StaphylococcusVs.Streptococcus.A Comprehensive Analysis. Comparison and Contrast.I. Mutual Characteristics:Both genera are Gram positive and have the similar spherical cell shape, therefore there are called cocci (in Greek coccus means granule).II. Visual differentiation between Staphylococci and Streptococcibycellular arrangement:When performing laboratory analysis, after Gram staining, first thing we should do is put a piece of a colony under microscope and observe cellular arrangement of the bacteria. Both staphylococci and streptococci have round, spherical cell shape, but the arrangement of cells is different due to a different binary fission. Streptococci form a chain of round cells, because their division occurs in one linear direction, whereas staphylococci divide in various directions forming grape-like clusters.

III. Biochemical differentiation between Staphylococci and Streptococci with CATALASE test:The main criterion for differentiation between Staphylococcusand Streptococcus genera is the catalase test. Staphylococci are catalase positive whereas Streptococci are Catalase negative. Catalase is an enzyme used by bacteria to induce the reaction of reduction of hydrogen peroxide into water and oxygen.III-A.Biochemicaldifferentiation among Staphylococci:There are at least three Staphylococci species of clinical importance:1.Staphylococcus aureusis the most pathogenic for humans2.Staphylococcus epidermidis, which is part of the normal flora and is of low pathogenicity, and3.Staphylococcus saprophyticuswhich can cause urinary tract infections, especially in sexually active young women.1.Differentiation betweenStaphylococcus aureusand other Staphylococci:-COAGULASE testwhich is positive forStaphylococcus aureus(generally accepted criterion for the identification) and negative for all other Staphylococci. Coagulase is an enzyme used byS.aureusto induce coagulation and convert soluble fibrinogen into fibrin which will protect bacteria from the immune system. It is also a clumping factor for bacterias coalescence.All other staphylococcus species can be collectively referred to as coagulase-negativestaphylococci.-STAPHYLOSLIDE testthat will determine if bacteria has two types of proteins: Fibrinogen receptor and Protein A. With this testS. aureuswill cause notable agglutination. Agglutination will not be seen if the isolate isS. epidermidis or S. saprophyticus.- Presence ofHEMOLYSIS. While others dont have any,Staphylococcus aureushas Beta hemolysis.2.Differentiation betweenStaphylococcus epidermisandStaphylococcus saprophyticuscan be made withreaction to NOVOBIOCIN(antibiotic produced by the actinomyceteStreptomyces nivensand used to treat infections by gram-positive bacteria).S. saprophyticusis resistant to novobiocin (at a concentration of 5 mg), and this is used to differentiate the organism fromS. epidermidiswhich is susceptible to novobiocin.StaphylococcusaureusStaphylococcus epidermidisStaphylococcussaprophyticus

Catalase test+++

Coagulase test+--

Staphyloslide test+--

Colour differences in coloniesGold yellowWhiteWhite to yellow

Hemolysis testBetaNoneNone

Reaction to NovobiocinSensitiveSensitiveResistant

III-B.Biochemicaldifferentiation among Streptococci:The various streptococci have genus-species Latin names. However, traditionally, clinical laboratories report them by theirtype of hemolysisandLancefield serological group. The first step in correctly identifying aStreptococcusin the clinical laboratory is an accurate determination of the type of hemolysis the organism produces. Streptococci may be classified into two main divisions on the basis of their hemolytic action on blood agar:I.Beta hemolyticcomplete hemolysis of erythrocytesThese are arranged into 18 groups A-U known as Lancefield groups. Groups are determined byPRECIPITIN test,serologictest to measure a specific reaction between antigen (C carbohydrate, located in the cell wall) and antibody which results in a visible precipitate.Group AStreptococci (Streptococcus pyogenes) is among the most important human pathogens. Their important diagnostic criterion is susceptibility toBacitracin(polypeptide antibiotic obtained from a strain of the bacteriumBacillus subtilisand used as a topical treatment for certain bacterial infections, especially those caused by cocci). Many strains have a hyaluronic acid capsule that is antiphagocytic.Group BStreptococci (Streptococcus agalactiae) are bacitracin resistant.Group Dinclude Enterococci (Streptococcus faecalis) and Non-enterococci (Streptococcus bovis). Enterococci grow in 6.5% NaCl and are not killed by penicillin G (the most commonly used penicillin compound, used primarily in the form of its stable salts, also calledbenzylpenicillin). Non-enterococci are inhibited by 6.5% NaCl and killed by Penicillin G.II. Non-Beta Hemolytic (Alpha hemolyticpartial or green hemolysis of erythrocytes orGamma hemolyticno hemolysis.). Differentiation among this group can be made withOPTOCHIN test. Members of this group are:Streptococcus pneumoniae: Inhibited by Optochin (ethyl hydrocupreine).Viridans groupof Streptococci (Streptococcus mitis, Streptococcus sanguis andStreptococcus mutans): not inhibited by optochin and not bile-soluble, in contrast toS.pneumoniae.Streptococcus mutanssynthesizes polysaccharides (dextrans) that are found in dental plaque and lead to dental cariesLancefield groupHemolysisDiagnostic features

S. pyogenesABetaBacitracin sensitive

S. agalactiaeBBetaBacitracin resistantHippurate hydrolyzed

S. faecalis (Enterococcus)DAlpha or Beta or noneGrowth in 6.5% NaCl

S. bovisDAlpha or noneNo Growth in 6.5% NaCl

S. pneumoniaeNot applicableAlphaBile solubleInhibited by optochin

Viridans groupNot applicableAlphaNot bile solubleNot inhibited by optochin

Significance of Catalase test in MicrobiologyAll aerobes and facultative anaerobe microorganisms use oxygen for growth and metabolism.The superoxide anion is a product of oxygen reduction and is capable of participating in destructive reactions potentially lethal to the cell. Moreover, products of secondary reactions may amplify toxicity.For example, one hypothesis holds that the superoxide anion reacts with hydrogen peroxide in the cell:O2 + H2O2' OH+ OH.+ O2This reaction, known as the Haber-Weiss reaction, generates a free hydroxyl radical (OH.), which is the most potent biologic oxidant known. It can attack virtually any organic substance in the cell. Aerobe and facultative anaerobe microorganisms contain a high concentration of an enzyme calledsuperoxide dismutase. This enzyme converts the superoxide anion into ground-state oxygen and hydrogen peroxide, thus freeing the cell of destructive superoxide anions:2O2 + 2H+Superoxide DismutaseO2+ H2O2The hydrogen peroxide generated in this reaction is an oxidizing agent, but it does not damage the cell as much as the superoxide anion and tends to diffuse out of the cell. Many organisms possesscatalaseor peroxidase or both to eliminate the H2O2.Catalase is enzyme that decomposes hydrogen peroxide (H2O2) to water and ground-state oxygenH2O2+ H2O2Catalase2H2O + O2Catalase testis particularly useful in differentiating staphylococci genus and family of micrococcacae (genera:ArthrobacterandMicrococcus), which are catalase-positive, from streptococciand enterococci, which are catalase-negative.How to perform thetest?- Dip a capillary tube into 3%H2O2..Touch a colony .Observe the tube for bubble indicating a positive reaction. Result: Bubles: positive, no bubbles: negative reaction.

Special Features- catalase is found in most aerobic and facultative anaerobic bacteria. The main exception isStreptococci, which have catalase negative test.Catalase is not found in anaerobes.Precautions in interpretation: It is important not to contaminate the bacterial colony under test with blood agar. Red blood cells contain catalase and their presence will give a false positive result. Old cultures may loose their catalase activity, possible resulting in a false negative result.MicroorganismCatalase test

StaphylococciPositive (exception: Staphylococcus aureus, subspecies anaerobius is catalase negative)

StreptococciNegative

Actinomyces israeliiNegative

FusobacteriumNegative

Prevotella melaninogenicaNegative

Family of EnterobacteriaceaePositive

-Escherichia colliRare types from moderate to mostly non-reactive

-SalmonellaModerate positive reaction

-ShigellaMostly non-reactive

ClostridiumNegative

As stated inCatalase Test as an Aid to the Identification of Enterobacteriaceaeresearch paper published in 1972, family of enterobacteriaceae have differentiation of catalase positive reaction, from vigorous ( Serratia, Proteus and Providencia), moderate ( Salmonella, some rare types of Escherichia, Enterobacter and Klebsiela) to non-reactive (most types of Escherichia and Shigella).