Intensive care unit (ICU) is a specialized setting in hospitals, that offers close monitoring and personalized care for the sick patients [1].

Even though ICU represents only 5% of total hospital beds, they account for almost 20-25% of all health care associated infections.2The rate of ICU infections worldwide is 23.7 infections per 1,000 patient days, with the rate of nosocomial infections being 5-30% amongst the ICU patients [3]. 

Patient’s own indigenous flora of the skin, mucous membrane, gastrointestinal tract, or respiratory tract which may invade the patient’s body during surgical or invasive procedures. The exogenous sources are commonly acquired in the ICU by other patients, health care workers, visitors and inanimate objects including patients bed surface, equipments [4].

The profile of organisms causing ICU infections varies widely one country to the other, one hospital to another and even amongst different ICUs of the same hospital [5]. The present study attempts to know the bacteriological profile of bacterial isolates from ICU patients in our institution. This study aims to improve patient’s outcome and infection control practices in the hospital.

Aims and Objectives

To identify the bacteriological profile of bacterial isolates in the samples received from different intensive care units (HDU, GICU, CTVS-ICU, PICU, RICU, NICU, SNCU

• Study Setting: The present study was conducted in the department of Microbiology, Indira Gandhi Medical College and Hospital Shimla

• Study Design: It was a descriptive cross sectional study

• Study period: The study period was of one year from 14^th January 2019 to 13^th January 2020

• Selection of cases: In this study all clinical samples received in the department of Microbiology for bacterial culture and susceptibility testing from patients admitted in the intensive care units of this institution during the study period

Samples received in the department of Microbiology and processed using standard procedures were of Bloodm,Sterile Body fluids (cerebrospinal fluid and pleural fluid), Pus samples, Sputum,Swabs (throat and wound) ,Respiratory secretions,Urine and Central line catheter tip.

The demographic profile of the patient whose samples were included in the study was also recorded.

Processing of Samples

The samples of blood and other sterile body fluids received in BACTEC blood culture vials were first cultured using the BD BACTEC™ FX system for five days. The positive blood culture vials were further processed within 8hrs. For obtaining pure growth for further processing, the positive blood culture vials were inoculated on blood agar and MacConkey agar plates and incubated aerobically at 37^oC overnight for 18-24 hrs. The positive cultures detected in the BD BACTEC™ FX system were subjected to identification and antibiotic susceptibility testing by BD Phoenix™ FX Automated Microbiology system. Negative report was given only after 5days of incubation in BD BACTEC ™ FX automated system.

Body fluid such as pus, sputum, respiratory secretions, pleural fluid were received in sterile containers, inoculated onto blood agar and MacConkey agar plates, and were incubated at 37^o C for 24 hrs. Cerebrospinal fluid was received in sterile container and inoculated on blood agar and chocolate agar plates and incubated at 37⁰ C for 24 hrs.Uncentrifuged urine but well-mixed urine was inoculated by a calibrated loop onto plates of cystine lactose electrolyte deficient (CLED) agar. Throat swab was inoculated onto blood agar plates and incubated at 37⁰ C for 24 hrs.

Morphology and Characteristics

The pure growth obtained after 24 hours of incubation on solid media was identified on the basis of colony characters, gram staining and preliminary biochemical reactions. When pure growth is not obtained on primary plating then it was subcultured on blood agar and MacConkey agar to get pure growth.

Preliminary Identification of Bacteria

• Colony characters: The growth of the organism was observed on Blood Agar and MacConkey Agar. The characters of the colony were studied like size, shape, surface, edge, elevation, consistency, colour of the colony, odour, and effect on media

• Gram Staining: Gram staining of the growth was done using modified Huckers method. Based on the gram staining of organism whether gram positive or gram negative, the panels for antimicrobial sensitivity were selected

• Preliminary Biochemical Reactions: Preliminary biochemical reactions such as catalase, coagulase and oxidase were performed to identify the organism.

The isolates were then processed in BD Phoenix™ FX automated system for further identification. The final report indicating organism identified was communicated to respective ICUs and also recorded in the performa

Quality Control

The quality check was performed using standard strains as per the manufacturer’s instructions.

Exclusion Criteria

The samples where BD Phoenix™ FX automated system gave inconclusive results or failed to identify the isolates were excluded from the study.

Statistical Analysis

The Data collected was entered in Excel spreadsheet and accuracy of data entered was checked by cross-verification of the data entered. Categorical variables were expressed as frequencies and percentages.

The present study was conducted in the department of Microbiology Indira Gandhi Medical College and Hospital where in the clinical samples received from various intensive care units were analysed for bacteriological profile and antibiotic susceptibility pattern. The duration of the study was from 14^th January 2019 to 13^th January 2020. The observations were as follows.

The clinical samples were received from general ICU, neonatal ICU, paediatric ICU, HDU, respiratory ICU, sick neonatal care unit and CTVS-ICU. The bacterial isolates were studied in detail in the present study and Candida spp. was also documented. In the present study 2458 samples were processed out of which 766 (31.16%) were found to be culture positive, sterile were 1463 (59.52%) and contaminants were found in 229 (9.32%) Figure 1. 

Figure 1: Culture Positivity among Clinical Samples

The number of isolates in all culture positive specimens was 840, as more than one isolates were also obtained in some specimens.

Among all isolates gram negative bacteria were most common, followed by Candida spp. and gram positive bacteria.

In the present study positivity rate was maximum from general ICU 58.36% followed by sick neonatal care unit 25.06% and lowest positivity rate was seen from respiratory ICU 16.66% Table 1-3.

Table 1: Distribution of Clinical Specimens from Different ICUs

Table 2: Pattern of Organisms Isolated In All Clinical Specimens

Table 3: Distribution of Isolates from Different ICU

The percentage of gram negative bacteria were maximum from HDU (80%), gram positive bacteria were found to be maximum from CTVS-ICU (27.27%) and Candida were maximum from pediatric ICUs (83.08%). In pediatric ICUs highest percentage of Candida spp. were isolated from NICU (64.28%) followed by PICU (60.14%) and SNCU (60%).

The age and sex wise distribution as categorized into various groups is depicted in Table 4-5.

In the present study, from GICU Klebsiella pneumoniae was the most common isolate followed by Non fermenter group of organism. Klebsiella pneumoniae was also the commonest isolate from HDU, SNCU and NICU. Whereas Non fermenter group of organism was common in RICU and CTVS ICU. In PICU Escherichia coli was the most common isolate.

Table 4: Age Sex Distribution of Patients with Positive Culture

Table 5: ICU Wise Distribution of Clinical Isolates

Infection is a major factor that determines the clinical outcome among patients requiring intensive care unit (ICU) support. The causes of infection within an ICU are multi‑factorial. The consequences depend upon the source involved, organisms associated, underlying morbidity, timeliness and appropriateness of the treatment and the intervention received [6].In the present study Eight hundred and forty (840) bacterial and Candida isolates were reported in this study form various clinical specimens that were received and processed as routine in the department of Microbiology.

The demographic profile of the ICU patients in the present study revealed that the number of males admitted in different ICUs were greater than females, (male: female ratio being 1.67:1). Which is similar to that reported by Iwuafor A.et al. Sarvepalli A. et al. and Turtkan M. et al. [7-9]. The reason for male predominance in this study could be due to more health seeking behaviour of males.

In the present study the overall culture positivity was found to be 31.16%. This was found to be similar to a study conducted by Patil P. et al. [1] The positivity rate was found to be more than that reported by Chelazzi et al. (9.3%) and Nangino et al. (8.9%) [10-11]. The positivity rate was less than that reported by Vincent J.et al. (51%) and Babbar P. et al. 44.8% [12-13]. The probable reason for the lower culture positivity rate in the present study can be due to prior use of antibiotics, improper sample collection and transportation and the samples were also not processed for anaerobic bacteria and filamentous fungi.

Majority of the pathogens causing infections in the patients admitted to the ICUs in the present study, were gram negative bacteria (56.66%) followed by gram positive bacteria (11.42%). The results from this study are similar to few recent studies where gram negative bacteria were most commonly isolated [12,14,15]. However according to global studies gram positive bacteria were found to be more compared to gram negative bacteria [16-18]. This predominance of gram negative bacteria in the present study can be explained by the fact that the prevalence of gram negative bacteria is higher in developing countries as compared to developed countries [2]. 

In the present study maximum number of samples were obtained from SNCU, but the overall culture positivity was found to be maximum from GICU (58.36%). Similar results were seen in the studies conducted by Patil P. et al. [1] and Jawady A. et al. [15]. In contrary to the present study Gupta S. et al. and Mahaluca A. et al. documented maximum positivity rate from NICU and PICU [16,19]. The culture positivity rate with respect to different ICUs is variable in different studies across the country and the world. 

In the present study gram negative bacteria were found to be maximum from HDU (80%), gram positive bacteria were maximum from CTVS-ICU (27.27%) and Candida were maximum in NICU (64.28%). The predominant gram negative bacteria isolated were Klebsiella pneumoniae and Non fermenter group of organism followed by Candida spp. and gram positive bacteria such as Staphylococcus aureus and coagulase negative Staphylococcus. The findings are in consistent with other studies from India such as by Sahu et al. Patil P.et al. and Pattanayak C. et al. and Jawady A. et al. [1,15,20,21]. Several studies from other parts of the world show predominance of gram positive bacteria from ICUs [7,16,18]. The predominance of gram negative bacteria may be due to their wide prevalence in the hospital environment, and most of them represent a wide range of normal flora. 

The most common bacteria isolated in the present study were Klebsiella pneumoniae followed by Non fermenter group of organism. Klebsiella pneumoniae was also found to be the most common isolate from blood, endotracheal secretions, pus and drain. Whereas in urine Enterococcus faecium and Escherichia coli were found to be predominant isolates. Klebsiella pneumoniae was also found to be predominant isolate from ICU infections in several other studies [22-24]. Unlike the present study Pradhan et al. found Acinetobacter baumannii as predominant pathogen from endotracheal secretions and Pseudomonas spp. from urine. Richards M. et al. found CONS as predominant isolate from blood, Pseudomonas aeruginosa from respiratory secretions, Escherichia coli from urine and Pseudomonas aeruginosa from pus. Jain et al. found Citrobacter koseri from blood, Escherichia coli from urine, Pseudomonas aeruginosa from sputum and Staphylococcus aureus from pus [25-26]. Klebsiella pneumoniae was found to be predominant isolate in this study this can probably be explained by the fact that the members of Enterobacteriaceae are found as normal commensal flora of human body, which make them one of the most important endogenous bacteria causing infections in immune-compromised patients. Increased colonization of Enterobacteriaceae organisms in the respiratory tract of patients on prolonged mechanical ventilation also contributes to higher infections due to these bacterias in ICUs [27].

Non fermenter gram negative bacteria have emerged as important pathogen in the hospitals particularly in ICUs, probably due to wide spread and injudicious use of antibiotics. These bacteria are normally inhabitants of water and soil. In the hospital environment they may be isolated from instruments, hospital linen and also from skin. Most of these are MDR pathogen. Hence pose a challenge to the treating physician. In the present study Non fermenter gram negative bacteria were next common group isolated from several clinical specimens. They were increasingly reported from endotracheal secretions. Pseudomonas and Acinetobacter baumannii were predominant Non fermenter bacteria isolated from endotracheal secretions. Pseudomonas and Acinetobacter baumannii are reported as predominant isolates from various ICUs in literature [28-29].

Multidrug resistant bacteria are a growing problem in the intensive care units which is leaving the clinicians with only fewer options to treat critically ill patients. The increasing multidrug resistant pathogens and the immunocompromised nature of the patients lead to increased mortality and morbidity in the ICUs and also the cost of treatment worldwide. 

Present study covers all the samples received from different ICUs in our institution and provide an insight in to early initiation of antimicrobial therapy and influence the outcome of patients admitted to these ICUs. A periodic surveillance of the ICUs is thus essential as many of the pathogens are not incubating in the patient at the time of admission but are transmitted by the hands of the treating physicians and other inanimate objects that are used during invasive procedures.

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