staphylococcus aureus basic exercise

Staphylococcus aureus Basic Identification in Applied Microbiology Exercise : 

Staphylococcus aureus Basic Identification in Applied Microbiology Exercise Dr.T.V.Rao MD Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 1

Patient presented with: 

Patient presented with A 30 years male patient presented with an abscess left mandibular region since 3 days, with onset of fever. Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 2

What are bacteriological agents can produce this pyogenic condition ?: 

What are bacteriological agents can produce this pyogenic condition ? Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 3

Most important bacteria are: 

Most important bacteria are Most abscesses are due to infection by Staphylococcus (as in the boil abscess), but other bacteria are sometimes associated Streptococci, Hemophilus spp. E.Coli Klebsiella spp Pseudomonas spp and many others. Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 4

How you proceed to identify the etiological agent : 

How you proceed to identify the etiological agent Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 5

How to make a Definitive Diagnosis: 

How to make a Definitive Diagnosis To make a definitive diagnosis and to confirm that Staphylococcus is the bacteria causing the infection, Microscopic observation of the given specimen and a culture can be done. Once a bacteria is identified on a culture, the pattern on sensitivities to antibiotics can help to tell whether or not it is actually MRSA, routine staph aureus, or another bacteria. Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 6

Gram staining showing Gram positive Cocci in clusters – Probably Staphylococcus spp: 

Gram staining showing Gram positive Cocci in clusters – Probably Staphylococcus spp Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 7

Slide 8: 

What are Staphylococci : Gram positive cocci ( from Greek staphyle, means bunch of grapes ) that occur singly and in pairs, short chains and irregular grape-like clusters. Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 8

Structure and Physiology of Staphylococcus : 

Gram-positive cocci, nonmotile, facultative anaerobes Cells occur in grapelike clusters because cells division occurs along different planes and the daughter cells remain attached to one another Salt-tolerant: allows them to tolerate the salt present on human skin Tolerant of desiccation: allows survival on environmental surfaces (fomites) Structure and Physiology of Staphylococcus Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 9

Staphylocoous appear as: 

Staphylocoous appear as Gram stained smear showing Gram positive cocci with cluster formation indicates presence of Staphylococci Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 10

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III. Virulence factors of Staphylococcus aureus Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 11

Staphylococcus aureus grown on Nutrient agar: 

Staphylococcus aureus grown on Nutrient agar Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 12

General Cultural Characteristics: 

General Cultural Characteristics Some Staphylococcus species, most notably S. aureus , produce a hemolysin that completely lyses red blood cells of humans and some other mammals (sheep blood). This is referred to as “beta” hemolysis. 13

What are your observation on Blood Agar: 

What are your observation on Blood Agar Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 14

What are the commonly performed in vitro pathogenicity tests?: 

What are the commonly performed in vitro pathogenicity tests? Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 15

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Staphylococcus aureus : is the staphylococcus which has the ability to clot plasma, which is coagulase positive. More than 80% of Staphylococcus aureus strains produce beta-lactamases.

Other S. aureus Characteristics: 

17 Other S. aureus Characteristics Mannitol fermentation is another useful characteristic – it is unique to, and consistent among S. aureus strains. Virtually all strains of S. aureus ferment mannitol. Bright yellow colonies on a yellow background indicates mannitol fermentation on mannitol salt agar.

Coagulase test for Identification of Staphylococcus : 

18 Coagulase test for Identification of Staphylococcus Staphylococcus aureus coagulation of plasma* “Free” staphylocoagulase Fibrinogen + CRF Fibrin Normal coagulation of plasma Thrombin Fibrinogen Fibrin (soluble ) (insoluble) *EDTA Rabbit plasma is preferred for the “free” or tube coagulase test because it contains a large amount of CRF

Slide Coagulase Test: 

Slide Coagulase Test The most important distinction among staphylococci is whether or not they produce the enzyme coagulase . S. aureus the most common pathogen among the catalase positive gram positive cocci and is differentiated from other staphylococci by the coagulase test . Here the bacterial cells have been suspended in a drop of rabbit plasma. Coagulase bound to the cell wall acts on fibrinogen and causes the clumping of the bacteria (right). Coagulase is an important virulence factor of S. aureus Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 19

Tube Coagulase Test: 

Tube Coagulase Test The tube coagulase test detects both free and cell bound coagulase of S. aureus . Bacteria are incubated in plasma for 2-4 hours and the tubes turned on their sides as illustrated. Free coagulase acts on prothrombin and fibrinogen in plasma and forms a fibrin clot (left). In manylaboratories staphylococci are simply differentiated as coagulase positive or coagulase negative without speciation Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 20

Mention commonly used Antibiotic agents for Staphylococcus aureus: 

Mention commonly used Antibiotic agents for Staphylococcus aureus Penicillins However Penicillin developed early resistance Other Beta lactam antibiotics like Ampicillin Macrolide group Vancomycin, Linezolid ( Only in MRSA strains ). Commonly used oral anti staphylococcal antibiotics include the first-generation cephalosporins like cephalexin and cefadroxil. Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 21

 Plate 1a: Staphylococcus aureus resistant to penicillin (P0.5) only. Note the annular radius of the zone of inhibition of 9.5 mm around the cefoxitin (FOX 10) disc.   : 

Plate 1a: Staphylococcus aureus resistant to penicillin (P0.5) only. Note the annular radius of the zone of inhibition of 9.5 mm around the cefoxitin (FOX 10) disc.

What is the importance of Drug resistance in this isolate? : 

What is the importance of Drug resistance in this isolate? MRSA is an acronym for Methicillin Resistant Staphylococcus aureus, a bacteria that has become resistant to many antibiotics, including methicillin, penicillin, amoxicillin, and cephalosporins. It is routinely pronounced M.R.S.A. Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 23

What are the Other Diseases produced by Staphylococcus aureus : 

What are the Other Diseases produced by Staphylococcus aureus Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 24

Other Staphylococcal Diseases: 

Systemic Diseases Toxic shock syndrome-TSS toxin is absorbed into the blood and causes shock Bacteremia-presence of bacteria in the blood Endocarditis-occurs when bacteria attack the lining of the heart Pneumonia-inflammation of the lungs in which the alveoli and bronchioles become filled with fluid Osteomyelitis-inflammation of the bone marrow and the surrounding bone Other Staphylococcal Diseases Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 25

How you Prevent Staphylococcal Infections: 

How you Prevent Staphylococcal Infections Prevention Staphylococcus is a important cause of Hospital infection Hand antisepsis is the most important measure in preventing nosocomial infections Also important is the proper cleansing of wounds and surgical openings, aseptic use of catheters or indwelling needles, an appropriate use of antiseptics Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 26

Slide 27: 

The programme is created for Undergraduate students in Medical Colleges as a part of Applied Microbiology exercises Email doctortvrao@gmail.com Dr.T.V.Rao MD Travancore Medical College, Kollam Kerala 27