Approach to nosocomial infections: Clinical sciences

Nosocomial infections, also called healthcare-associated infections, or HAIs for short, are infections that patients acquire while receiving medical care for another condition. Anyone who is hospitalized, lives in long-term care, or receives care at an outpatient facility, such as a dialysis unit or rehabilitation center, can develop a nosocomial infection.

Nosocomial infections are most commonly caused by multidrug-resistant bacteria, such as Methicillin-Resistant Staphylococcus Aureus or MRSA, Vancomycin-Resistant Enterococcus or VRE, and Carbapenem-Resistant Enterobacteriaceae or CRE. Less common causes include viruses and fungi.

The most common nosocomial infections include catheter-associated urinary tract infections or CAUTI; central line-associated bloodstream infections or CLABSI; surgical site infections or SSI; hospital-acquired pneumonia or HAP; ventilator-associated pneumonia or VAP; and Clostridioides Difficile infection or CDI.

If your patient presents with signs and symptoms suggestive of nosocomial infection, you should first perform an ABCDE assessment to determine if the patient is unstable or stable. If the patient is unstable, first stabilize the airway, breathing, and circulation, and start broad-spectrum antibiotics, before continuing with further workup.

Now, let’s go back to the ABCDE assessment and take a look at stable patients. In this case, obtain a focused history and physical examination, and order labs including a complete blood count with a differential. History typically reveals current or recent treatment at an inpatient or outpatient healthcare facility, as well as systemic symptoms of infection, such as fever, chills, and fatigue.

On exam, the patient might present with altered mental status, like confusion or lethargy, but also localized findings depending on the type of infection. Additionally, labs typically show leukocytosis. Alright, now if these features are present, you should suspect nosocomial infection and assess the source of infection.

Now, here's a clinical pearl! Keep in mind that some populations, such as elderly or immunosuppressed patients, may not develop fever and leukocytosis in response to infection. These patients may only present with vague symptoms, like fatigue or changes in mental status.

You can start by assessing indwelling devices like urinary catheters and central lines. First, let’s start with catheter-associated urinary tract infection, or CAUTI. These patients typically have a urinary catheter in place, or one was removed within the past two days. Symptoms usually include suprapubic discomfort, dysuria, as well as urinary frequency and urgency; while physical exam often reveals suprapubic or costovertebral angle tenderness. In this case, consider catheter-associated urinary tract infection, or CAUTI, so don’t forget to change the urinary catheter and then order a urinalysis and urine culture to avoid getting a contaminated or colonized sample. If the urinalysis reveals pyuria and bacteriuria, and the urine culture is positive, then the patient has CAUTI.

Next up is central line-associated bloodstream infection or CLABSI. This is associated with either a central line that’s been in place for more than 2 days, or symptoms of infection that developed on the day of central line removal or the next day. In addition to systemic signs, there are also localized signs of infection at the central line insertion site, like erythema, tenderness, and purulence.

In this case, you should consider CLABSI, so don’t forget to send two or more samples for blood cultures taken from different sites, like a peripheral vein and the central line. One positive blood culture for bacteria that is a true pathogen, meaning for bacteria that are not a part of human microflora; or two positive blood cultures for bacteria that are commensal organisms from the normal microflora, are highly suggestive of CLABSI.

Here’s a high yield fact! Staphylococcus epidermidis is a coagulase-negative baterium that’s part of the normal skin flora, but it’s among the most common causes of nosocomial blood infections, especially in patients with prosthetic valves, cardiac devices, central lines, catheters, and IV drug use. That’s because coagulase-negative species are able to produce an adherent biofilm that allows them to survive and colonize these devices.