Research Paper on Categories of Antimicrobial Agents

Introduction

There are four categories of antimicrobial agents based on the microorganisms they inhibit. They are antibacterial, antifungal, antiparasitic, and antiviral agents. Antibacterial agents are the ones that are most commonly used among the four agents (Becker, 2013). The different classes of antimicrobials will only act on a specific type of microorganisms. These drugs are used for both treatment and prevention.

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Antibacterial agents inhibit the growth or kill bacteria. Within the class of antibacterial agents, there are several other classes of drugs that have different spectra of activity. Commonly used antibacterial drugs include beta-lactam antibiotics, tetracycline, and rifampicin (Becker, 2013).

Antifungal agents have limited variety due to the high similarity between the fungal cell and the mammalian cell. The most commonly used antifungal agents are azole derivatives which are usually indicated for Candida infections (Becker, 2013).

Antiviral agents are used to treating infections caused by viruses. Most of these agents act by arresting the replication of viruses thereby minimizing the spread and reducing symptoms (Becker, 2013). Most common viral infections such as common cold are usually self-limiting in immuno-competent individuals.

Anti-parasitic agents usually eliminate parasites from the body. Such parasites include helminths such as tapeworms. Anti-parasitic agents typically have a broad spectrum of activity; they can reduce a wide range of parasites (Becker, 2013). An example of a common anti-parasitic agent is albendazole which is used against a wide range of helminths.

Differences between Viral and Bacterial Infections

The primary difference between bacterial and viral infections is the causative organism in these infections. Bacteria results in antibacterial infections whereas viruses cause viral infections. A significant difference between the two types of infections is that bacterial infections are susceptible to antibiotics whereas viral infections are not (Nuutila & Lilius, 2007). The mechanism of replication of bacteria and viruses differ. In viral infections, viruses use the cell machinery to replicate while bacteria replicate via other means such as budding (Sweeney et al., 2017). These differences result in a difference in the manifestations of viral and bacterial infections.

Bacterial infections can either be endogenous or exogenous whereas viral infections are all exogenous (Nuutila & Lilius, 2007). The reason is that some bacteria are present in various parts of the human body as normal flora which may cause endogenous infections. However, viruses are not present anywhere in the human body under normal conditions. The bacteria which are present in the body as normal flora may invade the body and cause infection due to a change in conditions. For instance, Clostridium difficile which is usually present in the colon as normal flora usually causes an infection following prolonged therapy with some antibiotics that eliminates other microorganisms causing it to multiply in the colon. Since viruses are generally absent in the body, all viral infections usually result from the introduction of a virus into the body from an external source.

The Significance of Proper Identification of Viral and Bacterial Infections in the Selection of Proper Antimicrobial Agent

Antimicrobial agents are among the most commonly injudiciously used medicines (Leekha et al., 2011). The most significant consideration in the prescription of antimicrobial therapy is reaching a proper diagnosis. The diagnosis made can either be empirical or definitive. Definitive diagnosis is usually not available at all times. For this reason, empirical diagnosis is usually used to prescribe antimicrobial therapy while awaiting laboratory results (Leekha et al., 2011). In the case of viral and bacterial infections, a proper diagnosis is usually vital for positive outcomes. For instance, if a patient presents with meningitis, determination of the cause of the infection is crucial to avoid a fatality. Administration of the wrong antimicrobial could result in the death of a patient in such medical emergencies since antibacterial will not combat a viral infection and vice versa.

Correct identification of bacterial or viral infections is the mainstay of therapeutic success (Sherris & Ryan, 1984). Antiviral agents do not work on bacteria, and antibacterial agents do not work on viruses. Identification of the causative organism in infection will make it possible for healthcare providers to make the correct decision regarding the type of antimicrobial agent that should be prescribed (Sherris & Ryan, 1984). In the case of bacterial infections, some bacteria strains have been found to be resistant to certain antibiotics implying strain identification is essential for an effective antimicrobial to be selected. An example is Methicillin-Resistant Staphylococcus aureus (MRSA) which is not susceptible to methicillin and other penicillins. In some cases, it may not be apparent whether the causative organism is a virus or bacteria. Additionally, different types of bacteria can cause an infection with similar symptoms such as pneumonia. Determining the specific causative organism will enable proper selection of antimicrobial agents. Identification of bacterial and viral infections will also enable more narrow and cost-effective therapeutic interventions to be made. Identification of causative organism in bacterial and viral infections saves cost since the administration of several classes of antimicrobials can be avoided. Thereby, the determination of the causative agent in the case of bacterial and viral infections is central to the selection of the most appropriate antimicrobial agent.

References

Becker, D. E. (2013). Antimicrobial Drugs. Anesthesia Progress, 60(3), 111-123. doi:10.2344/0003-3006-60.3.111

Leekha, S., Terrell, C. L., & Edson, R. S. (2011). General Principles of Antimicrobial Therapy. Mayo Clinic Proceedings, 86(2), 156-167. doi:10.4065/mcp.2010.0639

Nuutila, J., & Lilius, E. (2007). Distinction between bacterial and viral infections. Current Opinion in Infectious Diseases, 20(3), 304-310. doi:10.1097/qco.0b013e3280964db4

Sherris, J. C., & Ryan, K. J. (1984). Chapter 10: Principles of Diagnosis. In Medical Microbiology: An Introduction to Infectious Diseases. Elsevier Publishing Company.

Sweeney, T. E., Wong, H. R., & Khatri, P. (2016). Robust classification of bacterial and viral infections via integrated host gene expression diagnostics. Science Translational Medicine, 8(346), 346ra91-346ra91. doi:10.1126/scitranslmed.aaf7165