A Study on Incidence, Etiology and Susceptibility patterns of microorganisms causing Ventilator - Associated Pneumonia (VAP) in tertiary care hospital

 

Manish G Patel¹, Snehal², Paresh M Patel³, Rajeev Kumar^4*, Mannu R Jain⁵

 

Abstract              Background: In spite of the advances in the diagnosis, treatment and prevention of VAP, it continues to complicate the course of 7 to 41% of patients receiving continuous mechanical ventilation and is a major cause of morbidity and mortality among critically ill patients.1 This study is conducted to know the Incidence, Etiology and Susceptibility patterns of microorganisms causing Ventilator–Associated Pneumonia (VAP) in tertiary care hospital. Methods: This is a prospective study done on total 230 patients of all age group and gender who received mechanical ventilation for more than 48 hours admitted to the various intensive care units of SMIMER hospital from January 2016 to July 2016. Sample received form these cases were processed as per standard microbiology protocol (Gram stain, Culture, AST) Results: Out of 230 patients, 92 (40%) were detected with ventilator associated pneumonia (clinical pulmonary infection score >6). Out of the 92 VAP cases, 26.08% (24/92) were having early-onset and 73.92% (68/92) under the late-onset VAP. Polymicrobial VAP was found in 34.78% cases and monomicrobial in 65.22% cases. The most common organisms was Acinetobacter spp. 41(33.33%) followed by Klebsiella pneumonia 35(28.45%) and Pseudomonas spp. 26(21.13%). Conclusion: This study highlights the need for active surveillance for VAP in all ICU setups as the incidence of patients who are being admitted to ICU and requiring mechanical ventilation is increasing.

 

INTRODUCTION

Ventilator associated pneumonia is defined as pneumonia occurring in patients admitted to critical care units for more than 48 hours after endotracheal intubation and initiation of mechanical ventilation.¹ It is classified as either early onset (occurring within 96 hours of start of mechanical ventilation) or late onset (>96 hours after start of mechanical ventilation).¹

In spite of the advances in the diagnosis, treatment and prevention of VAP, it continues to complicate the course of 7 to 41% of patients receiving continuous mechanical ventilation and is a major cause of morbidity and mortality among critically ill patients.¹ VAP prolongs the duration of hospitalization for an average of 7–9 days per patient, and it is associated with increased health care costs. The crude mortality rate for VAP has been cited to be as high as 70%.² Early-onset VAP, which occurs during the first four days of MV(Mechanical Ventilation), usually is less severe, associated with a better prognosis, and is more likely to be caused by antibiotic sensitive bacteria than late-onset VAP which develops five or more days.³ Aerobic Gram negative bacilli such as Pseudomonas spp., Acinetobacter spp., Escherichia coli, Klebsiella pneumoniae and Gram positive like Staphylococcus aureus were identified as the common VAP pathogens, with varying prevalence.³ Pseudomonas spp., Acinetobacter spp. and even Enterobacteriaceae are quite often multidrug-resistant due to production of extended spectrum beta (β)-lactamases (ESBL), AmpC β-lactamases (AmpC) or metallo-β-lactamases (MBL).³ The etiological agents of VAP vary with different patient populations and types of ICUs. Therefore, the local microbial flora causing VAP needs to be studied in each setting to guide more effective and rational utilization of antimicrobial agents. Detection of the causative organism is crucial for the diagnosis and treatment of VAP. This is done by collecting the lower respiratory tract samples either by invasive (protected specimen brush PSB or broncho-alveolar lavage BAL) or non-invasive (endotracheal aspirate) technique and culturing quantitatively or semi quantitatively. There are many studies which compared the diagnostic value of semi-quantitative cultures of bronchoscopic and non-bronchoscopic samples in VAP. No technique could consistently be shown to achieve a superior diagnostic yield as compared to another.4

 

AIM AND OBJECTIVES

To determine the incidence of ventilator associated pneumonia (VAP). To determine the etiological organisms of ventilator associated pneumonia. To study the Antimicrobial Susceptibility profile of these organisms. To determine the prevalence of multidrug resistant (MDR) organisms.

 

MATERIAL AND METHODS

Study Area: SMIMER Medical College and Hospital, Surat, Gujarat

Study Design: Prospective study.

A prospective Study was performed on 230 patients of all age group and gender admitted to the various intensive care units of SMIMER hospital (from January 2016 to July 2016) and who had been receiving mechanical ventilation for more than 48 hours. Clinically diagnosed Ventilator Associated Pneumonia cases were observed and data such as age, gender, date of admission, risk factors involved, under lying diseases, date of intubation/tracheostomy, duration of mechanical ventilation, etc. were obtained. Endotracheal aspirate was obtained under aseptic precautions by using a K-90 suction catheter with a mucus extractor. After this, 2ml of 0.9% saline was injected in the endotracheal tube with a sterile syringe to flush the exudates into a sterile container. Each specimen processed in bacteriology laboratory as per standard microbiology protocol by performing Gram stain and culture on blood agar and MacConkey agar to isolate the pathogen. The bacterial isolate were further identified by using colony characteristics, gram stain and standard biochemical reactions as per CLSI guidelines.⁵ Antibiotic sensitivity of isolates was tested using the modified Kirby Bauer disc diffusion method on Muller-Hinton agar according to CLSI guidelines.

 

RESULTS

In present study of 230 patients, 92 (40%) were detected with clinical pulmonary infection score of more than six and were diagnosed as ventilator associated pneumonia during their ICU stay.

 

TABLE 1: NUMBER OF CASES ENROLLED

 

Patients developing VAP within 96 hours of mechanical ventilation were categorized as having “early-onset VAP". Out of the 92 VAP cases, 26.08% (24/92) were categorized under the early-onset group and the remaining 73.92% (68/92) under the late-onset group.

TABLE 2: ONSET OF VAP

 

Among 92 cases who developed VAP in various ICUs, 41.3% (38/92) were in MICU, 26.09% (24/92) in ICCU, 18.48% (17/92) in NICU, 7.61% (7/92) in PICU, and 6.52% (06/92) were in SICU.

TABLE 3: INCIDENCE OF VAP AMONG VARIOUS ICUs

 

TABLE 4: DISTRIBUTION OF CAUSATIVE ORGANISMS ON THE BASIS OF MONOMICROBIAL vs. POLYMICROBIAL AMONG VAP PATIENTS.

Table 8: Outcomes of VAP

 

The observed mortality rate associated with VAP was 50% (46 out of 92 cases).Out of 46 deaths 07 were seen in early onset VAP and 39 were seen in late onset VAP. It was observed that more number of deaths was seen in late onset of VAP.

 

CONCLUSION

This study highlights the need for active surveillance for VAP in all ICU setups as the incidence of patients who are being admitted to ICU and requiring mechanical ventilation is increasing. Knowledge of incidence of VAP, their causative microbial flora in a local setting along with information on the susceptibility patterns will help in selection of the appropriate antibiotic for therapeutic use and a better outcome. This will also prevent indiscriminate and irrational use of antibiotics which contribute to emergence of drug resistance strains in the environment. The susceptibility patterns will help us in evolving an antibiotic policy and also in controlling hospital infection. It would also allow formulation of strategies to decrease the incidence of multi-drug resistant VAP by putting into practice a system of performing a root cause analysis on these cases and emphasis the need to take corrective and preventive measures to reduce this hospital acquired infection which will help in reducing the morbidity and mortality of patients admitted to intensive care settings and also reduce the burden of health care costs. Prompt and early diagnosis of pneumonias would however be the mainstay in bringing down mortality. Endotracheal aspirate samples have been found to be very useful in isolation of etiological agents and should be sent to the clinical microbiology lab as early as possible in a patient on mechanical ventilation more than 48hours.

 

REFERENCES

1. R.M. Saldanha Dominic et al. A clinico-microbiological study of ventilator-associated pneumonia in a tertiary care hospital. Int J Biol Med Res. 2012; 3(2):1651-1654
2. De Rosa FG, Craven DE. “Ventilator-associated pneumonia: current management strategies. Infectious Medicine” 2003; 20(5):248–259.
3. Joseph NM, Sistla S, Dutta TK, Badhe AS, Parija SC (2009) Ventilator-associated pneumonia in a tertiary care hospital in India: incidence and risk factors. J Infect Dev Ctries 3: 771-777.
4. Usman SM et al. associated Clinical and microbiological facets of ventilator associated pneumonia; Int J Res Med Sci. 2014 Feb;2 (1):239-245
5. Clinical Laboratory Standards Institute “Performance standard for antimicrobial disk susceptibility tests”. Guide line 2014.

 

 

 

 

 

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