Multidrug-Resistant Organisms (MDROs) are microorganisms that have developed resistance to multiple groups of antimicrobial drugs, which limits the available treatment options and makes infections more challenging to manage. The screening of Multidrug-Resistant Organisms (MDROs) and the analysis of risk factors in Intensive Care Units (ICUs) is a critical area of research, particularly in tertiary care centers where patients are often at heightened risk due to their underlying conditions and the invasive procedures they undergo. The prevalence of MDROs in ICUs is concerning, with various studies indicating that these pathogens are responsible for a significant proportion of Healthcare-Associated Infections (HAIs) [1,2]. Resistance of common pathogens has been associated with multiple factors including increased length of hospital stay, broad antibiotic use and invasive devices [3,4].   Empirical antibiotic therapy in ICUs should be guided by local resistance patterns to ensure effective treatment. Studies have shown that inappropriate empirical therapy can lead to increased mortality rates, particularly in cases of infections caused by MDROs [5,6]. For instance, the inappropriate use of broad-spectrum antibiotics can not only fail to control the infection but also contribute to the further development of resistance [7]. Therefore, it is essential for healthcare providers to have access to updated data on local antimicrobial susceptibility trends to optimize treatment regimens [8,9].   Risk factors for acquiring MDRO infections in ICUs include prolonged mechanical ventilation, the presence of invasive devices and prior antibiotic exposure [10,11]. Specifically, patients who have undergone prolonged ICU stays are at a greater risk of colonization and subsequent infection by resistant organisms, such as carbapenem-resistant *Klebsiella pneumoniae [12]. Furthermore, the interplay between colonization pressure and antibiotic exposure has been highlighted, indicating that the presence of colonized patients in the ICU can significantly increase the risk for non-colonized patients [13].   In addition to patient-specific factors, environmental factors within the ICU, such as infection control practices and antibiotic management programs, play a crucial role in the spread of MDROs [14-16]. The implementation of antibiotic management programs in ICUs has been shown to improve patient outcomes by reducing unnecessary antibiotic use and optimizing treatment protocols [17,18].   The screening of MDROs in ICUs is essential for identifying at-risk patients and implementing appropriate therapeutic strategies. Continuous surveillance of resistance patterns, combined with robust infection control measures and antibiotic management, is critical in combating the rising threat of multidrug-resistant infections in critically ill patients. So the study aimed to analyze the risk factors and antimicrobial susceptibility patterns associated with Multidrug-Resistant Organisms (MDROs).

A prospective study was conducted at Panimalar Medical College Hospital and Research Institute in the Intensive Care Units during November to December 2023. Patients admitted to the ICU were informed about the study and consent was obtained. Participants were divided into two groups based on the presence of MDROs, determined through antibiotic susceptibility patterns. Risk factors examined included previous antibiotic use, prolonged ICU stay, invasive procedures, immunocompromised states, underlying chronic diseases, surgical history, previous hospitalizations, use of immunosuppressive therapy, inadequate infection control practices, presence of indwelling devices, age, nutritional status, co-infections, high patient-to-nurse ratios and environmental factors.   Patients aged over 18 years admitted to the ICU were included, while inpatients below 18 years, those from wards and outpatients were excluded. The study utilized continuous sampling with a target sample size of 123 and appropriate statistical analyses, including the Chi-square test, were employed to evaluate the data.   Results were expressed using medians and percentiles for quantitative non-parametric measures, as well as numbers and percentages for categorical variables, to identify key factors contributing to the development of MDROs and inform improved infection control practices.   Sample Processing and Identification Clinical specimens collected from the ICU patients were processed using standard microbiological techniques. Following Gram staining, primary culture and isolation, the bacterial isolates were identified using the VITEK® 2 automated microbial identification system. Antimicrobial Susceptibility Testing (AST) was also performed using the VITEK® 2 system to determine the susceptibility patterns of the isolated organisms. The results were interpreted according to the applicable Clinical and Laboratory Standards Institute (CLSI) guidelines. Multidrug-Resistant Organisms (MDROs) were identified based on the antimicrobial susceptibility profiles of the isolates.

Culture Results, MDRO Cases and Demographic VariablesThe study analyzed MDRO prevalence among 123 ICU patients, with 34 culture-positive cases (14 males, 20 females) and 89 culture-negative cases. Culture-positive samples were predominantly from urine (17 cases), followed by blood (12), exudates (11) and respiratory samples (6). MDROs were identified in 16 cases, primarily from urine (11 cases) and were more common in females (11 cases) than males (5 cases). Age distribution showed higher MDRO prevalence in elderly females (71-80 years, 6 cases) and younger to middle-aged males (20-30 and 61-70 years, 2 cases each). These findings highlight gender and age-related trends, with urine being the most frequent source of MDROs, underscoring the need for targeted infection control and antimicrobial management (Table 1).   Table 1: Distribution of Culture Results, MDRO Cases and Demographic Variables of ICU Patients (n = 123) Gender Culture positive Culture Negative Male 14 41 Female 20 48 Total 34 89 Multiple Sample distribution Culture positive Culture Negative Blood 12 - Urine 17 - Exudate 11 - Respiratory 6 - Sample distribution MDR Non MDR Blood 5 7 Urine 11 6 Exudate 4 7 Respiratory 1 5 Total 21 25 Total Number of cases MDR NON MDR Culture Positive Patients 16 18 Gender Count = 16 MDRO - Male MDRO - Female 5 11 Age MDRO - Male MDRO - Female 20-30 2 2 31-40 0 0 41-50 0 0 51-60 1 1 61- 70 2 1 71- 80 0 6 81-90 0 1 Total 5 11   Patient Characteristics, Microbial Profile and Risk Factor Analysis The Figure 1 summarizes ICU patient data, highlighting microbial profiles, demographics and associated risk factors for infections. It lists patient ID, organism type, sample source, Gram classification, age, sex and key risk factors, including prior antibiotic use, prolonged ICU stay, comorbidities (e.g., diabetes, hypertension, COPD), invasive procedures and immunosuppressive therapy. Risk factors are tallied as "Multiple Risk Factors Total." MDROs, notably Klebsiella pneumoniae and Escherichia coli, were prevalent among elderly females and those with multiple risk factors, underscoring the importance of robust infection control and antimicrobial management in ICU management.     Figure 1: Patient Characteristics, Microbial Profile and Risk Factor Analysis   MDRO Patients Associated with Multiple Risk Factors The Table 2 highlights the number of risk factors associated with MDRO patients, with totals ranging from 1 to 8. Patient P001 had the higahest risk factor count (8), while others, such as P008, P009 and P011, had 7 risk factors each, indicating significant vulnerabilities. Moderate-risk patients (4-5 risk factors) included P010, P014 and P016, while minimal-risk patients (1-3 risk factors) included P002, P005, P007, P012, P013 and P015. Patients with higher risk factor counts were strongly associated with MDRO infections, emphasizing the need for focused infection control and preventive measures in vulnerable populations.   Table 2: MDRO Patients Associated with Multiple Risk Factors Patient ID MDRO patients associated With multiple risk factors total P001 8 P001 P001 P002 2 P002 P003 6 P004 1 P004 P005 3 P006 1 P007 3 P007 P008 7 P009 7 P010 4 P011 7 P012 1 P013 3 P014 4 P015 3 P016 5 P016

The study analyzed MDRO prevalence among 123 ICU patients, with 34 culture-positive and 89 culture-negative cases. The analysis revealed a culture-positive rate of 27.6% (34 cases), underscoring the significant prevalence of these pathogens in critical care settings. The predominance of urinary tract infections, with 17 cases identified, aligns with existing literature that highlights urinary tract infections as a common source of MDROs in ICU patients [19,20]. Notably, the demographic data indicating a higher incidence among elderly females, particularly those aged 71-80 years, suggests that age and gender are critical risk factors for MDRO infections in this population [21,22].   The identification of Klebsiella pneumoniae and Escherichia coli as the most common MDROs is consistent with findings from various studies that report these organisms as prevalent in ICU settings, often linked to prior antibiotic use and prolonged hospital stays [23,24]. The correlation between the number of risk factors and the likelihood of MDRO infection is particularly concerning; patients exhibiting multiple risk factors, such as prolonged ICU stays and invasive procedures, are at a significantly increased risk for acquiring these infections [25]. This is further supported by evidence that prolonged mechanical ventilation and the presence of comorbidities exacerbate the risk of colonization and infection by resistant organisms [26,27].   The data from this study highlight the critical need for targeted infection control measures and antimicrobial management strategies in ICUs. The association of multiple risk factors with MDRO infections emphasizes the necessity for vigilant monitoring and tailored interventions, especially for vulnerable populations such as elderly females [28,29]. Implementing robust infection control practices, including regular surveillance of microbial profiles and adherence to antibiotic stewardship programs, can mitigate the risk of MDRO transmission and improve patient outcomes [30,31].

The study found that MDROs were common among ICU patients, especially in elderly females and those with multiple risk factors like prior antibiotic use, prolonged ICU stays and comorbidities. The most frequent pathogens were Klebsiella pneumoniae and Escherichia coli, with urine being the primary source. These findings highlight the need for better infection control, proper antibiotic use and focused care for high-risk patients to reduce MDROs in ICUs.