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Van Cuong, N.

Publications and source records attributed to Van Cuong, N..

2 recordsLinked to original sources
bioRxiv2020

Small-scale commercial chicken production: A risky business for farmers in the Mekong Delta of Vietnam

Small-scale farming of meat chicken flocks using local native breeds contributes to the economy of many rural livelihoods in Vietnam and many other low- and middle-income countries (LMICs). These systems are also the target of high levels of antimicrobial use (AMU); however little is known about the profitability and sustainability of such systems. Since small scale farms are commercial enterprises, this knowledge is essential in order to develop successful strategies aimed at curbing excessive AMU. Using longitudinal data from 203 randomly selected small-scale (100-2,000 chickens) native chicken flocks raised in 102 farms in Dong Thap province (Mekong Delta, Vietnam), we investigated the financial and economic parameters of such systems and the main constraints to their sustainability. Feed accounted for the largest financial cost (flock median 49.5% [Inter-quartile range (IQR) 41.5-61.8%]) of total costs, followed by day-old-chicks (DOCs) (median 30.3% [IQR 23.2-38.4%]), non-antimicrobial health-supporting products (median 7.1% [IQR 4.7-10.5%]), vaccines (median 3.1% [IQR 2.2-4.8%]), equipment (median 1.9% [IQR 0.0-4.9%]) and antimicrobials (median 1.9% [IQR 0.7-3.6%]). Excluding labor costs, farmers achieved a positive return on investment (ROI) from 120 (59.1%) flocks, the remainder generated a loss (median ROI 124% [IQR 36-206%]). Higher ROI was associated with higher flock size and low mortality. There was no statistical association between use of medicated feed and flock mortality or chicken bodyweight. The median daily income per person dedicated to raising chickens was 202,100 VND, lower than alternative rural labour activities in the Mekong Delta. In a large proportion of farms (33.4%), farmers decided to stop raising chickens after completing one cycle. Farmers who dropped off chicken production purchased more expensive feed (in 1,000 VND per kg) (11.1 [10.6-11.5] vs. 10.8 [10.4-11.3] for farms that continued production (p=0.039) and experienced higher chicken mortality (28.5% [12.0-79.0%] vs. 16 [7.5-33.0%] (p=0.004). The turnover of farmers raising chickens in such systems represents a challenge in targeting messages on appropriate AMU and on chicken health. In order to ensure sustainability of small-scale commercial systems, advisory services need to be available as farmer initiate new flocks, and support them in the early stages to help overcome their limited experience and skills. This targeted approach would support profitability whilst reducing risk of emergence of AMR and other disease problems from these systems.

microbiology↗
bioRxiv2020

A novel method for measuring phenotypic colistin resistance in Escherichia coli populations from chicken flocks

Colistin is extensively used in animal production in many low- and middle-income countries. There is a need to develop methodologies to benchmark and monitor changes in resistance in commensal bacterial populations in farms. We aimed to evaluate the performance of a broth microdilution method based on culturing a pooled Escherichia coli suspension (30-50 organisms) from each sample. In order to confirm the biological basis and sensitivity of the method, we prepared 16 standard suspensions containing variable ratios of colistin-susceptible and mcr-1 encoded colistin-resistant E. coli which were grown in 2mg/L colistin. The optical density (OD600nm) readings over time were used to generate a growth curve, and were adjusted to the values obtained in the absence of colistin. The median limit of detection of the method was 1 colistin-resistant in 104 susceptible colonies [1st - 3rd quartile, 1:102 - 1:105]. We applied this method to 108 pooled faecal samples from 36 chicken flocks in the Mekong Delta (Vietnam) over the production cycle. The correlation between this method and the prevalence of colistin resistance in individual colonies harvested from field samples, determined by the Minimum Inhibitory Concentration (MIC), was established. The overall prevalence of colistin resistance at sample and isolate level was 38.9% and 19.4%, respectively. Increased colistin resistance was associated with recent (2 weeks) use of colistin and other, non-colistin antimicrobials (OR=3.67 and OR=1.84, respectively). Our method is a sensitive and affordable approach to monitor changes in colistin resistance in pooled E. coli populations from faecal samples over time. IMPORTANCEColistin (polymyxin E) is an antimicrobial with poor solubility properties, and therefore broth microdilution is the only appropriate method for testing colistin resistance. However, estimating colistin resistance in commensal mixed Escherichia coli populations is laborious since it requires individual colony isolation, identification and susceptibility testing. We developed a growth-based microdilution method suitable for pooled faecal samples. We validated the method by comparing it with results from individual MIC testing of 909 E. coli isolates. We used the method to investigate phenotypic colistin resistance in 108 pooled faecal samples from 36 healthy chicken flocks, each sampled three times over the production cycle. A higher level of resistance was seen in flocks recently supplemented with colistin in drinking water, although the observed generated resistance was short-lived. Our method is affordable, and may potentially be integrated into surveillance systems aiming at estimating the prevalence of resistance at colony level in flocks/herds. Furthermore, it may also be adapted to other complex biological systems, such as farms and abattoirs.

microbiology↗