Investigations are ongoing but the source has not yet been identified in the outbreak around Conwy and Gwynedd.
Five of the 22 cases were hospitalised but have since been discharged, said Public Health Wales.
The agency is working with Environmental Health Officers from Gwynedd Council and Conwy County Borough Council to investigate the outbreak.
Illnesses have been recorded since 20 July and have been confirmed by laboratory testing as the same unique strain.
Dr Judy Hart, consultant in public health from Public Health Wales said: “Salmonella is usually contracted by eating food like red and white meats, raw eggs, milk and other dairy products which contain the bacterium, usually following cross-contamination of cooked food by raw food or by failing to ensure food is properly stored and cooked before it’s eaten.”
Salmonella cases in the country
Salmonella infection follows contamination of cooked food by raw food or failing to achieve cooking temperatures that are adequate to kill the bacteria. Cases can be prevented by the correct storage and cooking of foods and employing hygienic food handling and preparation procedures.
Rates of salmonella in Wales and the UK have fallen in recent years from a peak of infection recorded in 1997.
An important factor in this falling trend is the compulsory vaccination of the UK egg-laying flock, introduced in 1998, against Salmonella Enteriditis.
In Wales during 2011, the reported rate of salmonella infection in the general population was 15 cases per 100,000 people. This compares to a rate of 15.5 the year before and 80 cases per 100,000 in 1997.