An Explanation of the News about High Detection of Antimicrobial Resistant Bacteria from Chicken Meat
‘Antibiotic-resistant bacteria were detected in a half sample of chicken meat as reported by the Ministry of Health Labor and Welfare Research Group ’ was featured in the Nikkei newspaper on March 31, 2018. I’d like to explain about this press because it seems to include expressions with insufficient explanations which can become misleading.
Extended-spectrum β-lactamase (ESBL) producing bacteria as being is one of the antimicrobial resistant bacteria. Cephalosporin antibiotics which are often prescribed for a common cold, although they are not always effective, are divided into β-lactam antibiotics and are mostly used in Japan. Cephalosporin-resistant bacteria produce β-lactamase which decomposes β-lactam antibiotics. ESBL is the strongest β-lactamase, thus, bacteria producing ESBL will have abilities to decompose not only all types of cephalosporin antibiotics but also new developing ones in the future. That is why doctors have been monitoring them carefully.
This report said that antimicrobial resistant bacteria including ESBL producing bacteria were isolated from 49% of all examined chicken meat (59% of domestically grown chicken meat and 34% of imported chicken meat) from 2015 to 2017. In another report, they were detected in 77% of domestically grown and 52% of imported chicken meat.
The newspaper had reported that antimicrobial resistant bacteria were frequently isolated from chicken meat due to the excessive use of antibiotics for broiler, which led to the increase of ESBL producing bacteria. I wonder if that logic is correct.
In Japanese Veterinary Antimicrobial Resistance Monitoring System; JVARM, cephalosporin-resistant Escherichia coli, which was suspected to be ESBL producing bacteria, was isolated from 4.6% of chicken feces in 2013, while it decreased to 2.7% in 2015. These resistant rates had increased up to 20% owing to the improper use of cephalosporin antibiotics for broiler in Japan. However, ESBL producing bacteria in Escherichia coli, which were isolated from healthy chicken’s feces have not been detected much in recent years as mentioned above. Thus, there is a significant deviation of detected data between chicken meat and feces.
It is suspected that possible contamination occurred during the transport of the meat from farms to retail stores, in the meat processing, and especially in the cooling system with the presence of the chiller water. This process is performed after evisceration, and intestines can be sometimes injured by automatic cutting during evisceration. If intestines having ESBL producing bacteria are injured, these bacteria can expand in chiller water and contaminate the surface of the chicken meat. Actually, 200ppm sodium hypochlorite is added to the chiller water to annihilate bacteria. However, once the disinfection liquid is contaminated with organic matter like feces, the effect of disinfection liquid might deteriorate. That is how those bacteria are considered to contaminate the surface of chicken meat frequently.
How about the risk for humans eating chicken meat contaminated with ESBL producing bacteria? One report said that they were detected in about 2 % of feces from healthy humans, and the other report said detected rate had increased to 15.6% of their feces by several examinations to get accuracy. The ratio of these bacteria carrier in sick people is higher than it is in healthy people. Moreover, it was also reported that detected ESBL genotypes were different between humans and livestock animals (or meat). Thus, the risk for healthy people seems to be extremely low even if they eat chicken meat contaminated with a few numbers of these bacteria. For aged or sick people, however, we recommend cooking with heat. By the way, the national food-related antimicrobial resistance monitoring system is not established in Japan. If the monitoring had been performed in this case, temporal changes of the resistant bacteria-isolation rate could be detected early and optimum responses might be performed. Given that such systems are already established in the other developed county, the earlier setting of it is hoped in Japan.