all details you need to know about staphylococcus group alpha ( Strp. Viridans and Strp. Pneumonea ) diseases characteristics laboratory diagnosis treatments
Strept. Viridans :
❖ Characteristics
:
○ Gram +ve \ Catalase –ve \ cocci in pairs \ optochin and bile resistant \ cause
incomplete hemolysis of blood with green surrounding
○ Can reach blood in dental surgery, brushing , bleeding gums.
○ Most common cause of subAcute endocarditis.
8
○ Normal flora of the mouth ( 1 mL of saliva contain 10 bacteria), upper
respiratory tract.
❖ Virulence
:
○ produce glycocalyx (dextrans) that enables them to adhere to the cardiac valves,
and acids as end products of metabolism.
○ NO exotoxins or tissue destructive enzymes
❖ Diseases
:
1‐ Dental caries
by depositing of glucan on the surface of teeth done by S. mutans
2‐ Subacute bacterial endocarditis (SBE), occurs when the bacteria reaches the blood
and then reaches the heart valves
that are already damaged > Signs of
endocarditis are fever, heart murmur, anemia. Murmur is due to vegetation of the
bacteria on the heart valves
3‐ Septicemia : by entering the blood secondary to settlement on the valves, causing
fever and hypotension.
4‐ Brain abscess,especially Str. anginosus, Str. milleri, and Str. intermedius, also cause
brain abscesses, often in combination with mouth anaerobes (a mixed aerobic–
anaerobic infection)
❖ Treatment
:
Penicillin G or erythromycin if the pt. is sensitive
❖ Laboratory Diagnosis
:
○ Specimen collection :
blood, pus
○ Direct microscopy :
gram +ve diplococci
○ Culture :
▪ Blood agar :
incomplete blood hemolysis with green colonies.
○ Biochemical tests :
▪ Optochin resistance : +ve
▪ Bile resistance : +ve
▪ Quellung Reaction: ‐ve
▪ Inulin fermentation : ‐ve
, Strept. Pneumoniae :
❖ Characteristics
:
○ Gram +ve\ Catalase –ve \ cocci in pairs
or short chains \ diplococci lancet shape "
with pointed ends "
○ also known as the pneumococcus.
○ Normal flora of upper respiratory tract.
❖ Virulence :
1‐ IgA protease.
2‐ Polysaccharide capsule which is anti‐phagocytic
3‐ C‐polysaccharide which react with C‐reactive protein, Normal individuals are
resistant to pneumococci because of the body's ability to eliminate it.
❖ Predisposing factors
:
1‐ Any problem that affect the cough reflex increasing aspiration, like alcohol ingestion
cause neurological problems, anesthesia
2‐ Any problem that affect the respiratory tract causing the disruption of the
mucociliary blanket
3‐ Splenectomy, spleen removes bacteria from blood.
4‐ Abnormal circulatory dynamics (e.g., pulmonary congestion and heart failure)
5‐ Sickle cell anemia, this disease auto infarct the spleen making it non functional
leading or predisposing the patient to pneumococcal septicemia
6‐ Trauma to the head may cause leakage of CSF through the nose causing
pneumococcal meningitis.
❖
Diseases:
1‐ Typical Pneumonia ( most common cause ) often begins with a sudden chill,
fever, cough, and pleuritic pain. Sputum starts as yellowish greenish sputum
and turns red or brown “rusty” color. Bacteremia occurs in 15% to 25% of cases.
Spontaneous recovery may begin in 5 to 10 days and is accompanied by
development of anticapsular antibodies.
2‐ otitis media, sinusitis, mastoiditis, conjunctivitis, purulent bronchitis, (
most
common cause )
3‐ Bacterial meningitis , (
most common cause in adults ).
4‐ sepsis. Pneumococci are the leading cause of sepsis in patients without a
functional spleen.
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