Particularly in intensive care units (ICUs), antimicrobial resistance (AMR) is a rapidly growing global public health issue. Because of their severe underlying conditions, extended hospital stays, frequent exposure to intrusive devices, and heavy use of broad-spectrum antibiotics, ICU patients are particularly vulnerable to infections. Multidrug-resistant organisms (MDROs) that cause healthcare-associated infections dramatically raise morbidity, mortality, and medical expenses¹. With concerning resistance to several antibiotic classes, including carbapenems, gram-negative bacteria including Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae have become common ICU infections. Effective infection control and antimicrobial stewardship efforts, as well as the direction of empirical therapy, depend on an understanding of local antibiotic resistance patterns. The purpose of this study was to examine the antibiotic resistance trends and bacterial profile of isolates taken from tertiary care intensive care unit patients².

METHODS

Study Design and Setting

Over a 1-year period, a prospective observational study was carried out in the adult intensive care unit (ICU) of a tertiary care teaching hospital that treats critically sick surgical and medical patients in Telangana.

Study Population

During the study period, all ICU patients with microbiologically verified bacterial growth and clinical suspicion of infection were included. To reduce duplication and selection bias, only the initial isolate from each patient was examined.

Sample Collection and Microbiological Processing

Standard microbiological procedures were followed in the collection and processing of clinical specimens. Blood, urine, endotracheal aspirates, sputum, and wound swabs were among the sample types. The sample distribution was noted and examined as proportions with matching confidence intervals.

Bacterial Identification

Standard microbiological methods, such as Gramme staining, colony morphology, and biochemical tests, were used to identify the bacterial isolates.

Antimicrobial Susceptibility Testing

The Kirby-Bauer disc diffusion method was used to test for antimicrobial susceptibility, and the results were interpreted in compliance with CLSI recommendations. To show the accuracy of estimations, resistance rates were reported as proportions with 95% confidence intervals (95% CI).

Definition of Multidrug Resistance

According to widely recognised standards, multidrug resistance (MDR) is resistance to at least one antimicrobial agent in three or more antimicrobial classes.

Statistical Analysis

Descriptive statistical techniques were used to examine the data. Frequencies and percentages were used to sum up categorical variables. In order to assess the variability and dependability of resistance rates, 95% confidence intervals were computed for important proportions as needed.

RESULTS

Culture Positivity Rate

300 of the 420 clinical samples that were processed showed notable bacterial growth, resulting in a culture positive rate of 71.4% (95% CI: 67.0–75.7).

Distribution of Clinical Samples

The majority of samples (40.0%; 95% CI: 34.5–45.5) were endotracheal aspirates, followed by blood (26.0%; 95% CI: 21.1–30.9), urine (18.0%; 95% CI: 13.7–22.3), wound/pus samples (12.0%; 95% CI: 8.3–15.7), and sputum (4.0%; 95% CI: 1.8–6.2).

Distribution of Bacterial Isolates

Gram-negative bacteria accounted for 76.0% of isolates (95% CI: 71.2–80.8), while Gram-positive bacteria constituted 24.0% (95% CI: 19.2–28.8).

Acinetobacter baumannii was the most frequently isolated organism (30.0%; 95% CI: 24.8–35.2), followed by Pseudomonas aeruginosa (22.0%; 95% CI: 17.3–26.7) and Klebsiella pneumoniae (18.0%; 95% CI: 13.7–22.3).

Gram-positive bacteria made up 24.0% of isolates (95% CI: 19.2–28.8), whilst Gram-negative bacteria made up 76.0% (95% CI: 71.2–80.8).

The most often isolated bacterium was Acinetobacter baumannii (30.0%; 95% CI: 24.8–35.2), which was followed by Pseudomonas aeruginosa (22.0%; 95% CI: 17.3–26.7) and Klebsiella pneumoniae (18.0%; 95% CI: 13.7–22.3).

Antimicrobial Resistance Patterns

Gram-Negative Isolates

92% of isolates had ampicillin resistance (95% CI: 88.4–95.6). Third-generation cephalosporin resistance varied from 74% to 78% (95% CI roughly: 68.2–82.5). 69% of isolates had fluoroquinolone resistance (95% CI: 63.0–75.0).

For imipenem (95% CI: 41.5–54.5) and meropenem (95% CI: 38.6–51.4), carbapenem resistance was found in 48% and 45% of isolates, respectively. 6% of isolates had colistin resistance (95% CI: 3.0–9.0).

Gram-Positive Isolates:Methicillin resistance was seen in 45% of Staphylococcus aureus isolates (95% CI: 30.2–59.8). While all isolates remained sensitive to vancomycin and linezolid (100% susceptibility; 95% CI: 94.9–100), resistance to erythromycin and fluoroquinolones approached 50%.

Multidrug Resistance

A significantly greater MDR burden among Gram-negative organisms was seen in 68% of Gram-negative isolates (95% CI: 61.9–74.1) and 32% of Gram-positive isolates (95% CI: 21.2–42.8).

Bacterial Isolates

Gram-negative bacteria constituted 228 (76%) isolates, while Gram-positive bacteria accounted for 72 (24%).

DISCUSSION

Gram-negative organisms accounted for more than three-quarters of the isolates (76%; 95% CI: 71.2–80.8), indicating a high incidence of antibiotic resistance among bacterial isolates from ICU patients. The results are highly precise and reliable, as evidenced by the small confidence intervals seen for large resistance estimations^5,6.

Acinetobacter baumannii was the most common pathogen, accounting for 30% of isolates (95% CI: 24.8–35.2). Treatment options are severely limited by high rates of resistance to cephalosporins and carbapenems, with carbapenem resistance approaching 50%. Despite being modest (6%; 95% CI: 3.0–9.0), colistin resistance is clinically significant due to the scarcity of treatment options. Gram-positive resistance in ICU settings is still relevant, as seen by the incidence of MRSA (45%; 95% CI: 30.2–59.8). Nonetheless, the continued susceptibility to linezolid and vancomycin indicates that these medications are still effective when used as directed.
Gram-negative isolates have a greater percentage of MDR (68%; 95% CI: 61.9–74.1) than Gram-positive isolates, which highlights the critical need for focused antimicrobial stewardship and infection control measures in intensive care units^7,8.

CONCLUSION

More than two-thirds of the ICU bacterial isolates demonstrate multidrug resistance, reflecting a substantial burden of antibiotic resistance, especially among Gram-negative species. Consistent and clinically relevant resistance patterns are shown by the confidence intervals related to resistance estimate^9,10. To stop the spread of multidrug-resistant organisms and enhance patient outcomes in critical care settings, routine antimicrobial resistance surveillance with periodic ICU-specific antibiogram generation, sensible antibiotic use, and improved infection control practices are crucial.

DECLARATION

Conflicts of Interests: The authors declare no conflicts of interest.

Author Contribution: All authors have contributed in the manuscript.

Author Funding: Nill.

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