Who am i
Gram positive cocci
clusters
Catalase positive
Coagulase negative
Novobiocin sensitive
Staphylococcus epidermidis
Treatment St. pneumonia
High-dose penicillin G appears to be effective in treating pneumonia caused by pneumococci
Most people who are diagnosed early with bacterial meningitis and treated promptly will recover fully.
The correct answer is A. True.
But in some cases, the bacterial infection can progress so quickly that the person dies within 48 hours, even with treatment. The bacteria that cause meningitis are becoming resistant to many of the antibiotics that were once used to treat it. Newer, more expensive medicines must now be used.
You are the luckiest student)
push up 20times
Ophtalmia neonatorum
Newborn gonococcal ophtalmia which results from direct infection during passage through birth canal
Gram positive cocci
Appear in clusters
Catalase positive
Coagulase positive
Staphylococcus aureus
Lets mix the numbers
Try your luck
18-81
81-18
Morphology
Meningococci are gram-negative
Oval or spherical shape 0.6- 0.8 arranges typically in pairs with adjacent sides flattened, they are non-motile
Prevention and control:
Vaccine is not available
Early detection of new causes, contact tracing, health education
Exfoliative (epidermolytic) toxin
is responsible for the staphylococcal scalded skin syndrom
The outer layer of the epidermis gets separated from the underlying tissues.
Ritter s disease in newborn
toxic epidermal necrolysis - in older patients.
milder porms : pemphigus neonatorum , bullous impetigo.
Gram positive cocci
chains
Catalase negative
Beta-hemolytic
Bacitracin sensitive
Streptococcus pyogenes
Morphology
Individual cocci are spherical or ovoid and are arranged in chains . The cocci divide in a plane perpendicular to the long axis of the chain. The members of the chain often have a striking diplococcal appearance, and rodlike forms are occasionally seen. The lengths of the chains vary widely and are conditioned by environmental factors. Streptococci are Gram-positive; however, as a culture ages and the bac- teria die, they lose their Gram positivity and can appear to be Gram-negative; for some streptococci, this can occur after overnight incubation.
Most group A strains produce capsules composed of hyaluronic acid. The capsules are most notice- able in very young cultures. They impede phagocytosis. The S. pyogenes cell wall contains proteins (M, T, R antigens), car- bohydrates (group specific), and peptidoglycans. Hairlike pili project through the capsule of group A streptococci. The pili consist partly of M protein and are covered with lipoteichoic acid. The latter is important in the attachment of streptococci to epithelial cells.
choose letter
a
b
c
a sing a song
b dance
c sing a song anyway
Morphology
Diplodoccus, adjacent side concave, typically kidney shape. Posseses pilli on its surface responds for adhesion to mucosal surface and promote virulence factor by inhibiting the phagocytosis
Enzymes and Toxins Staphylococci
Catalase, which converts hydrogen peroxide into water and oxygen. Staphylococci+ versa streptococci-
Coagulase an enzyme like protein that clots oxalated or citrated plasma. Coagulase binds to prothrombin; together they become enzymatically active and initiate fibrin polymerization. - invasive pathogenic potential.
Clumping factor is cell wall bound , that is responsible for adherence of the organisms to fibrinogen and fibrin. When mixed with plasma, S. aureus forms clumps.
hyaluronidase
4 Hemolysins
Panton–Valentine Leukocidin has two components, is encoded on a mobile phage. It can kill white blood cells of humans and rabbits.
Exfoliative Toxins
Toxic Shock Syndrome Toxin which is the same as enterotoxin
Enterotoxins There are 15 enterotoxins (A–E, G–P) are superantigens. Important cases of food poisoning, enterotoxins are produced when S. aureus grows in carbohydrate and protein foods.
Gram positive cocci
clusters
Catalase positive
Coagulase negative
Novobiocin resistant
Staphylococcus saprophyticus
Cultivation
Growth of streptococci tends to be poor on solid media or in broth unless enriched with blood or tissue fluids. Nutritive requirements vary widely among different species. The human pathogens are most exacting, requiring a variety of growth factors. Growth and hemolysis are aided by incubation in 10% CO2. Most pathogenic hemolytic streptococci grow best at 37°C. Most streptococci are facultative anaerobes and grow under aerobic and anaerobic conditions
cultural characteristics
required medium enriched with blood, serum, ascitic fluid, aerobes, 5-10% CO2, high humidity,35-36C pH7.4-7.6
On solid med incubation period for 24 hours, the colonies small translucent, round, convex, bluish grey,
Blood agar, chocolate agar and Mueller-hinton starch casein hydrolysate agar. modified Thayer-Martin (vancomycin, colistin, nystatin) for selective med.
Treatment
Ceftriaxon with azitromicin or doxycycline
Resistance to drugs of staphilococci
Penicilin resistance
Production of beta lactamase ( penicilinase), inactivates penicillin by splitting the beta lactam ring.
Alterations in the penicillin binding protein PBP2a (a unique transpeptidase that is not inhibited well by β-lactam antibiotics) and changes in bacterial surface receptors, reducing binding of beta lactam antibiotics to cells. MRSA
Development of tolerance to penicillin, by which the bacterium is only inhibited but not killed.
Gram positive Diplococcus
Catalase negative
Alpha hemolytic
Bile esculin negative
Optochin susceptible
Streptococcus pneumoniae
Pyrogenic Exotoxins (Erythrogenic Toxin)
Pyrogenic exotoxins are elaborated by S. pyogenes. There are three antigenically distinct streptococcal pyrogenic exotoxins (Spe): A, B, and C. SpeA has been most widely studied. It is produced by group A streptococci that carry a lysogenic phage. The streptococcal pyrogenic exotoxins have been associated with streptococcal toxic shock syndrome and scarlet fever. Most strains of group A streptococci isolated from patients with streptococcal toxic shock syndrome either produce Spe A or have the gene that codes for it; in contrast, only about 15% of group A streptococci isolated from other patients have the gene. Spe C, also encoded by a phage, may contribute to the syndrome. Spe B, a potent protease, interferes with phagocytosis. The group A strep- tococci associated with toxic shock syndrome are primarily of M protein types 1 and 3.
The pyrogenic exotoxins act as superantigens, which stimulate T cells by binding to the class II major histocompatibility complex in the Vβ region of the T-cell receptor. The activated T cells release cytokines that mediate shock and tissue injury. The mechanisms of action appear to be similar to those caused by staphylococcal toxic shock syndrome toxin-1 and the staphylococcal enterotoxins.
Laboratory diagnosis
CSF, blood , NP swabs, scin scrapping from petechial lesions
CSF 3 portions
1- is centrifuged and Gram stained smear are prepared for deposit
2-inoculated on blood or chocolate agar plates and incubated at 33-36C under 5-10%CO2. Colonies will appear after 18-24 hours, can be identified by morphology and biochemical reactions
3-is incubated overnight with adding equal glucose broth, then subcutured on chokolate agar.
blood culture ( incubation 4-7days) -meningococcemia, in early cases meningitis - is often +
nP swab- for detection of carriers
Petechial lessions MG by microscopy and culture
Autopsy meninges, lateral ventricles or the surface of the brain and spinal cord for smear/culture, before 12 hours of the death
Serolofy: detection of antibodies.
Crede’s method
Instilling of 1% silver nitrate solution to newborn babies
“Toxic shock syndrome” is caused by the toxin of
a. Staphylococcus aureus
b. Streptococcus pyoge
c. Vibrio cholerae
d. Candida
Answer is A
extra 20 points