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 Table of Contents  
Year : 2020  |  Volume : 6  |  Issue : 1  |  Page : 50-53

Multi-drug resistant gram-negative bacilli in lower respiratory tract infections at IGIMS, Patna: A tertiary care hospital

1 Junior resident, IGIMS, India
2 Professor, IGIMS, India
3 Assistant Professor, IGIMS, India
4 Professor and Head, Dept. of Microbiology, IGIMS, India

Date of Submission09-Jan-2020
Date of Acceptance17-Jan-2020
Date of Web Publication12-Feb-2020

Correspondence Address:
Namrata Kumari
Professor, Dept. of Microbiology, IGIMS, Patna
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Source of Support: None, Conflict of Interest: None

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Background: Lower respiratory tract infections are among important causes of morbidity and mortality for all age groups. The emergence of multidrug resistant gram-negative organism (MDRO) is an issue of increasing concern.
Aims & Objectives: This study was focused on obtaining a comprehensive insight into the microbial profile, its prevalence and the susceptibility patterns of the gram negative bacilli isolates including multi drug resistance in lower respiratory tract infections.
Materials and Methods: A total of 1144 respiratory samples (sputum, broncho-alveolar lavage fluid and endotracheal aspirate) were processed for microscopy, culture and susceptibility testing following standard laboratory protocols. Multidrug resistant gram-negative bacilli causing lower respiratory tract infections were studied for their causation of disease.
Results: A total of 349 gram-negative pathogens were isolated from respiratory samples during the study period. Among these 213 (61%) gram-negative pathogens were found to be multidrug resistant. Although the percentage of multi drug resistance was higher among Escherichia coli (88% MDRO) and Acinetobacter spp. (80% MDRO), the predominant multidrug resistant gram-negative bacilli isolated were Klebsiella spp. 119 (34%) and Pseudomonas spp. 108 (30%). Among MDROs, other isolates were Citrobacter spp., Enerobacter spp., Proteus spp. and Providentia spp.
Conclusion: A large majority of pathogenic gram-negative bacilli isolated were found to be the multidrug resistant. Regular surveillance which directs appropriate empirical therapy and good clinico-microbiological workup of each case of lower respiratory tract infection can reduce the morbidity and mortality associated with MDROs. Bacteriological diagnosis and antibiotic resistance surveillance are indispensible in the effective management of lower respiratory tract infections.

Keywords: Multidrug resistance gram-negative bacilli, lower respiratory tract infection, IGIMS, tertiary care hospital

How to cite this article:
Azad MS, Kumari N, Sinha R, Saurabh K, Shahi SK. Multi-drug resistant gram-negative bacilli in lower respiratory tract infections at IGIMS, Patna: A tertiary care hospital. J Indira Gandhi Inst Med Sci 2020;6:50-3

How to cite this URL:
Azad MS, Kumari N, Sinha R, Saurabh K, Shahi SK. Multi-drug resistant gram-negative bacilli in lower respiratory tract infections at IGIMS, Patna: A tertiary care hospital. J Indira Gandhi Inst Med Sci [serial online] 2020 [cited 2023 Mar 24];6:50-3. Available from: http://www.jigims.co.in/text.asp?2020/6/1/50/300740

  Introduction Top

Respiratory tract infections are some of the most common causes of human illness and the leading cause of death from infectious diseases worldwide.[1] Lower respiratory tract infections are acute illness (present for 21 days or less), usually with cough as the main symptom, accompanied by other lower respiratory tract symptom (sputum production, dyspnoea, wheeze or chest discomfort/pain) and no alternative explanation (e.g. sinusitis or asthma). Lower respiratory tract infection (LRTI) is a broad description of a group of disease entities, encompassing acute bronchitis, pneumonia and exacerbations of chronic lung disease.[2]

Community-acquired pneumonia (CAP), nosocomial pneumonia and acute and chronic bronchial infections in patients with chronic obstructive pulmonary disease (COPD) and bronchiectasis are among the common respiratory infections. A large proportion of gram-negative bacteria (GNB) are the causative pathogens of these lower respiratory tract infections. Several studies have reported an increased rate of GNB as causal agents in recent years, especially in hospital-acquired infections and also in patients coming from the community.[3]

The main problem concerning the treatment of gram- negative bacterial infections is their related antibiotic resistance, reported as multidrug resistant (MDR), extensively drug resistant (XDR) and pan-drug resistant (PDR). Different definitions for MDR bacteria have being used in the literature. The European Centre for Disease Prevention and Control (ECDC) and the Centres for Disease Control and Prevention (CDC) joined in 2011 to standardize the terminology used to describe acquired resistant profiles in Staphylococcus aureus, Enterococcus spp., Enterobacteriaceae (other than Salmonella and Shigella), P. aeruginosa and Acinetobacter spp., all related to healthcare-associated infections. In the definitions proposed, non-susceptibility refers to either, resistant or intermediate result from in vitro antimicrobial susceptibility test. MDR was defined as non-susceptibility to at least one agent in three or more antimicrobial categories. In addition, extensively drug resistant (XDR) was defined as non-susceptibility to at least one agent in all but two or fewer antimicrobial categories and pan-drug resistance (PDR) as non-susceptibility to all agents in all antimicrobial categories.[4]

The most frequent MDR or potentially drug?resistant GNB isolated in respiratory infections are Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii, Stenotrophomonas maltophilia and other Enterobacteriaceae spp.[5]

P. aeruginosa is a versatile microorganism that is the leading cause of opportunistic human infections.[6] Treatment failure due to the development of resistance is indeed a frequent outcome in patients suffering from P. aeruginosa infections. Due to its ability to induce changes in genes, it generates mutants that are resistant to clinical concentrations of all antimicrobial agents used for therapy.[7] Another important feature is its capacity to produce biofilms to evade antibiotic effect. Biofilms are communities of bacteria attached to a surface, expressing different properties from planktonic cells as an increased resistance to antimicrobial therapy and host defence.[8]

P. aeruginosa is responsible for severe nosocomial infections, especially in the intensive care units (ICU). ' However, it has also been described in patients with pneumonia coming from the community[11] and it is well recognized as a major cause of chronic respiratory infections in patients with bronchiectasis and COPD.[12],[13]

Escherichia coli, Klebsiella pneumoniae and other Enterobacteriaceae spp. are responsible for different respiratory infections acquired in the hospital setting, although some studies have also reported the presence of these GNB in non-nosocomial infections.[3] They have the property of acquiring resistance to different antibiotic resulting in treatment failures. They are also capable to produce extended-spectrum χ-lactamases (ESBL), including carbapenemases that can hydrolyse most ??lactams, including the carbapenems.[14],[15]

Acinetobacter baumannii is an opportunistic pathogen that is frequently involved in outbreaks of infection, occurring mostly in the ICU. A. baumannii have been described as a cause of respiratory infections following hospitalization in patients with severe illness. MDR isolates of A. baumannii have been reported increasingly during the last years, especially against carbapenems, and have been related to poor clinical outcomes.[16]

The emergence of GNB antibiotic resistance and the lack of novel antibiotics in the development pipeline represent one of the biggest respiratory threats in the recent years. Hence this study was planned to identify MDR gram- negative bacilli causing LRTIs, to correlated their isolation with the causation of disease and to study the antimicrobial susceptibility profile of MDR GNB.

  Materials & Methods Top

This prospective study was conducted for a period of one year from October 2018 to September 2019 at IGIMS Patna, a tertiary care hospital. A total of 1144 respiratory samples (sputum, broncho-alveolar lavage fluid and endotracheal aspirate) from both out-patient and inpatient suspected of LRTI were processed for microscopy, culture and susceptibility testing following standard laboratory protocols.

The quality of specimens was evaluated based on Gram stain findings, followed by culture and susceptibility testing. All sputum gram stains were read under oil immersion objective (x100) and evaluated according to the Bartlett criteria. Specimens were scored 0, +1, or +2 according to the number of leukocytes seen per field and 0, -1, and -2 according to the number of squamous epithelial cells seen per field. Specimens with total scores of zero or less were considered inadequate and heavily contaminated with oropharyngeal flora. Those containing greater than 25 leucocytes and fewer than 10 squamous epithelial cells per field were optimal specimens and further processed.[17]

Samples were subjected to gram’s staining and then sub- cultured onto 5% sheep blood agar, chocolate agar and MacConkey agar plates and incubated. Biochemical tests were performed on culture isolates following standard laboratory protocols. Gram negative bacilli were identified by performing various biochemical tests.[18]

Antibiotic sensitivity testing was performed on Mueller Hinton agar (MHA) plates by modified Kirby Bauer disk diffusion method as per Clinical Laboratory Standard Institute (CLSI) guidelines 2016.[19]

For quality control, E. coli ATCC 25922, P. aeruginosa ATCC 27853 and K. pneumoniae ATCC 700603 were used. MDR gram-negative bacilli were defined as isolates showing resistance to at least 3 different antimicrobial groups.4 Clinically isolates were considered pathogenic if there was presence of fever (temperature >38°C), raised leucocyte count (>12.0 x 109 cells/L), presence of purulent sputum, positive chest auscultatory findings and radiological findings of chest infection.

Statistical Analysis: Data analysis was done using Statistical Package for Social Sciences (SPSS) software version 25.0. The level of significance for tests was set at P < 0.05. Microsoft excel were used for totaling, percentage and frequency.

  Results Top

A total of 349 gram-negative pathogens were isolated from 1144 respiratory samples [sputum (n= 932), broncho- alveolar lavage fluid (n= 119) and endotracheal aspirates (n= 93)]. 233 GNB pathogens were isolated from sputum samples, 44 GNB pathogens from broncho-alveolar lavage (BAL) fluid and 72 that from endotracheal aspirates (ETA). Mixed GNB pathogens were isolated predominantly from ETA samples from the patients on ventilatory life support in ICU. Klebsiella spp. 119 (34%) was the most common gram- negative bacilli (GNB) followed by Pseudomonas spp. 108 (31%), Acinetobacter spp. 51 (14.6%) and Escherichia coli 51 (14.6%). Other GNB isolates were Citrobacer spp. 9 (2.6%), Enterobacter spp. 6 (1.7%) and Proteus spp. 4 (1.14). Providentia spp. isolated was only one in number.[Figure 1]
Figure 1: Frequency of different GNB isolates

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Among these gram-negative pathogens, 213 (61%) GNB were found to be multidrug resistant. [Figure 2]
Figure 2: Percentage of MDROs among GNB isolates

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Escherichia coli 45 (88%) and Acinetobacter spp. 41 (80.4%) were the predominant MDROs. [Figure 3]
Figure 3: Preparation of MDR among GNB pathogens

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Other MDR gram-negative bacilli isolates were Klebsiella spp. 80 (67%), Psedomonas spp 35 (32.4%), Citrobacter spp. 6 (66.7%), Proteus spp. 3 (75%), Enterobacter spp. 2 (33.3%) and Providentia spp. 1 (100%). [Table ] Table. Percentage of the relative frequencies of various multidrug resistant GNB
Table 1: Percentage of the relative frequencies of various multidrug resistant GNB

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  Discussion Top

The World Health Organization has identified antimicrobial resistance as one of the greatest threats to human health. Two recent reports- one by the Infectious Diseases Society of America (IDSA) and another by the European Centre for Disease Prevention and Control and the European Medicines Agency- demonstrated that there are few candidate drugs in the pipeline that offer benefits over existing drugs and few drugs moving forward that will treat infections due to the so-called “ESKAPE” pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species), which currently cause the majority of US hospital infections and effectively “escape” the effects of approved antibacterial drugs.[20]

Resistance to the current library of antibacterial drugs is a serious problem in all parts of the world including the Asia- Pacific region, Latin America, Europe, and North America.[20]

In our study, Klebsiella spp. followed by Pseudomonas spp. were the most common Gram-negative bacilli isolated in cultures from LRTIs. This is in agreement with the study conducted by Lin et al.[21] and Gonlugur et al.[22] Interestingly, in Asian countrie K. pneumoniae is described as a frequent pathogen causing bacteremia.[21] In the present study, a significant number (61%) of gram-negative bacilli were found to be MDR with Escherichia coli 45/51 (88%), Acinetobacter spp. 41/51 (80.4%) and Klebsiella spp. 80/119 (67%) being the most common MDR Gram- negative bacilli isolated from LRTIs. This finding is concordant to study conducted by Gagneja et al., they found very high rate of resistance (60-100%) among A. baumannii and K. pneumoniae isolates.[23] Although Pseudomonas spp. was the second most common GNB isolate in our study, the percentage of MDROs 35/108 (32.4%) was relatively less among them. In contrast to the present study, Goel et al.[24] found high rates of multidrug resistance among P. aeruginosa. This is probably because their study was based on infections in intensive care unit, whereas the present study included both community acquired and nosocomial infections.

The MDR gram-negative bacilli were resistant to most of the so called commonly used antibiotics. Gram negative bacilli showed highest resistance to ampicillin , cephalosporins (cefotaxime, ceftazidime), fluoroquinolones (levofloxacin, ciprofloxacin), amoxicillin- clavulanate and piperacillin-tazobactam. Less resistance was evident to carbapenems (imipenem and meropenem) and tigecycl in. All the GNB isolates were 100% sensitive to colistin. Pseudomonas spp. showed a good antibiotic sensitivity pattern among MDR gram-negative bacilli. Most of the MDR Pseudomonas spp. were resistant to anti- pseudomonal χ-lactam antibiotics.

Further study is required to determine the prevalence and antibiotic susceptibility profile of nosocomial and community acquired MDR GNB pathogens.

  Conclusions Top

Correct identification of LRTI patients suspected of being infected with MDR Gram-negative pathogens is crucial. The collaboration of a multidisciplinary team (critical care specialists, pneumologist, infectious disease specialists, microbiologists) is needed to improve the management of the severe cases. The role of the microbiologist, in particular, is of pivotal importance to determine the antimicrobial susceptibility pattern of the pathogen causing LRTI, so that appropriate antibiotic therapy can be initiated as soon as possible. This would avoid excessive use of broad spectrum antimicrobials, which in turn increases the selection of resistant pathogens in-vivo. Antimicrobial stewardship programmes should be instituted in all care settings, based on resistance rates and audit of compliance with guidelines, but should be augmented by improved surveillance of outcome in Gram-negative bacteraemia, and feedback to prescribers.

Financial support and sponsorship: Nil.

Conflicts of interest: There are no conflicts of interest.

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  [Figure 1], [Figure 2], [Figure 3]

  [Table 1]


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