Streptococcus pyogenes = Group A Strep(treated by penicillin or macrolides if pt has allergy to penicillin ) Carried by 10-25% of many in throat often no symptoms it is Cause of • strep throat • impetigo • Necrotizing fasciitis Gram +ve cocci in chain Catalase negative
We do also grouping test to differentiate any of all sterpt. Groups you are dealing with.we use antibodies against the cell wall of strept. (Group A strept. Will have a reaction with Anti-A antibody.) Just look like the Blood group test.
Streptococcus pyogenes (induces pus).= Group A Strept Left. Gram stain of Streptococcus pyogenes in a clinical specimen (with some pus cells(neutrophils)which make sure that it induces pus). Right. Colonies of Streptococcus pyogenes on blood agar exhibiting beta (clear) hemolysis (when put the agar against light you will see a complete hemolysis zone (beta hemolysis) )
Strept.A is a Bacitracian sensitive. • Bacitracintest is used for presumptive identification of group A • To distinguish between S. pyogenes (susceptible to B) & non group A such as S. agalactiae (Resistant to B) • Bacitracin disk will inhibit the growth of gp A Strep. pyogenes giving zone of inhibition around the disk
Bacitracin sensitivity Group A strept. Is a bacitracian sensitive. Srept.B is a Bacitracin resistant Associated with neonatal sepsis & meningitis.
Case 1 A 5 year boy was brought to king Khalid University hospital, outpatient department complaining of fever and sore throat. He had regular vaccination history. On examination his temperature was 38.5° c, the tonsil area and pharynx were obviously inflamed with some foci of pus.<<here you exclude viral infection & think more about bacterial’s AB-herpis virus infection, very much resembles bacterial infections because it induces pus & inflamed tonsillitis.
1. What is the differential diagnosis? viral or bacterial infection,e.g. (strept.A)& (Corynebacterium diphtheria if unvaccinated) 2. What investigation should be done? Swab & culture it (gram stain is not recommended because the oral cavity is colonized by numerous normal flora) CBC
Lab tests • The full blood count showed a total white cell count of 15000ml.Throat swab culture showed colonies with clear haemolysis on blood agar. They were catalase negative .The gram stain of these colonies showed gram positive cocci in chains
1. What is the likely identity of the organism? • Catalase negative cocci in chain (Streptococci) (we say it’s A if it’s bacitraicansensetive) • 2. What is the best antibiotic therapy for this child? • penicillin • 3. If not treated what complication may this child have after 6 weeks period? • Rheumatic fever(the heart antigenic structure resembles very much the bacterial antigenic structure,so the antibodies attack the heart instead of the bacteria.the child then will develop leg pain) • Acute glomerulonephritis
Streptococcus pneumoniae(Pneumococci) Causes two fatal diseases : Pneumonia & meningitis Virulence factor: Its capsule alone is the complete story of meningitis. Pneumonia occurred in immunocompromised patients.(especially the humeral immunity is impaired). & Patient with impaired spleen function.
Alpha-hemolysis (partial clearance) • 2 strept. species Can display Alpha-hemolysis:. • "Viridans group strept.(causes endocarditis)“ • Srept. pneumonia.
Optochin Susceptibility Test Optochin resistant S. viridans Optochin susceptible S. pneumoniae This test is done to differentiate between: Viridans & pneumococcus
Strept. Pneumonia is an optochin sensitive Viridans strept. Is an optochin resistant
CASE 2 Fluid or pus infiltrates which causes consolidation Symptoms: fever with chills A 28 Year Old Female presented to the accident and emergency of KKUH with a sudden onset of fever, right sided chest pain and productive cough of purulent sputum. On examination her temperature was 39 °C. There were Rhonci and dullness on the right side of the chest. X-ray showed massive consolidation on the right side of the chest. Whole Lobe consolidation=lobar pneumonia
1. What is the most likely diagnosis? • Pneumonia or (lobar pneumonia to be accurate) • 2. What investigation should be done? • X-ray • CBC(leukocytosis)above11x10^3 • ESR • Sputum analysis(not recommended because it’s colonized by bacteria) • Blood culture (sepsis may occure)
LAB TESTS • The blood counts showed a total white cell count 45,000/ ml 90% of the cells were neutrophils. The sputum culture showed alpha haemolytic colonies on blood agar. The gram stain showed gram positive diplococcic.which were catalase negative This organism was confirmed to be optician susceptible. Culture of sputum
3. What should have been the empirical therapy for this case and why? penicillin if sensetive (MIC>2 so can’t be used). cephalosporins (Ceftraixone) If meningitis is the case we treat withvancomycin & ceftraixone
Sputum Microscopy Organism: Mycobacterium tuberculosis: Stain: Ziehl-Neelsen stain
Mycobacterium tuberculosis (highly infectious<communicable disease>) Growth on L.J medium( selective for mycobacteria Slowly growing, takes 2 weeks to grow
CASE 3 Abdul Karim is a 45 year old Saudi man who was admitted to King Khalid University Hospital because of 2-3 month (chronic) history of loss of appetite, weight loss, and on and off fever with attacks of cough. Two days before admission .he coughed blood (haemoptysis) Abdul karim is diabetic for the last 5 years. His father died of tuberculosis at the age of 45 yrs.
Cavities or open TB is very infectious.(need 2 weeks isolation & anti TB medications) • On examination Abdul Karim looked weak with a temperature 38.6 °C, CVS and Respiratory system examinnation was unremarkable. • The chest X- ray done showed multiple opacities and cavities (mean that it’s a reactivated disease) • The ESR was increased (85 m /hour) • What further tests should be done?
Sputum AFB smear • Sputum smear showed AFB • What is the probable diagnosis? • openTB,open pulmonary TB • How can the diagnosis be confirmed? Culture on L.J. medium PCR
Gram positive, cocci, in clusters (Staphylococci) If catalase positive,so it is Staph.areus (induces pus & abscesses)
Staphylococci Stained in Pus
Vaginal Smear of a Person with Candida Vaginitis May cause pneumonia in immunocommpromised pt. Note epithelial cells, rod-shaped bacteria, and Candida albicansin its hyphal form
Candida albicans Producing Germ tube Dimorphic Candida albicans switching from a yeast form to a filamentous form
Gram stain of candida: ovoid budingYeast Chlamydospore causes: oral thrush
Aspergillus niger Culture of Aspergillus niger(black). Conidial head of A. niger Aspirgillus pneumonia need a biopsy to diagnose it
Aspergillosis Methenamine silver (GMS) stained tissue section of lung showing dichotomously(45 degree division) branched
These information has been added after listening to Dr.Fawzia practical lecture. Good luck Done by: Khulud Alenzy