Bloodstream infections (BSIs) are among the most serious clinical conditions encountered in medical practice and are associated with high morbidity and mortality worldwide. They represent a major cause of healthcare-associated infections and pose a significant burden on healthcare systems, particularly in developing countries [1]. The presence of viable microorganisms in the bloodstream, termed bacteremia, may occur with or without clinical manifestations. When bacteremia is accompanied by systemic inflammatory responses such as fever, chills, tachycardia, hypotension, and organ dysfunction, it can progress to sepsis or septic shock, conditions associated with poor clinical outcomes [1,2]. Bacteremia can be classified as transient, intermittent, or continuous based on the duration and source of microbial entry into the bloodstream. Transient bacteremia may occur following minor mucosal trauma or invasive procedures, whereas intermittent bacteremia is commonly associated with localized infections such as abscesses or deep-seated infections. Continuous bacteremia is usually seen in intravascular infections such as infective endocarditis or infections related to indwelling medical devices [3]. Patients who are immunocompromised, critically ill, or suffering from chronic diseases such as diabetes mellitus, renal failure, malignancy, or those undergoing prolonged hospitalization are at increased risk of developing bloodstream infections [2,4]. The etiological profile of bloodstream infections has evolved over the past few decades. Earlier studies reported Gram-negative bacilli as the predominant causative agents; however, a shift towards Gram-positive organisms, particularly Staphylococcus aureus and coagulase-negative staphylococci, has been observed in many hospital settings. Despite this shift, Gram-negative bacteria continue to play a major role in bloodstream infections, especially in developing countries, where organisms such as Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter species are frequently isolated [4,5]. Timely diagnosis of bloodstream infections relies heavily on blood culture, which remains the gold standard for detecting bacteremia. Isolation and identification of the causative organism, along with antimicrobial susceptibility testing, are essential for guiding appropriate therapy. Prompt initiation of effective antimicrobial treatment has been shown to significantly reduce morbidity, mortality, and duration of hospital stay [6]. However, the increasing prevalence of antimicrobial resistance among bloodstream isolates has complicated empirical therapy and emphasizes the need for continuous local surveillance [7]. Patterns of bacterial etiology and antimicrobial susceptibility vary considerably across geographical regions and healthcare institutions. Therefore, knowledge of local epidemiological data is crucial for formulating empirical treatment guidelines and hospital antibiotic policies. In view of the limited data available from Central India, the present study was undertaken to determine the aerobic bacterial profile of bloodstream infections and their antibiotic susceptibility patterns in a tertiary care hospital of Bhopal. The findings of this study aim to provide valuable insight into the prevailing pathogens and resistance patterns, thereby assisting clinicians in the rational management of patients with bloodstream infections.

Study Design and Setting A hospital-based descriptive study was conducted over six months in the Department of Microbiology of a tertiary care hospital in Bhopal. Sample Collection A total of 647 blood samples were collected from clinically suspected cases of bacteremia under strict aseptic precautions before initiation of antibiotic therapy. Laboratory Processing Blood samples were inoculated into culture bottles and incubated aerobically. Positive cultures were sub-cultured on Blood agar and MacConkey agar. Identification was performed using Gram staining and standard biochemical tests. Antimicrobial Susceptibility Testing Antibiotic susceptibility testing was carried out using the Kirby–Bauer disc diffusion method on Mueller-Hinton agar, and results were interpreted according to CLSI guidelines. Statistical Analysis Data were analyzed using SPSS software. Chi-square test was applied, and p < 0.05 was considered statistically significant.

Out of 647 blood samples, 106 (16.38%) showed positive growth. All isolates were unimicrobial. Culture positivity was higher in females (56.6%) than males (43.4%), though the difference was not statistically significant. Gram-negative organisms (55.66%) predominated over Gram-positive organisms (44.34%). Among Gram-negative isolates, Escherichia coli (29%) was the most common, followed by Klebsiella pneumoniae (27%) and Pseudomonas aeruginosa (14%). Among Gram-positive isolates, Staphylococcus aureus accounted for 64%, followed by Staphylococcus epidermidis (17%). Gram-positive isolates showed 100% sensitivity to vancomycin and linezolid. High resistance was noted against ampicillin and erythromycin. Gram-negative isolates were largely sensitive to ceftazidime, imipenem, ciprofloxacin, and ampicillin-sulbactam, while resistance to amoxicillin-clavulanic acid and cotrimoxazole was common. Table 1. Demographic distribution of study subjects (n = 647) Age group (years) Male n (%) Female n (%) Total n (%) 0–12 (Children) 112 (17.31) 82 (12.67) 194 (30.0) 13–18 (Adolescents) 31 (4.79) 19 (2.94) 50 (8.0) >18 (Adults) 199 (30.76) 204 (31.53) 403 (62.0) Total 342 (53.0) 305 (47.0) 647 (100) Chi-square = 5.48, p = 0.064 (not statistically significant) Table 2. Blood culture positivity rate Total samples Positive cultures Positivity rate (%) 647 106 16.38 Table 3. Distribution of positive blood cultures by age and gender (n = 106) Age group (years) Male n (%) Female n (%) Total n (%) 0–12 (Children) 21 (19.81) 17 (16.04) 38 (35.85) 13–18 (Adolescents) 2 (1.89) 2 (1.89) 4 (3.77) >18 (Adults) 23 (21.70) 41 (38.68) 64 (60.38) Total 46 (43.40) 60 (56.60) 106 (100) Chi-square = 3.70, p = 0.157 (not statistically significant) Table 4. Distribution of Gram-positive and Gram-negative isolates (n = 106) Type of isolate Number (n) Percentage (%) Gram-positive bacteria 47 44.34 Gram-negative bacteria 59 55.66 Total 106 100 Table 5. Age-wise distribution of Gram-positive and Gram-negative isolates Age group (years) Gram-positive n (%) Gram-negative n (%) Total 0–12 20 (18.87) 18 (16.98) 38 13–18 0 (0.00) 4 (3.77) 4 >18 27 (25.47) 37 (34.91) 64 Total 47 (44.34) 59 (55.66) 106 p = 0.113 (not statistically significant) Table 6. Distribution of Gram-positive bacterial isolates (n = 47) Organism Number (n) Percentage (%) Staphylococcus aureus 30 64.0 Staphylococcus epidermidis 8 17.0 Enterococcus faecalis 5 11.0 Streptococcus pyogenes 4 8.0 Total 47 100 Table 7. Distribution of Gram-negative bacterial isolates (n = 59) Organism Number (n) Percentage (%) Escherichia coli 17 29.0 Klebsiella pneumoniae 16 27.0 Pseudomonas aeruginosa 8 14.0 Salmonella typhi 7 12.0 Citrobacter spp. 5 8.0 Acinetobacter spp. 4 7.0 Proteus mirabilis 2 3.0 Total 59 100 Table 8. Antibiotic susceptibility pattern of Staphylococcus aureus (n = 30) Antibiotic Sensitive n (%) Intermediate n (%) Resistant n (%) Ampicillin 7 (23.33) 4 (13.33) 19 (63.33) Ampicillin–Sulbactam 13 (43.33) 10 (33.33) 7 (23.33) Amoxyclav 10 (33.33) 9 (30.00) 11 (36.67) Clindamycin 20 (66.67) 3 (10.00) 7 (23.33) Cotrimoxazole 5 (16.67) 10 (33.33) 15 (50.00) Cefoxitin 8 (26.67) 7 (23.33) 15 (50.00) Erythromycin 12 (40.00) 8 (26.67) 10 (33.33) Linezolid 30 (100) 0 0 Table 9. Antibiotic susceptibility pattern of Escherichia coli (n = 17) Antibiotic Sensitive n (%) Intermediate n (%) Resistant n (%) Amikacin 9 (52.94) 5 (29.41) 3 (17.65) Ampicillin 1 (5.88) 3 (17.65) 13 (76.47) Ampicillin–Sulbactam 8 (47.06) 3 (17.65) 6 (35.29) Amoxyclav 10 (58.82) 1 (5.88) 6 (35.29) Ceftazidime 8 (47.06) 1 (5.88) 8 (47.06) Ciprofloxacin 11 (64.71) 1 (5.88) 5 (29.41) Cotrimoxazole 8 (47.06) 2 (11.76) 7 (41.18)

The present study was conducted to determine the aerobic bacterial profile of bloodstream infections and their antimicrobial susceptibility patterns in a tertiary care hospital of Bhopal. Bloodstream infections remain a major cause of morbidity and mortality, particularly in hospitalized and immunocompromised patients, and early microbiological diagnosis is crucial for appropriate management [1,2]. In the present study, the blood culture positivity rate was 16.38%, which is comparable to findings reported in several Indian studies showing positivity rates ranging between 16% and 17% [7,8]. Similar isolation rates have been reported by Vijaya Devi et al. and Shafazand et al., indicating that bloodstream infections remain a significant clinical problem in tertiary care settings [7,8]. The relatively low culture positivity may be attributed to prior antibiotic therapy before blood sample collection, a common practice in referred patients [9]. A predominance of Gram-negative organisms (55.66%) over Gram-positive organisms (44.34%) was observed in this study. This finding is consistent with several Indian and international studies that have documented a rising trend of Gram-negative bacteremia, especially in hospital-acquired infections [4,10]. However, some studies have reported a higher prevalence of Gram-positive organisms, highlighting regional variations in etiological patterns [11]. Among Gram-negative isolates, Escherichia coli (29%) was the most common pathogen, followed by Klebsiella pneumoniae (27%) and Pseudomonas aeruginosa (14%). These findings are in agreement with previous studies that identify Enterobacteriaceae as the leading cause of bloodstream infections [3,7,15]. The high prevalence of non-lactose fermenters such as Pseudomonas and Acinetobacter species is particularly concerning due to their association with multidrug resistance and increased morbidity [4]. The isolation of Salmonella typhi in 12% of cases is noteworthy and reflects the continued burden of enteric fever in developing countries. Similar observations have been reported in Indian studies, emphasizing the importance of blood culture in febrile illnesses [7,12]. Among Gram-positive organisms, Staphylococcus aureus was the most common isolate (64%), followed by Staphylococcus epidermidis (17%). This finding aligns with global data demonstrating Staphylococcus aureus as a leading cause of bloodstream infections in both community and hospital settings [5,19]. The emergence of coagulase-negative staphylococci as significant isolates may be related to increased use of intravascular devices and prolonged hospital stays [16]. Antimicrobial susceptibility testing revealed that Gram-positive organisms showed 100% sensitivity to vancomycin and linezolid, which is consistent with reports from other studies [7,13]. High resistance was observed to ampicillin, erythromycin, and cotrimoxazole, likely reflecting widespread and indiscriminate antibiotic use. These findings underscore the importance of reserving glycopeptides and oxazolidinones for severe infections to prevent future resistance [14]. Gram-negative isolates demonstrated good sensitivity to ceftazidime, imipenem, ciprofloxacin, and ampicillin-sulbactam. Similar susceptibility patterns have been reported by Karlowsky et al. and Diekema et al., indicating that carbapenems and aminoglycosides remain effective against many Gram-negative bloodstream pathogens [4,15]. However, resistance to commonly used antibiotics such as amoxicillin-clavulanic acid and cotrimoxazole was high, highlighting the need for regular surveillance and antibiotic stewardship [17,18]. Overall, the study highlights the changing epidemiology of bloodstream infections and the growing challenge of antimicrobial resistance. Continuous monitoring of pathogen distribution and susceptibility patterns is essential for guiding empirical therapy, reducing mortality, and preventing the emergence of resistant strains [19,20].

The present study demonstrates that Gram-negative bacteria are the predominant cause of bloodstream infections in the study setting. E. coli and Staphylococcus aureus were the most common Gram-negative and Gram-positive isolates, respectively. Knowledge of local bacterial profiles and antimicrobial susceptibility patterns is essential for effective empirical therapy and formulation of antibiotic policies.

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