Strategic measures for the control of surging antimicrobial resistance in Hong Kong and mainland of China

Cheng, Vincent CC; Wong, Sally CY; Ho, Pak-Leung; Yuen, Kwok-Yung

The presence of MDROs in food animals and food items should alert the general public to comply with good hand hygiene practices and to avoid eating raw and undercooked foods, especially while receiving antimicrobial therapy. Antibiotic resistance in animals may be transferred to humans from direct contact with animals, contaminated food and water, and also through indirect contact with contaminated environment. Given the abundance of antimicrobialresistant E. coli in food animals and meat products, it would be informative to assess the risk of human exposure. In a summer camp outbreak of foodborne Salmonella gastroenteritis, two multi-resistant E. coli strains were found along with S. enterica in nine of the 22 investigated individuals, 84 raising the possibility that contaminated food or water were the vehicles for simultaneous dissemination of Salmonella and resistant E. coli to the campers. Investigators from Spain evaluated this possibility further by investigating stool samples from 905 people involved in another 132 episodes of acute gastroenteritis outbreaks and from 226 outbreak-related food handlers from 2003-2004. In 31 of the 132 outbreaks, one or more of the investigated subjects carried one or more ESBL-producing bacteria. In 10 outbreaks, two or more diners were found to share the same ESBL-producing bacteria, and in four of them, the strain was identical to the bacteria isolated from the food handlers. 85 Using a mathematical model, Depoorter et al. 86 assessed the risk of human exposure to antimicrobial-resistant E. coli through consumption of broiler meat in Belgium, and 35% of the E. coli strains isolated from live broilers were resistant to third-generation cephalosporins. Using baseline data estimates, the probability of exposure to 1000 CFUs or more of resistant E. coli during consumption of a meal containing chicken meat was calculated to be 1.5%. The risk is mainly attributed to cross-contamination in the kitchen rather than undercooking. Given the much higher frequency of ESBL-producing Enterobacteriaceae in the live poultry in Hong Kong, this model predicted that the chance of consuming resistant bacteria in a serving of broiler meat could be as high as 4.3%-9.3% at exposure levels of 10-100 CFUs. In a recent study in Scandinavia, 21% (90/430) of the returning travelers had fecal colonization by ESBL-producing Enterobacteriaceae. The risk was higher among those who had travelled to South Asia and were taking antimicrobials. 87 In theory, ingestion of plasmids or DNA fragments containing the resistance determinants might also pose a risk because the human microbiota may acquire the resistance genes by transformation. However, the risk of resistance emerging from this route of exposure seems to be exceedingly low, at least for members of the gut microbiota that are not naturally competent to free DNA, such as E. coli and Klebsiella spp. In an animal model using Acinetobacter baylyi, which is competent to free DNA, extensive ingestion of plasmid DNA (100 mg per day) encoding resistance genes did not produce antibiotic-resistant transformants among the aerobic microbiota (detection limit ,1 transformants per 1.1310 8 cultured bacteria). 88 The content within the rodent gastrointestinal tract may have shielded or adsorbed the plasmid DNA, preventing exposure of food-derived DNA fragments to competent bacteria. 89 The observed lack of DNA uptake by gut bacteria might also be related to the lack of expression of bacter