Dear Label_Name,

Greetings! I hope you are well.

I am writing on behalf of an international publishing house, Science and Education Publishing, USA (http://www.sciepub.com).

Science and Education Publishing (SciEP) is a multidisciplinary open access publisher of Journals covering the fields of Science, Technology and Medicine. All SciEP publications are subject to high-quality peer review, editorial and production processes and are freely available online.

Welcome to the April, 2013 edition of SciEP newsletter, providing monthly summaries of articles on science & education related topics of interest to scientist and professionals. The mission of our journals is to provide an open access forum for publishing new findings on issues pertinent to scientific and academic field. We also invite you to submit original research papers, review articles, short reports, or case studies are considered for publication in our Multidisciplinary Journals.

American Journal of Public Health Research
DOI: 10.12691/ajphr-1-1-3

The Implementation of a Tele-Homecare System with Service Oriented Architecture and HL7 Message Transmission Standard
Ching-Sung Wang

American Journal of Medical and Biological Research
DOI: 10.12691/ajmbr-1-1-2

The Influence of Ethanol on Pyruvate Kinases Activity in Vivo, in Vitro, in Silico
Lelevich Sergey Vladimirovich, Khrustalev Vladislav Victorovich, Barkovsky Eugene Victorovich, Shedogubova Tatyana Aleksandrovna

American Journal of Medical Sciences and Medicine
DOI: 10.12691/ajmsm-1-1-1

Clinical and Histological Features in Wegener Granulomatosis
Li Cavoli Gioacchino, Passantino Rita, Bono Luisa, Tortorici Calogera, Ferrantelli Angelo, Giammarresi Carlo, Rotolo Ugo

American Journal of Infectious Diseases and Microbiology
DOI: 10.12691/ajidm-1-1-2

The Curse of Lymphatic Filariasis: Would the Continual Use of Diethylcarbamazine Eliminate this Scourge in Papua New Guinea?
Anne Lanham, Lillian Mwanri

We have released issues of some journals on February 2013.
American Journal of Public Health Research
American Journal of Medical Sciences and Medicine
American Journal of Medical and Biological Research
American Journal of Pharmacological Sciences
American Journal of Clinical Medicine Research
American Journal of Nursing Research
American Journal of Cancer Prevention
American Journal of Medicine Studies
American Journal of Infectious Diseases and Microbiology
American Journal of Cardiovascular Disease Research
American Journal of Biomedical Research
American Journal of Mechanical Engineering
American Journal of Microbiological Research
Journal of Preventive Medicine
American Journal of Food and Nutrition
American Journal of Hypertension Research
American Journal of Sports Science and Medicine
Journal of Cancer Research and Treatment
American Journal of Zoological Research
Journal of Biomedical Engineering and Technology
American Journal of Microbiological Research
Biomedical Science and Engineering

We are pleased to announce that submissions are now being accepted for peer review for all the journals across all our subject areas in SciEP.

Please submit your manuscript via our online submission system:
http://www.sciepub.com/author/signin

To unsubscribe from our mailing list, please click on the following link: unsubscribe

I am looking forward to hearing from you.

Kind regards,

David Rain
Email:join@sciepub.com
Science and Education Publishing (http://www.sciepub.com)

Activity of Linezolid against Multidrug-resistant Gram Positive Cocci in Eastern Nepal

Mr. Suraj Timilsina

Department of Microbiology, Nepal Medical College, Jorpati, Kathmandu, Nepal

Abstract: Background: The emergence of resistance in gram-positive bacteria has necessitated a search for new antimicrobial agents. Linezolid, an oxazolidinone, is a new class of antibacterial agents with enhanced activity against pathogens. Method: The in-vitro activity of linezolid was assessed against 461 gram-positive cocci; 301 Staphylococcus spp., 150 Enterococcus spp., 5 Streptococcus pneumoniae and 5 Streptococcus pyogenes, with an emphesis on testing multidrug-resistant isolates. Results: Linezolid demonstrated potent activity against all the isolates tested at the susceptible breakpoint (≤4µg/ml). Against methicillin-resistant staphylococci and vancomycin-resistant enterococci, linezolid was the most active agent tested. Moreover, among 29.90% methicillin-resistant staphylococcal isolates, 20 exhibited intermediate susceptibility to vancomycin. Similarly, among the enterococcal isolates, 32% exhibited high level gentamicin-resistance whereas 7.33% were found to be vancomycin-resistant. None of the streptococcal isolates exhibited resistance to any of the antimicrobials tested. Conclusions: In summary, linezolid may represent an important therapeutic option for the treatment of infections caused by gram-positive cocci in Nepal.

Keywords: eastern Nepal, gram-positive cocci, linezolid

Received June 13, 2015; Revised July 18, 2015; Accepted July 28, 2015

Citation: Mr. Suraj Timilsina, Activity of Linezolid against Multidrug-resistant Gram Positive Cocci in Eastern Nepal. American Journal of Infectious Diseases and Microbiology, 3 (4). 129-133. January 2015. doi:10.12691/ajidm-3-4-2

1. Introduction

Gram-positive cocci (GPC) are responsible for a significant proportion of community-acquired and hospital-acquired infections [1]. GPC are among the most frequently isolated organisms from nosocomial bloodstream infections [2]. With the steady increase in prevalence of gram-positive infections, emergence and spread of resistance among them, the landscape of clinical infectious disease is continuously changing. Infections caused by multidrug-resistant GPC such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE) and penicillin-resistant pneumococci (PRP) has led to a search for novel antimicrobials having suitable pharmacokinetic properties and safety profiles, with activity against these resistant GPC. During the past decade, the antimicrobial arsenal against GPC infections has been extended to include several new antimicrobials such as linezolid, daptomycin, quinupristin-dalfopristin, etc.

Linezolid is the first representative of a new class of synthetic antibacterial agents, the oxazolidinones. Oxazolidinones bind to the 50S subunit of the prokaryotic ribosome thus preventing translation of the mRNA [3]. Linezolid is bacteriostatic in nature and appears promising as it is active against GPC including MRSA, VRE and PRP. It has the advantage of being available in oral formulation with almost 100% bioavailability, thus allowing an earlier switch to oral administration, and possible earlier discharge of patients from hospital. Furthermore, linezolid has excellent tissue penetration [4,5]. A meta-analysis of 12 randomised controlled trials showed that linezolid is more effective than glycopeptides or β-lactams¹. However, resistance to linezolid has been documented but cross resistance with other antimicrobials has not been reported [6,7,8].

The epidemiology of drug resistance can exhibit remarkable geographical variability and rapid evolution over time. Therefore, knowledge regarding the susceptibility pattern of local isolates to new drugs is particularly important to institute appropriate therapy against multidrug-resistant GPC. Since study on activity of linezolid has not been done so far in our settings, the proposed study aims to assess the susceptibility pattern of the GPC with special reference to activity of linezolid against them.

2. Materials and Methods

The study was carried out in Department of Microbiology, B.P. Koirala Institute of Health Sciences (BPKIHS), Dharan, Nepal from 01/06/2012 to 31/06/2013. Various clinical specimens comprising of blood, cerebrospinal fluid, corneal scrapings, urine, pus, wound swabs, sputum, aspirates, tissue and peritoneal fluid were evaluated. The entire specimens were processed following standard microbiological procedures followed by presumptive identification of GPC.

Antimicrobial susceptibility testing was performed by Kirby-Bauer disk diffusion method following the Clinical Laboratory Standard Institute (CLSI) guidelines [9]. Antimicrobial disks supplied by HiMedia laboratories, India impregnated with following antimicrobials were used: ampicillin (10µg), cefotaxime ((30µg), ciprofloxacin (5µg), chloramphenicol (30µg), co-trimoxazole (25µg), erythromycin (15µg), gentamycin (10µg), nitrofurantoin (300µg), oxacillin (1µg), penicillin (10 units), tetracycline (30µg), vancomycin (30µg), linezolid (30µg). S. aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 were used as quality control measures.

Screening for high level gentamicin resistance (HLGR) among enterococcal isolates was carried out by disk diffusion method using 120µg disk of gentamicin as recommended by the CLSI [10]. Similarly, oxacillin screening agar base was used for the detection of MRSA [11]. Minimum inhibitory concentrations (MICs) of vancomycin, gentamicin and linezolid were determined using agar dilution technique [12]. Mueller Hinton agar media was used for Staphylococcus spp. and Mueller Hinton Blood agar was used for Enterococcus spp. and Streptococcus spp. For those enterococcal isolates which were resistant even up to 256µg/ml of gentamicin, higher concentration of the antibiotic and the media were prepared.

3. Results

A total of 461 isolates comprising of 301 Staphylococcus spp., 150 Enterococcus spp., 5 Streptococcus pneumoniae and 5 Streptococcus pyogenes were included in the study. Of these, GPC were most frequently isolated from pus- 137 (29.71 %), followed by urine- 113 (24.51 %), blood- 108 (23.42%) and other different clinical specimens (Table 1).

Table 1. Distribution of strains by culture sources

3.1. Staphylococci

Of the 301 staphylococcal isolates, 52 (17.30%) were coagulase-negative staphylococci (CoNS) while 249 (82.70%) were S. aureus. Resistance to penicillin was observed in 85.71% of the staphylococcal isolates. Similarly, resistance to erythromycin was observed in the 63.45% isolates and 52.15% of the isolates exhibited resistance to cefotaxime. Likewise, methicillin-resistance was observed in 29.90% (n=90) of the isolates by both the methods (disk diffusion and MIC) of susceptibility testing. Out of the 90 isolates, 13(14.44%) were CoNS and 77(85.56%) were S. aureus (Table 2).

Table 2. Antimicrobial drug resistance profile of gram positive bacteria

Among the 90 MRSA isolates, 79(87.77%) exhibited resistance to ≥2 antimicrobial agents tested, while 75(83.33%), 39(43.33%), 33(36.66%), and 10(11.11%) exhibited resistance to ≥3, ≥4, ≥5, and 6 agents respectively. Moreover, 20 methicillin-resistant isolates exhibited intermediate susceptibility to vancomycin.

However, there were no isolates of staphylococci exhibiting resistance towards vancomycin (MIC ≥16µg/ml) and linezolid (MIC ≥4µg/ml). But, vancomycin-intermediate (MIC 8-16µg/ml) staphylococcus formed 17.60% of the total isolates (n=53; CoNS: 10, S. aureus: 43). (Table 3).

Table 3. MIC distribution for the isolates studied

3.2. Enterococci

Among 150 enterococcal isolates, most were observed to be resistant to ampicillin (92.66%). Conversely, 88.42% of urinary enterococcal isolates were susceptible to nitrofurantoin. The rate of ciprofloxacin resistance was 56.66% (Table 2).

When tested for MIC of gentamicin, 54% of the total enterococcal isolates had MIC level above the breakpoint 4µg/ml. The concentration of even 2048µg/ml could not inhibit the growth of 35 isolates (23.33%). The enterococcal isolates exhibiting MIC of gentamicin above the breakpoint of 500µg/ml were regarded as high level gentamicin resistance (HLGR). In the present study, 48 (32%) enterococcal isolates exhibited high level resistance to gentamicin. 11 isolates (7.33%) were found to be resistant to vancomycin by disk diffusion method and it was confirmed by MIC. 8 (5.33%) of the isolates exhibited intermediate susceptibility to vancomycin (MIC 8-16µg/ml) and majority i.e. 60 (40%) of the isolates had MIC of 2µg/ml. Linezolid-resistance was not observed in our study. Similarly, when tested for MIC of linezolid, all of them showed MIC ≤4µg/ml, half of them with MIC of 1µg/ml. (Table 3)

Among the 95 urinary enterococcal isolates, 91.57% exhibited resistance to ≥2 antimicrobial agents tested, while 55(57.89%), 46(48.42%), 35(36.84%), and 11(11.57%) exhibited resistance to ≥3, ≥4, ≥5 and 6 agents respectively. And among the non-urinary enterococcal isolates (n= 55), 48(87.27%) exhibited resistance to ≥2 agents, while 31 (56.36%), 23 (41.81%), 14 (25.91%) and 4 (7.27%) exhibited resistance to ≥3, ≥4, ≥5 and 6 agents respectively. Moreover, among the 19 vancomycin-resistant and intermediate isolates, 10 (52.63%) had HLGR.

3.3. Streptococci

None of the streptococcal isolates exhibited resistance to any of the antimicrobials tested. The MIC range (in µg/ml) of all the isolates ranged from 0.03125 to 0.5 for vancomycin and 0.03125 to 0.125 for linezolid. (Table 3).

4. Discussion

In the present study, a total of 461 isolates of GPC recovered from various clinical samples were evaluated for their antimicrobial susceptibility patterns with special reference to linezolid.

Linezolid was found to be active against all the GPC tested, with MICs in the narrow range of 0.03-4µg/ml which is in concordance with the findings of others [13]. Among the 90 methicillin-resistant staphylococci in the current study, the simultaneous resistance to two or more antimicrobials was seen in 79(87.77%). Similar findings were seen in SENTRY Surveillance Programs, where, MRSA resistant isolates in United States, Canada, Latin America, Europe and Western Pacific exhibited co-resistance to other drugs [14,15]. The rate of isolation of MRSA in various studies in India ranged from 33% to 52.9% [16,17]; 50% in Pakistan [18] which was higher than that of our studies (29.90%). Similar study done in Nepal showed lower rate of MRSA isolation (15.4% [19], 26.14% [20] 25.33% [21]).

Because of the widespread occurrence of MRSA, the empiric therapy for staphylococcal infections was changed to vancomycin with a discernible increase in its use. As a consequence, selective pressure was established which lead to emergence of strains of S. aureus and other species of staphylococci with decreased susceptibility to vancomycin and other glycopeptides. Vancomycin-intermediate staphylococcus formed 17.60% (n=53) (CoNS: 10; S. aureus: 43) of the total isolates. None of the isolates were found to be vancomycin-resistant. However, in various studies vancomycin-resistance or vancomycin-intermediate staphylococci were found to be 0.003% to as high as 42%. Similar study in BPKIHS showed the prevalence of vancomycin intermediate S. aureus to be 26.66% whereas none of the isolate was vancomycin-resistant S. aureus [21]. In addition, 20 methicillin-resistant isolates exhibited intermediate susceptibility to vancomycin in this study.

Similarly, the simultaneous resistance to two or more antimicrobials by the enterococcal species in this study, i.e. 91.57% urinary isolates and 87.27% other non-urinary isolates, is much higher than 34% multidrug-resistance as observed by Udo et al., 2003 [22]. However, the resistance pattern is similar to that observed in a study conducted previously in BPKIHS, i.e. 96.23% for urinary isolates and 80.70% for other non-urinary isolates [23].

In a study conducted by Hayden et al., 1994 [24], 53.84% VRE isolates exhibited HLGR. In our study, 52.63% vancomycin intermediate and resistant isolate exhibited HLGR. The acquisition of resistance to vancomycin by enterococci demonstrates how an organism that usually behaves as a second-rate pathogen can become a first-rate clinical problem. The emergence of this resistance also has raised concerns about its possible transfer into other GPC. It is known that some plasmids can survive and replicate in enterococci, streptococci and staphylococci as well as in other various gram-positive bacteria and that these different organisms often have some of the same resistance genes [25]. In this study, no enterococcal isolate was found to be resistant to linezolid.

Furthermore, none of the streptococcal isolates exhibited resistance to any of the antimicrobials tested. However, in a study done at the same hospital from January 2000 to June 2001, 4% of the pneumococcal strains showed resistance to penicillin. Concomitant resistance to chloramphenicol, erythromycin and co-trimoxazole was observed in 7% of isolates [26].

5. Conclusions

Our findings confirmed that linezolid is consistently active against multidrug-resistant gram-positive pathogens including MRSA, VRE, and others. Even though linezolid-resistance was not observed in our present study, to prevent the emergence of resistance, linezolid should be used strictly after the therapeutic indications and the courses of treatment kept as short as possible. However, active surveillance is needed for discovery and containment of the resistance as sporadic cases of resistance to this novel drug (linezolid) has been reported from various parts of the world.

Acknowledgements

We are sincerely thankful to the technical staffs of Department of Microbiology, BPKIHS, Dharan, in helping us to conduct this work. In addition, we are grateful to the staffs of Blood Bank, Dharan for their continuous help and support.

Author Disclosure Statement

There is no any conflict of interest. This work was not supported by any grant.

References

[1]   | M. E. Falagas, I. I Siempos and K. V. Vardakas, “Linezolid versus glycopeptide or β- lactam for treatment of gram-positive bacterial infections: meta-analysis of randomised controlled trials,” Lancet Infectious Disease, vol. 8, pp. 53-66, 2008.
[2]   | D. J. Biedenbach, G. J. Moet and R.N. Jones, “Occurrence and antimicrobial resistance pattern comparisons among bloodstream infection isolates from the SENTRY Antimicrobial Surveillance Program (1997-2002),” Diagnostic Microbiology and Infectious Disease, vol. 50, pp. 59-69, 2004.
[3]   | D. M. Livermore, “Linezolid in vitro: mechanism and antibacterial spectrum,” Journal of Antimicrobial Chemotherapy, vol. 51, S2, pp. ii9-16, 2003.
[4]   | J. G. Slatter, D. J. Stalker, K. L. Feenstra et al., “Pharmacokinetics, metabolism, and excretion of linezolid following an oral dose of linezolid to healthy human subjects,” Drug Metabolism and Disposition, vol. 29, pp. 1136-45, 2001.
[5]   | P. Beringer, M. Nguyen, N. Hoem et al., “Absolute bioavailability and pharmacokinetics of linezolid in hospitalized patients given enteral feedings,” Antimicrobial Agents Chemotherapy, vol. 49, pp. 3676-81, 2005.
[6]   | R. D. Gonzales, P. C. Schreckenberger, M. B. Graham et al., “Infections due to vancomycin resistant Enterococcus faecium resistant to linezolid,” Lancet, vol. 357, pp. 1179, 2001.

[7]  
L. M. Deshpande, T. R. Fritsche, G. J. Moet et al., “Antimicrobial resistance and molecular epidemiology of vancomycin-resistant enterococci from North America and Europe: a report from the SENTRY antimicrobial surveillance program,” Diagnostic Microbiology and Infectious Disease, vol. 58, pp. 163-70, 2007.

[8]   | S. M. Toh, L. Xiong, C. A. Arias et al., “Acquisition of a natural resistance gene renders a clinical strain of methicillin resistant Staphylococcus aureus resistant to the synthetic antibiotic linezolid,: Molecular Microbiology, vol. 64, pp. 1506-14, 2007.
[9]   | Clinical and Laboratory Standards Institute, Performance standards for Antimicrobial Susceptibility testing. 9th ed. Approved Standard. Wayne, PA: Clinical and Laboratory Standards Institute (CLSI document no. M2-A9), 2006.
[10]   | Clinical and Laboratory Standards Institute, Performance standards for Antimicrobial Susceptibility testing. 16th informational supplement. Wayne, PA: Clinical and Laboratory Standards Institute (CLSI document no. M100-S16), 2006.
[11]   | P. R. Murray, E. J. Baran, M. A. Pfalle, Fred, Tenover, R. Yolke, “Special Tests for detecting Antimicrobial resistance,” in Manual of Clinical Microbiology, Washington ASM, 8th edition, 1995.
[12]   | J. F. Acar and F. W. Goldstein, “Disk susceptibility test" In: Lorain V, editor. Antibiotics in laboratory medicine, 4th ed., Maryland: William and Wilkins, pp. 28-32, 1996.
[13]   | R. Wise, J. M. Andrews, F.J. Boswell and J. P. Ashby, “The in-vitro activity of linezolid (U-100766) and tentative break-points,” Journal of Antimicrobial Chemotherapy, vol. 42 pp. 721-8, 1998.

[14]  
D. Diekema, Pfaller, F. J. Schmitz et al. “SENTRY Participants Group.Survey of Infections Due to Staphylococcus Spp.: Frequency of Occurrence and Antimicrobial Susceptibility of Isolates Collected in the United States, Canada, Latin America, Europe, and the Western Pacific Region for the SENTRY Antimicrobial Surveillance Program, 1997-1999,” S114 • CID 32 (Suppl 2), 2001.

[15]  
M. J. Gary, J. N. Ronald, B. J. Douglas, S. G. Matthew, F. R Thomas, “Contemporary causes of skin and soft tissue infections in North America, Latin America, and Europe: Report from the SENTRY Antimicrobial Surveillance Program 1998-2004,” Diagnostic Microbiology and Infectious Disease, Vol. 57, pp. 7-13, 2007.

[16]   | S. Mulla, M. Patel, L. Shah and Vaghela G, “Study of antibiotic sensitivity pattern of Methicillin Resistant Staphylococcus aureus,” Indian Journal of Critical Care Medicine, vol. 11, 2007.
[17]   | S. Anupurba, M. R. Sen, G. Nath, B. M. Sharma, A. K. Gulati and T. M. Mohapatra, “Prevalence of Methicillin Resistant Staphylococcus aureus in a tertiary referral hospital in eastern Uttar Pradesh,” Indian Journal of Medical Microbiology, vol. 21, pp. 49-51, 2003.
[18]   | K. Farzana and A. Hameed, “Resistance Patterns Of Clinical Isolates of Staphylococcus aureus against 7 groups of Antibiotics,” Journal of Research (Science), vol. 11, pp. 19-28, 2006.
[19]   | S. Subedi and K. N. Brahmadathan, “Antimicrobial susceptibility pattern of clinical isolates of Staphylococcus aureus in Nepal,” Clinical Microbiology and Infection, vol. 11, pp. 235-7, 2005.
[20]   | S. Kiran and R. Chitra, “Antibiotic susceptibility patterns of Staphylococcus aureus,” Journal of Nepal Medical Association, vol. 40 pp. 138, 2001.
[21]   | R. Baral, B. Khanal and A. Acharya, “Antimicrobial susceptibility patterns of clinical isolates of Staphylococcus aureus in eastern Nepal,” Health Renaissance, vol. 9 pp. 78-82, 2011.
[22]   | E. E. Udo, N. Al-Sweih, A. Oludotun, Phillips and T. D. Chugh, “Species prevalence and antibacterial resistance of enterococci isolated in Kuwait hospitals,” Journal of Medical Microbiology, vol. 52 pp. 163-168, 2003.
[23]   | H. Nepal, B. Khanal and A. Acharya, “Characterization and Antimicrobial Resistance of clinical isolates of enterococci in tertiary care hospital in eastern Nepal,” Health Renaissance, vol. 11 pp. 17-22, 2013.
[24]   | M. K. Hayden, G. L. Koenig and G. M. Trenholme, “Bactericidal activities of antibiotics against vancomycin resistant Enterococcus faecium blood isolates and synergistic activities of combination,” Antimicrobial Agents Chemotherapy, vol. 38, pp. 1225-29, 1994.
[25]   | S. Tsiodras, H. S. Gold, G. Sakoulas et al. “Linezolid resistance in a clinical isolate of Staphylococcus aureus,” Lancet, vol. 358, pp. 207-8, 2001.
[26]   | B. Khanal, S. K. Sharma, M. Deb and S. K. Bhattacharya, “Pneumococcal infections: Report of a hospital based study,” Journal of Nepal Medical Association, vol. 41, pp. 397-400, 2002.