The Enterics

The correct answer is O (outermost part of LPS), K (capsule just outside the O antigen), H (flagella on motile bacteria). The O antigen is the outermost part of the lipopolysaccharide (LPS) in the cell wall of enteric bacteria. The K antigen refers to the capsule that is located just outside the O antigen. The H antigen represents the flagella found on motile bacteria. These surface antigens play important roles in the identification and classification of enteric bacteria.

c) Escherichia coli and most of Enterobacteriaceae ferment lactose but Salmonella, Shigella and Pseudomonas aeruginosa do not!!
d) All have O antigen (LPS), but K(capsule) and H (flagella/motile) antigen are only present on some.

E. coli is capable of fermenting lactose, converting it into gas and acid, which can be visualized with a pH dye.

The family Enterobacteriaceae includes various genera of bacteria that are commonly found in the intestines of humans and animals. These bacteria are gram-negative, facultative anaerobes, and are often associated with gastrointestinal infections. E. coli, Klebsiella, Proteus mirabilis, Enterobacter, Serratia, Shigella, Salmonella, and Yersinia enterocolitica are all members of the Enterobacteriaceae family. However, Campylobacter jejuni is not a member of this family. Campylobacter jejuni is a curved, gram-negative bacterium that is a common cause of foodborne illness, specifically causing gastroenteritis in humans. It belongs to the Campylobacteraceae family, not Enterobacteriaceae.

The statement "methelene blue in the medium inhibits gram-positive growth" is not true about MacConkey agar. MacConkey agar contains bile salts which inhibit the growth of gram-positive bacteria, not methylene blue. Additionally, lactose fermenters on MacConkey agar take on a pink-purple color, not a metallic green sheen. Therefore, the correct answer is b and c.

This answer is correct because it accurately describes the characteristics of enterohemorrhagic Escherichia coli and Salmonella enteritidis infections. These enterics invade the intestinal epithelial cells using virulence factors, leading to the destruction of cells and a systemic immune response. This immune response causes local white blood cell infiltration, resulting in the presence of pus in the stool and fever. However, there is no presence of red blood cells in the stool in these infections.

The given correct answer is "c and e". This means that the statements "Bile salts inhibit gram-positive bacteria" and "lactose fermenters become pink-purple" are not true about EMB agar. EMB agar actually contains bile salts, which inhibit the growth of gram-positive bacteria. Additionally, lactose fermenters on EMB agar produce colonies that are typically deep purple to black in color, not pink-purple.

The correct answer is Enterobacteriaceae, Vibrionaceae, Pseudomonadaceae, and Bacteroidaceae. These four groups are the main classifications of enteric bacteria. Enterobacteriaceae includes common pathogens such as Escherichia coli and Salmonella. Vibrionaceae consists of bacteria like Vibrio cholerae, which causes cholera. Pseudomonadaceae includes Pseudomonas aeruginosa, a common cause of hospital-acquired infections. Bacteroidaceae includes Bacteroides fragilis, which is a normal inhabitant of the human gastrointestinal tract. These groups are important in clinical microbiology and have unique characteristics and clinical significance.