|Year : 2014 | Volume
| Issue : 3 | Page : 140-144
Bacterial and antimicrobial resistance profile of bloodstream infections: A hospital-based study
Amit Kumar Singh1, Vimala Venkatesh2, Ravinder Pal Singh3, Mastan Singh2
1 Department of Microbiology, Mayo Institute of Medical Sciences, Barabanki, Uttar Pradesh, India
2 Department of Microbiology, King George's Medical University, Lucknow, Uttar Pradesh, India
3 Department of Microbiology, Gold Field Institute of Medical Sciences and Research, Faridabad, Haryana, India
|Date of Web Publication||17-Aug-2014|
Amit Kumar Singh
Department of Microbiology, Mayo Institute of Medical Sciences, Barabanki - 225 003, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Background: Bloodstream infections (BSIs) are one of the serious infections causing significant morbidity and mortality among hospitalized patients. Large numbers of cases of treatment failure are being reported due to emergence of drug resistance. Early microbiological diagnosis and determination of antimicrobial susceptibility pattern have been shown to improve treatment outcome. The present study was aimed to determine the bacterial and antimicrobial resistance profile of BSIs in a major tertiary care hospital. Materials and Methods: Blood samples in brain heart infusion (BHI) broth submitted to the microbiology laboratory for culture and sensitivity during a period of 1 year were included in the study. Samples were processed as per standard protocol of laboratory for isolation and identification. The antimicrobial susceptibility profile of bacterial isolates was determined by the disc diffusion method as per Clinical and Laboratory Standards Institute (CLSI) guidelines. Results: Out of 4862 blood samples, 494 (10.16%) isolates were obtained. Of these isolates, 256 (51.82%) were Gram-negative and 230 (46.56%) were Gram-positive bacteria. The most commonly identified organism was coagulase-negative Staphylococcus (CoNS) (25.91%) followed by Acinetobacter spp. (20.24%) and Escherichia coli (14.98%). Gram-negative bacteria showed a higher rate of resistance as compared with Gram-positive bacteria. Conclusion: High prevalence of antimicrobial resistance was noted in this study, especially in Gram-negative bacteria. Hence, appropriate treatment of BSIs should be based on the current knowledge of bacterial resistance profile as provided by microbiology laboratory. It would be advisable for the clinicians to mandate antimicrobial sensitivity testing for suspected cases of BSIs.
Keywords: Antimicrobial resistance profile, bacterial profile, bloodstream infections
|How to cite this article:|
Singh AK, Venkatesh V, Singh RP, Singh M. Bacterial and antimicrobial resistance profile of bloodstream infections: A hospital-based study. CHRISMED J Health Res 2014;1:140-4
|How to cite this URL:|
Singh AK, Venkatesh V, Singh RP, Singh M. Bacterial and antimicrobial resistance profile of bloodstream infections: A hospital-based study. CHRISMED J Health Res [serial online] 2014 [cited 2019 Nov 20];1:140-4. Available from: http://www.cjhr.org/text.asp?2014/1/3/140/138881
| Introduction|| |
Bloodstream infections (BSIs) are one of the most significant cause of morbidity and mortality among hospitalized patients.  It is a serious challenge for health care professionals in prescribing suitable antimicrobial therapy. Factors that may lead to BSIs include increased use of indwelling intravenous catheters, overstay in intensive care units, increased use of steroids and immunomodulators, improved treatment of human immunodeficiency virus (HIV) infections, and changing pattern of antimicrobial usage. , BSIs are often complicated with syndromes associated with septic shock.  Development of resistance to antimicrobial agents further adds complication to its proper treatment outcome. Various studies from India and worldwide have reported an increased antimicrobial resistance among bacterial isolates causing BSIs. ,,,
Wide range of organisms have been isolated in BSIs, which include Acinetobacter spp., Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae among Gram-negative bacteria and coagulase-negative staphylococci (CoNS), Staphylococcus aureus, enterococci, and alpha-hemolytic streptococci among Gram-positive bacteria. The predominance of organisms varies from center to center with different antimicrobial resistance profile. ,, Early identification of bacterial isolates and their antimicrobial susceptibility pattern for rapid administration of antimicrobial therapy to the patients of BSIs have been shown to improve treatment outcome.  Therefore, for better results of treatment of BSIs, it is important to review its epidemiology and update the antimicrobial resistance profile to determine the appropriate empirical antimicrobial therapy for the region.
The present study was therefore aimed to determine the prevalence of various bacterial isolates causing BSIs and their antimicrobial resistance profile in a major tertiary care hospital to assist the health care professionals to choose an appropriate antimicrobial therapy for treatment of BSIs.
| Materials and Methods|| |
Blood samples in brain heart infusion (BHI) broth submitted to the bacteriology laboratory, Department of Microbiology, King George's Medical University, Lucknow, India from various inpatient departments of Gandhi Memorial and Associated Hospitals, Lucknow, India for culture and sensitivity during a period of 1 year from July 2011 to June 2012 were included in the study. Samples were incubated aerobically at 37 o C in an incubator for 16-18 h. After incubation, primary subculture from the BHI broth was done on 5% blood agar and MacConkey agar and repeated daily till 7 days. The culture was reported negative if all subcultures showed no growth by the end of 1 week. Growth obtained during any of the subculture done on 5% blood agar or MacConkey agar was included in the study. Isolates were further processed as per standard routine protocol of the laboratory for its complete identification as described in the [Table 1]. The organism grown on any of the culture media was included in the study if respective BHI broth was turbid and the smear prepared from broth and culture media showed the same organism; otherwise it was not included in the study.
The antimicrobial susceptibility profile of bacterial isolates was determined by the Kirby-Bauer disc diffusion method as per Clinical and Laboratory Standards Institute (CLSI) guidelines.  The antibiotics discs used for different Gram-positive and Gram-negative organisms are listed in the [Table 2]. Culture media and antibiotic discs used in the study were obtained from HiMedia Labs Pvt Ltd, India.
| Results|| |
Out of 4862 blood samples received during a period of 1 year, 494 (10.16%) isolates were obtained. Of these isolates, 256 (51.82%) were Gram-negative and 230 (46.56%) were Gram-positive bacteria [Table 3]. The most commonly identified organism was CoNS (25.91%) followed by Acinetobacter spp. (20.24%) and E. coli (14.98%) as demonstrated in [Table 4]. Other organisms that were isolated include Enterococcus fecalis (11.74%), S. aureus (6.88%), P. aeruginosa (5.67%), and K. pneumoniae (5.26%). Rest of the isolated organisms have been described in [Table 4].
|Table 3: Percentage distribution of gram-positive,|
gram-negative, and Candida spp. isolates among total
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Antimicrobial resistance profile of different isolates is documented in [Table 5]. Gram-positive bacteria were more resistant to ampicillin (67.2%) followed by septran (50.9%). Methicillin resistance was seen in 31 and 57.1% of CoNS and S. aureus, respectively. Vancomycin and linezolid showed a uniform sensitivity to all Gram-positive bacteria with an exception of five cases (17.9%) of vancomycin-resistant enterococcus. In addition, E. fecalis showed 57.1% resistance for high-level aminoglycosides.
Among Gram-negative bacteria, members of Enterobacteriaceae showed more resistance to ampicillin (91.7%), amoxiclav (86.5%), ceftriaxone (88.5%), and gentamicin (60.9%), whereas for imipenem and meropenem a comparatively lower rate of resistance of 0.93 and 12.6%, respectively, was seen. Combination drugs such as cefoperazone-sulbactum and piperacillin-tazobactum were also effective with 40.5 and 25.4% of isolates showed resistance, respectively. Acinetobacter spp. had shown greater resistance to some of its primary drugs such as ceftazidime (76.7%), amoxiclav (57.9%), and aminoglycosides (49.5%), whereas it showed lesser resistance to imipenem (8%), meropenem (15.2), levofloxacin (15.2%), and piperacillin-tazobactum (20.5%). P. aeruginosa were found less resistant to most of the antibiotics such as ceftazidime (18.2%), piperacillin-tazobactum (7.1%), meropenen (14.3%), and levofloxacin (21.4%), whereas 100% sensitivity to imipenem. Other less commonly isolated organism showed a lesser degree of resistance to the antibiotics used as first line drug [Table 5].
| Discussion|| |
BSIs have been a challenge for the clinicians due to changing bacterial resistance profile. The change in the resistance profile may be attributed to the indiscriminate use of antibiotics. Early detection of causative organism and determination of its antimicrobial resistance profile is necessary to decrease the mortality associated with BSIs. Along with that, knowledge of current trend of bacterial profile and its antimicrobial resistance pattern for a geographical location helps clinicians to decide appropriate empirical therapy, which ultimately decreases the emergence of resistance. The present study determines the bacterial profile of 4862 blood samples from suspected cases of bacteremia. The blood culture positivity rate was 494 (10.16%), which is very low in comparison with studies conducted by Alam et al. (20.9%), Arora et al. (20.02%), Sharma et al. (33.9%), and Roy et al. (16.4%). ,,, This low positivity rate may be ascribed to the injudicious use of antibiotics not only by clinicians before referring to the tertiary care center but patients as well.
The incidence of BSIs caused by Gram-positive bacteria was 46.56%, whereas that of Gram-negative bacteria was 51.82%. It is consistent with other studies conducted in India. , Among Gram-positive bacteria, CoNS was the most frequently isolated pathogen that is in accordance with various studies conducted in our country. , While other studies have reported a higher incidence of S. aureus among Gram-positive bacteria causing BSIs. , The high incidence of CoNS could be because a large number of received samples in our set up were from the neonatal intensive care unit. CoNS is a well-described pathogen in neonates, especially when associated with prematurity and central venous lines. However, as CoNS are also possible skin contaminants, clinicians are advised to consider possible risk factors and more importantly their repeated isolation from same patient for deciding therapy. The other Gram-positive bacteria were E. fecalis and S. aureus. Analysis of the incidence of Gram-negative bacteria showed that Acinetobacter spp., E. coli, and P. aeruginosa were the most common causative agents of BSIs among Gram-negative bacteria. The reason for high rate of isolation of Acinetobacter spp. among Gram-negative bacteria may be the acquisition of infection during hospital stay, as it is one of the commonest pathogen seen in nosocomial infections.  In the present study, Candida spp. were isolated in eight (1.62%) cases, whereas other studies have shown a higher incidence. ,
Antimicrobial resistance profile of CoNS has demonstrated a higher rate of resistance to beta-lactam antibiotics than other antimicrobials. Methicillin resistance was seen in 31% cases of CoNS and 57.1% of S. aureus, which implies resistance to beta-lactam antibiotics despite showing sensitivity in antimicrobial susceptibility testing. Also it may be coupled with an increase resistance to other antimicrobials such as aminoglycosides, quinolones, macrolides, and lincosamides.  All staphylococcal isolates were uniformly sensitive to vancomycin and linezolid, which signifies that high-end drugs are still effective in treatment of multidrug-resistant isolates. Enterococcus isolates had shown resistance to vancomycin (17.9%), which is higher in comparison with studies conducted by Sader et al. (2.4%) and Alam et al. (0%). , They have also shown resistance to high level of aminoglycosides (57.1%), which implies that it might not act synergistically with cell wall active antibiotics, such as glycopeptides and beta-lactam antibiotics. 
High prevalence of antimicrobial resistance was noted in this study, especially in Gram-negative bacteria. This might be due to indiscriminate use of antibiotics in hospitals and over the counter sale of drugs, which makes easy availability of drugs. There may be another reason that the extended spectrum beta-lactamase producer Gram-negative bacteria are prevalent in the hospital environment.
Antimicrobial resistance profile of Gram-negative bacteria had shown a higher rate of resistance as compared with Gram-positive bacteria. Most of the Gram-negative bacteria were multidrug resistant with a very high resistance to beta-lactam antibiotics. A lower resistance was seen to carbapenems, flouroquinolones, and combination drugs. But meropenem resistance were seen in 8.3-28.6% isolates, which may be due to inappropriate empirical use of meropenem as the first line treatment. Few cases of imipenem resistance were seen in this study, which is an alarming sign for the clinicians because thereafter they would have a very limited choice of drugs in the form of colistin and tigecycline, which have serious side effects and toxicity. 
It may be concluded from the study that early diagnosis and appropriate treatment of BSIs should be based on the current knowledge of bacterial resistance profile, which should be provided by microbiology laboratory from time to time. This in turn implies that blood cultures must always be obtained in all cases of suspected bacteremia and septicemia, so that both the common pattern of causative organisms and their susceptibility pattern are available in real time for a given health care center and the local region.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]