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ORIGINAL ARTICLE
Year : 2008  |  Volume : 2  |  Issue : 2  |  Page : 46-51

Nosocomial pneumonia in mechanically ventilated patients : Prospective study in intensive care unit of Fez university hospital


1 Department of Microbiology, College of Medicine, Fez University, Morocco
2 Department of Epidemiology at College of Medicine, Fez University, Morocco
3 Resuscitation service, Hassan II University, Fez, Morocco

Correspondence Address:
B Bennani
Department of Microbiology, College of Medicine, Fez University.
Morocco
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Source of Support: None, Conflict of Interest: None


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Date of Web Publication18-Jul-2009
 

   Abstract 

Background. Nosocomial organisms remain the leading cause of infection in the intensive care units (ICU) in patients on mechanical ventilation (MV). The risk factors involved are poorly described in the literature. Therefore, we conducted this study to determine the risk factors and antimicrobial sensitivity of bacterial species responsible of nosocomial pneumonia in ICU of Fez University Hospital.
Patients and Methods. Prospective study was conducted in this unit from February to Jun 2007. For
bacteriological analysis, protected distal specimens were used from all mechanically ventilated patients within 48 hr. Clinical and epidemiologic data were collected for all patients and correlated to infection.
Results. Statistical analysis showed that 68.8% of the 44 patients included in this study developed pneumonia. Etiology of infection was marked by the presence of two environmental species: acinobacter baumannii (44%) and pseudomonas aeruginosa (22%) with variable antibiotic sensitivity.
Conclusions. The study period was considered as epidemic for these two species.
Data analysis showed that temperature, abnormal chest-x ray and bronchial expectoration can be used as pneumonia predictor in mechanically ventilated patients in ICU. Risk factors identified in this study were: prophylactic use of antibiotics, duration of ICU admission, environmental factor and patient's status.

Keywords: Antibiotic sensitivity, Risk factors, Ventilator associated pneumonia.


How to cite this article:
Bennani B, Selmani R, Mahmoud M, Nejjari C, Kanjaa N. Nosocomial pneumonia in mechanically ventilated patients : Prospective study in intensive care unit of Fez university hospital. Saudi J Anaesth 2008;2:46-51

How to cite this URL:
Bennani B, Selmani R, Mahmoud M, Nejjari C, Kanjaa N. Nosocomial pneumonia in mechanically ventilated patients : Prospective study in intensive care unit of Fez university hospital. Saudi J Anaesth [serial online] 2008 [cited 2019 Oct 19];2:46-51. Available from: http://www.saudija.org/text.asp?2008/2/2/46/51855


   Introduction Top


NOSOCOMIAL PNEUMONIA OCCURS IN 0.5 to 2 % of hospitalized patients [1] . It remains the first leading type of infection in ICU and seems to be associated with tracheal intubations and MV. The incidence o f ventilator-associated pneumonia (VAP) is ranging between 9 and 68 %, depending on the population studied [1],[2],[3] . However, VAP may occur within the first 48 hr after tracheal intubation. It is usual to distinguish early-onset VAP, which occurs during the first 4 days of MV, from late-onset VAP, which develops >5 days after initiation of MV [4] . The prognosis is better in early-onset than late-onset VAP [5] . Early-onset VAP is most often due to antibiotic sensitive bacteria, whereas late-onset VAP is frequently caused by antibiotic-resistant pathogens [6],[7] . The mortality rate of VAP ranges from 24 to 50 % and can reach as high as 76 % in some specific settings or when caused by high-risk pathogens [5] . The predominant organisms responsible for infection in VAP are Staphylococcus Aureus,  Pseudomonas aeruginosa Scientific Name Search d Enterobacter. However, the incidence of multi-resistant pathogens is closely related to other factors that widely vary from one institution to another according to the population o f patients in an ICU, namely, duration of hospital stay and prophylactic antimicrobial therapy. Therefore, clinicians must clearly be aware of the common microorganisms responsible for early and late-onset VAP in their own hospitals to avoid the administration of non-specific antimicrobial therapy. Current studies in Morocco were mainly focussing on the general aspect of the nosocomial infections and their incidence [8] . There are no studies determining neither the predominant flora responsible for VAP, nor the risk factors associated to this infection in the ICU.

The aim of this study was to determine the bacterial species responsible for VAP and the sensitivity profiles of all isolated species in hospitalized patients within 48 hr in the ICU of Fez university hospital. Also in this study our target was to identify the risk factors associated with VAP in our institution in an attempt to reduce the rate of nosocomial infection.


   Patients and Methods Top


Patients enrolled in this study were recruited from ICU of Fez university hospital which serves as both referral centre and tertiary institution. Hospital ethics committee approval was obtained. Patients admitted in this unit, from February to June 2007, with tracheal intubation and on MV for more than 48 hr were considered eligible for the study. The following variables were recorded from each patient: age, sex, prior surgery, duration of MV and prophylactic antimicrobial therapy. Variables like, temperature, respiratory distress, bronchial expectorations and abnormal chest-x ray have been also recorded. Protected distal specimens (PDS) were used as biological samples. Diagnosis o f pneumonia was considered when PDS cultures were >10 3 cfu/ml. Bacterial identification was made by standard methods and confirmed by the fast appropriate gallery of analytical profile index (API). Antibiotics sensitivity tests were performed according to the recommendations of the French antibiogram committee. Beta-lactamase production was detected using EDTA test inhibition for A.baumanii imipenem resistance strains.

Descriptive analysis of the variables was obtained. Comparison between infection and risk factors were also done using Fisher test. Data Analysis was performed using Epi-Info version 3.4 (USA).


   Results Top


During the study period, 249 patients were hospitalized in our ICU. Only 44 patients (17.67 %) patients who were on MV for more than 48 hr were recruited in the study. They were 38 men (86.36 %) and 6 women (13.64 %) with age average of 40.43 ± 20.44 yr (5 - 80 yr). The average duration of stay in ICU was 5.63 ± 3.89 days. Those patients who were admitted >5 days presented an incidence of 56.81 %. Most of recruited patients were from emergency and neurosurgical departments with incidences of 86.36 % and 11.36 % respectively. All patients had at least one of the clinical parameters suspecting nosocomial pneumonia: temperature > 38°C (45.4%), respiratory distress (77.2%), bronchial expectorations (18.8%) and/or abnormal chest-x ray (34.10%). Twenty nine patients (65.90 %) underwent surgical procedure and 31 patients (70.45 %) had received antimicrobial agent for more than 48 hr. Types of antibiotics used were: Amoxicillin + Clavulanic acid (19.23%); Cefalotin (23.07%); Cefixime (7.69%); Gentamicin (26.96 %); Metronidazole 3.84%. Thirty PDS (68.18 %) were positive in culture, consequently, those patients were considered to have nosocomial pneumonia.

Microbial agents Acinetobacter baumannii (A. baumannii), pseudomonas aeruginosa (P. aeruginosa) and klebsiella pneumoniae Scientific Name Search  (K. pneumoniae) were the most frequently isolated bacteria as shown in [Figure 1]. This frequency varies depending on the time of specimen collection. Isolation of P. aeruginosa and A. baumannii were more isolated in June and April [Figure 2]. Decreasing number o f isolates in May was associated with less number of patients admitted to ICU in that period.

Among the infected patients, A. baumannii has been isolated in 22 specimens (73.3%). The antibiotic sensitivity of the isolated organisms allowed distinguishing two different strains. Those strains were resistant to fluoroquinolons, aminosids and acylureidopenicillins. However the first one was carbapenems sensitive (50 % of isolates) and was isolated during all the study period. While the second one was carbapenem resistant and was isolated during March (25%) and more frequently in May (50%) and June (60%) [Figure 3]. EDTA test have shown that resistance was due in 25% of the cases to mettalobeta-lactamase productions. P. aeruginosa was isolated in 11 specimens (35 % o f infected patients). Antibiotic sensitivity test allowed distinguishing of three different strains. The first one was sensitive to fluoroquinolons, aminosids, acylureidopenicillins and carbapenems, and was isolated during March. The second strain isolated during March, April and June was resistant to these antibiotics except to carbapenems. Whereas, the third strain isolated during May and June was sensitive to acylureidopenicillins and resistant to the others. Frequency of isolation of these strains during the study period is shown in [Figure 4]. K. pneumoniae and E.coli were isolated in ten and one specimens respectively. All isolates showed sensitivity profile characteristic of wild strains. Staphylococcus aureus Scientific Name Search  (S. aureus) was isolated from six patients. The various isolates showed also sensitivity profiles.

Statistical analysis

The young adults (21 - 40 yr) were the most susceptible to develop VAP (84.61 %) [Figure 5]. That susceptibility was higher in women (83.33 %) than in men (65.78 %). Infected patients were hospitalized for longer period than non infected patients, the hospitalisation period were 6.56 days± 4.35 and 3.64 ± 1.27 days (p=0.07) respectively. Early-onset pneumonia was found in 25 % o f infected patients and 43.18% with late-onset pneumonia (?5 days). Most patients (76%) with prolonged hospitalization and ventilatory assistance have been infected versus 57.89% of patients with short duration (<5 days) of hospitalisation. A. baumannii has been isolated in 94.73% and 36.36% of the late-onset and early-onset VAP respectively. The levels of P .aeruginosa detected in these two groups were 42.1% and 27.27% respectively. Fever, chest-x ray, bronchial expectorations and acute respiratory distress syndrome (ARDS) were positively correlated with the microbiological results. ARDS showed negative correlation to microbiological results [Table 1]. Among post surgical patients, 86.2 % were infected versus 13.7% not infected. Comparable results were obtained with patients under antibiotic therapy, where 83.8% were infected versus 16.1% were not infected [Table 2].


   Discussion Top


In the current study, the incidence of VAP was found to be 68.18 % which does not exceed those reported incidences in European hospitals [9],[10],[11] . Also we have found positive correlation between fever and pneumonia as well as between chest-x ray abnormality and pneumonia. The same results were obtained for bronchial expectoration and pneumonia. In our study, the rate of infected patients with prior ARDS is comparative to those described in other studies (<70%) [12],[13] . The three clinical signs: temperature, abnormal chest-x ray and bronchial expectoration can be used as predictors o f nosocomial pneumonia. It would be also interesting to establish a relation between the clinical score o f lung infection and the results of the bacteriological analysis. Risk factors provide information about the probability of lung infection in individuals. Thus, they may contribute to the establishment of preventive strategies by indicating which patients might be most likely to benefit from prophylactic antimicrobial therapy against pneumonia [9],[14] . The age (>60 years) is minor risk factor of VAP in the ICU [15] . In the present study, correlation between VAP rate and age showed that young adults (21 - 40 years) are the most infected with 84.61 % of positive cases. This tendency could be explained by the severity of the trauma occurring more frequently among younger subjects before admission to ICU. Studies on the relationship between the cumulative risks of pneumonia due to prolonged MV showed controversy but concluded that this risk increased over time [14],[16] . In our study, 63.3% of infected patients were on MV (average 6.56 days) and developed late-onset pneumonia, versus 57% with shorter duration. Effectively, during the stay in ICU, patients had prolonged contact with the hospital environment; this has led to an increased risk o f exogenous infection. This finding is confirmed by the isolation rates of two germs from most of the cultures: A. baumannii and P. aeruginosa, which are indicators of this type of contagion. In our series, A. baumanii and P. aeruginosa has been isolated 2.6 and 1.5 times more frequently in late-onset than in early-onset pneumonia respectively. These findings confirm that those species especially A. baumanii are more frequently isolated in late-onset pneumonia. It was demonstrated that post-surgical patients are at high risk for VAP, they account for nearly one-third of the pulmonary infiltrates in ICU patients [17],[18] . Cardio-thoracic surgery, neurosurgery, and trauma (particularly head trauma) patients were more likely to develop VAP than other types of surgical patients [14],[19],[20] . Our results supported those studies since 86.2 % of post-surgical patients developed nosocomial pneumonia and have neurosurgery or trauma. Thereby, post-surgery can be considered as risk factor with developing VAP. In accordance with other studies, more than 60% o f respiratory infections in the ICU were caused by aerobic GBN with predominance of P. aeruginosa followed by enterobacter and acinobacter [21],[22],[23],[24],[25],[26],[27] . In our ICU 74.19% of patients under prophylactic antibiotic therapy developed VAP with isolated A. baumannii and / or P. aeruginosa. Antibiotic use and duration of stay in ICU could not alone explain the high rate of A. baumannii (44 % in our study versus 18% in others). Effectively, the same species with the same antibiotic sensitivity profiles has been isolated when analysing 12 sites (medical instruments, patient's bed) of hospital environment in the same period. Those strains were also isolated in patients with nosocomial urinary infection. Those data and high rate of this species between March and July support the epidemic characters associated with A. baumannii in this period. This distribution pattern of etiologic factors responsible of VAP in our ICU can be explained by several risk factors: prophylactic use of antibiotics, duration, exogenous contagion, and patient's status. Those factors also explain the high rate of polymicrobial infection in VAP (56.66%), which varies in other studies from 13% to 40% [21],[28] . The incidence of multi­resistant pathogens is also closely linked to local factors and varies widely from one institution to another. During the period of our study, the isolated bacteria showed variable sensitivity profiles. Over isolated A. baumanii, 50 % were imipenem resistant; this rate is higher than those detected in Moroccan military hospital (31 %) and explain epidemic infection [29] . Concerning P. aeruginosa, the three strains obtained have different antibiotic sensitivity profiles. The antibiotic resistance profiles of P. aeruginosa were comparable to those reported in other studies [30],[31] . The imipenem resistant P. aeruginosa strains were isolated in May and June. That could explain that imipenem resistance has been transferred from one species to another, probably from A. baumanii to P. aeruginosa and also support epidemic character of infection. During the study period, no acquired resistance was recorded with K. pneumonia isolates. While isolation of ESBL strains have been reported in other ICU: Morocco [31] , Turkey [32] and in France during an epidemic time (25 % of isolates) [33] . Curiously, no S. aureus methicillin-resistant strains were isolated in our study, while their rate varies between 30 and 50 % in France [31] . This is probably due to the low frequency of their isolation (6 isolates). In our ICU, the incidence of VAP (68.18 %) doesn't overtake those described in the other national and international hospitals. Certainly, this rate and the aetiology were influenced by several risk factors especially environmental contamination and prophylactic antibiotic administration before bacteriological diagnosis.

In conclusion, this study emphasized the major influence of the underlying medical and environmental conditions on the epidemiologic characteristics of VAP. Also it showed the interest of implementing a national and pertinent surveillance program in the ICU which will help clinicians to be aware of the common microorganisms associated with VAP and to be more oriented with the application o f decontamination procedures and proper antimicrobial therapy.

 
   References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

  [Table 1], [Table 2]



 

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