European Journal of Cardiovascular Medicine

Ventilator-associated pneumonia (VAP) is a serious and common infection that occurs in patients who are on mechanical ventilation for extended periods. It is defined as pneumonia that develops more than 48 hours after the initiation of mechanical ventilation. VAP is a significant cause of morbidity and mortality in critically ill patients, particularly those in intensive care units (ICUs). It prolongs hospitalization, increases the need for intensive care, and results in higher healthcare costs. Furthermore, the development of VAP is often associated with poor outcomes such as increased duration of mechanical ventilation, prolonged ICU stays, and higher mortality rates. [1]

The pathogenesis of VAP is influenced by a combination of host factors and the ventilator itself. Mechanical ventilation impairs normal pulmonary defense mechanisms, such as the cough reflex and mucociliary clearance, which makes patients more susceptible to infections. In addition, the insertion of an endotracheal tube creates a direct pathway for pathogens to enter the lungs. Aspiration of secretions from the upper airways, bacterial colonization of the endotracheal tube, and the formation of biofilms are some of the critical factors contributing to the development of VAP. [2]

The pathogens responsible for VAP are predominantly bacterial and include Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, and Staphylococcus aureus (including methicillin-resistant Staphylococcus aureus or MRSA). Other less common pathogens, such as Enterobacter spp., Streptococcus pneumoniae, and Haemophilus injluenzae, have also been implicated in VAP. The bacterial composition may vary depending on several factors, including hospital practices, patient population, and the geographical region. Multidrug-resistant (MDR) organisms have become a major concern in the treatment of VAP, making the identification of resistant pathogens particularly important for effective treatment. [3]

The rise of antibiotic-resistant pathogens has been a major challenge in the management of VAP. Overuse and misuse of antibiotics in ICU settings contribute significantly to the development of antimicrobial resistance. Resistance to common antibiotics such as beta-lactams, carbapenems, and quinolones has been observed in several pathogens responsible for VAP. The emergence of extended-spectrum beta-lactamases (ESBLs), carbapenem-resistant Acinetobacter and Pseudomonas, and MRSA has made it more difficult to treat these infections. Inadequate treatment of VAP can lead to treatment failures, longer ICU stays, increased risk of complications, and higher mortality rates. Therefore, understanding local antibiotic resistance patterns is crucial for the formulation of effective empirical treatment strategies. [4]

The diagnostic approach to VAP typically involves clinical evaluation, microbiological testing, and imaging. Tracheal aspirates are the most commonly used specimens for microbiological diagnosis, although bronchoalveolar lavage (BAL) is considered the gold standard in some cases. Tracheal aspirates are easier to obtain and less invasive, making them ideal for routine testing in critically ill patients. Once pathogens are identified, antimicrobial susceptibility testing is conducted to determine the most effective antibiotics for treatment. This process helps to guide therapy, particularly in cases of suspected multidrug resistance. [5]

Antibiotic susceptibility testing is performed using various methods, such as disk diffusion, broth microdilution, and automated systems like Vitek or Phoenix. These methods allow for the determination of the minimum inhibitory concentration (MIC) of antibiotics, which is used to classify pathogens as susceptible, intermediate, or resistant to specific antibiotics. The results of these tests are critical in choosing the appropriate empirical therapy and in reducing the risk of selecting for resistant bacteria. Regular surveillance of antibiotic resistance patterns is essential in updating clinical guidelines and ensuring that antibiotic therapies remain effective. [6]

In ICU settings, several factors contribute to the high rate of VAP, including the type of ventilator, patient characteristics (such as age, comorbidities, and immune status), and the length of mechanical ventilation. The longer a patient remains on mechanical ventilation, the higher the risk of developing VAP. Studies have shown that the risk of VAP increases significantly after 48 hours of ventilation. Other risk factors include the use of sedatives, poor oral hygiene, and the presence of invasive devices. Identifying these risk factors is important for preventing VAP and minimizing its impact. [7]

Prevention of VAP involves a multi-faceted approach, including proper ventilation techniques, early extubation, good oral care, and strict infection control practices. Strategies such as elevating the head of the bed, using subglottic suctioning to remove secretions, and administering prophylactic antibiotics in high-risk patients have been shown to reduce the incidence of VAP. Additionally, improving hand hygiene and sterilization practices in the ICU environment can help reduce the transmission of resistant bacteria. However, despite these efforts, VAP remains a major concern in critically ill patients, underscoring the need for ongoing research into its pathophysiology and treatment. [8]

The clinical outcomes of patients with VAP depend on vanous factors, including the pathogen responsible for the infection, the timing of appropriate antibiotic therapy, and the presence of underlying health conditions. Early initiation of appropriate antibiotics is associated with better outcomes, while delayed treatment can lead to complications such as septic shock, multi-organ failure, and increased mortality. Moreover, the use of broad-spectmm antibiotics in patients with VAP increases the risk of developing antibiotic resistance, highlighting the need for rapid pathogen identification and targeted therapy. [9, 10]

This study aims to contribute to the understanding of the antibiotic resistance patterns and sensitivity profiles of bacteria responsible for VAP in mechanically ventilated patients. By focusing on tracheal aspirates collected from critically ill patients, the study will identify the most common pathogens, analyze their resistance to various antibiotics, and assess how these patterns impact patient outcomes. The findings of this research will help improve empirical treatment strategies and guide healthcare providers in making more informed decisions about antibiotic therapy for VAP.

AIMS AND OBJECTIVES OF THE STUDY

AIM:

• To study the antibiotic resistance pattern and sensitivity in ventilator associated pneumonia

 OBJECTIVES:

• To identify the bacterial orgamsms isolated from endotracheal aspirates of mechanically ventilated patients.
• To determine the antibiotic susceptibility profile of these isolates.
• To evaluate the relationship between duration of mechanical ventilation and incidence of resistant infections.

The study was conducted at the Medical Intensive Care Unit (MICU) of HIMS, Hassan, which provided a suitable setting due to its diverse patient population and advanced medical facilities. The ICU at HIMS handles critical care patients, many of whom require mechanical ventilation, making it an appropriate setting to study ventilator-associated conditions such as VAP. This environment allowed for the observation and documentation of clinical data on patients receiving ventilator support, as well as the collection of samples for microbiological analysis. The setting also provided the necessary medical infrastructure for performing diagnostic tests, such as culture and sensitivity testing, to identify the pathogens associated with VAP.

The study used a consecutive sampling technique, where patients who met the inclusion criteria and were admitted to the ICU were enrolled. This method allowed for the systematic inclusion of participants in the study, ensuring that the sample accurately represented the patient population in the ICU. Consecutive sampling minimized bias, as patients were enrolled in the study as they were admitted to the ICU, ensuring the sample included a diverse range of patients with different conditions requiring mechanical ventilation. This approach also facilitated a practical and feasible way to gather data over the course of the year.

The study aimed to include 65 patients as the sample size from study Mukherjee et al. This number was chosen based on the expected patient load in the ICU and the need for a sufficiently large sample to detect meaningful patterns in antibiotic resistance and pathogen isolation. The sample size was also based on statistical power calculations, ensuring that the study would have enough data to allow for reliable conclusions. The sample size was manageable within the study's one-year duration, allowing for proper monitoring and analysis of each patient's condition.

INCLUSION CRITERIA

• Patients aged more than 18 years admitted to the ICU and requiring mechanical ventilation for > 48
• Patients with clinical suspicious of ventilator-associated respiratory infection (e.g., fever, leukocytosis, purulent secretions, new infiltrates on imaging).
• Patients from whom endotracheal aspirates were collected and sent for culture and sensitivity.
• Patients admitted to the ICU of the tertiary care hospital during the study period

EXCLUSION CRITERIA

• Patients aged less than 18 years
• Patients with pre-existing lung infections prior to intubation (e.g., lung abscess).
• Patients with known immunosuppression (e.g., post-transplant, chemotherapy, HIV).

Table 1: ICU Admission Diagnosis of Mechanically Ventilated Patients

Table 2: Comorbidities in Mechanically Ventilated Patients

Table 3: Isolated Pathogens in Mechanically Ventilated Patients

Table 4: Antibiotic Resistance Patterns in Mechanically Ventilated Patients

Table 5: Antibiotic Sensitivity Trends in Mechanically Ventilated Patients

The primary aim of this study was to investigate the antibiotic resistance patterns of bacteria isolated from endotracheal aspirations in mechanically ventilated patients at a tertiary healthcare center. Additionally, the study sought to examine the clinical outcomes, including mortality rates, the impact of comorbidities, and the duration of mechanical ventilation, while identifying the most prevalent pathogens responsible for infections in this high-risk patient population. Through this investigation, the study aimed to assess how antibiotic resistance influences patient outcomes, particularly in terms of mortality, hospital stay, and the duration of mechanical ventilation.

The significance of this study lies in its ability to provide critical insights into the growing concern of multidrug-resistant organisms (MDROs) in the ICU setting, particularly with Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae. These pathogens, which are often resistant to multiple classes of antibiotics, present significant challenges in managing ventilator-associated pneumonia (VAP) and other hospital-acquired infections[11]. By identifying the most prevalent pathogens and their antibiotic resistance profiles, this study highlights the need for targeted empirical therapy, effective infection control practices, and the implementation of antimicrobial stewardship programs.

Age Distribution of Mechanically Ventilated Patients

In this study, the majority of mechanically ventilated patients were 2:70 years old, accounting for 33.85%, followed by those aged 60-69 years (30.77%). The age distribution of mechanically ventilated patients is consistent with findings in previous studies, where older adults showed a higher incidence of mechanical ventilation. Roychaudhury et al. (2014) reported a similar trend, noting that older adults, particularly those above 60 years, have a higher risk of requmng mechanical ventilation due to a greater burden of chronic comorbidities such as diabetes and cardiovascular diseases [12]. In addition, Rao et al. (2023) highlighted that the geriatric population is particularly vulnerable to complications such as ventilator-associated pneumonia (VAP), resulting in prolonged mechanical ventilation and increased mortality.

The findings of the current study are particularly relevant given the increasing global aging population, which will inevitably lead to a higher incidence of critical care admissions for older individuals. Mukherjee et al. (2018) also observed that age-related decline in immune function and the increasing prevalence of multimorbidity contribute to the vulnerability of older patients, making them more susceptible to severe infections that require ventilation [13]. The higher incidence in elderly patients underscores the importance of age-specific management strategies, such as optimized respiratory support and early identification of respiratory complications.

Gender Distribution of Mechanically Ventilated Patients

The study revealed that 64.62% of mechanically ventilated patients were male, with females accounting for 35.38%. This male predominance is consistent with previous studies, such as Hoque et al. (2020), who found a male-to-female ratio of 3:2 in ventilator-associated pneumonia (VAP) cases, which might be attributed to smoking and other gender-specific health behaviors [14]. Furthermore, Soni et al. (2016) observed that men are more likely to have severe respiratory failure, particularly due to conditions such as COPD exacerbations and cardiovascular disease [15].

The gender distribution in this study may reflect the broader epidemiological pattern where men, especially those with a history of smoking, are at greater risk for developing conditions leading to mechanical ventilation. However, the differences between male and female patients could also be influenced by healthcare access and underdiagnosis in females, especially in tenns of chronic respiratory conditions that predispose to ventilatory support.

ICU Admission Diagnosis

The most common ICU admission diagnosis in this study was pneumonia, affecting 21.54% of patients, followed by sepsis (16.92%). This finding is consistent with other studies such as Jani et al. (2019), which reported pneumonia as the leading cause of ICU admission and mechanical ventilation. Pneumonia, particularly hospital-acquired pneumonia (HAP), is a frequent trigger for respiratory failure, necessitating ventilatory support, and remains a major cause of mortality among mechanically ventilated patients.

Soni et al. (2016) also observed that pneumonia is one of the primary causes for mechanical ventilation, further corroborating our findings [13]. The association between sepsis and mechanical ventilation in our study also aligns with findings from Roychaudhury et al. (2014), who reported that sepsis is another leading cause of ICU admissions, often requiring intensive care management due to its potential to progress to multi-organ failure and ARDS[12].

The high incidence of pneumonia as a diagnosis emphasizes the need for timely and effective antimicrobial treatment strategies, as pneumonia is one of the most common and dangerous infections in ICU patients.

Comorbidities and Their Impact on Patient Outcomes

In this study, diabetes mellitus (DM) was the most prevalent comorbidity, affecting 49.23% of mechanically ventilated patients. Hypertension followed at 27.69%, and COPD was present in 10.77% of patients. These findings are consistent with Hoque et al. (2020), who noted that the majority of patients requiring mechanical ventilation have underlying chronic diseases like diabetes and COPD, which complicate their management and worsen their prognosis[16].

The findings of this study have significant implications for healthcare practice, particularly in the management of critically ill patients in the ICU. The high incidence of antibiotic resistance among commonly isolated pathogens underscores the need for tailored antibiotic therapies based on local resistance patterns and patient-specific factors. The study also emphasizes the importance of infection control measures to reduce the spread of multidrug-resistant organisms. Furthermore, the significant association between carbapenem resistance and increased mortality suggests the necessity of early detection and appropriate antibiotic escalation in managing critically ill patients. These findings can inform clinical decision-making and hospital protocols regarding empirical treatment and infection control in ICU settings.

Recommendations

Based on the study's findings, it is recommended that healthcare institutions implement regular antimicrobial surveillance and develop institution-specific antibiograms to guide empirical antibiotic therapy. Antimicrobial stewardship programs should be strengthened to minimize antibiotic overuse and reduce the emergence of multidrug-resistant pathogens. Additionally, early detection of resistant infections through rapid diagnostic tools could improve treatment outcomes. Ventilator-associated pneumonia (VAP) remains a significant concern, so preventative measures, such as oral care protocols and head-of-bed elevation, should be prioritized to reduce infection rates. Healthcare professionals must also receive training on proper antibiotic use, and infection control practices should be reinforced to mitigate the spread of hospital-acquired infections.

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