GRAM-POSITIVE BACTERIA
Clinical Importance, Diagnosis, Antimicrobial Susceptibility test, Control and Prevention
Universiti Malaysia KelantanFaculty of Veterinary Medicine
Course coordinator: Dr. Erkihun AkliluLecture II (24 September 2013)
STAPHYLOCOCCI
Occurs worldwide
Colonize nasal cavity, skin, mucous membrane, GIT (transient)
Infections are mainly endogenous
Indirect transmission is possible
Can survive in the environment for prolonged period
STAPHYLOCOCCI
Pathogenecity
Staphylococci are pyogenic (abscess formation and suppuration) Botryomycosis (Chronic staphylococcal wound) Granulomatous lesion with pockets of pus
Pathogenic strains produce various enzymes and toxins
Enterotoxins (A-E) cause food poisoning – emetic
STAPHYLOCOCCI
Exfoliatin causes staphylococcalscalded skin syndrome (SSS) ininfants and possiblby in dogs
STAPHYLOCOCCI
TSS-1: causes toxic shocksyndrome (TSS) in humans
Epidermolytic toxins: porcineexudative epidermatitis
The alpha toxin (haemolysin)produces gangrenous mastitis
STAPHYLOCOCCI
Leukocidin: kills neutrophils and macrophages
Protein A: binds to the FC region of IgG
Staphylokinase: activates plasminogen
Coagulase: causes plasma coagulation in vitro
Hyluronidase: Spreading factor
ANIMAL DISEASES CAUSED BY PATHOGENIC STAPHYLOCOCCI
ANIMAL DISEASES CAUSED BY PATHOGENIC STAPHYLOCOCCI
STAPHYLOCOCCAL HAEMOLYSINS
STAPHYLOCOCCUS
Laboratory Diagnosis
Specimen: includes, exudate, pus from abscess,mastitic milk, skin scrapings, urine,affected tissues
Direct Microscopy: Examination of Gram-stainedsmears (pus/exudate) may reveal Gram-positive cocci “Grape-like”
STAPHYLOCOCCUS
Isolation and Identification
Media: Ox or sheep blood agarSelective media: Sheep/ox blood agar with 15 mg
nalidixic acid and 10 mg colisitin sulphateper liter of media
For food microbiology: Mannitol salt agar (MSA) and Baird-Parker medium.
Incubated aerobically at 370C for 24 – 48 hours
STAPHYLOCOCCUS
Isolation and Identification
Colonial characteristics:
Colonies appear in 24 hours Round, smooth, glistening On BA appear larger and opaque compared to
smaller, colonies of haemolytic streptococci Golden-yellow pigment (human, domestic animals) Non-pigmented (white): dogs S.aureus and S.intermedius : produce double
haemolyis (alpha and beta) S. hyicus: non-haemolytic
STAPHYLOCOCCUS
Isolation and Identification
Haemolysis caused by S. aureus
Non-haemolytic colonies (S. hyicus)
STAPHYLOCOCCUS
Test for pathogenicity of staphylococcal isolates
Coagulase test DNAase test Test for protein A
STAPHYLOCOCCUS
Biochemical tests
STAPHYLOCOCCI
Differentiation of staphylococci, micrococci and streptococci
STREPTOCOCCUS
Habitat
Indigenous respiratory tract microbial flora ofanimals and humans
Certain species are also found in the gastrointestinaland urogenital tracts of humans and animals
STREPTOCOCCUS
General characteristics
Streptococci are facultative anaerobic Gram-positive organisms that often occur as chains or
pairs Catalase-negative
STREPTOCOCCUS
General characteristics
Hemolytic Reactions Beta Hemolysis
Complete hemolysis Clear zone around
colonies
STREPTOCOCCUS
Alpha hemolysis A greenish discoloration around the area
surrounding the colony due to incompletehemolysis of the red blood cells.
STREPTOCOCCUS
Gamma Reaction Absence of a hemolytic reaction No change around colonies on blood agar
STREPTOCOCCUS
Lancefield Groups Based on serological groupings Can also be detected by biochemical testing or antibiotic
Sensitivity
Group A Streptococcus pyogenes The most virulent human pathogen of the genus Is beta hemolytic Often identified by rapid serological tests or by
antibiotic resistance
STREPTOCOCCUS
Group B
Streptococcus agalactiae
Mildly to moderately virulent
Usually beta or alpha hemolytic (some strains are gamma)
Detected biochemically
STREPTOCOCCUS
Group D
Includes the fecal streptococci (enterococci)
Normal colon flora in humans and other animals
Genus Enterococcus
Several species; eg. Enterococcus faecalis
Occasionally pathogenic (often in urinary tract infections)
Usually gamma reactive
Detected biochemically
STREPTOCOCCUS
Pathogenesis
Pyogenic (associated with suppuration and abscess formation)
Enterotoxins: Haemolysins (Streptolysin O and S) Hyaluronidase Dnase NADase Protease Streptokinase Phage-coded pyrogenic toxin (Scarlet fever)
Polysaccaride capsules (S. pyogenes, S. pneumoniae, S. porcinus ---Antphagocytic
Polysaccaride capsules (S. pyogenes, S. pneumoniae,S. porcinus ---Antiphagocytic
Polysaccaride capsules in S. equi sbsp. equifunctions as adhesin.
STREPTOCOCCUS
STREPTOCOCCUS
Laboratory Diagnosis
Specimens: Exudates, pus, mastitic milk, skinscrapings, cerebrospinal fluid, urine, affectedtissues
Submit swabs in transport media
STREPTOCOCCUS
Laboratory Diagnosis
Direct microscopy:
Fixed smears from pus, exudates, sediments from centrifuged milk or urine
Gram stains
STREPTOCOCCUS
Laboratory Diagnosis
Isolation:
Routine media (BA), Edwardsmedia
Incubate at 37oC for 24 – 48 hours
Colonial morphology varies: small,translucent (hemolytic), mucoid (S.equi subsp equi & S.pneumoniae)colonies
STREPTOCOCCUSLaboratory Diagnosis
Isolation:
Peptone water sugar withadded serum (fastidiousstreptococci)
Enterococci and Group Dstreptococci grow at 45oC and40% bile (hyrdolyse aesculin)
STREPTOCOCCI
Streptococci identification tests
STREPTOCOCCUS
Laboratory Diagnosis
Identification:
CAMP test:
STREPTOCOCCI
Differentiation of equine group C streptococci
STREPTOCOCCI
Differentiation of enterococci and group D streptococci
STREPTOCOCCI
Differentiation of streptococci causing bovine mastitis
CORYNEBACTERIUM ANDRHODOCOCCUS
CORYNEBACTERIA Many corynebacteria are opportunistic pathogens
except for C. bovis (pyogenic infections)
Non-nitrate reducing biotypes of C. pseudotuberculosis cause caseous lymphadenitis in sheep, goat and rarely in cattle
Abscessation and enlargement of superficial or internal lymph nodes
CORYNEBACTERIA
Mechanical injury (e.g. shearing, insect bite) can be predisposing factors
Incubation period – about 3 months
C.pseudotuberculosis can survive in the environment longer
Bacteria can survive intracellularly and causes chronic infections
CORYNEBACTERIA
CORYNEBACTERIA
Laboratory diagnosis
Smear from lesion showingcoryneform bacteria
Isolation and identification of C.pseudotuberculosis from abscessmaterial (confirmatory)
RHODOCOCCUS
RHODOCOCCUS
R. equi (formerly known as Corynebacterium equi)
Gram-positive, soil saprophyte
Some spp of R. equi are cocci, while others appear as rods
Opportunistic pathogen of foals of less than six months old
Causes suppurative bronchopneumonia of foals
RHODOCOCCUS
Infection is usually through inhalation ofcontaminated dust particles
R. equi presents in large number in the feces of younghealthy foals and in the feces of older horses
RHODOCOCCUS
Laboratory diagnosis
Sample: tracheal aspirates or pus from lesions
Grows on non-enriched media
Produces characteristic mucoid salmon-like colonies