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ORIGINAL ARTICLE
Year : 2021  |  Volume : 10  |  Issue : 1  |  Page : 25-30

A surveillance study of multidrug-resistant organisms among clinically significant Gram-negative bacteria in a tertiary care teaching hospital from South India


Department of Microbiology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India

Date of Submission08-Mar-2020
Date of Decision22-May-2020
Date of Acceptance04-Aug-2020
Date of Web Publication4-Mar-2021

Correspondence Address:
Jayaprada Rangineni
Assistant Professor, Department of Microbiology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/JCSR.JCSR_116_19

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  Abstract 


Background: Sparse published data are available from Andhra Pradesh the burden of multidrug-resistant (MDR) Gram-negative bacteria in clinical specimens.
Methods: We studied the burden of MDR Gram-negative bacteria from among various clinical specimens in our tertiary care teaching institute.
Results: A total of 6900 isolates were obtained of which 2960 organisms were MDR. Escherichia coli were the most frequently isolated Gram-negative species (37%), followed by Klebsiella spp. (13.4%). Pseudomonas aeruginosa, Acinetobacter spp. and Enterobacter spp. were the other commonly isolated Gram-negative organisms. High resistance rates were observed for all antimicrobials studied except for cefoperazone-sulbactam (62.6%), meropenem (70%), aminoglycosides (64%) and polymyxin B (98.6%). In spite of high resistant rates (>50%) for ciprofloxacin (80%), cephalosporins (74.4%) and cotrimoxazole (65.7%), the above-mentioned antimicrobials were clinically effective. Extended-spectrum β-lactamase production was one of the significant mechanisms of resistance in our study as β-lactam resistance was 74.4%.
Conclusions: Our study documents a high proportion of resistant Gram-negative organism isolates. Clinicians should consider this while initiating antibiotic treatment.

Keywords: Antimicrobials, carbapenem, Gram-negative bacteria, multidrug resistant


How to cite this article:
Rangineni J, Nukanaboina R, Sharma KK. A surveillance study of multidrug-resistant organisms among clinically significant Gram-negative bacteria in a tertiary care teaching hospital from South India. J Clin Sci Res 2021;10:25-30

How to cite this URL:
Rangineni J, Nukanaboina R, Sharma KK. A surveillance study of multidrug-resistant organisms among clinically significant Gram-negative bacteria in a tertiary care teaching hospital from South India. J Clin Sci Res [serial online] 2021 [cited 2021 Aug 3];10:25-30. Available from: https://www.jcsr.co.in/text.asp?2021/10/1/25/310763




  Introduction Top


Healthcare facilities, in spite of evident effect on clinical outcome, are now turned to be a major source for healthcare-associated infections (HAIs). The patients in various departments of healthcare facility have a high risk of nosocomial infection and 20%–25% of HAIs reported in intensive care units (ICUs).[1],[2] ICU infections caused by Gram-negative bacteria leading to sepsis are one of the important causes for mortality, morbidity and prolonged hospital stay. This is because of interrelationship between severity of diseases, comorbidities, duration of stay in ICUs and the most important one being whether patient has any devices such as tubes, drains and lines.[1] Patient care, especially in ICUs, demands more frequent contact with healthcare workers. Breach in hand hygiene and asepsis in emergencies may result in horizontal transmission of infections.[3] Injudicious administration of broad spectrum antimicrobials among these patients results in selective pressure on Gram negative organisms which results in either colonisation or infections by multidrug resistant (MDR) bacteria, leading to sepsis.[3],[4]

Data related to individual department-wise infection rates and susceptibility pattern within a healthcare organization are insubstantial, albeit studies have yielded greater infection and mortality rates with higher antimicrobial resistance (AMR) in other parts of the world.[1],[5]

This study was undertaken to study the prevalence of Gram-negative bacteria isolated in clinical isolates obtained from healthcare facility and also to study the resistant rates to commonly used antimicrobials in our healthcare facility.


  Material and Methods Top


This was a retrospective study conducted in the Department of Microbiology, at our tertiary care teaching hospital, Tirupati. The study included aerobic Gram-negative bacteria isolates from clinical specimens submitted from January to June 2019.

Microbiological diagnosis was performed on various clinical samples that were submitted to the department of microbiology as per the standard protocols. All the samples were processed on nutrient agar, blood agar, MacConkey agar and chocolate agar. Identification was carried out depending on the culture characteristics and biochemical reactions. Sensitivity testing to antimicrobials was done by Kirby–Bauer disc diffusion method as per the Clinical Laboratory Standards Institute (CLSI) guidelines 2018.[6] Twelve different antimicrobials including amikacin (30 μg), cefotaxime (30 μg), cefoperazone + sulbactam (75/10 μg), ciprofloxacin (5 μg), gentamicin (10 μg), cotrimoxazole (1.25/23.75 μg), piperacillin + tazobactam (100/10 μg), meropenem (10 μg), ceftazidime (30 μg), aztreonam (30 μg), imipenem (10 μg) and polymyxin B (300 units) on Mueller–Hinton agar were studied. All were noted from records and analysed. For polymyxin B, no CLSI guidelines are available for the interpretation of disc diffusion technique as regards Enterobacteriaceae and Acinetobacter sp. For these isolates, the recommendation of Galani et al. was adopted. For each isolate, data regarding patient hospital identification number, admission department, type of sample, clinical diagnosis and demographic data were documented.[7] In our study for analysing the data, we considered intermediate-susceptible isolates as resistant by deploying CLSI 2018 breakpoints.[8] For Pseudomonas sp., imipenem was used as an indicator antibiotic to study the carbapenem resistance, and in cephalosporins group, antipseudomonal cephalosporin ceftazidime was being used for surveillance.

Statistical analysis

Data were entered and analysed using Microsoft Excel 2.0. Categorical variables such as proportion of bacterial infections across different wards and ICUs, age groups and gender were expressed as percentage. Pattern of microorganisms, sites of infections and resistant rates were analysed and expressed as percentage.


  Results Top


In our study, 2960 MDR organisms were isolated from 6900 positive cultures. Among them, 60.1% were isolated from male patients and 39.9% were isolated from female patients. More than 50% (61.1%) of isolates were reported from the age group of 41–70 years. Majority of organisms was reported from the urinary tract infections (44.3%) followed by respiratory tract infections (18%), bloodstream infections (17.5%), pus (15%) samples and remaining from other samples. Majority of MDR pathogens were reported from the ICUs (35.8%) followed by medical wards (29.2%), surgical wards (20.9%) and outpatient departments (14%) [Figure 1].
Figure 1: Distribution of multidrug-resistant isolates among various wards

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Resistant rates were reported high for all antimicrobials except for polymyxin B (sensitivity rate being 99.6%) [Table 1]. Carbapenems (meropenem/imipenem) and aminoglycosides (amikacin/gentamicin) remained relatively as active agents for most of the Gram-negative organisms. Majority of carbapenem-resistant isolates were reported from the ICUs (28.6%) in our study. Among antimicrobials studied, cefoperazone-sulbactam (62.6%), carbapenems (70%) and aminoglycosides (64%) were found to be relatively effective on majority of Gram-negative organisms. More than 50% of isolates of Escherichia coli, Enterobacter sp. and Acinetobacter sp. showed sensitivity to cefoperazone-sulbactam [Table 1].
Table 1: Antimicrobial susceptibility pattern of multidrug-resistant isolates (%)

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Antibiotic susceptibility of the most commonly isolated pathogens, namely P. aeruginosa, Klebsiella spp., Acinetobacter spp. and E. coli, varied considerably among the various departments of healthcare facility. As the most active agent against P. aeruginosa, imipenem had resistance rates ranging from 60.9% in outpatient department isolates to as high as 87.5% in medical wards. Piperacillin/tazobactam was moderately effective against Pseudomonas spp. (55.4%), and ceftazidime was highly resistant to Pseudomonas spp. ranging from 75.6% to 87.5% in various isolates [Table 2],[Table 3],[Table 4],[Table 5]. Resistance to ciprofloxacin was also very high for Pseudomonas (>80%) [Table 1]. ESBL producers were highly reported from Klebsiella spp. (61.1%) followed by Enterobacter spp. (46.3%), Pseudomonas spp. (42%) and E. coli (17.4%) [Table 6].
Table 2: Antimicrobial susceptibility pattern of organisms isolated from intensive care units (%)

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Table 3: Antimicrobial susceptibility pattern of organisms isolated from Medical wards (%)

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Table 4: Antimicrobial susceptibility pattern of organisms isolated from Surgical wards (%)

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Table 5: Antimicrobial susceptibility pattern of organisms isolated from Outside samples (%)

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Table 6: Resistance pattern to pencillins and cephalosporins (extended-spectrum β-lactamase), carbapenems and polymyxin B among various Gram-negative isolates

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E. coli isolated from ICUs samples had shown moderately high resistance to aminoglycosides and beta-lactamase combination drugs (cefoperazone-sulbactam/piperacillin-tazobactam) [Table 2]. Overall, in all departments, E. coli showed high sensitivity to carbapenem antimicrobial agents (>80%) and high resistance to cephalosporins (cefotaxime/ceftazidime) (81.4%), fluoroquinolones (ciprofloxacin) (85.9%) and cotrimoxazole (67%).

Isolates of Klebsiella spp. reported from the ICUs were >50% resistant to carbapenems (54.8%) when compared with other departments [Table 2]. Majority of Klebsiella spp. isolates showed high resistance to fluoroquinolones (76.6%), cotrimoxazole (83.7%) and cefotaxime (88.4%) [Table 1]. Acinetobacter spp. isolated from various departments showed moderate sensitivity to cefoperazone-sulbactam (58%) and almost 99% sensitivity to polymyxin B.

Extended-spectrum β-lactamase (ESBL) producers were highly reported from Klebsiella sp. (61.1%) followed by Enterobacter spp. (46.3%), Pseudomonas spp. (42%) and E. coli (17.4%). Sensitivity pattern to antimicrobial agents in ESBL-producing and non-ESBL-producing bacteria was grossly different. High resistant rates to other antimicrobials were reported in ESBL-producing E. coli, Klebsiella and other Gram-negative isolates [Figure 1] and [Figure 2].
Figure 2: Comparison of resistance pattern among ‘ESBL’-producing Escherichia coli and ‘Non-ESBL’-producing Escherichia coli. AK = Amikacin; CTX = Cefotaxime; CFS = Cefoperazone + sulbactam; CF = Ciprofloxacin; COT = Cotrimoxazole; G = Gentamicin; I = Imipenem; PTZ = Piperacillin + tazobactam; Pb = Polymyxin-B; CTZ = Ceftazidime; M = Meropenem; ESBL = Extended-spectrum beta-lactamase

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Carbapenem resistance in ESBL-producing E. coli was 56.6% which was in contrast to non-ESBL producers where it was 10.1%. Similar to this Klebsiella spp., carbapenem resistance in ESBL producers observed was 65.1%, but in non-ESBL producers, it was 45.5% [Figure 1] and [Figure 2].


  Discussion Top


Among HAIs, urinary tract infections and pneumonia are predominant infections; in accordance with this, in our study, most of the organisms were reported from various departments of healthcare facility including ICUs.[1] Gram-negative organisms isolated in our study differed from other studies.[1],[5],[9],[10],[11] Most common Gram-negative isolates accounted in our study were E. coli (37%), Klebsiella spp. (13.4%), Acinetobacter spp. (6.5%) and Pseudomonas spp. (6.3%).

In recent years, treatment of multidrug resistance among Gram-negative organisms becomes a major threat.[9] The high prevalence of MDR bugs leads to mortality, prolonged hospital stay and economical burden to the patients. In our study, among 6900 culture-positive samples, the percentage of MDR isolates was 42.9% (n = 2960). In another study by Apurba et al., they reported that 55.7% of the Gram-negative bacterial isolates were MDR.

Our study documented high resistant rates to antimicrobials such as cephalosporins, fluoroquinolones and cotrimoxazole, which were commonly used as the first-line drugs to treat HAIs. In our study, carbapenems stand out as antimicrobials with low resistance, but still the resistant rates are higher to these preserved drugs, which is alarming [Table 1]. All antimicrobials tested in our study showed high resistance rates except for polymyxin B. Carbapenems, beta-lactam and beta-lactamase inhibitor combinations and aminoglycosides are still remained as effective against majority of the Gram-negative organisms [Table 1].

Majority of carbapenem-resistant isolates were reported from ICUs (28.6%) in our study [Table 2]. Cefoperazone-sulbactam, amikacin and meropenem were clinically relatively effective in vivo, but in susceptibility testing, the resistant rates were exceeded more than 50% in our study. Cefoperazone-sulbactam was more effective against E. coli, Enterobacter spp. and Acinetobacter species (>50%) [Table 1].

Antimicrobial sensitivity of most frequently isolated Gram-negative bacteria was diversified significantly in various departments of healthcare facility. Imipenem is effective antimicrobial against P. aeruginosa, but imipenem resistance rates range from 60.9% in outpatient department samples to as high as 87.5% in the medical wards [Table 3]. Piperacillin/tazobactam was moderately effective against Pseudomonas spp. and ceftazidime was highly resistant to Pseudomonas spp. ranging from 75.6% to 87.5% in various departments [Table 2],[Table 3],[Table 4],[Table 5]. Resistant to ciprofloxacin was also very high for Pseudomonas (>80%) in our study. In various parts of India, AMR in P. aeruginosa differs considerably which is similar to our study.[9] In a study,[10] Pseudomonas aeruginosa showed resistance to imipenem that ranges between 33%–73% and for ceftazidime being 31%–76%.[10]

E. coli isolated from the ICU's samples had shown moderately high resistant to aminoglycosides and beta-lactamase combination drugs [Table 2]. Over all, E. coli showed high sensitivity to carbapenems (>80%) but more than 70% resistance to cephalosporins, fluoroquinolones and cotrimoxazole in all departments [Table 1].

Isolates of Klebsiella spp. reported from the ICUs were >50% resistant to carbapenems (54.8%) when compared with other departments [Table 2]. Isolates of Klebsiella spp. showed high resistance to fluoroquinolones, cotrimoxazole and cephalosporins (>80%) [Table 1]. In a study conducted by Moolchandani et al.,[11] they observed potent resistance to cephalosporins (67.6%–89.9%), quinolones (74.1%–90.1%) and aminoglycosides (48.2%–76.2%) among Enterobacteriaceae members. Minimal resistance is seen on incorporation of beta-lactamase inhibitor (14.8%–18.2% resistance against cefoperazone/sulbactam). Resistance to carbapenems (9.5%–51.1%) was remarkable in their study. By and large, when compared with E. coli, Klebsiella spp. and Enterobacter spp. showed higher resistance which is similar to other studies conducted by Jamshidi et al., Mohammadi-Mehr and Feizabadi, Ganguly et al.[12],[13],[14]

Acinetobacter spp. (11.2%) was the third most common Gram-negative bacteria followed by E. coli and Klebsiella spp., especially from ICU samples. In a retrospective study[15] reported similar findings in which non-fermentative Gram-negative bacteria were predominant isolates. In another study[16] Pseudomonas spp. was the leading cause of HAI. Another study[17] reported Acinetobacter spp. as the second most common isolate from ICUs. In our study, Acinetobacter spp. isolated from various departments showed moderate sensitivity to cefoperazone-sulbactam (67.7%) and almost 99% sensitive to polymyxin B [Table 1].

Carbapenem resistance was noted high in Pseudomonas (77.9%) followed by Acinetobacter spp. (57.3%), Klebsiella spp. (45.5%), Enterobacter spp. (14.6%) and E. coli (10.1%). Hence, cautious prescription of carbapenems is required [Table 1].

ESBL producers were highly reported from Klebsiella spp. followed by Enterobacter spp., Pseudomonas spp. and E. coli [Table 6]. Sensitivity pattern to antimicrobial agents in ESBL-producing and non-ESBL-producing bacteria is grossly different. High resistant rates to other antimicrobials were reported in ESBL-producing E. coli, Klebsiella spp. and other Gram-negative isolates [Figure 2] and [Figure 3]. In our study, the resistant rates to cefotaxime were very high representing ESBL production as a major mechanism of resistance. In our study for ESBL detection, aztreonam (30 μg) was used as per the CLSI guidelines 2018.[7]
Figure 3: Comparison of resistance pattern among ‘ESBL’-producing Klebsiella spp. and ‘Non-ESBL’ Klebsiella spp. AK = Amikacin; CTX = Cefotaxime; CFS = Cefoperazone + sulbactam; CF = Ciprofloxacin; COT = Cotrimoxazole; G = Gentamicin; I = Imipenem; PTZ = Piperacillin + tazobactam; Pb = Polymyxin-B; CTZ = Ceftazidime; M = Meropenem; ESBL = Extended-spectrum beta-lactamase

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Carbapenem resistant in ESBL-producing E. coli was 56.6% which were in contrast in non-ESBL producers where it was 10.1%. Similar to this, the percentage of Klebsiella spp. carbapenem resistance in ESBL producers was 65.1, but in non-ESBL producers, it was 45.5% [Figure 2] and [Figure 3]. In conclusion, our study revealed high resistant rates to antimicrobial agents that are commonly used as the first-line drugs to treat HAIs. Resistant to carbapenems is also alarming, for that strict implementation of antimicrobial stewardship, i.e., prescribing antimicrobials as per the policy and strict adherence to infection control practices, is mandatory to control the emergence and spread of resistance among Gram-negative isolates.

Being a retrospective study, clinical correlation was not accomplished for all isolates. Mortality, morbidity and length of stay were not analysed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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