11. When samples are sent to a lab for testing, the ____________step is the last step in the process that tells us Salmonella is present

Question

11. When samples are sent to a lab for testing, the ____________step is the last step in the process that tells us Salmonella is present

BlackTom AI · Accepted Answer

Confirmatory testing is the final step in the laboratory process that proves Salmonella is present.

Relevant knowledge points and concepts:
- Microbiological detection follows a staged workflow: sample receipt → pre-enrichment → selective enrichment → selective/differential plating → presumptive (screening) identification → confirmatory testing.
- Presumptive tests indicate possible Salmonella based on colony appearance or general biochemical reactions; confirmatory tests provide definitive identification using specific biochemical reactions, serotyping, or molecular assays (e.g., PCR, MALDI-TOF).
- Regulatory methods (e.g., FDA Bacteriological Analytical Manual, ISO methods) require confirmatory testing before reporting a positive Salmonella result.

Complete step-by-step reasoning:
1. Sample arrival and pre-enrichment: damaged or stressed cells are resuscitated in non-selective media (e.g., buffered peptone water).
2. Selective enrichment: media that favor Salmonella (e.g., Rappaport-Vassiliadis, selenite) increase Salmonella relative to other flora.
3. Selective/differential plating: plates such as XLD or Hektoen enteric allow isolation of suspect Salmonella colonies based on characteristic appearance.
4. Presumptive/screening tests: colonies are screened with simple biochemical tests or agglutination; results suggest but do not prove Salmonella.
5. Confirmatory testing (final step): isolates undergo definitive identification—complete biochemical panels (TSI, LIA, urease, etc.), serological O and H antigen typing, or species-specific PCR/MALDI-TOF. These tests discriminate Salmonella from look-alike organisms and meet regulatory confirmation requirements.

Why the correct answer is correct:
- Only the confirmatory step provides definitive evidence that the organism isolated is Salmonella, converting a presumptive positive into a confirmed positive suitable for reporting or regulatory action.

Why other steps are not correct:
- Pre-enrichment, selective enrichment, plating, and presumptive/screening steps are earlier stages that produce candidates or indications but do not definitively establish species identity.

Conclusion:
The final, definitive laboratory step that tells us Salmonella is present is the confirmatory step—answer C (Confirmatory).

11. When samples are sent to a lab for testing, the ____________step is the last step in the process that tells us Salmonella is present单项选择题

类似问题

True/False: Carrot juice (pH ~6) would be shelf-stable after HPP treatment as this is an effective way to inactivate spores that may be present in the juice.

True or False: Listeria monocytogenes is often associated with outbreaks involving frozen foods because it multiplies in frozen foods.

True or False: All shelf-stable foods are commercially sterile.

Which of the following specimen types is likely to have the LEAST amount of bacterial contamination with oral flora?

How was Peanut Corporation of America able to issue a “negative for Salmonella” certificate of analysis?

Multiple Choice: Which of the following characteristics are common to Shigella spp. and Salmonella enterica serovar Typhi?

Multiple Choice: Which of the following is true with regards to biofilms?

Which bacteria are present in yoghurt?

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单