Indian Journal of Medical Microbiology Medknow Publications on behalf of Indian Association of Medical Microbiology ISSN: 0255-0857 EISSN: 1998-3646 Vol. 29, Num. 1, 2011, pp. 60-62

Indian Journal of Medical Microbiology, Vol. 29, No. 1, January-March, 2011, pp. 60-62

Case Report

Sepsis due to linezolid resistant Staphylococcus cohnii and Staphylococcus kloosii: First reports of linezolid resistance in coagulase negative staphylococci from India

MA Peer, RA Nasir, DK Kakru, BA Fomda, G Bashir, IA Sheikh

Department of Clinical Microbiology, Sher-i-Kashmir Institute of Medical Sciences (SKIMS), Soura, Srinagar, Kashmir - 190 011, India

Correspondence Address: M A Peer, Department of Clinical Microbiology, Sher-i-Kashmir Institute of Medical Sciences (SKIMS), Soura, Srinagar, Kashmir - 190 011, India, maroofpeer@gmail.com

Date of Submission: 18-May-2009
Date of Acceptance: 30-Nov-2010

Code Number: mb11014

PMID: 21304198

DOI: 10.4103/0255-0857.76527

Abstract

Keywords: Linezolid resistance, Staphylococcus cohnii, Staphylococcus kloosii

Introduction

Linezolid, the first oxazolidinone introduced in 2000, has demonstrated potent antimicrobial activity against gram-positive organisms, including methicillin resistant Staphylococcus aureus (MRSA), methicillin resistant coagulase negative staphylococci (MR-CoNS), vancomycin resistant enterococci (VRE) and multidrug resistant (MDR) Streptococcus pneumoniae. ^[1] Linezolid uniquely inhibits protein synthesis at an early step by binding to the domain V region of 23S rRNA, thereby preventing formation of the N-formyl methionyl-tRNA-mRNA-70S ribosomal tertiary complex. Resistance to linezolid has been largely associated with mutations in the central loop of the domain V region of the 23S rRNA gene. ^[2]

Despite a decade of its clinical use, resistance to linezolid has remained stable and extremely low with only sporadic cases being reported mostly from USA and Europe. ^[3],[4] Most of the Asian countries have not reported even a single case of linezolid resistance in staphylococcal isolates. ^{[4],[5],[6],[7]} Linezolid resistance in coagulase negative staphylococci has not been reported from India before. An extensive search through PubMed did not reveal any published articles from India on resistance of coagulase negative staphylococci to linezolid. We hereby present two patients with documented linezolid resistant, coagulase negative staphylococcal sepsis, for the first time from India.

Case Reports

Case 1

An 18-year-old female, after sustaining greater than 45% full thickness stove burn, was admitted on 29/07/2009 in the Plastic Surgery Department of our hospital which is a 600-bedded multispeciality tertiary care centre. After initial resuscitation and burn wound management, she underwent multiple skin graft surgeries during her hospital course. Numerous cultures from infected burn wounds and graft sites during this period grew multidrug resistant Pseudomonas aeruginosa, MRSA and MR-CoNS. She received multiple antibiotics that included cefoperazone-sulbactum, pipercillin-tazobactum, gentamicin, ciprofloxacin and linezolid. One month after admission, she underwent a major split thickness skin grafting (STSG) surgery. Postoperatively, she was put on pipercillin-tazobactum. On the 3rd postoperative day, the patient developed high-grade fever (104ºF), appeared toxic and had a pulse of 130/minute and a respiratory rate of 24/minute. Her WBC count was 26,000/μl with 90% neutrophils. C-reactive protein (CRP) levels were raised (>16 mg/l). Three sets of blood cultures drawn aseptically from different venipuncture sites at 0, 24 and 48 hours grew linezolid resistant, coagulase negative Staphylococcus. Coagulase negativity was established using conventional tests for clumping factor, tube coagulase, deoxyribonuclease (DNase), thermostable enodonuclease and mannitol fermentation. The isolate was negative for all the tests. However, further identification to species level done by API ID32 STAPH (bioMerieux Sa F-69280 Marcy I′Etoile, France) revealed the isolate to be Staphylococcus cohnii subspecies cohnii. Susceptibility testing was performed by Kirby Bauer disc diffusion method according to CLSI guidelines. ^[8] By disc diffusion, the isolate was found to be sensitive to vancomycin, teicoplanin, tigecycline, ciprofloxacin, ofloxacin and amikacin, but resistant to penicillin, oxacillin, erythromycin, clindamycin, gentamicin, cotrimoxazole and linezolid. Growth up to the edge of a 30-μg linezolid disc was recorded. (Antibiotic discs used were purchased from HiMedia laboratories, Mumbai, India.) Minimum inhibitory concentrations (MICs) of oxacillin, vancomycin and linezolid were determined using CLSI broth microdilution methodology. MIC endpoints were read after an incubation period of 16-24 hours. ^[9] The MIC for oxacillin was >4 μg/ml, vancomycin 0.25 μg/ml and linezolid >256 μg/ml. (Susceptibility grade powders of oxacillin and vancomycin were obtained from Sigma, St. Louis, MO, USA, and linezolid from Pfizer, New York, USA.) Linezolid non-susceptible phenotype was confirmed by Etest (AB Biodisk, Solna, Sweden) which showed an MIC of >256 μg/ml [Figure - 1]. Staphylococcus aureus ATCC 29213 was used as quality control. An independent and blinded verification of resistance was done at Sheri-Kashmir Medical College, Bemina, Srinagar. The patient was put on intravenous vancomycin and ciprofloxacin. Subsequent blood cultures after 4 days of IV antibiotic therapy were sterile.

Case 2

A 60-year-old male, after suffering an intracranial bleed, was admitted to the Department of Neurology on 22/02/2010. On the 4th day of hospitalisation, the patient was febrile with a temperature of 103ºF, pulse of 120/minute and respiratory rate of 30/minute, while he was on intravenous ceftriaxone-sulbactum. Laboratory investigations revealed a WBC count of 24,000/μl with 85% neutrophils and CRP levels were raised (>32 mg/l). Three sets of blood cultures drawn aseptically from different venipuncture sites at 0, 24 and 48 hours grew linezolid resistant, coagulase negative Staphylococcus. Coagulase negativity was established using conventional tests for clumping factor, tube coagulase, deoxyribonuclease (DNase), thermostable enodonuclease and mannitol fermentation. The isolate was negative for all the tests. However, further identification to species level done by API ID32 STAPH (bioMerieux Sa F-69280 Marcy I′Etoile, France) revealed the isolate to be Staphylococcus kloosii. By disc diffusion, the isolate was found to be sensitive to ciprofloxacin, genatmicin, amikacin, vancomycin, teicoplanin, and tigecycline. It was, however, resistant to penicillin, oxacillin, erythromycin, clindamycin, cotrimoxazole, ofloxacin and linezolid. Around linezolid disc, an outer thick and an inner thin zone of growth extending up to the edge of the disc could be easily visualised. MICs of oxacillin, vancomycin and linezolid, as determined using CLSI broth microdilution, were >4, 0.5 and >32 μg/ml, respectively. Linezolid non-susceptible phenotype was confirmed by Etest. MIC by Etest was >16 μg/ml [Figure - 2]. Sta. aureus ATCC 29213 was used as quality control. An independent and blinded verification of resistance was done at Sheri-Kashmir Medical College, Bemina, Srinagar. However, the patient, who was put on intravenous vancomycin and amikacin, expired 9 days after admission.

Discussion

Resistance to linezolid remains rare. According to LEADER programme, monitoring and tracking linezolid resistance in the US since 2004, as of May 2007, nearly all Sta. aureus strains (>99.9%) and CoNS (98.4%) isolated in the US were susceptible to linezolid. ^[3] A similar worldwide programme, the "Zyvox Annual Appraisal of Potency and Spectrum Study" or ZAAPS, conducted since 2002, as of 2007, revealed the overall resistance to linezolid in 23 countries to be less than 0.2% and nonexistent in streptococci. ^[4] A previous SENTRY study of gram-positive bacteria (n ≥ 40,000) reported a single linezolid resistant isolate of Staphylococcus epidermidis from the USA only. ^[10]

Data on linezolid resistance from Asian countries are scarce with most of them having not reported on resistance in staphylococci. Staphylococcal linezolid resistance in India is extremely rare except for that reported in two South Indian studies which observed a few Sta. aureus isolates resistant to linezolid on Kirby Bauer disc diffusion testing. ^[11],[12] However, resistance was not confirmed in either study by any recommended method and the isolates were clinically insignificant. Linezolid resistance in coagulase negative staphylococci in India and other South Asian countries of Pakistan, Bangladesh, Srilanka, Nepal and Bhutan has not been reported in literature to the best of our knowledge. Numerous studies done across these countries have reported 100% susceptibility to linezolid in both Sta. aureus and other coagulase negative staphylococcal isolates. ^[5],[6],[7] The cases being described here are the first ever reports of documented linezolid resistance in coagulase negative staphylococcal isolates from India.

The first patient had been on oral linezolid for more than 28 days before we isolated linezolid resistant Sta. cohnii from multiple blood cultures. However, multiple swabs taken previously from infected burn wounds/graft sites and subsequently from anterior nares, axilla, infected raw areas and graft sites revealed no linezolid resistant isolates. The second patient from whom linezolid resistant Sta. kloosii was isolated had no history of prior linezolid intake. Swabs taken from other patients in the ward, hands and anterior nares of healthcare providers and close contacts did not reveal any linezolid resistant isolates in both the cases. Most of the linezolid resistance reported in staphylococci has emerged after prolonged exposure to linezolid. However, some linezolid resistant isolates have been isolated from patients with no prior linezolid exposure. ^[13],[14]

With the ever increasing number of immuno-compromised patients, prolonged hospital stays, frequent interventions and use of intravascular devices, coagulase negative staphylococci are emerging as important pathogens capable of causing life-threatening infections. Alarming rise in methicillin resistance in Sta. aureus and other coagulase negative staphylococci is limiting the utility of all betalactam agents, thus considerably limiting the therapeutic options. Linezolid is a viable solution for methicillin resistant staphylococcal isolates. However, emerging resistance to linezolid is a matter of great concern. It is high time that we recognise the far reaching consequences posed by such a great threat and closely monitor and track resistance to linezolid by prospective resistance surveillance studies, particularly where frequent and extended linezolid therapy is used. Such surveillance studies are already in place in the western world. Paucity of newer antimicrobials demands judicious use of linezolid to preserve its clinical utility, more than ever before.

References

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11.	Vinodhkumaradithyaa A, Uma A, Srinivasan M, Ananthalakshmi I, Nallasivam P, Thirumalaikolundu subramanian P. Nasal carriage of methicillin- resistant Staphylococcus aureus among surgical unit staff. Jpn J Infect Dis 2009;62:228-9.  Back to cited text no. 11
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14.	Anderegg TR, Sader HS, Fritsche TR. Trends in linezolid susceptibility patterns: Report from the 2002-2003 worldwide Zyvox Annual Appraisal of Potency and Spectrum (ZAAPS) Program. Int J Antimicrob Agents 2005;26:13-21.  Back to cited text no. 14

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