Question

The results of your patient’s wound culture just arrived, and Gram staining revealed the presence of pink, rod-shaped bacterial cells organized in pairs. You quickly realize that this patient could be at risk for developing fever and shock. Explain how the culture results indicated this potential risk.

Answer 1

Answer, discussion and explanation :

Bacteria which are rounded in shape are termed as cocci and bacteria which are rod shaped are termed as bacilli.

After Gram staining if bacteria appears violet or purple on microscopic examination, the bacteria is termed as Gram positive because it retains crystal violet used in staining imparting it the violet or purple appearence. These bacteria have thick cell wall mainly composed of peptidoglycan. These bacteria have chemicals which are released in circulation and are termed as exotoxin.

Bacteria which appear pink after staining are termed as Gram negative because they are unable to retain crystal violet due to thin cell wall. Gram negative bacteria have three layered covering- inner cell membrane, middle thin cell wall layer and outer membrane which contains lipopolysaccharide in large amount. This lipopolysaccharide acts as endotoxin and triggers exaggerated immune response leading to activation of large number of macrophage like immune cells and thus in turn widespread release of different cytokines. Cytokines are chemicals which act on different targets and give rise to many manifestations such as fever (Interleukins and TNF), dilatation of blood vessels (nitric oxide) and suppress heart activity (TNF-alpha and Interleukin-6).Vasodilation and suppression of cardiac contractility can lead to fall in blood pressure.

Endotoxins of Gram negative bacteria are more powerful in triggering an exaggerated immune response than exotoxins of Gram positive bacteria.

* Systemic inflammatory response syndrome (SIRS) is defined as any two of the following four criteria :

A) Body temperature > 38°C or < 36°C

B) Heart rate > 90 beats /minute

C) Respiratory rate > 20/minute

D) Total leukocyte count > 12000/mm3 or < 4000/mm3 or >10% immature cells

* Sepsis is defined as systemic inflammatory response syndrome due to infection

* Septic shock is defined as sepsis induced hypotension

Hence we can conclude that the bacteria isolated is Gram negative bacilli in pairs which can trigger a severe systemic inflammatory response syndrome or septic shock which is characterized by fever and low blood pressure.