Nosocomial Pneumonia in the Era of Multidrug-Resistance: Updates in Diagnosis and Management

Abstract

Nosocomial pneumonia (NP), including hospital-acquired pneumonia in non-intubated patients and ventilator-associated pneumonia, is one of the most frequent hospital-acquired infections, especially in the intensive care unit. NP has a significant impact on morbidity, mortality and health care costs, especially when the implicated pathogens are multidrug-resistant ones. This narrative review aims to critically review what is new in the field of NP, specifically, diagnosis and antibiotic treatment. Regarding novel imaging modalities, the current role of lung ultrasound and low radiation computed tomography are discussed, while regarding etiological diagnosis, recent developments in rapid microbiological confirmation, such as syndromic rapid multiplex Polymerase Chain Reaction panels are presented and compared with conventional cultures. Additionally, the volatile compounds/electronic nose, a promising diagnostic tool for the future is briefly presented. With respect to NP management, antibiotics approved for the indication of NP during the last decade are discussed, namely, ceftobiprole medocaril, telavancin, ceftolozane/tazobactam, ceftazidime/avibactam, and meropenem/vaborbactam.

Keywords: hospital-acquired pneumonia; low-radiation CT; lung ultrasound; nosocomial pneumonia; novel antibiotics; rapid microbiological diagnosis; syndromic multiplex PCR panels; ventilator-associated pneumonia.

Figure 1

Common areas of study in LUS. (A) Location of the BLUE-points. Two hands of the same size as patient’s hands are used as reference, applied in a way that covers the anterior chest surface, with the upper finger positioned below the clavicle. The upper BLUE-point (UBP), represented with a triangle, is defined by the intersection of the third and fourth finger of the upper hand. The lower BLUE-point (LBP), represented with a rhombus, is defined in the middle of the lower palm. The posterolateral alveolar and/or pleural syndrome (PLAPS) point, represented with a circle, is located just above the diaphragm and behind the posterior axillary line (PAL). (B) Division of the hemithorax into six areas of study: three regions (anterior [Ant], lateral [Lat] and posterior [Pos]) from the front to the back, delineated by the midsternal line (MSL), the anterior (AAL) and posterior axillary lines (PAL). These areas are then subdivided into a superior (Sup) and inferior (Inf) region. BLUE points are also drawn as reference.

Figure 2

Common signs and artefacts in LUS. (A) Normally aerated lung parenchyma. The pleural line (PL) can be recognised as a hyperechoic horizontal line, surrounded by two ribs (bat sign). A-lines are reverberation artefacts which can be visualised as equidistant motionless horizontal lines. Note lung sliding is a dynamic sign and cannot be visualised in a static picture. (B) Partially aerated lung parenchyma. Abnormal presence of fluid in the lung parenchyma is responsible for the presence of B-lines (*), which are beam-like hyperechoic vertical artefacts arising from the PL. Note B-lines always reach the edge of the image and erase A-lines. (C) Completely de-aerated lung parenchyma. Consolidation originates a tissue-like appearance of the lung (TLAL), inside which air bronchogram (AB) might be visualised as hyperechoic images. (D) Subpleural consolidation (SPC). Subpleural consolidations are defined as small (<2 cm) rounded or triangular-shaped hypoechoic areas with ill-defined hyperechoic limits, in contact with the PL.

Figure 3

Role of chest CT in the diagnosis of nosocomial pneumonia. (A) CT scans can accurately differentiate between atelectasis versus pneumonia compared to CXR, especially among critically ill patients. The left lower lobe retrocardiac consolidation, with air bronchogram, consistent with nosocomial pneumonia, was not visualized on portable CXR, but manifested on CT. (B) CT scan may reveal mild infiltrates that are usually missed with conventional CXR. While right lung consolidation shown on this image was visible on CXR, CT allowed for better characterization and revealed a mild infiltrate on the left lower lobe. (C) A wide range of lung pathologies may have similar appearances on CT scan. This image illustrates the difficulty in establishing a differential diagnosis in a patient with acute respiratory distress syndrome (ARDS), with suspected VAP. (D) In-hospital transfer of critically ill patients represents a logistical challenge with potential risks. This image depicts the transfer of a patient with COVID-19 on extracorporeal membrane oxygenation (ECMO) support to a CT scanner, to rule out VAP.