Streptococcus

Streptococcus

·         Gram (+) cocci arranged in pairs or chains

·         Spherical to ovoid

·         Generally non-motile except few strains of Group D

·         Generally non-encapsulated but members of groups A,B,C and D are encapsulated

·         Non-sporeformers

·         Facultative anaerobes requiring ↑ CO2

·         Catalase (-)

·         Reduce nitrate to nitrite

Viridans group and Streptococcus pneumoniae

All species have C carbohydrate in their cell wall except _____

blood or enriched media

Streptococcus requires ____ for isolation

Smith & Brown Classification

Hemolytic Patterns on BAP

\
Based on hemolysis

Beta Hemolytic Group

Streptococcus hemolyticus group

Beta Hemolytic Group

·         Complete lysis of RBC around the colony

·         Clear, colorless area around the colony

·         Streptococcus pyogenes

·         Streptococcus agalactiae

Beta Hemolytic Group

Alpha Hemolytic Group 

·         Green Streptococci

·         Partial lysis or incomplete hemolysis of RBC around the colony

·         Greenish or brownish discoloration of area around the colony probably due to methemoglobin

·         Forms long chains especially when grown in liquid media

·         Streptococcus pneumoniae

·         Viridans Group

Alpha Hemolytic Group 

Gamma Hemolysis / Non-hemolytic

No lysis of RBC around the colony

·         The Indifferent Streptococcus

·         No change observed in the agar around the colony

·         Streptococcus faecalis

Gamma Hemolysis / Non-hemolytic

Alpha-prime / Wide Zone

Small area of intact RBC surrounded by a wider zone of complete hemolysis

Pyogenic Group

Pus forming organisms

·         Mostly β-hemolytic

·         Majority of Lancefield groups

·         Grows at neither 45°C nor at 10°C

Lactic Acid Group

Grows at 10°C but not at 45°C

·         Harmless group of Streptococcus

·         Associated in dairy industry, pickles

Streptococcus lactis

·         responsible for souring of milk

Viridans Group

Grows at 45°C but not at 10°C

·         Normal flora of the oral cavity

·         Cause of Sub-Acute Bacterial Endocarditis (SBE)

Enterococcus Group

Grows at 45°C and at 10°C

·         Normal fecal flora

·         Currently considered as a new genus

Enterococcus faecalis

·         used as an indicator in water pollution

Lancefield Classification

Based on the presence of a serologically active CHO known as C-Polysaccharide group specific CHO Ag

Streptococcus pyogenes

Group A Streptococci

·         Predominantly pathogenic to man

·         Almost always β-hemolytic

M Protein

Resistance to phagocytosis and adherence to mucosal cells 

·         Principal virulence factor of S.pyogenes

Streptolysin O

Oxygen labile; active only in reduced form or anaerobic condition

·         Responsible for sub-surface hemolysis

·         Highly antigenic; Anti-Streptolysin O (ASO) indicates recent infection with S. pyogenes

·         Lyses leukocytes, platelets and RBC

Streptolysin S

Oxygen stable; responsible for hemolysis when incubated aerobically

·         Surface hemolysis

·         Non-antigenic

Streptodornase

Used to liquefy exudates

Erythrogenic Toxin / Pyrogenic Toxin

Three types of toxins (A, B, C)

\
Responsible for redness and the spreading rash in scarlet fever

1/3

__ of those with sore throat have a throat culture (+) for S. pyogenes

1-4 days

IP Strep throat

Strep Throat

Manifests as sore throat, malaise, fever, headache, inflamed tonsils and pharynx, swollen and tender cervical lymph nodes

\
Definitive Diagnosis relies on a throat culture

Impetigo

localized skin disease

·         small vesicles that progress to weeping lesions

·         Seen in children 2-5 years old

Erysipelas

Infection of the skin and subcutaneous tissue

·         Erythematous lesion

·         Seen in elderly patients

Cellulitis

Develops following deeper invasion by Streptococci

·         Life-threatening

·         With bacteremia or sepsis present

Scarlet Fever

Red rash appears on the upper chest, spreads to the trunk and extremities associated with erythrogenic toxin

DICK’S TEST

Susceptibility Test for Scarlet Fever

0\.1 ml.

DICK’S TEST uses ___. Dick’s Toxin & _ Dick’s Toxoid

·         area of erythema/redness and edema

DICK’S TEST (+)

SCHULTZ-CHARLTON RXN/NEUTRALIZATION RXN / BLANCHING PHENOMENON

Based on the neutralization of erythrogenic toxin when an antitoxin is injected into the skin of patient with a scarlet fever

·         Used to diagnose skin rashes whether skin rashes are due to scarlet fever

·         rashes fade / blanch

SCHULTZ-CHARLTON RXN/NEUTRALIZATION RXN / BLANCHING PHENOMENON (+)

Rheumatic Fever

Complication of S. pyogenes pharyngitis

\
·         Fever, inflammation of the heart, joints, and blood vessels; most serious result is progressive damage to the heart valves

\
·         Attacks begin within a month after infection; repeated infections may produce further valve damage

Acute Glomerulonephritis (AGN)

May occur after a cutaneous or pharyngeal infection

\
·         More common in children than adults 

Serologic Typing

S.pyogenes definitive ID

·         PENICILLIN

S.pyogenes drug of choice

·         ERYTHROMYCIN

S.pyogenes drug of choice for allerrgic to penicillin

Streptococcus agalactiae

\- Group B Streptococci

·         Three (3) Serotypes based on capsular polysaccharides (I, II, III)

·         Etiologic agent of bovine mastitis in animals

·         In human, normal flora of the URT, GIT, GUT

Early Onset Infection

Within 3 days after birth

\
·         Usually manifests pneumonia or meningitis with bacteremia

Late Onset Infection

Between 1 week and 3 months after birth

\
·         Usually meningitis

Enterococcal Group, Non-Enterococcal Group

Group D Streptococcus

Previously subdivided into two groups:

Enterococcal Group

Now placed in a new genus ENTEROCOCCUS

Non-Enterococcal Group

Remained part of the Group D Streptococci

\
S. equinus and S. bovis

\
Non-Enterococcal isolate but is found in the intestinal tract

\
Bacteremia has been associated with gastrointestinal tumor

·         Penicillin

Group D Streptococcus Treatment

Group D Streptococcus

Culture - Alpha or Beta or non hemolytic on BAP

·         *Group D Streptococcus Enterococcus* group

Enterococcus is previously known as

Enterococcus

·         Found in intestinal tract

·         Clinical Infections: same as Group D

·         E. faecalis

·         E. faecium

·         E. durans

Enterococcus samples

·         Diplococcus pneumoniae /Pneumococcus Encapsulated

Streptococcus pneumoniae is also known as

Streptococcus pneumoniae

·         Non-motile

·         Facultative anaerobes

·         Non-sporeformers

rusty – brown sputum

Lobar pneumonia color of sputum

Specific Soluble Substance (SSS)

Polysaccharide capsular substance which determines both the virulence and capsular type

Somatic Ag / O Ag

 Present in the cell wall

·         Binds with C-Reactive CHON (CRP)

·         CRP: ↑ in patients with acute inflammatory diseases

S.pneumoniae

lancet-shaped

Francis Test

Skin test done to determine the presence or absence of Ab against Pneumococcal Ag

Neufeld Quellung Reaction - Capsular Precipitation Rxn / Capsular Swelling Test

·         In glass slide, Mix a loopful of sputum and anti-pneumococcal serum + Methylene Blue

·         (+) result: capsules appear swollen due to a change in refractive index

Viridans Streptococci

·         Lack Lancefield Group Ag

·         Does not meet the criteria for S. pneumoniae

·         Oropharyngeal commensal but opportunistic pathogen

GROUP C STREPTOCOCCI

Primary animal pathogens

Streptococcus equisimilis

in human

Streptococcus equi

in horses

Streptokinase

·         Used in thrombolytic therapy in humans

·         Hydrolyzes thrombus (clot)

Genus Abiotrophia

Formerly known as *Nutritionally – Variant Streptococci / Pyridoxal - dependent / Vitamin B6 – dependent / Thiol-dependent / Symbiotic Streptococci*

\
·         They satellite around colonies of organism that produces pyridoxal: Staphylococci, E. coli, Klebsiella spp., Enterobacter and yeasts

\
·         Gram (+) cocci

\
·         maybe gram (-), variable and pleomorphic

·         Part of the normal oral flora but can cause endocarditis, otitis media and wound infections

pyridoxal

Genus Abiotrophia use

Micrococcus

·         Gram (+) cocci in tetrads

·         Aerobic

·         Catalase (+)

·         Non-motile

Micrococcus

·         Not pathogenic

·         Skin colonizers

·         Occasionally associated with skin lesions

·         More commonly isolated from immunocompromised patients

·         Unknown virulence factor; probably of extremely low virulence

·         Usually considered contaminants of clinical specimens

·         Rarely implicated as cause of infections in humans

yellow orange or red

Micrococcus is usually what color

·         Staphylococci

Micrococcus is easily confused with