lec10.docx

**Faculty of Dental medical** **Lecture : 10** **Gram positive cocci** B. **Streptococcus** C. **Enterococcus** 1. More than 50 species, the most important are - ***S. pyogenes*** - ***S. agalactiae*** - ***S.* viridans** - ***S. pneumoniae*** 2. Gram positive cocci 3. Arrang...

**Faculty of Dental medical** **Lecture : 10** **Gram positive cocci** B. **Streptococcus** C. **Enterococcus** 1. More than 50 species, the most important are - ***S. pyogenes*** - ***S. agalactiae*** - ***S.* viridans** - ***S. pneumoniae*** 2. Gram positive cocci 3. Arranges in chain or pairs 4. Facultative anaerobes 5. Grow in enriched media 6. Catalase (-) 7. No spore, no motile **Classification of Streptococci** i. Hemolysis on Blood agar - B- hemolysis ( *S.pyogenes , S. agalactiae* ). - Alpha hemolysisi ( *S. pneumonia )* - No hemolysis ( S. *bovis)*  ii. **Lancefield classification:** classifying streptococci based on the presence of polysaccharide and teichoic acid antigens in the bacterial cell wall  ***Streptococcus Pyogenes* ( Group A ) beta hemolytic** **Culture:** Facultative anaerobes grow in Blood agar at 37c for 24h in clear hemolytic small colonies ( this colony break the RBC of the Blood agar )  **Virulence factor** 1. **Adherence ( M protein ) :** is major surface protein of *S.pyogenes* helps the bacteria evade the immune system by interfering with phagocytosis and killing. 2. **Hyaluronic acid capsule :** ( similar to host hyaluronic acid ) this acid protect the bacteria from phagocytosis and produce hyaluronidase that break the tissue of the host. 3. **Streptokinase :** convert plasminogen to plasmin that dissolved fibrin clot and invasive to cells this proses could be used as a treatment for people that have a heart attack by dissolved blood clots.( in medicine form) 4. **Streptolysin :** there is 2 types of sterptolysin : sterptolysin O (SLO) and sterptolysin S (SLS). sterptolysin are toxins that can damage host cells , including Red and White blood cells, (SLO) itis oxygen labile and causes beta- hemolysis on blood agar , sterptolysin S is an oxygen stable ( SLS) does not cause complete lysis of red blood cells on blood agar. ***Streptococcus pyogenes:** produce a* Pyrogenic exotoxins **( A,B,C)** *S. pyogens* produces pyrogenic exotoxins , alo known as Streptococcal Pyrogenic exotoxins ( SPEs). These toxins are responsible for the characteristic symptoms of Streptococcal infections including **fever, rash, and scarlet fever and Toxic shock syndrome** (similar to staphylo toxic shock). ***Streptococcus pyogenes* disease*:*** i. **Pyogenic local infection** ( pharyngitis, Tonsillitis ) 1. Acute follicular Tonsillitis transsmited by droplets and cause ( fever , Enlarged tonsils with exudate , enlarged cervical lymph nodes) 2. Otitis media 3. Impetigo similar to staphylococcus, usually found on the face , legs arms and trunk.  ii. **Puerperal sepsis:** infection of the fetus after delivery or abortion by contamination of *S. pyogenes* during delivery and cause Endometritis then Septicemia that lead to Puerperal sepsis , the symptoms include high fever , Purulent vaginal discharge , septicemia , toxic shock iii. **Acute endocarditis.** iv. **Scarlet fever :** Characterized by : - Fever - Tonsillitis - Red skin rash - Strawberry tongue - Vomiting and abdominal pain  v. **Necrotizing fasciitis** : this disease produce a protease that destroys normal tissue and cause necrotizing vi. **Streptococcal toxin shock syndrome :** cause an organ failure. vii. **Acute rhematic fever ( RF ):** the antibody of S.pyogenes bind with the joints and lead to ( RF) that cause to migrating polyarthritis. viii. **Acute glomerulonephritis.** **Lab diagnosis of *S. pyogenes*** 1. **Specimen** 2. **Direct smear** 3. **Cultivation** 4. **Identification** i. **Specimen :** according the side of infection - Throat swab, Swap from lesions , Pus swab , Uterine swab , blood for blood culture ( acute endocarditis) ii. Direct smear  iii. Cultivation : on blood agar at 37c for 24h iv. Identification : Beta hemolysis colonies on blood agar **Colonies Identified by :-** 1. Gram staining 2. Catalase test : Neg (-) 3. Bacitracin test ( sensitive )  **S. agalactiae : group B , B hemolytic streptococci.** **Morphology & culture:** - Gram (+) cocci arranged in chain - Capsulated - Non -- motile - Non -- spore forming **Culture:** facultative anaerobic, grow in blood agar at 37c for 24 h. **Diseases:** They inhabit about 25% of pregnant women (Vagina ), during delivery the baby could have **neonatal pneumonia ,** **neonatal septicemia , neonatal meningitis.** **Lab diagnosis :** 1. cultivate a vaginal swab on blood agar at 37c for 24h 2. Identification: B hemolytic colonies 3. Gram staining : G+ cocci arranged in chain 4. Bacitracin test : Resistant **Treatment**: Intravenous ampicillin at least 4 hours prior to delivery. **S. viridans , alpha -- haemolytic streptococci.** **Morphology & culture:** - Gram (+) cocci arranged in chain - Capsulated - Non -- motile - Non -- spore forming **Culture:** facultative anaerobes , grow in blood agar at 37c for 24 h **Diseases :** These bacteria are found in ( oral cavity, GIT , female genital tract ) and cause : 1. Dental caries ( synthesize large sticky polysaccharides ) 2. Subacute bacteria endocarditis : patient with rheumatic heart disease had a tooth extraction or tonsillectomy that's may lead to subacute endocarditis **Lab diagnosis:** 1. Specimen from blood and do a blood culture 2. Subculture on blood agar that gives a greenish alpha hemolytic colonies 3. Gram staining 4. Optochin test : Resistant **S. pneumonia , alpha -- haemolytic streptococci.** **Morphology & culture:** - Gram positive cocci arranged in Pairs ( diplococcic ) Capsulated - Non -- motile - Non -- spore forming There are at least 90 serotypes of pneumococci based on **polysaccharide** **Culture :** Facultative anaerobes grow on blood agar ( alph hemolytic ) this bacteria has the ability to convert the hemoglobin to methemoglobin and produce a greenish colonies  This bacreia found in nasopharynx as a carrier **Diseases -- predisposing factors** 1. Immunosuppression 2. Viral infection 3. Respiratory infection 4. Alcoholism 5. Smoking **Diseases:** - **Labor pneumonia :** by droplet or nasopharynx that goes to lung and lead to - Labor pneumonia - **Sinusitis :** it is an inflammation of paranasal sinuses - **Otitis media.** - **Meningitis :** it is an inflammation of meninges ( layers that cover the brain ) **Lab diagnosis:** 1. Specimen from sputum for pneumonia , ear swab for otitis media , nasal swab for sinusitis , CSF for meningitis , blood for endocarditis Direct smear : gram positive cocci in pairs (diplococcic ) 2. Cultivation : on blood agar at 37c for 24h 3. Identification: alpha hemolytic colonies on blood agar 4. Gram staining 5. Catalase test : Neg (-) 6. Optochin test : sensitive 7. Quelling reaction : swilling of capsule 8. Bile solubility : clear in s. pneumonia (sensitive) **C. Enterococcus** **General features of enterococcus:** 1. There is two medical important - **E. faecalis** - **E. faecium** 2. Gram positive cocci , arranged in short chain / pairs 3. Facultative anaerobes 4. Catalase neg (-) Q\) why it is not with streptococcus group??? Because : grow at 45c , salt tolerant ( not in streptococci ). **Morophology and culture** - Gram positive cocci arranged in pairs - Capsulated - Non motile , non spore forming - Grow in blood agar , non hemolytic colonies and grow in macconkey agar and gives pink colonies - **E. faecalis** **Diseases:** Used as indicator of fecal pollution of water 1. UTI 2. Wound infection 3. Bacteremia **Lab diagnosis** 1. **Specimen :** ( urine culture , blood for blood culture , wound swab) 2. **Direct smear** ( gram positive cocci) 3. **Cultivation** ( blood agar , macconkey agar ) 4. **Identification** ( catalase - , esculine test + with dark brown)