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Questions and Answers
What is the purpose of publishing an annual antibiogram according to CLSI recommendations?
What is the purpose of publishing an annual antibiogram according to CLSI recommendations?
Which of the following microorganisms can be recovered through appropriate culture methods mentioned in the content?
Which of the following microorganisms can be recovered through appropriate culture methods mentioned in the content?
Which treatment enhances the observation of yeasts and molds in specimens?
Which treatment enhances the observation of yeasts and molds in specimens?
In which situation is empiric therapy particularly significant?
In which situation is empiric therapy particularly significant?
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Which condition is commonly associated with yeast or fungus infections?
Which condition is commonly associated with yeast or fungus infections?
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What is the primary purpose of designing PCR primers in the context of microbial identification?
What is the primary purpose of designing PCR primers in the context of microbial identification?
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Which gene is most commonly used for bacterial identification due to its conserved regions?
Which gene is most commonly used for bacterial identification due to its conserved regions?
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What technique does MALDI-TOF MS employ to facilitate mass spectrometry analysis?
What technique does MALDI-TOF MS employ to facilitate mass spectrometry analysis?
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In the context of mass spectrometry, what primarily characterizes the charged particles created by ionization?
In the context of mass spectrometry, what primarily characterizes the charged particles created by ionization?
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What role does PCR-sequencing have in virology, according to the content?
What role does PCR-sequencing have in virology, according to the content?
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Which of the following describes the application of MassTag PCR?
Which of the following describes the application of MassTag PCR?
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Which of the following is not identified as a conserved gene target for bacterial identification?
Which of the following is not identified as a conserved gene target for bacterial identification?
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What is a key advantage of using the 16S rRNA gene for distinguishing bacterial species?
What is a key advantage of using the 16S rRNA gene for distinguishing bacterial species?
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Which bacteria is characterized as coagulase-positive and usually β-hemolytic?
Which bacteria is characterized as coagulase-positive and usually β-hemolytic?
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In a clinical context, which testing method is more sensitive than culture for identifying specific infections?
In a clinical context, which testing method is more sensitive than culture for identifying specific infections?
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What kind of flora is typically associated with mixed anaerobic and aerobic bacteria?
What kind of flora is typically associated with mixed anaerobic and aerobic bacteria?
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What type of white blood cells are indicated in infections caused by trachomatis in the absence of associated organisms?
What type of white blood cells are indicated in infections caused by trachomatis in the absence of associated organisms?
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Which of the following is NOT typically associated with Gram-negative diplococci?
Which of the following is NOT typically associated with Gram-negative diplococci?
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Which type of organisms are often strongly suspected as the cause of pneumonia due to their unusual presence in sputum?
Which type of organisms are often strongly suspected as the cause of pneumonia due to their unusual presence in sputum?
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In what type of infections does the source of infection play a significant role in creating a susceptibility test battery?
In what type of infections does the source of infection play a significant role in creating a susceptibility test battery?
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What does the Clinical and Laboratory Standards Institute (CLSI) provide recommendations for?
What does the Clinical and Laboratory Standards Institute (CLSI) provide recommendations for?
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What is the proper way to report common organisms found in abdominal abscesses?
What is the proper way to report common organisms found in abdominal abscesses?
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Which statement about zone sizes of growth inhibition is accurate?
Which statement about zone sizes of growth inhibition is accurate?
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What should be done with yeasts present in small numbers within a specimen?
What should be done with yeasts present in small numbers within a specimen?
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Why should other fungi not normally present in a specimen be reported?
Why should other fungi not normally present in a specimen be reported?
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What is necessary to compare the zone sizes of different drugs acting on the same organism?
What is necessary to compare the zone sizes of different drugs acting on the same organism?
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Which specimen is typically used for diagnosing Enteric fever caused by Salmonella serovar Typhi?
Which specimen is typically used for diagnosing Enteric fever caused by Salmonella serovar Typhi?
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What type of flora is predominantly found in anaerobic and aerobic bowel abscesses?
What type of flora is predominantly found in anaerobic and aerobic bowel abscesses?
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On which agar is Vibrio cholerae specifically cultured when there is a clinical suspicion?
On which agar is Vibrio cholerae specifically cultured when there is a clinical suspicion?
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What is the expected colony morphology of Campylobacter jejuni on a smear?
What is the expected colony morphology of Campylobacter jejuni on a smear?
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Which of the following statements is true regarding Shigella species?
Which of the following statements is true regarding Shigella species?
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Which type of specimen is recommended for culturing Campylobacter species?
Which type of specimen is recommended for culturing Campylobacter species?
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In diagnosing cholecystitis, which of the following is typically found in the culture?
In diagnosing cholecystitis, which of the following is typically found in the culture?
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What is a distinguishing characteristic of non-lactose fermenting colonies on MAC/EMB agar?
What is a distinguishing characteristic of non-lactose fermenting colonies on MAC/EMB agar?
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What is the gram stain appearance of Bacteroides fragilis?
What is the gram stain appearance of Bacteroides fragilis?
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What is a common laboratory method used to identify Salmonella species in stool samples?
What is a common laboratory method used to identify Salmonella species in stool samples?
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Study Notes
Bacterial Characteristics and Culture
- Gram-negative rods: Primarily associated with enteric infections and gastrointestinal flora, indicative of potential pathogens.
- Bacteroides fragilis: Notable for being a Gram-negative anaerobe typically found in mixed flora; significant in infections involving anaerobic bacteria.
- Entamoeba histolytica: Considered in cases of mixed aerobic and anaerobic infections.
Clinical Conditions and Specimen Collection
- Cholecystitis: Key specimens include bile; culture on BA, CA, and MAC/EMB needed for anaerobic and aerobic Gram-negative isolation, including B. fragilis.
- Abdominal or perirectal abscess: Fluid sample reveals mixed flora; usually involves both aerobic and anaerobic bowel flora with more than five species often present.
- Enteric fever (Typhoid): Blood, stool, or urine specimens cultured on BA, CA, MAC/EMB, and Hektoen to identify Salmonella serovar Typhi. Culturing multiple specimens is critical due to lactose-negative, H2S-positive characteristics.
Enteritis and Diarrheal Illnesses
- Enteritis and bacterial diarrheas: Stool specimens assessed on MAC/EMB, Hektoen, and enteric agar.
- Salmonella species: Identifiable through non-lactose fermenting colonies on TSI slants, producing gas and acid; prevalent in gastroenteritis cases.
- Shigella species: Similar identification through TSI, characterized by an alkaline slant, acid butt without gas or H2S.
- Campylobacter jejuni: Requires incubation at 42°C; identification of “gull wing–shaped” Gram-negative rods and oxidase-positive colonies.
Vibrio cholerae Detection
- Thiosulfate-citrate-bile salts-sucrose (TCBS) agar: Important for identifying Vibrio cholerae in clinically suspected cases, which appear as yellow colonies.
Arthritis Testing
- Synovial fluid culture: Typically tested on BA or CA for Staphylococcus aureus, identifiable as Gram-positive cocci in clusters.
Molecular Methods in Microbial Identification
- 16S rRNA gene sequencing: Commonly used for bacterial identification due to its conserved regions interspersed with variable sequences.
- Mass spectrometry: Utilized for protein or DNA analysis; advanced techniques, including MALDI-TOF MS, revolutionize microbial identification processes.
Additional Bacterial Identification Techniques
- PCR-sequencing: Enables strain typing and detection of resistance mutations in viruses.
- Multi-target PCR: Incorporates mass tags for easier identification during mass spectrometry analysis.
Antimicrobial Susceptibility Testing
- Susceptibility patterns: Identified based on the type of infection and microbiota present; recommended practices by the Clinical and Laboratory Standards Institute (CLSI).
- Antibiotic zone sizes: Vary by drug characteristics; crucial for determining effective therapy options.
Fungal and Yeast Infections
- Common fungal species: Includes Candida and Aspergillus; identified microscopically in suspicious areas and culturing practices adjusted for accurate results.
- Enhanced observation techniques: Using KOH and calcofluor white aids in recognizing yeasts and molds effectively.
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Description
This quiz covers the characteristics and classifications of Gram-negative rods, focusing on common enteric bacteria like Escherichia coli and Bacteroides fragilis. Additionally, it explores mixed flora, anaerobes, and possible infections caused by these organisms, including Entamoeba histolytica. Test your microbiology knowledge with this insightful quiz.
