Streptococcus Viridans

Fatality rates for left-sided disease are greater than those for right-sided disease because of the increased incidence of cardiac failure and neurologic complications. Streptococcus viridans is the most common organism implicated in left-sided endocarditis, with Staphylococcus aureus increasing in incidence.

Enterococcal and fungal infections are also seen. Right-sided endocarditis is caused by S. aureus in more than 75 percent of cases, followed by S. viridans and gram-negative rods. Blood cultures should be drawn from three different venous sites and sent for aerobic, anaerobic, and fungal cultures. Antifungal agents should be considered in patients with HIV or other immunocompromised states or in patients with indwelling catheters. Murmurs are heard in only 35 to 50 percent of patients with right-sided disease but in up to 80 percent of patients with left-sided disease.

During the lag time, by definition, bacteria newly introduced into a culture will undergo metabolic changes necessary for use of the medium, but will NOT increase in number.

Therefore, at the end of the first 30 minutes elapsed time, the number of bacteria in the culture will be 2 x 10^2.

Thereafter, the number of bacteria will double every 20 minutes (the definition of generation time).

This means that after 2 1/2 hours of total elapsed time, 6 generations will have occurred, so the original inoculum number is multiplied by 2, 6 times.

Ans. is ‘a’ i.e. S. viridans, ‘b’ i.e. S. aureus

Causative organisms of community acquired infective endocarditis

.  Staphylococcus aureus ( most common)

.   Streptococcus ( Str viridans, Str bovis, other non group A Streptococci)

.  Others- Enterococcus, Coagulase negative Streptococci ( Stop epidermidis), HACEK group, Pneumococcus, candida

Ans. is ‘a’ i.e., Streptococcus viridans

.  Viridans streptococci are normally resident in the mouth and upper respiratory tract. They cause transient bacteremia following tooth extraction or other dental procedures; and get implanted on damaged or prosthetic valves or in a congenitally diseased heart, and grow to form vegetations.

Ans. is ‘c’ i.e., Pneumococcus 

On blood agar, after incubation for 18 hrs, the colonies of pneumococci are small, dome shaped and glistening with an area of green discoloration (alpha hemolysis) around them, resembling colonies of Str. viridans.

Ans:C i.e. Streptococcus viridans

Subacute bacterial endocarditis/Endocarditis lenta

• It can be considered a form of Type III hypersensitivity.
• It is usually caused by a form of streptococci viridians bacteria that normally live in the mouth and throat (Streptococcus mutans, mitis, sanguis or milleri).
• Osler’s nodes can indicate this condition.
• Nail clubbing is also often seen in subacute endocarditis.
• In cases of subacute bacterial endocarditis, the causative organism (streptococcus viridans) needs a previous heart valve disease to colonize and cause such disease.
• On the other hand, in cases of acute bacterial endocarditis, the organism can colonize on the healthy heart valve, causing the disease.

Ans. is ‘a’ i.e., Streptococcus viridans

• Viridans streptococci are normally resident in the mouth and upper respiratory tract. They cause transient bacteremia following tooth extraction or other dental procedures; and get implanted on damaged or prosthetic valves or in a congenitally diseased heart, and grow to form vegetations.
• They are ordinarily nonpathogenic but can on occasion cause disease. In persons with preexisting cardiac lesions, they may cause bacterial endocarditis, Str. sanguis being most often responsible.
• Str. mutans is important in causation of dental caries.
• The transient viridans streptococcal bacteremia induced by eating, tooth-brushing, flossing and other source of minor trauma, together with adherence to biological surfaces, is thought to account for the predilection of these organisms to cause endocarditis.
• Viridans streptococci are also isolated, often as a part of a mixed flora, from sites of sinusitis, brain abscess and liver abscess.
• Viridans streptococcal bacteremia occurs relatively frequently in neutropenic patients, particularly after bone marrow transplantation or high dose chemotherapy for cancer.

Treatment of varidans streptococcal infections include :-

1. Bacteremia in neutropenic patients → Vancomycin.
2. Other infection → Penicillin.

Ans. is ‘d’ i.e., Streptococcus viridans

The dominant etiologic agents, accounting for more than 85% of cases of urinary tract infection, are the gram-negative bacilli that are normal inhabitants of intestinal tract.

By far the most common is Escherichia coli, followed by proteus, klebsiella, and Enterobacter.

In most patients with urinary tract infection, the infecting organisms are derived from the patient’s own fecal flora. This is thus a form of endogenous infection.