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7. CONCLUSIONS

 

  1. Some of the hot meals exceeded the microbiological standards accepted by the AEA for E. coli (8.2%), S. aureus (0.6%), B. cereus (0.7%) and for C. perfringens (0.7%). Total counts higher than 10 6 cfu/g, which is the AEA limit for food items that have been handled after heat treatment, were found in 9.2% of hot meal samples. Total counts above this limit indicates shortcomings in food preparing practice. Although the frequency of food poisoning bacteria was rather low, their occurrence may indicate a risk of food poisoning via hot aircraft meals. However, hot meals undergo final re-heating on board, which decreases the microbial count of hot meals and thus the risk of food poisoning. There were significant differences between preparing countries regarding the microbiological quality of hot meals reflecting the level of production hygiene.
  2. Many of the cold meals failed to meet the AEA standard for E. coli (14%), S. aureus (7%) and for B. cereus (3%). The contamination rate in respect of these bacteria was higher in cold meals than in hot meals. Such a high level as the 10 6 cfu/g for E. coli found indicated poor microbiological quality of meals. The maximum levels of S. aureus and B. cereus found, 10 3 cfu/g and 10 4 cfu/g, respectively, mean shortcomings in microbiological quality and indicate a risk of food poisoning. In the case of cold meals, the level of hygiene of the preparing country seemed to reflect to the microbiological quality of the meals, too. Stricter control measures should be focused particularly on the production of cold aircraft meals, which seemed to be even riskier than the hot ones.
  3. The prevalence of Salmonella was low in cold meals (0.1%), but the only positive finding detected was connected with an outbreak among air passengers. The prevalence of Salmonella in hot meals was higher (0.3%). However, none of them were reported to be connected with outbreaks. If final re-heating on board is properly carried out, it should destroy Salmonella contamination. This means a higher risk of Salmonella associated with cold served dishes than with hot served ones.
  4. Nintyone airline passengers and 107 railway passengers became infected with S . Infantis via food prepared in a flight kitchen. A high number of the flight catering employees 28/162 (17%), also became infected via breakfast prepared in the flight kitchen and served in their canteen. This figure included many 23/118 (19%) of the catering establishment’s food handlers. It was impossible to establish the origin of this Salmonella outbreak. The employees’ breakfast had probably been contaminated by a symptom-free S. Infantis carrier in the flight kitchen. Many of the food handlers became infected and this subsequently led to widespread contamination of food products of the flight kitchen. Air passengers became infected via contaminated meals served on a charter flight and railway passengers via contaminated egg sandwiches served on several train routes. S . Infantis was isolated from one hot meal sample representing the batch served on the particular charter flight. The most prominent contributing factors were found to be that food handlers suffering from mild diarrhoea were not excluded from work and that there was no hygiene education or supervision for food handlers. A heat wave combined with a shortage of refrigeration facilities and possible malfunction of the re-heating oven on board were regarded as contributing factors, too. The results of the investigation showed that preparing meals for aircraft is a high-risk operation, which calls for strict hygiene requirements and a thorough knowledge of food hygiene.

  5. Hand and nasal sampling showed a substantial prevalence, 6% and 12% respectively, of the carriage of enterotoxic S. aureus among flight catering food handlers. Nasal carriers can easily transmit S. aureus into the hands and this means a potential risk of food poisoning. Because S. aureus colonises primarily in the human nose, nasal sampling is a better way of detecting S. aureus carriers than hand sampling. Testing food handlers working in high-risk premises such as in flight catering provides valuable information about carriers. It helps in planning preventive measures, such as special hygiene instructions for carriers to avoid contamination of food. Characterisation of isolated strains by pulsed-field gel electrophoresis is very useful especially by tracing the contamination source. It also revealed that more than one clone can be harboured by one employee.

 


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