Introduction
(Article introduction authored by ICU Editorial Team)
Bacterial and fungal infections are prevalent among intensive care unit (ICU) patients, with up to 50% diagnosed at any given time. These infections pose challenges due to drug-resistant organisms.
Mortality rates in ICU patients with infections are approximately 30%, and drug-resistant infections further increase the odds of death.
Antimicrobial resistance (AMR) is a global concern, affecting Gram-negative and Gram-positive organisms.
Fungal infections, including multidrug-resistant Candida auris, present emerging threats. ICU admission increases the risk of nosocomial infections, and recent experiences during the COVID-19 pandemic have underscored these challenges, leading to outbreaks of multidrug-resistant bacterial infections.
This review explores the epidemiology, risk factors, diagnosis, management, and prevention strategies for bacterial and fungal infections in the ICU, addressing the impact of AMR and recent challenges observed during pandemics.
Challenges in the Diagnosis of Bacterial and Fungal Infection in ICU
Diagnosing infections in ICU patients poses challenges, as organ support may obscure traditional diagnostic factors like the systemic inflammatory response syndrome (SIRS), often of non-infective origin.
Clinical history and examination limitations, coupled with diagnostic delays, underscore the urgency in therapeutic decision-making.
Despite prediction tools, early recognition based on clinical judgment is crucial, emphasizing the need for prompt investigation and management when sepsis is suspected
While early appropriate antimicrobial therapy benefits severe infections, undue broad therapy is linked to increased mortality and complications.
Controversies persist regarding time-to-antibiotic guidelines without prior diagnostic steps.
Timely investigation and therapy initiation, considering clinical risk factors and available diagnostics, are essential for optimal care.
Advances in Diagnostics
For over a century, microbiological diagnostics have primarily relied on culture-based methods for identifying and characterizing microorganisms.
These approaches offer a phenotypic antimicrobial susceptibility profile, facilitating targeted prescription based on the organism, drug pharmacokinetics/pharmacodynamics, and host factors.
However, traditional culture-based methods suffer from slow turnaround times, limited sensitivity, and variations between laboratories. Consequently, the identity and antimicrobial susceptibility report for an organism may not be available until 48–72 hours after sample collection, leading to delays in delivering targeted and individualized therapy and creating a window for inappropriate broad treatment.
Recent technological advances in microbiology aim to streamline the identification and susceptibility reporting of microorganisms in the intensive care unit (ICU).
This includes improving sample collection and delivery, developing rapid antimicrobial susceptibility methods, and adopting innovative technologies for organism identification and antimicrobial resistance.
Matrix-assisted laser Desorption/Ionization – Time of Flight Mass Spectrometry (MALDI-TOF MS) exemplifies a technology that expedites organism identification and detects antimicrobial resistance.
Molecular diagnostic tools offer an additional modality by bypassing the culture step, allowing rapid organism detection and identification directly from clinical specimens.
Near-patient testing with molecular platforms in the ICU can potentially reduce the time to organism identification and targeted antimicrobial therapy.
Despite improvements in antimicrobial stewardship targets, such as reduced time to effective therapy, current trials have yet to demonstrate significant enhancements in clinical outcomes, including mortality.
Management of Bacterial and Fungal Infection in the ICU
Empiric Antimicrobial Therapy
Empirical antimicrobial selection in the intensive care unit (ICU) is crucial to cover potential causative organisms while awaiting definitive results for targeted treatment.
The challenge in the ICU lies in the higher prevalence of drug-resistant infections, necessitating broad-spectrum antimicrobials with anti-pseudomonal properties.
In regions with elevated methicillin-resistant Staphylococcus aureus (MRSA) prevalence, glycopeptides are often included empirically.
For suspected fungal infections, echinocandins are recommended for suspected candidaemia, and amphotericin-B is used empirically for invasive mould infections.
Diagnosis involves considering various factors, and syndromic approaches guide empirical treatment based on common causative organisms and local resistance patterns.
Optimizing drug delivery, especially in critically ill patients, is vital due to pharmacokinetic/pharmacodynamic variations associated with increased mortality risk in sepsis.
Prolonged or continuous infusion of beta-lactam and glycopeptide antibiotics is often recommended to ensure optimized targeted attainment.
Targeted/Individualised Antimicrobial Therapy
SIn septic shock, prompt administration of antimicrobial therapy within an hour of recognition is crucial to reduce mortality, while guidelines support initiation within 3 hours for patients without shock.
Challenges in critically ill patients often limit waiting for culture-based diagnostic results, but point-of-care molecular diagnostics show promise for quicker targeted therapy.
Once culture-based diagnostics yield organism and susceptibility results, transitioning from broad-spectrum empiric therapy to targeted treatment can minimize adverse events and combat antimicrobial resistance.
Despite limited randomized control trial data, observational studies support the safety of early de-escalation, indicating no impact on mortality.
Therapeutic drug monitoring (TDM) gains recognition for ensuring optimal drug exposure in critically ill patients, particularly for beta-lactam antibiotics, vancomycin, and linezolid, with ongoing research to determine its overall impact on patient outcomes.
The Importance of Source Control and Other Non-Antimicrobial Factors
Effective infection management in the ICU goes beyond antimicrobial selection, emphasizing the importance of source control.
This involves removing persistent sources of infection, preventing ongoing contamination, and restoring pre-morbid function and anatomy whenever possible.
Source control encompasses draining collections or abscesses, debriding or removing infected devices, and implementing definitive control measures.
Guidelines advocate prompt source control performance, ensuring optimal individual patient outcomes. In the ICU, source control often involves minimizing unnecessary invasive interventions.
Although routine central venous catheter replacement lacks evidence for reducing infection risk and is not recommended, regular review and removal when unnecessary or suspicion of infection are crucial.
In suspected infections, catheters should be re-placed at new sites, avoiding re-wiring the old line. Strategies such as daily sedation holds and spontaneous breathing trials are suggested to potentially reduce the need for mechanical ventilation, though consistent benefits in reducing ventilation duration are not firmly established.
Infection Prevention in the ICU
In the ICU, infection prevention involves a comprehensive, multi-modal strategy addressing hand hygiene, environmental cleanliness, screening, isolation practices, surveillance, antimicrobial stewardship, and adherence to patient safety guidelines.
Hand hygiene, particularly with alcohol-based gels and soap and water, is pivotal in reducing nosocomial pathogen transmission.
The breakdown in hand hygiene during the COVID-19 pandemic led to outbreaks of organisms like Corynebacterium striatum.
Transmission-based precautions may vary in effectiveness; hand hygiene adherence plays a crucial role, especially in reducing drug-resistant organism transmission.
Surveillance at local, regional, and national levels aids in identifying outbreaks and shaping antimicrobial policy.
Selective Decontamination of the Digestive Tract (SDD) is proposed to reduce ventilator-associated pneumonia risk; while it may not lower mortality, it reduces bacteraemia rates and drug-resistant infections.
In hospitals, IPC policy, including care bundles, aims for safe, effective patient care. Care bundles, like the “Matching Michigan” and ‘100K lives campaign’, have successfully lowered infection rates, and the Surviving Sepsis Campaign has reduced mortality in septic patients.
Conclusion
Bacterial and fungal infections in ICU patients are significant events, necessitating consideration from all involved in critical care.
Preventable through adherence to multi-modal infection prevention and control (IPC) policies, these infections are crucial considerations in patient care.
Diagnosis complexity evolves with additional information over time, and the introduction of molecular diagnostics and rapid antimicrobial susceptibility testing (AST) offers earlier insights into organism characteristics. To maximize patient benefit, these technological advancements should be integrated into a broader decision-making framework.
Source: Rawson, Timothy M., et al. “Management of Bacterial and Fungal Infections in the ICU: Diagnosis, Treatment, and Prevention Recommendations.” Infection and drug resistance (2023): 2709-2726.
