European Journal of Cardiovascular Medicine

Nosocomial infections, also known as healthcare-associated infections (HCAI), are serious and potentially life-threatening complications that can occur in healthcare settings, particularly in intensive care units (ICUs). Several factors contribute to the occurrence of these infections, including the severity of illness in patients, compromised immune systems, prior exposure to various antibiotics, frequent contact with healthcare workers, and the use of invasive devices such as urinary catheters, central lines, and endotracheal tubes in ICU settings. The types of organisms causing these infections and their sensitivity to antibiotics can vary between medical ICUs, surgical ICUs, wards, and community settings, with ICU isolates often showing higher rates of antimicrobial resistance. Numerous studies have been conducted to assess the prevalence of infections, the types of organisms involved, and their antibiotic sensitivity patterns in adult ICUs, but there is limited data available for the pediatric population. In a study by Weiss and colleagues, they likely found important insights into nosocomial infections among pediatric patients in ICUs (1). Understanding the specific microbiological landscape in pediatric ICUs is crucial for implementing appropriate infection control measures, selecting effective antimicrobial therapies, and ultimately improving patient outcomes.

It is crucial to wait for the culture report and antimicrobial sensitivity pattern before starting specific therapy in a suspected infection. This process may take time as it relies on the growth of organism in culture media. Understanding the prevalence of nosocomial infection and antibiotic sensitivity pattern in a particular region is essential for initiating empirical antibiotic therapy. The increasing antimicrobial resistance due to the excessive and irrational use of antibiotics is a significant global health concern( 2 ). Therefore, continuous surveillance in pediatric intensive care unit is necessary to detect nosocomial infections early, identify responsible organisms promptly, and begin appropriate antimicrobial therapy based on the culture sensitivity report.

Understanding the spectrum of positive blood culture in a specific unit can help identify the microorganism profile and their sensitivity to different groups of antibiotics. Monitoring sequential data of culture sensitivity patterns for the same organism over time can also be valuable in recognizing changes in antibiotic resistance, indicating the irrational use of specific antimicrobials.

The purpose of this study is to identify the common types of microorganism present in the pediatric intensive care unit in our center and to assess their resistance to antibiotics.

This study was conducted as prospective observational research in the pediatric intensive care unit (PICU) at Mahatma Gandhi Medical College and Hospital (MGMCH), Jaipur, Rajasthan, India, from July 1, 2022 to December 31, 2023.

Data collection involved recording the age and sex of the patients, the total number of cultures taken, specimen types, the number of positive cultures in different specimens, the organisms isolated from the culture specimens, and their antibiotic susceptibility and resistance patterns.

The PICU at our center is a state-of-the-art unit with 15 fully equipped beds with advanced intensive care equipments. Culture samples were collected following sterile procedures according to a standard protocol. The samples were collected immediately upon admission before the initiation of antibiotics, especially when clinically indicated, or before changing antibiotics for already admitted patients in cases of suspected sepsis with clinical deterioration or abnormal supportive laboratory parameters such as high total leukocyte count (TLC), high C- reactive protein (CRP), and high procalcitonin levels. 

Various types of samples, including blood, urine, endotracheal aspirates, swabs, etc. that were routinely sent for culture based on clinical indications were included in the study. Detailed clinical information related to each sample was recorded.

In the study, antimicrobial susceptibility testing was performed using the Vitek 2 Compact System. The results were interpreted according to the guidelines provided by the clinical and laboratory standards institute (CLSI) in 2022(3).

Positive isolates were categorized into gram- positive and gram-negative microorganisms. The antimicrobial susceptibility and resistance patterns of these isolates were meticulously documented.

The data was presented in the form of the number of isolates and the percentage of microorganism resistance to specific antimicrobial agents. This information provides insights into the effectiveness of various antimicrobial treatments against the identified microorganisms in the samples obtained from the patients.

Table 1: Types of culture and their positivity rates

Table 1 provides information about the distribution of positive culture results across different types of samples, which were send according to the clinical indication. Out of total 1116 different culture samples, 111 were came out to be positive during the study period. Positivity rate of Endotracheal sample (ET) was highest (23.3%) as compared to blood (7.6%) and urine sample (8.3%).

Table 2: Gender distribution

Table 2: From total 111 positive culture patients, 54 were male and 57 were female with male to female ratio was almost 1:1. Children with age group ≤6 years were 76%, whereas culture was found to be positive in only 24% of patients who were at the age of ≥ 6 years.

Table 3: Distribution of microorganism isolated in various cultures

Among the isolated agents, Acinetobacter species, including baumanniii and hemolyticus, were the most frequently encountered microorganisms, representing 18.9% of all positive cases. Following Acinetobacter species, coagulase negative staph (CNS) was the second most prevalent microorganism at 18 % (n=20) of all isolations. Staph aureus accounted for 9 % (n=10) of the positive cases.

Among gram-negative bacteria, Acinetobacter species were the most frequent, with 18.9%(n=21) positive cases. E.coli followed with 14.4 % of the positive cases. Klebsiella pneumoniae and pseudomonas aeruginosa shared an equal percentage of positive cases at 12.6% and 11.71% respectively.

TABLE 4 – Antibiotics resistance rates of Gram positive bacteria (%)

Table 4: Benzathine penicillin resistance was observed in 100% of CONS , 80% resistance in staph aureus and 50% resistance was observed in Enterococcus faecalis positive isolates. Methicillin resistant staphylococcus aureus( MRSA) was observed in 70% cases. Quinolone group of antibiotics were found to resistant in 65% of CONS, 100% of staph aureus and 75% of enterococcus faecalis. Linezolid and daptomycin were most effective antibiotics with no gram positive (GP) organism was documented resistant. Vancomycin was the most susceptible antibiotic after oxazolidinone and daptomycin with only 25% were reported as vancomycin resistant enterococcus (VRE). In newer drugs like teicoplanin, 30% of CONS and 37.5% of enterococcus faecalis cases were reported resistant. Trimethoprim-sulfamethoxazole also had good sensitivity against CONS and Staph aureus with only 20% resistant to CONS and 30% resistant to staph aureus.

TABLE – 5     Antibiotic resistance rates of gram negative bacteria

Table 5: Amongst all Gram-negative bacteria, resistance to 3^rd and 4^th generation cephalosporine group of antibiotics were higher as compared to combination therapy of cephalosporine plus beta lactamase inhibitor (Cefoperazone plus salbactum). 

Extended-spectrum beta lactamase (ESBL) (piperacillin and amoxiclav ) resistance was found as 81 % for Acinetobacter spp., 64.28% for klebsiella, 50% and 75% respectively for E.coli, and 46% and 84% in pseudomonas spp. Carbapenems were reported as very effective group against gram negative organisms with only 25% resistance found in klebsiella spp, 12.5% resistance in E. coli, 30% in pseudomonas spp. and only 14% resistance in Acinetobacter spp. Colistin remained most sensitive antibiotic with not a single gram negative organism was documented resistance to this antibiotic. Only a few cases were reported resistant to tigecycline with klebsiella spp showed 14% resistance, 12.5% in E.coli, 8% in pseudomonas spp and 9% in Acinetobacter spp.

Graph1:

Out of total 111 positive culture reports, blood culture positive were highest (n=46,41.4%) followed by endotracheal culture (n=35,31.5%) and urine culture (n=14, 12.6%).

Out of the 1116 culture samples sent from our PICU between July 2022 and December 2023, 111 were culture positive, resulting in a positivity rate of 9.94 %. This positivity rate is comparable to the rates reported in studies in India (4, 5, 6, 7) and abroad ( 8, 9, 10). However, the culture positivity rates reported in studies by Katyal A et al ( 24.86%)(11) and Wasihun et al (28%)(12) are significantly higher than the rate observed in our pediatric intensive care unit, potential factor could be because of patient population, sampling methods, geographic location and local epidemiology, antibiotic use and resistance patterns, and variability in healthcare practices. 

In our, study, we observed that the highest number of positive cultures were found in blood samples, accounting for 41.4% of cases ( 46/111). This was followed by E.T. culture, with 32% positivity ( 35/111), and urine cultures, which had a positivity rate of 14.4% ( 16/111). Interestingly, the positivity rates were much higher for E.T. cultures ( 23.3%) and pleural/peritoneal fluid cultures( 19.35%) compared to blood ( 7.6%), urine (8.3%), and CSF cultures( 3.67%). Our study’s findings on culture-positive specimen distribution were in line with Kumar KMA et al ( 5), which found tracheal culture positivity in 35.6% and E.T. culture positivity in 41.2% of cases, suggesting similar trends in culture positivity rates. The gender distribution of the 111 culture positive patients in our study was relatively equal, with 54 males and 57 females. This differ from adult study done by Kaur and singh (13), where males have been reported to have higher culture positivity rates, likely due to their role as primary caregivers and increased access to healthcare. However, this bias is not evident in pediatric patients. Additionally, we found that 75% of positive cultures were from children aged 6 years or younger, while only 25% of positive cultures belonged to individuals older than 6 years. Overall, our findings highlight the importance of considering different culture sources in diagnosing infections, as well as the age distribution of positive cultures in pediatric patients.

In present study, gram-negative bacteria accounted for 63% of the detected microorganisms, gram-positive bacteria made up 37% of the total isolates. It is interesting to note the varying prevalence of gram-positive bacteria ( GPB) and gram-negative bacteria( GNB) in different studies conducted around the world. The studies by Ashima Katyal (11), Ayşe Betül Ergül(8), Araya Gebreyesus Wasihun(12), and Banik A et(4) al all highlighted a higher prevalence of GPB over GNB in their finding. These findings ranged from GPB accounting for 57.4% to 72.2% of infections, while GNB ranged from 27.8 to 42.8%. Interestingly, multiple studies from different countries including India have shown a predominance of GNB in hospitalized patients, as reported by Gupta and Kashyap( 7) (58.3%GNB, 41.65%), Singh et al ( 14) (51.82% GNB, 46.56% GPB) and Kumar KMA et al ( 5)( 66.6% GNB, 33.3% GPB). These discrepancies in findings could be attributed to various factors such as geographic location, patient demographics, healthcare practices, or even variations in laboratory procedures and techniques used for bacterial identification. The differences in the prevalence of GPB and GNB in these studies highlight the complex nature of bacterial infections and the importance of understanding local epidemiology and patterns of bacterial resistance.

In our study, Coagulase Negative Staph (CNS) emerged as the most prevalent Gram-positive bacterium, accounting for 18% (n=20) of all isolations, followed by Staph Aureus at 9% (n=10). As reported by Ergul et al.(8), CNS was the most frequently isolated gram-positive bacteria, followed by enterococcus faecalis, in their study. Similarly, Wattal C et al (6) reported CNS as the most common isolate causing blood stream infections (BSIs) in ICU patients. In spite of the fact that CNS is a normal skin commensal, now a days we are getting pathogenic nature due to increasing number of indwelling devices in ICUs, ultimately increasing rate of antimicrobial resistance, financial burden, and poor clinical outcome (4, 15). On the contrary, S. aureus (37.5%) were the most commonly isolated Bacteria in the study done by Wasihun et al.(12), second common microorganism was CNS (30.6%).

In the realm of Gram-negative bacteria, the Acinetobacter group emerged as the most frequent identified microorganism with 18.9% (n=21) positive cases, followed by E. coli at 14.41% in present study. Klebsiella pneumoniae and Pseudomonas aeruginosa shared almost a similar percentage of positive cases. Among few cases of pyrexia of unknown origin investigated for blood culture, other gram negative microorganisms such as Burkholderia spp., Stenotrophomonas maltophilia, Salmonella typhi, Elizabethkingia meningoseptica recovered from culture. Ergül et al. (8) noted in their research that within Enterobacteriaceae, Klebsiella pneumoniae was the most commonly isolated species, followed by serratia spp., with E. coli being notably rare at 1.2%. Banik et al (4) highlighted that among Gram-negative pathogens, Enterobacteriaceae collectively contributed to the highest number of sepsis cases (41/98), primarily dominated by Klebsiella species and E. coli. However, Acinetobacter, classified as a non-fermenting bacillus, held a more prominent position as an individual bacterial genus. The Enterobacteriaceae family, known to cause bloodstream infections, has been reported to be the dominant gram-negative bacteria in some other research studies also( 9, 16).

Teicoplanin resistance was observed in 30% of coagulase-negative staphylococci (CNS) cultures in our study, while vancomycin resistance was not detected. Ergül et al. (8) reported no vancomycin resistance in CNS, but found teicoplanin resistance in 22.3% of cases. The rates of methicillin resistance in Staphylococcus aureus was 54.5% in study by Sağlam et al. (9), slightly lower than our study finding of 70% methicillin resistance. Contrary to aforementioned studies, Banik et al’s (4) research revealed a majority of methicillin-sensitive staphylococcus aureus ( MSSA) and a smaller proportion ( 13.6%) of methicillin-resistant staphylococcus aureus ( MRSA). Enterococcus spp. accounted for 25% of all cultured gram-positive microorganisms in our study, with 25% exhibiting vancomycin-resistant enterococci (VRE). Conversely, Kara et al. (17) reported a VRE frequency of 1.55%, while Ergül et al. (8) reported 3.6%.

In present study, gram-negative organism resistance to 3^rd and 4^th generation cephalosporine antibiotics was higher than when using cephalosporine plus beta-lactamase inhibitor(Cefoperazone plus salbactum). Previous study done by Gupta S et al (7) showed similar finding of good antimicrobial susceptibility to combination drugs like cefoperazone plus salbactum.  Factors responsible for antimicrobial resistance are multiple, which include lack of awareness about prevention of infection and, excessive and irrational use of antibiotics by health care professionals and patients(18). For Acinetobacter spp, the extended spectrum beta-lactamase ( ESBL) ( Piperacillin and amoxicillin plus clavulanic acid) resistance was 81% for each antimicrobial, 64% each for Klebsiella, 50% and 75% respectively for E. coli, and 46% and 84% respectively for pseudomonas spp. Carbapenems were highly effective against gram-negative organisms, with resistance rates of 25% in Klebsiella spp., 12.5% in E.coli, 30% in Pseudomonas spp., and 14% in Acinetobacter spp. Colistin remained the most sensitive antibiotic, with no documented resistance among gram-negative organisms. Tigecycline showed low resistance rates, with 14% in Klebsiella spp., 12.5% in E.coli, 8% in Pseudomonas spp., and 9% in Acinetobacter spp.

Our study revealed a concerning resistance profile in Acinetobacter spp., with 14.28% resistance to carbapenems, 85.71% to aminoglycosides, and 9.5% to tigecycline, while colistin showed no resistance. In contrast, Ergul et al ( 9) reported higher resistance rates, with 100% resistance to carbapenems and 90% to aminoglycosides, but no resistance to colistin in Acinetobacter spp. Due to escalating resistance to aminoglycosides and carbapenems in Acinetobacter spp., colistin and tigecycline have emerged as vital treatment alternatives, warranting their inclusion in susceptibility testing ( 19). Our findings, consistent with other studies, indicate colistin as the primary treatment choice  for Acinetobacter infections in our setting. In our study, we observed a significantly higher resistance rate to amikacin ( 53.84%) and gentamicin ( 46.15%) in P. aeruginosa, exceeding the rates reported by Duman Y et al ( 20) ( amikacin resistance: 3-43%, gentamicin : 16-51%) and Ergul et al ( 8)(amikacin resistance: 7.1%, gentamicin : 18.6%).

Even though carbapenems, colistin, and tigecycline have shown high sensitivity against gram-negative organisms, these high end antimicrobials cannot be utilized routinely and should be reserved. Their indiscriminate use poses a significant risk of developing resistance to these drugs as well.

This study revealed that Gram-negative microorganisms were the predominant cause of sepsis in pediatric intensive care unit (PICU), with Acinetobacter species being the most common Gram-negative bacteria and Coagulase negative staphylococcus aureus (CONS) being the most frequent Gram-positive isolate. Linezolid and vancomycin demonstrated high efficacy against Gram-positive microorganisms, while carbapenems, colistin, and tigecycline were the most effective antimicrobials against Gram-negative isolates. The increasing incidence of multi-drug-resistant infections, particularly in intensive care units, is a pressing concern in the medical field. Prior awareness of the causative organisms of bacteremia and sepsis enables us to begin empirical antimicrobials sooner, which can reduce the risk of complications.

Acknowledgements: We greatly appreciate University of Mahatma Gandhi Medical College & Hospital, Jaipur, Rajasthan, India to give ethical clearance for the study. We Would like to thank all staff member and resident doctor for generous help during this study.

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