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