Inside the Mind of an Infectious Disease Specialist

Armelle Pérez-Cortés Villalobos, MD, MSc

October 01, 2021

An infectious disease specialist often acts as a detective, exhaustively searching for clues to reconstruct and understand a patient's condition. This perspective is not unique to infectious disease specialists, but the mindset is particularly important when approaching a patient with a suspected infectious disease.

The first question we ask ourselves is whether or not the patient is hemodynamically stable. If the patient is unstable, we have a responsibility to quickly decide on a short-term plan, especially because the instability could be secondary to an infection. As such, the priority is to collect cultures before we can decide, on an empirical basis, whether to start antibiotic treatment.

The administration of broad-spectrum antibiotics in an unstable patient is a reasonable and life-saving measure. But it is not acceptable to continue them if the presence of an infectious agent is ruled out, and if an agent is identified, the broad-spectrum regimen should be switched to the most appropriate antibiotic.

The key lies in carefully listening to what the patient says and identifying the relevant data.

The next step is to find the source of infection; in the vast majority of cases, it can be identified with structured and detailed questioning. The key lies in carefully listening to what the patient says and identifying the relevant data. It is important to ask whether the patient was feeling well before the onset of symptoms and to allow the patient's description of the development of the condition to be understood in chronological order. Likewise, factors that can alter the clinical course of a disease must be considered. As William Osler, MD, one of the founding professors of Johns Hopkins Hospital, used to say, "The good physician treats the disease; the great physician treats the patient who has the disease."

The approach to infectious diseases follows this advice. As we know, a urinary tract infection is different in a 70-year-old man, a pregnant woman, and a kidney-transplant patient. An infection can have a variety of clinical presentations in different groups of patients, so we must be able to identify it. Each presentation will have a different clinical course and require different management.

It is rare for infectious disease specialists to be the first physicians to see a patient. In general, other colleagues consult us, and it is common that the patients we see have an extensive medical history, are on antibiotics, and that alternatives to resolve the condition have been tried before we were become part of the management team. In these cases, our detective work involves reconstructing the sequence of the patient's clinical course. The beauty lies in the details. For example, it is often important to look at the days when the patient had a fever, the antibiotics they were taking when they developed a fever, if they received antipyretics at the time the fever abated, or if they started enteral nutrition on the day they had diarrhea. All these details, based on common sense and the clinical course of the patient, give us the clues we can use to make decisions to successfully manage the patient.

As an infectious disease specialist, I cannot emphasize enough the importance of taking cultures from patients in a timely manner. There is no magic bullet without cultures. Timely cultures allow us to "first, do no harm" by ruling out diagnostic possibilities, and have a direct impact on the duration and spectrum of antibiotics the patient ultimately receives. Some infectious conditions require several weeks of antibiotics, such as endocarditis or osteomyelitis. Broad-spectrum antibiotics can be unsustainable for patients with these infections, but cultures can identify the infectious agent and point to a simplified regimen.

A positive culture is not the same as having an infection.

A positive culture is not the same as having an infection. One of the most frequent tasks of the infectious disease specialist is to evaluate the relevance, congruency, and impact of a bacterial or fungal culture on the patient. When we have a positive culture, we think about the relevance of the isolated pathogen. With knowledge, common sense, and experience, we assess its pathogenic role in the body. This, combined with the symptoms and clinical state of the patient, will help us achieve one of our major tasks: to avoid giving antibiotics for positive cultures. We need to treat infections.

As with all medical practice, the infectious disease specialist's job is to act for the benefit of the patient, which means engaging in antibiotic stewardship. The objective is to assess the infectious disease and the patient's characteristics to provide the treatment needed to resolve the patient's condition.

This commentary originally appeared in the Spanish edition of Medscape.

Follow Armelle Pérez-Cortés Villalobos of Medscape in Spanish on Twitter @armelleID.

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