Microbiology Streptococci & Enterococci Quiz

Questions and Answers

What is true about Streptococci and Enterococci?

They occur in clusters

They lack the enzyme catalase (correct)

They are motile

They are anaerobes

What is Beta Hemolysis?

Complete lysis of RBCs around a colony, resulting in a clear zone surrounding the colonies.

What is Alpha Hemolysis?

Partial breakdown of the hemoglobin inside RBCs, producing a green discoloration around the colonies.

Define Gamma Hemolysis.

No hemolysis of blood; no effect on RBCs. Signup and view all the answers

What is the significance of Group A Streptococci?

serious human pathogen, primarily found in the pharynx, causes multiple infections. Signup and view all the answers

What infections are associated with Group B Streptococci?

Neonatal infection like sepsis and meningitis, as well as access, endocarditis, septicemia. Signup and view all the answers

What are the characteristics of Alpha Hemolytic Group: Streptococcus pneumoniae?

Does not possess a Lancefield antigen and is causative agent of pneumonia. Signup and view all the answers

What is the function of the CAMP test?

It helps identify Streptococcus agalactiae. Signup and view all the answers

What distinguishes humans as carriers of Staphylococci and Streptococci?

Staphylococci occur in clusters and are catalase positive; Streptococci occur in chains and are catalase negative. Signup and view all the answers

What is the appearance difference between S.agalactiae and S.pyrogenes on blood agar?

S.agalactiae colonies are large with a narrow zone of beta hemolysis; S.pyrogenes have small colonies with a large zone of beta hemolysis. Signup and view all the answers

What streptococcal species is investigated in third trimester pregnant women?

S.agalactiae (group B strep). Signup and view all the answers

Which streptococci are implicated in dental caries?

Viridans streptococci, such as S.mutans. Signup and view all the answers

Study Notes

Streptococci & Enterococci Overview

Streptococci and enterococci are primarily found in chains and are Gram-positive bacteria.
They are facultative anaerobes, nonmotile, and lack catalase.

Hemolysis Types

Beta Hemolysis: Complete lysis of red blood cells (RBCs) creates a clear zone around colonies.
Alpha Hemolysis: Partial breakdown of hemoglobin in RBCs results in a green discoloration around colonies.
Gamma Hemolysis: No hemolysis occurs, with no effect on RBCs.

Beta Hemolytic Groups

Group A Streptococci (S. pyrogenes): Most serious, primarily found in the pharynx, skin, and rectum; produces hemolysins causing complete lysis of RBCs.
Group B Streptococci (S. agalactiae): Common in the genital and intestinal tracts; significant neonatal infections including sepsis and meningitis. Identified by positive CAMP reaction.
Group C Streptococci (S. dysgalactiae): Uncommon pathogens; involved in pharyngitis and endocarditis, differentiated by Bacitracin resistance and negative CAMP test.

Alpha Hemolytic Groups

Streptococcus pneumoniae: Causes bacterial pneumonia, meningitis, and otitis media; virulent strains have a polysaccharide capsule and are positive for optochin susceptibility.
Viridans Streptococci: Opportunistic infections, associated with dental caries; appear small and grayish on blood agar, with negative bile esculin and variable salt tolerance test results.

Enterococci Groups

Group D Enterococci (E. faecalis and E. faecium): Inhabit the GI tract and oral cavity; can cause urinary tract infections, bacteremia, and endocarditis. Show large non-hemolytic colonies.
Group D Nonenterococci (S. bovis): Present in the intestinal tract; associated with GI malignancies and can cause endocarditis.

Sensitivity Tests

Optochin Sensitivity: Pneumococci are sensitive; viridans are resistant.
Bacitracin Sensitivity: S. pyrogenes is sensitive, while S. agalactiae is resistant.
SXT Sensitivity: Useful for identifying group C streptococci.

Identification Tests

CAMP Test: Positive for S. agalactiae, indicating enhanced breakdown of RBCs.
Lancefield Antigen Testing: Differentiates between streptococcal groups based on carbohydrate antigens.
NaCl Tolerance Test: Distinguishes enterococci from other group D streptococci.
SXT Test: Group A strep is resistant, while group C is sensitive.

Clinical Applications

Throat Swab on Blood Agar: Stabbing creates anaerobic conditions, improving hemolysis development.
Pregnant Women Screening: Focus on S. agalactiae (group B strep) status during the third trimester.
Dental Caries Development: Caused by viridans streptococci like S. mutans fermenting sugars and producing enamel-eroding acids.

Description

Test your knowledge on Streptococci and Enterococci with this informative quiz designed specifically for microbiology students. Covering important concepts such as hemolysis and characteristics of these bacteria, this quiz helps reinforce your understanding of gram-positive microorganisms.