Bengal Physician Journal
Volume 7 | Issue 1 | Year 2020

A Spectrum of Causative Organisms of Healthcare-Associated Infections in a Tertiary Care Hospital of West Bengal—An Observational Study

Sinjan Ghosh1, Mukhopadhyay Mainak2, Anjum Namhata 3, Nandini Chatterjee 4

1Department of Neurology, NRS Medical College, Kolkata, West Bengal, India

2Department of Cardiology, Midnapur Medical College Hospital, Midnapur, West Bengal, India

3Department of Microbiology, NRS Medical College, Kolkata, West Bengal, India

4Department of Medicine, IPGMER and SSKM Hospital, Kolkata, West Bengal, India

Corresponding Author: Anjum Nanhata, Department of Microbiology, NRS Medical College, Kolkata, West Bengal, India, Phone: +91 8902221317, e-mail: rivuc23092006@gmail.com

How to cite this article: Ghosh S, Mukhopadhyay M, Namhata A, et al. A Spectrum of Causative Organisms of Healthcare-Associated Infections in a Tertiary Care Hospital of West Bengal: An Observational Study. Bengal Physician Journal 2020;7(1):2–7.

Source of support: Nil

Conflict of interest: None


Background: Nosocomial infections are the foremost reasons for morbidity and mortality among hospitalized patients. Rampant use of antibiotics in infections has led to the emergence of multiresistant bacteria worldwide. Periodical review of sensitivity profiles is of utmost importance for optimal patient benefit.

Aims and objectives: To explore the spectrum of organisms responsible for intensive care unit (ICU) and inpatient hospital-acquired sepsis and evaluate the pattern of antibiotic sensitivity of the organisms.

Materials and methods: Samples were collected from all consecutive patients getting fever and satisfying the criteria for a nosocomial infection indoor as well as ICU, irrespective of etiology. They included sputum, blood, urine, and wound swabs. All samples were sent for a routine examination as well as a culture and sensitivity test. Descriptive statistical methods were used with the help of SPSS version 21.

Results: The most frequent organisms for nosocomial infections in the ICU were Enterobacteriaceae (45%), Acinetobacter (13.7%), and Staphylococcus aureus (12.3%). In the general wards, the most common isolates were Enterobacteriaceae (59.9%), S. aureus (14.5%), Enterococcus (9.8%), and Pseudomonas (9.3%). There was a high percentage of extended-spectrum beta-lactamase among the Enterobacteriacae, methicillin-resistant S. aureus, and borderline oxacillin-resistant S. aureus among S. aureus and metallo-ß-lactamase among the Acinetobacter and Pseudomonas. These indicate resistance to most beta-lactams, cephalosporins, and at times to carbapenems. There was also coresistance to fluoroquinolones and aminoglycosides.

Conclusion: An antibiotic policy should be improvised for each healthcare facility on the basis of that point of time.

Keywords: Infection, Multiresistant, Nosocomial, Sensitivity.


Antibiotics are essential components of modern therapeutic practices. But inappropriate and indiscriminate usage of antibiotics can result in resistance of organisms. Healthcare-associated infections (HAIs) lead to poor outcomes in hospitalized patients.1 Thus, it is mandatory to abide by certain norms while prescribing antibiotics to minimize nosocomial infections which are defined as those that occur within 48 hours of admission or 3 days after discharge from a healthcare facility and it was absent during admission.2 Empirical antibiotic therapy if not matched with suitable sensitivity profiles definitely leads to polyresistance in severe sepsis.3 So, it is essential for the institutions to have in-house up-to-date data to evaluate the likely causatives. This will assist in choosing empirical drugs from sensitivity patterns.

Studies concerning culture and sensitivity profiles of body fluids have been performed over the decades. There have been changes in the sensitivity profiles over time and more so due to the indiscriminate as well as illogical use of antibiotics. We endeavored to study the current trend of causative organisms and their antibiotic sensitivity and to compare it with the previous work done in this field. This study was done for 6 months to identify the pattern of organisms isolated from the intensive care unit (ICU) and inpatients of wards.



This is an observational study carried out in the ICU and the general wards of our hospital for a period of 6 months. Nonpurposive convenient sampling method was used to select patients. All patients with undiagnosed fever that developed 48 hours after admission to the hospital were included in the study fulfilling the criteria for a nosocomial infection. Immunocompromised and neutropenic patients and patients on steroids or immunosuppressive drugs were excluded. After taking informed consent, detailed history and clinical examination were recorded in a prevalidated proforma.

Antimicrobial sensitivity tests were performed on bacteria considered significant. The antibiotics included in our study were Co-amoxiclav, ampicillin, trimethoprim/sulfamethoxazole (cotrimoxazole), norfloxacin, ciprofloxacin, levofloxacin, ofloxacin, nitrofurantoin, gentamicin, amikacin, doxycycline, cefuroxime, ceftazidime, cefotaxime, netilmicin, polymyxin B, Colistin, piperacillin/tazobactam, cefoperazone/sulbactam, meropenem, imipenem, vancomycin, tigecycline, and teicoplanin.


The study was conducted for 6 months in the general wards as well as ICU of a tertiary care hospital. The total number of samples collected was 1,046, of which 255 were from ICU. Seventy-three were positive isolates in the ICU (Table 1). Of 73 isolates, respiratory tract infection accounted for 33, urinary tract infection (UTI) 10, wound sepsis 7, bacteremia/septicemia 11, and intravenous (IV) catheter sepsis in 2 patients. Ten samples (15.4%) were due to probable colonization.

Fig. 1: Sensitivity patterns of organisms in ICU

Table 1: Antibiotic sensitivity patterns of common isolates from inpatients location: intensive care units
Antibiotics Isolates (% sensitive)
Enterobacteriaceae Pseudomonas Acinetobacter Staphylococci Enterococci
N = 34 N = 9 N = 10 N = 9 N = 5
Amoxicillin 00 11 60
Cloxacillin/oxacillin 44
Carbenicillin 00
Piperacillin 00
Ampicillin-sulbactam 60
Amoxicillin-clavulanate 06 10 11 60
Piperacillin-tazobactam 62 44 80 56 100
Ticarcillin-clavulanate 35 00 20 56
Cefoperazone-sulbactam 65 56 100 56
Cephalexin 56
Cefuroxime 16 56
Cefotaxime 24 20
Ceftazidime 24 11 20
Cefoperazone 11
Cefpirome 56
Cefepime 24 11 20
Aztreonam 24 11 20
Imipenem 100 78 60 100
Meropenem 100 78 60
Azithromycin 33 40
Clindamycin 67
Vancomycin 100 100
Teicoplanin 100 100
Linezolid 100 100
Gentamicin 56 22 70 89 (High dose) 60
Tobramycin 47 22 80
Netilmicin 68 67 80 100 60
Amikacin 65 67 80 100 60
Ciprofloxacin 35 44 40 56 20
Ofloxacin 38 44 60 56 20
Levofloxacin 62 44 80 56 20
Moxifloxacin 56 44 80 78 60
Cotrimoxazole 21 00 40 33
Chloramphenicol 68 40 78 40
Tetracycline 44 50 89 20
Tigecycline 94 100 100 80
Polymyxin B 89 100
Colistin 89 100

Total no. of samples: 1464; no. of inpatient samples: 1046; no. of ICU samples: 255; total no. of ICU isolates: 73; polymicrobial growth: 8 samples (12.3%); NA, antibiotic disks not available

The most common organisms isolated were Enterobacteriaceae (34 isolates, i.e., 45%). Of which 15 (44%) were extended-spectrum beta-lactamase (ESBL) producers; 11 (32%) probable coproducers of ESBLs and AmpC beta-lactamases. All isolates were sensitive to imipenem and meropenem.

Among the Acinetobacter sp., the next most common organism (10 isolates, i.e., 13.7%), 4 (40%) were carbapenem resistant and 3 (75%) of those were metallo-ß-lactamase (MBL) producers. Polymyxins, cefoperazone/sulbactam and tigecycline covered 100% of the isolates.

Other organisms isolated were:

The results from inpatients revealed the following (Table 2): there were 791 samples collected, of which 172 were positive. Of 172 isolates, respiratory tract infection accounted for 10, UTI 70, wound sepsis 60, bacteremia/septicemia 15, IV catheter infection in 3; 14 samples (9%) were due to probable colonization.

Here also the most frequent isolate was Enterobacteriaceae: 103 isolates (59.9%). Fifty-four (52%) ESBL producers; 11 (11%) probable coproducers of ESBLs and AmpC beta-lactamases. All were carbapenem sensitive. They were poorly responsive to cephalosporins and quinolones.

Next were Staphylococci: 25 isolates (14.5%): 10 (40%) MRSA, 2 (8%) BORSA, 13 MSSA. Well responsive to vancomycin, clindamycin, and linezolid.

Enterococci: Of the 17 isolates (9.8%), all were sensitive to vancomycin, linezolid, and tigecycline.

Pseudomonas: 16 isolates (9.3%): all P. aeruginosa: 6 (38%) carbapenem resistant: all were MBL producers. All were polymyxin sensitive.

Acinetobactersp.: 3 isolates (1.7%): 1 (33%) carbapenem resistant and MBL producer. All sensitive to polymyxins, cefoperazone/sulbactam, and piperacillin/tazobactam (Fig. 2).

Fig. 2: Sensitivity patterns of organisms in wards

Fungi: 8 isolates (4.6%), all Candida sp.: 4 (50%) albicans; 4 (50%) non-albicansspp.

To summarize, the pattern of infection reveals a spectrum of multiresistant bacteria both in ICU and general wards responsive to the highest grade of antibiotics. However, Acinetobacter was much more frequently found in ICU than wards, though Enterobacteriacae and S. aureus were omnipresent.4


HAIs comprise catheter-associated UTI, pneumonia including ventilator-associated pneumonia, bloodstream infection, gastroenteritis, and surgical site and wound sepsis.5 Nosocomial infections are most frequently bacterial.6 Some may be commensals of the patient taking the upper hand when immunity becomes weak. In the ICU, almost 70% of the organisms constitute Staphylococci, Enterobacteriaceae, Pseudomonas, and Acinetobacter species. Enterobacteriaceae include Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, and Serratia marcescens.79

Our study revealed that growth of Enterobacteriaceae, Acinetobacter, S. aureus, and Pseudomonas were most isolated in the ICU. In the wards, Enterobacteriacae, S. aureus, and Pseudomonas were most frequent. This spectrum is similar to the studies in the United Kingdom, Canada, Uganda, etc.1012 Of the Enterobacteriaceae 103 isolates: 54 (52%) ESBL producers; 11 (11%) probable coproducers of ESBLs and AmpC beta-lactamases. Among the Staphylococci 25 isolates: 10 (40%) MRSA; 2 (8%) BORSA; 13 MSSA. For Acinetobacter sp. 3 isolates: 1 (33%) carbapenem resistant and MBL producer and for Pseudomonas 6 isolates (38%) carbapenem resistant: all were MBL producers. A study from Punjab revealed production of ESBL, AmpC beta-lactamase, and MBL by E. coli and K. pneumoniae.

Table 2: Antibiotic sensitivity patterns of common isolates from inpatients, location: general wards (non-ICU)
Antibiotics Isolates (% sensitive)
Enterobacteriaceae Pseudomonads Acinetobacter Staphylococci Enterococci
N = 103 N = 16 N = 3 N = 25 N = 17
Amoxicillin 06 16 65
Cloxacillin/oxacillin 52
Carbenicillin 13
Piperacillin 13
Ampicillin-sulbactam 67
Amoxicillin-clavulanate 17 00 24 65
Piperacillin-tazobactam 87 50 100 60 82
Ticarcillin-clavulanate 41 31 00 60
Cefoperazone-sulbactam 88 50 100 60
Cephalexin 60
Cefuroxime 20 60
Cefotaxime 32 00
Ceftazidime 32 19 00
Cefoperazone 19
Cefepime 32 25 00
Aztreonam 32 38 00
Imipenem 100 63 67 82
Meropenem 100 63 67
Azithromycin 56 47
Clindamycin 68
Vancomycin 100 100
Teicoplanin 100 100
Linezolid 100 100
Gentamicin 61 50 33 92 (High dose) 59
Tobramycin 59 50 33
Netilmicin 71 50 67 92 65
Amikacin 70 69 33 92 59
Ciprofloxacin 41 50 33 68 35
Ofloxacin 47 50 33 76 47
Levofloxacin 69 50 67 88 59
Moxifloxacin 83 50 67 92 76
Cotrimoxazole 34 19 33 44
Chloramphenicol 68 88 53
Tetracycline 54 33 92 47
Tigecycline 95 67 100 100
Polymyxin B 100 100
Colistin 100 100

No. of inpatient samples: 1046; no. of non-ICU samples: 791; total no. of non-ICU isolates: 172; polymicrobial growth: 15 samples (9.6%); NA, antibiotic discs not available

Of all isolates, ESBL was detected in 35.16% and MBL producers in 10.98%.13

Thus, they manifested multidrug resistance and propensity to respond only to higher antibiotics like carbapenems, polymyxin, Colistin, vancomycin, tigecycline, etc. The initial choice of drugs like cephalosporins and beta-lactams is useless in this setting. Coresistance to quinolones and aminoglycosides was seen maybe due to plasmid transfer, which is of grave concern.

The fungal isolate in this study, i.e., Candida species is another fixture in all HAI spectrum of organisms. It is isolated mostly in patients with diabetes, renal failure, and cancer and in immunocompromised patients. It is said to be the sixth common cause of nosocomial infection worldwide.14

World Health Organization documents around 15% of all hospitalized patients develop nosocomial infections.15 Susceptibility to HAI increases due to unhygienic environment, improper waste disposal, and ignorance among healthcare personnel.16

Patient factors include immunosupression, increased duration of ICU admission, and continued antibiotic therapy. Improper techniques of use of invasive devices (cannula and catheters) and absence of control policies are all incriminated as predisposing factors.17

In low-income countries, the above factors are linked to poor economic status, inadequate staff, and infrastructure.18

It is important to devise ways of prevention of nosocomial infections by practicing well-monitored healthcare delivery, maintenance of hygiene, and specifically targeted antimicrobial prescription policy.

Proper waste disposal, cleanliness in the environment, proper food handling, and hand hygiene should be practiced. Foremost is also to take measures for the prevention of drug resistance to develop.19,20

It is important that every hospital should have an infection control group who would devise an antibiotic policy for that particular healthcare facility. Our study is a typical microbiological surveillance report on the current pathogen spectrum and their sensitivity pattern.

An antibiotic policy provides guidelines for use in specific infections for that institution at a point in time. It is reviewed by a microbiologist and devised based on the latest surveillance data.21,22

The following are the measures to be undertaken:

  1. a. Training on antibiotic usage.
  2. b. Monthly data surveillance and feedback to be reviewed periodically.
  3. c. Hospital infection control group will formulate guidelines to ensure restricted antibiotic use.


Viral identification was not possible in our setup. The total number of samples was limited and stool samples were not done.


Superbugs are emerging day by day in healthcare setups where traditional antibiotics are becoming useless. The importance of periodical sampling and culture and sensitivity tests cannot be undermined as the bacterial spectrum and the sensitivity change over time. Moreover, it helps to lay down an antibiotic policy for a particular institution that goes a long way in the prevention of multidrug resistance in the future.


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