Prevalence of High and Low Level Mupirocin Resistance among Staphylococcal Isolates from Skin Infection in a Tertiary Care Hospital

Clonal Lineage Diversity, Antibiotic Resistance, and Virulence Determinants Among Methicillin-Resistant and Methicillin-Susceptible Staphylococcus aureus Isolated from Nurses at a Teaching Hospital in Ilam, Iran: Successful Nares Decolonization by Mupirocin

BACKGROUND

Staphylococcus aureus is known to be responsible for nosocomial infections, and the typing method was useful in managing the reservoir of bacteria. The main aim of this study was to determine the prevalence of S. aureus in the nares and hands of nurses working in Imam Khomeini hospital, Ilam, Iran, as well as to determine the clonal relatedness, antimicrobial susceptibility profiles, different virulence, and resistance determinants among these isolates. The evolution of mupirocin activity in the eradication of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) colonization in the nares of the healthcare workers in Ilam, Iran, was also determined in this study.

MATERIALS AND METHODS

In this cross-sectional study, 80 nurses, auxiliary nurses, and service workers from Imam Khomeini Hospital were enrolled. MRSA, antibiotic susceptibility, and virulence determinants were evaluated. Then, the isolates were subjected to pulsed field gel electrophoresis (PFGE) and Staphylococcal cassette chromosome mec typing.

RESULTS

Our results demonstrated that 23% of isolates were MRSA. PFGE results demonstrated that pulsotypes A (3 out of 30; 10%) and J (3 out of 30; 10%), pulsotypes E (2 out of 30; 6.7%), M (2 out of 30; 6.7%), P(2 out of 30; 6.7%), and V (2 out of 30; 6.7%) were the most predominant pulsotypes, respectively.

CONCLUSION

We cannot give conclusive suggestions about the correlation between nasal carriage and infections, but we suggest the monitoring of all healthcare workers annually, decontamination of their noses by using mupirocin and other antistaphylococcal agents, and also the washing of their hands at least every 2 h.

Screening for Mupirocin Resistance in Staphylococcus

INTRODUCTION

Mupirocin is widely used topical antibiotic for the treatment of skin and soft tissue infections caused by Staphylococcus and Streptococcus. In addition nasal formulations are approved for the use in nasal eradication of methicillin-resistant Staphylococcus aureus in patients and health care workers. Wide usage of mupirocin has resulted in resistance leading to treatment failure.

AIM

To screen for the mupirocin resistance among the Staphylococcus isolates using disc diffusion and minimum inhibitory concentration method.

MATERIALS AND METHODS

A cross-sectional study was done at Microbiology Department of Sri Ramachandra University with 100 strains of Staphylococcus spp isolated from skin and soft tissue infections. Methicillin susceptibility was done by disc diffusion method using oxacillin (1 μgm) and cefoxitin (30 μgm) discs. Isolates were screened for mupirocin resistance by disc diffusion method using 5 μgm discs. High level and low level resistance determined by MIC using agar dilution method.

RESULTS

In 100 Staphylococcus spp 56 were Staphylococcus aureus and 44 were CoNS. Among the 56 Staphylococcus aureus 49 (87.5%) were mupirocin susceptible and 7 (12.5%) resistant by 5μg disc diffusion method. However by MIC method 11 (19.6%) were high and low level mupirocin resistant. Out of 44 CoNS 22 (50%) and 18 (41%) were susceptible by disc diffusion and MIC method respectively. Of the 26 resistant CoNS low level and high level mupirocin resistant was observed in 7 (15.9%) and 19 (43.1%) respectively.

CONCLUSION

Screening for mupirocin resistance by disc diffusion method is important before attempting decolonisation. Mupirocin resistance is more with CoNS. Disc diffusion method may miss low level Mupirocin resistance.

Prevalence of Mupirocin Resistance Among Staphylococci, its Clinical Significance and Relationship to Clinical Use

Introduction:

Mupirocin competitively inhibits bacterial isoleucyl transfer-RNA synthetase and inhibit bacterial protein synthesis. Widespread usage and over the counter availability of the drug has resulted in resistance among Staphylococcus species.

Objectives:

This study aimed to determine the overall prevalence of mupirocin resistance among staphylococci. Correlate clinical significance of mupirocin resistance and its relationship to clinical use.

Methods:

Consecutive, nonrepetitive, clinical isolates of Staphylococcus aureus (n = 98), and coagulase-negative staphylococci (CoNS) (n = 45) from skin and soft-tissue infections between January 2014 and June 2014 were studied. Antibiotic susceptibility testing was done according to Clinical and Laboratory Standards Institute guidelines. Low- and high-level mupirocin resistance was screened by using 5 µg and 200 µg discs respectively and confirmed by agar dilution. Annual consumption of mupirocin was studied and correlated with resistance.

Results:

High-level mupirocin resistance was found in 8.2% S. aureus and 15.6% of CoNS, while low-level mupirocin resistance was found in 17% S. aureus and 8.9% CoNS. High-level mupirocin resistance was more common in methicillin-sensitive S. aureus isolates when compared with methicillin-resistant S. aureus isolates (P < 0.05). Mupirocin resistant S. epidermidis were associated with methicillin resistance and constitutive clindamycin resistance.

Conclusion:

High prevalence of mupirocin resistance was found in the present study. Increased prevalence of mupirocin resistance among community-acquired staphylococci demands the judicious use of the drug in the community.

Preventing surgical site infections: a randomized, open-label trial of nasal mupirocin ointment and nasal povidone-iodine solution

BACKGROUND

Treatment of Staphylococcus aureus colonization before surgery reduces risk of surgical site infection (SSI). The regimen of nasal mupirocin ointment and topical chlorhexidine gluconate is effective, but cost and patient compliance may be a barrier. Nasal povidone-iodine solution may provide an alternative to mupirocin.

METHODS

We conducted an investigator-initiated, open-label, randomized trial comparing SSI after arthroplasty or spine fusion in patients receiving topical chlorhexidine wipes in combination with either twice daily application of nasal mupirocin ointment during the 5 days before surgery or 2 applications of povidone-iodine solution into each nostril within 2 hours of surgical incision. The primary study end point was deep SSI within the 3 months after surgery.

RESULTS

In the modified intent-to-treat analysis, a deep SSI developed after 14 of 855 surgical procedures in the mupirocin group and 6 of 842 surgical procedures in the povidone-iodine group (P = .1); S. aureus deep SSI developed after 5 surgical procedures in the mupirocin group and 1 surgical procedure in the povidone-iodine group (P = .2). In the per protocol analysis, S. aureus deep SSI developed in 5 of 763 surgical procedures in the mupirocin group and 0 of 776 surgical procedures in the povidone-iodine group (P = .03).

CONCLUSIONS

Nasal povidone-iodine may be considered as an alternative to mupirocin in a multifaceted approach to reduce SSI.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT01313182.