Streptococci PDF

1 DR. OKUNLADE A.O DEPT OF VETERINARY MICROBIOLOGY AND PARASITOLOGY UNIVERSITY OF IBADAN. 8/21/2024 2 Streptococci 8/21/2024   They are non motile, nonsporing, Gram positive cocci 3 in pairs or chains  Warm-blooded...

1 DR. OKUNLADE A.O DEPT OF VETERINARY MICROBIOLOGY AND PARASITOLOGY UNIVERSITY OF IBADAN. 8/21/2024 2 Streptococci 8/21/2024   They are non motile, nonsporing, Gram positive cocci 3 in pairs or chains  Warm-blooded animals carry a resident streptococci flora on the mucous membrane of upper respiratory tract,  lower genital and most of the alimentary tract (enterococci)  They are haemolytic α- Strept pneumoniae (pneumococcus) is a common colonizer of the human nasopharynx 8/21/2024  Schematic diagram of group A Streptococcal cell Pilus(Lipotechoic 4 acid) Hyaluronic acid capsule Protein antigen MT&R cytoplasm Mucopeptide Cytoplasmic membrane 8/21/2024   On primary isolation group A and C strains of 5 streptococci have a hyaluronic acid capsule which interferes with phagocytosis  they are non-antigenic in Strept equi subsp. equi and Strept. pyogenes  The Strept. pneumonia and Strept. agalactiae have antigenically diverse capsules used for serotyping  Two major characteristics employed for the identification of Streptococci are the Lancefield (serological) groups and the type of haemolysis produced 8/21/2024   There are Lancefield groups (A–W, excluding I) 6 characterized by a series of carbohydrate antigens in the cell wall referred to as C substance  The streptococci within S. pyogenes (group A) can be divided into serological types by means of two classes of protein antigens: M and T  M is a type-specific antigen near the surface of the organism that can be removed by trypsinization 8/21/2024   T is not type specific, may be present with or 7 independent of the M antigen  and is demonstrated by agglutination tests with appropriate antisera  Other serological procedures including latex agglutination, coagglutination,  and the fluorescent antibody tests are also used to identify the Lancifeld groups 8/21/2024  Extracellular products (Cellular 8 products of medical importance)  Haemolysin: α, β, and γ  The alpha streptococci do not destroy red cells but produce a zone of greenish discoloration around the colonies  e.g The viridans group of streptococci (VGS) include a variety of commensal bacteria  The term viridans comes from the Latin word ‘viridis’, meaning green 8/21/2024   Beta- haemolytic streptococci destroy red cells and 9 produce zones of transparent clarity around colonies.  Most pathogenic types are in this group  Gamma haemolytic streptococci are non haemolytic  They are mostly non pathogenic  Streptolysins: The β-haemolytic group A streptococci produce 2 streptolysins (O and S)  Streptolysins O is antigenic and antibody to it is a good indicator of present and past infection 8/21/2024   Streptolysins O is oxygen sensitive, but Streptolysins 10 S is not; both are toxic to phagocytes  Streptokinase (Fibrinolysin): activates plasminogens to plasmin (protease) thus leading to the digestion of fibrin clots.  This process prevents the buildup of fibrin clots that may contain and protect organisms  It produces neutralizing antibodies in many streptococcal infections 8/21/2024   Hyaluronidase: it is associated with streptococcal 11 cellulitis  It facilitates the spread of infection in the tissues.  The enzyme is antigenic and convalescent serum is rich in neutralising antibodies  Deoxyribonucleases A, B, C and D (Streptodornase) it is known to assist in the production of substrates for growth  Streptococcal pus may be thin/watery because of this enzyme. DNases B and D are ribonucleases 8/21/2024   Proteinase: is produced by group A streptococci 12 and has a broad substrate specificity  Erythrogenic toxins (A,B and C): are low molecular weight proteins.  Streptococal erythrogenic toxins are responsible for the rash in scarlet fever  Adhesins Streptococcal bacteria possess adhesins that aid the adherence of the organism. 8/21/2024   Adhesins Target 13 i) Pneumococcal adhesion A Fibronectin ii) Collagen -binding protein A Fc portion IgA iii) Enolase Plasminogen 8/21/2024  MODE OF INFECTION AND 14 TRANSMISSION PYOGENIC INFECTIONS  Some species of staphylococci and streptococci e.g Strept. equi subsp. equi are termed pyogenic because the produce infection characterised by pus formation  When pyogenic bacteria establish in a tissue like mucous membrane of pharynx they produce vasodilation, exudation of plasma 8/21/2024   S. pyogenes (Group A) causes septic sore throat, 15 scarlet fever diffuse rash and fever in children, pyoderma erysipelas (human)  streptococcal toxic-shock-like disease due to same toxin (Spc) similar in mechanism to TSS-I  S. agalactiae (Group B) causes human meningitis and chronic bovine mastitis with loss of lactating ability (agalactia).  The predisposing factor of chronic bovine mastitis is milking machine 8/21/2024   S. dysgalactiae subsp. dysagalactiae (Group C) 16 incriminated in sporadic acute mastitis.  It is commonly found in mouth, udder and it is opportunistic organism often in conjunction with Actinomyces pyogenes.  S. dysgalactiae subsp. equisimilis it is associated with joint-ill in piglets usually acquired from sow.  It has also been associated with lymph node abscess in horses and placentas of aborted foal.  Contaminated wounds or umbilicus may lead to suppurative arthritis. 8/21/2024   S. equi subsp. equi: (Group C) responsible for highly 17 contagious upper respiratory tract and associated lymph nodes infection of solipeds  Immune complexes may be responsible for purpura haemorrhagia in horses after S. equi subsp equi infection.  S. equi subsp. zooepidemicus (Group C) closely related S. equi subsp equi it is an opportunistic pathogen: 8/21/2024  Clinical conditions associated with 18 Streptococci in domestic animals  Cattle/goats: severe mastitis: An investigation of bovine mastitis in Nigeria showed Streptococcus uberis was the most  frequently encountered species with an incidence of (55.4%) followed by Streptococcus agalactiae (24.6%),  Streptococcus dysgalactiae (12.3%) Streptococcus zoopidemicus (3.9%) Streptococcus bovis (2.3%) and Streptococcus  equinus (1.5%). 8/21/2024   Horses: lymph node abscesses, pneumonia, 19 endometritis, cervicitis, abortion and wound infection.  Foals: bacteriaemia, abscesses, polyarthritis (joint ill); nasal catarrh and pneumonia  Mares: commonly associated with reproductive tract conditions.  Sheep/dogs: wound infection, septicaemia, pleuritis, pneumonia, pericarditis.  Chickens: septicaemia  Guinea pigs: purulent cervical lymphadenitis 8/21/2024   Streptococcus iniae: Streptococcus of fish which is 20 implicated in bacteraemia, cellulitis, endocarditis and meningitis in fish handlers. Its strains are untypable  Viridans Streptococci: This is a group of nontypable streptococci which are commensals of oropahrynx and female gentalia of animals and man 8/21/2024  Laboratory Diagnosis 21  Samples can be taken and vary according to the disease condition  e.g pus in case of abscess or strangles; milk in mastitis, joint fluid in arthritis  CSF or meningeal swab in meningitis, organ and or blood in septicemia; urine in urinary tract infection  Gram stain of the smear from the clinical sample will yield Gram-positive cocci, singly or in chains 8/21/2024   Arginine broth (enrichment) is useful in identifying 22 some streptococci  The pathogenic strains grow best in serum or blood enriched media (cow or sheep blood)  Incubate preferably at 37oC  Colonies vary from large to small in size and are round, mucoid (hyaluronic acid),  matt (high M protein, virulent) and glossy (little M protein, low virulence) with dewdrop appearance with or without haemolysis 8/21/2024   Serological procedures including latex 23 agglutination, coagglutination,  and the fluorescent antibody tests are also used to identify the Lancifeld group antigens  CAMP Test: The phenomenon (named after Christie, Atkins and Munch-Petersen)  reflects haemolytic synergism between staphylococcal β-toxin and Streptococcus agalactiae toxin (CAMP protein, cytolysin)  Their combined action on sheep or bovine blood agar produces larger and clearer zones of haemolysis than either agent alone 8/21/2024   CAMP test may be conducted for presumptive 24 identification of S. agalactiae.  It involves completion of partial haemolysis (β- haemolytic) of Staph aureus  when S. agalactiae is streaked perpendicularly to that of Staph. aureus on blood agar  S. porcinus and S. iniae are CAMP-positive whereas Group A streptococci CAMP-negative  CAMP test may be conducted using Staph. aureus-β- toxin containing medium  and incorporation of esculin into the medium helps to distinguish 8/21/2024  CAMP Test Esculin test Heamolysis 25 S. agalactiae + - α, β or γ S. - - α dysagalactiae S. uberis - + non- haemolytic 8/21/2024  Carbohydrate fermentation 26  Haemolytic colonies can be subcultured in Todd- Hewitt broths  used to inoculate serum sugar broths  S. equi subsp equi can be identified by its inability to ferment ribose, sorbitol, trehalose  and lactose and by its possession of the Lancefield group C antigen  Optochin test: Pneumococci are sensitive but streptococci are resistant to optochin 8/21/2024   Hippurate test 27  Group B streptococci hydrolyse sodium hippurate  Inoculate hippurate broth, incubate overnight and add excess 5% ferric chloride  A brown precipitate indicates hydrolysis.  Controls:  positive: Streptococcus agalactiae;  negative: S. salivarius. 8/21/2024