Please answer the questions below in approximately 200 words. DO NOT PLAGERIZE. Reference sources. ESSAY. Write your answer in the space provided or on a separate sheet of paper. 1) Antibiotics can...

Please answer the questions below in approximately 200 words
Please answer the questions below in approximately 200 words. DO NOT PLAGERIZE. Reference sources.
ESSAY. Write your answer in the space provided or on a separate sheet of paper.
1) Antibiotics can kill gram-negative bacteria, but symptoms of fever and low blood pressure can persist. Why?
Ans. Gram negative bacteria have lipopolysaccharide (LPS) in the outer mem
ane of their cell wall that is toxic to
specific hosts. This LPS in an endotoxin because it is bound to the bacterium and is released when microorganism lyses.
Thus antibiotic can kill gram-negative bacteria but this will lead to release of LPS endotoxins. The toxic component of the
LPS is the lipid portion called Lipid A. Lipid A is not a single macromolecule but is an a
ay of different lipid residues.
This component shows all the characteristic properties associated with the endotoxicity and gram-negative bacterimia.
Bacterial endotoxins are usually capacble of producing general systemic effects like fever, shock, blood coagulation,
weakness, dia
hea and fi
inolysis. Gram-negative endotoxins also indirectly induce a fever in the host by causing
macrophages to release endogenous pyrogens that reset the hypothalamic thermostat. One important endogenous pyrogen
is cytolkine IL-1. Other cytokines released by macrophages such as tumor necrosis factor (TNF) also produces fever. Thus
also gram-negative bacteria is killed by the antibiotic, it can still lead to fever and low blood pressure due to its endotoxins.
2) Why is diagnosis of botulism difficult?
Ans. Botulism is caused by an exotoxin produced by Clostridium botulinum. This microbe is an obligate anaerobe,
endospores-forming, gram-positive rod and is found in soil and aquatic sediments. The most common source of infection is
home-canned food that had been heated insufficiently and thus contaminating spores of C.botulinum are not killed. The
otulism toxin is a neurotoxin. Symptoms of botulism occur within 12 to 72 hours of toxin ingestion and include blu
ed
vision, difficulty in swallowing and speaking, muscle weakness, nausea and vomiting. Laboratory diagnosis is restricted to
laboratory response network facilities and is demonstrated by the presence of toxin in stool, serum or vomit of patient.
However, diagnosis of botulism is difficult because toxin might not be present in the sample. It might also lead to inco
ect
diagnosis because symptoms of botulism are very similar to some other neurological diseases like polymyositis, stroke,
lyme disease, Guillain-Ba
e Syndrome, etc. The laboratory tests which are used for diagnosis of this disease can take upto
4-5 days and diagnostic kit might not be available in all laboratories. ELISA test can be used but this test detects both
active as well as inactive toxins which might give a false positive results.
3) Explain how each of the following avoids being killed by phagocytes.
a. Streptococcus pneumoniae

Ans. Streptococcus pneumoniae is a gram-positive pathogenic microorganism and it has a thick capsule which is the
most important virulence factor responsible for its pathogenicity. This capsule helps the microbe to minimize being
phagocytosed. The capsule is polysaccharide in nature which inhibits phagocytosis with the help of its chemical
composition and resists by interfering with the binding of complement C3b on the surface of the cell.
. Mycobacterium tuberculosis

Ans. Mycobacterium tuberculosis are intracellular pathogens of human beings and they act as phagosome within the
host bosy which helps them to survive. When these microbes are injested by macrophages, they act as phagosome which
does not fuse with lysosome and thus prevents formation of phagolysosome. Hence they are not exposed to lysosomal
hydrolase enzyme and thus avoid being phagocytosed.
c. Streptococcus pyogenes

Ans. Streptococcus pyogenes are gram-positive non-spore forming, non-motile anaerobic bacterium which produces
streptolysin toxin. This toxin repels chemotactic activity and also induces lysosomal siacharge into the cytoplasm which kills
phagocyte. The cell wall of this organism is made of M-proteins which also helps to resist phagocytosis. The capsule of
Streptococcus pyogenes is made up of hyaluronic acid and it is similar to connective tissue of human beings. This acid helps it
to be not recognized as an antigen within the host body which further help the bacteria not to be phagocytosed.
d. Shigella dysenteriae
4) A patient consulted a physician for symptoms that included a swollen toe, a red streak along his ankle, and enlarged
lymph nodes in his groin. Explain the cause of these symptoms.
Ans.
These symptoms indicate a condition called lymphedema which is also called lymphatic obstruction. Lymph is a clear fluid
which ca
ied with the help of lymphatic vessels through out the body. When the flow of lymph is blocked, then it might lead
to accumulation of lymph in the su
ounding tissue which leads to lymphedema. It can be primary or secondary. Primary
lymphedema can be present from birth or can occur during puberty specifically in females. In primary lymphedema,
lymphatic channels are missing. The symptoms of primary lymphedema are swollen leg and sometimes entire lower
extremity becomes swollen. Secondary lymphedema occurs mostly due to infection and it starts with chills, fever and swollen
legs. Red streaks which are called lymphangitic streaks may also be present over a large area on the skin. It also leads to
enlargement of groin due to enlargement of lymph nodes in the groin. These features may distinguish it from acute infection
in the veins or thrombophlebitis (venous inflammation). Damage of lymphatic vessels leads to swelling. The infection can be
caused by Staphylococcus aureus.
5) A person has antibodies against the measles virus. Identify three ways in which these antibodies could be acquired.
Ans. Acquired immunity refers to the type of specific (adaptive) immunity a host...