Hospital-acquired pneumonia: symptoms, diagnosis, treatment

Hospital-acquired pneumonia is a lower respiratory tract infection that occurs at least 48 hours after hospitalization and is not associated with intubation. The primary mechanisms of infection are aspiration of oropharyngeal microbial flora and bioaerosols from the healthcare facility environment, with hematogenous spread being less common. Gram-negative bacteria and Staphylococcus aureus predominate among pathogens, with resistance patterns determined by local conditions. [1]

The clinical significance of hospital-acquired pneumonia is due to increased mortality, length of hospital stay, and treatment costs. Timely etiotropic therapy and optimized diagnostic approaches have been shown to improve outcomes, while excessive and untimely antibiotic prescriptions increase resistance selection. Balancing the speed of treatment initiation and accurate diagnostic verification is a central challenge in patient management. [2]

International recommendations are unanimous in their key principles: early empirical therapy when the likelihood of severe infection is high, preference for short courses when progression is favorable, and mandatory adaptation of the regimen based on microbiological and surveillance data. These principles are complemented by antibacterial diligence measures, including de-escalation and duration control. [3]

In recent years, the emphasis has shifted to personalization at the patient's bedside: severity stratification, the use of biomarkers for early stopping of antibiotics, reliance on local cumulative antibiograms and the AWaRe system to select less “resistant” alternatives with comparable efficacy. [4]

Epidemiology

The incidence of hospital-acquired pneumonia varies between departments and populations, reflecting differences in the invasiveness of procedures, the burden of comorbidities, and the structure of microbial resistance. In acute hospitals, the proportion of this infection remains one of the largest among hospital-acquired bacterial diseases and significantly impacts antibiotic consumption. [5]

The risk is particularly high in intensive care unit patients, the elderly, and individuals with chronic lung and cardiovascular diseases. Systematic reviews highlight the contribution of resistant Gram-negative pathogens, which correlates with prior antimicrobial exposure and duration of hospitalization. [6]

Mortality depends on the severity, timeliness of adequate empirical therapy, and the presence of resistance. Implementation of guideline-based protocols is associated with a reduction in the duration of antibiotic therapy and relapse rates without worsening outcomes. [7]

In recent years, there has been increased attention to standardized short-course treatments, reflected in international guidelines and supported by real-world data, including reduced treatment duration without increasing complications. This has implications for both clinical practice and healthcare systems. [8]

Reasons

The etiologic spectrum includes Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter, and methicillin-resistant Staphylococcus aureus, the proportions of which depend on the department and previous antibacterial exposure. The choice of the initial regimen should be based on local susceptibility data for the past twelve months. [9]

The source of the pathogen is most often endogenous—colonization of the oropharynx and stomach followed by microaspiration. Exogenous sources include contaminated surfaces, equipment, and personnel hands, which emphasizes the role of infection control and hand hygiene. [10]

The contribution of atypical pathogens to hospital-acquired pneumonia is small, and routine coverage with active agents is not recommended without specific indications. This avoids unnecessary spectrum broadening and reduces the risk of resistance selection. [11]

The resistance profile is rapidly changing under the influence of local antibiotic prescribing practices, where the AWaRe framework serves as a guide for balancing efficacy and the “resistogenic” potential of a class. [12]

Risk factors

Key factors include age, prolonged hospitalization, prior systemic antibacterial therapy, use of acid inhibitors, impaired consciousness and swallowing, tube feeding, as well as chronic lung disease and immunodeficiency. Their combination increases the likelihood of both the infection itself and the presence of a resistant pathogen. [13]

Procedural risk factors include invasive chest and abdominal procedures, prolonged high-flow oxygen support, frequent bronchoscopies, and aspirations. Adherence to prophylaxis protocols reduces the burden of complications. [14]

Environmental factors—overcrowding, staff shortages, inadequate hand hygiene, and equipment reprocessing—directly correlate with the incidence of hospital-acquired infections. Management measures have a significant preventative effect. [15]

A number of clinical features increase the likelihood of a resistant pathogen in a particular case: recent use of broad-spectrum antigens, intensive care unit stay, colonization with resistant strains. This serves as a basis for expanding the initial coverage followed by de-escalation. [16]

Pathogenesis

The primary route is microaspiration of the colonized oropharynx when defense mechanisms, including the cough reflex and mucociliary clearance, are impaired. Epithelial damage, hypoxia, and local inflammation create conditions for the adhesion and invasion of pathogens. [17]

Dysbiosis and colonization with resistant strains are caused by previous antibiotic use and tube feeding. Acid suppression also plays a role, altering the microbiota of the upper gastrointestinal tract and increasing the risk of bacterial aspiration. [18]

The development of inflammation is accompanied by the release of cytokines, disruption of the alveolar-capillary barrier, and the formation of exudate, which impairs ventilation-perfusion relations and gas exchange. In some patients, thromboinflammatory mechanisms are also present. [19]

Resistant pathogens exhibit additional virulence factors and the ability to form biofilms on medical equipment, which supports persistence and reduces the effectiveness of therapy. This justifies the need for source control and replacement of contaminated systems. [20]

Symptoms

Classic manifestations include fever, cough with purulent sputum, increasing dyspnea, deteriorating gas exchange, and infiltrates on imaging. However, in elderly and debilitated patients, symptoms may be subtle, with tachypnea and hypoxemia becoming the leading signs. [21]

The onset often coincides with deterioration in respiratory support and hemodynamic parameters. It is important to consider that congestive heart failure and thromboembolic complications can mimic pneumonia, requiring targeted diagnostic testing. [22]

Laboratory evidence of inflammation supports, but does not confirm, the diagnosis, as inpatients often have alternative sources of inflammatory response. Therefore, the assessment is performed in conjunction with imaging and microbiology. [23]

Rapid deterioration with signs of systemic reaction and perfusion disturbances requires immediate therapy according to severe infection protocols with the first administration of effective antibiotics in a short period of time. [24]

Forms and stages

It is common practice to distinguish between hospital-acquired pneumonia in patients without mechanical ventilation and pneumonia that develops while ventilated. Within hospital-acquired pneumonia, mild, moderate, and severe forms are distinguished based on signs of respiratory failure, the volume of infiltrates, and the systemic response. These severity levels guide the choice of initial regimen and treatment location. [25]

The clinical course includes an early phase with predominantly inflammatory manifestations and a stabilization phase during therapy. In an unfavorable scenario, a septic course with multiorgan dysfunction develops, requiring escalation of intensive care. [26]

Relapse and superinfection are possible with an initially inadequate empirical regimen, with untimely de-escalation, and with a violation of source control. Therefore, dynamic assessment after forty-eight to seventy-two hours is a standard element of management. [27]

The presence of a resistant pathogen is not equivalent to an unfavorable outcome, provided that the therapy is adequate in terms of sensitivity and the course is of sufficient duration without unnecessary prolongation. [28]

Complications and consequences

Acute complications include respiratory failure, septic shock, acute respiratory distress syndrome, pleural complications, and secondary bacteremia. The risk of complications increases with delayed effective therapy and unrecognized resistance. [29]

Long-term consequences include prolonged weakness, decreased exercise tolerance, and cognitive impairment, especially after intensive care unit (ICU) stay. Timely rehabilitation improves functional outcomes. [30]

Relapse and superinfection increase antibiotic consumption and the risk of resistance development, requiring strict antibacterial vigilance programs at the ward and hospital level. [31]

Reduction in the incidence of complications is achieved by standardization of routes, including early risk stratification, timely de-escalation and control of the duration of the course. [32]

Diagnostics

Diagnosis relies on a combination of clinical examination, imaging, and microbiology. Radiography is helpful for initial verification, but computed tomography is preferred for clarifying the location, determining the extent of the lesion, and ruling out alternatives. It is important to correlate the images with clinical examination to avoid overdiagnosis. [33]

Microbiological verification is performed before the start of antibiotic therapy or before the second dose in severe cases: blood cultures, sputum tests, and, if indicated, invasive lower respiratory tract samples. Collection should be performed using proper technique and with minimal delays in delivery to the laboratory. [34]

Biomarkers of inflammation and infection are useful for monitoring and discontinuing antibiotics, rather than for initiating therapy. Procalcitonin has found the greatest practical application as a tool for safely reducing the duration of treatment with favorable clinical and microbiological dynamics. [35]

If there are signs of a systemic reaction with a high probability of sepsis, antibiotics are administered without delay, in parallel with diagnostics, observing the time window recommended by international campaigns for the treatment of severe infection. [36]

Table 1. Minimum diagnostic kit for suspected hospital-acquired pneumonia

Situation	What to do immediately	Comment
Moderate suspicion	X-ray or CT scan, complete blood count, C-reactive protein	Compare with the clinic and risks of alternatives
Severe form	Two blood cultures, sputum, or invasive material before antibiotic administration	The fence should not delay the start of therapy.
Dynamics after forty-eight to seventy-two hours	Repeated clinical and laboratory evaluation, revision of diagnosis	The basis for de-escalation and stopping antibiotics
[37]

Differential diagnosis

Pulmonary edema, thromboembolic complications, exacerbation of chronic lung diseases, drug-induced injuries, and infection at other sites must be excluded. A comprehensive assessment of clinical, imaging, and microscopic data helps avoid excessive antibacterial therapy. [38]

Pleural processes, atelectasis, and pulmonary infarctions often mimic infiltrates. Computed tomography with an emphasis on distribution and dynamics helps to differentiate them. [39]

In intensive care unit patients, the inflammatory response can be caused by catheter-associated infections, urinary tract infections, colitis, which requires a broad diagnostic search before narrowing the antibacterial regimen. [40]

If rare pathogens or fungal infections are suspected, extensive testing as indicated and consultation with an infectious disease specialist are indicated. The choice of empirical regimen is adapted to these situations. [41]

Treatment

Initial therapy should be timely and adequate in covering potential pathogens and local resistance. In cases of high risk of severe disease and signs of sepsis, antibiotics are administered immediately, ideally within the first hour in shock. In the absence of shock but a high risk of infection, prompt administration is recommended after a brief diagnostic assessment. [42]

International recommendations establish a standard treatment duration of approximately seven days if the disease is showing favorable progress. Extension is possible only in cases of slow resolution of symptoms, complications, or the identification of a difficult-to-treat pathogen. This approach reduces relapses and antibiotic consumption without worsening outcomes. [43]

De-escalation is performed after 48 to 72 hours based on clinical and microbiological findings. Switching to a narrow spectrum or oral formulations in the event of stability is a mandatory element of antibacterial vigilance. Procalcitonin is considered an additional tool for early discontinuation of antibiotics when clinical improvement occurs. [44]

The choice of a specific empirical regimen depends on the local antibiogram and individual resistance risks. The AWaRe framework helps minimize the use of reserve classes, maintaining treatment efficacy and containing resistance selection at the hospital level. [45]

Table 2. Principles for selecting a starting scheme

Clinical situation	The basic idea	The next step
Low risk of resistance	Coverage of typical pathogens based on local data	Rapid de-escalation when improving
High risk of resistance	Expanded coverage taking into account local strains	Narrowing the scheme after microbiology
Signs of sepsis	Administer the first dose immediately	Parallel diagnostics and control of sources
[46]

Table 3. Duration of antibacterial therapy

Scenario	Recommended course	Comment
Favorable dynamics	About seven days	Standard of modern management
Slow resolution of symptoms	Individual renewal	Only on objective grounds
Use of biomarkers	Early Termination Support	Only in combination with a clinic
[47]

Table 4. The role of biomarkers in reducing the duration

Biomarker	Practical application	Restrictions
Procalcitonin	Supporting the decision to stop early when the dynamics are favorable	Do not use as a start trigger
C-reactive protein	Non-specific, dynamic assessment	Limited specificity
[48]

Table 5. Antibacterial prudence and AWaRe framework

Principle	What are we doing?	For what
De-escalation	Narrowing the scope of microbiology	Reducing resistance selection
Course reduction	Seven-day guideline	Fewer side effects and resistance
Access Group Preference	With comparable efficiency	Balance between efficiency and ecology
[49]

Prevention

Primary prevention relies on hand hygiene, source control, proper equipment reprocessing, staff training, and limiting unnecessary antibiotic use. Organizational measures, including adequate staffing and adherence to care protocols, have been shown to reduce the incidence of hospital-acquired infections, including pneumonia. [50]

Clinical measures include timely patient mobilization, control of dysphagia and aspiration risks, nutritional optimization, cautious acid suppression, and active identification and elimination of factors that contribute to colonization by resistant strains. Regular analysis of local antibiograms and training of physicians in AWaRe principles enhance the preventive effect. [51]

Forecast

The prognosis is determined by the severity of the disease at the time of initiation of therapy, the adequacy and speed of regimen selection, the presence of resistance, and comorbidities. Implementation of protocols with early initiation and short courses improves clinical outcomes and reduces the length of hospitalization. [52]

Even in the presence of a resistant pathogen, timely treatment adjustments based on susceptibility, source control, and strict antibacterial vigilance can reduce the risk of complications and relapses. Rehabilitation and a multidisciplinary approach improve long-term recovery. [53]

FAQ

• Should antibiotics be started before culture results?

If there is a high probability of severe infection and signs of sepsis, the first dose should not be delayed. Microbiological samples should be collected as soon as possible, but they should not delay the start of life-saving therapy. [54]

• What is the standard course length?

If the dynamics are favorable, a course of approximately seven days is recommended, with a review at the forty-eighth to seventy-second hour and de-escalation based on microbiological criteria. Extension is possible only if objectively indicated. [55]

• Is there a role for biomarkers?

Procalcitonin is useful as a tool to support early discontinuation of antibiotics in the setting of clinical improvement. Its use as a criterion for initiating therapy is not recommended. [56]

• How to reduce the risk of sustainability at the department level?

Strict de-escalation, short courses, priority of access groups according to the AWaRe framework with comparable effectiveness and systematic analysis of local susceptibility are the basic elements of antimicrobial diligence programs. [57]