Pesquisadores from USP and Instituto from Pesca from São Paulo detected the bacteria Citrobacter telavivensis in fresh oysters purchased in markets. The discovery occurred in samples of São Paulo and Santa Catarina. Organização Mundial of Saúde classifies the microorganism as critical priority because of high antibiotic resistance. Nenhuma of the oysters analyzed failed current health inspection tests. The finding marks the first identification of the bacteria in food in the country.
The study was published in August 2025. Ele reinforces the global alert about antimicrobial resistance, listed by the WHO among the ten biggest threats to public health. Oysters act as natural water filters. Therefore, they accumulate what circulates in the marine environment, including bacteria and pollutants.
Descoberta exposes gaps in health surveillance
Citrobacter telavivensis first appeared in an Israeli hospital in 2010. No Brasil was isolated directly from oysters intended for human consumption. The samples also revealed strains of Klebsiella pneumoniae and Escherichia coli resistant to next-generation antibiotics.
Além In addition, 35% of the oysters had arsenic levels above the maximum limit allowed by Anvisa. The researchers observed a co-selection process. Arsênio and antibiotic residues in water favor bacteria tolerant to both. Essa combination transforms the polluted environment into a breeding ground for resistance.
- The oysters were collected from five different markets.
- Nenhuma sample failed current criteria for total microorganisms.
- Current protocols do not include specific resistance profile tests.
- The research analyzed 108 fresh oysters.
- Outros resistant microorganisms were also identified in the same samples.
Ostras function as environmental sentinels
Esses molluscs pump large volumes of water to feed themselves. Eles retain viruses, heavy metals, drug residues and bacteria present in the cultivation site. Essa feature makes them reliable indicators of water quality.
In the case studied, the oysters came from regions with possible influence of pollution. The study did not allow tracking the exact origin of the samples, which limits the precise identification of contaminating sources. Ainda thus, the result points to a larger problem in the marine food chain.
Current Protocolos do not assess bacterial resistance
Sistemas as HACCP and Boas Práticas as Fabricação check temperature, hygiene and specific pathogens as Salmonella and Listeria. Eles does not, however, examine the antimicrobial resistance profile of bacteria. A batch can contain superbugs and still be released if the total number of microorganisms is within limits.
Essa lag occurs because the protocols were created before resistance was consolidated as a threat in food. Agricultura’s Ministério advanced in 2023 with Ação Nacional’s Plano for the agricultural sector. The main focus is on poultry, pigs and cattle. Pescados and molluscs do not yet have equivalent coverage.
Biofilmes increases the complexity of the problem
Bactérias resistance is not limited to raw foods. Elas can colonize equipment, benches and pipes in processing plants. Formam structures called biofilms, which protect colonies and increase resistance to sanitizers and antibiotics by up to a thousand times.
Pesquisas seek biological alternatives to combat these biofilms. An enzyme called lugdulisin, produced by another bacteria, showed the ability to degrade the protective matrix in laboratory tests. The result is still experimental, but it indicates a possible path towards new industrial hygiene strategies.
Especialistas requests urgent update of controls
Três measures appear as priorities according to the authors. Antimicrobial resistance surveillance should include fish. Quality protocols need to incorporate origin traceability and genomic profile testing. Finally, funding for research into biotechnological solutions must grow.
The consumption of antibiotics in aquaculture and livestock accounts for more than 75% of the global volume. Parte of these compounds reaches the sea via sewage and inadequate disposal. Selective pressure favors the spread of superbugs outside the hospital environment.
Risco goes beyond public health
The presence of superbugs in export products can affect international trade. Países like União Europeia and Estados Unidos require rigorous antimicrobial control standards. Falhas in this field threaten the competitiveness of the Brazilian fishing sector.
The study does not recommend avoiding oyster consumption. Ele reinforces, however, the need for adequate cooking and broader prevention measures. Antimicrobial resistance already causes one in six bacterial infections, reducing the effectiveness of treatments, according to recent global data.
The finding in oysters serves as a warning. Ele shows that the threat evolves and reaches consumers’ tables through routes that current inspection does not yet fully cover. Pesquisadores and authorities need to align control instruments with the emerging reality.
