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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