Viridans Steptococci andGroups C and G Streptococci

Piyarat rueangbut MD.

*microbiology

*species identification

*epidemiology

*pathogenicity

*clinical manifestations

*therapy

Microbiology

-Facultatively anaerobic , gram-positive cocci.

-Not produce catalase or coagulase on blood agar.

-viridans Latin word viridis “green”

-Partial destruction of erythrocytes with resultant green discoloration on blood agar (α-hemolysis).

-The organisms are nonmotile and non-spore-forming.

-Ferment carbohydrates with acid but without gas production.

Species Identification

-Multiple species of α-hemolytic Streptococci.

-Heterogenous group of organism

- “the human oral viridans streptococci”

Viridans streptococcus

Mutans group-S.mutans-S.rattus-S.cricetus-S.macacae-S.sobrinus-S.downii

Bovis group-S.bovis-S.equinus-S.alactolyticus

Salivarius group-S.salivarius-S.vestibulalaris-S.thermophilus

Mitis group-S.sanguis-S.parasanguis-S.gordoni-S.oralis-S.mitis-S.pneumoniae

Anginosus group-S.anginosus-S.constellatus-S.intermedis

Epidermology

-Normal flora

-URT , female genital tract , GI tract , oral cavity

▪28% - flora from dental plaque. ▪29% - gingival crevices. ▪45% - the tongue. ▪46% - saliva.

-In healthy person “colonization resistance”

Pathogenicity

-Low virulence.

-Not known to possess endotoxin or secrete exotoxins.

-Fully susceptible to lysis by serum and lysosomal enz.

-Extracellular dextran--adherence and propagation.

-FimA-- initial colonization of damaged heart tissue.

-Fibronectin—adherence

-Lipoteichoic acid--adherence

Clinical Manifestation

• Endocarditis

• Bacteremia

• Meningitis

• pneumonia • Miscellanous Infection

Endocarditis

preantibiotic 75% of case of infective endocarditis

current 30-40%

Cause endocarditisS.mitis , S. sanguis , S.mutans , S. salivarius , S.gordonii , s . Oralis

-underlying valvular heart disease-prosthetic valves

sign and symptoms.* insidious onset * subacute but progressive course * fever* constitutional symptoms –fatigue, anorexia,weight

loss* cardiac murmur* splenomegaly* circulating immune complexes-Osler’s node

Endocarditis

Diagnosis*viridans streptococci bacteremia

96% of first blood culture98% of two blood culture

*Echocadiography

identify valvular dysfunction

hemodynamic complications

myocardial abscesses

findings indicate for surgical intervention

Endocarditis

Treatment-prolong penicillin therapy adequately sterilized vegetations-gentamicin lead to more rapid eradcation of the pathogen

Endocarditis

Bacteremia

-2.6% positive blood culture-only 21% clinically significant.-Association

*Aggressive cytoreductive therapy, *acute leukemia*allogeneic bone marrow transplantation *after high-dose cytosine arabinoside

-Risk factor*profound neutropenia*prophylactic Bactrium or fluoroquinolone*use antacid or H2 antagonists* mucositis*increase radiation to oral cavity

Sign and symptom

-fever alone-Organ dysfunction-Fulminant shock syndrome

•hypotension•rash•palmar desquamation•ARDS

Bacteremia

Treatment

-B-lactam ± aminoglycoside-prevent streptococcal bacteremias is controversial.-ampicillin prophylactic failed in bone marrow transplant

Bacteremia

Meningitis

-S.salivarius most common.-S.mitis and S.sanguis-Source –endogenous flora-Neonatal meningitis-perinatallry from mother-Review of viridans streptococcal meningitis(55 case)

-31% ear,nose, throat-13% endocarditis-8% head trauma or neurosurgery-35% illidentifield

Predisposing factors

-gastrointestinal pathology-gastrointestinal manipulation-trauma-ganglionic thermocoagulation-severe immunocompromise after CMT-after lumbar puncture

Meningitis

Sign and symptoms

-all ages , neonates.-typical of acute pyogenic meningitis-meningeal irritation-Neurologic deficits-seizures-altered sensorium

Meningitis

Diagnosis -CSF parameters

*prot. and WBC counts abnormal*glucose normal*positive Gram stain *CSF culture

“Differentiation from S. pneumoniae”

#Review CSF culture -&-hemolytic streptococci 43 pts.19% --clinically relevant.Dx.--clinical setting +CSF laboratory parameters.Contaminants than pathogen

Meningitis

Treatment

-penicillin G 24 Mu / day ( MIC 0.1 ug/ml ) (antibiotic of choice)

-antibiotic resistant viridans streptococci (MIC > 4 ug/ml )

vancomycin plus 3nd generation cephalosporin

Meningitis

Pneumonia

-normal oral flora-if culture from lower respiratory tract specimens, trantracheal aspiration , protected bronchial brush

“aspiration pneumonia syndrome”

-Predisposing host factors*older ( 49-80 yr.)*multiple underlying conditions*alcoholism*lung carcinoma* DM

-Prognosis– primary viridans streptococcal pneumonia

“ good”

-treatment –penicillin G

Pneumonia

Miscellaneous infection

•localized purulent collections asso. S.milleri group

•pericarditis

•peritonitis

•acute bacterial sialadenitis

•orofacial odontoenic infection

•endophthalmitis

•upper respiratory tract infection(otitis media , sinusitis)

Therapy

In the past-viridans group streptococci-susceptible to most antibiotic

1993-1994-44% susceptible to penicillin-Resistance –nosocomial blood-stream

-immunocompromised pt.-98 nosocomial blood stream

-61% susceptible penicillin- <43% susceptible penicilin

(neutropenic cancer pt.)

Resistance latter group.-antimicrobial prophylaxis with cancer chemotherapy.

Community

-remaining of susceptible to penicillin

-1986-> review->endocarditis•2 of 31 viridans streptococcal-> penicillin resistant.•penicillin prophylaxis children with rheumatic fever î number of penicillin resistant strains.

-some strains->exhibit a high level of resistanceto penicillin

Therapy

-USA high-level penicillin resistance 5-13%• non-B –lactamaseproducing• posses altered penicillin binding proteins.

-Species – least sensitive •S.mitis

•S.sanguis

Therapy

Tolerance

-Animal model of endocarditis•tolerance stains -> eradicated more slowly

from vegetation than non tolerance strain

-most -> S. sanguis and S. gordonii

-minority -> S.mitis

-No clinical significance -> attached to tolerance

-Relapse after 4 wks. course of high-dose parenteral penicillin -> rare not been asso. with tolerance in the pathogen

Other B-lactum ATB .

-In vitro เหมื�อน ๆ กับ penicillin

Community-acquired endocarditis

Ceftriaxone – inh. 100% of 20 endocarditis strain at concentration 2.0 ug/ml or less- 80% (16 strain) susceptible to 0.25 ug/ml or

less

Hospitalized or neutropenic cancer pt.

Ceftriaxone- less activity- 15-23 % resistance- high level resistance to penicillin (MIC > 4

ug/ml)

Therapy

Aminoglycosides – viridans streptococci are resistant - synergistic bactericidal activity

(penicillin+aminoglycosides)

Streptomycin – MIC 1000 ug/ml or greater

In vitro

-good activity against viridans streptococci• chloramphenicol•vancomycin•fluoroguinolones •ofloxacin•sparfloxacin•levofloxacin

*neutropenic cancer pt.+prophylaxis quinoloneHigh level resistance

-Variable activity -25-50% reported resistant•Tetracycline•Clindamycin•Erythromycin

-most-strains of viridans streptococci are resistant•Trimethoprim-sulfamethoxazole

Nutritionally variant of viridans streptococi (NVS) (Abiotrophia)

-described 1961 – fastidious gram-positive bacteria -grow as satellite colonies around other

bacteria

-originally -endocarditis-otitis media

-Mutant subspecies of S. mitis (S.mitior)

-Evidence for similarity between NVS and S.mitis

DNA-DNA hybridization studies พบว่�า-NVS -> streptococcus แต่� taxonomically unrelated

viridans group อ��น ๆ-name-> S.adjacens and S. defectivus-กัารศึ�กัษาต่�อมืาพบว่�า ทั้�ง 2 ต่ว่ไมื� relate กับ streptococcus ต่ว่อ��น ๆ เลย

-1995 -> new genus -> Abiotrophia ->A.adjacens , A.defectiva

•resistant to optochin•susceptible to vancomycin

-Colonies -non hemolysis-or &-hemolysis

-Normal flora -upper respiratory-urogenital-gastrointestinal tract

Historically-NVS มืกัพบใน case culture negative endocarditis-endocarditis caused by NVS greater morbidity and motality > other streptococci

-Comparison -49 NVS endocarditis -130 other oral species

-แต่�ถ้ าเทั้!ยบกัน NVS กับ viridans streptococc

TherapyIn vitroPenicillin – NVS less susceptible to penicillin

(MIC 0.2-2.0 ug/ml)

Aminoglycosides-NVS variable in activity against

(MIC 0.5-32 ug/ml)

Therapy

-synergy ระหว่�าง penicillin or vancomycin กับ aminoglycosideพบว่�า

-penicillin + low dose gentamicin superior penicillin + low dose streptomycin

NVS -> susceptible•vancomycin •erythromycin•clindamycin •rifampin+vancomycin•chloramphenicol

NVS-> variable•cephalosporin•tetracycline

-NVS in other disease is unknow(grow poorly on solid media)

-NVS ถ้#กั reported ใน*pancreatic abscess*otitis media*conjuctivitis*infectious crystalline keratopathy*cirrhosis*postpartum and postabortal sepsis

ß-hemolytic streptococci (group C and G)

Microbiology

-Group C streptococci-common pathogens in domestic animal, bird,

rabbit-bacitracin resistance-four species Streptococcus dysgalactiae

•uncommon in human•mastitis in cows and suppurative polyarthritis in lambs•not streptolysin O or S

Streptococcus equisimilis•most common cause infection in humans•produces streptokinase and streptolysin O but not streptolysin S•throat , nose , genital tract, umbilicus•domestic animal

Streptococcus zooepidermicus•infection in domestic animal•human infection->traced to animal source•not streptolysin O or S ,streptokinase

Streptococcus equi•pathogen of young horses•not streptolysin O or S , streptokinase

Microbiology

-Group G streptococci•B-hemolytic streptococcal•produce streptolysin similar to streptolysin O by group A B-hemolytic streptococci

Microbiology

Epidemiology

Group C streptococci-normal human flora •nasopharynx

•skin •genital tract •umbilical in newborns •puerperal vaginal

-colonized in many animal

-Infection in humans –traced to animal sources -underlying condition

*Review 31 case –group C streptococal infection

-26% cardiopulmonary disease

-20% DM

-20% chronic dermatologic condition

-19% immunosupression

-13% alcohol abuse

-10% renal or hepatic failure

-6% injection drug use

Review 88 case -group C streptococcal bacteremia

-73% underlying --20% cardiovascular dis. --20% malignancy

-24% exposure to amimal

Epidemiology

Group G streptococci

-colonized – nasopharynx - skin - genital tract - intestinal

-Group G streptococal infection -65 % underlying malignancy

Review 57 case – group G streptococcal infection

-21 % underlying malignancy

-21 % alcohol use

-14 % DM

Clinical Manifestations

-suppurative infection of various organ

-endogenous – organism residing on skin or mucous membranes

neonate , elderlyalcoholisminjection drug abuseDMimmunosuppressive therapy with corticosteroid or cytotoxic drugsunderlying malignancy

**severe resembling groups A and B ß-hemolytic streptococci

-exogenous – animal sources

Pharyngitis

Sign and symptoms

-group C streptococci pharyngitis similar group A ß-hemolytic streptococci

-fever

-mild to moderate sore throat

-pharyngeal exudate

-cervical adenopathy

-severe pharyngitis followed by bacteremia , metastatic infection

-group G streptococci –asymptomatic pharyngeal carriage -mild upper respiratory tract infection

-exudative pharyngitis with fever

-lymphadenopathy

Pharyngitis

Complications of pharyngitis

-Poststreptococcal glomerulonephritis asso. Group C

-acquired by unpasteurized milk from cattle with mastitis

-S.zooepidemicus

-No ASO antibody titer response

-pathogenesis is unclear

- Group G streptococcal pharyngitis asso. with sterile reactive arthritis

Skin and soft tissue infection

-cellulitis , wound infection , pyoderma , erysipelasimpetigo , cutaneous ulcers.

-Group C –cellulitis after vein harvest for coronaryArtery bypass grafts

-Group G streptococcal bacteremia -skin and softTissue infection ( underlying malignancy)

Arthritis

-Group C streptococcal arthritis ->joints with preexistingrheumatologic abnormalities , polyarthritis

-Group G streptococcal -> prosthetic joints.

Osteomyelitis

-Group G -> underlying condition(malignancy , alcoholic cirrhosis , osteoarthritis ,internal fixation for fracture , prosthesis )

Respiratory tract infection

-Group C - uncommon cause of pneumonia - preceded by viral URI

-Group G - rare -underlying malignancy

Endocarditis-Groups C and G streptococci is uncommon

-Group C streptococcal endocarditis•subacutely•major emboli to CNS , eye , limb , lung•poorly response to single B-lactam•favor use bactericidal combination (penicillin plus gentamicin)

-Group G streptococcal endocarditis•older pt. with multiple underlying disorders•affect to both native and prosthetic valves•left sided more common•abrupt onset with rapid valve destructon and perivalvular infection•B-lactam plus aminoglycoside at least 28 days.

Meningitis

-Groups C and G streptococcal meningitis asso. with infective endocarditis.

-occur in healthy patients– equine zoonosis- ingestion of unpasterized goat ‘s milk

-Group C streptococci- CSF in a preterm infant-> mother receivedintrapartum antimicrobial therapy for chorioamnionitis.

Puerperal infection

-Groups C and G streptococci asso. epidemic and nonepidemic puerperal sepsis and endometritis

Neonatal Sepsis-Group G streptococci neonatal sepsis

•premature•low birth weight infants•premature rupture membranes•onset –within the first week of life•asso.-high incidence of maternal obstetric complication

Miscellaneous infection

-Group C streptococcal-pericarditis-pyomiositis in AIDS-Henoch schonlein purpura-brain abscess , subdural empyema-epiglottis-infected arteriovenous fistular-peritonitis in dialysis pt.

-Group G streptococcal-spinal epidural abscess-brain abscess in HIV-panophthalmitis

-toxic shock like syndrome asso. – both groups

Therapy

Group C streptococcai

-drug of choice -> penicillin G

-Good activity-> cefazolin , vancomycin , cefotaxime

-variable -> tetracycline

-resistant -> erythromycin

-synergy -> penicillin plus gentamicin(recommend for pt. with severe infection)

Group G streptococci

-Good activity-> penicillin , ampicillin , cefotaxime vancomycin ,cephalosporins

-Relatively poor activity -> clindamycim , chloramphenicol

erythromycin

-synergy -> gentamicin with either penicillin cefotaxime vancomycin

against 80-90%

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