Activity of Mupirocin and 14 Additional Antibiotics against Staphylococci Isolated from Latin American Hospitals: Report from the SENTRY Antimicrobial Surveillance Program

Mupirocin resistance in Staphylococcus aureus: A systematic review and meta-analysis

OBJECTIVES

Staphylococcus aureus is one of the most common pathogens causing nosocomial and community-acquired infections associated with high morbidity and mortality. Mupirocin has been increasingly used for treatment of methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) infections. The aim of this study was to determine the prevalence of mupirocin-resistant S. aureus (MuRSA), mupirocin-resistant MRSA (MuRMRSA), high-level MuRSA (HLMuRSA) and high-level MuRMRSA (HLMuRMRSA) worldwide.

METHODS

Online databases including Medline, Embase and Web of Science were searched (2000-2018) to identify studies addressing the prevalence of MuRSA, MuRMRSA, HLMuRSA and HLMuRMRSA. STATA v. software was used to interpret the data.

RESULTS

Of the 2243 records identified from the databases, 30 and 63 studies fulfilled the eligibility criteria for MuRSA and MuRMRSA, respectively. Finally, 27 and 60 studies were included separately for HLMuRSA and HLMuRMRSA, respectively. The analyses revealed pooled and averaged prevalences of MuRSA, MuRMRSA, HLMuRSA and HLMuRMRSA of 7.6% [95% confidence interval (CI) 6.2-9.0%], 13.8% (95% CI 12.0-15.6%), 8.5% (95% CI 6.3-10.7%) and 8.1% (95% CI 6.8-9.4%), respectively.

CONCLUSION

Overall, these results show a global increase in the prevalence of HLMuRSA and HLMuRMRSA among clinical S. aureus isolates over time. However, there was only a significant increase in the prevalence of MuRMRSA compared with the other categories, especially MuRSA. Since mupirocin remains the most effective antibiotic for MSSA and MRSA decolonisation both in patients and healthcare personnel, a reduction of its effectiveness presents a risk for invasive infection. Monitoring of mupirocin resistance development remains critical.

Nasal vestibulitis due to targeted therapies in cancer patients

BACKGROUND AND PURPOSE

Cancer patients treated with targeted therapies (e.g., epidermal growth factor receptor inhibitors) are susceptible to dermatologic adverse events (AEs) including secondary skin infections. Whereas infections such as paronychia and cellulitis have been reported, nasal vestibulitis (NV) has not been described with the use of these agents. The aim of our study was to characterize NV in cancer patients treated with targeted therapies.

METHODS

We utilized a retrospective chart review of cancer patients who had been referred to dermatology and were diagnosed with NV. We recorded data including demographics, referral reason, underlying malignancy, targeted anticancer regimen, NV treatment, and nasal bacterial culture results.

RESULTS

One Hundred Fifteen patients were included in the analysis, of which 13 % experienced multiple NV episodes. Skin rash was the most common reason (90 %) for a dermatology referral. The most common underlying malignancies were lung (43 %), breast (19 %), and colorectal (10 %) cancer. Sixty-eight percent of patients had been treated with an EGFRI-based regimen. Nasal cultures were obtained in 60 % of episodes, of which 94 % were positive for one or more organisms. Staphylococcus aureus was the most commonly isolated organism [methicillin-sensitive S. aureus 43 %; methicillin-resistant S. aureus 3 %].

CONCLUSIONS

We report the incidence and characteristics of an unreported, yet frequent dermatologic condition in cancer patients treated with targeted therapies. These findings provide the basis for additional studies to describe the incidence, treatment, and consequences of this event. A better understanding of NV would mitigate its impact on patients' quality of life and risk for additional dermatologic AEs.

Retapamulin: a semisynthetic pleuromutilin compound for topical treatment of skin infections in adults and children

Retapamulin is a semisynthetic pleuromutilin compound with in vitroactivity against Gram-positive bacteria, no cross-resistance to other classes of antimicrobial agents in current use and a low potential for development of resistance. A 1% ointment formulation has been developed for clinical use, and a placebo-controlled trial of impetigo in 210 patients produced significantly higher rates of clinical and microbiological success compared with placebo - 85.6 versus 52.1% and 91.2 versus 50.9%, respectively. Additional comparative studies in over 1900 patients showed noninferiority to topical fusidic acid and oral cephalexin and a low frequency of adverse events. In 2007, retapamulin was approved in the USA for topical treatment of impetigo caused by Streptococcus pyogenes and methicillin-susceptible Staphylococcus aureus, and in the EU for topical treatment of impetigo and infected wounds caused by S. pyogenes and S. aureus, with approvals including adults and children over 9 months of age.

Anti-MRSA agents: under investigation, in the exploratory phase and clinically available

Staphylococcal infections are difficult to treat due to the rapid emergence of methicillin-resistant staphylococci and, unfortunately, vancomycin-intermediate or -resistant staphylococci. Numerous alternative treatments are urgently required. In this special report, intensive research of new molecules is highlighted--in known antibacterial families and new medicinal chemical entities.

Retapamulin ointment twice daily for 5 days vs oral cephalexin twice daily for 10 days for empiric treatment of secondarily infected traumatic lesions of the skin

INTRODUCTION

Retapamulin is a novel, topical antibacterial of the pleuromutilin class in development for the treatment of secondarily infected traumatic lesions of the skin.

METHODS

The efficacy, safety, and tolerability of topical retapamulin ointment, 1% for 5 days twice daily was evaluated in 2 identical, randomized, double-blind, double-dummy, multicenter studies vs oral cephalexin, 500 mg twice daily for 10 days, in 1904 patients with secondarily infected traumatic lesions.

RESULTS

Clinical success rates were 89.5% in protocol-adherent patients receiving retapamulin compared with 91.9% for cephalexin (treatment difference, -2.5% [95% confidence interval, -5.4% to 0.5%]). In patients with Staphylococcus aureus or Streptococcus pyogenes at baseline, clinical success was 89.2% (365/409) for retapamulin and 92.6% (63/68) for cephalexin. Safety and tolerability were similar between treatments. Noncompliance (defined as using or taking <80% of doses) was recorded in 8.0% (51/636) of patients taking cephalexin compared with 0.39% (5/1268) of patients receiving retapamulin.

CONCLUSIONS

Retapamulin offers a novel, effective, and convenient topical treatment for secondarily infected traumatic lesions.

Topical retapamulin ointment (1%, wt/wt) twice daily for 5 days versus oral cephalexin twice daily for 10 days in the treatment of secondarily infected dermatitis: results of a randomized controlled trial

BACKGROUND

New antibacterial agents with activity against pathogenic strains resistant to established antibiotics are needed to treat patients with secondarily infected dermatitis (SID).

OBJECTIVE

We sought to determine the clinical safety and efficacy of topical retapamulin ointment 1% versus oral cephalexin for the treatment of SID.

METHODS

Patients with SID were randomly assigned to retapamulin ointment 1% (twice daily [bid]) for 5 days, or oral cephalexin (500 mg bid) for 10 days. The primary efficacy end point was clinical response at follow-up. Secondary outcomes included microbiologic response at follow-up, safety, and compliance.

RESULTS

Retapamulin was as effective as cephalexin (clinical success rates at follow-up: 85.9% and 89.7%, respectively). Microbiologic success rates at follow-up were 87.2% for retapamulin and 91.8% for cephalexin. Retapamulin was well tolerated and the topical formulation was preferred over the oral drug.

LIMITATIONS

An imbalance existed in the number of patients with the clinical outcome "unable to determine" (15 retapamulin, 2 cephalexin), mainly because of their failure to attend the study visit. If those who failed to attend visits (who did not withdraw as a result of drug-related events) are removed from the analysis, the clinical success rates are 89.9% for retapamulin and 89.7% for cephalexin.

CONCLUSIONS

Retapamulin ointment 1% (bid) for 5 days was as effective as oral cephalexin (bid) for 10 days in treatment of patients with SID, and was well tolerated.

Molecular analysis of isoleucyl-tRNA synthetase mutations in clinical isolates of methicillin-resistant Staphylococcus aureus with low-level mupirocin resistance

Emergence and spread of low-level mupirocin resistance in staphylococci have been increasingly reported in recent years. The aim of this study was to characterize missense mutations within the chromosomal isoleucyl-tRNA synthetase gene (ileS) among clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) with low-level mupirocin resistance. A total of 20 isolates of MRSA with low-level mupirocin resistance (minimal inhibitory concentration, 16-64 microg/mL) were collected from 79 patients in intensive care units for six months. The isolates were analyzed for isoleucyl-tRNA synthetase (IleS) mutations that might affect the binding of mupirocin to the three-dimensional structure of the S. aureus IleS enzyme. All isolates with low-level mupirocin resistance contained the known V588F mutation affecting the Rossman fold, and some of them additionally had previously unidentified mutations such as P187F, K226T, F227L, Q612H, or V767D. Interestingly, Q612H was a novel mutation that was involved in stabilizing the conformation of the catalytic loop containing the KMSKS motif. In conclusion, this study confirms that molecular heterogeneity in ileS gene is common among clinical MRSA isolates with low-level mupirocin resistance, and further study on clinical mutants is needed to understand the structural basis of low-level mupirocin resistance.

Clonal composition of Staphylococcus aureus isolates at a Brazilian university hospital: identification of international circulating lineages

In only a few instances has the clonal composition of Staphylococcus aureus collections that include methicillin-susceptible S. aureus (MSSA) been extensively characterized. In order to investigate the clonal composition of MSSA and methicillin-resistant S. aureus (MRSA) and examine whether the infections diagnosed at our hospital were related to internationally distributed S. aureus lineages, we collected 89 clinical S. aureus isolates from patients at a public university hospital in Rio de Janeiro, Brazil, from September 1999 to June 2000. All S. aureus isolates were genotyped by pulsed-field gel electrophoresis and multilocus restriction fragment typing (MLRFT), and a subset (n = 17) was further characterized by multilocus sequence typing (MLST). The 34 MRSA isolates were additionally characterized by SCCmec typing. The MSSA population (n = 55) was grouped into 18 restriction fragment types (RFTs); of these, five RFTs accounted for 67% (37) of the MSSA isolates. MRSA isolates were clustered into only three RFTs (P = 0.02). The majority of MSSA RFTs were related to sequence type 30 (ST30) (12 isolates, 22%), ST1, ST188, and ST432 (6 isolates, 11% each). The predominant MRSA RFT comprised 31 (91%) of 34 isolates; four randomly selected isolates of this RFT were ST239, the previously described widely disseminated Brazilian clone. However, a fifth isolate belonging to this RFT was the ST644, a new single locus variant of ST239. By applying MLRFT and MLST, we found evidence for a clonal structure in MSSA isolates and detected the dissemination of MSSA clonal complexes 1, 5, 8, 30, and 45.

Risk factors for isolation of low-level mupirocin-resistant versus -susceptible methicillin-resistant Staphylococcus aureus from patients in intensive care units

OBJECTIVES

The aim of this study was to determine the risk factors for the recovery of low-level mupirocin-resistant (mup(r)) or -susceptible (mup(s)) MRSA from patients in intensive care units (ICUs).

METHODS

A case-case-control study was conducted from November 2003 to April 2004. Two case groups consisted of patients with low-level mup(r) MRSA and mup(s) MRSA. A control group was frequency matched.

RESULTS

Mup(r) MRSA and mup(s) MRSA were isolated from 20 to 51 patients, respectively, during a six-month period. Risk factors identified for mup(r) MRSA were as follows: exposure to piperacillin-tazobactam (odds ratio [OR] 13.8; 95% confidence intervals [CI], 1.8-105.0), third-generation cephalosporins (OR, 5.0; 95% CI, 1.6-15.5) and quinolones (OR, 3.4; 95% CI, 1.1-10.7). Risk factors identified for mup(s) MRSA were as follows: length of ICU stay (OR, 1.1; 95% CI, 1.0-1.1), surgery (OR, 3.7; 95% CI, 1.5-9.0), exposure to third-generation cephalosporins (OR, 8.4; 95% CI, 3.3-21.7) and quinolones (OR, 7.7; 95% CI, 2.8-21.3).

CONCLUSIONS

Our results suggest that nosocomial isolation of low-level mup(r) MRSA may be affected by piperacillin-tazobactam.

Safety of Targeted Perioperative Mupirocin Treatment for Preventing Infections After Cardiac Surgery

BACKGROUND

Indiscriminate antibiotic use may lead to development of antibiotic resistance. Preoperative mupirocin treatment decreases Staphylococcus aureus carriage and may reduce subsequent surgical site infection, but is unlikely to benefit noncarriers. This study was undertaken to evaluate whether avoiding mupirocin in noncarriers places them at increased risk for subsequent postoperative infection.

METHODS

We conducted a retrospective cohort study examining incidence of postoperative infection in patients undergoing cardiac surgery at the Cleveland Clinic after introduction of a protocol of polymerase chain reaction screening for nasal S aureus carriage, and avoiding mupirocin treatment of noncarriers.

RESULTS

Between August 1, 2002, and May 31, 2004, 6,334 patients were screened for nasal carriage of S aureus before undergoing cardiac surgery. There was no significant difference in infection rates between carriers and noncarriers when examining the incidence of all infections (5.6% and 5.0%; relative risk [RR] 1.11 [95% confidence interval (CI): 0.86 to 1.43]), infections caused specifically by S aureus (1.04% and 0.80%; RR 1.30 [95% CI: 0.71 to 2.39]), any surgical site infection (3.1% and 3.2%; RR 0.97 [95% CI: 0.69 to 1.36]), S aureus surgical site infection (0.82% and 0.58%; RR 1.41 [95% CI: 0.71 to 2.82]), any bloodstream infection (3.1% and 2.5%; RR 1.21 [95% CI: 0.86 to 1.71]), and S aureus bloodstream infection (0.37% and 0.48%; RR 0.77 [95% CI: 0.30 to 2.03]). Mupirocin use declined substantially after introduction of the protocol.

CONCLUSIONS

A strategy of targeting perioperative mupirocin treatment to carriers leads to significant reduction in mupirocin use without increasing early postoperative infectious complications in noncarriers.

Contemporary antimicrobial activity of triple antibiotic ointment: a multiphased study of recent clinical isolates in the United States and Australia

Triple antibiotic ointment (TAO) containing neomycin, polymyxin B, and bacitracin was launched in the 1950s in the United States (USA) as a prescription product and then was used over the counter (OTC) since the 1970s (USA) to prevent superficial wound infections. In Australia, TAO has been restricted to prescription use. This study 1) determined cross-resistance patterns of neomycin compared with other aminoglycosides; 2) determined the level and trend of resistance to TAO and individual components especially versus mupirocin-resistant strains (USA); and 3) established the baseline TAO activity level against pathogens from Australia. A total of 200 strains (> or =50% gentamicin-resistant) from the United States were used for the cross-resistance study including Staphylococcus aureus (110), coagulase-negative staphylococci (CoNS; 50), Pseudomonas aeruginosa (10), Escherichia coli (20), and other Enterobacteriaceae (10) tested against TAO, bacitracin, polymyxin B, neomycin, amikacin, gentamicin, streptomycin, tobramycin, and mupirocin. Fifty gentamicin-resistant isolates from each year (1997-2002) were used to determine the activity of TAO over time. Baseline resistance rates of TAO among 300 Australian isolates (AGARS Program, 2002-2003) were also studied. Reference broth microdilution methods were used in all phases of this study. At a 1:100 dilution of the ointment concentration, TAO inhibited all CoNS, Pseudomonas aeruginosa, and Enterobacteriaceae isolates, and resistance to TAO among Staphylococcus aureus at this concentration was only 5% in the cross-resistance study. Patterns of susceptibility in the United States did not significantly vary from 1997 to 2002. Australian pathogens showed that TAO was 98% active against methicillin-resistant Staphylococcus aureus and 100% for Enterobacteriaceae, methicillin-susceptible S. aureus, CoNS, and P. aeruginosa, the rates equivalent to those observed in the United States. Mupirocin-resistant S. aureus (5%) and CoNS (47%) were all TAO-susceptible. All Gram-negative species were also mupirocin-resistant, but inhibited by neomycin and/or polymyxin B components of TAO. In conclusion, aminoglycoside resistance patterns differ significantly, and none of the commonly tested agents could accurately predict neomycin resistance. TAO resistance was rare in the United States after extensive OTC use and was not adversely influenced by decades of parenteral aminoglycoside use. Australian surveillance showed high levels of TAO susceptibility in sampled isolates as a baseline for possible OTC availability. TAO maintains a wider spectrum of activity compared with mupirocin and was usable against mupirocin-resistant Gram-positive strains.