Question

CLINICAL CASE #1

USE THE FOLLOWING INFORMATION TO ANSWER THE QUESTION

It was a hot summer day in Fort Meyers, Florida, and Max was anxious to get some last-minute surfing in before the end of the weekend. A slip of the knife while prepping dinner had him nursing a minor hand wound that kept him out of the water for the past week. The wound was not very deep and was healing well—it was well scabbed over and was itchy but painless. After enjoying a full morning back in the surf, Max was famished and stopped at a local burger stand for lunch. While devouring greasy fries and a burger, he noticed that his lengthy time in the water had softened the scab on his hand to no more than a small pinkish layer. The wound looked much better than it had in days.

However, by 5:00 p.m. that evening, Max felt achy and his upper arm and hand were sore. He noticed the area that was previously covered by the small pink remnants of a scab had reddened and become tender, swollen, and warm to the touch. He figured the soreness was normal after a day in the surf, and that the hand abrasion was just irritated from sea and sand. He also felt a bit nauseous, but assumed that might be due to the greasy food he had eaten for lunch. Exhausted, feverish, and nauseous, Max skipped dinner and went to bed early.

His mom called him around 8:30 p.m. She noticed that he sounded terrible. Upon learning of his symptoms, she told him to go to the emergency room right away. Since his mom was a nurse, he decided he’d better listen to her even though he thought she was probably overreacting.

Max was 33. Aside from this acute situation, he was in perfect health. Despite this, the doctor was concerned about his condition, especially since he was running a fever. The emergency department staff admitted Max to the hospital for wound management, intravenous antibiotic therapy, and monitoring. By the morning, Max had a heartbeat of 105 beats per minute (tachycardia), a temperature of 101.4°F (38.4°C), remained nauseous, and was also disoriented. Despite ongoing intravenous volume resuscitation (IV fluid administration), Max was hypotensive (had a pathologically low blood pressure). In addition, his arm was looking much worse: It was severely swollen, and pulses in the arm were difficult to detect. The skin, which had previously been mostly spared, now appeared eccyhmotic (took on a deep bluish color due to the escape of blood from ruptured blood vessels into the surrounding tissue) and a number of hemorrhagic bullae (large blood-filled blisters) were evident. Max was also in excruciating pain that morphine barely dulled.

The attending physician suspected Max had necrotizing fasciitis (informally known as “flesh-eating bacteria”), a soft tissue infection that is usually caused by Gram-positive group A streptococci. He noticed Max had some mild sunburn, and asked him if he’d been out swimming lately. Max confirmed he’d been surfing the morning before falling ill. The microbiology report confirmed the physician’s suspicions: Max was fighting off a Gram-negative bacterium called Vibrio vulnificus. Knowing that V. vulnificus has a number of virulence factors (a capsule, extracellular collagenases, proteases and lipases, motility, and various other adhesins and invasins like siderophores and toxins that act as cytolysins and hemolysins), the doctor was worried about Max’s rapid decline.

Max was immediately taken into surgery for wound debridement–– the removal of infected, damaged tissue. Following surgery, Max was moved to the intensive care unit (ICU). He endured several additional wound debridement procedures and a skin graft. Max was told that his age and general overall health would likely lead him to a full recovery. The nurse explained to Max that had his fever and hypotension not resolved after the debridement procedures, the doctor likely would have recommended an amputation. Fortunately, that was not the case. Although Max’s arm would require a good deal of rehabilitation, he would eventually regain full use of the affected arm.

QUESTION #1

Which of the following virulence factors contributed to the pathology described in the case?

SELECT ALL THAT APPLY

Collagenase helped the pathogen breakdown tissues in the patient’s arm to promote invasion.

A capsule helped the pathogen avoid phagocytosis by leukocytes, allowing the pathogen time to replicate.

Mycolic acids in the bacterial cell wall enabled the pathogen to resist initial intravenous antibiotic therapy, allowing the disease to progress.

Endospores helped the pathogen resist initial intravenous antibiotic therapy, allowing the disease to progress.

Flagella enabled the pathogen to move deeper into the patient’s tissues to establish infection.

Membrane-damaging toxins interfered with host immune function, allowing the pathogen time to replicate.

Answer 1

Ans. -Collagenase helped the pathogen breakdown tissues in the patient's arm to promote invasion.

-A capsule helped the pathogen avoid phagocytosis by leukocytes, allowing the pathogen time to replicate.

-Flagella enabled the pathogen to move deeper into the patient's tissues to establish infection.

-Membrane-damaging toxins interfered with host immune function, allowing the pathogen time to replicate.

Explanation: Collagen is protein found in many tisssues in humans and it is degraded by collagenase enzyme produced by the pathogen making the invasion by pathogen easier. Capsule is the structure surrounding the pathogenic bacteia and it does not allow the engulfing by immune cells like leucocytes which phagocytose the pathogens. Phagocytosis is the ingulfing of pathogens by immune cells to destroy the pathogens. Movement from outer region to interior of the tissue with the help of flagella enables the pathogen to progress the infection. Toxins produced by the pathogen damage the membrane and interfer with host immune response. This allows pathogen to grow in the host tissue progressing the tissue infection.