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Genus Staphylococcus >70 species & subspecies Wide host range Most species are commensal Only some cause important opportunistic infections Staphylococcus aureus Staphylococcus hyicus Staphylococcus pseudintermedius Occurs naturally worldwide in mammals and birds Colonizes in Nasal cavity Nas...

Genus Staphylococcus >70 species & subspecies Wide host range Most species are commensal Only some cause important opportunistic infections Staphylococcus aureus Staphylococcus hyicus Staphylococcus pseudintermedius Occurs naturally worldwide in mammals and birds Colonizes in Nasal cavity Naso-pharynx Skin Mucous membranes Gastrointestinal tract (TRANSIENTLY) Characteristics Gram +’ve cocci Grape-like clusters (most common) Single Pairs Short Chains Facultative anaerobes 1 anaerobic subspecies 1 microaerophilic species Catalase positive Coagulase tests are variable by species Test is used to differentiate between species of staphylococcus Coagulase variable species have strain dependent reactions Both coagulase positive and negative species are associated with normal flora +’ve (CoPS) Variable (+/-) -’ve (CoNS) Staph. Aureus Staph. Agnetis Staph. auricularis Staph. Argenteus Staph. Chromogenes Staph. Capitis Staph. Coagulans Staph. Hyicus Staph. Epidermidis Staph. Cornubiensis Staph. Haemolyticus Staph. Delphini Staph. Hominis Staph. Intermedius Staph. Saprophyticus Staph. Lutrae Staph. lugdunesis Staph. Pseudointermedius Staph. felis Staph. Schweitzer Staph. warneri Virulence Factors Staph. Aureus Opportunistic pathogen Broad range of virulence factors, none of which are individually essentially for virulence Virulence genes are NOT part of the core genome Accessory genes Cell Wall Associated Structures MSCRAMM Microbial Surface Components Recognizing Adhesive Matrix Molecules Role in cell surface attachment, colonization and invasion 24 different proteins that bind to host proteins in extracellular matrix Collagen Fibrinogen Fibronectin Laminin Proteins are important adhesins & coat host proteins for immune avoidance Peptidoglycan Capsule Most strains of Staph. Aureus do NOT produce large capsules that are characteristic of other bacterial pathogens Produce polysaccharide microcapsule Not visible with negative stains Capsular polysaccharides Linked to persistence in mammary glands Increased resistance to macrophages and phagocytosis Masks recognition of antibodies for the cell wall and therefore avoids complement activation Expression of capsule is variable among strains Biofilm Bacterial community that is metabolically heterogenous and embedded in self-produced matrix of polysaccharides Plays a role in bacterial resistance to antibiotic treatments 4 stages Adhesion Facilitated by surface proteins Proliferation Involves production of biofilm matrix that connects cells Maturation Involves production of biofilm matrix Detachment Dispersal of pathogen Protein A Staph. Aureus & pseudintermedius express as surface protein Binds to immunoglobulins to prevent recognition, opsonization and innate immune system avoidance Binds to Fc portion of antibodies so that effector end is not available to bind with Fc receptors on the host cells thus inhibiting opsonization Binding of antibodies coats the bacterial cell with host proteins which makes it easier to evade the immune system Role in biofilm formation Clumping factor (bound coagulase) Exotoxins Haemolysins Haemolytic toxins Affect leukocytes or other host cells Initially characterized by effects on RBCs but primarily act as cytotoxins and play a role in virulence Examples α(alpha) haemolysis→ creates pores in cell membrane→water influx→ cell lysis β(beta) haemolysis→sphingomyelinase damages RBC membranes γ(gamma) haemolysis→ pore-forming toxin δ(delta) haemolysis→ cytotoxic to neutrophils Leukocidins Pore-forming toxins that target white blood cells Important for killing phagocytes and avoidance of host innate immune system Damage host cells plasma membranes Examples LukMF’ → found in bovine Staph. Aureus isolates LukPQ → found in equine Staph. Aureus isolates LukSF-I → produced by Staph. Pseudintermedia Can target canine & human phagocytes Enterotoxins Heat stable Can survive boiling for 30 minutes) Responsible for food poisoning Caused by intoxication rather than infection. Vomiting provides no advantage to the bacterium for transmission or survival Pathogenic process Mast cells bind to enterotoxin → induced serotonin release → serotonin binds to 5-HT3 receptors expressed on enteric nerves → depolarization of vagus afferent nerves → stimulation of brainstem’s emetic loci→ vomiting Superantigens Proteins that bind to the outside of Major Histocompatibility Complex II (MHC-II) molecules on antigen presenting cells and T-cell receptors on T-cells. This activates the cell in polyclonal fashion resulting in a cytokine storm and disruption of immune function Fever, headache, vomiting, hypertension, rash, aches & multi-organ damage & coma Structurally related bacterial toxins that stimulate large numbers of T-cells that results in an uncontrolled proliferation and release of excessive amount of pro-inflammatory cytokines Exfoliatin Produced by Staph. Aureus & Staph. hyicus Breaks intercellular adhesion molecules (desmoglein-1) between keratinocytes in the epidermis Separation of tissue layers Blister formation Desquamation (peeling) or skin Enzymes Facilitate dissemination and enhance the pathogen’s toxicity Staphylokinase Fibrinolytic activity (clot degradation) Plasminogen activator Coagulase Converts fibrinogen into fibrin (creating clots) Fibrin clots form a coating on the bacteria cells making them resistant to opsonization & phagocytosis DNAse Degrades DNA Lipase Enzymatic activity on lipids Phospholipase Enzymatic activity on phospholipids Hyaluronidase Breaks down hyaluronic acids in host connective tissues and thus facilitating spread of pathogen to adjacent regions Protease Causes proteolysis Staph. Infections Comparatively stable in the environment allowing for indirect transmission Pyogenic bacteria Often causes suppurative lesions Coagulase +’ve (CoPS) are primary pathogenic staphylococcus species Coagulase -’ve (CoNS) are important in veterinary related diseases Predisposing Factors Injury to the skin Respiratory infections by other pathogens Immunosuppression (including medicinally induced) Malnutrition Disruption of normal flora Large exposure dose Intro of bacteria to a new body site Staphylococcal Mastitis Mammary gland inflammation Cause of significant economic loss in the dairy industry Reduced yield Increased veterinary treatment Culling Staph. Aureus primary pathogen for mastitis in dairy cattle Can be carried on teat skin, nasal cavity and rectum Majority of intramammary infections become chronic, low-grade or subclinical Transmission Primarily from udder to udder during milking via contaminated milking equipment or handlers Pathogenesis Bacteria colonize tip of teat → bacteria enter teat canal → Rapid replication → biofilm formation → degradation of epithelial cells in cistern, duct & alveoli → microlesions → influx of phagocytic cells and reduced milk production (may result in abscess or fibrosis) Subclinical No clinical signs or visual changes in milk Elevated somatic cell count (gland epithelial cells and leukocytes) Detected using California mastitis test Clinical Presents as swelling, firmness, warmth and tenderness of the udder Severe and peracute cases Onset of hyperthermia Reduced feed intake Tachycardia Depression Visual milk change Other Diseases caused by Staphylococcus aureus Cattle Skin infections Folliculitis Impetigo /w vesicles (sometimes bullae) Papules Pustules Crusts Small ruminants Mastitis Poultry Bumblefoot (pododermatitis) Osteomyelitis Septicemia Rabbits Mastitis Dermatitis Pododermatitis Skin abscesses Horses Botryomycosis Chronic suppurative granulomatous condition Occurs after castration due to infection of spermatic cord stump Staphylococcus hyicus Primary cause of ‘greasy pig disease’ (exudative epidermitis) Natural commensal of porcine skin, nose and ears Can also be isolated from vaginal mucosa which is transmitted to piglets at birth Staph. Hyicus causing greasy pig and the commensal staph. Hyicus are different Greasy pig staph hyicus can produce exfoliative toxins & biofilms Can occasionally be found in cattle, horses and poultry skin diseases Staph. hyicus Infections Exudative epidermitis Worldwide occurrence in pigs ≤ 3 months of age 20% morbidity rate, 80-90% mortality rates can be reached Initial presentation of lethargy, depression, anorexia & reddened skin Lesions evolve to yellowish-brown crusts in the groin, axillae, ears, face or damaged skin Dermatitis expands over time Skin becomes covered in sebum, serum and sweat producing the ‘greasy’ look and feel 24hrs-10 days after crusting can have fatal results caused by dehydration Predisposing stress factors Agalactia in sows Weaning Parasitic or viral infections Physical alterations Inappropriate housing materials Cystitis Arthritis Flank biting /w ear necrosis Staphylococcus pseudintermedius Normal part of canine microbiota Can be persistent in healthy dogs, intermittent or non-carriers Can be colonized with multiple strains of Staph. Pseudintermedius from the same or different anatomical sites Isolated from mouth, perineum, skin and nose Not defined as zoonotic but transmission between dogs and humans has occurred and cause human infection Staph. pseudintermedius Infections Canine pyoderma Certain breeds predisposed German shepherds Golden retrievers French bulldog Cavalier king charles spaniels Great Danes Can present as surface, superficial and deep pyoderma Superficial is most clinically relevant Initiated by underlying conditions (allergic skin reactions, ectoparasitic infections and endocrinopathies & skin lesions) Isolates from pyoderma cases and healthy dogs do NOT differ Genetic trait required for pathogenesis are shared between all strains Ability to form biofilm expresses specific adherence factors to canine keratinocytes and produces exfoliative toxins, leukocidins, enterotoxins and several evasion factors inhibiting function of complement, IgG, IgM & immune cells Otitis externa Mastitis Endometritis Cystitis Osteomyelitis Wound infections (dogs & cats) Antimicrobial Resistance Significant problem with Staph. Aureus & pseudintermedius Organisms acquire mecA gene encoding for penicillin-binding protein 2a. Renders methicillin-resistant Methicillin-resistant strains are frequently resistant to other antimicrobial agents Methicillin-resistant Staph. Aureus (MRSA) has been isolated from dogs, horses, pigs, poultry and dairy cows highlighting public health threat Control & Prevention Staphylococci can survive and remain virulent for comparatively long periods (weeks), especially in dry environments (scabs, dried pus etc) Focus should be on prevention rather than reaction Susceptible to disinfectants and antiseptics used commonly Killed rapidly at temperatures over 60ºC & between pH <4, >9.5 & in 9-10% NaCl Genus Streptococcus 103 recognized species, 9 subspecies within genus Worldwide distribution Most species are of interest in veterinary medicine Opportunistic pathogens and non-pathogenic commensals in humans and animals Commensals live primarily on mucosa of upper respiratory, alimentary and lower urogenital tracts Transmission Inhalation Ingestion Sexual activity Congenital Indirect via hands and fomites Characteristics Gram +’ve, cocci Small, less than 2 μm Growth by cell division across one plane Forms linear arrangements (chains of varied length) Arrangement is in smears of liquid media or clinical samples Clumps Arrangement is seen in smears made from colonies Strep. Pneumoniae predominantly in pairs Most are non-motile, catalase & oxidase negative, fastidious, facultative anaerobes Require addition of blood or serum to culture media for growth in vitro Susceptible to desiccation Classification of Streptococci Classifications are based on Haemolysis Type of haemolysis can vary among streptococcal species α(alpha) haemolysis Often referred to as ‘viridans streptococci’ viridis→ green in Latin Zone of green discolouration Hydrogen peroxide produced by bacteria oxidizes hemoglobin in the RBCs into methemoglobin Most commensal species found in animals will exhibit α Does not mean these are avirulent Strep. Pneumoniae & suis are α haemolytic pathogens β(beta) haemolysis Usually pathogenic Strep. Agalactiae & Strep. canis Erythrocytes lysed and produce a zone of haemolysis around colonies γ(gamma) haemolysis No haemolysis Most are non-pathogenic Cell wall carbohydrates (Lancefield Group) Most pathogenic streptococci possess serologically active carbohydrates Depending on cell wall carbohydrates, streptococci are sorted into groups A→H K→V Most common test for Lancefield grouping is Latex agglutination Commercial tests available for identifying groups A, B, C, D, F, & G Some pathogens are not groupable Strep. Uberis Strep. Parauberis Strep. pneumoniae Haemolysis by colonies on blood agar and Lancefield serological grouping is important factors in presumptive pathogen identification Virulence Factors Adhesins Different adhesins but similar to staphylococci. Streptococci also produces a number of surface proteins that bind to extracellular matrix proteins of the host cells. These adhesins are termed ‘Microbial surface components recognizing adhesive matrix molecules’ MSCRAMM/M Protein Important factor for Strep. Pyogenes & equi equi Fibrinogen binding & confers antiphagocytic properties to the streptococcal cell Enhances adherence to nasal epithelium May be associated with post infection complications in horses Purpura hemorrhagica Used to create vaccines for Strangles FbsA Analogous protein in Strep. Agalactiae Antibodies to FbsA are NOT protective Principal fibrinogen binding protein in Strep. Agalactiae FOG Analogous protein in Strep. Dysgalactiae equisimilis SzP Analogous protein in Strep. Equi zooepidemicus Similar to M protein Capsule Some species form capsules Protection from phagocytosis Can be made of hyaluronic acid (Group A & C streptococci) Part of mammalian tissue and is poorly antigenic Does not readily bind to complement components and therefore is antiphagocytic Polysaccharides (Group B, E, & G) Contain sialic acid (Strep. Suis & agalactiae) Streptococcal pyrogenic toxin superantigens (SPEs) (exotoxins) Pyrogenic Fever inducing Superantigens simultaneously bind to MHC-II molecules and T-cell receptors. This binding results in activation of large proportion of antigen presenting cells and T-cells, and a subsequent release of high systemic levels of cytokines leading to immune malfunction & different systemic clinical signs Productions of exotoxins has been identified with three species Strep. Pyogenes Strep. Equi equi Strep. Zooepidemicus Streptolysins (haemolysins) Streptolysin O (oxygen-labile) Exotoxin Forms protein complex on target membrane creating relatively large pores Streptolysin S (stable) Exotoxin Responsible for large zones of beta haemolysis on sheep blood agar Broad cytolytic spectrum Effects RBCs, WBCs, platelets, tissue-culture cells & subcellular organelles Lysosomes & mitochondria Cytolysins cause lysis of neutrophils, macrophages & platelets Streptokinase Enzyme that activates conversion of plasminogen to plasmin Protease that degrades fibrin clots Invasion factor Biofilm regulatory protein A Produced by Strep. Agalactiae Promotes establishment of infection Improves antibiotic resistance & immune system avoidance Characteristics of Streptococcal Infections Most disease causing strep are commensal and only cause disease when stress or internal conditions allow Pyogenic infections Skin Respiratory tract Repro tract Umbilical stump Mammary glands Febrile symptoms can develop in some stages Locally affected areas exhibit pus formation If drainage is prevented, abscess formation Hematogenous spread of primary infection may result in septicemia Pathogenic Species of Streptococci Diseases of the udder Strep. Agalactiae Strep. Dysgalactiae Strep. Uberis Pathogens of head and neck lymphatics Strep. Equi equi Strep. Canis Equine lower respiratory diseases Strep. Pneumoniae Infections of CNS, lungs and joints Strep. Suis Opportunistic pathogen causing variety of diseases in different species Strep. Equi zooepidemicus Streptococcus agalactiae (Lancefield group B) Lancefield group B Invasive disease in camels and occasionally disease causing in dogs, fish, cats & hamsters Persistence by feeding contaminated milk to calves can result in colonization with the gastrointestinal or tonsillar regions allowing for maintenance of the disease in the herd. Important because of the chronic, subclinical and contagious bovine mastitis caused Transmission through inappropriate milking processes Can survive for weeks in milk fat, on skin (bovine and human), and on clothing for 4-21 days and in fresh water for more than 4 weeks ~96% of cases are subclinical Normally found in cattle & human GI tracts Approx. 30% of humans are health carriers Colonization can be transitional, persistent or intermediate in human GI tracts, urogenital tract or throat Newborns are at risk of meningitis and neonatal septicemia. There is no ONE classical presentation of this pathogen in dairy herds Infection can become evident anywhere from the first month to 1 year after introduction of an infected cow to the herd Predisposing Factors Poor milking time hygiene Not using dry cow antibiotic therapy Not culling chronically infected cattle Teat hyperkeratosis Caused by intense suctioning of milking equipment and improper equipment attachment causing tissue damage to the teat Transmission Primarily udder to udder during milking Fecal shedding and milk leakage from infected udders may contribute to environmental contamination and can promote environmental transmission Pathogenesis Enters through teat→ adhesion, colonization and multiplication on epithelium of teat and duct sinuses→ slow progression of inflammation and fibrosis causing damage to cells→ damaged cells and bacteria release signal for polymorphic nuclear leukocytes (PMN) → phagocytosis of bacteria & death resulting in a release of lysosomal enzymes that further damage host tissue→ fibrin plug formation→ involution of secretory tissue and loss of milk production Streptococcus Dysgalactiae Commensals in most mammals and birds but is an opportunistic pathogen. It is found in the epithelial and mucosal tissues in domestic animals and farmed fish. Subspecies (based on geno & pheno-typic classifications) Dysgalactiae Lancefield group C Alpha haemolytic Causes acute, subclinical mastitis in cattle Associated with insect bites or other teat/udder epithelial injury (direct access to target tissues) Trueperella pyogenes is a synergistic pathogen in sporadic, acute clinical infections Equisimilis Lancefield groups A, C, G, or L Beta haemolytic Disease causing in variety of species + humans Streptococcus uberis (No Lancefield group) Commensal in cattle Tonsils, intestines, mucous membranes & skin 20-30% of clinical mastitis cases Many of which are opportunistic invasions of the mammary gland Environmental mastitis pathogen Older cattle more likely to be infected Associated with heavy environmental soiling with fecal matter Mastitis severity varies by strain virulence, number of infecting organisms, season, animal immune status, parity & stage of lactation Infection may occur more commonly after drying off or cows with open teat canals Streptococcus equi equi (Lancefield group C) Lancefield Group C Obligate parasite/primary pathogen Causes Strangles Highly contagious nasopharyngeal infection also impacting the associate lymph nodes Transmission Infection source Nasal discharge, pus from an abscess, contaminated water, feed or fomite Animals can be carriers for short or longer periods Pathogenesis Strep. Equi enters via mouth or nose & attaches to cells in the crypts of oral tonsils and cilia of nasopharyngeal tonsils→ ~48 hrs clumps of Strep. Equi visible in lamina propria→ large number of polymorphic nuclear (PMNs) leukocytes activated and attracted to site of infection, failure to phagocytose and kill pathogen→ abscess formation with clumps of long chains of extracellular streptococci interspersed among large number of degrading PMNs→Potential to metastasize and form abscesses in other organs (brain, thoracoabdominal lymph nodes) Clinical Signs Incubation 3-14 days Fever Lassitude/no energy Nasal discharge Cough Difficulty swallowing Swelling of mandibular lymph nodes Potential metastasis Prognosis & Disease Continuation Nasal shedding begins at 4-14 days and ceases between 3-6 weeks post acute infection phase Most cases are uneventful and quick Infection may persist in guttural pouch after clinical recovery Prolonged carriage is commonly associated with empyema (pus formation in sinuses) Choroids of guttural pouch & cranial sinuses Hardened collections of pus Streptococcus equi zooepidemicus (Lancefield group C) Name stems from wide host range Mucosal commensal with wide range of opportunistic diseases where hosts are experiencing stress (viral infections, heat stress, tissue damage etc) Most frequently isolated pathogen from opportunistic infections in horses When concurrent with influenza infections, high summer temps, transport stress it can be a devastating and fatal respiratory tract pathogen in horses Can cause peracute and fatal haemorrhagic pneumonia in animals shelters, kennels and laboratory colonies Specific clones have caused widespread swine loss in China, US & Canada Streptococcus canis (Lancefield group G) Lancefield group G Sporadic, opportunistic purulent infections in multiple sites Urogenital tract, otitis externa, pneumonia, endocarditis, neonatal septicemia), abscesses, necrotizing fasciitis, toxic shock syndrome. Infects Dogs Cats Mink Possums Aquatic mammals Humans Found in Anal mucosa Oropharynx Urogenital tract Parts of canine and feline skin Strep. Canis in Cats Commonly isolated from skin and lymph node abscesses in cats Causes mastitis, conjunctivitis, metritis Septicemia in kittens Kittens infected by vaginal secretions or from mouth of queen during severing of umbilical cord Local abscess forms→ bacterial thrombi in variety of body sites Death within a week Older queens may be able to pass some immunity to kittens making them more resistant Juvenile streptococcosis When maternal antibodies wane (around 2-4 months) and during post weaning Invasion of tonsils and local lymphatics of head and neck Purulent lymphadenitis Persian cats are more susceptible Streptococcus suis (Lancefield groups D, R, S & T) Wide range of clinical syndromes Serious zoonotic pathogen in humans Pigs Primary carriers Palatine tonsil carrying site Transmission by respiratory and oral routes Causes in pigs Septicemia Meningitis Endocarditis Bronchopneumonia Polyarthritis Occurrence associated with intensive management systems and co-infections Control & Prevention Survives in dry pus for weeks Killed at 55-60ºC in 30 minutes Inhibited by 6.5% NaCl 40% Bile low (10ºC) and high (>44ºC) temperatures Resistant to antibiotics Tetracycline Benzopenicillin Clindamycin Tilmicosin Norfloxacin Erythromyacin Genus Enterococcus Possess phenotypic traits that set them apart. Used to be classified as group D streptococci before the genus Enterococcus was established. 60 species Most in intestinal tracts of mammals and birds Mainly opportunistic Infect compromised sites Virulence Factors Multiple MSCRAMMs (adhesins) Aggregation substance (adhesin) Surface protein that promotes aggregate formation and adherence to epithelial surfaces Promotes adherence to other enterococci Pili Promotes adhesion to multiple types of cells & biofilm formation Capsule Antiphagocytic Cytolysin Heat-labile, oxygen stable, pore-forming exotoxin lysing both bacterial and eukaryotic cells Gelatinase Important in biofilm production Lyses several peptides Gelatin Collagen Hemoglobin Fibrin Promotes dissemination Transmission & Pathogenesis Endogenous enterococci contaminate and infect compromised sites Cell wall peptidoglycan and lipoteichoic acids initiate inflammatory response Capsule, cytolysin and other virulence factors promote further inflammatory response Disease causing Enterococcus Species Intestinal Diseases (diarrhea in young animals) Other Infections Enterococcus durans Enterococcus faecalis (~95%) Enterococcus hirae Entercoccus faecium (~5%) Enterococcus villorum Otitis externa (dogs & cats) Lower UTIs & Bacterial endocarditis (dogs) Dogs, cats, horses, cattle, swine etc Enterococcus spp. Should be expected in any condition that could result from contamination of compromised site with fecal matter Abscesses, wound infections etc Resistance Grows in 6.5% NaCl, 40% bile, high and low temperatures Intrinsically resistant to beta lactam antibiotics, aminoglycosides, clindamycin, fluoroquinolones and trimethoprim-sulfonamides Vancomycin-resistant strains of enterococci are serious health problem in human medicine