Case 5: A 75 year old male had hip replacement surgery. He was placed on IV prop
ID: 243217 • Letter: C
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Case 5: A 75 year old male had hip replacement surgery. He was placed on IV prophylactic antibiotics during his hospital stay and oral antibiotics for ten days after returning home. Two weeks after the surgery, he had symptoms of severe abdominal pain and diarrhea. Stool cultures were sent to the laboratory. The stool specimen submitted was a watery consistency. Aerobic culture results showed very little normal flora present. 1 What factors predisposed this patient to diarrhea? 2 What are some clues as to the source of the infection? What organism is the source of the infection? 3 What laboratory test should be performed to determine the source of the infection?Explanation / Answer
Case 5 Solution:
Since the patient was already on Prophylactic Antibiotics and then Oral Antibiotics, this can cause the problems mentioned in the case.
To understand this, we need to have two pre-requisites:
A) We have abundant normal flora. i.e., microorganisms in various parts of our body that live in a mutual relationship with us. They are non-disease causing under normal circumstances but can be pathogenic if the host doesn't have adequate immunity. These microorganisms help us fight infections by outside pathogens by competing for nutrition and space to live. These microorganisms are also very sensitive to the antibiotics we take.
B) The way the antibacterials act is by selectively targetting bacterial components regardless the bacteria are normal flora or pathogens.
During antibiotic therapies, normal gut flora is also affected.This upset of balance paves way for other bacteria to invade/breach the gut. Also, this flora is responsible for digestion of certain compounds in our foods.
1) As per the above explanation, it can be said that disturbance of normal flora gives rise to these symptoms.
2) Watery diarrhea is seen in cases of bacterial or viral infection, But in case of heavy antibiotic usage, it has been seen that Clostridium difficile overgrows in the gut and causes diarrhea. Without normal flora to keep a check, C. difficile numbers increase in the gut and cause disease. The bacteria and their spores are found everywhere- from normal flora to water and meat. Hence, they can cause diarrhea to patients post-surgery who are on heavy antibiotics. Water quality of the house, food intake of the patient should be closely evaluated to determine the cause of spread.
3) C. difficile is an anaerobic bacteria. Culture should be done under anaerobic conditions, not aerobic. Culture can be done from stool samples.
Case 6 Solution:
Though rare, it is common to get post-operative infections which can manifest as Surgical Site Infections, Chest infections, or bacteremias.
1) There can be many sources of the infections. It can be because of medical negligence, sterile equipment may not have been used during and after the surgery. Also, this can be a caused by several nosocomial opportunistic agents, which are present in different sites in a hospital and invade admitted patients. During postop, patients are susceptible to infections because heavy antibiotics kill the normal flora which protects hosts from many pathogens. Moreover, there are many resistant strains. If they are present in hospitals, they can cause diseases despite on antibiotic treatment. Since it has been mentioned already, the causative organism is S.aureus which is a part of normal flora of the skin, but can colonize and adhere to medical devices and reach the inner body and cause infections or even can cause superficial infections in susceptible hosts. There is a growing concern over Methicillin-Resistant Staphylococcus Aureus or MRSA.
2) MRSA is resistant to treatment not just by methicillin, but all Beta-Lactam antibiotics which includes Penicillins, all generation Cephalosporins, Vancomycin etc.. Cephalosporin generations are usually used as prophylaxis for postop patients, but they can't kill MRSA. The new line of treatment for MRSA includes: Trimethoprim, Linezolid, Chloramphenicol, Clindamycin, Rifampin etc..Extensive handwashing is also recommended.
3) Normal flora are nonpathogenic until they remain in their original site, or the host has a strong immune system. But if the immune system weakens, or the normal flora exchange genes via conjugation with pathogenic strains after heavy antibiotic usage, they become opportunistic pathogens.
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