Lecture 6 Microbiology 21-10-22 PDF

Lecture 6 Cocci 1  Content Staphylococci (pyogenic cocci and coagulase-negative staphylococcus) Morphology, culture, and biological characteristics of Staphylococcus aureus The virulence factors of Staphylococcus aureus and their ef...

Lecture 6 Cocci 1  Content Staphylococci (pyogenic cocci and coagulase-negative staphylococcus) Morphology, culture, and biological characteristics of Staphylococcus aureus The virulence factors of Staphylococcus aureus and their effects ( including SPA, coagulase, hemolysin, and enterotoxin) The diagnostic laboratory tests for Staphylococcus aureus and the principles of controlling Staphylococcus infections Streptococcus (classification) Morphology, culture, and biological characteristics of Streptococcus The virulence factors of group A streptococcus, the pyogenic and non- pyogenic infections caused by group A streptococcus, diseases caused by group B, D streptococcus and enterococcus (streptolysin, pyrogenic exotoxin, invasive enzymes) The diagnostic laboratory tests for streptococcus and pneumococcus; antistreptolysin O test (ASO test) Neisseria Classification of Neisseria (Neisseria meningitides and Neisseria gonorrhoeae) The biological characteristics and pathogenicity of - and immune response to - Neisseria meningitides Principles of diagnostic laboratory tests, and principles of prevention and treatment of the diseases caused by Neisseria meningitides Neisseria gonorrhoeae and infection 2  Classification Family: Micrococcaceae Genus: o Staphylococcus o Micrococcus Species: S. aureus S. saprophyticus S. epidermidis More than 20 species: Micrococcus luteus, etc. 3  Staphylococcus Sir Alexander Ogston, a Scottish surgeon, first showed in 1880 that a number of human pyogenic diseases were associated with a cluster-forming micro-organism. He introduced the name staphylococcus (Greek: staphyle = bunch of grapes; kokkos = grain or berry), Alexander Ogston now used as the genus name for a group of facultatively anaerobic, catalase-positive, Gram- positive cocci. 4  Genus Staphylococcus The genus Staphylococcus contains about forty species and subspecies today. Only some of them are important as human pathogens: Staphylococcus aureus Staphylococcus epidermidis Staphylococcus hominis Staphylococcus haemolyticus Staphylococcus saprophyticus other 5  Structure and physiology Gram-positive cocci, nonmotile, facultative anaerobes. Cells occur in grapelike clusters because cells division occurs along different planes and the daughter cells remain attached to one another. Salt-tolerant: allows them to tolerate the salt present on human skin. Tolerant of desiccation: allows survival on environmental surfaces (formites). 6 Staphylococcus aureus - Morphology Polysaccharide capsule is only rarely found on cells. The peptidoglycan (murein) layer is the major structural component of the cell wall. It is important in the pathogenesis of staphylococcal infections. Other important component of cell wall is teichoic acid. 7  Peptidoglycan Half of the cell wall by weight is peptidoglycan, a feature common to gram-positive bacteria. The subunits of peptidoglycan are N-acetylmuramic acid (NAM) and N-acetylglucosoamine (NAG). Unlike gram-negative bacteria, the peptidoglycan layer in gram-positive bacteria consists of many cross-linked layers, which makes the cell wall more rigid. 8  Protein A Protein A is the major protein component of the cell wall. It is located on the cell surface but is also released into the culture medium during the cell growth. A unique property of protein A is its ability to bind to the Fc part of all IgG molecules except IgG3. It is not an antigen-antibody specific reaction. The surface of most S. aureus strains (but not the coagulase-negative staphylococci) is uniformly coated with protein A. The presence of protein A has been exploited in some serological tests, in which protein A-coated S. aureus is used as a nonspecific carrier of antibodies directed against other antigens. Additionally, detection of protein A can be used as a specific identification test for S. aureus. 9 Protein A binding 10 11  Teichoic acid Teichoic acid is species-specific, phosphate- containing polymers that are bound covalently to the peptidoglycan layer or through lipophilic linkage to the cytoplasmic membrane (lipoteichoic acid - LPA). Teichoic acid mediates the attachment of staphylococci to mucosal surfaces through its specific binding to fibronectin. 12  Coagulase and other surface proteins The outer surface of most strains of S. aureus contains clumping factor (also called bound coagulase). This protein binds fibrinogen, converts it to insoluble fibrin, causing the staphylococci to clump or aggregate. Detection of this protein is the primary test for identifying S. aureus 13  Coagulase binding test Coagulase - cause blood to coagulate Blood clots protect bacteria from phagocytosis from WBC’s and other host defenses. Staphylococci - are often coagulase positive Negative The genus Staphylococcus can be divided into two subgroups (on the basis of its ability to clot blood plasma by enzyme coagulase): coagulase-positive: Staphylococcus aureus coagulase-negative: oStaphylococcus epidermidis, o Staphylococcus hominis, o Staphylococcus haemolyticus, o Staphylococcus saprophyticus, o Staphylococcus simulans, o Staphylococcus warneri o other 14 Positive  Other surface proteins Other surface proteins that appear to be important for adherence to host tissues include: collagen-binding protein elastin-binding protein fibronectin-binding protein 15  Capsule Capsule or polysaccharide slime layer A loose-fitting, polysaccharide layer (slime layer) is only occasionally found in staphylococci cultured in vitro, but is believed to be more commonly present in vivo. Eleven capsular serotypes have been identified in S. aureus, with serotypes 5 and 7 associated with majority of infections. 16  Capsule Capsule helps Staphylococcus. The capsule protects the bacteria by inhibiting the chemotaxis and phagocytosis of staphylococci by polymorph nuclear leukocytes (PNL), as well as by inhibiting the proliferation of mononuclear cells. It is also facilitates the adherence of bacteria to catheters and other synthetic materials. 17  Cytoplasmic membrane The cytoplasmic membrane is made up of a complex of proteins, lipids, and small amount of carbohydrates. It serve as an osmotic barrier for the cell and provides an anchorage for the cellular biosynthetic and respiratory enzymes. 18  Enzymes Staphylococcal enzymes: Coagulase Catalase Hyaluronidase Fibrinolysin Lipases Nuclease Penicillinase 19  Role of Enzymes 1. Coagulase – Triggers blood clotting 2. Hyaluronidase – Breaks down hyaluronic acid, enabling the bacteria to spread between cells 3. Staphylokinase (Fibrinolysin) – Dissolves fibrin threads in blood clots, allowing Staphylococcus aureus to free itself from clots 4. Lipases – Digest lipids, allowing staphylococcus to grow on the skin’s surface and in cutaneous oil glands 5. β-lactamase – Breaks down penicillin – Allows the bacteria to survive treatment with β-lactam antimicrobial drugs 20 21 22  Staphylococcal toxins S. aureus produces many virulence factors, including at least five cytolytic or membrane-damaging toxins: alpha toxin =alpha hemolysin-pore forming toxin lyses membrane, it is inactive against neutrophils beta toxin delta toxin Cytotoxic gamma toxin factors Panton-Valentine toxin =kleucocidin – pore forming toxin – causes tissue necrosis, active against neutrophils. two exfoliative toxins eigth enterotoxins (A-E, G-I) Toxic Shock Syndrome Toxin 1 (TSST-1) 23  Exfoliative toxins Exfoliatin splits interdermal junctions Exfoliative toxins A and B results in staphylococcal scalded skin syndrome; usually in infants and neonates. Staphylococcal scalded skin syndrome (SSSS), a spectrum of diseases characterized by exfoliative dermatitis, is mediated by exfoliative toxins. The prevalence of toxin production in S. aureus strains varies geographically but is generally less than 5% to 10%. 24  Food poisoning Enterotoxins Eigth serologically distinct staphylococcal enterotoxins (A-E, G-I) and three subtypes of enterotoxin C have been identified. The enterotoxins are stable to heating at 100 C for 30 minutes and are resistant to hydrolysis by gastric and jejunal enzymes. In preformed food heat-resistant enterotoxin mediates staphylococcal food poisoning (symptoms in 2-6 hours; usually self-limiting). Symptoms: nausea, abdominal cramping, vomiting, and diarrhea. Foods particularly effective carriers of bacteria and its toxins: Custard of cream filled bakery food Processed meat, chicken Salads with mayonnes Ice-cream, milk, dairy products 25  Food poisoning Enterotoxins Thus, once a food product has been contaminated with enterotoxin-producing staphylococci and the toxin have been produced, neither reheating the food nor the digestive process will be protective. These toxins are produced by 30% to 50% of all S. aureus strains. Enterotoxin A is most commonly associated with disease. Enterotoxins C and D are found in contaminated milk products, and enterotoxin B causes staphylococcal pseudomembranous enterocolitis. 26 Toxic Shock Syndrome Toxin (TSST) and other Toxins The enterotoxins and TSST-1 belong to a class of polypeptide known as super antigens (SAgs) Non-specific binding of toxin to receptors triggers excessive immune response Staphylococcus aureus strains produce several other extracellular, biologically active substances, including proteases, phosphatases, lipases, lysozyme etc. 27  Toxin-mediated infections Toxic shock syndrome toxin (TSST-1) is a super-antigen (SAg) capable of activating large number of T cells. Was associated with use of tampons but is also known to be associated with postoperative wound or soft tissue infections. The disease is characterized by high fever, vomiting, diarrhea, sour throat and muscle pain. Within 48 h it may progress to severe shock with evidence of renal and hepatic damage. A skin rash may develop, followed by desquamation at a deeper level than in scalded skin syndrome. Blood cultures are usually negative. 28  Toxic Shock Syndrome Toxin - 1 TSST-1, formerly called pyrogenic exotoxin C and enterotoxin F, is a heat and proteolysis resistant, chromosomally mediated exotoxin. The ability of TSST-1 to penetrate mucosal barriers, even though the infection remains localized in the vagina or at the site of a wound, is responsible for the systemic effects of TSS. Death in patients (5%-10%) with TSS is due to hypovolemic shock leading to multi-organ failure. Hypovolemic shock is an emergency condition in which severe blood or other fluid loss makes the heart unable to pump enough blood to the body. This type of shock can cause many organs to stop working. 29  Epidemiology of Staphylococcus aureus Staphylococci are ubiquitous. All persons have coagulase- negative staphylococci on their skin, and transient colonization of moist skin folds with S. aureus is common. Colonization of the umbilical stump, skin and perineal area of neonates with S. aureus is common. S. aureus and coagulase-negative staphylococci are also found in the oro-pharynx, gastrointestinal and uro-genital tract. Because staphylococci are found on the skin and in the naso-pharynx, shedding of the bacteria is common and is responsible for many hospital-acquired infections. 30  Epidemiology Colonizes anterior nares of 20-30% of healthy people Strains with increased virulence can not be distinguished Community infections are endogenoius Hospital spread is on the hands of medical personnel Outbreaks involve nasal carriers or workers with leason S. aureus survives drying 31  Clinical Manifestations The clinical manifestations of some staphylococcal diseases are almost exclusively the result of toxin activity (e.g. staphylococcal food poisoning and TSS), whereas other diseases result from the proliferation of the staphylococci, leading to abscess formation and tissue destruction (e.g. cutaneous infection, endocarditis, pneumonia, empyema, osteomyelitis, septic arthritis). 32  Staphylococcal Diseases Systemic Disease Toxic shock syndrome-TSS toxin is absorbed into the blood and causes shock Bacteremia-presence of bacteria in the blood Endocarditis-occurs when bacteria attack the lining of the heart Pneumonia-inflammation of the lungs in which the alveoli and bronchioles become filled with fluid Osteomyelitis-inflammation of the bone marrow and the surrounding bone 33  Clinical diseases Staphylococcal pyogenic infections: folliculitis, furuncle, carbuncle, bullous impetigo, panaritia and paronychia, wound infections, mastitis, osteomyelitis, staphylococcal pneumonia and other 34  Staphylococcus infections Bullos impetigo - Folliculitis - superficial bubble-like swellings inflammation of hair follicle; that can break and usually resolved with no peel away; most complications but can common in newborns progress Furuncullosis- boil; Carbuncles larger and deeper inflammation of hair lesion created by aggregation follicle or sebaceous gland and interconnection of a cluster Panaritia Stye progresses into abscess or of furuncles 35 pustule  Treatment Antistaphylococcal antibiotics of the first choice: oxacillin (methicillin) cephalosporins of I. generation (cefazolin, cephalotin) Antistaphylococcal antibiotics of the second choice: lincosamides (e.g. clindamycin) glycopeptides (vancomycin, teicoplanin) linezolid tigecyklin daptomycin and others 36  Diagnosis Microscopy – smears of clinical materials are stained according to Gram stain Cultivation on solid media (agar, usually blood agar) Biochemical tests Phage typing – susceptibility of S. aureus strains to various temperature phages 37  Culture of Staphylococcus aureus Colonies on solid media are round, regular, smooth, slightly convex and 2 to 3 mm in diameter after 24h incubation. Most strains show a α-haemolysis surrounding the colonies on blood agar. S. aureus cells produce cream, yellow or orange pigment. 38 Laboratory identification scheme for Staphylococcus 39 Laboratory identification scheme for Staphylococcus 40  Growth of Staphylococcus Staphylococcus species are facultative anaerobic bacteria. All species grow best on nutrient agar and blood agar. Mannitol salt agar is a selective media for Staphylococcus species. It can grow at a temperature range of 15-45 C, and NaCl concentration as high as 15%. 41  Mannitol Salt Agar Not Staphylococcus Staphylococcus aureus S. epidermidis 42  Novobiocin test S. saprophyticus S. epidermidis 43  Resistance of Staphylococcus sp. Like most of medical important non-spore-forming bacteria, S. aureus is rapidly killed by temperature above 60 OC S. aureus is susceptible to disinfectants and antiseptics commonly used. S. aureus can survive and remain virulent long periods of drying especially in an environment with pus 44 Antibiotic sensitivity pattern 45  MRSA Methicillin-resistant S. aureus Resistant to all penicillins, cephalosporins, and imipenems Usually multiply-resistant Vancomycin resistance is very rare – so far Hospital-acquired Community-acquired cases now (CA MRSA) 46  Panton-Valentine Leukocidin Panton-Valentine Leukocidin (PVL) consists of 2 components S and F, together with γ exotoxin lyses WBC resulting in massive release of inflammatory mediators responsible for necrosis and severe inflammation PVL is an important virulence factor in MRSA infections 47 Coagulase-negative staphylococcal spp (CoNS) S. epidermidis – most frequently isolated staphylococcal spp. Colonizes moist body areas such as axilla, inguinal and perianal areas, anterior nares and toe webs Important cause of nosocomial infection esp. S. epidermidis Usually causes nosocomial infections in patients with predisposing factors such as S. epidermidis immunodeficiency/ immunocompromised or presence of foreign bodies 48  Staphylococcus epidermidis Skin commensal Has predilection for plastic material Associated with infection of IV lines, prosthetic heart valves, shunts Causes urinary tract infection in catheterized patients Has variable antibiotic sensitivity pattern Treatment should be aided with antibiotic susceptibility test 49 Infections caused by S. epidermidis Blood stream infection Endocarditis Cerebrospinal fluid (CSF) shunt infection Peritoneal dialysis catheter infection Urinary tract infections, especially with indwelling urinary catheters resulting to urinary tract complications Prosthetic joints infections Infection of vascular grafts Infection among newborns Eye infection after an eye surgery Infection of pacemakers or implantable cardioverter-defibrillators Infection of breast implants 50  Importance of S.saprophyticus Skin commensal S. saprophyticus frequently isolated in rectum and genitourinary tract of young women Can be causative agent in UTI in young healthy women 2nd most common urinary pathogen (other than E. coli) in uncomplicated cystitis in young women Colony counts of ≥ 105 CFU/ml usually indicative of significant Bacteriuria Usually sensitive to wide range of antibiotics 51 Prevention Hand antisepsis is the most important measure in preventing nosocomial infections Also important is the proper cleansing of wounds and surgical openings, aseptic use of catheters or indwelling needles, an appropriate use of antiseptic. 52 Streptococcus 53  Streptococcus sp. Gram positive cocci, occur in pairs and in short chains. None-motile, none- spore formers, some strains are capsulated. Strict anaerobes and facultative anaerobes. Gram positive Catalase negative 54 Streptococcus species are classified according to hemolytic activity. 55  Streptococci Trypticase soy agar culture plate containing 5% sheep’s blood growing group-D Streptococci (left wedge), group-B Streptococci (middle wedge), and group-A Streptococci (right wedge) bacteria. 56 Rebecca Lancelfield’s classification Lancelfield’s antigens are cell wall carbohydrates Group A – rhamnose-N-acetylglucosamine Group B – rhamnose-glucosamine polysaccharide Group C – rhamnose-N-acetylglucosamine Group D – glycerol teichoic acid containing alanine & glucose Group F – glucopyrasonyl-N- acetylgalactosamin Presence of Lancefield antigens defines the pyogenic streptococci Only pyogenic streptococci are β-hemolytic Hemolysis is the practical guide to classification. 57  Classification - Lancefield Lancefield realized that all species in each “group” generally (and conveniently) shared clinically significant properties such as type of hemolysis, normal host, body system or tissue where indigenous, etc. For example: Group A - S. pyogenes: human upper respiratory Group B - S. agalactiae: human urogenital Group C - S. zooepidemicus: from animal products Group D - S. faecalis: bile-resistant, fecal origin 58 Group Common Hemolysis Lencefield Surface Capsule Virulence Diseas term cell wall protein factors Streptococci pyogenic S. pyogenus GrA Strep β A M protein Hyaluronic M protein, Strep acid lipoteichoic throat,im (GAS) acid, go,pyoge StrepSAgs, infection streptolysin toxic sho O,streptokina rheumat se fever,glo lonephri S.agalactae GrBStrep β,- B - Salic acid Capsule Neonata sepsis,m (GBS) (9) itis, pyog infection S.equi β C - - StrepSAg genes Pyogenic infections S.bovis -, α D - - - Pyogenic Other β, α,- E-W - - - Pyogenic species Pneumococcus S.pneumoniae Pneumococcus α - Chlorine Polysaccharai Capsule, Pneumon binding de (90+) pneumolysinn meningitis euraminidase media, py protein 59 infections Group Common term Hemolysis Lencefield cell Surface protein Capsule Virulence Disease wall factors Streptococci Viridans and non-hemolyti c S. sanguis α Low virulence, endocarditis S.salivarius α Low virulence, endocarditis S. mutans α Dental caries Other species α,- Low virulence, endocarditis Enterococci E. faecalis Enterococcus -,α D Urinary tract , pyogenic infections E. faecim Enterococcus -, α D Urinary tract , pyogenic infections Other species -, α D Urinary tract , pyogenic infections 60  S. pneumococcus and S.viridans Pneumococcus have an antigenic polysaccharide capsule Viridans and non-hemolytioc species lack Lancefield antigens or capsules Streptolysin O and S cause β hemolysis Streptolysin S is active ONLY in aerobic conditions Streptolysin O is active only in anaerobic conditions 61 62  VIRULENCE FACTORS 1. Hyaluronic acid capsule - nonimmunogenic 2. M protein – hair-like projections on the cell wall major virulence factor promotes adherence antiphagocytic anticomplement type specific 3. F-protein – fibronectin binding protein 4. Lipoteichoic acid (LPA) –play a role in pathogenesis 63 Cell wall structure 64  Virulence Factors of β-Hemolytic S. pyogenes Produces surface antigens: C-carbohydrates – protect against lysozyme Fimbriae – responsible for adherence M-protein – contributes to resistance to phagocytosis Hyaluronic acid capsule – provokes no immune response C5a protease hinders complement and neutrophil response, degrades complement 65  Extracellular Virulence Factors Streptolysin O – a pore-forming toxin– damages membranes StrepSAgs i.e. Erythrogenic toxins: are produced by some strains, cause: rash of scarlet fever , pyrogenicity, acute rheumatic fever (ARF) lethal shock – Streptococcal Toxic Shock Syndrome (STSS) 66 Clinical significance of Streptococcus pyogenes: 1-Acute pharyngitis and tonsilitis. 2-Impetigo and deep skin infection. 3- Acute Rheumatic fever. Due to the bacteria M protein. Streptococcus tonsilitis 4-Acute nephritis. Due to antibodies interaction with glomerulus. Streptococcal tonsilitis 67  Poststreptococcal Sequelae Acute rheumatic fever (ARF) follows respiratory infection Rheumatic heart disease is produced by recurrent ARF Glomeronephritis follows respiratory or skin disease Only “nephritogenic” strains are involved. 68 Streptococcal erysipelas 69 Neisseria 70  Neisseria The Gram negative Diplococci: Neisseriae meningitidis Neisseriae gonorrhoeae Gram negative cocci Kidney-shaped, occur in pairs, in clinical specimens: present inside the polymorphonuclear cells. 71 Neisseriae gonorrhoeae  Clinical significance Neisseriae meningitidis 1-Meningitis and Meningococcemia. 2-Septicemia. Neisseriae gonorrhoeae 1-Urinary tract infection: (Most common): A-Gonococcal Urethritis. B-Pelvic inflammatory disease. 72 73  Neisseria infections N. meningitidis causes meningitis and meningococcemia. It is the leading cause of death from infection in children. N. meningitidis has a prominent polysaccharide capsule that enhances N. meningitidis virulence by its antiphagocytic action. 74  Neisseria gonorrhoea vs. N. meningitidis N. gonorrhoeae has no polysaccharide capsule, it has three outer membrane proteins (proteins I, II and III) protein II plays a role in attachment of the organism to cells and varies antigenically as well. The endotoxin of N. meningitidis is a lipopolysaccharide (LPS) but the endotoxin of N. gonorrhoeae is a lipo -oligosaccharide (LOS). 75 Characteristics Neisseria gonorrhoeae Neisseria meningitidis N. gonorrhoeae is the agent of N. meningitidis is a major cause of Agents gonorrhoea. cerebrospinal meningitis. N. gonorrhoeae form smooth, round, N. meningitides would form smooth, moist, uniform round, moist, uniform Colony Morphology grey/brown colonies with a greenish large grey/brown colonies with a glistening colour underneath on primary isolation surface and entire edges. medium. N. gonorrhoea is kidney shaped with N. meningitidis is semicircular diplococcus Morphology apposing ends concave. with flat apposing ends. N. gonorrhoeae form smooth, round, N. meningitides would form smooth, moist, uniform round, moist, uniform Colony Morphology grey/brown colonies with a greenish large grey/brown colonies with a glistening colour underneath on primary isolation surface and entire edges. medium. N. gonorrhoeae grow less N. meningitidis grow well on blood agar Growth on Blood Agar well on blood agar than N. meningitidis. than N. gonorrhoeae Capsule No Yes Pathogens It is always considered a pathogen. It is not always considered as pathogens. N. gonorrhoeae infections have a high N. meningitidis infections have a low Prevalence and Mortality prevalence and low mortality prevalence and high mortality. Cause meningitis and other forms of N. gonorrhoeae can also cause meningococcal disease such as Pathogenesis conjunctivitis, pharyngitis, proctitis or meningococcemia, a life-threatening urethritis, prostatitis, and orchitis. sepsis. 76  I. Neisseria meningitidis - Pathogenesis and Epidemiology Humans are the only hosts for meningoccocci. The organisms are transmitted by airborne droplets, they colonize the membranes of the nasopharynx and become part of the transient flora of the upper respiratory tract. A polysaccharide capsule that enables the organism to resist phagocytosis by polymorphonuclear leukocytes (PMNs). From the nasopharynx, the organism can enter the bloodstream and spread to specific sites such as the meningis or joints, or be disseminated throughout the body. 77 Meningococci have 3 virulence factors: Endotoxin (LPS) which causes fever and shock. An immunoglobulin A protease helps the bacteria attaches to the membrane of the upper respiratory tract. A polysaccharide capsule 78  Diagnostic Laboratory Tests Specimens: Specimens of blood are taken for culture and specimens of spinal fluid are taken for smear, culture and chemical determinations. Nasopharyngeal swab cultures are suitable for carrier surveys. Smears: Gram-stained smears of the sediment of centrifuged spinal fluid often show typical neisseriae within polymorphonuclear leukocytes or extracellularly 79  Laboratory tests Cerebrospinal fluid (C.S.F.) specimens are plated on chocolate agar and incubated at 37° C in an atmosphere of 5% CO2. Presumptive colonies are identified by Gram-stain and oxidase test. Serology: Antibodies to meningococcal poly-saccharides can be measured by latex agglutination or hemagglutination tests. Fermentation test: N. meningitidis ferment both glucose and maltose. 80 Growth of Neisseria meningitis Blood agar Chocolate agar 81 II. Neisseria gonorrheae - Pathogenesis and Epidemiology Gonococci like meningococci cause disease only in humans. The organism is usually transmitted sexually. Newborns can be infected during birth. Gonorrheae is usually symptomatic in men but often asymptomatic in women. 82  Neisseria gonorrheae Genital tract infections are the most common source of the organism. Pili constitute one of the most important virulence factors, because they mediate attachment to mucosal cell surfaces and are antiphagocytic. The endotoxin of gonococci is weaker than that of meningococci. Gonococci have no capsules. 83  Neisseria gonorrheae Gonococci cause both localized infections usually in the genital tract, and disseminated infections with seeding of various organs. Gonococci reach these organs via the bloodstream (gonococcal bacteremia). Gonorrhoeae in men is characterized by urethritis accompanied by dysuria and a purulent discharge. 84  Neisseria gonorrheae In women infection is located primarily in the endocervix, causing a purulent vaginal discharge and intermenstrual bleeding (cervicitis). The most frequent complication in women is ascending infection of the uterine tubes (salpingitis) which can result in sterility. 85  Infections caused by Neisseria gonorrheae Other infected sites include the anorectal area, throat and eyes. Anorectal infections occur in women and homosexual men. In the throat, pharyngitis Ophthalmia neonatorum occurs. In newborn infants, purulent conjunctivitis (ophthalmia neonatorum) is the result of gonococcal infection acquired from the mother during passage through the birth canal. 86 Gonococcal pharyngitis  Diagnostic Laboratory Tests Specimens: Pus and secretions are taken from the urethra, cervix, rectum, conjunctiva, or throat for culture and smear. Smears: Gram-stained smears of urethral or endocervical exudate reveal many diplococci within pus cells. 87  Neisseria gonorrheae Culture: immediately after collection, pus or mucus is streaked on enriched selective medium (e.g. modified Thayer-Martin medium) and incubated in an atmosphere containing 5% CO2 at 37° C. Fermentation test: N. gonorrhea ferment glucose only. 88  Neisseria gonorrheae They grow best on Thayer-Martin Medium; Chocolate agar supplemented by vancomycin and nystatin. Both factor X and V (hemoglobin, NAD) are required for Neissereiae species cultivation. A 5-10 % CO2 is required for primary cultivation. 89 Your tasks for lectures 4-5 Your manual Read: Chapter 13 p.205 Chapter 14 p.215 Chapter 20 p.295 90 91