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Year : 2018 | Volume : 6 | Issue : 3 | Page : 96 - 103  


Original Articles
Ventilator associated pneumonias and its antibiogram

Swati Prakasam1, M. Shailaja Rani2*

1Consultant Microbiologist, Yashoda Hospital, Hyderabad

2Assistant Professor, Malla Reddy Medical College for Women, Suraram, Hyderabad

*Corresponding Author                                                                                                                                   Received: 12-09-2016

Dr. M. Shailaja Rani                                                                                                                                           Accepted: 10-11-2017

Email: drshailumicro@gmail.com

                                                                                               

Abstract:

 

Background: Various studies show Pseudomonas species, Acinetobacter species, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus   were   identified   as common VAP pathogens with varying prevalence. Due  to increasing   incidence  of  MDR in  ICU,  early  and correct  diagnosis  of  VAP  is  a challenge  for  an  optimal  antibiotic treatment.

Objective: To  know  the  Bacteriological  Profile  of  Ventilator associated pneumonias, their  prevalence  and also  their  susceptibility pattern

Methods: The   study   was   conducted   in Intensive Care units in Osmania General Hospital Hyderabad among 300  patients  both  male  and  female  age  group  ranging   from  15- 60  years  admitted  in ICUs. Specimen collection was done by anesthetists, ETA  was  collected  using  8 F suction catheter which  was  guided  through  the  lumen   of   Endotracheal tube  for  approximately  24  cm. Gentle  aspiration  was  then  performed  without  instilling  saline  and  catheter  was  withdrawn  from  endotracheal tube. After  catheter  was  withdrawn  approximately  2.5 – 5 ml  of  saline  was  injected  into  it  with  a  sterile  syringe  to  flush  the  exudate  into  a sterile  container.

Results: The total no. of patients on mechanical ventilation included in the study during one year period was 300.  Out of these 138 patients developed Ventilator Associated Pneumonia (VAP). The most common isolated pathogen was Klebsiella pneumoniae in (40.63%) cases followed by Pseudomonas aeruginosa (15.63%), Acinetobacter species (12.50%) and Staphylococcus aureus (9.38%). Klebsiella pneumoniae was the commonest pathogen isolated in both early onset and late onset. 

Conclusion: The most common isolated pathogen was Klebsiella pneumoniae in (40.63%) cases followed by Pseudomonas aeruginosa (15.63%), Acinetobacter species (12.50%) and Staphylococcus aureus (9.38%).

Key words: Ventilator, pneumonia, antibiogram

Introduction:

 

Pneumonia is the second most common (86%) nosocomial infection in critically ill patients, associated with mechanical ventilation and are termed as Ventilator Associated Pneumonias. Nosocomial pneumonia (NP) is defined as an infection of the lung parenchyma that was neither present nor incubating at the time of hospital admission and which develops after 48 hrs of hospital admission. Ventilator associated pneumonia is defined as pneumonia occurring after 48 hrs of endotracheal intubation and initiation of mechanical ventilation. The onset of VAP can be divided into 2 types: early and late. 1

Early onset VAP: occurs 48 to 96 hours after intubation and is associated with antibiotic susceptible organisms. Late-onset VAP: occurs more than 96 hours after intubation and is associated with antibiotic resistant organisms. 2, 3, 4

Several risk factors reported are duration of mechanical ventilation, presence of chronic pulmonary diseases, sepsis, Acute Respiratory Distress Syndrome (ARDS), neurological diseases, trauma, prior use of antibiotics and red cell transfusions. 5, 6

Mortality rates range from 20-70% when infection is caused by multi resistant and invasive pathogens. Beyond mortality, VAP includes increased length of   stay in ICU and its incremental cost. Delayed or incorrect diagnosis     may lead to unnecessary treatment   and subsequent complications related to therapy. Diagnosis  of  VAP  requires  a  high  clinical   suspicion  combined  with bed  side  examination, radiographic  examination and  microbiological  analysis  of respiratory  secretions. 7

  1. Center for Disease control and Prevention

Radiology  signs: two or more  serial chest radiographs  with  at least one  of  the following: New  or  Progressive  persistent  infiltrate, Consolidation, Cavitation

Clinical signs: At least 1 of the following

  1. Fever (> 38 0 c)
  2. Leucopenia (< 4000 mm3) or Leucocytosis (> 12000 mm3)
  3. Altered mental status, for adults 70 years or older with no other recognized cause

Microbiological criteria: 7

At least one of the following:

Positive  growth  in  blood culture  not  related  to   another  source  of  infection

Positive growth in culture or pleural fluid

Positive quantitative culture from broncho-alveolar   lavage (>104) or PSB (>103)

 5%  or  more  of  cells  with  intracellular  bacteria  on  direct  microscopic examination   of Gram stained  bronchoalveolar  lavage fluid

Histopathological evidence of Pneumonia

Plus at least 2 of the following:

New onset   of purulent sputum, or change in character of sputum

Increased   respiratory secretions or increase   suctioning requirements

New onset or worsening cough, or Dyspnoea or tachypnoea

Rales or bronchial sounds

Worsening gas exchange

Increased oxygen requirements

Microbiological diagnosis:

Methods to obtain culture material from the lower respiratory tracts:-

Non-invasive: Endotracheal aspirate-(standard): Simplest method

Non bronchoscopic techniques

Plugged telescoping catheter (PTC)

Protected bronchoalveolar mini-lavage (mini-PBAL),

Blind Protected specimen brushing

Invasive; Bronchoscopic techniques

             1 .Protected specimen brushing (PSB)

  1. BAL (Bronchoalveolar Lavage),
  2. Open lung biopsy

Various studies show Pseudomonas species, Acinetobacter species, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus   were   identified   as common VAP pathogens with varying prevalence. Due  to increasing   incidence  of  MDR in  ICU,  early  and correct  diagnosis  of  VAP  is  a challenge  for  an  optimal  antibiotic treatment. 8

In   view  of  the above  facts,  the  present  study  on  Bacteriological  Profile  of  VAP  was undertaken and  aimed  at isolating and   identifying  the causative organisms  of  VAP and  their   antibiogram   in  patients  admitted  in  Respiratory  Intensive  Care  Unit  at a tertiary care hospital, Hyderabad

 

Methods:

 

The   study   was   conducted   in Intensive Care units in Osmania General Hospital Hyderabad, a tertiary care centre from 9/9/10-11/9/12

Study group:  300  patients  both  male  and  female  age  group  ranging   from  15- 60  years  admitted  in ICUs

Specimen: endotracheal aspirate

Specimen collection: Specimen collection  is  done  by  Anesthetists, ETA  was  collected  using  8 F suction catheter which  was  guided  through  the  lumen   of   Endotracheal tube  for  approximately  24  cm. Gentle  aspiration  was  then  performed  without  instilling  saline  and  catheter  was  withdrawn  from  endotracheal tube. After  catheter  was  withdrawn  approximately  2.5 – 5 ml  of  saline  was  injected  into  it  with  a  sterile  syringe  to  flush  the  exudate  into  a sterile  container.

Specimen processing: 9 Specimen   was immediately processed. Gram stain  was  done  to consider it as  an  appropriate  sample  more than 10  PMN  neutrophils /HPF, 1 bacteria/  oil immersion  field, Squamous  epithelial  cells  < 1 bacteria/  oil immersion  field, Squamous  epithelial  cells  <  1℅ . Sample   was  mechanically  liquefied  and  homogenized  by  overtaxing   for  2-3  min  with sterile  glass  beads. Samples  were  then  serially  diluted  using  0.9%  sterile  saline solution  with  final  dilution  of  1 in 100  and  1 in 1000.

Dilutions are plated using 4 mm Nichrome   wire loop (Himedia) which holds 0.01 ml sample on to Blood agar, Chocolate agar, MacConkey agar, Sabourads Dextrose agar with antibiotics, without   antibiotics. Inoculated  plates    were  incubated   at 37 0 c for  overnight .Chocolate agar   was  incubated  at  37 0 c  under  5-10% CO2  tension  in a  candle jar. SDA slants were incubated for 1 week   in BOD incubator. All  plates  were  checked  foe  growth  overnight  and  then  after  24-48  hr of   incubation.SDA  slants  were  checked  for  up to  1  week. Colony count of 10 5 cfu/ml   is considered significant. Colony  morphology  was  noted  followed  by  Gram stain and  identification of  the  isolate  was  done  by  conventional  methods. 10 Antibiogram  of  the  isolate   was  done  were  determined  by  Kirby-Bauers Disk Diffusion  method using  Mueller-Hilton  Agar and  the Zone  Diameters were  interpreted  as  per  NCCLS  guidelines.

Results:

 

The total no. of patients on mechanical ventilation included in the study during one year period was 300.  Out of these 138 patients developed Ventilator Associated Pneumonia (VAP). Patients who developed VAP with-in four days of Mechanical Ventilation were categorized as early onset VAP and no. of cases who developed early onset VAP were 60 (43.48%) out of 46 patients. And those who developed after 4 days were categorized as late onset VAP and patients under this category were 78 (56.52%).

The maximum rate of isolated pathogens was in the age group of 31-45 years (32.61%) followed by those in the age group of 46-60 years (30.43%). There was also male preponderance showing 78(56.52%) male cases (56.52%) and 60 (43.48%) female cases. Out of 138 samples which were processed 18 (13.04%) were sterile while bacterial pathogens were isolated in 96 (69.57%) samples and Candida albicans was isolated in 6 (4.35%) samples.  Poly-microbial growth was reported in 18 (13.04%) samples. Among 96 bacterial pathogens obtained majority of them were Gram negative bacteria (90.62%).  The most common isolated pathogen was Klebsiella pneumoniae in (40.63%) cases followed by Pseudomonas aeruginosa (15.63%), Acinetobacter species (12.50%) and Staphylococcus aureus (9.38%). Klebsiella pneumoniae was the commonest pathogen isolated in both early onset and late onset.  Pseudomonas aeruginosa and Acinetobacter species were isolated only in late onset cases.

 

Discussion:

 

Hospital acquired   or  Nosocomial infection   continues  to  be  an  important cause  of  mortality  and  morbidity .Critically  ill  patients  are  at  particular  risk   of  developing  ICU   acquired  infection. Nosocomial   bacterial  pneumonia  occurring  after  2  days   of  mechanical  ventilation  is  associated   with  7  fold  to   21  fold  increase  in  the  incidence  of  Pneumonia  and  28%  of patients  receiving   mechanical  ventilation  will develop  this complication .Its  development  is  associated  with  an  attributable  increase  in  mortality  and  morbidity  .The  establishment  of  an  accurate   diagnosis of  VAP   remains   problematic  and  as  yet  there  is  still   no  accepted  gold  standard  test  for  the  diagnosis  .The  responsible  pathogen  vary  according  to  case  mix, local  resistance  patterns  and  methodology  of  sampling. Keeping  in  view  the  above  facts  , this  study  was  undertaken  to  determine  the  prevalence  of  VAP  , the  common  pathogens  responsible  for  VAP  and  their  resistance   pattern  in  patients  admitted   in  Intensive  Care  Unit  in  a  tertiary  care  centre. The  study  group  comprised  300   patients  who  were   on      mechanical  ventilation  for  more  than  48  hrs. out  of   these  300  patients , 138 patients  are clinically   diagnosed  to  have  developed  VAP(46%), out of which 43.48%(60)  had an early onset   and 56.52%(78)  had  late onset . Studies by  Dey A et al 8 2007 reported  an  incidence of 45.4%   among mechanically ventilated patients  with 47.7% developing early onset  and  52.3% developing  late  onset  VAP. Chawla R 11 (2008)  in  his  comparative   study   of  epidemiology  of  VAP  among  various  Asian  countries  reported  an  incidence  of   33% early onset and 67%  late onset, Set R 12 et al 2011  in  her  study  reported  a higher  incidence  of   late   onset  VAP (68%)   compared  to  early onset (32%). These studies   showed   correlation with the present study.

In  the  present  study  out   of  the  138 patients  56.52% (  75 ) were  males  43.48%   (60)  were   females , showing  higher  preponderance  in  males  which   is  correlating  with  studies  by  Rakshit P et al 13 in 2005 and Manoel J et al 14 2007, Bennani B 7 et al  2008  reported   high  incidence  of  VAP   among  young  adults  which  correlates  with  our  study where 32.61%  of  patients  were  of  31-45  years  age  group  .

Bacteria  were  established   as  the  most  common   etiologic  agents  of  VAP  in  many  of  studies  conducted    worldwide  . In   the present study also bacterial   isolates were more predominant (69.57%). Among all isolates Gram negative   bacteria the most common pathogen responsible for   VAP. Set R et al 12

in  2011  in  their   study  reported  Klebsiella   Pneumoniae  (33.33%)   as  the  commonest  isolate  followed  by  Pseudomonas aeruginosa  (31.25%). In  the  present  study  ,among  Gram negative  bacteria  Klebsiella   Pneumoniae  (40.63%)  was  the  most   common  pathogen  followed  by  Pseudomonas  aeruginosa (15.63%) as  the  second  most  common  isolate. Heyland DK et al 15 in 1999   reported 3.5% occurrence rate of Acinetobacter species. A  study  by  Dey A et  al 8  2007   reported  Acinetobacter  as  the  commonest  agent  of  VAP  in  their  ICU setting  with  a   very   high  incidence  rate  of    48.94% .    However  in  the  present  study  12.50%  of  the  isolates  were  Acinetobacter  species and  it  was  isolated  in  late onset  cases  only  which    was  also  the  same  in  study  by  Rakshit P  et  al 13  in  2005

Staphylococcus aureus  was  the  most  common  Gram positive  cocci  isolated in  studies  by Wu CL et al 16 in 2002 (24%), Wahid F et al 4  in 2005 (20%), Rakshit P et al 13 in 2005, Gacouin A et al 10 in 2009 (21%), In  the  present  study  also  Staphylococcus aureus  was  the  commonest  and  the  only  Gram-positive  cocci   isolated.(9.38%). Wu CL et  al 16  2002   observed  a  single  isolate  each  of  Enterobacter and  Escherichia coli  in  his  study. In  the  present  study  also  a  single   isolates   of   Enterobacter  and  Escherichia coli  were  obtained. Other  Organisms  isolated  in  our  study  were  citrobacter (9.38%)  and  Proteus    mirabilis  (3.23%)  which  were  also  reported  in  studies  by  Heyland DK et al 15 in 1999 and George P et al 17 2010. Pseudomonas putida  was  isolated  in  one  case  which  was  suspected  as  Acinetobacter  species. It  was  later  confirmed  as  Pseudomonas putida  by  Vitek  method  and  was  reported  in  an  elderly  patient  who  is  diabetic. The incidence of polymicrobial flora in our study was 15.55%. Hortal J et al 18 2009 reported 25% incidence. Rakshit P et al 13 in  their  study  found  that   incidence  of  Polymicrobial  flora  was  higher  in  tracheal  aspirate  culture .They  reported   it as 54%. The  incidence   was  found  to  be  varying  in  different  studies  probably  due  to  different    methods of  sample  collection  in  different  studies . Wahid F et al 4 reported 9% incidence of polymicrobial flora in BAL samples. Singhal R et al 19 2005 reported   incidence of 12.3% from BAL samples. Samples   showing   polymicrobial  flora  mostly  compromised  of  mixed  oropharyngeal  growth  with  a  few  colonies  of  pathogenic  flora  and  were  not  processed  further  as  the  patients  were  either  responding    well to   routine antimicrobials  or  were  shifted  from  RICU  to  their  respective  wards.

The  antibiogram  of  Klebsiella pneumoniae  in our  study  showed 100 %  sensitivity  to  imipenem  which  correlated  well  with  studies  Chita L Nazal Matunog et al 20 1993, George P et al  17 2010, Manoel J  et al 14 in 2007, Seth R et al 12 2011, Japoni A et al 21 2011. The  isolates  showed    resistance  to  most  of  the  cephalosporin including  ceftrioxone (100%)  with  moderate  susceptibility  to  ceftazidime (38.47%) and    cefaperazone(53.84%) . This  pattern  was  in  concordance  with  studies by  Maria N et al 22  2010  and  George P et  al 17 2010 .

Pseudomonas  aeruginosa was  isolated  in  5 samples   showed   maximum   sensitivity  to  imipenem ,Piperacillin+ Tazobactum(80%) and  fairly sensitive   to  ceftazidime   and  cefaperazone (80%)  whereas  it  was  resistant  to  Gentamicin(100%) ,  Ciprofloxacin(60%)  . This  was  correlating  with  resistance pattern of  Pseudomonas  aeruginosa  isolates  of  other  studies.  Nazal- Matunog CL et al 20 in 1993   reported 17% resistance to imipenem. Seth R et al 12 2011   reported  10%    resistance  to  Imipenem  and  23.33%  resistance  to  ceftazidime and  20%  resistance  to  cefaperazone. George P et al 17 2010 found that Pseudomonas were sensitive to Imipenem, Piperacillin and cefaperazone.

All  the isolates  of  Acinetobacter  species in  this  study  were  100 %  sensitive  to  Imipenem. Seth R et al 12 2011 also reported 100% sensitivity   to Imipenem. The  isolates  were  showing  100% resistance  to  Gentamicin   which  correlated  with  studies  by  Maria N et al 22 2010. In  the   same  study  33%  resistance  was  reported  against  Piperacillin+ tazobactum .However  in   the    present study  50%  resistance  was  observed  .

Among all Staphylococcus aureus  isolates  one  isolate  was  resistant  to  cefoxitin (30 mcg)and  was  reported  as  MRSA . MRSA  was  reported  in VAP  cases  in  studies  by  Chawla R et al 11 in  2008 (20%), Hortal J   et al 18 (10%)  and  Japoni A  et al 21 (17.2%).

Cefoxitin  disc  was   used  as    studies  by Anand KB et al 23 2009 and Mathews AA et al 24 2010  on  comparison  of  different  screening  methods  for  MRSA  detection  stated  that  results  with  cefoxitin  disc  were  in  concordance  with  PCR results  for  mec A gene. All the three isolates showed excellent sensitivity    to Vancomycin.  Very few studies reported fungal isolates.  Candida  albicans  was  the  only  fungal isolate  seen  in  our  study   which  correlates  with  studies   by  Maria N  et al 22 2010 where  they  reported  Candida spp.

Conclusion:

 

The most common isolated pathogen was Klebsiella pneumoniae in (40.63%) cases followed by Pseudomonas aeruginosa (15.63%), Acinetobacter species (12.50%) and Staphylococcus aureus (9.38%).

 

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