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Year : 2022  |  Volume : 15  |  Issue : 3  |  Page : 440-443  

Microbiological profile and antibiotic susceptibility pattern of gram-negative isolates from tracheal secretions in a tertiary care setup

Department of Microbiology, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pune, Maharashtra, India

Date of Submission30-Nov-2020
Date of Decision13-Dec-2021
Date of Acceptance20-Jan-2022
Date of Web Publication11-Mar-2022

Correspondence Address:
Shahzad Mirza
Department of Microbiology, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pune - 411 018, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/mjdrdypu.mjdrdypu_679_20

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Among intensive care unit patients, lower respiratory tract infections (LRTI) are one of the most common infections to occur. The aim of this study was to determine the microbiological profile and antibiogram of pathogens isolated from tracheal secretions. Place of study. Dr. D. Y. Patil Medical college; Type of study - Retrospective study and cross-sectional study; Study period- April 2020 to September 2020 (6 months).152 isolates from non-repeated samples received for culture and sensitivity were considered for the study. Sample -Tracheal secretions. The sample was processed on blood and MacConkey's agar, identification done by standard biochemical tests, and antibiotic sensitivity was performed by disk diffusion (Kirby-Bauer test) method on Muller Hinton agar According to CLSI 2020 guidelines. Total- 152 tracheal aspirates; Positive samples- 148. The most commonly reported among the isolates was Klebsiella pneumoniae 51, (64.7%) followed by Acinetobacter Spp 45(30.40%) and Pseudomonas 37(25%). Alarming rate of resistance was seen in gram-negative isolates in tracheal secretions to carbapenems but good sensitivity was seen in tigecycline and colistin both. So, with a lack of new antibiotics, the current scenario presents a major threat in dealing with these pathogens in the future.

Keywords: Intensive care unit, Lower Respiratory Tract Infection (LRTI), Ventilator associated pneumonia(VAP)

How to cite this article:
Bhaumik S, Das NK, Gandham NR, Mirza S, Rabindra N M, Gupta NS, Mukhida SS, Kannuri S. Microbiological profile and antibiotic susceptibility pattern of gram-negative isolates from tracheal secretions in a tertiary care setup. Med J DY Patil Vidyapeeth 2022;15:440-3

How to cite this URL:
Bhaumik S, Das NK, Gandham NR, Mirza S, Rabindra N M, Gupta NS, Mukhida SS, Kannuri S. Microbiological profile and antibiotic susceptibility pattern of gram-negative isolates from tracheal secretions in a tertiary care setup. Med J DY Patil Vidyapeeth [serial online] 2022 [cited 2022 Nov 29];15:440-3. Available from: https://www.mjdrdypv.org/text.asp?2022/15/3/440/339400

  Introduction Top

Pneumonia accounts for more than 60% of the infections diagnosed in the intensive care unit (ICU) patients worldwide. Ventilator-associated pneumonia (VAP) is at the forefront of nosocomial infections in the ICU and affects 10%–20% of patients under mechanical ventilation (MV) for more than 48 h. It is defined as pneumonia occurring more than 48 h after patients have been intubated and received MV. Diagnosing VAP requires a high clinical suspicion combined with bedside examination, radiographic examination, and microbiologic analysis of respiratory secretions.

Criteria provided by Center for Disease Control recommend three methods for diagnosing VAP which are bronchoalveolar lavage, lung biopsy, and tracheal aspirate. Of the three, tracheal aspirate specimens are easier and potentially safer to collect, but they have low diagnostic specificity for VAP and rarely distinguish between colonization and infection.[1]

Distinguishing colonization from infection is an important factor in making the correct diagnosis in a wide variety of pediatric conditions. Colonization indicates that the patient has a sufficiently high concentration of organisms at a site that they can be detected, yet the organism is causing no signs or symptoms in that patient. This differs from contamination, where the organism was never present in the site from which it has been detected, but was introduced into the specimen from another site or from contamination in the laboratory. A carrier is a person who is colonized with an organism and may transmit the organism to other people. Colonization can persist for days to years, with resolution influenced by the immune response to the organism, competition at the site from other organisms, and sometimes, use of antimicrobials.[2] The aim of this study was to identify the common pathogens in tracheal secretions and to study the patterns of their sensitivity and resistance to various antibiotics, which can serve as guidelines to physicians for empirical treatment with proper antibiotics.

  Materials and Methods Top

This is a retrospective, observational, and cross-sectional study conducted at a tertiary care center, Pimpri, Pune. The study included data from April 2020 to September 2020.

Ethical clearance was obtained from the institutional ethics subcommittee and the approval number will be provided soon.

All the tracheal secretions received in the department of microbiology from various ICUs such as surgical ICU, medicine ICU, and respiratory ICU and from critical care medicine were included in the study. The samples included protected specimen brush, lung biopsy, Endotracheal secretions (ET) secretions, and ET tip culture. All the specimens received were processed immediately without delay.

The sample was processed for microscopy, where Gram staining was done from the mucopurulent part of the specimen. The diagnosis of VAP was made if the Gram staining demonstrates the higher number of bacteria, intracellular bacteria, or presence of fibrin strands. Organisms on Gram staining and fewer than ten squamous epithelial cells per low-power field (magnification ×100) are followed. Furthermore, the number of polymorphonuclear leukocytes is not predictive of an interpretable specimen in patients with VAP. Then, the sample was processed on blood and MacConkey agar and was incubated at 37°C for 24–48 h; quantitative culture was considered significant if the colony count exceeded >/105 CFU/ml for endotracheal aspirates. Identification was done by standard biochemical tests and antibiotic sensitivity was performed by disk-diffusion (Kirby–Bauer test) method on Mueller–Hinton agar according to CLSI 2020 guidelines.[3],[4]

Clinical pulmonary infection score (CPIS) system is a scoring system based on six parameters such as clinical, radiological, and microbiological, with each parameter given a score scale ranging from 0 to 2. The maximum score that can be obtained is 12, and a score >6 is diagnostic of VAP. CPIS score is prone to significant interobserver variability, mainly in the interpretation of the tracheal secretions and the chest X-ray.[5]

  Results Top

During the period of 6 months, in our study, 152 isolates from nonrepeated samples received for culture and sensitivity were considered. We have seen that of 152 tracheal aspirates, 148 tested positive. Among 148 patients, 37 females (25%) and 111 males (75%) showed growth in cultures. Positive growth was observed in 148 (97.36%) samples. The Gram-negative bacilli contributed a major number of isolates (147; 99%), the remaining one (1%) was caused by Gram-positive cocci. Out of the bacteria isolated from positive growth cultures, the most common reported among the isolates was Klebsiella pneumoniae 51, (34.7%), followed by Acinetobacter spp. 45, (30.7%). There were 37 cases of Pseudomonas aeruginosa (25%), four cases of  Escherichia More Details coli (2.70%), and the other organisms were Proteus mirabilis (1), Citrobacter freundii (1), Citrobacter koseri (1), Enterobacter spp. (2), and Gram-negative nonfermenter (1) [Figure 1].
Figure 1: Percentage distribution of the isolates from tracheal secretions

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A study by Ahmad et al. showed that more of the isolates from the patients were Gram-negative enteric aerobic bacteria, with Klebsiella being the most common species, followed by Acinetobacter and Pseudomonas.[6]

Klebsiella was most sensitive to tigecycline (94.7%). Majority of the organisms reported were multidrug resistant (MDR) strains which were resistant to cephalosporins, aminoglycosides, and carbapenems too [Table 1].
Table 1: Antibiotic sensitivity pattern of Gram-negative bacilli in tracheal secretions

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These MDR and extensively drug-resistant (XDR) pathogens increase morbidity and mortality in patients making treatment difficult and extensive.

  Discussion Top

The resistance to conventional antibiotics is severely increasing in bacteria in clinical setups. The rate of nosocomial infection is increasing day by day in the patients admitted in the ICU due to excessive invasive procedures. This constantly emerging resistance is a serious situation suggesting the need for new regulations for the judicious use of antibiotics and purifying the conditions of hospitals to prevent further exacerbation of resistance shown by the bacteria.

The percentage of samples showing positive growth in our study was 97.36%. In another study by Chandra et al., the positive samples were 72.3%.[7] In a study conducted by Gupta et al., the percentage of positive growth was 53%.[8] In a study conducted in the setting of Pakistan by Malik et al., the positive cultures came out to be 83%.[9] In our study, Gram-negative bacilli were more common causative agents (99%) as compared to Gram-positive cocci, which were 1% of the total positive cultures. A study by Deepti et al. showed that more of the isolates from the patients were Gram-negative enteric aerobic bacteria, with Klebsiella being the most common species, followed by Acinetobacter and Pseudomonas.[7] This can be attributed to the fact that the majority of the nosocomial infections are caused by Gram-negative bacteria which are more dangerous and difficult to treat. This calls for strict measures against the spread of Gram-negative bacilli, especially in the ICU setting.

In our study, Klebsiella (64.7%) was the most common isolate. In one study by George et al., Acinetobacter was the most common isolate (37.5%), followed by Pseudomonas (21.8%) and Klebsiella (15.6%).[10] The rise in Klebsiella in our study, especially in the ICU setup, can be attributed to the dramatic increase in the occurrence of MDR isolates. In addition, this organism has the ability to survive in humid and dry conditions as well as at extreme cold for longer periods, indicating its surviving ability in temperate and tropical temperatures resulting in nosocomial outbreaks.

The second most common isolate in our study was Acinetobacter (30.40%). In a study conducted by Malik et al., in Pakistan, the most common bacterium isolated from tracheal secretions was K. pneumoniae (35.4%).[9] Another study by Chandra et al. showed Klebsiella (32.35%) to be the most common isolate. Pseudomonas (25%) was the third-most common isolate present in our study.[7]

In our study, Klebsiella and Acinetobacter were both most sensitive to tigecycline (94.7%). In a study by Anusha et al., Acinetobacter was most sensitive to imipenem and ciprofloxacin.[11] Pseudomonas was shown to be 94.59% sensitive to tigecycline. Both Klebsiella and Pseudomonas showed a gradual decrease in the sensitivity to drugs. These Gram-negative bacteria have developed resistance to multiple drugs which can be associated with cross infections and other factors such as the misuse of antibiotics.

The other Gram-negative bacilli of our study included E. coli, P. mirabilis, C. freundii, C. koseri, and Gram-negative nonfermenter which were sensitive to amikacin (80%) and imipenem (100%). E. coli, in a study by Anusha et al., showed sensitivity to both amikacin and imipenem.[9] This was consistent with a similar study by Gupta et al., which showed no change in antimicrobial resistance pattern.[7] The resistance patterns of bacteria in our study showed Klebsiella and Acinetobacter to be 100% resistant to ceftriaxone, ciprofloxacin, amoxicillin, and clavulanic acid. In the research by Gupta et al., Acinetobacter showed resistance to cephalosporins and aminoglycosides.[7] This depicted a pattern of increasing resistance to the drugs. In our study, of all the Gram-negative bacilli, Acinetobacter showed increasing resistance to carbapenems. This is an alarming situation as the emergence of MDR and XDR pathogens in tracheal secretions is increasing morbidity and mortality in patients, making treatment difficult and very expensive.[8]

  Conclusion Top

The alarming rate of resistance was seen in Gram-negative isolates in tracheal secretions to carbapenems, but good sensitivity was seen in both tigecycline and colistin. Hence, with the lack of new antibiotics, the current scenario presents a major threat in dealing with these pathogens in future. Upsurge in MDR Gram-negative organisms such as K. pneumoniae and Acinetobacter spp. warrants for judicial use of antibiotics in hospital-acquired infection.

Antibiotic administration should be promptly initiated when VAP is suspected, and quantitative cultures obtained should be broad in coverage. Knowledge of local antibiograms should guide the choice of antibiotics. For patients already on antibiotics at the time of suspected VAP, the clinician should choose antibiotics from different classes, as it is likely that resistance to “in-use” antibiotics has developed.

Assessment of the likelihood of VAP by day 3 is needed to decide whether antibiotics should be continued. The assessment should include a repeat CPIS, as the change in CPIS can guide clinical decisions, even stoppage of antibiotics. Assessment of quantitative culture results and sensitivities at this juncture is prudent, as it may permit early antibiotic de-escalation by choosing a narrower focused agent. Monotherapy may be suitable in many instances of VAP and should reduce the incidence of drug resistance. A change to monotherapy may be possible in a responding patient where organism sensitivity results permit. A short course can be administered to patients with VAP but is dependent on the patient's physiological response to treatment, along with which organisms have been recovered.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Dray S, Coiffard B, Persico N, Papazian L, Hraiech S. Are tracheal surveillance cultures useful in the intensive care unit? Ann Transl Med 2018;6:421.  Back to cited text no. 1
Robinson J. Colonization and infection of the respiratory tract: What do we know? Paediatr Child Health 2004;9:21-4.  Back to cited text no. 2
Mackie TJ. Mackie and McCartney practical medical microbiology. Harcourt Health Sciences 2020.  Back to cited text no. 3
CLSI (2020). Performance Standards for Antimicrobial Susceptibility Testing, Twenty-Fifth Informational Supplement in M100-S30. Wayne, PA: Clinical and Laboratory Standards Institute.  Back to cited text no. 4
Sastry AS, Bhat S. Essentials of Medical Microbiology. New Delhi, India Jaypee Brothers, Medical Publishers Pvt. Limited; 2018.  Back to cited text no. 5
Ahmad H, Sadiq A, Bhatti HW, Bhatti AA, Tameez-Ud-Din A, Ibrahim A, et al. Bacteriological profile and antibiogram of cultures isolated from tracheal secretions. Cureus 2019;11:e4965.  Back to cited text no. 6
Chandra D, Laghawe A, Sadawarte K. Microbiological profile and antimicrobial sensitivity pattern of endotracheal tube aspirates of patients in ICU of a tertiary care hospital in Bhopal, India. Int J Curr Microbiol App Sci 2017;6:891-5.  Back to cited text no. 7
Gupta P, Gupta S, Singh JB. Bacteriological profile and the antibiotic susceptibility pattern of endotracheal secretions In the ICU of a tertiary care hospital. J Evol Med Dent Sci 2018;7:2210-3.  Back to cited text no. 8
Malik MI. Pattern of bacterial pathogens isolated from endotracheal secretions in Intensive Care Unit (ICU) patients of a tertiary care hospital of Lahore. Sajjad 2018;29:46-8.  Back to cited text no. 9
George P, Sequiera A. Antimicrobial sensitivity pattern among organisms which were isolated from the endotracheal aspirates of patients with ventilator associated pneumonia. J Clin Diagn Res 2010;4:3397-401  Back to cited text no. 10
Anusha N, Madhu KP, Arun BJ, Vidyasagar B. Microbiological profile and sensitivity pattern of endotracheal secretions in mechanically ventilated patients in the ICU. J Evid Based Health 2014;1:1177-84.  Back to cited text no. 11


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