31. An estimation of total antimicrobial usage in humans and animals in Vietnam
Abstract: The accurate assessment of antimicrobial use (AMU) requires relating quantities of active ingredients (AAIs) with population denominators. These data can be used to prioritize potential sources of selective pressure for antimicrobial resistance and to establish reduction targets. Here, we estimated AMU in Vietnam (human population 93.4 M in 2015), and compared it with European Union (EU) data (population 511.5 M in 2014). We extrapolated AMU data on each key animal species and humans from different published sources to calculate overall AMU (in
tonnes) in Vietnam. We then compared these data with published statistics on AMU in the European Union (EU). A total of 3838 t of antimicrobials were used in Vietnam, of which 2751 (71.7%) corresponded to animal use, and the remainder (1086 t; 28.3%) to human AMU. This equates to 261.7 mg and 247.3 mg per kg of human and animal biomass, compared with 122.0 mg and 151.5 mg in the EU. The greatest quantities of antimicrobials (in decreasing order) were used in pigs (41.7% of total use), humans (28.3%), aquaculture (21.9%) and chickens (4.8%). Combined
AMU in other species accounted for < 1.5%. These results are approximate and highlight the need to conduct targeted surveys to improve country-level estimates of AMU.
32. Carriage of the zoonotic organism Streptococcus suis in chicken flocks in Vietnam
Streptococcus suis infections are an emerging zoonotic agent causing severe disease in humans and a major pig pathogen worldwide. We investigated the colonization of S. suis in healthy chickens in different flocks (n = 59) as well as in‐contact pigs in farms with S. suis‐positive chickens (n = 44) in the Mekong Delta of Vietnam. Streptococcus suis was isolated from 20 (33.9%) chicken flocks and from all pigs investigated. Chicken isolates formed a distinct genotypic cluster compared with pig and human strains, although two chicken isolates (10%) clustered with pig isolates. Chicken isolates had unusually high levels of resistance against tetracycline (100%), clindamycin (100%) and erythromycin (95%); and intermediate resistance against penicillin (35%) and ceftriaxone (15%). Our findings suggest that chickens may potentially represent a source of S. suis infection to in‐contact humans and pigs.
33. New study highlights what non-critically important antimicrobials are likely to be effective against chicken pathogens
A new study carried out by the ViParc team at Oxford University Clinical Research Unit has characterised antimicrobial resistance in chicken pathogens against 12 commonly used antimicrobials in the Mekong Delta of Vietnam. The study, led by Ms. Nguyen Thi Phuong Yen (ViParc laboratory scientist) investigated the antimicrobial susceptibility profiles of 58 pathogenic bacteria collected from diagnostic investigations of diseased chicken flocks in Dong Thap, including Ornithobacterium rhinotracheale (ORT), Gallibacterium anatis, and Avibacterium endocarditidis. Because antimicrobials are extensively used in chicken farms in the area, it is important to decide which antibiotics should be prioritized, whilst avoiding those of critical importance according to the World Health Organization (WHO). In the study the researchers analysed the distribution of susceptibility against 12 commonly used antimicrobials, and established a tentative interpretation of resistance. According to the results, doxycycline would theoretically be effective against A. endocarditidis (88.2% susceptibility and G. anatis infections (94.7% susceptibility) in most cases. A total of 86.4% ORT isolates were susceptible to oxytetracycline. In this study, non-critically important antimicrobials against which chicken pathogens are likely to be susceptible as a basis for treatment guidelines. Since there are not yet standardized international guidelines to determine whether a strain is resistance or not, this study illustrates the challenges in interpreting susceptibility testing results, and the need to establish such guidelines for veterinary pathogens. The full article can be accessed here: https://doi.org/10.3390/antibiotics9080499.
34. The role of animals as a source of antimicrobial resistant nontyphoidal Salmonella causing invasive and non-invasive human disease in Vietnam
Nontyphoidal Salmonella (NTS) are associated with both diarrhea and bacteremia. Antimicrobial resistance (AMR) is common in NTS in low-middle income countries, but the major source(s) of AMR NTS in humans are not known. Here, we aimed to assess the role of animals as a source of AMR in human NTS infections in Vietnam. We retrospectively combined and analyzed 672 NTS human and animal isolates from four studies in southern Vietnam and compared serovars, sequence types (ST), and AMR profiles. We generated a population structure of circulating organisms and aimed to attribute sources of AMR in NTS causing invasive and noninvasive disease in humans using Bayesian multinomial mixture models.
Among 672 NTS isolates, 148 (22%) originated from human blood, 211 (31%) from human stool, and 313 (47%) from animal stool. The distribution of serovars, STs, and AMR profiles differed among sources; serovars Enteritidis, Typhimurium, and Weltevreden were the most common in human blood, human stool, and animals, respectively. We identified an association between the source of NTS and AMR profile; the majority of AMR isolates were isolated from human blood (p < 0.001). Modelling by ST-AMR profile found chickens and pigs were likely the major sources of AMR NTS in human blood and stool, respectively; but unsampled sources were found to be a major contributor.
Antimicrobial use in food animals is hypothesized to play role in the emergence of AMR in human pathogens. Our cross-sectional population-based approach suggests a significant overlap between AMR in NTS in animals and humans, but animal NTS does explain the full extent of AMR in human NTS infections in Vietnam.