|Year : 2014 | Volume
| Issue : 3 | Page : 162-166
Prevalence of non-fermenting Gram-negative bacilli and their in vitro susceptibility pattern at a tertiary care teaching hospital
Kirtilaxmi K Benachinmardi, M Padmavathy, J Malini, BV Naveneeth
Department of Microbiology, Employees' State Insurance Corporation Medical College and PGIMSR, Bengaluru, Karnataka, India
|Date of Web Publication||19-Sep-2014|
Kirtilaxmi K Benachinmardi
Department of Microbiology, Employees' State Insurance Corporation Medical College and PGIMSR, Rajajinagar, Bengaluru - 560 010, Karnataka
Source of Support: None, Conflict of Interest: None
Background: Aerobic non-fermenting Gram-negative bacilli (NFGNB) once considered as contaminants now associated with life-threatening infections and emerging as multi drug resistant nosocomial pathogens. Aim: Isolation and identification of NFGNB in all the clinical samples and to determine antibiotic susceptibility pattern of the isolated NFGNB. Materials and Methods: This study has been conducted in the Department of Microbiology at a tertiary care teaching hospital over a period of 2 months from September to October 2013. NFGNB were isolated and identified from clinical specimens by standard procedure and antibiotic sensitivity test was performed. Results: NFGNB isolation rate in the present study was 3.58%. Male to female ratio was 2.125. Pus was the most common specimen (21%) followed by tracheal aspirate (17%). Pseudomonas aeruginosa was the most common isolate (60%) followed by Acinetobacter baumannii (22%) and Acinetobacter lwoffii (12%). P. aeruginosa has shown good sensitivity to amikacin (83.3%), imipenem (80%) and piperacillin-tazobactam (73.3%) whereas A. baumannii showed multidrug resistance. Conclusion: It is necessary to identify NFGNB and to monitor their susceptibility pattern to guide the clinician for better care and management of patients. NFGNB are now emerging as organisms of nosocomial infections. Hence, antibiotic sensitivity testing and infection control measures are needed to prevent the emergence and spread of multi drug resistant NFGNB in health care settings.
Keywords: Acinetobacter baumannii, Acinetobacter lwoffii, non-fermenting Gram-negative bacilli, Pseudomonas aeruginosa
|How to cite this article:|
Benachinmardi KK, Padmavathy M, Malini J, Naveneeth B V. Prevalence of non-fermenting Gram-negative bacilli and their in vitro susceptibility pattern at a tertiary care teaching hospital. J Sci Soc 2014;41:162-6
|How to cite this URL:|
Benachinmardi KK, Padmavathy M, Malini J, Naveneeth B V. Prevalence of non-fermenting Gram-negative bacilli and their in vitro susceptibility pattern at a tertiary care teaching hospital. J Sci Soc [serial online] 2014 [cited 2020 Sep 22];41:162-6. Available from: http://www.jscisociety.com/text.asp?2014/41/3/162/141204
| Introduction|| |
Aerobic non-fermenting Gram-negative bacilli (NFGNB) are taxonomically diverse group of non-sporing bacilli that either do not utilize glucose as a source of energy or utilize it oxidatively.  Basically, they are saprophytes and previously they were considered as contaminants or commensals of little significance. , However, recent literature review shows that these organisms are now associated with life-threatening infections such as septicemia, pneumonia, urinary tract infection, meningitis, surgical site infection, ventilator associated pneumonia (VAP), wound infection, osteomyelitis etc.  They account for around 15% of all bacterial isolates from clinical samples.  Routinely they are identified only in few laboratories in India as they are slow growing and require special culture media and biochemical tests for their identification.  Due to rampant use of antibiotics most of these organisms are now resistant to many routinely used antibiotics causing prescription failure.  Hence, this study was undertaken to isolate and identify NFGNB and also to characterize the antibiotic susceptibility pattern at a tertiary care teaching hospital.
Aims and objectives
1. Isolation and identification of NFGNB in all the clinical samples.
2. To determine antibiotic susceptibility pattern of the isolated NFGNB.
| Materials and methods|| |
This prospective study has been conducted in the Department of Microbiology at a tertiary care teaching hospital over a period of 2 months from September to October 2013. All the samples received in bacteriology section of laboratory were inoculated on blood agar, MacConkey agar and incubated at 37°C for 48 h before being reported as sterile. The isolates which were non-lactose fermenting and showed alkaline/no change (K/NC) reaction on triple sugar iron agar were provisionally considered as NFGNB and they were further identified using standard protocol for identification.  The various tests were Gram stain for morphology, hanging drop for motility, oxidase test, catalase test, citrate utilization, oxidative-fermentative test (Hugh-Leifson medium) for glucose, lactose, sucrose, maltose, mannitol and xylose, utilization of 10% lactose, gelatin liquefaction, lysine and ornithine decarboxylation, arginine dihydrolase test, growth at 42°C and 44°C.
Antimicrobial sensitivity was determined by Kirby-Bauer disc diffusion method on Mueller Hinton agar using commercially available antimicrobial discs (Hi-media). The different antimicrobials tested were piperacillin (100 μg), ceftazidime (30 μg), gentamicin (10 μg), piperacillin-tazobactam (100/10 μg), imipenem (10 μg), amikacin (30 μg), ciprofloxacin (5 μg) and cotrimoxazole (1.25/23.75 μg). The results were interpreted as per Clinical and Laboratory Standard Institute guidelines.  Controls used were Escherichia More Details coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853.
| Results|| |
A total of 2793 samples were received for culture and sensitivity during the study period, among which 100 NFGNB were isolated accounting for an isolation rate of 3.58%. Age of our cases ranged from day 4 to 80 years, males were 68 and females were 32 with male to female ratio of 2.125. Maximum number of cases were observed in the age group of 21-30 years (20) and 41-50 years (20). The age and sex distribution is shown in [Figure 1].
|Figure 1: Bar diagram showing age and sex distribution of isolated non-fermenting Gram-negative bacilli|
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Pus was the most common specimen accounting for 21% followed by tracheal aspirate (17%), sputum (16%), ear swab (14%), catheter tips (12%), urine (11%), blood (7%) and vaginal swab (2%). Among the NFGNB isolated P. aeruginosa (60%) was the most common followed by Acinetobacter baumannii (22%), Acinetobacter lwoffii (12%), Sphingobacterium spp. (3%) and Pseudomonas stutzeri, Flavobacterium spp. and Stenotrophomonas maltophila (1%) each [Table 1]. The clinical samples from inpatients yielded more number (39%) of NFGNB than out patients (24%) [Table 2].
|Table 2: NFGNB isolated from outpatient, inpatient and intensive care unit|
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The antibiotic sensitivity pattern of NFGNB is shown in [Table 3] and [Table 4]. Most of the isolates of P. aeruginosa showed highest sensitivity to amikacin (83.3%) and least sensitivity to piperacillin (38.3%). A. lwoffii were also sensitive to most of the drugs. Flavobacterium, S. maltophila and P. stutzeri showed 100% sensitivity to all the antibiotics. However A. baumannii and Sphingobacterium were resistant to most of the drugs.
| Discussion|| |
Although NFGNB are considered commensals or contaminants, their pathogenic potential has been well-established by their frequent isolation from clinical samples and their association with clinical disease. The outbreaks of nosocomial infections, emerging antimicrobial resistance and epidemiological complexity have made NFGNB the remarkable organisms. In the recent years, they have emerged as important nosocomial pathogens and resistance to antimicrobials has increased over the years.  NFGNB are innately resistant to many antibiotics and are known to produce extended spectrum beta-lactamase and metallo-beta-lactamase. 
Risk factors for NFGNB to emerge as nosocomial pathogens are immunosuppression (cancer patients on cytotoxic therapy, radiotherapy, organ transplant patients, acquired immune deficiency syndrome patients and patients on antimicrobial therapy), neutropenia, mechanical ventilation and cystic fibrosis, indwelling catheters, invasive diagnostic and therapeutic procedures. Prolonged hospital stay, indiscriminate use of broad spectrum antibiotics and underlying host factors also contribute to morbidity and mortality. 
Most commonly occurring NFGNB are P. aeruginosa, Acinetobacter spp., Stenotrophomonas spp., S. maltophila, Alcaligenes spp., Flavimonas, Oryzhihabitans, Sphingobacterium, Burkholderiaspp., Cepacia, Acromobacter spp., Bordetella spp., Commamonas spp., Methylobacterium spp., Olizella spp., Ralstonia spp., Psychrobacter spp., Roseomonas spp., Shewanella spp., Sphingobacterium spp., Elizabethkingia spp. 
In our study prevalence of NFGNB was 3.58% which is in parallel to studies by Malini et al.  and Bruno et al.  whose isolation rate was 4.5% and 2.18% respectively. On the other hand, Samanta et al.  Eltahawy and Khalaf  Vijaya et al.  and Sidhu et al.  have reported higher rate of isolation i.e., 10%, 16%, 21.80% and 45.9% respectively. Most of the isolates in our study were from pus samples as observed in other studies. ,,, NFGNB isolated from in-patient was more than out-patient as seen in studies by Jayanthi and Jeya  and Juyal et al.  It was observed that P. aeruginosa was the commonest non-fermenter followed by Acinetobacter spp. and this is in concordance with other studies and is depicted in [Table 5].
|Table 5: Isolation rate of Pseudomonas species and Acinetobacter species in various studies|
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The world-wide resistance pattern of nosocomial pathogens shows wide variation from country to country and within the same country over a period of time.  Proper identification and detection of antibiotic sensitivity pattern is of great value because of high intrinsic resistance of different NFGNB to different antimicrobial agents. Therefore, various international authorities emphasize that every hospital should have antibiotic policy of its own. 
In our study, it was observed that P. aeruginosa isolates were sensitive to most of the antibiotics as seen in other studies, amikacin being the highest (83.3%). ,, In contrast to other studies who found 60-70% resistance to amikacin, ceftazidime and ciprofloxacin. ,, Imipenem resistance was seen in 20% isolates of Pseudomonas in our study whereas Gladstone et al.,  Hodiwala et al.,  Gupta et al.,  and Malini et al.,  detected 42.8%, 21%, 20% and 6% respectively.
Over 70% of strains of Acinetobacter spp. isolated showed resistance to various antibiotics similar to other studies. ,, However, imipenem was comparatively sensitive (57.14%) as observed in other studies. ,,, Higher resistance pattern was observed in A. baumannii when compared with A. lwoffii. A. baumannii is gaining more attention now-a-days due to potential ability to form biofilm, this may also explain its outstanding antibiotic resistance, survival properties and increased virulence. 
| Conclusion|| |
P . aeruginosa and A. baumannii are the most commonly isolated NFGNB in our study. Their role as health care associated pathogen is well-established and they are associated with wound infection, urinary tract infection, septicemia, surgical site infection and VAP. P. seudomonas has shown good sensitivity to amikacin, imipenem and piperacillin-tazobactam. A. baumannii shows higher degree of resistance pattern to various antibiotics suggesting multidrug resistance. The different species of NFGNB have shown a varied sensitivity pattern as already discussed above. Hence, it is necessary to identify NFGNB and to monitor their susceptibility pattern to guide the clinician for better care and management of patients. Moreover, NFGNB have great potential to survive in hospital environment therefore improved antibiotic stewardship and infection control measures are needed to prevent emergence and spread of multi drug resistant NFGNB in health care settings.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]
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