Gram Positive Cocci Archives • Microbe Online

Staphylococcus saprophyticus: Characteristics and Diagnosis

Staphylococcus saprophyticus causes urinary tract infections (UTI), especially cystitis in sexually active young women.

Viridans Streptococci: Pathogenesis and Lab Diagnosis

The viridans streptococci are another important Gram-positive cocci comprising a large group of bacteria and are commensals of mouth.

Enterococcus faecalis: Properties, Pathogenesis, Lab Diagnosis

Enterococcus is gram-positive cocci in chains and is catalase negative. It causes infections of Urinary tract and biliary tract.

Streptococcus agalactiae (GBS): Properties, Pathogenesis, Lab Diagnosis

Streptococcus agalactiae (GBS), is a beta-hemolytic, CAMP test positive, gram-positive cocci. It can cause severe infection in newborns.

Furazolidone Disk Test: Principle, Procedure Results

Furazolidone disk test is used to differentiate staphylococci (sensitive) from micrococci (resistant).

Staphylococcus aureus Virulence Factors

Major virulence factors of S. aureus are capsule, teichoic acid, protein A, enterotoxin, TSST-1, coagulase, hyaluronidase, etc.

Streptococcus Pneumoniae Virulence Factors

S. pneumoniae virulence factors include capsular polysaccharide, C carbohydrate antigen, pneumolysin, autolysin.

Pus Sample: Collection, Processing, Staining and Culture

Pus aspirate is the preferred sample. S. aureus, Strep pyogenes, and members of Enterobacteriaceae are major pathogens.

Pneumococcal Urinary Antigen Testing (UAT)

Pneumococcal urinary antigen testing is a rapid assay that detects Streptococcus pneumoniae antigen (C-polysaccharide) in the urine of patients.

Streptococcus pyogenes Virulence Factors

Major virulence factors of S.pyogenes are adhesions, M protein, hemolysins, pyrogenic exotoxins and spreading factors.

Staphylococcus vs. Micrococcus

Micrococcus is lysostaphin and furazolidone resistant, bacitracin sensitive and microdase positive. Find the results of Staphylococcus.

Streptococcus Pyogenes (GAS): Characteristics, Diseases, Tests

This group A beta-hemolytic streptococci is bacitracin sensitive and causes strep sore throat, rheumatic fever, and PSGN.

Staphylococcus vs. Streptococcus

Staphylococci are catalase positive, gram positive cocci in clusters but Streptococci are catalase negative and may appear in pairs or chains.

Hippurate Hydrolysis Test: Principle, Procedure, Results

Campylobacter jejuni, Listeria monocytogenes, Gardnerella vaginalis, and Streptococcus agalactiae are positive for hippurate hydrolysis test.

Lancefield Classification of Streptococci

Beta hemolytic streptococci are arranged into twenty (20) groups A-U without I and J (i.e. A through H and K through V).

Bile-Esculin test for Enterococcus species

Bile-esculin test is widely used to differentiate Enterococci and Non-enterococcus group D streptococci from non-group D viridans group streptococci.

Salt Tolerance Test for Enterococcus species

Salt tolerance test determines the ability of an organism to grow in high concentrations of salt (6.5%).

PYR Test: Principle, Procedure, Results

Some gram-positive cocci such as Enterococcus produces enzyme L-pyrroglutamylaminopeptidase that hydrolyze PYR substrate.

Catalase test: Principle, Procedure, Results, Uses

Catalase test is used to distinguish among Gram-positive cocci. Staphylococci are catalase-positive but Streptococci are catalase-negative.

Gram-Positive vs. Gram-Negative Bacteria

Gram positive bacteria appear purple and gram-negative bacteria appear pink when stained by Gram-staining methods.

$Anti-streptolysin O Titer: ASO Test$

Anti-streptolysin O Titer: ASO Test

Rapid latex agglutination test for the qualitative and semi-quantitative determination of anti-streptolysin-O antibodies (ASO) in serum.

How to identify Streptococcus pneumoniae?

Gram positive diplococci (lanceolate shaped), alpha hemolysis, optochin sensitive and bile soluble isolates are S.pneumoniae.

Novobiocin Susceptibility Test: Principle, Procedure, Results

Novobiocin test is used to differentiate CONS and presumptively identify the isolate as Staphylococcus saprophyticus (novobiocin resistant).

Optochin Sensitivity Test: Principle, Procedure, Results

Optochin (ethylhydrocupreine hydrochloride) lyses pneumococci (positive) but alpha-streptococci are resistant (negative).

Bile Solubility Test: Principle, Procedure, Results

Bile solubility test differentiates S. pneumoniae (positive) from alpha-hemolytic streptococci (negative).

Bacitracin Test: Principle, Procedure, Results

Bacitracin test differentiates S. pyogenes (inhibited) from other beta-hemolytic streptococci.

Streptococcus pneumoniae (pneumococcus): Disease, Properties

Pneumococcus is lanceolate shaped gram-positive cocci and causes pneumonia and meningitis. Its is optochin sensitive and bile soluble.

Biochemical Tests for Bacterial Identification

Catalase test, oxidase test, MUG test, optochin sensitivity test, bacitracin sensitivity test, coagulase test, etc are some of the common biochemical tests.

Size, Shape, Arrangement of Bacteria

Bacteria exist in four basic morphologies: cocci; rod-shaped cells, or bacilli; spiral-shaped cells, or spirilla; and comma-shaped cells, or vibrios.

Teichoic Acid: Structure, Functions

Teichoic acids are fibers of glycerol phosphate or ribitol phosphate and is located in the cell-wall of gram-positive bacteria.

Staphylococcus aureus: Disease, Properties, Lab Diagnosis

Frequent colonizer of skin, S. aureus is a major cause of surgical wound infection. This gram-positive cocci is catalase and coagulase +ve.

Coagulase Test: Principle, Procedure, Results

Coagulase test detects clumping factors and bound coagulase and differentiates Staphylococcus aureus (positive) from CoNS (negative).

Name of Gram-positive cocci	Diseases
Staphylococcus aureus	Surgical-site infections, skin infection, hospital-acquired pneumonia, osteomyelitis, toxic-shock syndrome, necrotizing fasciitis, food-poisoning, infective arthritis
Streptococcus pyogenes	Acute pharyngitis (strep-sore throat), impetigo, erysipelas, necrotizing fasciitis, myositis,
Streptococcus pneumoniae	Bacterial pneumonia, meningitis, otitis media, sinusitis, bronchitis, bacteremia, scarlet fever, rheumatic fever, post-streptococcal glomerulonephritis, and streptococcal toxic shock syndrome
Streptococcus agalactiae	Postpartum infection and neonatal sepsis
Enterococcus faecalis	Urinary tract infections, bacteremia, ocular infections, mitral valve endocarditis, meningitis (rarely)