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Year : 2020  |  Volume : 15  |  Issue : 2  |  Page : 261-265

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

Department of Microbiology, BJ Government Medical College, Pune, Maharashtra, India

Date of Submission19-Mar-2020
Date of Decision30-Mar-2020
Date of Acceptance30-May-2020
Date of Web Publication21-Dec-2020

Correspondence Address:
Dr. Swati Mudshingkar
1st Floor, Above Dean Office (College Building), Department of Microbiology, BJ Government Medical College, Pune, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jdmimsu.jdmimsu_10_20

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Introduction: Clinical manifestations of blood stream infections (BSIs) range from transient bacteremia to fulminant septic shock with high mortality. Regular surveillance of BSI etiology is important in monitoring the spectrum of bacterial pathogens and their sensitivity pattern in a particular area and thus helps in rationalizing therapy. Objective: The present study was undertaken to know the bacteriological etiology of BSIs and the antibiotic susceptibility pattern of the isolated strains to formulate effective empirical treatment. Materials and Methods: During the 1-year study, 5588 blood samples from patients with a clinical diagnosis of sepsis were processed at Microbiology Laboratory of a 1200–bedded tertiary care hospital of Western India. Bacteriological identification and antimicrobial susceptibility testing were performed for all bacterial isolates by following the standard protocol. Results: A culture positivity was seen in 10.73% of the septicemic cases. Contamination was observed at a rate of 1.96%. Of the total 600 bacterial isolates gram-negative Enterobacteriaceae, Gram-negative nonfermenters and Gram-positive cocci contributed to 38%, 31%, and 31%, respectively. The predominant organisms were Acinetobacter spp followed by Klebsiella spp. and Staphylococcus aureus. All Gram-negative bacteria showed low sensitivity to fluoroquinolones and beta lactam drugs such as ampicillin and cephalosporins. Aminoglycosides, carbapenems, chloramphenicol, βeta lactam-β lactamase inhibitor combinations such as Piperacillin tazobactam were effective in treating Gram-negative bacteremia. Chloramphenicol, glycopeptides, and linezolid were effective in treating Gram-positive bacteremia. All Gram-positive isolates showed low sensitivity to fluoroquinolones. Conclusions: This study stresses the need for the continuous screening and surveillance for antibiotic resistance in septicemic cases.

Keywords: Antimicrobial susceptibility, bacteremia, blood stream infections, empirical treatment, resistance

How to cite this article:
Palewar M, Mudshingkar S, Dohe V, Kagal A, Karyakarte R. Bacteriological profile and antibiogram of blood culture isolates from a tertiary care hospital of Western India. J Datta Meghe Inst Med Sci Univ 2020;15:261-5

How to cite this URL:
Palewar M, Mudshingkar S, Dohe V, Kagal A, Karyakarte R. Bacteriological profile and antibiogram of blood culture isolates from a tertiary care hospital of Western India. J Datta Meghe Inst Med Sci Univ [serial online] 2020 [cited 2021 Jan 19];15:261-5. Available from: http://www.journaldmims.com/text.asp?2020/15/2/261/304230

  Introduction Top

Blood stream infections (BSIs) are one of the most common healthcare-associated infections and are associated with significant morbidity and mortality.[1] Clinical manifestations range from transient asymptomatic bacteremia to fulminant septic shock with high mortality.[2] Early diagnosis and management of BSIs is life-saving, and hence, prompt detection of such infections is a critical task of clinical microbiology laboratories. Blood culture is a vital tool and remains the gold standard for bacteremia detection. The prevalence and susceptibility patterns of microorganism vary according to geography and even within the same hospital with time. Hence, regular surveillance of BSI etiology is important in monitoring the spectrum of bacterial pathogens and their sensitivity pattern in a particular area. Such data help clinicians to start effective empirical treatment, prevents irrational use of antibiotics and thus prevents spread of antibiotic resistance. The present study was undertaken to know the bacteriological etiology of BSIs and the antibiotic susceptibility pattern of the isolated strains.

Aims and objectives

  1. To describe the profile of bacteriological isolates causing BSIs in suspected cases of bacteremia and septicemia
  2. To determine the antibiotic susceptibility pattern of bacterial isolates and formulate empirical therapy accordingly.

  Materials and Methods Top

Study design

This was retrospective descriptive record-based study.

Duration of study

One year (January–December 2018).

Study setting

Department of Microbiology BJ Government Medical College Pune.

Study population

Blood samples of all inpatients of the tertiary care hospital received in the department of microbiology, during January–December 2018 were included in the study. Cultures which yielded contaminants and mixed bacterial growths were excluded in the study.

Processing of samples

Blood samples were collected from the patients before the administration of any antibiotic. Relevant details of the patients were recorded in registers. Samples from intensive care units (ICUs) were received in adult and pediatric BACTEC bottles and processed by automated BACTEC system. Samples from wards were received in conventional adult and pediatric blood culture bottles containing BHI broth with activated charcoal and were processed manually. Conventional blood culture bottles inoculated with the sample were incubated at 37°C aerobically, and periodic subcultures were done on blood agar and Macconkey agar on day 2 and day 5. The growth obtained was identified by colony morphology, gram stain of the isolated colonies and standard biochemical identification tests.[3] BACTEC blood culture were processed manually after they flashed positive. Antimicrobial susceptibility testing was performed by Kirby–Bauer disk diffusion method and interpreted using clinical laboratory standard institute (CLSI) guidelines 2019.[4] For Gram-positive bacteria from blood isolates following drugs were tested: penicillin (10U), cefoxitin (30 μg), trimethoprim-sulfamethoxazole (1.25/23.75 μg), gentamicin (10 μg and 120 μg), ciprofloxacin (5 μg), linezolid (30 μg), teicoplanin (30 μg), chloramphenicol (30 μg). Vancomycin (30 μg discs) was used for Enterococcus and Streptococci. Vancomycin screen agar was used for Staphylococci species. For Gram-negative bacteria following drugs were tested: ampicillin (10 μg), gentamicin (10 μg), ciprofloxacin (5 μg), cefotaxime (30 μg), cefepime (30 μg), and ceftriaxone (30 μg), Trimethoprim/sulfamethoxazole (1.25/23.75 μg), ceftazidime (30 μg), amikacin (30 μg), piperacillin-tazobactam (100/10 μg), meropenem (30 μg), and chloramphenicol (30 mcg), and ceftazidime-clavulanic (30/10 mcg) were tested. The susceptibility and resistance were interpreted as per CLSI guidelines 2019.[4]  Escherichia More Details coli (ATCC 25922), Staphylococcus aureus (ATCC 25923), Pseudomonas aeruginosa (ATCC 27853), and  Enterococcus faecalis Scientific Name Search ATCC 29212) were used as reference strains for culture and susceptibility testing.

Data analysis

Data were entered and analyzed using Whonet software.

Ethical Clearance

This paper titled “ Bacteriological Profile and Antibiogram of Blood Culture Isolates from a Tertiary Care Hospital of Western India” is a real retrospective study done with bacterial isolates and their susceptibility pattern. Its not interventional study, hence ethical clearance was not taken for the same.

  Results Top

A total of 5588 blood samples were received from different wards and ICUs of the hospital. Positive aerobic bacterial growth was observed in 621 samples from 600 patients. But to formulate antibiogram only 1st isolate from patient was considered and hence 600 isolates from 600 patients were considered for formulation of antibiogram. Hence, culture positivity was seen in 10.73% of the septicemic cases. One hundred and eleven isolates (1.96%) were contaminants recovered during culture of samples. Out of 600 culture positive samples, 347 (58%) were male and 253 (42%) were female. Gender-wise ratio of 1.37:1 was observed and skewed in favor of males [Table 1]. Highest blood culture positivity was found in the age group of <1 month 140 patients (23%) [Table 2]. [Table 3] describes the ICU and ward-wise distribution of patients with culture positive bacteremia. None of the patient was from outpatient department setting in the present study. Among ICU's maximum number of patients were from neuro-ICU (n = 140) and medical ICU (n = 36). In ward-wise distribution, maximum number of patients were from medicine ward (N = 165) followed by pediatric ward (N = 77).
Table 1: Distribution based on gender

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Table 2: Distribution based on age

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Table 3: Intensive care units and Wardwise distribution of patients

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Out of the total 600 bacterial isolates Gram-negative Enterobacteriaceae, Gram-negative non fermenters and Gram-positive cocci contributed to 38%, 31%, and 31%, respectively [Graph 1]a. [Graph 1]b shows there were 394 isolates from ward and 206 isolates from ICUs and also their susceptibility patterns are compared.

The predominant organisms were Acinetobacter spp. (n = 88) and Klebsiella spp.(n = 84) and S. aureus (n = 65). Among nonfermenters apart from Acinetobacter spp. and Pseudomonas spp. there were other nonfermenters were such as Stenotrophomonas maltophilia, Burkholderia cepacia, Burkholderia spp, Chryseobacterium meningosepticum, and Sphingobacterium spp. Among Gram-positive cocci S. aureus dominated followed by Coagulase negative staphylococci and Enterococcus spp [Graph 2]. Amongst Enterobacteriaceae Klebsiella spp. predominated followed by Citrobacter, Enterobacter, E. coli, Proteus, and  Salmonella More Details spp. The prevalence of Salmonella typhi was low 0.5% (3/600) in our study.

Antimicrobial resistance pattern of Gram-negative blood isolates and Gram-positive blood isolates in wards and ICUs is shown in [Graph 3] and [Table 4].
Table 4: Susceptibility of Gram-positive isolates in intensive care units and wards

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Ward isolates had low percentage of sensitivity to all antibiotics class when compared to ICU isolates. Susceptibility of ICU and ward isolates to all antibiotics stated below, respectively. Gram-negative blood isolates showed low sensitivity to ampicillin (9.18%), cephalosporins such as cefotaxime (23%, 37%), cefepime (23%, 44%), ciprofloxacin (35%, 55%), and aztreonam (30%, 42%). Moderate sensitivity to aminoglycosides such as amikacin (35%, 63%), gentamicin (36%, 60%), chloramphenicol (38%, 60%), and piperacillin-tazobactum (39%, 64%). High susceptibility to meropenem (55%, 72%) and colistin (100%, 100%).

ESBL rates were 75% and 60% respectively in ICU and ward isolates, respectively.

S. aureus isolates showed 100% sensitivity to vancomycin, teicoplanin, and linezolid in both settings and 87%, 90% sensitivity to chloramphenicol in ICU and ward respectively, however, there was moderate sensitivity to Gentamicin (67%, 80%) and trimethoprim sulfamethoxazole (60%, 75%) and low sensitivity to ciprofloxacin (20%, 27%) in ICUs and wards, respectively. There was higher prevalence of methicillin resistant S. aureus (MRSA) (70%) from ICU and 62% from ward isolates. Enterococcus species showed high sensitivity to vancomycin (90%, 98%), teicoplanin (90%, 98%), chloramphenicol (89%, 90%) in ICU and ward isolates, respectively, 100% sensitivity to Linezolid in both settings. High level gentamicin resistance was 44% and 60%, respectively, in ICU and ward isolates. Low sensitivity to ciprofloxacin (10%, 24%) was noted among Enterococcus isolates. All Streptococci species were sensitive to vancomycin, linezolid, and chloramphenicol. Among coagulase-negative staphylococci sensitivity to vancomycin was (97.5%, 100%), teicoplanin (97.5%, 100%), and chloramphenicol (87%, 90%) in ICU and wards, respectively.

  Discussion Top

BSI is a challenging problem and may be life-threatening, therefore its timely detection, identification, and antimicrobial susceptibility testing of BSI pathogens is the most important task of diagnostic microbiology laboratory.[6],[7] Each hour of delay in therapy initiation is associated with an average decrease in survival of 8%.[6],[8] This study attempts to analyze the bacterial profile and assess their antimicrobial trends to formulate antibiogram and effective empirical treatment of BSIs.

In the present study, the culture positivity was 10.73%. This rate of isolation is consistent with many studies from India[6],[9],[10],[11],[12] and abroad.[13],[14] Higher culture positivity is reported by some authors.[15],[16],[17],[18] Variation in culture positivity rates could be due to difference in geographical location, nature of population, epidemiological difference of the etiological agents, also factors such as volume or number of blood culture samples. The low rate of isolation in our study could be due to the fact that most of the patients would have already received antibiotic treatment at peripheral health center before being referred to our tertiary care hospital.

A total of 111 (1.96%) isolates of contaminants were isolated in the present study. The rate of contamination observed is below the target level suggested by Hall and Lyman.[17]

Gender-wise ratio of 1.37:1 was observed skewed in favor of males in our study in accordance with recent review of data in the National Hospital Discharge Survey (U.S) which states incidence of sepsis, severe sepsis, and septic shock is higher in men than in women.[2]

Attack rate is very high among infants, particularly low birth weight newborns experience high risk. Sepsis incidence and its related mortality decrease after the 1st year of life and thereafter increases with increasing age.[2],[5] Furthermore, in our study, the highest blood culture positivity was found in the age group of <1 month 140 patients (23%) and <1 year 170 patients (28%).

In the present study also, septicemia due to Gram-negative isolates predominated over Gram-positive isolates as observed in various other studies too.[12],[18] Among Gram-negative pathogens, Enterobacteriaceae as a group accounted for maximum sepsis cases 35% of total sepsis and 55.52% (231/416) of all Gram-negative sepsis with a predominance of Klebsiella species, Citrobacter and E. coli similar to findings reported in other studies.[6],[12] However, as an individual bacterial genus, nonfermenting bacilli Acinetobacter spp. (n = 88) was more predominant. Rather all nonfermenting bacteria combined together accounted for 31% of total sepsis and 44.47% (185/416) of all Gram-negative sepsis. The finding is of significant concern as in the hospital setting, theses isolates are associated with a high degree of antimicrobial resistance.[6],[18],[19] In our study, S. typhi was isolated in 0.5% (3/600) cases; finding concordant to the study by Jadhav et al.[20] from the same geographical area (1.5%), but in contrast to various other studies which reported prevalence between 12% and 15%.[18],[19] The most common Gram-positive bacterium isolated in the present study was S. aureus followed by coagulase-negative Staphylococcus and Enterococcus species. Predominance of S. aureus as a blood stream pathogen has been documented by other studies.[6] Among these isolates, the prevalence of MRSA ranged from 70% in ICU setup and 62%in wards complicating management of BSIs. Since the past two decades, coagulase negative Staphylococcus (CoNS), the usual skin commensals are increasingly being considered bloodstream pathogens in select settings. Improper methods of blood collection and the presence of longstanding intravascular catheters are recognized as possible modes of spread of BSI by CoNS.

In present study all gram-positive isolates showed higher sensitivity to vancomycin, teicoplanin, linezolid, chloramphenicol which is comparable to other Indian studies.[6],[12] All Staphylococcus species were moderately sensitive to Gentamicin and Trimethoprim-sulfamethoxazole. S. aureus and Enterococcus species showed low sensitivity to Ciprofloxacin and CONS were moderately sensitive to Ciprofloxacin. High level gentamicin resistance was noted in 44% and 60% Enterococcus isolates from ICU and wards, respectively.

All Gram-negative bacteria showed low sensitivity to ampicillin, cephalosporins such as ceftazidime, ceftriaxone, and cefepime. Beta–lactam drugs are rapidly becoming ineffective for treating BSIs due to indiscriminate and nonjudicious usage. 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 degree of resistance. All GNBs showed moderate sensitivity to ciprofloxacin, trimethoprim-sulfamethoxazole. Comparatively higher sensitivity to aminoglycosides amikacin, gentamicin, piperacillin-tazobactum, Meropenem, Chloramphenicol and Colistin. These findings match with other Indian studies.[6],[11],[12] Hence, rationalization of treatment strategies is very much warranted considering the local trends of BSIs. Poor infection control practices and inappropriate use of antibiotics are main driving forces for the spread of resistant organisms. With the shortage of newer drugs' availability and increasing resistance, the use of limited option drugs such as colistin by clinicians could soon lead to the condition of so called pan drug–resistance.[6],[11]

  Conclusions Top

Thus present study provides the prevalence of bacterial pathogens in BSIs and their antibiotic sensitivity patterns in our tertiary care center of Western India. We recommend the following empirical treatment in our set up:

  1. In moderate BSIs (Hospitalized in wards, not in ICU): Aminoglycoside (Amikacin, Gentamicin)/Chloramphenicol or Piperacillin tazobactum. Use injectables and switch to oral earliest
  2. In severe BSIs (Hospitalized in ICUs): Aminoglycosides/Piperacillin tazobactum and Meropenem and add vancomycin if MRSA Suspected. Escalate/descalate after culture and sensitivity report.

Routine surveillance of local BSI etiology is essential for formulation of hospital antibiograms and effective empirical treatment of sepsis in that particular area. There are only a few newer antimicrobials in the research pipeline. It is foreseen that if injudicious prescription of antibiotics continues, we will face the problem of pan drug resistance in near future. We need to implement specific antibiotic utilization strategies such as restricting antibiotic use, combination therapy, antibiotic usage as per antimicrobial susceptibility testing results to reduce incidence of BSIs as well as prevent the emergence of resistance. Robust infection control practices and antibiotic stewardship programs are prime need of the hour.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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  [Table 1], [Table 2], [Table 3], [Table 4]


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