Consumption of edible ice contaminated with Acinetobacter, Pseudomonas, and Stenotrophomonas is a risk factor for fecal colonization with extended-spectrum ß-lactamase-producing Escherichia coli in Vietnam.

Although Vietnamese residents frequently harbor extended-spectrum ß-lactamase-producing Escherichia coli (ESBL-E), it is unclear which foods/beverages are risk factors for acquiring these bacteria. The aim of this study was to evaluate the frequency with which edible ice served in restaurants is contaminated with antibiotic-resistant bacteria, and thereby clarify whether this product poses a risk for ESBL-E carriage in humans. Ice from restaurants in Vietnam and Japan was screened for bacteria capable of growing on agar containing cefotaxime (BG-CTX). Of the 119 BG-CTX strains isolated in Vietnam, 40%, 39%, and 12% were identified as Pseudomonas spp., Acinetobacter spp., and Stenotrophomonas maltophilia, respectively. Meanwhile, of the six such strains isolated in Japan, five were identified as Acinetobacter spp. and one as Pseudomonas spp. More than 10% of the Acinetobacter isolates exhibited cefotaxime, ceftazidime, and sulfa/trimethoprim resistance, while 21% of Pseudomonas and 14% of S. maltophilia isolates exhibited meropenem and sulfa/trimethoprim resistance, respectively. Subsequent multiplex polymerase chain reaction (PCR) analyses detected ESBL-encoding genes in 10% of the BG-CTX. Notably, feces harvested from mice administered water contaminated with BG-CTX contained E. coli harboring the blaCTX-M-9 gene. In conclusion, our findings indicate that consumption of contaminated edible ice is a risk factor for human ESBL-E carriage.

Residues of 2-hydroxy-3-phenylpyrazine, a degradation product of some ß-lactam antibiotics, in environmental water in Vietnam.

Antibiotic-resistant bacteria have become a serious problem worldwide, caused in part by the excessive use and discharge of antibiotics into the environment. Ampicillin (ABPC) is a widely used antibiotic. However, this chemical rapidly decomposes in water containing divalent cations like Ca2+ and Mg2+, thus, detection of ABPC in environmental water is difficult. This study was carried out to evaluate the presence of 2-hydroxy-3-phenylpyrazine (HPP), one of the degradation products of ABPC and ß-lactam antibiotics with an ABPC substructure, in environmental water. An analytical method for HPP monitoring in environmental water was developed using liquid chromatography/tandem mass spectrometry. The analyte was extracted from water samples and enriched using a solid-phase extraction cartridge. The quantification limit was 1 ng L-1. The HPP recovery rates from spiked water samples of 25 and 125 ng L-1 were 84.1 and 86.1%, respectively. The method was then used to determine HPP residue levels in 98 environmental water samples from rivers, household ponds, and aquacultural ponds in Vietnam. HPP residues were detected in 60 samples. The HPP detection rates in rivers and household ponds were 42 and 79%, respectively. HPP was not detected in aquacultural ponds. HPP residue concentrations in the samples ranged from 1.3 to 413.3 ng L-1. The residue levels in rivers flowing through city centres were higher than levels in other sampling locations. The findings of this study suggest that HPP is a promising marker for assessing the discharge of ABPC and ß-lactam antibiotics with an ABPC substructure into the environment around sampling sites.

Water metagenomic analysis reveals low bacterial diversity and the presence of antimicrobial residues and resistance genes in a river containing wastewater from backyard aquacultures in the Mekong Delta, Vietnam.

The environmental pathways for the dissemination of antibiotic resistance have recently received increased attention. Aquatic environments act as reservoirs or sources of antimicrobial-resistant bacteria, antimicrobial residues, and antimicrobial resistance genes (ARGs). Therefore, it is imperative to identify the role of polluted water in the dissemination of antimicrobial resistance. The aim of this study was to evaluate the antimicrobial residues, ARGs, and microbiota in the freshwater systems of the Mekong Delta. We selected 12 freshwater sites from aquacultures and rivers in Can Tho, Vietnam and analyzed them for 45 antimicrobial residues and 8 ARGs by LC/MS/MS and real-time PCR, respectively. A 16S rDNA-based metagenomic analysis was conducted to characterize the water microbiota. Residues of sulfamethoxazole (10/12) and sulfadimidine (7/12) were widely detected, together with the sulfa-resistance genes sul1 (11/12) and sul2 (9/12). Additionally, sulfamethoxazole residues and the ß-lactamase-resistance gene blaCTX-M-1 were detected in eight freshwater systems (8/12), suggesting that these freshwater systems may have been polluted by human activity. The metagenomic analysis showed that all the tested freshwater systems contained the phyla Proteobacteria, Actinobacteria, and Bacteroidetes, representing 64% of the total microbiota. Moreover, the Cai Rang River site (Ri-E), which is located at the merge point of wastewaters from backyard-based aquacultures, contained the genera Polynucleobacter, Variovorax, and Limnohabitans, representing more than 78.4% of the total microbiota. Bacterial diversity analysis showed that the Ri-E exhibited the lowest diversity compared with other regions. Principal coordinate analysis showed that the differences among water microbiotas in backyard-based aquacultures could be explained by the farmers' aquaculture techniques. In conclusion, this study demonstrated a collapse of bacterial diversity at the merge point of wastewaters from backyard-based aquacultures in the Mekong Delta.

Frequent use of colistin-based drug treatment to eliminate extended-spectrum beta-lactamase-producing Escherichia coli in backyard chicken farms in Thai Binh Province, Vietnam.

Reports of livestock infections with extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-E) are increasing. Based on interviews conducted over a 6-month period, we found that veterinarians in the Vietnamese province of Thai Binh prefer to prescribe colistin-based drugs (CBD) in chicken farms. We aimed to clarify whether CBD use selects for strains of colistin-resistant ESBL-E. With the cooperation of seven local households, we detected ESBL-E in chickens' feces after treating chickens with CBD. Phylogenetic groupings and the presence of CTX-M/AmpC genes were determined, and the multi-antibiotic susceptibility of isolates was analyzed. Our results showed that ESBL-E presented in seven chickens' feces from two households. Seventy-two percent of ESBL-E isolates harbored CTX-M9 and the phylogenetic group A; the colistin minimum inhibitory concentration (MIC) of all isolated ESBL-E ranged from 0.064 to 1 µg mL-1. Moreover, ESBL-E isolates were used to experimentally select for colistin resistance, and the effect of commercial CBD on ESBL-E was investigated. The results showed that an ESBL-E strain with a colistin MIC of 4 µg mL-1 was able to grow in media with CBD. Although CBD treatment was effective, in vitro experiments demonstrated that ESBL-E can easily acquire colistin resistance. Therefore, restrictions on colistin use are necessary to prevent the emergence of colistin-resistant bacteria.