staphylococci

SYSTEMIC MICROBIOLOGYSYSTEMIC MICROBIOLOGY

BACTERIOLOGYBACTERIOLOGY

Dr. Ashish V. Jawarkar M.D.

Dr. Ashish JawarkarDr. Ashish Jawarkar 22

GRAM POSITIVE BACTERIAGRAM POSITIVE BACTERIA

STAPHYLOCOCCUSSTAPHYLOCOCCUS


IntroductionIntroduction

Bacteria consist of only a single cell Bacteria consist of only a single cell Bacteria fall into a category of life Bacteria fall into a category of life

called the Prokaryotes called the Prokaryotes There are thousands of species of There are thousands of species of

bacteria, but all of them are basically bacteria, but all of them are basically one of three different shapes. one of three different shapes.


Classification of Bacteria Classification of Bacteria

Until recently classification has done on Until recently classification has done on the basis of such traits as: the basis of such traits as: shape shape

bacillibacilli: rod-shaped : rod-shaped coccicocci: spherical : spherical spirillaspirilla: curved walls: curved walls In clusters : actinomycesIn clusters : actinomyces


Classification of Bacteria Classification of Bacteria

The The Gram stainGram stain is named after the 19th is named after the 19th century Danish bacteriologist who developed century Danish bacteriologist who developed it. it. The bacterial cells are first stained with a purple The bacterial cells are first stained with a purple

dye called crystal violet. dye called crystal violet. Then the preparation is treated with alcohol or Then the preparation is treated with alcohol or

acetone. acetone. This washes the stain out of This washes the stain out of gram-negativegram-negative cells. cells. To see them now requires the use of a counterstain To see them now requires the use of a counterstain

of a different color (e.g., the pink of safranin). of a different color (e.g., the pink of safranin). Bacteria that are not decolorized by the Bacteria that are not decolorized by the

alcohol/acetone wash are alcohol/acetone wash are gram-positivegram-positive

Dr. Ashish Jawarkar 9

Gram Positive bacteria

• Staphylococci and streptococci constitute the main group of medically important gram positive bacteria

• There are also bacilli that are pathogenic such as Anthrax and the Clostridia group. These are also spore forming organisms

• There are also some other gram positive rods such as Listeria, Lactobacillus,and Cornybacterium diptheria


Staphylococci

• Staphylococcus was first identified in 1880 in Aberdeen, United Kingdom, by the surgeon Sir Alexander Ogston in pus from a surgical abscess in a knee joint.[1] This name was later appended to Staphylococcus aureus by Rosenbach

• Main types– Staph aureus – coagulase positive– Staph epidermidis, staph hemolyticus,

staph saphrophyticus – coagulase negative

http://en.wikipedia.org/wiki/Aberdeen

http://en.wikipedia.org/wiki/United_Kingdom

http://en.wikipedia.org/wiki/Alexander_Ogston

http://en.wikipedia.org/wiki/Alexander_Ogston

http://en.wikipedia.org/wiki/Pus


Description headings for each Description headings for each bacteriabacteria

MorphologyMorphology Growth characteristicsGrowth characteristics Biochemical reactionsBiochemical reactions ResistanceResistance Pathogenicity and virulencePathogenicity and virulence EpidemiologyEpidemiology Diseases causedDiseases caused Laboratory diagnosisLaboratory diagnosis TreatmentTreatment


StaphylococciMorphology

• Staphylococci stain dark purple with the gram stain.

• Staphylococci are arranged in grape like clusters

• Because they divide in three planes with daughter cells remaining in close proximity


Description headings for each bacteria

• Morphology• Growth characteristics• Biochemical reactions• Resistance• Pathogenicity and virulence• Epidemiology• Diseases caused• Laboratory diagnosis• Treatment


Growth characteristics

• Grow on ordinary media like nutrient agar

• Temperature 10-42 degree• Produce golden yellow pigment


Staphylococcibiochemical reactions

• The most virulent form of staphylococcus, SA also secretes coagulase, that causes citrated plasma to clot. These are referred to as coagulase positive

• There are other staph that do not have this ability and are labeled coagulase negative


Coagulase test

• Slide method or tube method• In tube method – we add culture

of staphylococci and rabbit plasma

• Look for clot formation


Resistance

• Resistant to drying – can remain in dried pus for 3-6 months

• resistant forms to penicillin have emerged– Produce penicillinase which

inactivates penicillin– Change surface receptors for

penicillin– Develop tolerance to penicillin –

bacteria inactivated, not killed


Pathogenicity

• Cell surface protein – protein A – antiphagocytic property

• Clumping factor – surface protein – responsible for slide coagulase test

• Produce enzyme coagulase• Produce toxins

– Hemolytic toxins (leucocidins)– Enterotoxin – causes food poisoning – vomitting,

diarrhoea etc– Toxic shock syndrome toxin – produces

hypotension and rash– Epidermolytic toxin – causes STAPHYLOCOCCAL

SCALDED SKIN SYNDROME (ssss)


Staphylococcus aureusepidemiology

• Carried by 20-40 % of healthy individuals in their mouth or on their skin

• It also found in their nasal mucosa• Vagina – increased risk of TSS during

menstruation• Umbilical stump infected during birth• Fomites carry staphylococci for months• Nosocomial infections by MRSA


Diseases caused by staphylococci


cellulitis


boils


Lab diagnosis

• Specimen to be collected– Skin – pus– Respiratory inf – sputum– Food poisoning – stool– For detection of carriers – nasal

swab


Staining and microsocopy

• Gram stained smears– Gram positive cocci in grape like

clusters


Culture

• Nutrient agar/blood agar– Colonies with golden yellow

pigment

• Coagulase test


Antibiotic susceptibility testing

• In case of suspected hospital acquired infection


Treatment

• Penicillin• In resistant cases – cloxacillin• For MRSA - vancomycin


Coagulase negative staphCoagulase negative staph

S. epidermidis – stitch abcess, grows S. epidermidis – stitch abcess, grows on implantson implants

S. saprophyticus – causes UTIS. saprophyticus – causes UTI


THANK YOUTHANK YOU

staphylococci

Health & Medicine