STREPTOCOCCSTREPTOCOCCUSUS

Pavithra G. Pavithra G. PalanPalan

Streptococci are Gram positive cocci.Streptococci are Gram positive cocci. Arranged in chains or pairs.Arranged in chains or pairs. The name streptococci (The name streptococci (streptosstreptos

meaning twisted or coiled) was given meaning twisted or coiled) was given by by BillrothBillroth..

CLASSIFICATIONCLASSIFICATION::

Streptococci

Aerobes & facultative anaerobes

Obligate anaerobesEg: Peptostreptococci

Beta haemolyticGamma haemolytic

Eg: Enterococcus groupAlpha haemolytic

Eg: Viridans streptococci

20 Lancefield groups(ABCDEFGHKLMNOPQRSTUV)

80 Griffith types(1,2,3,etc. up to 80)

02 requirement

Haemolysis

Serological Grouping (C carbohydrate antigen)

Group A- Streptococcus pyogens

Serological typing (M Protein)

Streptococcus pyogensStreptococcus pyogens

MORPHOLOGYMORPHOLOGY::

Gram positive Gram positive spherical or oval spherical or oval cocci arranged in cocci arranged in chains.chains.

Individual coccus Individual coccus will be 0.5-1.0will be 0.5-1.0μμm in m in diameter.diameter.

They are nonmotile They are nonmotile and nonsporing.and nonsporing.

Some strains have Some strains have capsule composed capsule composed of hyaluronic acid. of hyaluronic acid.

CULTURECULTURE::

Media usedMedia used::

1. Non selective media:- Sheep blood 1. Non selective media:- Sheep blood agaragar

2. Selective media:- Crystal violet blood 2. Selective media:- Crystal violet blood agaragar

PNF mediumPNF medium

Cultural characteristicsCultural characteristics: On : On blood agarblood agar, , afterafter

overnight incubation, the colonies are overnight incubation, the colonies are small,small,

circular, low convex with an area of circular, low convex with an area of

ββ-haemolysis around them. -haemolysis around them.

Biochemical reactionsBiochemical reactions::

1. Catalase test: Negative1. Catalase test: Negative

2. Bile solubility test: Negative2. Bile solubility test: Negative

Positive

Negative

3. PYR test: Positive3. PYR test: Positive

4. Ribose is not fermented.4. Ribose is not fermented.

PATHOGENICITYPATHOGENICITY::

Source of infectionSource of infection::

1. Patient1. Patient

2. Carriers2. Carriers

Mode of transmissionMode of transmission::

1. Contact: direct or indirect( through 1. Contact: direct or indirect( through fomites)fomites)

2. Inhalation of air borne droplets2. Inhalation of air borne droplets

Antigenic structureAntigenic structure::

1.Capsular hyaluronic acid:1.Capsular hyaluronic acid:

2.Cell wall antigens:2.Cell wall antigens:a) Inner layer of peptidoglycan a) Inner layer of peptidoglycan b) Middle layer of group specific C carbohydrateb) Middle layer of group specific C carbohydratec) Outer layer of protein (fimbriae) & c) Outer layer of protein (fimbriae) &

lipoteichoic acidlipoteichoic acid

3.Type specific antigens:3.Type specific antigens:a) M proteina) M proteinb) T proteinb) T proteinc) R proteinc) R protein

Antigenic structure of S. pyogens

Virulence factorsVirulence factors::

These includeThese include

A) Toxins A) Toxins

B) Enzymes B) Enzymes

A) A) ToxinsToxins::

1. Haemolysins 1. Haemolysins

a) Streptolysin ‘O’a) Streptolysin ‘O’

b) Streptolysin ‘S’b) Streptolysin ‘S’

2. Pyrogenic exotoxin( Erythrogenic 2. Pyrogenic exotoxin( Erythrogenic toxin)toxin)

B) B) EnzymesEnzymes::

1. Streptokinase (Fibrinolysin)1. Streptokinase (Fibrinolysin)

2. Deoxyribonuclease 2. Deoxyribonuclease (Streptodornase)(Streptodornase)

3. NADase3. NADase

4. Hyaluronidase4. Hyaluronidase

DiseasesDiseases::

Diseases caused by S. pyogens is studiedDiseases caused by S. pyogens is studied

under 2 groupsunder 2 groups

1. Suppurative infections1. Suppurative infections

2. Non suppurative complications2. Non suppurative complications

1. 1. Suppurative infectionsSuppurative infections::

Pyogenic infections.Pyogenic infections.

Spreads locally, along lymphatics Spreads locally, along lymphatics and and

through the blood stream. through the blood stream.

Common suppurative infections areCommon suppurative infections are::

A) A) Respiratory infectionsRespiratory infections:-:- TonsillitisTonsillitis

sore throatsore throat PharyngitisPharyngitis Otitis mediaOtitis media MastoiditisMastoiditis Quinsy Quinsy Ludwig’s anginaLudwig’s angina Rarely it may cause pneumonia & meningitisRarely it may cause pneumonia & meningitis Scarlet fever (sore throat & skin rash)Scarlet fever (sore throat & skin rash)

Tonsillitis

Pharyngitis

Otitis media

Mastoiditis

Quinsy

Ludwig’s angina

Skin rashes in Scarlet fever

B) B) Skin infectionsSkin infections:-:-

Infection of wounds & burnsInfection of wounds & burns

ImpetigoImpetigo

ErysipelasErysipelas

Impetigo

Erysipelas

C) C) Soft tissue infectionsSoft tissue infections:-:-

i) Cellulitis i) Cellulitis

ii) Necrotising ii) Necrotising fasciitisfasciitis

iii) Soft tissue infections with some M iii) Soft tissue infections with some M types of strains may sometime cause types of strains may sometime cause toxic shocktoxic shock syndromesyndrome resembling resembling staphylococcal TSS.staphylococcal TSS.

D) D) Genital InfectionsGenital Infections:-Puerperal sepsis:-Puerperal sepsis

E) E) Other suppurative infectionsOther suppurative infections:-:-

PyemiaPyemia

SepticemiaSepticemia

Abscesses in internal organs such as Abscesses in internal organs such as brain, lungs, liver and kidney.brain, lungs, liver and kidney.

2. 2. Non suppurative complicationsNon suppurative complications::

It is also called as post streptococcal It is also called as post streptococcal complicationscomplications

Non suppurative complications of Non suppurative complications of S.pyogens occur 1-4 weeks after the S.pyogens occur 1-4 weeks after the acute infection.acute infection.

The organism may not be detectable The organism may not be detectable when these complications set in.when these complications set in.

These complications are believed to be These complications are believed to be the result of hypersensitivity to some the result of hypersensitivity to some streptococcal components.streptococcal components.

The complications are-The complications are-

1. Acute rheumatic fever1. Acute rheumatic fever

2. Acute glomerulonephritis2. Acute glomerulonephritis

1. 1. Acute rheumatic feverAcute rheumatic fever: : It occurs after repeatedIt occurs after repeatedsore throat caused by S. pyogens.sore throat caused by S. pyogens.

Mechanism of pathogenesis:Mechanism of pathogenesis:During primary infection antibodies will be producedDuring primary infection antibodies will be producedagainst some streptococcal antigen.against some streptococcal antigen.

Since streptococcal antigen has similarity with cardiacSince streptococcal antigen has similarity with cardiactissue antigen, the antibodies will cross react withtissue antigen, the antibodies will cross react withcardiac tissue antigen causing destruction. cardiac tissue antigen causing destruction.

Leads to clinical symptoms such as Aschoff’s nodules,Leads to clinical symptoms such as Aschoff’s nodules,carditis, fever and malaise.carditis, fever and malaise.

2. 2. Acute glomerulonephritisAcute glomerulonephritis:: It follows after skin It follows after skin infection caused by S. pyogens nephritogenic infection caused by S. pyogens nephritogenic types.types.

Mechanism of pathogenesis:Mechanism of pathogenesis:

During skin infection caused by nephritogenic types During skin infection caused by nephritogenic types ofof

S. pyogens, the antibodies will be produced againstS. pyogens, the antibodies will be produced againstcell membrane antigen.cell membrane antigen.

These antibodies cross react with glomerular These antibodies cross react with glomerular basement membrane antigen causing destruction.basement membrane antigen causing destruction.

Leads clinical symptoms such as proteinuria,Leads clinical symptoms such as proteinuria,haematuria & hypertension.haematuria & hypertension.

LABORATORY DIAGNOSIS:LABORATORY DIAGNOSIS:

A) In acute suppurative infectionA) In acute suppurative infection

Specimens to be collectedSpecimens to be collected:: Throat swab,Throat swab, Pus,Pus, Tissue material,Tissue material, Blood,Blood, Swab from nose for detection of Swab from nose for detection of

carriers.carriers.

Transport mediaTransport media: : Pike’s mediumPike’s medium

I) I) Direct MicroscopyDirect Microscopy::

Direct microscopy Direct microscopy with Gram stained with Gram stained smear is useful in smear is useful in case of pus & CSF, case of pus & CSF, where cocci in chains where cocci in chains are seen.are seen.

This is of no value for This is of no value for

specimen like sputum specimen like sputum & genital swabs & genital swabs where mixed flora are where mixed flora are normally present.normally present.

Methods of Methods of examinationexamination:-:-

c) Gram’s staining: c) Gram’s staining: Smears are Smears are examined from examined from the culture plate the culture plate and reveals and reveals Gram positive Gram positive cocci in chains.cocci in chains.

II) II) CultureCulture::

a) Media used:a) Media used:

b) Cultural Characteristics:b) Cultural Characteristics:

d) Biochemical reactions:d) Biochemical reactions:

e) Bacitracin (1 unit/ml) sensitivity test: e) Bacitracin (1 unit/ml) sensitivity test:

S. pyogens is sensitive.S. pyogens is sensitive.

f) Lancefield sero grouping: Based on ‘C’ f) Lancefield sero grouping: Based on ‘C’ carbohydrate antigencarbohydrate antigen

g) Sero typing: sero typing of S. pyogens g) Sero typing: sero typing of S. pyogens is required only for epidemiological is required only for epidemiological purposes.purposes.

III) III) Antigen detectionAntigen detection::

ELISA & Agglutination tests are used ELISA & Agglutination tests are used for detection of S. pyogens antigen for detection of S. pyogens antigen from throat swabsfrom throat swabs

B) In Non-suppurative complicationsB) In Non-suppurative complications

Serological tests are usefulSerological tests are useful

The tests are –The tests are –

1. Anti Streptolysin O (ASO) test1. Anti Streptolysin O (ASO) test

2. Anti Deoxyribonuclease B (anti-DNAase B) 2. Anti Deoxyribonuclease B (anti-DNAase B) testtest

3. Anti Hyaluronidase test3. Anti Hyaluronidase test

4. Streptozyme test4. Streptozyme test

TREATMENT:TREATMENT:

Penicillin G is the drug of choice.Penicillin G is the drug of choice.

In patients allergic to penicillin; In patients allergic to penicillin; erythromycin or cephalexin is used.erythromycin or cephalexin is used.

Antibiotics have no effect on Antibiotics have no effect on established glomerulonephritis & established glomerulonephritis & rheumatic fever.rheumatic fever.

EPIDEMIOLOGY:EPIDEMIOLOGY:

Streptococcal infections of the respiratory Streptococcal infections of the respiratory tract are more frequent in children5-8 years of tract are more frequent in children5-8 years of age.age.

They are more common in winter in the They are more common in winter in the temperate countries.temperate countries.

Crowding is an important factor in the Crowding is an important factor in the transmission of infections.transmission of infections.

Outbreaks of infection may occur in closed Outbreaks of infection may occur in closed communities such as boarding school or army communities such as boarding school or army camps.camps.

PROPHYLAXIS:PROPHYLAXIS:

Prophylaxis is indicated only in the Prophylaxis is indicated only in the prevention of rheumatic fever.prevention of rheumatic fever.

It is done by long term administration of It is done by long term administration of penicillin in children who have penicillin in children who have developed early signs of rheumatic developed early signs of rheumatic fever.fever.

Antibiotic prophylaxis is not useful in Antibiotic prophylaxis is not useful in case of glomerulonephritis.case of glomerulonephritis.

OTHER HAEMOLYITC STREPTOCOCCI:OTHER HAEMOLYITC STREPTOCOCCI:

Group B: Streptococcus agalactiaeGroup B: Streptococcus agalactiae

It is a important pathogen of cattle & It is a important pathogen of cattle & causes bovine mastitis.causes bovine mastitis.

In human it inhabitats genital tract.In human it inhabitats genital tract.

Clinical significanceClinical significance::

1. 1. Infection in neonatesInfection in neonates: 2 types : 2 types

a. Early onset disease- Occurs during first a. Early onset disease- Occurs during first week of life.week of life.

Source of infection- Vagina of the mother Source of infection- Vagina of the mother &&

infection is acquired during birth.infection is acquired during birth.

Clinical symptoms- Septicemia, meningitis Clinical symptoms- Septicemia, meningitis &&

pneumonia.pneumonia.

b. Late onset disease- Occurs during 2b. Late onset disease- Occurs during 2ndnd & 12 & 12thth

week of life.week of life.

Source of infection: It usually acquired from theSource of infection: It usually acquired from thehospital environment.hospital environment.

Clinical symptoms- Osteomyelitis, arthritis,Clinical symptoms- Osteomyelitis, arthritis,conjunctivitis, respiratory infection, endocarditisconjunctivitis, respiratory infection, endocarditis& peritonitis.& peritonitis.

2. 2. Infection in adultInfection in adult: It causes bacteraemia, : It causes bacteraemia, sepsis , wound infection, septic abortion &sepsis , wound infection, septic abortion &puerperal sepsis.puerperal sepsis.

Laboratory diagnosisLaboratory diagnosis::

Specimens collectedSpecimens collected: Blood, CSF & : Blood, CSF & exudatesexudates

from lesions.from lesions.

Methods of examinationsMethods of examinations::

1. Detection of antigen in clinical samples.1. Detection of antigen in clinical samples.

2. Direct microscopy by doing Gram’s 2. Direct microscopy by doing Gram’s smear.smear.

3. Culture- Blood agar is used for culture.3. Culture- Blood agar is used for culture.

4. Identification-4. Identification-

a. Small a. Small ββ-haemolytic colonies on blood -haemolytic colonies on blood agaragar

b. Gram stainingb. Gram staining

c. Catalase test- Negativec. Catalase test- Negative

d. Hippurate hydrolysis- Positive

e. CAMP test :

f. Lancefield sero grouping is done for f. Lancefield sero grouping is done for

confirmation.confirmation.

TreatmentTreatment:: Penicillin is used. Penicillin is used.

Group D Streptococci:Group D Streptococci:

Classified intoClassified into 2 groups-2 groups-

1. The enterococcus group-1. The enterococcus group- which have which have

been reclassified as a separate genus calledbeen reclassified as a separate genus called

Enterococcus, containing- E. faecalis,Enterococcus, containing- E. faecalis,

E. faecium & E. durans.E. faecium & E. durans.

2. Non enterococcal group-2. Non enterococcal group- containing containing

S. bovis & S. equinusS. bovis & S. equinus

ENTEROCOCCUSENTEROCOCCUS

Normal inhabitants of human intestinal Normal inhabitants of human intestinal tract.tract.

Possess some distinctive properties Possess some distinctive properties like-like-

1.1. They grow in 40% bile,They grow in 40% bile,

2.2. They resist pH till 9.6.They resist pH till 9.6.

3.3. They grow in 6.5% NaCl solution,They grow in 6.5% NaCl solution,

4.4. They grow at 45ºC can withstand up to 60ºC They grow at 45ºC can withstand up to 60ºC for 30 minutes.for 30 minutes.

5.5. They grow in 0.1% methylene blue milk.They grow in 0.1% methylene blue milk.

MorphologMorphology:y:

Enterococci Enterococci typically appear as typically appear as pairs of oval Gram pairs of oval Gram positive cocci.positive cocci.

The cells in a pair The cells in a pair arranged at an arranged at an angle to each angle to each other.other.

Clinical significanceClinical significance::

Source & mode of infection:Source & mode of infection:1. Endogenous-from colonized site.1. Endogenous-from colonized site.2. Exogenous-through direct or indirect 2. Exogenous-through direct or indirect

contact.contact.

Common infections:Common infections:1.1. Urinary tract infection,Urinary tract infection,2.2. Bacteremia,Bacteremia,3.3. Wound infection,Wound infection,4.4. Biliary tract infection,Biliary tract infection,5.5. Sub acute bacterial endocarditis.Sub acute bacterial endocarditis.

Laboratory diagnosis:Laboratory diagnosis:

Specimens collectedSpecimens collected: Urine, blood, pus &: Urine, blood, pus &exudates.exudates.

Methods of examinationMethods of examination::

1. Direct microscopy- by doing Gram’s 1. Direct microscopy- by doing Gram’s smear.smear.

2. Culture- Blood agar and MacConkey’s 2. Culture- Blood agar and MacConkey’s agar is agar is

used.used.

3. Colony morphology-3. Colony morphology-

i) On blood agar small non-haemolytic i) On blood agar small non-haemolytic coloniescolonies

are seen but some strains may show are seen but some strains may show αα or or ββ

haemolysis.haemolysis.

ii) On MacConkey’s agar it produces pinkii) On MacConkey’s agar it produces pink

colour colonies.colour colonies.

4. Identification-4. Identification-

i)i) Gram’s smearGram’s smear

ii)ii) Catalase test- NegativeCatalase test- Negative

iii) Biochemical tests-iii) Biochemical tests- It ferments mannitol, sucrose & It ferments mannitol, sucrose &

sorbitol.sorbitol. Bile esculin test- positiveBile esculin test- positive

+-

Treatment:Treatment:

Strains resistant to penicillin & other Strains resistant to penicillin & other antibiotics occur frequently.antibiotics occur frequently.

Vancomycin is the alternative drug to Vancomycin is the alternative drug to penicillin.penicillin.

Vancomycin resistant is also seen.Vancomycin resistant is also seen.

THANK YOU