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A Gram stain is performed to show Gram-positive cocci in chains. Then, the organism is cultured on blood agar. The rapid pyrrolidonyl arylamidase (PYR) test is commonly used, wherein a positive reaction confers a presumptive identification of group A beta-hemolytic streptococci if the appearance and clinical context is consistent.
The term "atypical" does not relate to how commonly these organisms cause pneumonia, how well it responds to common antibiotics or how typical the symptoms are; it refers instead to the fact that these organisms have atypical or absent cell wall structures and do not take up Gram stain in the same manner as gram-negative and gram-positive ...
Enterococcus faecalis – formerly classified as part of the group D Streptococcus system – is a Gram-positive, commensal bacterium inhabiting the gastrointestinal tracts of humans. [1] [2] Like other species in the genus Enterococcus, E. faecalis is found in healthy humans and can be used as a probiotic.
As mentioned, S. agalactiae is a Gram-positive coccus with a tendency to form chains, beta-haemolytic, catalase-negative, and facultative anaerobe (anaerobic organism). GBS grows readily on blood agar plates as microbial colonies surrounded by a narrow zone of β-haemolysis.
The encapsulated, Gram-positive, coccoid bacteria have a distinctive morphology on Gram stain, lancet-shaped diplococci. They have a polysaccharide capsule that acts as a virulence factor for the organism; more than 100 different serotypes are known, and these types differ in virulence, prevalence, and extent of drug resistance.
Streptococcus bovis is a group of strains of Gram-positive bacteria, originally described as a species, [5] [6] that in humans is associated with urinary tract infections, endocarditis, sepsis, [7] and colorectal cancer. [8] S. bovis is commonly found in the alimentary tract of cattle, sheep, and other ruminants, [9] and may cause ruminal acidosis.
Streptococcus is a genus of gram-positive or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales (lactic acid bacteria), in the phylum Bacillota. [2] Cell division in streptococci occurs along a single axis, thus when growing they tend to form pairs or chains, which may appear bent or twisted.
Enterococci are Gram-positive cocci that often occur in pairs or short chains, and are difficult to distinguish from streptococci on physical characteristics alone. [2] Two species are common commensal organisms in the intestines of humans: E. faecalis (90–95%) and E. faecium (5–10%).