Original article DOI: https://doi.org/10.18320/jimd/201603.03134 JOURNAL OF INTERNATIONAL MEDICINE AND DENTISTRY To search..to know...to share p-issn: 2454-8847 e-issn: 2350-045X Prevalence and antimicrobial susceptibility pattern of clinical isolates of Methicillin-resistant Staphylococcus aureus in a tertiary care hospital in Mangalore Hannath Ayesha Reema 1, Saldanha Dominic R M 2 Abstract: Staphylococcus aureus is the most common human bacterial pathogen and is an important cause of nosocomial infections. Due to inappropriate use of antibiotics, the resistance in these strains is increasing worldwide. In India, Methicillin-resistant Staphylococcus aureus(mrsa) represents a challenge for all healthcare institutions. This study was carried out to determine the prevalence of MRSA in a tertiary care hospital and the prevalent antibiotic susceptibility patterns. Fifty strains of MRSA were taken up for the study. Methicillin resistance was detected by Cefoxitin Disk Diffusion test. A prevalence rate of 46% for MRSA was seen in our study. The most effective antibiotics were Linezolid (100%), Teicoplanin (96.6%) and Vancomycin (96.6%). This study highlights the fact that MRSA continues to be a problem in healthcare institutions. With MRSA rates being high, routine and regular surveillance of MRSA and in vitro susceptibility testing, regular monitoring and update of infection control practices and antibiotic policies might change the prevailing trends and reduce the chances of MRSA infections. Key words: MRSA, Cefoxitin, Linezolid, Vancomycin Introduction: Staphylococcus aureus is the most common human bacterial pathogen and is an important cause of skin and soft tissue infections, endovascular infections, pneumonia, tonsillitis, pharyngitis, septic arthritis, endocarditis, enterocolitis, osteomyelitis, meningitis, toxic shock syndrome, sepsis, etc. Due to inappropriate use of antibiotics, the resistance in these strains is increasing worldwide. 1 In India, Methicillin-resistant Staphylococcus aureus(mrsa) represents a challenge for all healthcare institutions. Previously, it was limited to large institutions; now is quite common in all hospital settings. 2, 3 Many of these MRSA isolates are becoming multi-drug resistant and are susceptible only to glycopeptide antibiotics such as Vancomycin. 4 Low level resistance even to Vancomycin is emerging at present. 5 The prolonged hospital stay, indiscriminate use of antibiotics, lack of awareness, receipt of antibiotics before coming to the hospital etc. are the possible predisposing factors of MRSA emergence. 2 Use of invasive medical devices, healthcare workers, suppressed immune system, prolonged use of antimicrobials, living in crowded or unsanitary conditions are some risk factors for MRSA infections. 1 Therefore, the knowledge of prevalence of MRSA and their current antimicrobial profile become necessary in the selection of appropriate empirical treatment of these infections. This study was carried out to determine the prevalence of MRSA in a tertiary care hospital and the prevalent antibiotic susceptibility patterns. Aims: To study the prevalence of Methicillin-resistant Staphylococcus aureus [MRSA] Objectives: 1. To determine the prevalence of MRSA in a tertiary care hospital
2. To determine the susceptibility patterns of MRSA to various antimicrobial agents Materials and Methods: The study was conducted at the Department of Microbiology, Yenepoya Medical College, Mangalore. Fifty strains of Staphylococcus aureus were included in the study. The strains were isolated and identified from clinical specimens of patients received at the diagnostic microbiology laboratory. Specimens includes pus, urine and fluids. The specimens were collected using all aseptic precautions and transported to the laboratory immediately for processing. The specimens were collected using all aseptic precautions and transported to the laboratory immediately for processing. Specimen processing: Direct examination: For all the specimens received in the microbiology laboratory, smears were prepared and stained with Gram stain. They were microscopically examined to determine the presence and type of cells along with the number of microorganisms and their relative morphology. The specimens (except blood) were plated onto culture media 5% sheep blood agar and MacConkey s agar immediately after transporting them to the laboratory and were incubated at 37 C for 24 hours at a carbon dioxide concentration of 5-10%. Blood was inoculated into Brain Heart Infusion (BHI) broth and incubated at 37 C for 6-8 hours before subculturing them onto the respective media After inoculation, the plates were examined for growth and identified by standard microbiological techniques. Isolates of Staphylococcus aureus were identified using standard tests like catalase test, slide and tube coagulase and growth on Mannitol Salt agar. 6 Antimicrobial susceptibility testing was done by Kirby- Bauer method to determine the sensitivity pattern and interpretation was done according to Clinical Laboratory Standards Institute (CLSI) guidelines. 7,8,9,10 Antibiotics tested included Amoxyclav (10/20mcg), Cefoxitin (30mcg), Ciprofloxacin (5mcg), Co-trimoxazole (1.25/23.75mcg), Erythromycin (15mcg), Ceftazidime (30mcg), Clindamycin (2mcg), Linezolid (30mcg) and Vancomycin (30mcg). After 18-24 hours incubation, the sensitivity plates were observed and the diameter of the inhibitory zone measured. The zone size around each antimicrobial disc was interpreted as sensitive, intermediate or resistant according to CLSI criteria. Methicillin resistance was detected by Cefoxitin Disk Diffusion test. Staphylococcus aureus ATCC 25923 was used as the standard control strain. Results: A total of 50 Staphylococcus aureus strains isolated from clinical specimens. The specimens from which the isolates were obtained included pus, urine and fluids.the age distribution patterns of the isolates obtained is as mentioned in Figure I. The highest number of isolates were seen in the age group of >18-45 years- 25 isolates (50%), whereas the least number of isolates were seen in the >1-18 year age group- 1 isolate (2%). In terms of numbers, the highest number of MRSA and MSSA was seen in the age group of >18-45 years. (Table I). Table I: Distribution of MRSA and MSSA among various age groups AGE MRSA n (%) MSSA n (%) <1 yr - 2 (100) >1-18yr 1 (100) - >18-45yr 13 (52) 12 (48) >45-60yr 8 (48) 9 (52) >60yr 1 (20) 4 (80) 135
The susceptibility patterns of the various aureus is as mentioned in antibiotics tested against Staphylococcus Figure I: Age distribution patterns of patients infected with Staphylococcus aureus. Table II. P E R C E N T A G E 50 45 40 35 30 25 20 15 10 5 0 AGE <1 yr >1-18 yr >18-45 yr >45-60 yr >60 yr Table II: Antibiotic susceptibility patterns of Staphylococcus aureus ANTIBIOTIC (n) SENSITIVE n ( %) INTERMEDIATE n (%) RESISTANT n (%) Ampicillin (48) 4 (8.33%) 1 (2%) 43 (89.5%) Amoxyclav (24) 13 (54.1%) - 11 (45.8%) Cefoxitin (50) 23 (46%) - 27 (54%) Ceftazidime (24) 10 (41.6%) 1 (4.1%) 13 (54.1%) Co-trimoxazole (47) 33 (70.2%) 1 (2.1%) 13 (27.6%) Clindamycin (45) 40 (88.8%) - 5 (11.1%) Linezolid (49) 49 (100%) - - Rifampicin (17) 16 (94.1%) - 1 (5.88%) Teicoplanin (48) 47 (97.9%) - 1 (2%) Vancomycin (50) 48 (96%) - 2 (4%) Ciprofloxacin (23) 5 (21.7%) - 18 (78.2%) Erythromycin (47) 19 (40.4%) - 28 (59.5%) Tetracycline (23) 22 (95.6%) - 1 (4.3%) Gentamycin (23) 11 (47.8%) 1(4.3%) 11 (47.8%) Daptomycin(16) 16 (100%) - - The most effective antibiotics against Staphylococcus aureus were Daptomycin- 16(100%), Linezolid- 49(100%), Teicoplanin- 47(97.9%), Vancomycin- 48(96%) and Rifampicin- 16(94.1%). Staphylococcus aureus was found to be most resistant to Ampicillin- 43(89.5%), Ciprofloxacin-18(78.2%), Erythromycin- 28(59.5%), Ceftazidime- 13(54.1%) and Gentamycin- 11(47.8%). The most effective antibiotics against MRSA were Linezolid (100%), Teicoplanin (96.6%) and Vancomycin (96.6%). Discussion: Among the gram positive pathogens, Staphylococcus aureus, especially MRSA has become a major nosocomial pathogen 136
causing skin and soft tissue infections in both community and hospitalized patients. 11 In the last two decades, the alarming trend of increasing drug resistance of Staphylococcus aureus, particularly MRSA, has posed severe problems for healthcare authorities in infection control. The present study indicates the prevalence and antibiotic susceptibility patterns of various Staphylococcus aureus isolates identified from clinical specimens such as pus(40), urine (3) and body fluids(7). A total of 27(54%) MSSA strains and 23(46%) MRSA strains were identified. The prevalence of MRSA obtained in our study (46%) is marginally higher than those from other studies by Debnath et al(30%) 12, Goyal et al(32.6%) 1, Pai et al(29.1%) 13, Tripathi (33.33%) 14. However, studies by Surpur et al(54.91%) 15 and Savitha et al(62.14%) 16 have reported a high prevalence of MRSA. The variations seen between different studies including ours could probably be influenced by a variety of factors such as the limited sample size, duration of study, specimens collected, methods employed for detection, demography of the region, infection control and antibiotic prescribing practices. Some subtle observations were also made when the prevalence of MRSA among different age groups was analysed. The age group of >18-45 years showed highest isolation of MRSA- 13 isolates followed by 8 isolates >45-60 years age group. MSSA isolation was also highest in > 18-45 years- 12 isolates followed > 45-60 years- 9 isolates. The highest prevalence of MRSA in the younger generation could probably be due to indiscriminate or prolonged use of antibiotics, self medication, increased travel and mobility in addition to busy lifestyles with reduced attention to healthcare. Strains of Methicillin resistant Staphylococcus aureus when isolated from clinical specimens can create therapeutic difficulties since they are known to be multi-drug resistant and the alternatives available are also limited. In this study, not all the strains isolated were tested against the antibiotics in use in the hospital setting, so there is limited data available on the MRSA strains being resistant to a number of antibiotics used in our study. However majority of the strains were tested against Linezolid, Teicoplanin and vancomycin and showed 100%(49) sensitivity to Linezolid, 97.9%(47) to Teicoplanin and 96%(48) to vancomycin. These findings correlate well with studies done by Surpur et al 15, Goyal et al 1, INSAR group 17 and Tripathi 14 which showed similar susceptibilities to Linezolid, Teicoplanin and Vancomycin. Our study therefore highlights and adds to the prevailing knowledge that glycopeptides(vancomycin and Teicoplanin) and Linezolid appear to be the most effective therapeutic options available for treating MRSA infections. Vancomycin is considered inferior to B- lactams for the treatment of MSSA bacteremia and endocarditis. 18 Therefore, the first generation cephalosporins are the drugs of choice for the treatment of MSSA infections in patients who are unable to tolerate anti-staphylococcal penicillins. De-escalation of Vancomycin to beta lactams should be encouraged in all cases of MSSA. 17 With MRSA isolates being widespread, it is imperative that treating doctors deescalate to beta lactams once the culture sensitivity results reveal an MSSA isolate. Preservation of glycopeptides and Linezolid for use only in MRSA cases should be encouraged. 17 Conclusion: This study highlights the fact that MRSA continues to be a problem in healthcare institutions. This is a global phenomenon as the availability of treatment options is restricted by the few drugs available to treat them. 137
Routine and regular surveillance of MRSA and in vitro susceptibility testing, regular monitoring and update of infection control practices and antibiotic policies might change the prevailing trends of antibiotic sensitivities which will reduce the chances of MRSA infections. The use of glycopeptides and Linezolid should be reserved for use in life-threatening infections caused by MDR-MRSA so as to prevent the future emergence of resistance to these precious antibiotics. References: 1. Goyal A, Diwakar MK, Bhooshan S, Goyal S, Agrawal A. Prevalence and Antimicrobial Susceptibility Pattern of Methicillin-resistant Staphylococcus aureus[mrsa] Isolates in a Tertiary Care Hospital in Agra, North India- A systematic annual review. IOSR- Journal of Dental and Medical Sciences 2013; 11(6):80-84. 2. Anupurba S, Sen MR, Nath G, Sharma BM, Gulati AK, Mohapatra TM. Prevalence of Methicillin-resistant Staphylococcus aureus in a tertiary referral hospital in eastern Uttar Pradesh. Indian J Med Microbiol 2003; 21: 49-51. 3. Salaria M, Singh M. Methicillin resistant Staphylococcus aureus. Indian Pediatr 2001; 38: 29-36. 4. Mehta AP, Rodrigues C, Sheth K, Jani S, Hakimiyan A, Fazalbhoy N. Control of methicillin resistant Staphylococcus aureus in a tertiary care centre: A five-year study. Indian J Med Microbiol 1998; 16: 31-4. 5. Assadullah S, Kakru DK, Thoker MA, Bhat FA, Hussain N, Shah A. Emergence of low level vancomycin resistance in MRSA. Indian J Med Microbiol 2003; 21: 196-8. 6. Collee JG, Miles RS, Watt B. Test for the identification of bacteria. In: Mackie, McCartney, editors. Practical Medical Microbiology. 14th Ed. New York: Churchill Livingstone; 1996.p.131-45. 7. Clinical and Laboratory Standards Institute [CLSI]. Performance Standards for Antimicrobial disk Susceptibility Testing- Approved Standard. 10th edition. M02-A10 2009; 29(1). 8. Clinical and Laboratory Standards Institute [CLSI]. Performance Standards for Antimicrobial disk Susceptibility Testing- Approved Standard.10th edition.m100-s20 2010; 30(1). 9. Clinical and Laboratory Standards Institute [CLSI]. Performance Standards for Antimicrobial disk Susceptibility Testing. Twenty First Informational Supplement. M100-S21 2011; 31(1) 10. Clinical and Laboratory Standards Institute [CLSI]. Performance for Antimicrobial disk Susceptibility Testing-Approved Standard.11th edition.m02-a11. 2012; 32(1) 11. Chambers HF. The changing epidemiology of Staphylococcus aureus. Emerg Infect Dis 2001; 7: 178-182; https://doi.org/10.3201/eid0702.700178 12. Debnath A, Chikkaswamy BK. Antibiogram and susceptibility pattern Of methicillin-resistant Staphylococcus aureus collected from various clinical samples in Bengaluru. Asian Journal of Pharmaceutical and Clinical Research 2015; 8(6): 260-264. 13. Pai V, Rao VI, Rao SP. Prevalence and antimicrobial susceptibility pattern of methicillin-resistant Staphylococcus aureus[mrsa] isolates at a tertiary care hospital in Mangalore, South India. J Lab Physicians 2010; 2(2): 82-84; https://doi.org/10.4103/0974-2727.72155 14. Tripathi A. Prevalence and antimicrobial susceptibility pattern of methicillin resistant Staphylococcus aureus in Central India. MedPulse- International Medical Journal 2015; 2(1): 45-48. 15. Surpur RR, Patil VM, Rao A, Hegadi S, Kalpana. Prevalence of Methicillin resistance Staphylococcus aureus and antibiotic susceptibility pattern among patients admitted at Navodaya Medical College, Hospital And Research Center, Raichur. International Journal of Recent Trends in Science And Technology 2013; 9(1): 152-154. 16. Savitha P, Swetha K and Beena PM. Methicillin resistant Staphylococcus aureus and their antibiotic resistance pattern among clinical samples in a tertiary care hospital in rural South India. Asian J Adv Basic Sci 2015; 4(1):89-92. 17. Indian Network for Surveillance of Antimicrobial Resistance (INSAR) group, India. Methicillin resistant Staphylococcus aureus (MRSA) in India: Prevalence and susceptibility pattern. Indian J Med Res 2013; 137: 363-369. 138
18. Liu C, Bayer A, Cosgrove SE, Daum RS, Fridkin SK, Gorwitz RJ, et al. Clinical practice guidelines by the infectious disease society of America for the treatment of methicillinresistant Staphylococcus aureus infections in adults and children. Clin Infect Dis 2011; 52: e18-e55; https://doi.org/10.1093/cid/ciq146 Acknowledgements: The authors sincerely thank the Indian Council of Medical Research for selecting and sanctioning this student project as a part of ICMR-STS 2016 with the aim of promoting aptitude and interest in research among medical undergraduates ********************************************************************************** Conflict of interests: Nil Date of submission: 10-11-2016 Source of funding: Nil Date of acceptance: 29-12-2016 Authors details: 1. Third year M.B.B.S. student, Yenepoya Medical College, Mangalore 2. Corresponding author: Professor, Department of Microbiology, Yenepoya Medical College, Deralakatte, Mangalore 575018, Karnataka, India; E-mail: drdoms@gmail.com 139