Streptococcus Notes

NOTES NOTES STREPTOCOCCUS MICROBE OVERVIEW Morphology ▪ Spherical, Gram-positive bacteria; appear in chains/pairs; catalase, coagulase negative ▪ Produce extracellular substances (e.g. cytolysins, enzymes) → enhance pathogenicity STREPTOCOCCUS AGALACTIAE (GROUP B STREP) osms.it/streptococcus-agalactiae PATHOLOGY & CAUSES ▪ AKA Group B Streptococcus (GBS) ▪ Encapsulated, facultative anaerobe ▪ Colonizes human genital, gastrointestinal (GI) tracts; upper respiratory tracts of young infants ▪ Beta-hemolytic ▫ Blood agar plates, hemolysins degrade lipid membranes → colonies surrounded by narrow zone of hemolyzed cells → complete (beta-)hemolysis Virulence factors ▪ Complex capsular polysaccharides ▫ Inhibit complement deposition on microbe surface components ▪ Hypervirulent GBS adhesin (HvgA) ▫ ↑ ability to invade blood-brain barrier ▪ Cluster of virulence responder/sensor (CovR/S) mutation ▫ Accelerate failure of amniotic barrier → ↑ ability to penetrate chorioamniotic membranes ▪ Pilins ▫ Act as adhesins → ↑ ability to invade central nervous system, form biofilm 552 OSMOSIS.ORG ▪ Direct cytotoxicity to host phagocytes Common infectious agent ▪ Adults (nonpregnant) ▫ Broad spectrum of infections ▪ Pregnant individuals ▫ Chorioamnionitis ▪ Neonates ▫ GBS infection, sepsis RISK FACTORS ▪ Adults (nonpregnant) ▫ Chronic disease (e.g. diabetes, liver disease, malignancy; > age 65, esp. residents of nursing homes) ▪ Pregnancy ▪ Neonates ▫ Ascending infection from mother (e.g. rupture of membranes, chorioamnionitis) ▪ Hospitalization ▫ Nosocomial/hospital-acquired infections

Chapter 99 Streptococcus COMPLICATIONS ▪ Cystitis, pyelonephritis, urethritis, prostatitis; osteomyelitis, septic arthritis; endocarditis; meningitis; pneumonia; sepsis; toxic shock-like syndrome ▪ Neonates ▫ Preterm birth, bacteremia, sepsis, pneumonia, meningitis, neonatal mortality SIGNS & SYMPTOMS ▪ Fever, chills; malaise; cough ▪ Local tissue infection ▫ Red, warm, swollen, presence of drainage ▪ Hippurate hydrolysis test ▫ Detections hippurate hydrolysis by GBS OTHER DIAGNOSTICS ▪ Clinical history, physical examination TREATMENT MEDICATIONS ▪ Antibiotics (e.g. penicillin G, ampicillin) OTHER INTERVENTIONS ▪ Prenatal screening DIAGNOSIS LAB RESULTS Identification of microbe ▪ E.g. blood, cerebrospinal fluid ▪ Gram stain, characteristic morphology ▪ Culture ▫ Beta-hemolysis on blood agar ▪ CAMP test ▫ Identifies presence of CAMP factor ▪ Latex agglutination tests ▫ Detects antibodies produced in response to GBS Figure 99.1 The three classes of streptococcus cultured on a blood agar plate. Alpha (left) shows partial hemolysis, beta (centre) shows complete hemolysis and gamma (right) shows no hemolysis. STREPTOCOCCUS PNEUMONIAE osms.it/streptococcus-pneumoniae PATHOLOGY & CAUSES ▪ Causative agent for numerous clinical syndromes in children, older adults ▪ Alpha-hemolytic, lancet-shaped diplococci ▪ Lysis by bile (deoxycholate), optochin sensitive ▪ Fastidious; prefers 5% carbon dioxide ▪ Pyogenic ▪ Virulence factors ▫ Resistance to phagocytosis (conferred by 92 polysaccharide serotypes) ▫ Adherence proteins ▫ Biofilm formation ▫ Pneumolysin toxin ▪ Asymptomatic colonization → direct spread from site of colonization,hematogenous spread → clinical syndromes OSMOSIS.ORG 553

▪ Typical infections caused by S. pneumoniae range from mucosal to invasive diseases ▫ Meningitis ▫ Otitis media ▫ Pneumococcal community-acquired pneumonia ▫ Sinusitis RISK FACTORS ▪ Age (< 2, ≥ 65 years) ▪ Underlying disease (e.g. liver, kidney, heart, lung, diabetes, malignancies) ▪ Crowded conditions (e.g. daycare centers, military camps, prisons) ▪ Immunodeficiency (e.g. HIV, genetic immune defects, solid organ/bone transplant) ▪ Smoking, alcohol abuse COMPLICATIONS ▪ Pneumococcal endocarditis, empyema, bacteremia, sepsis SIGNS & SYMPTOMS ▪ Common clinical presentation ▫ Fever, altered mental status, malaise ▪ Typical findings related to clinical syndrome ▫ Meningitis: headache, neck stiffness ▫ Otitis media: ↓ tympanic membrane mobility/bulging membrane, otorrhea, pain ▫ Pneumonia: cough, bronchial breath sounds, rales ▫ Sinusitis: purulent rhinitis, mucous membrane edema, headache 554 OSMOSIS.ORG DIAGNOSIS DIAGNOSTIC IMAGING Chest X-ray ▪ Infiltration, consolidation (pneumonia) LAB RESULTS Identification of organism ▪ Gram-positive diplococci, positive culture, polymerase chain reaction (PCR) ▪ Urine antigen analysis (bacteremia) OTHER DIAGNOSTICS ▪ Clinical history, physical examination TREATMENT MEDICATIONS ▪ Antibiotics ▫ Pneumonia: beta-lactam antibiotic ▫ Otitis media: amoxicillin-clavulanate (children) ▫ Sinusitis: amoxicillin (amoxicillin– clavulanic acid may be preferable) OTHER INTERVENTIONS Prevention ▪ Pneumococcal vaccine

Chapter 99 Streptococcus STREPTOCOCCUS PYOGENES (GROUP A STREP) osms.it/streptococcus-pyogenes PATHOLOGY & CAUSES ▪ AKA Group A Streptococcus (GAS) ▪ Colonizes human skin, mucous membranes ▪ Cell-wall structure ▫ Peptidoglycan backbone + lipoteichoic acid components → structural stability ▪ Beta-hemolytic ▫ Blood agar plates, hemolysins degrade lipid membranes → colonies surrounded by clear zone of hemolyzed cells → complete (beta-) hemolysis ▪ Primarily infects skin, soft tissue Virulence factors ▪ Vary with specific strain ▪ M proteins ▫ Protect microbe from humoral immune surveillance, phagocytosis by polymorphonuclear leukocytes ▪ Binding proteins ▫ Bind to IgG, IgM, IgA → may interfere with complement activation ▫ Protein F: binds to fibronectin → ↑ adherence to epithelial surfaces ▪ Cytolysins ▫ Streptolysins: bind to cholesterol on eukaryotic cell membranes → cell lysis ▫ Hyaluronidase: hydrolyzes hyaluronic acid → facilitates infection spread ▫ Streptokinase: proteolytically converts bound plasminogen to active plasmin → cleavage of fibrin; medically useful as clot-busting drug ▫ Nicotinamide adenine dinucleotidase (NADase): exact function unclear; likely ↑ invasiveness ▫ Deoxyribonuclease: promotes production of anti-deoxyribonuclease (DNase) antibody following pharyngeal/ skin infections ▪ Pyrogenic exotoxins (type A, B, C) ▫ Induce fever, act as superantigens → T-cell proliferation → ↑ cytokine production → promotes shock ▪ Streptococcal inhibitor of complement (SIC) ▫ Inactivates complement membrane attack complex ▪ Opacity factor (OF) ▫ Lipoprotein lipase Causative agent in several disorders ▪ Pyogenic diseases ▫ Pharyngitis, cellulitis (abscess formation in dermis, subcutaneous fat layers), necrotizing fasciitis (progressive destruction of deep soft tissue), impetigo ▪ Toxigenic disease ▫ Scarlet fever, toxic shock syndrome, GAS endometritis (puerperal sepsis) ▪ Immunologic disease ▫ Rheumatic fever (antibodies against streptococcal cell cross-react with cardiac tissue); poststreptococcal glomerulonephritis (immune complexes deposited in glomeruli) RISK FACTORS ▪ Susceptible host + encounter with streptococcus expressing specific virulence factors COMPLICATIONS ▪ Local spread (e.g. otitis media, sinusitis, mastoiditis); tissue destruction; valvular, renal disease; sepsis, shock, multiorgan failure; disseminated intravascular coagulation; pediatric autoimmune neuropsychiatric disorder associated with group A streptococci (PANDAS) OSMOSIS.ORG 555

DIAGNOSIS SIGNS & SYMPTOMS ▪ Pharyngitis ▫ Acute onset of sore throat, fever, pharyngeal edema, patchy tonsillar exudates ▪ Cellulitis ▫ Erythema, edema, abscess formation ▪ Impetigo ▫ Papules, vesicles, pustules surrounded by erythema pustules → breaks down, forms crusts ▪ Scarlet fever ▫ Erythematous rash ▪ Toxic shock syndrome ▫ Shock, multiorgan failure ▪ GAS endometritis ▫ Postpartum fever, uterine tenderness LAB RESULTS Identification of microbe ▪ Gram positive cocci ▪ Positive culture ▪ Blood studies ▫ Rapid antigen detection test (RADT) for GAS OTHER DIAGNOSTICS ▪ Clinical history, physical examination TREATMENT MEDICATIONS ▪ Antibiotics (e.g. penicillin G, clindamycin) SURGERY ▪ Surgical debridement STREPTOCOCCUS VIRIDANS osms.it/streptococcus-viridans infections (e.g. abdominal, central nervous system, lung, skin, soft tissue, sepsis) ▫ Abscess formation ▫ Viridans streptococcal shock syndrome PATHOLOGY & CAUSES ▪ Heterogeneous collection of alpha/ nonhemolytic streptococci, cause variety of diseases ▪ Some species produce greenish color on blood agar plates ▪ Not bile soluble, optochin resistant ▪ Approx. 30 species classified into six groups ▪ Part of microbiome of oropharynx, GI, genitourinary tract ▪ May be invasive, produce variety of diseases ▫ Dental caries, periodontal disease, maxillofacial infections, exudative pharyngitis, infective endocarditis ▫ Invades circulation → systemic 556 OSMOSIS.ORG RISK FACTORS Immunocompromised state Periodontal disease More common in children than adults Comorbidities (e.g. mucositis, cystic fibrosis, malignancies) ▪ Altered microbiome ▪ ▪ ▪ ▪ SIGNS & SYMPTOMS ▪ Clinical presentation varies widely depending on infection

Chapter 99 Streptococcus DIAGNOSIS LAB RESULTS Identification of organism ▪ Gram-positive cocci, positive culture OTHER DIAGNOSTICS ▪ Clinical history, physical examination TREATMENT MEDICATIONS ▪ Antibiotics (depending on sensitivity, resistance) ▫ Penicillin + aminoglycoside; broadspectrum cephalosporin, vancomycin SURGERY ▪ Abscess debridement/drainage OSMOSIS.ORG 557