Uncommon non-fermenting Gram-negative bacillary bacteraemia in ICU patients*

Recently, in this journal, a report from Thessaloniki, Greece showed an alarming increase of multidrug-resistant Gram-negative bacteria in patients hospitalized in an intensive care unit (ICU) [1]. In particular, Acinetobacter baumannii, Klebsiella pneumoniae and Pseudomonas aeruginosa were frequent drug-resistant species. We here wish to contribute with our experience on uncommon non-fermenting Gram-negative bacillary (NFGNB) bacteraemia in critically ill patients, which are resistant to commonly used antimicrobials in the ICU. Patients who developed these infections after prolonged exposure to antimicrobials had poor survival. This retrospective observational was done in a 20 bed medical ICU in a tertiary care hospital in North India during the period of September 2016 to August 2018. After institute ethical committee (IEC) approval (2018-125-IPEXP), electronic-based data records were searched for all blood cultures done during the study period to identify those which showed growth of NFGNB (other than Pseudomonas and Acinetobacter species) in adult patients admitted in ICU. Demographic and clinical data of the patients were noted through structured proforma, from patient medical records and electronic database of the hospital information system. Blood samples collected for culture and sensitivity in patients with clinical suspicion of sepsis. 8–10ml of blood was collected by nursing personnel using strict aseptic precautions in BACTEC bottles (BD Diagnostics, Sparks, MD) followed by subculture on blood agar and MacConkey agar plates. The isolated bacteria were subjected to identification by MALDI–TOF (matrix-assisted laser desorption ionisation–time of flight mass spectrometry) and antibiotic susceptibility testing by VITEK-2 automated system (Biomeriux, France). Results of antibiotic susceptibility testing were interpreted as per the Clinical and Laboratory Standards Institute guidelines 2016. The patient treatment was modified in accordance with blood culture report by treating physician. Descriptive statistics of the continuous variables were presented using median (Inter-quartile range ‘IQR’) while categorical variable in frequency (%). To compare the distribution of continuous variable between survivors and non-survivors, Mann–Whitney U-test was used, while proportions were compared using Fisher’s exact test. As sample size was small, Cohen’s d (effect size) was also estimated between two quantitative values. Effect size (d) which is ratio of mean difference and pooled standard deviation between the groups, considered small size ( 0.2), medium size (>0.2 to <0.5) and large size ( 0.5) respectively. Effect sizes that are large but not significant may suggest further research with greater power, simultaneously assessing whether statistically significant values are being overvalued because of huge sample size [2]. Data were analysed using software Statistical package for social sciences, version-23 (SPSS-23, IBM, Chicago, USA). p value < . 05 considered as statistically significant. During the study period, 3516 blood cultures were processed from 587 ICU patients, of which 172 patients showed bacterial growth. A majority of the isolates (67%) were Gram-negative bacilli and among them, only 1.5% isolates were non-fermenting Gram-negative bacilli other than Pseudomonas and Acinetobacter species. Uncommon NFGNB were isolated on more than one occasion from 15 patients. The median age of the patients was 48 (31–63) years and 12 were males (Table 1). At admission, ICU severity scores (median) were APACHE II 22 (18.25–28) and SOFA 11 (8.25–16).