ISOLATION AND ANTIMICROBIAL SUSCEPTIBILITY PATTERN OF MICROORGANISMS CAUSING INTRA-ABDOMINAL INFECTIONS AT TERTIARY CARE HOSPITAL OF NORTHERN INDIA

Objective: The objective of the study is to find out the resistance pattern of pathogenic organisms isolated from intra-abdominal infection (IAI). Methods: A total of 500 samples were collected from suspected IAIs of patients reporting to the hospital and cultured. Identification of the isolates was done using standard identification protocol. Antimicrobial susceptibility was performed by Kirby-Bauer disc diffusion method and interpretation was done using Central Laboratory Standard Institute guidelines. Results: Out of 500 samples, 170 were culture positive and 330 showed no growth. Gram-negative organisms (n=127) outnumbered the Gram-positive organisms (n=23). Among the Gram-negative organisms, Escherichia coli (n=67) was the most commonly isolated bacilli followed by Klebsiella sp (n=32), Pseudomonas sp . (n=25), Acinetobacter baumannii (n=18), and Klebsiella oxytoca (n=05). Among Gram-positive organisms Staphylococcus aureus (n=17) and Enterococcus spp (n=06) isolates of were grown in culture. Among Gram-negative bacilli, Imipenem followed by Gentamicin was the most effective drug but in Acinetobacter spp . The second most effective drug was Tigecycline. Among Gram-positive isolates, Linezolid was the most effective drug. Conclusion: Prompt starting of empirical antimicrobials based on the local susceptibility pattern, followed by modification of treatment in accordance with the antimicrobial susceptibility report can significantly reduce the morbidity and the mortality associated with IAIs.


INTRODUCTION
Intra-abdominal infections (IAI's) are associated with significant morbidity and mortality and common cause of hospitalized patients [1]. IAIs is a wide term that encompasses a number of infectious processes which include peritonitis, diverticulitis, cholecystitis, cholangitis, pancreatitis, chronic liver failure, and intestinal perforation [2]. According to the Infectious Diseases Society of America, complicated IAIs is defined as an infection that extends beyond the wall of a hollow viscous of source into the abdominal cavity while being related with an abscess or peritonitis [3]. Etiology of the organism responsible for the IAI can be conditional, based on the location of the organ originally infected, since the residential Gastrointestinal flora is typically the cause in the IAIs. For example, infections occurring in the stomach and proximal small intestine mostly involve Gram-positive organisms, whereas those in the distal small intestine involve more Gram-negative aerobic and facultative anaerobic bacilli. Even more distally, infections in the colon consist mainly of obligate anaerobic organisms [3,4]. Management of IAIs requires the involvement of multiple modalities such as surgeries as well as treatment with antimicrobials [5]. Hospitalacquired IAIs are associated with higher mortality rates because of compromised patient's immunity due to underlying illness and infections with multidrug-resistant organisms [1]. Antimicrobial management plays a vital role in critically ill patients with IAIs as selection of wrong antimicrobial can cause therapeutically failure which can lead to further mortality rate [6]. Initially, empirical therapy should be started based on the most frequently isolated organism and local pattern of antibiotic susceptibility, which should be modified to specific antimicrobials after receiving the microbiology report of antimicrobial susceptibility of the isolated organism [7]. Growing emergence of resistance to multiple drugs and dearth of local data on antimicrobial resistance pattern of IAIs is the cause of concern for the management of IAIs [8]. By keeping in mind the above facts, the present study was planned to determine the resistance pattern of pathogenic organisms isolated from IAIs.

METHODS
The present study was conducted for the duration of 2 years, i.e., 2018-2020 to determine the bacteriological profile and antimicrobial susceptibility pattern of isolates from the samples received from IAIs in the department of Microbiology, MMIMSR, Mullana, Ambala, Haryana, India. Ethical clearance for the study was taken from Institutional Ethical Committee.

Processing of samples
A total of 500 samples, like -ascetic fluid, bile, pus from intraabdominal cavity, were obtained from patients suffering from IAIs such as peritonitis, cholithiasis, appendicitis, pancreatitis, liver abscess. All the samples were cultured on Blood agar and MacConkey agar and incubated at 37°C for 18-24 h and gram staining was performed on each sample. Identification of isolates was done using standard identification protocol (Mackey and McCartney) and other relevant biochemical tests as appropriate for isolates. Antimicrobial susceptibility testing was done by Kirby-Bauer disc diffusion methods and as per Central Laboratory Standard Institute (CLSI), 2018 guidelines [9][10][11].

Antibiotic susceptibility tests
Antimicrobial sensitivity pattern of the isolates was performed using Kirby-Bauer disk diffusion method and interpreted according to guidelines of CLSI. Antimicrobial sensitivity testing for Gram-negative isolates was applied using: a. For Escherichia coli, Klebsiella spp. and Klebsiella oxytoca: Ciprofloxacin ( In addition, Amikacin (30 µg) was also tested against Pseudomonas spp. Additional antibiotics tested against Enterococcus spp. was High-level Gentamicin (120 µg).
Screening for Methicillin-resistance in S. aureus was done using cefoxitin disc as per CLSI guidelines.

RESULTS
Out of 500 samples collected from clinically suspected cases of IAIs, 405 were indoor patients while 95 were outdoor patients ( Table 1). All 500 samples were cultured out of which, 330 showed no growth while growth was obtained in 170 samples. Out of 170 samples, 23 samples showed growth of Gram-positive cocci, in which S. aureus (n=17) were predominant followed by Enterococcus spp. (n=6). Among Gramnegative isolates fermentative bacilli (n=104) were predominant as compared to non-fermentative bacilli (n=43). Out of all fermentative bacilli E. coli was predominant (n=67) followed by Klebsiella spp. (n=32) and K. oxytoca (n=5). In non-fermentative bacilli, Pseudomonas spp.
The most predominant IAIs were Peritonitis and Intestinal perforation in which most isolated organisms were E. coli followed by Klebsiella spp. and Pseudomonas spp. (Table 3).
The Anti-microbial susceptibility testing was also performed in which Imipenem was found to be the most effective drug among all Gram-negative isolates followed by Gentamicin except for Acinetobacter spp. in which the second most effective drug was Tigecycline (Table 4).

DISCUSSION
The emergence of resistance to routinely used antibiotics and even to newer antibiotics has made the treatment of IAIs a real challenge as a result accurate laboratory cultures for identification of organisms and their sensitivity testing has to be done with standard protocols. So that the microbiologists and physicians can go to decrease the mortality rate due to IAIs.

CONCLUSION
The present study emphasizes the need for antimicrobial susceptibility testing of clinically significant isolates from IAIs as a routine practice.
Knowing the prevalent pattern of antimicrobial resistance is an important issue especially when Gram-negative isolates continue to exhibit widespread resistance to various currently in use antimicrobial agents. Prompt starting of empirical antimicrobials based on the local susceptibility pattern, followed by modification of treatment in accordance with the antimicrobial susceptibility report which can significantly reduce the morbidity and the mortality associated with IAIs.

AUTHOR CONTRIBUTION
Concept and design of the study were done by the first, second, and fourth author. Data collection, Data Analysis and manuscript writing were done by first, second, and corresponding author.