Catalase negative, Gram positive cocci

Question 1

What enzyme are Streptococcus and Enterococcus species negative for, which differentiates them from staphylococci?

Answer 1

Catalase.

Question 2

What type of oxygen requirement do Streptococcus and Enterococcus species have?

Answer 2

Facultative anaerobes

Question 3

Name a common pathogen in human infections caused by Group A Streptococcus.

Answer 3

Streptococcus pyogenes.

Question 4

Which Streptococcus species is known for causing neonatal infections?

Answer 4

Streptococcus agalactiae (Group B Streptococcus).

Question 5

Which Enterococcus species are commonly encountered in nosocomial infections?

Answer 5

Enterococcus faecalis and Enterococcus faecium.

Question 6

To which Lancefield group does Streptococcus pyogenes belong?

Answer 6

Group A.

Question 7

What type of hemolysis is exhibited by Streptococcus pyogenes on blood agar?

Answer 7

β-hemolysis (complete hemolysis).

Question 8

Is Streptococcus pyogenes sensitive or resistant to bacitracin?

Answer 8

Bacitracin sensitive

Question 9

What test result helps to differentiate Streptococcus pyogenes from other streptococci?

Answer 9

PYR test positive.

Question 10

What virulence factor is responsible for the β-hemolytic pattern of Streptococcus pyogenes on blood agar plates and is oxygen-labile?

Answer 10

Streptolysin O.

Question 11

Which virulence factor is oxygen-stable and nonimmunogenic, yet capable of lysing erythrocytes in the presence of room air?

Answer 11

Streptolysin S.

Question 12

Which enzyme known as the “spreading factor” helps Streptococcus pyogenes spread through tissues?

Answer 12

Hyaluronidase.

Question 13

What protein enables Streptococcus pyogenes to resist phagocytosis and adhere to mucosal cells?

Answer 13

M protein

Question 14

It causes the red spreading rash seen in scarlet fever.

Answer 14

erythrogenic toxin

Question 15

Which virulence factor of Streptococcus pyogenes can lyse fibrin clots?

Answer 15

Streptokinase.

Question 16

Which virulence factor of Streptococcus pyogenes is antigenic, allowing for detection of antibodies following infection?

Answer 16

DNAseB

Question 17

What is the most common bacterial cause of acute pharyngitis in children aged 5 to 15?

Answer 17

Streptococcus pyogenes (Group A).

Question 18

Which skin infection caused by S. pyogenes is characterized by perioral blistered lesions with honey-colored crusts?

Answer 18

Impetigo (Impetigo Contagiosa).

Question 19

What is a potential complication of impetigo caused by S. pyogenes?

Answer 19

Post-streptococcal glomerulonephritis (poststrep GN).

Question 20

What superficial skin infection caused by S. pyogenes extends into the dermal lymphatics?

Answer 20

Erysipelas.

Question 21

Which deeper skin infection involving subcutaneous or dermal tissues is facilitated by hyaluronidase?

Answer 21

Cellulitis

Question 22

What rapidly progressive infection of deep subcutaneous tissues is facilitated by exotoxin B?

Answer 22

Necrotizing Fasciitis.

Question 23

Which enzyme produced by Streptococcus pyogenes facilitates the spread of cellulitis by breaking down hyaluronic acid in connective tissues?

Answer 23

Hyaluronidase.

Question 24

What condition, often associated with streptococcal pharyngitis, is caused by streptococcal pyrogenic exotoxins and presents with a characteristic sandpaper-like rash and strawberry tongue?

Answer 24

Scarlet Fever.

Question 25

How is the diagnosis of acute pharyngitis (strep throat) confirmed in a clinical setting?

Answer 25

Diagnosis is confirmed through a throat culture or a positive rapid strep test.

Question 26

Acute pharyngitis most common bacterial cause

Answer 26

S. pyogenes

Question 27

What is Streptococcal Toxic Shock Syndrome similar to?

Answer 27

Toxic shock syndrome caused by Staphylococcus aureus.

Question 28

What mediates STSS?

Answer 28

Production of potent streptococcal pyrogenic exotoxins (SPEs).

Question 28

What often tests positive in cases of STSS?

Answer 28

Blood cultures for Streptococcus pyogenes.

Question 29

What protein is associated with Rheumatic Fever?

Answer 29

M protein.

Question 30

What precedes Rheumatic Fever?

Answer 30

A respiratory tract infection believed to be caused by S. pyogenes.

Question 31

What protein mediates Acute Glomerulonephritis?

Answer 31

M protein.

Question 32

What condition is associated with immune complex deposition in the kidneys?

Answer 32

Acute glomerulonephritis.

Question 33

Microscopy: Gram-positive cocci, some in short chains or pairs, round to oval-shaped, occasionally forming elongated cells resembling pleomorphic corynebacteria or lactobacilli.

Answer 33

Streptococcus pyogenes

Question 34

What media is used for cultivating Streptococcus pyogenes?

Answer 34

5% sheep blood agar, chocolate agar, and 5% sheep blood agar with trimethoprim-sulfamethoxazole (SXT) for throat swabs.

Question 35

Blood agar: Small, transparent, smooth colonies with β-hemolysis.

Answer 35

Streptococcus pyogene

Question 36

what test: o presumptively identify and differentiate β-hemolytic group A streptococci (S. pyogenes-susceptible) from other β-hemolytic streptococci.

Answer 36

Bacitracin test

Question 37

What indicates a positive Bacitracin test result?

Answer 37

Any ZOI greater than 10 mm indicates susceptibility.

Question 38

What indicates a negative Bacitracin test result?

Answer 38

No ZOI indicates resistance.

Question 39

what test: Presumptive identification of Group A streptococci (S. pyogenes) and enterococci by detecting the enzyme L-pyrrolidonyl arylamidase.

Answer 39

PYR test

Question 40

What indicates a positive PYR test result?

Answer 40

Bright red color within 5 minutes.

Question 41

What does the Anti-streptolysin O (ASO) test detect?

Answer 41

Antibodies against streptolysin O, a toxin produced by S. pyogenes.

Question 42

What indicates a negative PYR test result?

Answer 42

No color change or an orange color.

Question 43

What organism: Gram-positive cocci in chains Lancefield group B β-hemolytic Bacitracin resistant CAMP test positive PYR negative Hippurate hydrolysis positive Resistant to SXT

Answer 43

Streptococcus agalactiae

Question 44

Where is Streptococcus agalactiae commonly found?

Answer 44

Normal microbiota in the female genital tract and lower gastrointestinal tract Occasional colonizer of the upper respiratory tract

Question 45

What is the most important virulence factor of Streptococcus agalactiae?

Answer 45

Capsule

Question 46

What other potential virulence factors are associated with Streptococcus agalactiae, though not proven to be factors in infection?

Answer 46

DNAse and hyaluronidase

Question 47

Is Streptococcus agalactiae PYR positive or negative?

Answer 47

PYR negative.

Question 48

What are common infections caused by Streptococcus agalactiae in neonates and infants?

Answer 48

Pneumonia (0–2 months old) Meningitis Sepsis

Question 49

what organism Postpartum infections (e.g., endometritis, pelvic abscesses, septic shock) Bacteremia Pneumonia Endocarditis Arthritis Osteomyelitis Skin and soft tissue infections

Answer 49

Streptococcus agalactiae in adults

Question 50

In which group of adults is Streptococcus agalactiae infection more commonly seen?

Answer 50

Immunocompromised adults.

Question 51

Blood agar: Grayish-white mucoid colonies surrounded by a small zone of β-hemolysis.

Answer 51

Streptococcus agalactiae

Question 52

How is Streptococcus agalactiae detected in vaginal or rectal swabs during pregnancy?

Answer 52

Inoculated into Todd-Hewitt broth (containing gentamicin, nalidixic acid, or colistin and nalidixic acid) such as LIM.

Question 53

What is the appearance of Streptococcus agalactiae on CHROMagar StrepB?

Answer 53

Mauve colored colonies.

Question 54

How is a positive CAMP test result interpreted?

Answer 54

Enhanced hemolysis indicated by an arrowhead-shaped zone of beta-hemolysis at the juncture of the two organisms.

Question 55

What does a positive hippurate hydrolysis test indicate for Streptococcus agalactiae?

Answer 55

The production of hippuricase, with a purple-colored product formed due to the reaction of end products of ninhydrin oxidation.

Question 56

Hippuric acid is deaminated by the enzyme?

Answer 56

hippuricase

Question 57

Principle of hippurate hydrolysis

Answer 57

Hippurate acid ->hippuricase> glycine benzoic acid

Question 58

Gram-positive “lancet-shaped” cocci, alpha-hemolytic.

Answer 58

Streptococcus pneumoniae

Question 59

Bile solubility sensitive, optochin sensitive, positive Quellung reaction.

Answer 59

Streptococcus pneumoniae

Question 59

It is the leading cause of bacterial meningitis in infants, young children, and adults in the US, followed by N. meningitidis and H. influenzae

Answer 59

Streptococcus pneumoniae

Question 60

What is the key virulence factor of Streptococcus pneumoniae?

Answer 60

Capsule, which inhibits phagocytosis and has 80 antigenic types.

Question 61

It activates the classical complement pathway and suppresses the oxidative burst of phagocytes.

Answer 61

pneumolysin

Question 62

It binds to receptors for platelet-activating factor in endothelial cells, leukocytes, platelets, and tissue cells of the lungs and meninges, aiding in entry and spread of the organism.

Answer 62

phosphorylcholine

Question 63

What percentage of bacterial pneumonia cases is caused by Streptococcus pneumoniae?

Answer 63

95% of all bacterial pneumonia cases.

Question 64

What are common diseases associated with Streptococcus pneumoniae?

Answer 64

Bacterial pneumonia, sinusitis, otitis media, bacteremia, and meningitis.

Question 65

It is the leading cause of bacterial meningitis in infants, young children, and adults in the US.

Answer 65

Streptococcus pneumoniae

Question 66

Which other bacteria follow Streptococcus pneumoniae in causing bacterial meningitis?

Answer 66

Neisseria meningitidis and Haemophilus influenzae

Question 67

Microscopy: Leukocytosis and numerous lancet-shaped cocci occurring singly, in pairs, or in short chains.

Answer 67

Streptococcus pneumoniae

Question 68

On which types of media can Streptococcus pneumoniae be cultivated?

Answer 68

Brain heart infusion agar, trypticase soy agar with 5% sheep blood, or chocolate agar. It may require increased CO2 for optimal growth.

Question 69

Blood agar: Round, glistening, wet, mucoid, dome-shaped colonies with alpha-hemolysis.

Answer 69

Streptococcus pneumoniae

Question 70

What does a positive Optochin (P disk) susceptibility test indicate?

Answer 70

A positive test indicates that the organism is susceptible to optochin, which is characteristic of Streptococcus pneumoniae. A zone of inhibition (ZOI) of at least 14 mm around the disk is considered positive.

Question 71

How does the Bile solubility test differentiate Streptococcus pneumoniae from other alpha-hemolytic streptococci?

Answer 71

Streptococcus pneumoniae is bile soluble, meaning its colonies disintegrate when exposed to bile or bile salts, while other alpha-hemolytic streptococci are bile insoluble and remain intact.

Question 72

detects capsular subtypes of Streptococcus pneumoniae by causing the capsule to swell, which is visible under the microscope.

Answer 72

Quellung test

Question 73

Species: PYR positive, possess group D antigen, grow in 6.5% NaCl, and are LAP positive.

Answer 73

Enterococcus species

Question 74

Which Enterococcus species are most commonly encountered as pathogens?

Answer 74

E. faecalis and E. faecium are the pathogenic species most commonly encountered

Question 75

Enterococcus: most commonly encountered

Answer 75

E. faecalis

Question 76

Enterococcus: more frequent vancomycin resistance

Answer 76

E. faecium

Question 77

What are key virulence factors of Enterococcus species?

Answer 77

Aggregation substance Capsular polysaccharides Surface carbohydrates Ability to translocate across intact intestinal mucosa Hemolysis Lipoteichoic acid Gelatinase Superoxide production Peptide inhibitors Ability to adhere to extracellular matrix proteins

Question 78

What are common infections caused by Enterococcus species?

Answer 78

Urinary tract infections (UTIs) Bacteremia Endocarditis Intra-abdominal, pelvic, wound, and soft tissue infections

Question 79

How is Enterococcus identified using the PYR test?

Answer 79

Enterococcus species hydrolyze PYR, leading to a positive result in the PYR test.

Question 80

How does the 6.5% NaCl broth test help in identifying Enterococcus?

Answer 80

Enterococcus species can grow in 6.5% NaCl broth, which is used to differentiate them from non-enterococci. Positive result shows visible turbidity and possible color change from purple to yellow.

Question 81

Enterococci is resistant or sensitive to high salt concentration

Answer 81

resistant

Question 82

It is used as the test medium for enterococcus

Answer 82

HEart infusion broth containing 6.5% NaCl

Question 83

What test helps in the presumptive identification of catalase-negative gram-positive cocci by detecting the enzyme leucine aminopeptidase.

Answer 83

Leucine Aminopeptidase (LAP) test for Enterococcus

Question 84

How does a positive Leucine Aminopeptidase (LAP) test result appear?

Answer 84

A positive LAP test will show the development of a red color within 1 minute after adding cinnamaldehyde reagent.

Question 85

What are the antibiotic resistance characteristics of Enterococcus?

Answer 85

Enterococcus species are intrinsically more resistant to antimicrobials, including cephalosporins and aminoglycosides. Vancomycin-resistant Enterococcus (VRE) is also a notable concern in healthcare settings.

Question 86

Not groupable by Lancefield serology

Answer 86

Viridans streptococci

Question 87

Butterscotch smell, especially on chocolate agar

Answer 87

Viridans streptococci

Question 88

Fastidious and some strains require increased carbon dioxide for growth Alpha-hemolysis or no hemolysis (greening) on sheep blood agar Butterscotch smell, especially on chocolate agar

Answer 88

Viridans streptococci

Question 89

Where are Viridans streptococci normally found?

Answer 89

Normal microbiota in the oral cavity, oropharynx, gastrointestinal tract (GIT), and vagina.

Question 90

part of the normal microbiota in the oral cavity, oropharynx, GIT, and vagina, and is involved in infections after dental or surgical procedures

Answer 90

S. anginosis group

Question 91

What kind of odor might you notice with Viridans streptococci on chocolate agar?

Answer 91

A butterscotch smell.

Question 92

Key role in development of dental carries

Answer 92

S. mutants