Individual bacteriology

Chapter 14 Coccus

Main contents Biological characterization Pathogenesis and immunity Laboratory diagnosis Treatment and control

Outline 5 pathogenic cocci G+ cocci: Staphylococcus aureus Streptococcus pyogenes Streptococcus pneumoniae G- cocci: Neisseria meningitidis Neisseria gonorrhea ※Biological characteristics ※Pathogenicity

Section 1 Staphylococcus “staphyline” grape-like

Staphylococcus At least 30 species S.aureus: most virulent species. S.epidermidis: opportunistic pathogen. S.saprophyticus: rarely cause human diseases.

Biological characteristics Shape and structure Size: about 1.0 m in diameter Shape: round Arrangement: grape-like Structure: no flagella, can not form spores Staining: G+

Biological characteristics Cultivation Requirements: grow well on basic media facultative anaerobes or aerobes 37℃ pH: 7.4

Biological characteristics Growth properties liposoluble pigments some strains of S.aureus form complete hemolysis (-hemolysis) S.aureus and S.epidermidis

Biological characteristics Biochemical reactions Catalase test “+” Staphylococci: “+” Streptococci: “-” Mannitol Fermentation “+” S. aureus: “+”; S.epidermidis & S.saprophyticus: “-”;

Biological characteristics Antigenic composition Carbohydrate antigens: capsules & teichoic acid Protein antigen: SPA Staphylococcal protein A Characteristics: nonspecific bind to the Fc fragment of IgG

SPA(staphylococcal protein A) IgG Fc receptor Phagocyte BACTERIUM Fab Fc

Biological characteristics Function: virulence factor Anti-phagocytosis; damage platelet; induce hypersensitivity and inflammation; coagglutination test SPA-coated S.aureus is used as Ab carriers

SPA (staphylococcal protein A ) S.aureus Ab

Thermostable nuclease Classification Based on the pigments and chemical reactions Properties S. aureus S. epidermidis S. sarprophyticus Pigment Golden yellow White Citrine Coagulase + － － Mannitol + － － Thermostable nuclease + － － α-hemolysin + － － SPA + － － Pathogenicity strong Weak -

Classification Based on coagulase Phage typing Coagulase” +”: e.g., S. aureus Coagulase” -”: e.g., S. epidermidis & S. saprophyticus Phage typing S. aureus: 4 phage groups, 23 phage types. group Ⅰ: TSST-1-producing strains group Ⅱ: exfoliative toxin-producing strains group Ⅲ: enterotoxin-producing strains ----is of epidemiological value

Resistance to environment Dry Heat high concentration of salt (10-15% NaCl) Sensitivity: basic dyes (crystal violet) several antibiotics (penicillin, vancomycin) MRSA (methicillin resistance S.aureus)

Pathogenicity (S.aureus) Virulence factors Invasiveness Surface structure SPA, capsules Enzyme Toxin---exotoxin Hemolysins Leukocidin Staphylococcal enterotoxin TSST-1 Exfoliative toxin

Enzyme Coagulase: An enzyme that converts fibrinogen in citrated human or rabbit plasma into fibrin causing the coagulation of blood. Classification: Free coagulase Bound coagulase Roles to inhibit the phagocytosis of macrophages and damage of bactericidal substances in body by coating the bacteria with fibrin. Localized infection

fibrin-coated staphylococci

Free coagulase + - tube coagulase test

Bound coagulase slide coagulase test

Other enzymes Staphylokinase: plasminogen---plasmin Heat stable nuclease:degrade DNA and RNA Hyaluronidase (spreading factor) lipase

Exotoxin Hemolysins----staphylolysin Roles: damage membrane permeability; cytotoxic effects on RBC and tissue cells Five kinds:-Lysin (main pathogenic substance) -Lysin -Lysin -Lysin -Lysin S.Aureus in blood agar

leukocidin Increasing membrance permeability Cytotoxic effects on neutrophil and macrophage antiphagocytosis

Staphylococcal enterotoxin 1/2 strains of S.aureus produce it. Produced by S.aureus strains of phage group Ⅲ Chemical and physical characteristics: protein Heat stable (100℃, 30 min) Resistant to proteolytic enzymes of GI tract multiple types: A-E，G-I , K-M superantigen Role: stimulate vomiting-control center and cause a food poisoning characterized by vomiting.

Toxic shock syndrome toxin-1 (TSST-1) Produced by S.aureus strains of phage group Ⅰ superantigen Role: induce fever, shock, hypotension, desquamative skin rash, multisystem involvement; enhance the host susceptibility to endotoxin

Exfoliative toxin---epidemolytic toxin strains of phage-group Ⅱ Superantigen Role: Split desmosomes in stratum granulosum layer of epidermis blister of skin associated with SSSS SSSS: staphylococcal scalded skin syndrome

Pathogenicity Disease Invasive infection/pyogenic infection local infection: folliculitis; boil; carbuncle; impetigo;suppuration of wound (Lesion is limited in local area and pus is thick and yellow) organ infection: pneumonia; meningitis,endocarditis Systemic infection: Septicemia; pyemia Toxin-associated diseases

hair folliculitis boil

folliculitis impetigo carbuncle boil

Pathogenicity Toxin-associated diseases Food poisoning (enterotoxin) TSS (Toxic shock syndrome) SSSS (staphylococcal scalded skin syndrome)

Staphylococcal scalded skin syndrome (SSSS) Most often occurs in infants and young children

Diseases caused by coagulase negative staphylococci(CNS) S.epidermidis urinary tract infection Bacterial endocarditis Septicemia Wound infection S.saprophyticus Community-acquired urinary tract infection

Laboratory diagnosis Specimen Direct smear and Gram stain Isolation and identification Primary criterions: coagulase test, thermostable nuclease gold yellow pigmentation -hemolysis mannitol fermentation Enterotoxin test (animal test) Antibiotic susceptibility tests

pathogenic cocci 3 Genus G+ cocci: Staphylococcus G- cocci: Neisseria S. aureus Streptococcus S. pyogenes S. pneumoniae G- cocci: Neisseria N. meningitidis N. gonorrhea

Section 2 Streptococcus

Biological characteristics Morphology & cultivation properties Spherical, G+, arranged in chains, microcapsule, pili-like structure no flagella, can not form spore Nutritive requirement: high “flesh-eating bacteria”

On blood agar: tiny colony (1-2mm) different hemolysis Most are facultative anaerobe,some are obligate anaerobe catalase negative---distinguish streptococcus and staphylococcus

Biological characteristics Classification Hemolytic activity -hemolytic strep. Incomplete hemolysis Opportunistic pathogens e.g., S.pneumoniae, S.viridans -hemolytic strep. Complete hemolysis() Major human pathogens e.g., S. pyogenes -streptococcus No hemolysis, No pathogenicity e.g., enterococci.

Biological characteristics Antigenic structure Carbohydrate antigen group-specific antigen 20 groups (A~H, K~V) Group A-main human pathogens Protein antigen type-specific antigen M, R, T protein Group A >80 types Cell wall Streptococcus capsule protein Polysaccharide Peptidoglycan

Biological characteristics Resistance Heat labile: 60℃, 30 min Antibiotics sensitivity: penicillin G ,etc.

Pathogenesis(group A streptococcus) Virulence factors Surface structures LTA: adhere to sensitive cell M-protein: a.Anti-phagocytosis b.Be associated with rheumatic heart disease & glomerulonephritis c.Adhere to epithelial cells protein F：receptor of fibronectin on epithelial cell hair like pili

S. pyogenes lipoteichoic acid F-protein fibronectin epithelial cells

Enzymes Pathogenesis Hyaluronidase (spreading factor) Streptokinase (SK) ---myocadial infarction Streptodornase (SD)

Pathogenesis Streptolysin (hemolysin) Toxins---exotoxin Streptolysin (hemolysin) Streptococcal pyrogenic exotoxin (Erythrotoxin, scarlet fever toxin)

Streptolysins streptococci group A, C, and G; Destroy RBC,WBC,platelet Classification: Properties Streptolysin O (SLO) Streptolysin S (SLS) O2 oxygen-labile oxygen-stable Antigenicity Strong (ASO test) Weak Chemical Protein (MW60,000) Polypeptide (28aa)

Anti-SLO Test Definition: a neutralization test or indirect agglutination test between the toxin (SLO) and its specific anti-toxin (ASO) helping to diagnose of recent streptococcus infection and active rheumatic fever. Positive standard: > 250 IU/ml Active rheumatic fever: > 400 IU/ml

Erythrotoxin pyrogenic toxin /scarlet fever toxin Strep. group A (lysogenic) protein Antigenicity A,B,C serotypes Scarlet fever and toxic shock syndrome

Pathogenesis Disease caused by Strep. Group A Transmission: Respiratory tract, trauma, gastrointestinal tract 3 types of infections

Abscess with surrounding cellulitis Types of infections Abscess with surrounding cellulitis Pyogenic infection: Local purulent infections: pharyngitis, tonsillitis; puerperal fever, erysipelas, cellulitis, impetigo;lymphangitis,lymphadenitis Systemic infection: septicemia

Erysipelas Erysipelas on the cheek

Toxin-associated diseases: scarlet fever: Toxic shock syndrome

Types of infections Hypersensitivity type II & III Hypersensitive disease Acute glomerulonephritis edema, hypertension, hematuria and proteinuria Rheumatic fever: involve: heart, joints, subcutaneous tissue, and CNS; fever, migratory polyarthritis, carditis Hypersensitivity type II & III

Prevention and treatment Treat the pharyngitis and tonsillitis in time Antibiotics: penicillin G for the first choice

Section 3 Streptococcus pneumoniae (pneumococcus)

General properties G+, arranged in pairs, bullet shape Capsule: polysaccharide Blood agar , fastidious Facultative anaerobes -hemolysis Autolysis

umbilicus-like colony

Distinguish α-hemolytic streptococcus and streptococcus pneumoniae: Bile solubility test: “+” Fermentation inulin: “+”

Bile solubility test

Antigenic structure Capsular polysaccharide---84 serotypes C polysaccharide---CRP detection Resistance weak

Pathogenesis Virulence factor Capsule Pneumolysin O & Neuraminidase Main disease Lobar pneumonia Meningitis, otitis media, sinusitis bacteriemia, pericarditis, arthritis Immunity Gain type specific immunity afer infection

Lobar pneumonia

Other streptococci Group B streptococci(GBS) Neonatal infections (meningitis,pneumonia,septicemia) Group D streptococci Opportunistic infection---Urinary infeciton,endocarditis,septicemia

α-hemolytic streptococci(viridans streptococci Endocarditis Dental cary

Section 4 Neisseria N. meningitidis N. gonorrhoeae

Common biological characteristics G- coffee bean-shaped or kidney-shaped cocci, in pairs capsules and pili No spore , no flagella aerobic fastidious 5~10%CO2 Resistance: very low

N. meningitidis Pathogenesis Virulence factor: Pili Capsule：13 serogroups (A,B,C---pathogenic to human) Endotoxin Disease: epidemic cerebrospinal meningitis (fever, intense headache, vomiting, stiff neck, coma)

N. Gonorrhoeae /gonococcus Virulence factors Pili IgA1 protease Outer membrane protein (OMP) LPS (endotoxin) Diseases Gonorrhea

Gonorrhea Adults Newborns Transmission: STD (sexually transmitted disease) Clinical disease: Genitourinary tract infection Urethritis, prostatitis; epididymitis (male); cervix inflammation (female); sterility Newborns Ophthalmia neonatorum

Prevention and treatment Penicillin 1%Silver nitrate-- ophthalmia neonatorum

This chapter will focus on Concepts: Pathogenic/Pyogenic cocci SPA ASO test Question: Try to describe pathogenicity of 5 pathogenic cocci (S.aureus, S.pyogenes, S.pneumoniae, N.meningitidis, N.gonorrhea)