Community-Acquired Pneumonia:Causative Agents and Transmission

Introduction

The infection given in the scenario is Community-Acquired Pneumonia (CAP). The condition can be caused by various microorganisms such as Haemophilus influenza, Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella, Gram-negative bacilli, Staphylococcus aureus2. However, the major cause is the Streptococcus pneumoniae . The infection is transmitted when the microorganisms that cause it reach the lungs through inhalation of droplets that are created by sneezing or coughing from an individual who is infected2. The causative agent is responsible for more than 50% of all the cases that have been reported but can also be caused by respiratory viruses (mostly influenza type A) and the atypical bacteria Chlamydophila pneumoniae and Mycoplasma pneumoniae2.

Interpretation of the microbiological data

From the data provided, gram-negative rods are notable. Besides, the cetrimide media indicated a green colour due to the combination of blue-water-soluble pyocyanin indicating a characteristic of Pseudomonas aeruginosa. In this case, I excluded other microorganism based on the idea that cetrimide is a selective agent that inhibits most bacteria through the action as a detergent and Pseudomonas aeruginosa releases various water-soluble iron chelators that indicate a yellow-green fluorescent pyoverdin, which combines with the blue water-soluble pyocyanin thus producing the green colour that was observed. Besides, the oxidative test was also positive thus supporting the indication from the first test. MacConkey agar was noted to be pale and this was associated with the fact that the microorganism that was suspected was lactose negative. The microorganism also grows well in LB broth besides having the ability to use various compounds such as carbon and nitrogen.

Antibiotic sensitivity

The first line of treatment that I would suggest for the condition would be doxycycline. This medication has been noted to have a very high degree of activity against many respiratory pathogens such as Pseudomonas aeruginosa. It is thus an effective and inexpensive therapy for the empirical treatment of patients with severe community acquired pneumonia. For CAP, I would prescribe 100mg PO every 12 hours for 5 to 10 days for the patient if it is an adult. For a child that is 8 years and older and adolescents that weigh below 45Kg, I would prescribe 2mg/kg/dose every 12 hours for 5 to 10 days for CAP3. This is an oral dosage thus the route of administration is the oral route.

Mode of action

The medication exerts antimicrobial effects by inhibiting protein synthesis1. The target of the drug is the interaction that important for the translation initiation of protein that takes place at the 3′ end of the 16S rRNA, found on the ribosome on the 30S subunit. The drug thus inhibits the translation through the binding to the 16S rRNA part of the ribosome1. This prevents the binding of the tRNA to the RNA-30S bacterial ribosomal subunit that is essential to the delivery of amino acids for protein synthesis1. The actions result in blockade of the initiation of protein synthesis by polyribosome formation. The replication of the bacteria is thus stopped and a bacteriostatic effect if produced1.

References

• Chukwudi, C. U., & Good, L. (2019). Doxycycline inhibits pre-rRNA processing and mature rRNA formation in E. coli. The Journal of antibiotics, 72(4), 225-236.
• Mandell, L. A. (2004). Epidemiology and etiology of community-acquired pneumonia. Infectious Disease Clinics, 18(4), 761-776.
• Saivin, S., & Houin, G. (1988). Clinical pharmacokinetics of doxycycline and minocycline. Clinical pharmacokinetics, 15(6), 355-366.

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