A multistate outbreak of Salmonella Typhimurium infections has been linked to various clinical, commercial and teaching microbiology laboratories.
A total of 24 people infected with the outbreak strain were reported from 16 states and six were hospitalised.
California, Colorado, Florida, Georgia, Iowa, Maine, Michigan, Missouri, North Carolina, New Hampshire, New Jersey, New Mexico, New York, Oklahoma, Texas and Washington are affected.
CDC: Outbreak is a reminder
CDC said non-pathogenic or attenuated bacterial strains should be used when possible, especially in teaching labs.
The outbreak is a reminder that bacteria used in microbiology laboratories can sicken workers, added the agency.
Illness dates range from March 17 to June 22. Ill people are aged from less than one to 57 years, with a median of 24. Seventy-five percent were female.
Nine (69%) of 13 ill people interviewed had laboratory exposures. Ill people reported behaviours while working in the laboratory that could increase the risk of Salmonella infection.
These included not wearing gloves or lab coats, not washing hands and using the same writing utensils and notebooks outside of the lab.
WGS showed the strain of S. Typhimurium causing illness is closely related genetically to a strain from 2014 and one in 2011 - both of which were linked to microbiology labs.
A total of 41 people were infected in the 2014 outbreak and 109 illnesses were recorded in 2011 with twelve hospitalizations and one death.
After that outbreak, lab professionals developed guidelines for handling microorganisms safely in a teaching lab.
Guidelines for safely handling microbes at biosafety level 1 (BSL1) and biosafety level 2 (BSL2) were created.
They are divided into personal protection requirements, lab physical space requirements, stock culture requirements, standard laboratory practices, training practices and document practices.
CDC infection and Dutch employee exposed
CDC investigated last year how one of its lab workers diagnosed with Salmonella may have acquired the infection due to work in a BSL-2 laboratory.
Lab tests indicated the worker was infected with a strain of Salmonella which matched that being worked on in the lab. The worker returned to the CDC and no other staff were exposed.
The infected person was following standard protocols to perform a basic procedure on a frozen sample to culture the bacteria.
RIVM reported earlier this year that an employee of a Dutch vaccine manufacturer, who was infected with the polio virus in early April, is no longer carrying it.
No other people were infected and the employee can no longer infect others.
The employee was vaccinated so he could not develop the paralytic illness caused by the polio virus but as he did carry the virus and could have spread it through faeces he was isolated at home.
In the Netherlands, children from the age of two months are vaccinated against polio.