Wound infections in burn victimsAfter a horrible fire ravaged a bloc of flats, several residents were brought to the hospital for mild to severe burn treatments (see Table 1).Table 1: Patients admitted at the hospital following the fire.NameAge (years)Medical conditionSandra63Second-degree burns on 40% of her bodyMarco19Deep third-degree burns on 90% of his legsAlexandre29Deep third-degree burns on 35% of his legsMatthieu58Superficial burns on his arms and legsMaddie38Partial thickness burns on her left armMatthieu and Maddie, who were less severely burned, were treated with various topical anesthetic ointments and antibiotics, they were released from care and made full recoveries.Severely burned Sandra, Marco, and Alexandre were all moved to an isolated section of the ICU and initially treated through intravenous (for fluid resuscitation) and intra-arterial (for invasive blood pressure monitoring) catheters.After being treated for shock and after their conditions were stabilized, Sandra, Marco, and Alexandre were treated in the hydrotherapy room (warm running water) twice daily for 2-3 days. Hydrotherapy can stimulate recovery and act as a pain relief for burn victims. However, the patients soon started exhibiting signs of infection with high fevers/malaise, and their wounds started emitting sweet-like odors.Dr. Moochin, the physician in charge of Sandra, Marco and Alexandre, was very worried about the symptoms her patients were exhibiting. She suspected bacterial infections and without waiting for diagnostic results, she immediately prescribed antibiotics for all 3 patients.During the twice daily dressing changes, wound exudates (fluid that leaks out from the lymph and blood into injured tissues) were collected from each patient using a sterile collection system, and bacterial culture tests were performed to confirm the presence of bacterial infection.After gram staining, microscopy examination showed that the isolates from all patients in the ICU were dominated by blue/purple coccoid cells, indicating a Staph infection. However, Marco’s wounds were colonized by both red/pink rods and blue/purple coccoid cells. The rods were identified as Pseudomonas aeruginosa, and the cocci were Staphylococcus aureus.To make sure the antibiotics she had prescribed would treat the bacterial infections, Dr. Moochin asked for an antibiotic sensitivity test, which all came back positive. When the patient’s general conditions did not respond after days of high-dosage antibiotic treatment, Dr. Moochin consulted with her colleagues about what to do next. Dr. Moochin and her colleagues suspect that the bacteria causing the infection in her patients are resistant to the antibiotics, but not because of genetic resistance. She decided to ask the clinical microbiology lab to determine the biochemical profile of the bacteria causing infections in her patients, in an effort to understand the nature of the persisting infections.Several tests were made on the samples collected from patients’ wound. Dr Moochin was aware of the various other ways bacteria can transiently survive antibiotic treatments and wanted to know which mechanism was at cause. Knowing the cause could help her treat her patient in the best possible way.To do so, she ordered the following molecules to be measured in each sample:c-di-guanylate monophosphate (c-di-GMP)Polyphosphate (poly-P)Exopolysaccharides (EPS)Autoinducers (AI)Guanidine tetraphosphate (ppGpp)A) Why would Dr Moochin ask to measure each of these molecules in the patient’s sample? Explain the reason for measuring each of them. The lab came back with the following results for the following patients:Marco c-di-GMPPoly-PEPSAI(p)ppGppControl++-+-S.aureus+++++++++++P.aeruginosa++++++++++++Alexandre c-di-GMPPoly-PEPSAI(p)ppGppControl++-+-S.aureus++++++++++++P.aeruginosan/an/an/an/an/ab) Which patient’s wound are most likely covered in a biofilm of aureus? Explain why you chose this patient. Dr Moochin is aware that P.aeruginosa possesses a TA system which promotes virulence and help the bacterial population to resist antibiotic treatment. The P.aeruginosa Toxin/Antitoxin (TA) system leads to the activation of an RNAse (a different system then the HipAB system seen in class). The end results are similar tough, when activated, this P.aeruginosa TA system leads to cell dormancy. C) Thinking about what you know of the mechanisms that lead to cell dormancy and persistence, how could the activation of an RNAse by the aeruginosa TA system have a similar effect then that of the HipAB system seen in class? Explain your reasoning. D) Another aeruginosa TA system leads to the decrease in cellular NAD+. How could this promote cell dormancy? Using all knowledge acquired in class that may be relevant, explain how low levels of NAD+ could lead to cell dormancy.

Question

Wound infections in burn victimsAfter a horrible fire ravaged a bloc of flats, several residents were brought to the hospital for mild to severe burn treatments (see Table 1).Table 1: Patients admitted at the hospital following the fire.NameAge (years)Medical conditionSandra63Second-degree burns on 40% of her bodyMarco19Deep third-degree burns on 90% of his legsAlexandre29Deep third-degree burns on 35% of his legsMatthieu58Superficial burns on his arms and legsMaddie38Partial thickness burns on her left armMatthieu and Maddie, who were less severely burned, were treated with various topical anesthetic ointments and antibiotics, they were released from care and made full recoveries.Severely burned Sandra, Marco, and Alexandre were all moved to an isolated section of the ICU and initially treated through intravenous (for fluid resuscitation) and intra-arterial (for invasive blood pressure monitoring) catheters.After being treated for shock and after their conditions were stabilized, Sandra, Marco, and Alexandre were treated in the hydrotherapy room (warm running water) twice daily for 2-3 days. Hydrotherapy can stimulate recovery and act as a pain relief for burn victims. However, the patients soon started exhibiting signs of infection with high fevers/malaise, and their wounds started emitting sweet-like odors.Dr. Moochin, the physician in charge of Sandra, Marco and Alexandre, was very worried about the symptoms her patients were exhibiting. She suspected bacterial infections and without waiting for diagnostic results, she immediately prescribed antibiotics for all 3 patients.During the twice daily dressing changes, wound exudates (fluid that leaks out from the lymph and blood into injured tissues) were collected from each patient using a sterile collection system, and bacterial culture tests were performed to confirm the presence of bacterial infection.After gram staining, microscopy examination showed that the isolates from all patients in the ICU were dominated by blue/purple coccoid cells, indicating a Staph infection. However, Marco’s wounds were colonized by both red/pink rods and blue/purple coccoid cells. The rods were identified as Pseudomonas aeruginosa, and the cocci were Staphylococcus aureus.To make sure the antibiotics she had prescribed would treat the bacterial infections, Dr. Moochin asked for an antibiotic sensitivity test, which all came back positive. When the patient’s general conditions did not respond after days of high-dosage antibiotic treatment, Dr. Moochin consulted with her colleagues about what to do next. Dr.  Moochin and her colleagues suspect that the bacteria causing the infection in her patients are resistant to the antibiotics, but not because of genetic resistance. She decided to ask the clinical microbiology lab to determine the biochemical profile of the bacteria causing infections in her patients, in an effort to understand the nature of the persisting infections.Several tests were made on the samples collected from patients’ wound. Dr Moochin was aware of the various other ways bacteria can transiently survive antibiotic treatments and wanted to know which mechanism was at cause. Knowing the cause could help her treat her patient in the best possible way.To do so, she ordered the following molecules to be measured in each sample:c-di-guanylate monophosphate (c-di-GMP)Polyphosphate (poly-P)Exopolysaccharides (EPS)Autoinducers (AI)Guanidine tetraphosphate (ppGpp)A) Why would Dr Moochin ask to measure each of these molecules in the patient’s sample? Explain the reason for measuring each of them. The lab came back with the following results for the following patients:Marco c-di-GMPPoly-PEPSAI(p)ppGppControl++-+-S.aureus+++++++++++P.aeruginosa++++++++++++Alexandre c-di-GMPPoly-PEPSAI(p)ppGppControl++-+-S.aureus++++++++++++P.aeruginosan/an/an/an/an/ab) Which patient’s wound are most likely covered in a biofilm of aureus? Explain why you chose this patient. Dr Moochin is aware that P.aeruginosa possesses a TA system which promotes virulence and help the bacterial population to resist antibiotic treatment. The P.aeruginosa Toxin/Antitoxin (TA) system leads to the activation of an RNAse (a different system then the HipAB system seen in class). The end results are similar tough, when activated, this P.aeruginosa TA system leads to cell dormancy. C) Thinking about what you know of the mechanisms that lead to cell dormancy and persistence, how could the activation of an RNAse by the aeruginosa TA system have a similar effect then that of the HipAB system seen in class? Explain your reasoning. D) Another aeruginosa TA system leads to the decrease in cellular NAD+. How could this promote cell dormancy? Using all knowledge acquired in class that may be relevant, explain how low levels of NAD+ could lead to cell dormancy.

Accepted Answer

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Name	Age (years)	Medical condition
Sandra	63	Second-degree burns on 40% of her body
Marco	19	Deep third-degree burns on 90% of his legs
Alexandre	29	Deep third-degree burns on 35% of his legs
Matthieu	58	Superficial burns on his arms and legs
Maddie	38	Partial thickness burns on her left arm

	c-di-GMP	Poly-P	EPS	AI	(p)ppGpp
Control	+	+	-	+	-
S.aureus	+++	+	++++	++	+
P.aeruginosa	++	+++	++	++	+++