Epidemiology of nosocomial infections in medicine intensive care unit at a tertiary care hospital in northern India

Abstract

This prospective observational study describes the rates of nosocomial infections (NI), the sites of infection, the pathogens involved, their antibiogram and the risk factors at a tertiary care hospital in northern India. In 62 of the 182 enrolled patients 95 episodes of NI were recorded (incidence rate 28.6/1000 person days): pneumonia (77%); urinary tract infection (24%) and blood stream infection (24%). All isolates of Acinetobacter, Pseudomonas and Klebsiella and 83.3% of Escherichia coli were resistant to the third generation cephalosporins. An increased duration of the time spent in intensive care units and days of intervention were associated with incident NI.

Introduction

Nosocomial infections (NIs) result in increased morbidity, mortality and length of hospital stay.¹ The Incidence of NIs, their risk factors and the antibiogram patterns vary across and within countries.² Furthermore, intensive care units (ICUs) act as epicentres for NI and the development of antimicrobial resistance due to prolonged hospitalization, serious illness and a high use of antibiotics.³

There are very few published studies on the epidemiology of NIs from India. In this study, we report rates, infection sites, pathogens, risk factors and the antibiotic sensitivity of NI in ICU patients of at a tertiary care hospital in northern India.

Methods

This prospective observational study was done at an eight-bed medical ICU of a tertiary care referral hospital in northern India. An open cohort of all patients admitted to the unit from January 2004 to July 2005 was followed for NIs, until either discharge from the ICU or death. Patients who died or were transferred from the ICU within 48 hours of their entry were excluded from the study. Those who already had had an infection within <48 hours were followed for superadded infections. Active surveillance was carried out to identify the NI according to the definitions of the Center for Disease Control and Prevention (CDC).⁴

Baseline cultures of blood, urine and tracheal aspirate (for intubated patients) were sent for the isolation of pathogens, and antimicrobial sensitivity testing, in accordance with Clinical and Laboratory Standard Institute Guidelines. ⁵ Further samples were tested according to the suspected sites of infection, in patients with a clinical suspicion of infection. Pneumonia was defined based on the CDC definition.

The association between the clinical factors, interventions and NIs was tested using chi-squared test. The relationship between the duration of ICU stay and NIs was tested using a linear model with transformations. SAS version 9.1.3 (Cary, NC, USA) was used for analysis.

Results

One hundred and eighty-two (58.3%) of the 312 patients admitted to ICU during study duration met the inclusion criteria. All study participants/their proxies (for comatose patients) gave informed consent.

The demographic and clinical characteristics of patient are as follows: men 64.3%, mean age 48.8 years, mean Acute Physiology and Chronic Health Evaluation (APACHE II score) 14 (range: 4–52). Hypotension and type II respiratory failure were the most common indications for ICU admission. Sixty-two patients (34.1%) had had one or more NI episodes (total 95 episodes). The incidence rate (IR) of NI was 28.6/1000 patient days at risk.

Common infection sites were: pneumonia (77.4%, 63 episodes, IR = 22.1/1000 patient days); urinary tract infection (UTI) (33.9%, 23 episodes, IR = 9.7/1000 patient days); and catheter-related blood stream infection (BSI) (19.4%, nine episodes, IR = 2.3/1000 patient days).

Ninety-eight percent of the intubated patients and 43.8% of patients with tracheostomy had pneumonia (IR = 31.4/1000 ventilator days). All patients with nosocomial UTI had a urinary catheter in situ (IR = 11.3/1000 urinary catheter-days). All patients with nosocomial BSIs had a central line and 80% had a peripheral intravenous line (IR = 3.4/1000 central venous pressure (CVP) line days).

Acinetobacter (58.3% episodes), Pseudomonas (43.7% episodes), E. coli (10.4% episodes) and Enterococci (1.2% episodes) were the most common pathogens isolated from patients with pneumonia. Similarly, Candida spp. (90.4% of the episodes), Pseudomonas (14.2% episodes) and E. coli (4.76% episodes) were isolated from nosocomial UTI. Organisms causing nosocomial BSIs were Pseudomonas (33.3% episodes), and Acinetobacter, E. coli, Candida spp., Coagulase-negative staphylococci and Staphylococcus aureus caused one episode each. These BSI organisms were isolated from cultures of blood and the CVP line tip.

The antibiogram of the pathogens to the commonly used antibiotics is shown in Table 1. Additionally, both coagulase-negative staphylococcus and Staphylococcus aureus were methicillin resistant but showed in vitro sensitivity to linezolid and vancomycin.

Table 1

The antibiotic resistance pattern of common pathogens isolated in 62 bacterial isolates of patients admitted to the intensive care unit of a tertiary care hospital in northern India

Organism	Antibiotic (% resistant)
Organism	Ceftazidime	Netilmycin	Meropenem	Cefoperazone-sulbactam	Piperacillin-tazobactam
Acinetobacter	100%	36.4%	70.4%	35.7%	58.6%
Pseudomonas	100%	70%	60%	50%	50%
Escherichia coli	83.3%	100%	0	16.7%	40%
Klebsiella	100%	50%	50%	33.3%	0

The analysis of the few risk factors is shown in Table 2. Importantly, the length of stay in ICU was linearly associated with NI (P for trend <0.001). Notably, no patient staying less than five days in ICU developed NI. Intubation and mechanical ventilation (relative risk [RR] = 12.4 [1.6, 93.9]), tracheostomy (RR = 5.59 [2.3, 13.2]) and nasogastric tube insertion (RR = 5.48 [1.7–42.8]), were associated with a risk of developing nosocomial pneumonia. Similarly, urinary catheterization was associated with nosocomial UTI (RR = 2.50 [1.02–6.1]). Also, central venous catheterization (but not a peripheral venous line) was associated with development of nosocomial BSI (RR = 4.38 [2.2–8.7]).

Table 2

Risk factors for the development of a nosocomial infection (NI) in an intensive care unit (ICU) in northern India (n = 182)

Risk factor^a	Patients with NI N = 62; n (%)	Patients without NI N = 120; n (%)	P value
Age >60 years	23 (38.3)	48 (67.6)	0.06
APACHE II >12	42 (78.3)	88 (74.1)	0.45
Chronic obstructive airway disease	25 (40.3)	34 (28.3)	0.1
Diabetes mellitus type II	8 (12.9)	18 (15.1)	0.6
Immunosuppression	5 (8.1)	12 (10.0)	0.87
Cytotoxic drug therapy	3 (4.8)	7 (5.8)	0.78
Stress ulcer prophylaxis	50 (80.6)	91 (75.8)	0.46
Hypoalbuminaemia (<30 g/L)	34 (54.`8)	58 (48.3)	0.40
ICU stay ≥8 days	54 (88.5)	20 (16.5)	<0.0001

^aDoes not include interventions

The mean duration of at-risk ICU stay for those who developed NI was 20.1 days (range 5–68 days) compared with eight days for those who did not develop NI (range 3–28 days). A total of 105/182 (57.6%) patients died during the follow-up period. Of the 62 patients with NI, 32 (53.3%) died and 28.8% of these deaths were attributed to the infection. Mortality in patients without NI was 69.5% and was not statistically different from those without NI (P = 0.57).

Discussion

NIs are seen worldwide but are less studied and are given less emphasis in developing countries. This study reports a high IR of NI, as well as high antibiotic resistance, in ICU settings of a tertiary care hospital in northern India. The relatively high incidence of NI observed in this study may be a reflection of the higher severity of illness, poorer nutritional status, more interventions, fewer staff and, possibly, poor adherence to aseptic measures. Also, the high proportion of mechanical ventilation (84.1%) could partly account for higher IR of nosocomial pneumonia. The ICU of low resource countries may have to cope with patients with severe illness coupled with the lack of resources and expertise needed to control NI.

Decreasing ICU stay duration and patient days on intervention are important for reducing the incidences of NI.⁶ Furthermore, the resistance pattern is alarming: four of the most common isolates are almost resistant to the third generation cephalosporins, i.e. ceftazidine and cefotaxime. The empirical treatment of choice in serious NI in ICUs would be cefoperazone-sulbactam. A study of antibiotic sensitivity patterns is vital for the effective management of NIs and the decision to use antibiotic cycling to reduce NIs.⁷

Conclusion

It is important to study NIs in developing countries in order to adapt strategies to reduce the risk of NIs and antimicrobial resistance.

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