Unit 12. Staphylococcus.pdf

Microbiology Unit 12 Staphylococcus genus Ve más allá 1 DEFINITIONS:  Taxonomy. The study of general principles of scientific classification and naming organisms.  Classification. Organisation of organisms into progressively more inclusive groups (taxons) by either phenotypic similarities or e...

Microbiology Unit 12 Staphylococcus genus Ve más allá 1 DEFINITIONS:  Taxonomy. The study of general principles of scientific classification and naming organisms.  Classification. Organisation of organisms into progressively more inclusive groups (taxons) by either phenotypic similarities or evolutionary relationships.  Nomenclature. Systematic naming of organisms based on international rules according to it’s characteristics.  Identification. Refers to the practical use of a classification scheme. CLASSIFICATION - TAXONOMY FAMILY GENUS SPECIE SUBSPECIE STRAIN NOMENCLATURE OF MICROORGANISMS Staphylococcus aureus Genus (upper case) Species (lower case) Either (genus and species) be written in ITALICS or UNDERLINED (if handwritten) FAMILY: Staphylococcaceae Genus: Staphylococcus GENUS SPECIE Staphylococcus aureus Staphylococcus epidermidis saprophyticus COAGULASE Positive Negative (CNS) Staphylococci can be divided into pathogenic and relatively nonpathogenic strains based on the synthesis of the enzyme coagulase. Staphylococcus aureus Staphylococcus aureus  Very virulent  Multiple pathogenicity factors  Resistant to dessication, temperature, salt, despite not forming spores.  Colonizers of our skin and mucous membranes (moist environments: nose, armpits) "BROKEN BARRIERS" ARE ESSENTIAL IN THEIR PATHOGENESIS Staphylococcus aureus MICROBIOLOGICAL CHARACTERISTICS AND IDENTIFICATION  Gram-positive cocci  Grouped in tetrads or clusters  Facultative anaerobes  Growth in standard media (nonselective) such as blood agar at 37 ° C  Golden colonies (aureus).  Beta-hemolysis on blood agar. Complete hemolysis. Staphylococcus aureus  Production of coagulase (coagulase +) ⇒ difference with other staphylococci  Production of catalase (catalase +) ⇒ difference with Streptococcus and other gram positive cocci Staphylococcus aureus Fuente: Dr. Richard Facklam.1980. Public Health Image Library (PHIL), CDC. Fuente: James Archer. 2013. Public Health Image Library (PHIL), CDC. Staphylococcus aureus B Hemolysis (complete) in blood agar Golden colonies Nathan Reading from Halesowen, UK. 2011. Streptococcus pyogenes (Lancefield Group A) on Columbia Horse Blood Agar - Detail.jpg Disponible en: commons.wikimedia.org/wiki/File:Streptococcus_pyogenes_(Lancefield_Group_A)_on_Columbia_Horse_Blood_Agar_-_Detail.jpg Staphylococcus aureus: Pathogenicity Pathogenicity  HOST: Normal microbiota (skin and mucosas) Pathogenicity favored by:  Broken mucocutaneous barriers  Impaired immunity (diabetes, chemotherapy, corticosteroids) Staphylococcus aureus: Pathogenicity STRUCTURAL VIRULENCE FACTORS: Teichoic acids, capsule (in some cases)  TOXINS production:  Cytotoxins α, β, γ, δ : β-hemolysis (in blood agar)  Panton-Valentine Leukocidin.  Thermostable Enterotoxins: Gastroenteritis (Food poisoning).  Exfoliatin: Scalded Skin Syndrome (destroy desmosomes in the stratum granulosum epidermis)  Toxic Shock Syndrome Toxin (TSST-1): Death by hypovolemic shock that leads to a multiorgan fail. Staphylococcus aureus: Pathogenicity  ENZYMES:  Coagulase:  Formation of intravascular thrombus  Formation of fibrin layer around staphylococcal abscess, protecting the microorganisms from phagocytosis  Hyaluronidase:  Invassion of tissues (hyaluronic acid from the conective tissue)  Catalase:  Breakdown of H2O2 from macrophages DNase:  Destruction of eukaryotic DNA  Lipase:  Destruction (hydrolysis) of lipids from the skin Staphylococcus aureus: Infections  COLONIZATION (microbiota, normal flora):  Skin, pharynx and nasal passages (nares)  Some healthy adults are persistent nasopharyngeal carriers of S. aureus  PURULENT INFECTIONS consisting of, containing, or discharging pus.  Folliculitis: pyogenic infection in the hair follicles.  Furuncle: extension of folliculitis. Painful. Dead and necrotic tissue.  Hydradenitis: chronic inflammation of the hair follicle (acumulation of water).  Paronychia: superficial infection of the hands (nails), or feet.  Impetigo: superficial. Face (mouth) and limbs. Young children.  Cellulitis: infection at the end of the legs (subcutaneous tissues). Painful.  Wound infection Staphylococcus aureus: Infections  SYSTEMIC INFECTIONS (Generalized)  Bacteremia: presence of bacteria in blood  Sepsis: systemic inflammation of the body (septicemia)  Endocarditis  Pneumonia  Arthritis/Osteomyelitis  Meningitis  MANIFESTATIONS CAUSED BY TOXINS:  Staphylococcal Food Poisoning (Gastroenteritis)  Staphylococcal Scalded Skin Syndrome (SSSS)  Toxic Shock Syndrome (T1SST). Coagulase negative Staphylococci Coagulase-Negative Staphylococci  Gram-positive cocci  Grouped in tetrads or clusters  Facultative anaerobes metabolism) (oxidative and fermentative  Growth in standard media (nonselective) such as blood agar at 37 ° C.  White or gray colonies. Non hemolytic on blood agar.  No coagulase enzyme (Coagulase -): difference with Staphylococcus aureus.  Production of catalase (catalase +): difference with Streptococci. Coagulase-Negative Staphylococci INFECTIONS  LESS VIRULENTS than S. aureus. TRANSMISSION BY:  Hands (normal microbiota) and fomites  Staphylococcus epidermidis:  Adhesion to plastics (infection of catheters, prostheses ...)  Infection of intravenous lines, urinary catheters, prosthetic heart valves (endocarditis, bacteremia).  Hospitalized patients and immunocompromised. PROSTHESIS INFECTION by Coagulase-Negative Staphylococus Involved in colonization and pathogenesis of CoNS: •Abundant mucus layer •Teichoic acids which act as adhesins Facilitates binding of CoNS to foreign body KEY FACTORS FOR INFECTION: PRESENCE OF FOREIGN BODIES OR IMMUNODEFICIENCY TREATMENT OF Staphylococus spp.  IF THERE IS PUS: DRAINAGE  REMOVE PLASTIC OR PROSTHESIS (S. epidermidis)  Urinary infection by S. saprophyticus: LIQUID.  To consider:  MAY BE MULTIDRUG RESISTANT!  THEY CAN BE CONTAMINANTS AS THEY LIVE IN OUR SKIN! Treatment TREATEMNT FOR Staphylococus aureus INFECTIONS  NO Penicillins, more than 95% of strains have beta-lactamases (penicillinases)  CLOXACILLIN (semisynthetic penicillin, type of penicilin modified to be resistant to beta lactamases), empirical treatment of choice in S. aureus, resistant to β-lactamase  Alternatives: quinolones, lincosamides etc. aminoglycosides, macrolides,  Some S. aureus have become resistant to methicillin (penicilin resistant to betalactamases) ⇒ MRSA (methicillin resistant S. aureus). This strains will be typically resistant to all β-lactams, except ceftaroline. Furthermore, MRSA have multiple mechanisms of resistance associated.  MRSA Treatment: GLYCOPEPTIDES (vancomycin, teicoplanin), linezolid. TREATMENT OF CoNS INFECTIONS  Similar to S. aureus but are often more resistant to cloxacillin and other families of AB  Empirically: Vancomycin or Teicoplanin (almost all gram-positive are sensitive to these antibiotics)  Later adjustment for sensitivity testing  Although CoNS are less virulent than S. aureus they are often more resistant Staphylococci in dentistry STAPHYLOCOCCI IN DENTISTRY  S. aureus and S. epidermidis are the most frequently isolated staphylococci in the oral cavity (in saliva of 1/3 of the population but in small quantities)  Not normal oral microbiota, only transient guests  Possible opportunistic pathogens if they find the chance.  Isolated from polymicrobial infectious processes were the significance as a pathogen is unknown  Found in dental plaque of immunocompromised or patients with prosthesis. STAPHYLOCOCCAL INFECTIONS IN THE ORAL CAVITY Staphylocci can be isolated in cultures from different samples of the oral cavity, but sometimes are just contaminants (skin): careful when sampling!  Root caries, periapical infections  Glossitis  Gingivitis and periodontitis  Maxillary osteitis, periimplant osteitis  Abscess of tonsils  Cavernous sinus thrombosis: formation of a blood clot from a spreading infection in the nose, sinuses, ears or teeth.  Facial malignant staphylococcal infection THANKS FOR YOUR KIND ATTENTION! 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