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Year : 2016  |  Volume : 19  |  Issue : 2  |  Page : 94-99

Bacteriological profile and antibiogram of blood culture isolates from a tertiary care hospital of North India

Department of Microbiology, Lok Nayak Hospital, Maulana Azad Medical College, New Delhi, India

Date of Web Publication5-Jul-2016

Correspondence Address:
Bineeta Kashyap
Department of Microbiology, Lok Nayak Hospital, Maulana Azad Medical College, New Delhi
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DOI: 10.4103/1119-0388.185426

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Introduction: Blood stream infections cause a significant morbidity and mortality worldwide. Rapid and reliable detection of bacterial pathogens and rational use of antimicrobials are required for proper management. The present work was undertaken to study the bacteriological profile along with the antibiogram of the blood culture isolates from clinically diagnosed cases of sepsis. Materials and Methods: During the 1-year study period, 3472 blood samples from patients with a clinical diagnosis of sepsis were received at the Emergency Microbiology Laboratory of a 2500-bedded tertiary care hospital of North India. Bacteriological identification and antimicrobial susceptibility testing were performed for all bacterial isolates by following the standard protocol. Results: Culture positivity was seen in 16.5% of the septicemic cases. The most common bacteria isolated were Escherichia coli (22.4%) followed by Klebsiella species (19.7%), Staphylococcus aureus (18.3%), and coagulase-negative staphylococci (17.4%). About 26.5% of S. aureus were methicillin-resistant. Vancomycin (100%), gentamicin (87.9%), and ciprofloxacin (73%) showed the highest activity among the Gram-positive isolates. Most of the Gram-negative bacteria were multi-drug resistant (67.1%). Imipenem (98.8%), amikacin (90.8%), and cefoperazone/sulbactam combination (81.1%) showed the highest activity among Enterobacteriaceae. Nonfermenters in majority were susceptible to imipenem (88.2%), amikacin (81.6%), and piperacillin/tazobactam combination (72.4%). Gram-negative isolates showed 100% sensitivity toward colistin. Conclusion: The present study highlights the bacteriological etiology of sepsis along with the antibiogram of septicemic isolates that may provide necessary information for the formulation of antibiotic policy in effective management of such cases.

Keywords: Antimicrobial susceptibility, bacteremia, blood stream infection, resistance

How to cite this article:
Gupta S, Kashyap B. Bacteriological profile and antibiogram of blood culture isolates from a tertiary care hospital of North India. Trop J Med Res 2016;19:94-9

How to cite this URL:
Gupta S, Kashyap B. Bacteriological profile and antibiogram of blood culture isolates from a tertiary care hospital of North India. Trop J Med Res [serial online] 2016 [cited 2020 Jul 9];19:94-9. Available from: http://www.tjmrjournal.org/text.asp?2016/19/2/94/185426

  Introduction Top

Bacteremia ranges from self-limiting infections to life-threatening septicemia that requires rapid and aggressive antimicrobial treatment. [1] The mortality rate ranges from 20% to 50% in cases of bacteremia. [2],[3] Septicemia leads to a significant morbidity and mortality and it is among the most common health-care associated infections. In recent years, there has been an increase in the incidence of bacteremia caused by the members of Enterobacteriaceae and other Gram-negative bacilli. Sensitive bacterial strains are now being replaced by multi-drug resistant (MDR) strains of Klebsiella, Pseudomonas, Acinetobacter, and Citrobacter species. [4] Increase in incidence is also seen among Gram-positive isolates such as methicillin resistance in Staphylococcus aureus (MRSA) and vancomycin resistance in Enterococci. [5] This increasing antimicrobial resistance is a worldwide concern and is subjected to regional variation. [6] Thus, regular surveillance of blood stream etiology is important in monitoring the spectrum of bacterial pathogens and their sensitivity pattern in a particular area. Such data are not only necessary for the clinicians to be aware of the emerging resistant strains of pathogens that are a threat to the community but also provide platform to initiate effective empirical therapy. [7] Awareness of the baseline microbial resistance specific to a hospital prevents irrational use of antibiotics in that hospital, thus helps progress a step forward in the prevention of spread of antibiotic resistance. The present study was undertaken to know the bacteriological etiology of blood stream infections and the antibiotic susceptibility pattern of the isolated strains.

  Materials and Methods Top

A total of 3472 blood samples from clinically diagnosed cases of sepsis, received in the emergency microbiology laboratory of a 2500-bedded tertiary care teaching hospital of North India over a duration of 1 year, were included in the study. Samples received were from the inpatient population of the hospital. Blood samples were collected from the patients before the administration of any antibiotic. Relevant details of the patients were recorded in a predesigned pro forma. Blood culture bottles inoculated with the sample were incubated at 37°C aerobically, and periodic subcultures were done on blood agar and MacConkey's agar on day 2 and day 7, respectively, and in between if turbidity appeared visibly. The growth obtained was identified by colony morphology, Gram-stain of the isolated colonies, and conventional biochemical identification tests as per the standard protocol followed in our laboratory. [8] The antibiotic susceptibility pattern of the isolated organisms was performed by Kirby-Bauer disc diffusion method on Mueller-Hinton agar plates, and the results were recorded as per the Clinical and Laboratory Standards Institute 2015 guidelines. [9] Cefoxitin disc diffusion method was used to identify MRSA and methicillin-resistant coagulase-negative staphylococci (MRCoNS) among Staphylococcus and coagulase-negative staphylococci isolates, respectively. [9] MDR was defined as nonsusceptibility to at least one agent in three or more antimicrobial categories for S. aureus, Enterococcus species, Enterobacteriaceae (other than Salmonella and Shigella), Pseudomonas aeruginosa, and Acinetobacter species. [10] The antibiotic discs that were used to identify the susceptibility pattern of the bacterial pathogens and their concentrations included penicillin (10 mcg), amikacin (30 mcg), amoxicillin clavulanic acid (30/10 mcg), ceftazidime (70 mcg), ceftriaxone (30 mcg), cefixime (5 mcg), cefepime (30 mcg), cefoxitin (10 mcg), cefoperazone/sulbactam combination (70 mcg), ciprofloxacin (5 mcg), clindamycin (2 mcg), erythromycin (10 mcg), gentamicin (10 mcg), imipenem (10 mcg), linezolid (30 mcg), piperacillin/tazobactum combination (100/10 mcg), tobramycin (10 mcg), and vancomycin (30 mcg).

  Results Top

A total of 3472 blood samples received during the study period were processed for aerobic culture and 573 (16.5%) of these samples yielded growth. Among 573 positive blood culture samples, 554 (96.68%) yielded bacterial isolates and 19 (3.31%) were Candida species. Poly-microbial growths were seen in 3 blood samples out of 554 (0.54%) blood samples with bacterial etiology whereas the remaining 551 (99.45%) blood samples yielded mono-bacterial growth. Three patients whose culture had poly-microbial growth had Klebsiella pneumoniae with Enterococcus species, Escherichia coli with S. aureus, and Acinetobacter species with Enterococcus species. Out of the total 557 bacterial organisms isolated from 554 positive blood culture samples, Gram-positive and Gram-negative organisms contributed to 41.65% (232/557) and 58.34% (325/557), respectively. [Figure 1] describes the distribution of the total bacterial isolates obtained from positive blood cultures. E. coli was the predominant organism isolated (22.4%) followed by Klebsiella species (19.7%) and S. aureus (18.3%). The ward-wise distribution of the samples has been shown in [Figure 2]. Out of the total 150 (26.9%) bacterial isolates from Neonatal Intensive Care Unit (NICU), Pediatric Intensive Care Unit, and medico-surgical ICU, maximum positivity was found from NICU (16%). Among the Gram-positive isolates, the predominant isolate was S. aureus (43.9%) followed by coagulase-negative staphylococci (41.8%) and Enterococcus species (11.6%), which exhibited no resistance to vancomycin and linezolid. MRSA was found to in 26.47% of total S. aureus isolates whereas MRCoNS was found in 18.6% of total CoNS isolates. [Table 1] shows the sensitivity pattern of Gram-positive isolates toward various antibiotics. Among Gram-positive isolates, amoxyclav and erythromycin showed high degree of resistance with 73.9% and 68.3% resistant isolates, respectively [Figure 2]. The most commonly isolated Gram-negative bacteria was E. coli (38.46%) followed by Klebsiella species (33.84%), Pseudomonas species (14.46%), and Acinetobacter species (8.92%). Salmonella typhi was found in 1.53% of total Gram-negative isolates from blood culture. Enterobacteriaceae showed the maximum resistance to amoxyclav (91.4%) followed by cefixime (90.37%) and ceftriaxone (74.7%) as shown in [Figure 3]. Among cephalosporins, cefoperazone/sulbactam combination was found to be highly sensitive for Enterobacteriaceae (81.14%) [Table 2]. Amikacin showed high in vitro susceptibility for both Enterobacteriaceae (90.76%) and nonfermenters (81.57%). Carbapenem resistance was seen more among nonfermenters (11.85%) as compared to Enterobacteriaceae (1.23%). No strain among bacterial isolates was found to be colistin-resistant. [Figure 3] depicts percentage resistance shown by Gram-positive cocci, Enterobacteriaceae, and nonfermenters toward various antibiotics. Total MDR isolates observed in our study were 46.3%. Among Gram-positive organisms, MRSA, MRCoNS, and MDR enterococcus observed were 26.5%, 13.4%, and 55.6%, respectively. Multidrug resistance was observed in high number among Gram-negative isolates, with 75.8% (185/244) among Enterobacteriaceae species and 43.42% (33/76) among nonfermenters.
Figure 1: Frequency distribution of bacterial blood isolates from suspected septicemic patients (n = 557)

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Figure 2: Frequency distribution of Gram-positive and Gram-negative bacterial isolates in various wards and Intensive Care Units of the hospital

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Figure 3: Percentage of bacterial resistance to various antibiotics

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Table 1: Antibiotic sensitivity pattern of Gram-positive bacterial isolates in blood culture (n=232)

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Table 2: Antibiotic sensitivity pattern of Gram-negative bacterial blood culture isolates (n=325)

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  Discussion Top

The present study provides information on the distribution of bacterial isolates causing bloodstream infections along with their antibiotic susceptibility pattern that plays a crucial role in effective management of septicemic cases. The blood positivity rate found in our study was 16.5%, which was comparable to rates reported by various other Indian studies. [11],[12] In contrast, low culture positivity ranging from 5.6% to 8.39% whereas high culture positivity ranging from 33.9% to 52.10% were reported by various other authors. [3],[6],[13],[14],[15] Such variation in blood culture positivity can be explained by various factors such as volume or the number of blood culture samples taken for study as explained by Lee et al., 2007. [16] The low isolation rate in our study could also be explained by the fact that quite a few number of patients already undergo some kind of primary treatment at peripheral health centers before reaching a tertiary care hospital. Self-medication is also common due to over-the-counter availability of the medicines. We did try to exclude such cases by history. In most of the studies, Gram-negative bacteria were found to be predominant over Gram-positive organisms, especially so in hospital settings. In the present study also, Gram-negative isolates were predominant over Gram-positive isolates as observed in various other studies too. [4],[11],[17] Among Enterobacteriaceae, E. coli and Klebsiella species were the predominant isolates (72.3%) similar to findings reported in earlier studies. [12],[18],[19] A high prevalence of nonfermenters; Pseudomonas species (8.4%) and Acinetobacter species (5.2%); was found in our study as reported by Chhina and Gupta and Vanitha et al. The finding is of significant concern as in the hospital settings, these isolates are associated with a high degree of antimicrobial resistance. [4],[19] In our study, S. typhi was isolated in 0.9% cases; finding concordant to the study by Jadhav et al. (1.5%), but in contrast to various other studies which reported prevalence between 12% and 15%. [4],[6],[12],[19] The most common Gram-positive bacterium isolated in the present study was S. aureus followed by coagulase-negative Staphylococcus. Other surveillance studies have reported CONS as the most common Gram-positive organism isolated from blood culture specimens. [11],[20] Due to irrational and increased use of antibiotics, there is an increase in the prevalence of resistance among microorganisms and stream pathogens. The etiological profile and antibiotic spectrum of bacterial pathogens vary geographically due to variations in social and environmental conditions. [11] Thus, the main purpose of the present study was to assess the antibiotic susceptibility pattern of the major pathogens among the clinically diagnosed cases of sepsis. Most of the isolates (46.3%) found in our study were MDR. Among Gram-positive isolates, MRSA was found in significant frequency (26.47%), almost similar to the findings in other Indian studies. [4],[11] Rate as high as 35% has been reported by Ahmadey and Mohammed [21] Earlier studies have reported an increased resistance to ampicillin, amoxicillin/clavulanic acid combination, and erythromycin among Gram-positive isolates; a finding also observed in our study. [4],[11],[22] Apart from vancomycin and linezolid, that were 100% sensitive, increased susceptibility was seen with gentamicin (87.9%), clindamycin (73.65%), and ciprofloxacin (73%) among Gram-positive isolates. These antibiotics were found to be susceptible in many MRSA and MRCoNS strains. Multidrug resistance was found in 55.56% of the Enterococcal isolates which was similar to the finding of Jain et al. (54%), a study conducted in East Delhi. In the same study, 2.7% of Enterococcal isolates were found to be moderately sensitive to vancomycin in contrast to our finding where no vancomycin-resistant isolates were found in blood culture. [23] Among Gram-negative isolates, overall antibiotic susceptibility pattern suggests a high prevalence of MDR organism in our hospital. In our study, we found 218 (67.1%) Gram-negative isolates to be MDR. Several other studies also have reported high frequency of Gram-negative isolates as MDR. [6],[15],[22] Indiscriminate use of antibiotics and lack of appropriate antibiotic policy in the hospital could be the main reasons for this existing problem. In the present study, MDR isolates were observed in 75.8% of the total Enterobacteriaceae isolates with a high degree of resistance observed to amoxicillin/clavulanic acid combination, second and third generation cephalosporins. The fact that cephalosporins are one of the most commonly used antibiotics for inpatients as well as for outpatients could be the reason for such high level of resistance being observed in the developing countries. [24] Majority of Enterobacteriaceae were sensitive to imipenem (98.77%), amikacin (90.76%), and cefoperazone/sulbactam combination (81.14%). A study conducted in Chandigarh showed similar findings, but a majority of Enterobacteriaceae were found to be susceptible to ceftriaxone, which is in contrast to the finding in the present study. [12] MDR isolates among nonfermenters were seen in 43.42% in the present study. Amikacin (81.57%), piperacillin/tazobactam combination (72.36%), and imipenem (88.15%) were found to be highly susceptible for MDR nonfermenter isolates. This finding has also been observed in several other studies. [4],[12],[25] In the present study, we found 13 out of the total Gram-negative isolates to be carbapenem-resistant with 9 (69.23%) and 4 (30.76%) isolates among nonfermenters and Enterobacteriaceae, respectively. The greatest threat with MDR and carbapenem-resistant Gram-negative bacteria is that the infections are usually untreatable due to the limited options of the antibiotics available, resulting into increased mortality. Worldwide, their incidence is rising with variations due to regional and geographical differences as stated by Jadhav et al. [6] With the shortage of newer drugs availability and increasing resistance, use of limited option drugs such as colistin by clinicians could soon lead to the condition of so-called pan-drug resistance.

The present study provides information on the prevalence of bacterial pathogens causing blood stream infections along with their antibiotic susceptibility profile. The study identified both Gram-positive and Gram-negative bacteria to be responsible for blood stream infections, and most of them were found to be MDR. Vancomycin and gentamicin were found to be most effective for Gram-positive bacteria whereas cefoperazone/sulbactam combination and amikacin were found to be most effective for Gram-negative isolates. The increase in the prevalence of MDR bacteria emphasize the urgent need for rational use of antibiotics, formulation of antibiotic policy, and implementation of infection control practices for the effective management and prevention of drug resistance.

  Conclusion Top

Routine surveillance of baseline resistance, formulation of hospital antibiotic policy and compliance with existing guidelines will go long way in reducing multi drug resistance in pathogens.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2]

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