Staphylococci are gram positive cocci, Staphylococci are gram positive cocci, Occur in grape like...

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Staphylococci are gram positive cocci,Staphylococci are gram positive cocci, Occur in grape like clusters,Occur in grape like clusters, In Greek; In Greek; staphyle staphyle -- Bunch of grapesBunch of grapes

KokkusKokkus - Berry - Berry

CLASSIFICATION:CLASSIFICATION:

A) Based on coagulase production:A) Based on coagulase production:

1. Coagulase positive: Eg- S. aureus1. Coagulase positive: Eg- S. aureus

2. Coagulase negative: Eg- S. epidermidis2. Coagulase negative: Eg- S. epidermidis

S. saprophyticusS. saprophyticus

B) Based on pathogenicity:B) Based on pathogenicity:

1. 1. Common pathogen: Eg- S. aureusCommon pathogen: Eg- S. aureus

2. Opportunistic pathogens: Eg- S. epidermidis2. Opportunistic pathogens: Eg- S. epidermidis

S. saprophyticusS. saprophyticus

3. Non pathogen: Eg- S. homonis3. Non pathogen: Eg- S. homonis

STAPHYLOCOCCUSSTAPHYLOCOCCUS AUREUSAUREUS

MORPHOLOGY:MORPHOLOGY: These are spherical These are spherical

cocci.cocci. Approximately 1Approximately 1μμm in m in

diameter.diameter. Arranged Arranged

characteristically in characteristically in grape like clusters.grape like clusters.

They are non motile They are non motile and non sporing.and non sporing.

A few strains possess A few strains possess capsules.capsules.

CULTURECULTURE::

Media usedMedia used :- :-

i) Non selective media: Nutrient agar,i) Non selective media: Nutrient agar,

Blood agar, Blood agar,

MacConkey’s agar.MacConkey’s agar.

ii) Selective media: Salt-milk agar, ii) Selective media: Salt-milk agar,

Ludlam’s mediumLudlam’s medium

Cultural Characteristics:Cultural Characteristics:i) On nutrient agar-i) On nutrient agar- The colonies are large, circular, The colonies are large, circular,

convex, smooth, shiny, opaque and easilyconvex, smooth, shiny, opaque and easily

emulsifiable. Most strains produce emulsifiable. Most strains produce golden yellowgolden yellow

pigments.pigments.

ii) On MacConkey’s agar-ii) On MacConkey’s agar- The colonies are small The colonies are small & pink in colour.& pink in colour.

iii) On blood agar-iii) On blood agar- Most strains produce Most strains produce ββ- - haemolytic colonies.haemolytic colonies.

Biochemical reactions:Biochemical reactions:

1) Catalase test- Positive.1) Catalase test- Positive.

2) Coagulase test-2) Coagulase test-

i) Slide coagulase test- Positive.i) Slide coagulase test- Positive.

ii) Tube coagulase test- Positive.ii) Tube coagulase test- Positive.

SLIDE COAGULASE TEST TUBE COAGULASE TEST

PATHOGENICITYPATHOGENICITY::

Source of infection:Source of infection:

A) Exogenous: patients or carriersA) Exogenous: patients or carriers

B) Endogenous: From colonized siteB) Endogenous: From colonized site

Mode of transmission:Mode of transmission:

A) Contact: direct or indirect( through fomites)A) Contact: direct or indirect( through fomites)

B) Inhalation of air borne droplets B) Inhalation of air borne droplets

Disease:Disease:

Diseases produced by Staphylococcus aureusDiseases produced by Staphylococcus aureus

is studied under 2 groups:is studied under 2 groups:

A) InfectionsA) Infections

B) IntoxicationsB) Intoxications

A) A) INFECTIONS:INFECTIONS:

Mechanism of pathogenesisMechanism of pathogenesis::

Cocci gain access to damaged skin, mucosal orCocci gain access to damaged skin, mucosal or

tissue sitetissue site

Colonize by adhering to cells or extracellular matrix Colonize by adhering to cells or extracellular matrix

Evade the host defense mechanisms and multiply Evade the host defense mechanisms and multiply

Cause tissue damageCause tissue damage

Common Staphylococcal infections areCommon Staphylococcal infections are::

1) 1) Skin and soft tissueSkin and soft tissue: Folliculitis, furuncle (boil), : Folliculitis, furuncle (boil), carbuncle, styes, abscess, wound infections, carbuncle, styes, abscess, wound infections, impetigo, paronychia and less often cellulitis.impetigo, paronychia and less often cellulitis.

Folliculitis

Furuncle (boil)

Carbuncle

Styes Abscess

Impetigo Paronychia

CellulitisWound infection

2) 2) MusculoskeletalMusculoskeletal: Osteomyelitis, arthritis, bursitis, : Osteomyelitis, arthritis, bursitis, pyomyositis.pyomyositis.

osteomyelitisosteomyelitis

3) 3) RespiratoryRespiratory: Tonsillitis, pharyngitis, sinusitis, : Tonsillitis, pharyngitis, sinusitis, otitis, bronchopneumonia, lung abscess, otitis, bronchopneumonia, lung abscess, empyema, rarely pneumonia.empyema, rarely pneumonia.

4) 4) Central nervous systemCentral nervous system: Abscess, meningitis, intracranial : Abscess, meningitis, intracranial thrombophlebitis.thrombophlebitis.

55) Endovascular) Endovascular: Bacteremia, septicemia, pyemia, : Bacteremia, septicemia, pyemia, endocarditis.endocarditis.

EndocarditisEndocarditis

6) 6) UrinaryUrinary: Urinary tract infection: Urinary tract infection. .

B) B) INTOXICATIOINS:INTOXICATIOINS:

The disease is caused by the bacterial exotoxins,The disease is caused by the bacterial exotoxins,

which are produced either in the infected hostwhich are produced either in the infected host

or preformed in vitro.or preformed in vitro.

There are 3 types-There are 3 types-

1.1. Food poisoningFood poisoning

2.2. Toxic shock syndromeToxic shock syndrome

3.3. Staphylococcal scalded skin syndromeStaphylococcal scalded skin syndrome

1) 1) Food poisoning:Food poisoning:

Enterotoxin is responsible for manifestations of Enterotoxin is responsible for manifestations of staphylococcal food poisoning.staphylococcal food poisoning.

Eight types of enterotoxin are currently known, named Eight types of enterotoxin are currently known, named A, B, C1-3, D, E, and H.A, B, C1-3, D, E, and H.

It usually occurs when preformed toxin is ingested with It usually occurs when preformed toxin is ingested with contaminated food.contaminated food.

The toxin acts directly on the autonomic nervous The toxin acts directly on the autonomic nervous system to cause the illness, rather than gut mucosa.system to cause the illness, rather than gut mucosa.

The common food items responsible are - milk The common food items responsible are - milk and milk products, meat, fish and ice cream.and milk products, meat, fish and ice cream.

Source of infection- food handler who is a carrier.Source of infection- food handler who is a carrier.

Incubation period- 2 to 6 hours.Incubation period- 2 to 6 hours.

Clinical symptoms- nausea, vomiting and Clinical symptoms- nausea, vomiting and diarrhoea.diarrhoea.

The illness is usually self limited, with recovery in The illness is usually self limited, with recovery in a day or so.a day or so.

2) 2) Staphylococcal Toxic shock syndrome (STSS):Staphylococcal Toxic shock syndrome (STSS):

STSS is associated with infection of mucosal or STSS is associated with infection of mucosal or sequestered sites by TSST( formerly known as sequestered sites by TSST( formerly known as enterotoxin type F) producing S.aureus.enterotoxin type F) producing S.aureus.

It is fatal multisystem disease presenting with It is fatal multisystem disease presenting with fever, hypotension, myalgia, vomiting, diarrhoea, fever, hypotension, myalgia, vomiting, diarrhoea, mucosal hyperemia and erythematous rash which mucosal hyperemia and erythematous rash which desquamates subsequently.desquamates subsequently.

2 types of STSS known2 types of STSS known::

i) Menstrual associated STSS: Here colonization of i) Menstrual associated STSS: Here colonization of S.aureus occurs in the vagina of menstruating S.aureus occurs in the vagina of menstruating woman who uses highly absorbent vaginal woman who uses highly absorbent vaginal tampons. tampons.

ii) Non menstrual associated STSS: Here ii) Non menstrual associated STSS: Here colonization of S.aureus occurs in other sites like colonization of S.aureus occurs in other sites like surgical wound.surgical wound.

3) 3) Staphylococcal scalded skin syndrome Staphylococcal scalded skin syndrome (SSSS):(SSSS):

Exfoliative toxin produced by S.aureus is Exfoliative toxin produced by S.aureus is responsible for this.responsible for this.

It is a skin disease in which outer layer of It is a skin disease in which outer layer of epidermis gets separated from the underlying epidermis gets separated from the underlying tissues. tissues.

Types of SSSSTypes of SSSS::

Severe formSevere form Milder formMilder form

In new born - Ritter’s disease - Pemphigus In new born - Ritter’s disease - Pemphigus

neonatorumneonatorum

In older patients - Toxic epidermal - Bullous In older patients - Toxic epidermal - Bullous

necrolysis impetigonecrolysis impetigo

Toxic epidermal necrolysis

Ritter’s disease

Bullous impetigo

Pemphigus neonatorum

LAB DIAGNOSIS:LAB DIAGNOSIS:

Specimens collectedSpecimens collected:: Depends on the type of infection. Depends on the type of infection.

Suppurative lesion- Pus,Suppurative lesion- Pus,

Respiratory infection- Sputum,Respiratory infection- Sputum,

Bacteremia & septicemia- Blood,Bacteremia & septicemia- Blood,

Food poisoning- Feces, vomit & the remains of suspected Food poisoning- Feces, vomit & the remains of suspected food,food,

For the detection of carriers- Nasal swab.For the detection of carriers- Nasal swab.

I) I) Direct microscopyDirect microscopy: : Direct microscopy Direct microscopy

with Gram stained with Gram stained smear is useful in case smear is useful in case of pus, where cocci in of pus, where cocci in clusters are seen.clusters are seen.

This is of no value for This is of no value for

specimen like sputum specimen like sputum where mixed flora are where mixed flora are normally present.normally present.

Methods of examination:

c) Gram staining: c) Gram staining: Smears are examined Smears are examined from the culture plate from the culture plate and reveals Gram and reveals Gram positive cocci(1positive cocci(1μμm in m in diameter) arranged in diameter) arranged in grape like clusters.grape like clusters.

II) II) CultureCulture::

a) Media used:a) Media used:

b) Cultural Characteristics:b) Cultural Characteristics:

d) Biochemical reactions:d) Biochemical reactions:

III) Antibiotic sensitivity tests done as a guide to III) Antibiotic sensitivity tests done as a guide to treatment.treatment.

IV) Bacteriophage typing is done for IV) Bacteriophage typing is done for epidemiological purposes. epidemiological purposes.

V) Serological tests are not useful.V) Serological tests are not useful.

TREATMENT:TREATMENT: Drug resistance is common.Drug resistance is common. Benzyl penicillin is the most effective antibiotic, Benzyl penicillin is the most effective antibiotic,

if the strain is sensitive.if the strain is sensitive. Cloxacillin or Methicillin is used against Cloxacillin or Methicillin is used against

beta-lactamase producing strains.beta-lactamase producing strains. MMethicillin ethicillin RResistant esistant SStaphylococcus taphylococcus aaureus ureus

((MRSAMRSA) strains have become common.) strains have become common. Vancomycin is used in treatment of infections Vancomycin is used in treatment of infections

with MRSA strains.with MRSA strains.

EPIDEMIOLOGY:EPIDEMIOLOGY:

Staphylococci are primary parasites of human Staphylococci are primary parasites of human beings and animals.beings and animals.

Hospital infections caused by staphylococci Hospital infections caused by staphylococci deserve special attention because of their deserve special attention because of their frequency & they are caused by strains resistant to frequency & they are caused by strains resistant to various antibiotics.various antibiotics.

Staphylococci are the common cause of Staphylococci are the common cause of postoperative wound infection and other hospital postoperative wound infection and other hospital cross infections.cross infections.

PREVENTION:PREVENTION:

Isolation & treatment of MRSA patients.Isolation & treatment of MRSA patients.

Detection of carriers among hospital staff, their Detection of carriers among hospital staff, their isolation & treatment.isolation & treatment.

Avoid indiscriminate usage of antibiotics.Avoid indiscriminate usage of antibiotics.

CoCoagulase agulase NNegative egative SStaphylococci( taphylococci( CoNSCoNS ): ):

Two species of coagulase negativeTwo species of coagulase negative

Staphylococci can cause human infections-Staphylococci can cause human infections-

1. Staphylococcus epidermidis1. Staphylococcus epidermidis

2.2. Staphylococcus saprophyticus Staphylococcus saprophyticus

S. EpidermidisS. Epidermidis::

It is a common cause of stitch abscesses.It is a common cause of stitch abscesses.

It has predilection for growth on implanted foreign bodies It has predilection for growth on implanted foreign bodies such as artificial valves, shunts, intravascular catheters such as artificial valves, shunts, intravascular catheters and prosthetic appliances leading to bacteraemia.and prosthetic appliances leading to bacteraemia.

In persons with structural abnormalities of urinary tract, it In persons with structural abnormalities of urinary tract, it can cause cystitis.can cause cystitis.

Endocarditis may be caused, particularly in drug addicts.Endocarditis may be caused, particularly in drug addicts.

Streptococcal DiseasesStreptococcal Diseases

Streptococcus pyogenesStreptococcus pyogenes

Streptococcus pyogenesStreptococcus pyogenesPyogenes means pus producingPyogenes means pus producing

One of the most important pathogensOne of the most important pathogens

Gram positive cocci in chainsGram positive cocci in chains

Lancefield Serological Group ALancefield Serological Group A

Beta Hemolytic on blood agarBeta Hemolytic on blood agar

Gram Stain of S. pyogenes

Hemolysis on Blood Agar PlatesHemolysis on Blood Agar Plates

Alpha hemolysis-organism excretes hemolysins Alpha hemolysis-organism excretes hemolysins which partially break down rbc (incomplete which partially break down rbc (incomplete hemolysis) thus a greenish zone appears around hemolysis) thus a greenish zone appears around colony. colony. S. pneumoniaeS. pneumoniae

Beta hemolysis-organisms excretes potent hemoysins Beta hemolysis-organisms excretes potent hemoysins which completely lyse rbc (complete hemolysis) thus which completely lyse rbc (complete hemolysis) thus a clear zone appears around colony. a clear zone appears around colony. S. pyogenesS. pyogenes

S.pyogenes S. pneumonia

Beta hemolysisAlpha hemolysis

Diseases caused by Diseases caused by S. pyogenesS. pyogenes

Strep throat Strep throat ImpetigoImpetigo ErysipelasErysipelas CellulitisCellulitis Invasive Strep A infectionsInvasive Strep A infections

Necrotizing fasciitisNecrotizing fasciitis MyositisMyositis Toxic shock-like syndromeToxic shock-like syndrome

ErysipelasErysipelas

Acute infection and imflammation of the Acute infection and imflammation of the dermal layer of skin. dermal layer of skin.

Painful red patches which enlarge and thickenPainful red patches which enlarge and thicken Treatment -penicillin or erythromycinTreatment -penicillin or erythromycin

Erysipelas

Strep ThroatStrep Throat

Most common of all Strep diseasesMost common of all Strep diseases Spread by saliva or nasal secretionsSpread by saliva or nasal secretions Incubation period 2-4 daysIncubation period 2-4 days Sore throat, slight fever (101)Sore throat, slight fever (101) Important to treat immediately to avoid post Important to treat immediately to avoid post

strep diseasesstrep diseases

Diagnosis and treatment of Strep ThroatDiagnosis and treatment of Strep Throat

Tell tale symptoms are slight fever associated Tell tale symptoms are slight fever associated with sore throat and visual of pus in back of with sore throat and visual of pus in back of throatthroat

Quick diagnostic tests (Molecular) available Quick diagnostic tests (Molecular) available but must be confirmed by throat swab and but must be confirmed by throat swab and growth on blood agar (beta hemolysis) growth on blood agar (beta hemolysis)

Diagnosis and treatment of Strep ThroatDiagnosis and treatment of Strep Throat

If the strain of S. pyogenes is lysogenic for a If the strain of S. pyogenes is lysogenic for a particular phage which expresses an particular phage which expresses an erythrogenic toxin the result is Scarlet fevererythrogenic toxin the result is Scarlet fever

Rash appears and characteristic is the Rash appears and characteristic is the strawberry colored tonguestrawberry colored tongue

Strawberry Tongue

Treatment of StrepTreatment of Strep

Penicillin G or Erythromycin are drugs of Penicillin G or Erythromycin are drugs of choicechoice

Although the disease is self-limiting it is Although the disease is self-limiting it is important to treat immediately to avoid post important to treat immediately to avoid post strep complicationsstrep complications

Poststreptococcal diseasesPoststreptococcal diseases

Rheumatic Fever-autoimmune disease Rheumatic Fever-autoimmune disease involving heart valves,joints, nervous system. involving heart valves,joints, nervous system. Follows a strep throatFollows a strep throat

Acute glomerulonehritis or Bright’s Disease-Acute glomerulonehritis or Bright’s Disease-inflamatory disease of renal glomeruli and inflamatory disease of renal glomeruli and structures involved in blood filter of kidney. structures involved in blood filter of kidney. Due to deposition of Ag/Ab complexesDue to deposition of Ag/Ab complexes

Rheumatic FeverRheumatic Fever

Most common cause of permanent heart valve Most common cause of permanent heart valve damage in childrendamage in children

Exact cause not yet known but there appears to Exact cause not yet known but there appears to be some antibody cross reactivity between the be some antibody cross reactivity between the cell wall of S. pyogenes and heart musclecell wall of S. pyogenes and heart muscle

Rheumatic FeverRheumatic Fever

Diagnosis is based on symptoms and is Diagnosis is based on symptoms and is difficultdifficult

Occurs most frequently between ages of 6 and Occurs most frequently between ages of 6 and 1515

US it is about 0.05% of pop having strep US it is about 0.05% of pop having strep infectionsinfections

100x more frequent in tropical countries100x more frequent in tropical countries

Rheumatic FeverRheumatic Fever

Treatment is via salicylates (aspirin Treatment is via salicylates (aspirin derivatives) and corticosteroids to decrease derivatives) and corticosteroids to decrease inflammation and fever.inflammation and fever.

Glomerular NephritisGlomerular Nephritis

Diagnosis based on history of Strep throat and Diagnosis based on history of Strep throat and clinical findings.clinical findings.

Symptoms include fever, malaise,edema, Symptoms include fever, malaise,edema, hypertension and blood or protein in urinehypertension and blood or protein in urine

Occurs in 0.5% of those having strep throat.Occurs in 0.5% of those having strep throat.

Glomerular NephritisGlomerular NephritisTreatment and RecoveryTreatment and Recovery

Penicillin or erythromycin to eradicate and Penicillin or erythromycin to eradicate and residual strep infectionresidual strep infection

80-90% of cases recover with bed rest lasting 80-90% of cases recover with bed rest lasting for monthsfor months

Kidney damage in the remainder is often Kidney damage in the remainder is often permanent resulting in chronic glomerular permanent resulting in chronic glomerular nephritisnephritis

Streptococcus PneumoniaStreptococcus Pneumonia

Caused by infection with Caused by infection with Streptococcus Streptococcus pneumoniae (Pneumococci)pneumoniae (Pneumococci)

Gram positive, alpha hemolytic, not of Gram positive, alpha hemolytic, not of lancefield serotype Alancefield serotype A

Often part of normal flora of respiratory track Often part of normal flora of respiratory track and becomes infective once hosts resistance is and becomes infective once hosts resistance is lowered. Classified as an lowered. Classified as an endogenous endogenous infection.infection.

Strep PneumoniaStrep Pneumonia

Strep PneumoniaStrep Pneumonia

S. pneumoniaeAlpha hemolysis

Strep pneumoniaStrep pneumonia

Predisposing factors: upper respiratory viral Predisposing factors: upper respiratory viral infection, diabetes, alcoholisminfection, diabetes, alcoholism

60-80% of all pneumonias60-80% of all pneumonias

Strep Pneumonia

Cause of strep pneumoniaCause of strep pneumonia

Primary virulence factor is the capsular Primary virulence factor is the capsular polysaccharide which protects the organism polysaccharide which protects the organism against phagocytosisagainst phagocytosis

Pathogenesis is due to rapid growth of bacteria Pathogenesis is due to rapid growth of bacteria in alveolar spacesin alveolar spaces

Symptoms of Strep PneumoniaSymptoms of Strep Pneumonia

Onset abruptOnset abrupt

Chest painsChest pains

ChillsChills

Labored breathingLabored breathing

Diagnosis of Strep pneumoniaDiagnosis of Strep pneumonia

Chest XrayChest Xray

Culture and stainingCulture and staining

Biochemical tests of isolated organismBiochemical tests of isolated organism

Treatment of Strep PneumoniaTreatment of Strep Pneumonia

Typically treated with Penicillin G cefotaxime, Typically treated with Penicillin G cefotaxime, oflaxacin or for those allergic to penicillins oflaxacin or for those allergic to penicillins can be treated with erythromycin or can be treated with erythromycin or tetracyclinetetracycline

Pneumococcal vaccine (Pneumovax 23 or Pneumococcal vaccine (Pneumovax 23 or Pnu-immune 23) is available for the elderlyPnu-immune 23) is available for the elderly

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