Bacteremia plays a vital role in illness and death among critically ill patients in Intensive Care Units (ICU). Factors like invasive procedures, long hospital stays, weak immune systems, and mechanical ventilation elevate the risk of bloodstream infections and the use of broad-spectrum antibiotics in ICUs. This practice contributes to the growth of multidrug-resistant (MDR) pathogens. Antimicrobial resistance (AMR) has become a global health issue. The World Health Organization (WHO) has emphasized the great demand for systematic monitoring of antimicrobial use [1]. Measures such as Defined Daily Dose (DDD) and Days of Therapy (DOT) are commonly used to evaluate antibiotic consumption. DDD shows the strength of antibiotic exposure, while DOT indicates how long treatment lasts, regardless of dosage [2,3]. It is necessary to understand the correlation between consumption metrics and patterns of antimicrobial resistance. This knowledge will help create a targeted antimicrobial stewardship program (AMSP). AMSP initiatives aim to improve antibiotic usage, reduce toxicity, lower costs and address AMR. De-escalation based on culture and sensitivity results stands out as one of the most effective stewardship strategies [4,5]. This study looks at patterns of antibiotic use through DDD and DOT metrics and connects them with AMR trends in ICU patients diagnosed with bacteremia. Aims and objectives: To evaluate the number of patients with positive blood cultures in ICU and measure antibiotic consumption using DDD and DOT metrics. To examine antimicrobial use, microbiological findings and stewardship interventions, including culture-guided de-escalation practices among critically ill adults with bloodstream infections

A prospective cross-sectional study was conducted over three months period (January 2025 to March 2025) in the ICU of SRM Medical College Hospital and Research Centre, Kattankulathur, Chengalpattu District, Tamil Nadu. The study was approved by institutional ethics committee, ethical number is SRMIEC-ST1124-1895. Before enrollment of patients, written informed consent was obtained from all eligible patients or their legal guardians. Inclusion criteria: Adult patients aged 18 and above who were admitted to the ICU with microbiologically confirmed positive blood cultures and patients receiving antimicrobial therapy for at least one day were included in the study. Exclusion criteria: The patients below 18 years of age or receiving antimicrobial treatment outside ICU or disinterested patients were excluded from the study. Detailed demographic information, clinical characteristics, blood culture results, antimicrobial regimens, and patient outcomes were systematically collected using a structured form. This method ensured consistency and completeness of the clinical and microbiological data recorded for each participant. Antimicrobial use was assessed using standardized WHO method [6]. In detail, the DDD was calculated by dividing the total administered antimicrobial dose by the WHO assigned standard DDD for each agent. DOT was recorded as the total number of days a patient received a specific antimicrobial, regardless of dosage changes. The antimicrobial resistance profiles of the isolates were classified into multidrug-resistant (MDR) and extensively drug-resistant (XDR) categories based on widely accepted criteria [7]. Stewardship interventions were noted and categorized into three groups: de-escalation, escalation, and no change, depending on how antimicrobial regimens were adjusted after culture results and clinical assessment [8].

The study included 50 bloodstream infection positive patients, of which 36% (18 patients) were between 51 and 70 years of age, with a slightly higher proportion of males. The predominant pathogens were gram-negative organisms such as Klebsiella pneumoniae (28%), Acinetobacter baumannii (22%) and Escherichia coli (22%). Gram-positive isolates such as Staphylococcus aureus and Enterococcus faecalis formed a smaller proportion of the cases (Table 1). Category Prevalance (%) Age Group (years) 18-30 14 31-50 34 51-70 36 71-90 16 Gender Female 44 Male 56 Organism Klebsiella pneumoniae 28 Acinetobacter baumannii 22 Escherichia coli 22 Staphylococcus aureus 12 Pseudomonas aeruginosa 12 Enterococcus faecalis 4 Table 1. Age-wise and gender-wise distribution of patients and organisms isolated from blood cultures.14 patients in 18-30 years,34 patients in 31-50 years,36 patients in 51-70 and 16 patients in 71-90 years.Male[56] patients are more than female[44] patients.Klebsiella pneumoniae is the predominant organism which was isolated in 28 patients followed by Acinetobacter baumannii and Escherichia coli in 22 patients each,Pseudomonas aeruginosa in 12 patients and least being Enterococcus faecalis isolated in blood from 4 patients. Antibiotics were dde-escalated in 27 case s,escalated in 10 cases and did not change in 13 cases(Figure 1).Antimicrobial were When antimicrobial usage patterns were evaluated, empirical therapy showed a mean DDD of 4.95 and an average DOT of 3.9 days, reflecting the use of broader initial coverage (Fig 2 and 3). Once culture and susceptibility data were available, definitive therapy demonstrated a reduction in DDD to 4.05 and a slight increase in DOT to 4.3 days, indicating dose adjustments and treatment refinement (Fig 2 and 3). Stewardship interventions played a significant role, with de-escalation occurring in over half of the patients, while smaller proportions required escalation or had no change in therapy. Importantly, patients infected with MDR or XDR organisms experienced notably higher mortality (1%), underscoring the clinical impact of resistant pathogens in the ICU setting.

This study evaluates the use of antimicrobials and resistance patterns among culture-positive patients admitted to a tertiary care intensive care unit. Critically ill patients are especially vulnerable due to the initiation of antimicrobial therapy without prior confirmation of infection. However, this approach significantly increases selective pressure, leading to the growth and spread of resistant organisms in ICUs. The age distribution in this study showed that most patients were middle-aged or elderly. This trend indicates a strong correlation between long-term health issues, weakened immune systems, and frequent healthcare visits among older adults. These factors make them more susceptible to bloodstream infections [9]. This result corroborates with the reports of Lat et al. (2021) that higher prevalence of male patients may be due to differences in underlying health conditions and how they seek care[10]. In the present study, the major causes of bacteremia are gram-negative organisms such as Klebsiella pneumoniae (28%), Acinetobacter baumannii (22%), and Escherichia coli (22%). This microbiological profile finding is similar to patterns seen in ICUs globally, where gram-negative bacilli lead bloodstream infections because of their high survival rate and resistance in hospital settings [11,12]. The ongoing presence of Acinetobacter spp. and Klebsiella spp. is concerning, as these pathogens often cause outbreaks and are resistant to many antimicrobial classes [13]. The assessment of antimicrobial use showed higher DDD values during the empirical phase than during definitive therapy. This indicates great clinical demand to initiate broad-spectrum antimicrobial regimens in critically ill patients suspected of having sepsis, where delays in effective treatment can lead to higher mortality. Once culture and susceptibility results were available, the decrease in definitive DDD suggests better dose optimization and narrowing of the antimicrobial spectrum. Stewardship-driven ICU studies have observed similar reductions following microbiological confirmation [14]. Conversely, DOT values were slightly higher during definitive treatment. DOT measures how long patients receive antimicrobials regardless of dose, and its increase during the definitive phase likely means that clinicians completed an appropriate treatment course after identifying the cause of the infection [15]. This pattern shows that doctors maintained suitable treatment durations while avoiding unnecessary dose increases, highlighting how DDD and DOT work together as indicators for stewardship. The correlation analysis revealed a strong interlink between empirical and definitive DDD and a moderate to strong link between empirical and definitive DOT. These findings suggest that patients needing more antimicrobial exposure at the start often continue to require prolonged therapy. This likely reflects greater illness severity, delayed source control, or infections with resistant organisms. ICU surveillance studies of Huttner et al. (2019) have observed similar connections between antimicrobial use and clinical severity[16]. Importantly, these correlations imply inappropriate continuation of therapy and highlight the need for personalized treatment decisions based on patient responses and lab results. This study reveals that Antimicrobial Resistance (AMR) significantly impacts patient clinical outcomes, particularly in patients with MDR and XDR, leading to worse outcomes and increased mortality. This finding aligns with global evidence showing that resistant infections lead to delayed effective treatment, longer ICU stays, worsening organ issues, and higher healthcare costs [17,18]. The existence of resistant Klebsiella pneumoniae and Acinetobacter baumannii in ICU highlights the critical necessity for continuous resistance surveillance and stringent infection control protocols [19,20]. Overall, this study emphasizes the importance of systematic monitoring of antimicrobial use in ICUs. Using both DDD and DOT provides a detailed understanding of the intensity and duration of therapy. When combined with microbiological data and stewardship oversight, these metrics can help guide safe prescribing, reduce unnecessary antimicrobial use, and limit the spread of resistance. Ongoing evaluation of antimicrobial use trends, along with timely microbiological feedback, is crucial for improving outcomes in critically ill patients with bloodstream infections..

In conclusion, this study highlights the importance of antimicrobial consumption indicators like DDD and DOT, which provide useful information about prescribing habits in ICU patients with bacteremia. The difference between empirical and definitive therapy clarifies the essentiality of culture-based optimization. High rates of MDR and XDR necessitate strong antimicrobial stewardship and regular surveillance. Improving AMS programs, encouraging timely de-escalation, and tracking antimicrobial usage are crucial for lowering AMR burden and enhancing patient outcomes. Clinical significance: The relationship between antimicrobial consumption and antimicrobial resistance in studied using the primary outcome indicators Defined Daily Dose and Days of Therapy. Our study provides and evidence that this can help in the selection of appropriate antibiotic therapy in critically ill patients reducing inappropriate antimicrobial use also limiting the spread of resistant pathogen.

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