectiveness over time for vaccine candidates that are being developed.

Please give your (brief) perspective on the short- and long-term future for combatting nontyphoidal salmonella. 

The best option in the face of the severity of disease caused by invasive NTS and with so many drugs becoming ineffective due to resistance is use of vaccines for prevention and control. We hope that the several efforts that are ongoing in the search for effective vaccines for NTS will bear fruit and that these will be trialed and available for use immediately in NTS endemic settings. It will be important also to ensure that the search for more effective treatments (such as novel antimicrobials, bacteriophages) continues. Vaccines, though effective in prevention and control, have limitations in proportions of population coverage and treatment may still be required for some cases of severe disease.


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