Frequency and antibiogram pattern of gram positive cocci in catheter related blood stream infections (CRBSI) in a tertiary care hospital, Tamilnadu

Introduction: Blood stream infection associated with catheter is life threatening. Various bacterial agents are responsible for this and Coagulase Negative Staphylococci (CoNS) is now becoming one of the major agent in Catheter Related Blood Stream infection (CRBSI). Objectives: To know the bacterial isolates and the frequency of the CoNS & its antibiotic resistance patterns of in Catheter Related Blood Stream infection (CRBSI). Methods: Catheter tips (5 cm tip) were collected and 5 ml of peripheral blood sample was collected with proper aseptic precautions. Catheter tips were processed using Maki DG et al procedure. Blood was inoculated into the BACTEC blood culture bottle (BacT/ALERT 3D automated blood culture system –BioMerieux). All the gram positive bacteria were further processed for standard biochemical tests. All these isolates were subjected to antibiotic susceptibility testing (Hi-Media discs) by Kirby Bauer disc diffusion test according to CLSI guidelines. Results: Among the total 158 isolates, 55 (34.8%) were gram positive cocci. Coagulase Negative Staphylococci (CoNS), were the predominant isolate in this study. Highest resistance was observed with ampicillin, penicillin, amoxyclav, erythromycin and tetracycline. All the gram positive isolates were 100% sensitive to Vancomycin and Linezolid. Conclusion: Among the total 158 isolates, 55 (34.8%) were gram positive cocci. Coagulase negative staphylococci (CONS) which account 18.98%, followed by 8.86%, Staphylococcus aureus, 5.06% Enterococci and 1.89% were Micrococci. All our isolates were sensitive to Vancomycin and linezolid.


Introduction
CRBSI is the presence of bacteria in blood originating from an intravenous catheter which is a life threatening complication of central venous catheterisation [1].
Central venous catheter plays an important role in the management of critically ill patients and pose a risk of device related infection than other devices and cause significant morbidity and mortality [2]. The mortality rate varies between 30-70% in BSI in hospitalised patients [3]. Gram positive organisms plays a major role in CRBSI than gram negative organism [4]. But both Manuscript received: 6 th January 2017 Reviewed: 16 th January 2017 Author Corrected: 24 th January 2017 Accepted for Publication: 1 st February 2017 gram positive, gram negative bacteria have been isolated from CRBSI and predominance of one type over others varies from place to place and even in the same place over time [5]. Isolation of the pathogen and determination of antimicrobial susceptibility pattern of the isolates remain the anchor of definitive diagnosis and management of BSI [6].
The emergence of antibiotic resistance in all kinds of bacteria is a serious public health issue worldwide, which could be due to increased inappropriate antibiotic use or misuse. The reports of wider variation in the resistance pattern in one area in one period of time are not necessarily true for other area or period [7]. Exclusion criteria: Patients who already had signs and symptoms of septicaemia at the time of admission and less than 48 hours of venous catheterisation were excluded in this study.

Study size & Participants:
A total of 812 catheter tips (5 cm tip) were collected and 5 ml of peripheral blood sample was collected with proper aseptic precautions.
Method: Catheter tips were processed using Maki DG et al procedure. Blood was inoculated into the BACTEC blood culture bottle (BacT/ALERT 3D automated blood culture system -BioMerieux). From the positive BacT bottles, it was sub cultured on blood agar, nutrient agar, chocolate agar, & MacConkey agar and further incubated at 37 0 c overnight and the colony morphology was examined and subjected for gram staining.
All the gram positive bacteria were further processed for standard biochemical tests. Among 812 catheter tips, 158 (19.75%) were found to be culture positive. In this 158 positive isolates, 55 were gram positive cocci (34.8%) All these gram positive isolates were subjected to antibiotic susceptibility testing (Hi-Media discs) by Kirby Bauer disc diffusion test according to CLSI guidelines.
Variables: Of 55 gram positive cocci, 34 were male and 21 were female.
Data source: Intensive care unit (ICU) patients after 48 hours with signs & symptoms of septicaemia.
Bias: we eliminated the bias by applying simple random sampling method for selecting the subject from ICU.

Statistical methods:
Chi-square test (χ 2 ) was applied to find if any equal distribution in the type of CRBSI.

Results
Out of the total 812 blood samples, 158 (19.75%) isolates were found to be positive with CRBSI. Among the total 158 isolates, 55 (34.8%) were gram positive cocci. Among 158 isolates, 27 isolates grown either in blood culture or in catheter tip which were excluded.   Among the gram positive isolates, highest resistance 81%, 78%, 75%, 72%, 69% and 69% were observed with ampicillin, penicillin, amoxyclav, gentamycin, erythromycin, and tetracycline respectively. All our isolates were sensitive to Vancomycin and linezolid. 4% of gram positive isolates were resistant to oxacillin.

Discussion
In blood stream infections, bacteriological profile and antimicrobial susceptibility pattern plays an important role in effective management. In our study, 19.75% showed the positive growth in culture. Many authors have observed the rates of 17% 18.6% & 21.7% respectively in their studies [11,12,2]. Our study is in line with these studies. Vanitha Rani et al., [7] has reported a lower rate of 8.39% whereas 44.9% was the incidence rate in the study of Martins et al [13]. The results have varied with various studies could be due to different factors like socioeconomic, use of ventilators and practice of antibiotic in that locale.
Among the blood culture, 34.8% were gram positive cocci in our study. It was documented that the rates of gram positive cocci isolation in blood culture were, 37.7 %, 41.9% & 69.0% with various studies respectively [7,12,14]. Our study is slightly lower than these studies. Male were commonly affected (61.8 %) in our study.
Though CoNS have been considered as non-pathogenic, due to the both increased use of intravascular device and immune compromised population, it is considered as major nosocomial pathogens. CONS were the major isolates with various studies [15,16]. Staphylococcus aureus was the predominant organism in various studies [2,12,7].
All the gram positive cocci were subjected for antimicrobial susceptibility test. In our study, highest resistance was observed with ampicillin, penicillin, amoxyclav, erythromycin and tetracycline. Similar high resistance of ampicillin was observed by many authors [12,7,17,18].

Research Article
Tropical Journal of Pathology & Microbiology Available online at: www.pathologyreview.in 105 | P a g e Highest resistance for Erythromycin was reported by Ashwini et al, whereas it was highly sensitive agent in the study of Meenakshi et al., [19]. 95% & 90% of penicillin resistance were noted in some studies [20,21]. The variation in resistance pattern with different studies are due to the environment where the test is done and use of newer technology and the pattern of antibiotic practice in that locale. Regular monitoring of pathogen and update of antibiotic resistant pattern is very important in prevention and management of infection.
In our study the methicillin resistance rate was very less (4%). But high methicillin resistance rate of 87.5%, was noted by Kaur et al. 26.7% of methicillin resistance was observed by Parameswaran et al [2,22]. Methicillin resistant gram positive isolates are increasingly reported in various studies and it is a dominant and significant threat to human.
All the gram positive isolates were 100% sensitive to Vancomycin and Linezolid. This in line with many studies. [17,23]. Glycopeptides have been considered to be the reserve drug for these organism. In our study, cephalosporin group of drugs are promising.

Conclusion
The present study provided the prevalence of gram positive cocci in causing blood stream infections and their antibiotic sensitivity pattern in our locale. In each area, the determination of organism responsible for BSI and the antibiotic resistant pattern in periodic interval is necessary for the clinicians to be aware of the pathogens and to provide safe and effective therapy. So that we can develop rational prescribing practices and formulate antibiotic policy.