Mupirocin resistance in patients colonized with methicillin-resistant Staphylococcus aureus in a surgical intensive care unit

The efficacy of an alcohol-based nasal antiseptic versus mupirocin or iodophor for preventing surgical site infections: A meta-analysis

BACKGROUND

Nasal decolonization of Staphylococcus aureus is a proven strategy to reduce surgical site infections (SSI). Recently updated guidelines expanded nasal decolonization beyond traditionally high-risk populations to include the option for alcohol-based antiseptics (ABAs). We assessed the efficacy of a novel ABA for reducing SSI compared to mupirocin and iodophor.

METHODS

A literature search in Google Scholar, PubMed, MEDLINE, and Cochrane databases was completed of studies reporting SSI outcomes in hospitals using an ABA. Primary meta-analyses were conducted to analyze ABA clinical efficacy versus no intervention (7 studies); subanalyses compared the ABA to mupirocin (3 studies) or iodophor (2 studies).

RESULTS

One hundred forty-seven nasal decolonization titles for SSI prevention were identified, of which 7 were accepted. In the studies selected, 16,212 patients were included: 7,983 (49.24%) control group, and 8,129 (50.14%) intervention group. Significant effect sizes (measured as odds ratios [ORs]) and z-scores were found in all 3 meta-analyses: (OR = 3.178, z = 4.743, P < .001) in ABA clinical efficacy, (OR = 4.110, z = 3.167, P < .01) in ABA versus mupirocin, and (OR = 3.043, z = 3.155, P < .01) in ABA versus iodophor. Funnel plots for each demonstrated a lack of bias.

CONCLUSIONS

Statistically significant positive effects were identified in all 3 meta-analyses. An ABA appears to be a viable alternative to mupirocin or iodophors to reduce SSIs.

Chronicity of high and low level mupirocin resistance in Staphylococcus aureus from 30 Indian hospitals

Mupirocin is one of the most effective topically used antibiotic for the treatment of dermatitis, nasal carriage, decolonization of methicillin susceptible Staphylococcus aureus and eradication of methicillin resistant Staphylococcus aureus. Extensive use of this antibiotic has resulted in mupirocin resistance in Staphylococcus aureus which is a matter of concern. This study was conducted to evaluate the high and low level of mupirocin resistance in Staphylococcus aureus collected from various Indian hospitals. A total of 600 samples, of which 436 were pus specimens and 164 wound site swabs were collected from 30 Indian hospitals. Disc diffusion and agar dilution methods were used to test mupirocin susceptibility in methicillin resistant Staphylococcus aureus. Out of 600 Staphylococcus aureus isolates, 176 isolates (29.33%) were found to be methicillin resistant Staphylococcus aureus (MRSA). Out of 176 non-duplicate MRSA strains, 138 isolates were found to be mupirocin sensitive, 21 isolates had high level resistance whereas 17 isolates had low level resistance to mupirocin, which contributed 78.41%, 11.93% and 9.66% respectively. Multidrug resistant susceptibility was tested for all the MRSA with Cefuroxime, Cotrimoxazole and Vancomycin antibiotics. All the high and low level resistant strain were subjected to genome screening for mupA ileS gene respectively. mupA gene was found positive in all the high level resistant strain and out of 17 low level resistant strain, 16 strain were found point mutation in V588F of ileS gene. Overall, high rate of mupirocin resistance was found in the studied samples which might be a result of indiscriminate use of mupirocin in the population of studied region. This data emphasizes the urgent need for formulation of a well-defined and regulated guidelines for mupirocin use. Moreover, continuous surveillance is needed for the use of mupirocin and routine test should be performed to detect MRSA in patients and health care personnel to prevent MRSA infections.

Spa Typing of Staphylococcus aureus in a Neonatal Intensive Care Unit During Routine Surveillance

BACKGROUND

Staphylococcus aureus protein A (spa) typing can be used to expand characterization of the epidemiology of methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) in neonatal intensive care units (NICU).

METHODS

From January 2017 to June 2018, twice-monthly surveillance for S. aureus was performed in an academically affiliated NICU. Decolonization of infants colonized with S. aureus included chlorhexidine gluconate bathing and/or mupirocin for those with mupirocin-susceptible strains. Spa typing and mupirocin-resistance testing were performed. Demographic and clinical characteristics were compared between infants colonized with MSSA vs MRSA and infants with and without the most common MSSA spa type, MSSA-t279.

RESULTS

Overall, 14% and 2% of 1556 hospitalized infants had positive surveillance cultures for MSSA and MRSA, respectively. Thirty-six infants harbored unique MSSA spa types, 5 infants harbored unique MRSA spa types, and 30 MSSA and 6 MRSA spa types were identified in ≥2 infants. No outbreaks were identified during the study period. MSSA-t279 was isolated from 3% of infants and largely detected from infants hospitalized in one section of the NICU; 96% of t279 isolates were mupirocin resistant. Infection rates, length of hospitalization, and mortality were similar among infants initially colonized with t279 vs other MSSA spa types.

CONCLUSIONS

The MSSA colonization burden was 5-fold larger than that of MRSA. Numerous unique spa types were identified. The most common spa type, MSSA-t279, was not associated with increased morbidity or mortality but was mupirocin resistant and associated with clustered NICU beds. This suggests potential transmission from the environment, shared staff, and/or workflow issues requiring further study. Other decolonization strategies for S. aureus in the NICU are needed.

Decolonization of Staphylococcus aureus

Staphylococcus aureus infections are associated with increased morbidity, mortality, hospital stay, and health care costs. S aureus colonization has been shown to increase risk for invasive and noninvasive infections. Decolonization of S aureus has been evaluated in multiple patient settings as a possible strategy to decrease the risk of S aureus transmission and infection. In this article, we review the recent literature on S aureus decolonization in surgical patients, patients with recurrent skin and soft tissue infections, critically ill patients, hospitalized non-critically ill patients, dialysis patients, and nursing home residents to inform clinical practice.

Characteristics of methicillin-resistant Staphylococcus aureus carrying the toxic shock syndrome toxin gene: high prevalence of clonal complex 22 strains and the emergence of new spa types t223 and t605 in Iran

Methicillin-resistant Staphylococcus aureus (MRSA) strains that carry the tst gene are disseminated worldwide with varying regional incidences and different genetic backgrounds. The data on molecular characteristics of these strains is insufficient in Iran. The present study aimed to assess the characteristics and distribution of spa types of tst-positive MRSA strains. We investigated 89 MRSA isolates carrying the tst gene with spa typing, resistance gene detection and in vitro antimicrobial susceptibility. Of the 89 tested isolates, 61 (68.5%) were confirmed as multidrug resistant (MDR). The isolates were distributed across seven clonal complexes (CCs) including CC22 (42.7%), CC8 (28.1%), CC5 (11.2%), CC59 (5.6%), CC30 (4.5%), CC80 (4.5%) and CC15 (3.4%). spa typing identified 11 distinct types, with t223 (16.9%) and t790 (15.7%) being the most prevalent. All high-level mupirocin-resistant strains belonged to t002 (n = 8) and low-level mupirocin-resistant strains belonged to t790 (n = 6) spa types. Fusidic-acid-resistant isolates belonged to t437 (n = 3). iMLS_B phenotype was observed in t005 (6.7%), t002 (5.6%), t790 (3.4%), and t030, t044 and t084 (each 2.2%). It was found that in the tst-carrying MRSA strains, there were genetic diversities with a majority of the t223 spa type. Indeed, there is a necessity for more constructive surveillance/infection control strategies to address the prevalence and prevention of the emerging spa types.

Essential oils as topical anti-infective agents: A systematic review and meta-analysis

OBJECTIVE

This study summarized evidence on the efficacy and safety of essential oils (EOs) in the treatment of topical infections.

DESIGN AND SETTING

Systematic review of clinical trials conducted and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guideline. Electronic databases of the Cochrane, PubMed, EMBASE, Web of Science, and Scopus were searched from inception to November 2018.

INTERVENTION

Essential oil of any type, standard treatment and placebo.

MAIN OUTCOME MEASURES

Outcomes of the study include total acne count, acne severity index, reduction in total acne surface area, number of non-inflammatory acne lesions and inflammatory acne lesions, microbial cure rate, microbial decolonization rate, and new microbial emergence.

RESULTS

Non-significant but higher proportion of MRSA was cleared in EOs group (69% [95%CI: 34%, 96%]) compared to routine care (45% [95%CI: 36%, 53%]). Essential oils significantly lowered level of new MRSA emergence (9% [95% CI: 5%, 14%], I² = 86.59%) compared to routine care (53% [95%CI: 30%, 75%], I² = 86.59%). Four of the five studies on acne treatment showed equal or superior efficacy of EOs and the remaining one showed inferior efficacy to a control. In treatment of topical fungal infections, efficacy of essential oils were non-inferior compared to a standard treatment but superior to a placebo.

CONCLUSION

Essential oils could be considered as alternative treatment for acne, decolonization of MRSA, and topical fungal infections, yet the low quality and heterogeneity among the studies calls for further studies.

A two-part phase 1 study to establish and compare the safety and local tolerability of two nasal formulations of XF-73 for decolonisation of Staphylococcus aureus: A previously investigated 0.5mg/g viscosified gel formulation versus a modified formulation

OBJECTIVES

Successful decolonisation of nasal Staphylococcus aureus (SA) carriage by mupirocin is limited by increasing drug resistance. This randomised, open-label, phase 1 study compared the safety and local tolerability of two nasal formulations of XF-73, a novel porphyrinic antibacterial with rapid intrinsic activity against SA.

METHODS

The study was performed in 60 healthy adults. In Part 1, eight non-SA carriers were randomised to groups of four subjects each and were treated with XF-73 concentrations of 0.5mg/g 2% gel or 2.0mg/g 2% gel. In Part 2, 52 persistent SA carriers were randomised to groups of 13 subjects each and were treated with XF-73 concentrations of 0.5mg/g 2% gel, 2.0mg/g 2% gel, 0.5mg/g 4% gel or 4% viscosified placebo gel. Plasma pharmacokinetic and pharmacodynamic studies were performed. Antistaphylococcal activity was assessed as the presence/absence of SA and by quantification of colonisation using a semiquantitative scale (SA score).

RESULTS

56 subjects (8/8 from Part 1 and 48/52 from Part 2) completed the study, with 47/60 comprising the pharmacokinetic population and 48/60 the pharmacodynamic population. There was no measurable systemic absorption of XF-73. XF-73 treatment was associated with rapid reduction in SA score in all subjects. The most common treatment-emergent adverse events (TEAEs) were rhinorrhoea and nasal dryness (15.5% each in Parts 1 and 2). TEAEs were mild and resolved spontaneously.

CONCLUSION

XF-73 was well tolerated with minimal side effects at doses of 0.5mg/g 2% gel and 2.0mg/g 2% gel. These findings support further development of XF-73.

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.

Genetic Diversity Analysis of Mupirocin-Resistant Staphylococcus aureus Clinical Isolates in Tehran Hospitals, Iran

Few studies describe the molecular characterization of mupirocin resistance in Staphylococcus aureus strains. In this study, we evaluated the characteristics of mupirocin resistance in S. aureus isolates for 1-year period in Tehran, Iran. In a cross-sectional study, we collected 51 unique mupirocin-resistant strains obtained from 648 S. aureus isolates. High- and low-level resistance were determined by minimum inhibitory concentration with broth microdilution method. Presence of the genes for resistance to antibiotics and toxins was detected by polymerase chain reaction assays. Genotyping was performed by S. aureus protein A (spa) and staphylococcal cassette chromosome mec (SCCmec) typing, whereas clones were determined by multilocus sequence typing. Among mupirocin-resistant isolates, methicillin-resistant S. aureus (MRSA) 23 (45.1%) and 28 (54.9%) isolates were classified as high- and low-level mupirocin resistance, respectively. Among the 51 tested strains 25 (49%) isolates were positive for mupA genes. Seven different clones were detected in this study. High-level mupirocin-resistant (HLMUPR) strains belonged to ST8-SCCmec IV/t064 (n = 10, 19.6%), ST5-SCCmec IV/t002 (n = 5, 9.8%), ST8-SCCmec IV/t008 (n = 4, 7.8%), and ST239-SCCmec III/t631 (n = 4, 7.8%) clones, while low-level mupirocin-resistant (LLMUPR) strains belonged to ST22-SCCmec IV/t790 (n = 11, 21.6%), ST239-SCCmec III/t860 (n = 9, 17.7%), and ST15-SCCmec IV/t084 (n = 8, 15.7%) clones. Two strains belonged to ST22-SCCmec IV/t790 clone, despite carrying mupA gene, and demonstrated LLMUPR phenotype. One ST8-SCCmecIV/t008 strain with HLMUPR was confirmed as Vancomycin-intermediate S. aureus strain. Our data demonstrated the need for thorough epidemiological monitoring and a routine mupirocin testing program to prevent and detect mupirocin resistance in MRSA.

A review on mechanism of action, resistance, synergism, and clinical implications of mupirocin against Staphylococcus aureus

Mupirocin (MUP), bactroban, or pseudomonic acid is a natural crotonic acid derivative drug extracted from Pseudomonas fluorescens which is produced by modular polyketide synthases. This antibiotic has a unique chemical structure and mechanism of action. It is a mixture of A-D pseudomonic acids and inhibits protein synthesis through binding to bacterial isoleucyl-tRNA synthetase. MUP is often prescribed to prevent skin and soft tissue infections caused by S. aureus isolates and where the MRSA isolates are epidemic, MUP may be used as a choice drug for nasal decolonization. It is also used for prevention of recurring infections and control the outbreaks. The emergence of MUP resistance has been increasing particularly among methicillin-resistant Staphylococcus aureus (MRSA) isolates in many parts of the world and such resistance is often related with MUP widespread uses. Although both low-level and high-level MUP resistance were reported among MRSA isolates, the rate of resistance is different in various geographic areas. In this review, we will report the global prevalence of MUP resistance, discuss synergism and mechanism of action of MUP, and provide new insights into the clinical use of this antibiotic.

Knowledge, attitudes and practices regarding methicillin-resistant Staphylococcus aureus (MRSA) infection control and nasal MRSA carriage rate among dental health-care professionals

BACKGROUND

Dental health-care professionals (DHCPs) with nasal colonisation of methicillin-resistant Staphylococcus aureus (MRSA) can serve as a reservoir for MRSA transmission to others and be exposed to self-contamination with MRSA. Evaluating the knowledge, attitudes and actual practice of DHCPs is imperative for appropriate infection control.

METHODS

Dentists, dental hygienists and dental technologists from Seoul National University Dental Hospital were recruited to participate in a cross-sectional survey and undergo nasal sampling of MRSA. The survey included demographic questions, six questions about knowledge, eight questions about attitudes/perceptions and six questions about practices/behaviours regarding MRSA infection control. Nasal samples from the participants were analysed for MRSA presence, antimicrobial susceptibility and staphylococcal cassette chromosome mec (SCCmec) typing. MRSA carriers underwent decolonisation with topical mupirocin.

RESULTS

Among 139 DHCPs, four (2.9%) were nasal MRSA carriers. Decolonisation was successful in three participants. One participant was decolonised with topical fusidic acid after failure to decolonise with mupirocin. Dentists had a higher knowledge score compared with the other professionals (P < 0.05). Dental hygienists scored higher on practice questions compared with the other professionals (P < 0.05). There was a significant, positive correlation between attitude and practice scores (P < 0.01).

CONCLUSIONS

The nasal MRSA carriage rate among DHCPs is 2.9%, which is higher than that in the general population but lower than that in other health-care professionals. Further education of DHCPs on MRSA, especially regarding its seriousness, is needed to improve MRSA infection control in a dental hospital setting.

Povidone-Iodine-Based Solutions for Decolonization of Nasal Staphylococcus aureus: A Randomized, Prospective, Placebo-Controlled Study

BACKGROUND

Nasal Staphylococcus aureus decolonization reduces the risk of surgical site infections after orthopedic procedures. Povidone-iodine (PI)-based solutions have shown promising results in bacteria decolonization. The unique physiology of the nose may pose challenges for the bioactivity profiles of PI solutions. This study compared the antibacterial efficacy of an off-the-shelf PI product with a specifically manufactured PI-based skin and nasal antiseptic (SNA).

METHODS

This randomized, placebo-controlled study was conducted at a single institution between April 2014 and July 2015. Four hundred and twenty-nine patients undergoing primary or revision total joint arthroplasty, femoroacetabular osteoplasty, pelvic osteotomy, or total shoulder arthroplasty were included. 10% off-the-shelf PI, 5% PI-based SNA, or saline (placebo) were used for nasal decolonization. Baseline cultures were taken immediately preoperatively, followed by treatment of both nares twice for 2 minutes with 4 applicators. Reculturing of the right nostril occurred at 4 hours and the left at 24 hours.

RESULTS

Ninety-five of the 429 patients (22.1%) had a positive culture result for S. aureus; 13 (3.03%) were methicillin-resistant S. aureus. Of these 95, 29 were treated with off-the-shelf PI, 34 with SNA, and 32 with saline swabs. At 4 hours post-treatment, S. aureus culture was positive in 52% off-the-shelf PI patients, 21% SNA patients, and 59% saline patients. After 24 hours posttreatment, S. aureus culture was positive in 72% off-the-shelf PI patients, 59% SNA patients, and 69% saline group. SNA was significantly more effective at decolonizing S. aureus over the 4-hour time interval (P = .003); no significant difference was observed over the 24-hour time interval between the 3 groups.

CONCLUSION

A single application of PI-based SNA before surgery may be effective in eliminating nasal S. aureus in over two-thirds of patients. Off-the-shelf PI swabs were not as effective at 4 hours as the specifically manufactured product for S. aureus decolonization.

Dissemination of macrolides, fusidic acid and mupirocin resistance among Staphylococcus aureus clinical isolates

As an increasingly common cause of skin infections worldwide, the prevalence of antibiotic-resistant Staphylococcus aureus (S. aureus) across China has not been well documented. This literature aims to study the resistance profile to commonly used antibiotics, including macrolides, fusidic acid (FA) and mupirocin, and its relationship to the genetic typing in 34 S. aureus strains, including 6 methicillin-resistant S. aureus (MRSA), isolated from a Chinese hospital. The MIC results showed 27 (79.4%), 1 (2.9%) and 6 (17.6%) isolates were resistant to macrolides, FA and mupirocin, respectively. Among 27 macrolide-resistant S. aureus isolates, 5 (18.5%) were also resistant to mupirocin and 1 (3.7%) to FA. A total of 13 available resistant genes were analyzed in 28 antibiotic-resistant strains using polymerase chain reaction (PCR). The positive rates of macrolide-resistant ermA, ermB, ermC, erm33 and low level mupirocin-resistant ileS mutations were 11.1%, 25.9%, 51.9%, 7.4% and 100%, respectively. Other determinants for FA- and high level mupirocin-resistance were not found. The results of multilocus sequence typing (MLST) and pulsed field gel electrophoresis (PFGE) revealed 13 sequence types (STs) and 18 clusters in 23 resistant gene positive S. aureus isolates. Among these STs, ST5 was most prevalent, accounting for 18.2%. Notably, various clusters were found with similar resistance phenotype and genotype, exhibiting a weak genetic relatedness and high genetic heterogeneities. In conclusion, macrolides, especially erythromycin, are not appropriate to treat skin infections caused by S. aureus, and more effective measures are required to reduce the dissemination of macrolides, FA and mupirocin resistance of the pathogen.

Methicillin-Resistant Staphylococcus aureus Infections: A Comprehensive Review and a Plastic Surgeon's Approach to the Occult Sites

BACKGROUND

Up to 20 percent of the general population is persistently colonized with Staphylococcus aureus, and 1 to 3 percent of the population is colonized with community-acquired methicillin-resistant S. aureus. Currently, the knowledge of methicillin-resistant Staphylococcus aureus carriage sites other than the nose, and their effect on surgical site infections in cosmetic surgery, is lacking.

METHODS

A comprehensive literature review using the PubMed database to analyze prevalence, anatomical carrier sites, current screening and decontamination protocols and guidelines, and methicillin-resistant S. aureus in cosmetic surgery was performed. The senior author's (L.R.) methicillin-resistant S. aureus infection experience and prevention protocols were also reviewed.

RESULTS

Nasal swabs detect only 50.5 percent of methicillin-resistant S. aureus colonization, and broad screening has noted the presence of methicillin-resistant S. aureus in the ear canal and umbilicus. Decolonization protocols within the orthopedic and cardiothoracic surgery literature have reduced rates of methicillin-resistant S. aureus surgical-site infections. There are no decolonization guidelines for plastic surgeons. Since instituting their decolonization protocol, the authors have had no cases of methicillin-resistant S. aureus infection in nearly 1000 cosmetic surgery procedures.

CONCLUSIONS

There are very limited, if any, Level I or II data regarding methicillin-resistant S. aureus screening and decolonization. As the sequelae of a surgical-site infection can be disastrous, expert opinions recommend that plastic surgeons vigorously address methicillin-resistant S. aureus colonization and infection. The authors have developed and recommend a simple decolonization protocol that includes treatment of the umbilicus, ear canal, and nares to limit surgical-site infection and improve surgical outcomes.

MRSA decolonisation using polyhexanide 0.1 % with application where necessary of systemic antibiotics

Background: Increasing infections and drug resistances lead to new treatment concepts in terms of MRSA decolonisation. An antibiotic-free decolonisation treatment with topical antiseptics is of great clinical interest. We investigated the effectiveness of MRSA decolonisation therapy using the topical antiseptic agent polyhexanide 0.1 %. If needed, a systemic antibiotic was added in case of hospitalisation, abscess formation, chronic wounds and others.

Patients and methods: 63 patients were introduced to our outpatient clinic within a period of record of 15 months. 42 (66.7 %) of them were confirmed MRSA-positive and 27 (64.3 %) of these colonised patients were included to the protocol of decolonisation. Patients who followed the protocol of decolonisation (n=27) were investigated in terms of the site of MRSA-colonisation, parameters that minimize the effect of decolonisation, spa types as well as the effectiveness of the topical antiseptic agent polyhexanide 0.1 %.

Results: 22 patients (81.5 %) were successfully decolonised within the group that followed the decolonisation protocol (n=27). Using polyhexanide 0.1 % as single treatment regime seven people (31.8 %) were successfully decolonised, whereas 15 patients (68.2 %) were in need of an additional systemic treatment with antibiotics in order to be decolonised. The implementation of one topical eradication cycle with polyhexanide 0.1 % was effective in case of an exclusive colonisation of the nose (n=3). At maximum, three decolonisation runs were necessary. Within six months of post-eradication investigations no relapses of MRSA were registered.

Conclusions: One third of the decolonised patients were successfully treated with the topical antiseptic polyhexanide 0.1 %, whereas two thirds of the patients that followed the decolonisation protocol were in need of an additional systemic antibiotic.

Active Surveillance Cultures and Targeted Decolonization Are Associated with Reduced Methicillin-Susceptible Staphylococcus aureus Infections in VLBW Infants

BACKGROUND

Methicillin-susceptible Staphylococcus aureus (MSSA) is a major contributor to infectious episodes of very low birth weight infants (VLBWI), resulting in significant morbidity and mortality.

OBJECTIVE

To examine the efficacy and safety of surveillance cultures and the decolonization of MSSA-colonized VLBWI.

METHODS

VLBWI admitted to our neonatal wards in 2011-2016 were retrospectively analyzed. Rates of MSSA-attributable infections were compared before and after the implementation of active surveillance cultures and the decolonization of MSSA-colonized patients. The mupirocin susceptibility of isolated MSSA strains was routinely tested.

RESULTS

A total of 1,056 VLBWI were included in the study, 552 in the pre-intervention period and 504 in the post-intervention period. The implementation of surveillance cultures and decolonization of colonized patients resulted in a 50% reduction of incidence rates per 1,000 patient-days of MSSA-attributable infections (1.63 [95% CI 1.12-2.31] vs. 0.83 [95% CI 0.47-1.35], p = 0.024). No adverse effects were observed from application of the decolonization protocol with mupirocin and octenidin. No mupirocin-resistant MSSA strains were detected during the study period.

CONCLUSION

Implementation of an active surveillance and decolonization protocol resulted in a reduction of MSSA-attributable infections in VLBWI.

A randomized, double-blind, comparative study to assess the safety and efficacy of topical retapamulin ointment 1% versus oral linezolid in the treatment of secondarily infected traumatic lesions and impetigo due to methicillin-resistant Staphylococcus aureus

OBJECTIVE

To evaluate the clinical and bacteriological efficacy of topical retapamulin ointment 1% versus oral linezolid in the treatment of patients with secondarily infected traumatic lesions (SITLs; excluding abscesses) or impetigo due to methicillin-resistant Staphylococcus aureus (MRSA).

DESIGN

A randomized, double-blind, double-dummy, multicenter, comparative study (NCT00852540).

SETTING

Patients recruited from 36 study centers in the United States.

PATIENTS

Patients 2 months or older with SITL (including secondarily infected lacerations or sutured wounds) or impetigo (bullous and nonbullous) suitable for treatment with a topical antibiotic, with a total Skin Infection Rating Scale score of 8 or greater, including a pus/exudate score of 3 or greater.

INTERVENTIONS

Patients received retapamulin ointment 1% (plus oral placebo), twice daily for 5 days or oral linezolid (plus placebo ointment) 2 or 3 times daily for 10 days.

MAIN OUTCOME MEASURE

Primary end point: clinical response (success/failure) at follow-up in patients with MRSA at baseline (per-protocol population). Secondary efficacy end points: clinical and microbiologic response and outcome at follow-up and end of therapy; therapeutic response at follow-up.

MAIN RESULTS

The majority of patients had SITL (70.4% [188/267] and 66.4% [91/137] in the retapamulin and linezolid groups, respectively; intent-to-treat clinical population). Clinical success rate at follow-up was significantly lower in the retapamulin versus the linezolid group (63.9% [39/61] vs 90.6% [29/32], respectively; difference in success rate -26.7%; 95% CI, -45.7 to -7.7).

CONCLUSIONS

Clinical success rate at follow-up in the per-protocol MRSA population was significantly lower in the retapamulin versus the linezolid group. It could not be determined whether this was related to study design, bacterial virulence, or retapamulin activity.

Change in Antimicrobial Susceptibility of Skin-Colonizing Staphylococcus aureus in Korean Patients with Atopic Dermatitis during Ten-Year Period

BACKGROUND

A small subset of adolescents atopic dermatitis (AD) tends to persist. This also leads to get more antibiotics exposure with advancing years. Antibiotic resistance has been regarded as a serious problem during Staphylococcus aureus treatment, especially methicillin-resistant S. aureus (MRSA).

OBJECTIVE

It was investigated the S. aureus colonization frequency in the skin lesions and anterior nares of adolescent AD patients and evaluated the changes in S. aureus antimicrobial susceptibility for years.

METHODS

Patients who visited our clinic from September 2003 to August 2005 were classified into group A, and patients who visited from August 2010 to March 2012 were classified into group B. To investigate the differences with regard to patients' age and disease duration, the patients were subdivided into groups according to age. Lesional and nasal specimens were examined.

RESULTS

Among the 295 AD patients, the total S. aureus colonization rate in skin lesions was 66.9% (95/142) for group A and 78.4% (120/153) for group B. No significant changes in the systemic antimicrobial susceptibilities of S. aureus strains isolated from adolescent AD patients were observed during about 10-year period. The increased trend of MRSA isolation in recent adolescent AD outpatients suggest that the community including school could be the source of S. aureus antibiotic resistance and higher fusidic acid resistance rates provides evidence of imprudent topical use.

CONCLUSION

Relatively high MRSA isolation and fusidic acid resistance rates in recent AD patients suggest that the community harbors antibiotic-resistant S. aureus.

The Antistaphylococcal Activity of Citropin 1.1 and Temporin A against Planktonic Cells and Biofilms Formed by Isolates from Patients with Atopic Dermatitis: An Assessment of Their Potential to Induce Microbial Resistance Compared to Conventional Antimicrobials

Staphylococcus aureus (SA) colonizes the vast majority of patients with atopic dermatitis (AD). Its resistance to antibiotics and ability to form biofilms are the main origins of therapeutic complications. Endogenous antimicrobial peptides (AMPs) exhibit strong activity against SA, including antibiotic resistant strains as well as bacteria existing in biofilm form. The purpose of the present work was to determine the antistaphylococcal activity of two amphibian peptides against SA isolated from patients with AD. The AMPs demonstrated permanent activity towards strains exposed to sublethal concentrations of the compounds and significantly stronger antibiofilm activity in comparison to that of conventional antimicrobials. The results suggest the potential application of amphibian AMPs as promising antistaphylococcal agents for the management of skin infections.

Prevalence of qacA/B Genes and Mupirocin Resistance Among Methicillin-Resistant Staphylococcus aureus (MRSA) Isolates in the Setting of Chlorhexidine Bathing Without Mupirocin

OBJECTIVE

We aimed to determine the frequency of qacA/B chlorhexidine tolerance genes and high-level mupirocin resistance among MRSA isolates before and after the introduction of a chlorhexidine (CHG) daily bathing intervention in a surgical intensive care unit (SICU).

DESIGN

Retrospective cohort study (2005-2012) SETTING: A large tertiary-care center

PATIENTS

Patients admitted to SICU who had MRSA surveillance cultures of the anterior nares

METHODS

A random sample of banked MRSA anterior nares isolates recovered during (2005) and after (2006-2012) implementation of a daily CHG bathing protocol was examined for qacA/B genes and high-level mupirocin resistance. Staphylococcal cassette chromosome mec (SCCmec) typing was also performed.

RESULTS

Of the 504 randomly selected isolates (63 per year), 36 (7.1%) were qacA/B positive (+) and 35 (6.9%) were mupirocin resistant. Of these, 184 (36.5%) isolates were SCCmec type IV. There was a significant trend for increasing qacA/B (P=.02; highest prevalence, 16.9% in 2009 and 2010) and SCCmec type IV (P<.001; highest prevalence, 52.4% in 2012) during the study period. qacA/B(+) MRSA isolates were more likely to be mupirocin resistant (9 of 36 [25%] qacA/B(+) vs 26 of 468 [5.6%] qacA/B(-); P=.003).

CONCLUSIONS

A long-term, daily CHG bathing protocol was associated with a change in the frequency of qacA/B genes in MRSA isolates recovered from the anterior nares over an 8-year period. This change in the frequency of qacA/B genes is most likely due to patients in those years being exposed in prior admissions. Future studies need to further evaluate the implications of universal CHG daily bathing on MRSA qacA/B genes among hospitalized patients.

Active Surveillance Cultures and Decolonization to Reduce Staphylococcus aureus Infections in the Neonatal Intensive Care Unit

BACKGROUND

Staphylococcus aureus is a common cause of healthcare-associated infections in neonates.

OBJECTIVE

To examine the impact of methicillin-susceptible S. aureus (MSSA) decolonization on the incidence of MSSA infection and to measure the prevalence of mupirocin resistance.

METHODS

We retrospectively identified neonates admitted to a tertiary care neonatal intensive care unit (NICU) from April 1, 2011, through September 30, 2014. We compared rates of MSSA-positive cultures and infections before and after implementation of an active surveillance culture and decolonization intervention for MSSA-colonized neonates. We used 2 measurements to identify the primary outcome, NICU-attributable MSSA: (1) any culture sent during routine clinical care that grew MSSA and (2) any culture that grew MSSA and met criteria of the National Healthcare Safety Network's healthcare-associated infection surveillance definitions. S. aureus isolates were tested for mupirocin susceptibility. We estimated incidence rate ratios using interrupted time-series models.

RESULTS

Before and after the intervention, 1,523 neonates (29,220 patient-days) and 1,195 neonates (22,045 patient-days) were admitted to the NICU, respectively. There was an immediate reduction in the mean quarterly incidence rate of NICU-attributable MSSA-positive clinical cultures of 64% (incidence rate ratio, 0.36 [95% CI, 0.19-0.70]) after implementation of the intervention, and MSSA-positive culture rates continued to decrease by 21% per quarter (incidence rate ratio, 0.79 [95% CI, 0.74-0.84]). MSSA infections also decreased by 73% immediately following the intervention implementation (incidence rate ratio, 0.27 [95% CI, 0.10-0.79]). No mupirocin resistance was detected.

CONCLUSION

Active surveillance cultures and decolonization may be effective in decreasing S. aureus infections in NICUs.

Clonal variation in high- and low-level phenotypic and genotypic mupirocin resistance of MRSA isolates in south-east London

OBJECTIVES

Both low-level mupirocin resistance (LMR) and high-level mupirocin resistance (HMR) have been identified. The aim of this study was to determine the epidemiology of LMR and HMR in MRSA isolates at five hospitals that have used mupirocin for targeted decolonization as part of successful institutional control programmes.

METHODS

All MRSA identified in three microbiology laboratories serving five central and south-east London hospitals and surrounding communities between November 2011 and February 2012 were included. HMR and LMR were determined by disc diffusion testing. WGS was used to derive multilocus sequence types (MLSTs) and the presence of HMR and LMR resistance determinants.

RESULTS

Prevalence of either HMR or LMR amongst first healthcare episode isolates from 795 identified patients was 9.69% (95% CI 7.72-11.96); LMR was 6.29% (95% CI 4.70-8.21) and HMR was 3.40% (95% CI 2.25-4.90). Mupirocin resistance was not significantly different in isolates identified from inpatients at each microbiology laboratory, but was more common in genotypically defined 'hospital' rather than 'community' isolates (OR 3.17, 95% CI 1.36-9.30, P = 0.002). LMR was associated with inpatient stay, previous history of MRSA and age ≥65 years; HMR was associated with age ≥65 years and residential postcode outside London. LMR and HMR varied by clone, with both being low in the dominant UK MRSA clone ST22 compared with ST8, ST36 and ST239/241 for LMR and with ST8 and ST36 for HMR. V588F mutation and mupA carriage had high specificity (>97%) and area under the curve (>83%) to discriminate phenotypic mupirocin resistance, but uncertainty around the sensitivity point estimate was large (95% CI 52.50%-94.44%). Mutations in or near the mupA gene were found in eight isolates that carried mupA but were not HMR.

CONCLUSIONS

Mupirocin resistance was identified in <10% of patients and varied significantly by clone, implying that changes in clonal epidemiology may have an important role in determining the prevalence of resistance in conjunction with selection due to mupirocin use.

Comprehensive review of methicillin-resistant Staphylococcus aureus: screening and preventive recommendations for plastic surgeons and other surgical health care providers

BACKGROUND

Up to 2.3 million people are colonized with methicillin-resistant Staphylococcus aureus in the United States, causing well-documented morbidity and mortality. Although the association of clinical outcomes with community and hospital carriage rates is increasingly defined, less is reported about asymptomatic colonization prevalence among physicians, and specifically plastic surgeons and the subsequent association with the incidence of patient surgical-site infection.

METHODS

A review of the literature using the PubMed and Cochrane databases analyzing provider screening, transmission, and prevalence was undertaken. In addition, a search was completed for current screening and decontamination guidelines and outcomes.

RESULTS

The methicillin-resistant S. aureus carriage prevalence of surgical staff is 4.5 percent. No prospective data exist regarding transmission and interventions for plastic surgeons. No studies were found specifically looking at prevalence or treatment of plastic surgeons. Current recommendations by national organizations focus on patient-oriented point-of-care testing and intervention, largely ignoring the role of the health care provider. Excellent guidelines exist regarding screening, transmission prevention, and treatment both in the workplace and in the community. No current such guidelines exist for plastic surgeons.

CONCLUSIONS

No Level I or II evidence was found regarding physician screening, treatment, or transmission. Current expert opinion, however, indicates that plastic surgeons and their staff should be vigilant for methicillin-resistant S. aureus transmission, and once a sentinel cluster of skin and soft-tissue infections is identified, systematic screening and decontamination should be considered. If positive, topical decolonization therapy should be offered. In refractory cases, oral antibiotic therapy may be required, but this should not be used as a first-line strategy.

Efficacy of skin and nasal povidone-iodine preparation against mupirocin-resistant methicillin-resistant Staphylococcus aureus and S. aureus within the anterior nares

Mupirocin decolonization of nasal Staphylococcus aureus prior to surgery decreases surgical-site infections; however, treatment requires 5 days, compliance is low, and resistance occurs. In 2010, 3M Company introduced povidone-iodine (PVP-I)-based skin and nasal antiseptic (Skin and Nasal Prep [SNP]). SNP has rapid, broad-spectrum antimicrobial activity. We tested SNP's efficacy using full-thickness tissue (porcine mucosal [PM] and human skin) explant models and human subjects. Prior to or following infection with methicillin-resistant Staphylococcus aureus (MRSA) (mupirocin sensitive and resistant), explants were treated with Betadine ophthalmic preparation (Bet), SNP, or mupirocin (Bactroban nasal ointment [BN]) or left untreated. One hour posttreatment, explants were washed with phosphate-buffered saline (PBS) plus 2% mucin. One, 6, or 12 h later, bacteria were recovered and enumerated. Alternatively, following baseline sampling, human subjects applied two consecutive applications of SNP or saline to their anterior nares. One, 6, and 12 h after application of the preparation (postprep), nasal swabs were obtained, and S. aureus was enumerated. We observed that treatment of infected PM or human skin explants with SNP resulted in >2.0 log10 CFU reduction in MRSA, regardless of mupirocin sensitivity, which was significantly different from the values for BN- and Bet-treated explants and untreated controls 1 h, 6 h, and 12 h after being washed with PBS plus mucin. Swabbing the anterior nares of human subjects with SNP significantly reduced resident S. aureus compared to saline 1, 6, and 12 h postprep. Finally, pretreatment of PM explants with SNP, followed by a mucin rinse prior to infection, completely prevented MRSA infection. We conclude that SNP may be an attractive alternative for reducing the bioburden of anterior nares prior to surgery.

Decolonization to prevent Staphylococcus aureus transmission and infections in the neonatal intensive care unit

Staphylococcus aureus (S. aureus) continues to be a leading cause of outbreaks and health-care-associated infections in neonatal intensive care units. In the first few months of life, many neonates acquire S. aureus as part of their delicate and evolving microbiota. Neonates that asymptomatically acquire S. aureus colonization are at increased risk of developing a subsequent S. aureus infection. This review discusses the epidemiology and prevention of S. aureus disease in neonates and how decolonization to eradicate S. aureus may decrease S. aureus transmission and infections in the neonatal intensive care unit.

LTX-109 is a novel agent for nasal decolonization of methicillin-resistant and -sensitive Staphylococcus aureus

Nasal decolonization has a proven effect on the prevention of severe Staphylococcus aureus infections and the control of methicillin-resistant S. aureus (MRSA). However, rising rates of resistance to antibiotics highlight the need for new substances for nasal decolonization. LTX-109 is a broad-spectrum, fast-acting bactericidal antimicrobial drug for topical treatment, which causes membrane disruption and cell lysis. This mechanism of action is not associated with cross-resistance and has a low propensity for development of resistance. In the present study, persistent nasal MRSA and methicillin-sensitive S. aureus (MSSA) carriers were treated for 3 days with vehicle or with 1%, 2%, or 5% LTX-109. A significant effect on nasal decolonization was observed already after 2 days of LTX-109 treatment in subjects treated with 2% or 5% LTX-109 compared to vehicle (P ≤ 0.0012 by Dunnett's test). No safety issues were noted during the 9-week follow-up period. Minimal reversible epithelial lesions were observed in the nasal cavity. The systemic exposure was very low, with a maximum concentration of drug in plasma (Cmax) at 1 to 2 h postdosing (3.72 to 11.7 ng/ml). One week after treatment initiation, LTX-109 was not detectable in any subject. Intranasal treatment of S. aureus with LTX-109 is safe and reduces the bacterial load already after a single day of treatment. Hence, LTX-109 has potential as a new and effective antimicrobial agent with a low propensity of resistance development that can prevent infections by MSSA/MRSA during hospitalization. (This study has been registered at ClinicalTrials.gov under registration no. NCT01158235.).

Bacteriophage as effective decolonising agent for elimination of MRSA from anterior nares of BALB/c mice

BACKGROUND

Nasal carriers not only pose serious threat to themselves but also to the community by playing an active role in the dissemination of serious and life threatening S. aureus especially MRSA strains. The present study focuses on the use of broad spectrum lytic phage as decolonising agent. In addition, the combined use of lytic phage with mupirocin has also been investigated as an effective decolonising regimen. The effect of phage on the adherence, invasion and cytotoxic effect of MRSA strains on nasal epithelial cells was studied in an ex-vivo model of cultured murine nasal epithelial cells. This was followed by demonstration of therapeutic potential of phage along with mupirocin in decolonising the nares of BALB/c mice using a nasal model of MRSA colonisation.

RESULTS

Phage was able to significantly reduce the in vitro adherence, invasion and cytotoxicity of MRSA 43300 as well as other clinical MRSA strains on murine nasal epithelial cells as compared to untreated control. Also, the frequency of emergence of spontaneous mutants decreased to negligible levels when both the agents (phage and mupirocin) were used together.

CONCLUSION

Phage MR-10, given along with mupirocin showed an additive effect and the combination was able to effectively eradicate the colonising MRSA population from the nares of mice by day 5.

Risk factors for development of methicillin-resistant Staphylococcus aureus-positive clinical culture in nasal carriers after decolonization treatment

BACKGROUND

Active surveillance systems are effective in reducing health care-associated infections caused by methicillin-resistant Staphylococcus aureus (MRSA). Nonetheless, some patients develop MRSA infection despite control measures. We tried to identify risk factors related to the appearance of MRSA at sites other than the nasal fossa in patients who were nasal carriers of MRSA.

METHODS

A retrospective case-control study was conducted in an active surveillance program for MRSA between January 2009 and December 2010 at a Spanish teaching hospital. Cases were patients with MRSA in the anterior nares and a length of stay of at least 5 days who developed MRSA-positive clinical culture after decolonization treatment had started. Controls were patients with the same characteristics as the case group, except that they did not develop MRSA-positive clinical culture as verified by negative clinical cultures.

RESULTS

After intrinsic and extrinsic risk factors were analyzed, the emergence of mupirocin-resistant MRSA clones after decolonization treatment, and residence in a nursing home were marginally significant in the univariate analysis. The detection of the emergence of mupirocin-resistant MRSA clones was independently associated with the detection of MRSA in other clinical locations.

CONCLUSIONS

In an active surveillance program for MRSA it is important to determine the mupirocin susceptibility of the isolates to determine appropriate treatment and to verify negativity after decolonizing treatment has been completed.

Susceptibility of Staphylococcus aureus to topical agents in the United States: a sentinel study

BACKGROUND

Mupirocin has been used topically for treating skin and skin structure infections and for nasal decolonization before surgical interventions. Pleuromutilin compounds, including retapamulin, provide similar treatment/interventional options. Rates of resistance of Staphylococcus aureus to mupirocin and other agents used to treat skin and skin structure infections vary between countries and medical centers, including those in the United States. These resistance rates may be associated with higher usage and/or improper epidemiologic practices.

OBJECTIVE

This study aimed to determine rates of resistance to topical and other class agents against S aureus isolates collected from SSSIs.

METHODS

Isolates were obtained from outpatients at 6 US dermatology centers in 5 states. Demographic data were collected from medical records, and each patient completed a study questionnaire on recent history of skin infections, antibiotic use, and hospitalization. Each isolate was tested against cephalothin, clindamycin, erythromycin, gentamicin, mupirocin, tetracycline, retapamulin, and trimethoprim/sulfamethoxazole.

RESULTS

Although methicillin-resistance rates varied between centers (range, 15.8%-35.5%), macrolide resistance was ~50% at all of the sites in this study. Mupirocin-resistant isolates were observed much more frequently from 1 center (33.9%), and nearly all demonstrated high-level resistance. Only 1 retapamulin-resistant isolate (0.5%) was observed, with a minimum inhibitory concentration of 16 µg/mL. The other agents had relatively low resistance rates, which varied between centers and were dependent on susceptibility to methicillin.

CONCLUSIONS

Although the rate of mupirocin-resistant S aureus isolates collected in this investigation was >10%, retapamulin resistance was infrequent. Surveillance of topical agents to determine resistance rates against targeted bacteria is necessary.

The prevalence and significance of methicillin-resistant Staphylococcus aureus colonization at admission in the general ICU Setting: a meta-analysis of published studies

OBJECTIVE

To estimate the prevalence and significance of nasal methicillin-resistant Staphylococcus aureus colonization in the ICU and its predictive value for development of methicillin-resistant S. aureus infection.

DATA SOURCES

MEDLINE and EMBASE and reference lists of all eligible articles.

STUDY SELECTION

Studies providing raw data on nasal methicillin-resistant S. aureus colonization at ICU admission, published up to February 2013. Analyses were restricted in the general ICU setting. Medical, surgical, and interdisciplinary ICUs were eligible. ICU studies referring solely on highly specialized ICUs populations and reports on methicillin-resistant S. aureus outbreaks were excluded.

DATA EXTRACTION

Two authors independently assessed study eligibility and extrapolated data in a blinded fashion. The two outcomes of interest were the prevalence estimate of methicillin-resistant S. aureus nasal colonization at admission in the ICU and the sensitivity/specificity of colonization in predicting methicillin-resistant S. aureus-associated infections.

DATA SYNTHESIS

Meta-analysis, using a random-effect model, and meta-regression were performed. Pooled data extracted from 63,740 evaluable ICU patients provided an estimated prevalence of methicillin-resistant S. aureus nasal colonization at admission of 7.0% (95% CI, 5.8-8.3). Prevalence was higher for North American studies (8.9%; 95% CI, 7.1-10.7) and for patients screened using polymerase chain reaction (14.0%; 95% CI, 9.6-19). A significant per year increase in methicillin-resistant S. aureus colonization was also noted. In 17,738 evaluable patients, methicillin-resistant S. aureus infections (4.1%; 95% CI, 2.0-6.8) developed in 589 patients. The relative risk for colonized patients was 8.33 (95% CI, 3.61-19.20). Methicillin-resistant S. aureus nasal carriage had a high specificity (0.96; 95% CI, 0.90-0.98) but low sensitivity (0.32; 95% CI, 0.20-0.48) to predict methicillin-resistant S. aureus-associated infections, with corresponding positive and negative predictive values at 0.25 (95% CI, 0.11-0.39) and 0.97 (95% CI, 0.83-1.00), respectively.

CONCLUSIONS

Among ICU patients, 5.8-8.3% of patients are colonized by methicillin-resistant S. aureus at admission, with a significant upward trend. Methicillin-resistant S. aureus colonization is associated with a more than eight-fold increase in the risk of associated infections during ICU stay, and methicillin-resistant S. aureus infection develops in one fourth of patients who are colonized with methicillin-resistant S. aureus at admission to the ICU.

The emergence of linezolid resistance among Enterococci in intestinal microbiota of treated patients is unrelated to individual pharmacokinetic characteristics

Linezolid is an antimicrobial agent for the treatment of multiresistant Gram-positive infections. We assessed the impact of linezolid on the microbiota and the emergence of resistance and investigated its relationship with plasma pharmacokinetics of the antibiotic. Twenty-eight patients were treated for the first time with linezolid administered orally (n = 17) or parenterally (n = 11) at 600 mg twice a day. Linezolid plasma pharmacokinetic analysis was performed on day 7. Colonization by fecal enterococci, pharyngeal streptococci, and nasal staphylococci were assessed using selective media with or without supplemental linezolid. The resistance to linezolid was characterized. The treatment led to a decrease of enterococci, staphylococci, and streptococci in the fecal (P = 0.03), nasal, and pharyngeal (P < 0.01) microbiotas. The appearance of resistant strains was observed only in enterococci from the fecal microbiota between the 7th and 21st days of treatment in four patients (14.3%). The resistance was mainly due for the first time to the mutation G2447T in the 23S rRNA gene. No pharmacokinetic parameters were significantly different between the patients, regardless of the appearance of resistance. The emergence of linezolid resistance during treatment was observed only in the intestinal microbiota and unrelated to pharmacokinetic parameters. However, colonization by Gram-positive bacteria was reduced as a result of treatment in all microbiotas.

Mupirocin susceptibility in Staphylococcus aureus nasal and oropharyngeal isolates from Brazilian children

Mupirocin is a topical antimicrobial agent and part of most Staphylococcus aureus decolonization regimens. Thus, knowing the mupirocin susceptibility profile of colonizing S. aureus is paramount for the proper use of this agent. We evaluated S. aureus isolates from 128 colonized children, using disc diffusion (with 5 mcg and 200 mcg discs) and Etest. None were low-level or high-level mupirocin-resistant. Since mupirocin will be increasingly needed for the control of S. aureus infection, continuous monitoring of its susceptibility status is necessary.

Activities of vancomycin, ceftaroline, and mupirocin against Staphylococcus aureus isolates collected in a 2011 national surveillance study in the United States

Forty-two medical centers from throughout the United States participating in a longitudinal surveillance program were asked to submit 100 consecutive Staphylococcus aureus isolates during July to December 2011. Susceptibility testing using CLSI broth microdilution and mecA detection by PCR analysis was performed on the 4,131 isolates collected. Methods employing Etest glycopeptide resistance detection (GRD; bioMérieux) and brain heart infusion agar containing 4 μg/ml vancomycin (BHIV) were used to screen methicillin-resistant S. aureus (MRSA) isolates for heterogeneous intermediate-level resistance to vancomycin (hVISA). Isolates with positive hVISA screen results were confirmed by population analysis profiling-area under the curve (PAP-AUC) determinations. The genetic relatedness of hVISA, ceftaroline-nonsusceptible, or high-level (HL) mupirocin resistance MRSA isolates was assessed by pulsed-field gel electrophoresis (PFGE). Among 2,093 MRSA isolates, the hVISA screen results were positive with 47 isolates by Etest GRD and 30 isolates by BHIV agar screen. Twenty-five of the GRD- or BHIV screen-positive isolates were confirmed as hVISA by PAP-AUC testing. Results of the current study were compared to results obtained from prior surveillance performed in 2009. The prevalence of hVISA among MRSA isolates was higher in 2011 than in 2009 (1.2% versus 0.4%, P = 0.003), especially for isolates with a vancomycin MIC of 2 (45.4% versus 14.3%, P = 0.01). The overall rate of ceftaroline susceptibility in the current study was 99.4% (one hVISA isolate had an intermediate ceftaroline MIC). HL mupirocin resistance increased from 2.2% in 2009 to 3.2% in 2011 (P = 0.006). Although overall rates of hVISA and HL mupirocin resistance are low, they have increased since 2009.

In-vitro activity of polyhexanide alone and in combination with antibiotics against Staphylococcus aureus

BACKGROUND

The resistance of Staphylococcus aureus is increasing, not only to antibiotics but also to antiseptics.

AIM

To investigate the activity of the antiseptic polyhexanide and several antibiotics against clinical isolates of meticillin-susceptible and meticillin-resistant Staphylococcus aureus (MSSA and MRSA, respectively). Polyhexanide was tested alone and in combination with oxacillin, penicillin G, ampicillin, cefazolin, cefuroxime, imipenem, gentamicin, erythromycin, doxycycline, levoflocaxin, linezolid and vancomycin.

METHODS

Fifty MSSA and 50 MRSA strains, including one vancomycin-intermediate (VISA) strain, were tested. All strains were typed by pulsed-field gel electrophoresis (PFGE) to exclude testing of clonal isolates. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined using the serial broth microdilution technique according to DIN 58940. Combinations of polyhexanide and different antibiotics were investigated using the checkerboard technique.

FINDINGS

Polyhexanide MICs and MBCs in the range of 0.5-2mg/L were found for both MSSA and MRSA, and the VISA strain had MIC and MBC values of 2mg/L. All isolates were regarded as susceptible to polyhexanide, and no antagonism was observed between polyhexanide and the tested antibiotics. Synergism between polyhexanide and some bacteriostatic antibiotics (erythromycin, doxycycline and linezolid) was found for some strains.

CONCLUSIONS

Polyhexanide appears to be suitable for the topical treatment of S. aureus alone and in combination with antibiotics.

Community-genotype strains of methicillin-resistant Staphylococcus aureus with high-level mupirocin resistance in a neonatal intensive care unit

AIM

The aim of this study was to investigate the genotypes of mupirocin-resistant methicillin-resistant Staphylococcus aureus (MR-MRSA) isolates in our neonatal intensive care unit (NICU) and their potential source.

STUDY DESIGN

One hundred one MRSA isolates obtained from 59 inborn and 42 outborn infants were identified and their antimicrobial susceptibility determined. Using pulse-field gel electrophoresis (PFGE) analysis, MR-MRSA isolates obtained from the neonatal patients in the NICU were compared with those from adult hospitalized in the same hospital and with community-associated MRSA (CA-MRSA) isolates recovered from different hospitals in Korea.

RESULTS

Overall, 47% of CA-MRSA and 79% of healthcare-associated MRSA isolates exhibited high-level mupirocin resistance (HLMR). Forty-five percent of the outborn infants were considered to have CA-MRSA at the time of admission to our NICU. Most HLMR-MRSA isolates from neonates were grouped into a single cluster by PFGE analysis, and which included CA-MRSA isolates with HLMR recovered from outborn infants who were already colonized when they were transferred to our NICU. They belonged to the same PFGE group as the community-genotype strains isolated from different hospitals in Korea. HLMR-MRSA isolates from adults patients were classified as different clones. None of the attending staff in the NICU were nasal carriers.

CONCLUSION

Community-genotype strains of MRSA with HLMR may be imported to our NICU through obstetrics clinics and contribute to MRSA colonization or infection in facilities with a high rate of admission of outborn infants.

Trends in the susceptibility of methicillin-resistant Staphylococcus aureus to nine antimicrobial agents, including ceftobiprole, nemonoxacin, and tyrothricin: results from the Tigecycline In Vitro Surveillance in Taiwan (TIST) study, 2006-2010

This study investigated the in vitro susceptibilities of methicillin-resistant Staphylococcus aureus (MRSA) to nine antimicrobial agents in Taiwan. A total of 1,725 isolates were obtained from 20 hospitals throughout Taiwan from 2006 to 2010. The minimum inhibitory concentrations (MICs) of the nine agents were determined by the agar dilution method. The MICs of mupirocin and tyrothricin were determined for 223 MRSA isolates collected from 2009 to 2010. For vancomycin, 99.7 % were susceptible; however, 30.0 % (n = 517) exhibited MICs of 2 μg/ml and 0.3 % (n = 6) demonstrated intermediate susceptibility (MICs of 4 μg/ml). Nearly all isolates (≥ 99.9 %) were susceptible to teicoplanin, linezolid, and daptomycin. The MIC90 values were 2 μg/ml for ceftobiprole and 1 μg/ml for nemonoxacin. The MIC90 values of mupirocin and tyrothricin were 0.12 and 4 μg/ml, respectively. MIC creep was noted for daptomycin during this period, but not for vancomycin, teicoplanin, linezolid, or tigecycline. For isolates with vancomycin MICs of 2 μg/ml, the MIC90 values were 2 μg/ml for teicoplanin, 0.5 μg/ml for daptomycin, and 0.5 μg/ml for tigecycline. Those values were four- to eight-fold higher than those among isolates with vancomycin MICs of 0.5 μg/ml (2, 0.06, and 0.12 μg/ml, respectively). Of the nine MRSA isolates exhibiting non-susceptibility to vancomycin (n = 6), teicoplanin (n = 1), daptomycin (n = 2), or tigecycline (n = 1), all had different pulsotypes, indicating the absence of intra-hospital or inter-hospital spread. The presence of a high proportion of MRSA isolates with elevated MICs (2 μg/ml) and MIC creep of daptomycin might alert clinicians on the therapy for serious MRSA infections in Taiwan.

Activity of the antiseptic polyhexanide against meticillin-susceptible and meticillin-resistant Staphylococcus aureus

Staphylococcus aureus is one of the most important pathogens, with increasing emergence of meticillin-resistant S. aureus (MRSA) strains. This is associated not only with multiresistance to antibiotics but also with increasing resistance to topical antibiotics and antiseptics. As the antiseptic polyhexanide has only a low risk of emergence of resistant strains, the aim of the study was to obtain data on the sensitivity of S. aureus towards polyhexanide. The effect of polyhexanide was tested against 80 meticillin-susceptible S. aureus (MSSA) and 80 MRSA strains from sporadic cases as well as against 6 MRSA outbreak strains. The clonal diversity of the 166 strains was proven by pulsed-field gel electrophoresis (PFGE). Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined by the serial broth microdilution technique according to DIN 58940. Time-kill studies were performed for reference strains MSSA ATCC 29213 and MRSA ATCC 33591. MICs and MBCs in the range of 0.5-2mg/L were found. According to a created epidemiological cut-off (ECOFF) value of 4mg/L, all strains were regarded as susceptible to polyhexanide, including MRSA epidemic strains and MSSA and MRSA sporadic strains with various antibiotic susceptibility patterns. Addition of up to 4% albumin to the test medium did not change the MICs and MBCs. Time-kill studies showed reduction rates of 4log₁₀CFU/mL for 200mg/L and 5log₁₀CFU/mL for 400mg/L polyhexanide within 5-30min. It is concluded that polyhexanide is suitable for topical eradication of S. aureus.

Ex vivo porcine vaginal mucosal model of infection for determining effectiveness and toxicity of antiseptics

AIMS

To develop a semi-high-throughput ex vivo mucosal model for determining efficacy and toxicity of antiseptics.

METHODS AND RESULTS

Explants (5 mm) from freshly excised, porcine vaginal mucosa were infected with methicillin-sensitive Staphylococcus aureus (1 × 10(6)  CFU) at the epithelial surface for 2 h. Haematoxylin and eosin staining revealed healthy uninfected tissue and only minor disruptions in tissue infected with methicillin susceptible Staph. aureus (MSSA), which remained in outer epithelial cell layers. After 2 h infection, 10 μl of chlorhexidine digluconate (CHG, 3%), povidone-iodine (PI, 7·5%), octenidine dihydrochloride (OCT, 0·1%) or polyhexamethylene biguanide (PHMB, 0·1%) was applied. Antiseptics significantly reduced MSSA (1-4 log10  CFU/explants) after 0·25 h to 4 h. CHG, PHMB and OCT exhibited persistence at 24 h. In broth culture, CHG 0·012% and PI 0·625% achieved >6 log10 reductions at 2 h. PI-based formulations were more efficacious than unformulated PI. PI-based formulations exhibited no significant cytotoxicity on explants using an MTT assay.

CONCLUSIONS

All antiseptics tested in the mucosal MSSA infection model reduced MSSA. CHG and PI were more potent in broth culture.

SIGNIFICANCE AND IMPACT OF THE STUDY

We developed a semi-high-throughput mucosal model that can identify compounds or formulations with promising antimicrobial and limited cytotoxic properties.

Targeted versus universal decolonization to prevent ICU infection

BACKGROUND

Both targeted decolonization and universal decolonization of patients in intensive care units (ICUs) are candidate strategies to prevent health care-associated infections, particularly those caused by methicillin-resistant Staphylococcus aureus (MRSA).

METHODS

We conducted a pragmatic, cluster-randomized trial. Hospitals were randomly assigned to one of three strategies, with all adult ICUs in a given hospital assigned to the same strategy. Group 1 implemented MRSA screening and isolation; group 2, targeted decolonization (i.e., screening, isolation, and decolonization of MRSA carriers); and group 3, universal decolonization (i.e., no screening, and decolonization of all patients). Proportional-hazards models were used to assess differences in infection reductions across the study groups, with clustering according to hospital.

RESULTS

A total of 43 hospitals (including 74 ICUs and 74,256 patients during the intervention period) underwent randomization. In the intervention period versus the baseline period, modeled hazard ratios for MRSA clinical isolates were 0.92 for screening and isolation (crude rate, 3.2 vs. 3.4 isolates per 1000 days), 0.75 for targeted decolonization (3.2 vs. 4.3 isolates per 1000 days), and 0.63 for universal decolonization (2.1 vs. 3.4 isolates per 1000 days) (P=0.01 for test of all groups being equal). In the intervention versus baseline periods, hazard ratios for bloodstream infection with any pathogen in the three groups were 0.99 (crude rate, 4.1 vs. 4.2 infections per 1000 days), 0.78 (3.7 vs. 4.8 infections per 1000 days), and 0.56 (3.6 vs. 6.1 infections per 1000 days), respectively (P<0.001 for test of all groups being equal). Universal decolonization resulted in a significantly greater reduction in the rate of all bloodstream infections than either targeted decolonization or screening and isolation. One bloodstream infection was prevented per 54 patients who underwent decolonization. The reductions in rates of MRSA bloodstream infection were similar to those of all bloodstream infections, but the difference was not significant. Adverse events, which occurred in 7 patients, were mild and related to chlorhexidine.

CONCLUSIONS

In routine ICU practice, universal decolonization was more effective than targeted decolonization or screening and isolation in reducing rates of MRSA clinical isolates and bloodstream infection from any pathogen. (Funded by the Agency for Healthcare Research and the Centers for Disease Control and Prevention; REDUCE MRSA ClinicalTrials.gov number, NCT00980980).

Prevention of peritoneal dialysis catheter infections in Saudi peritoneal dialysis patients: the emergence of high-level mupirocin resistance

PURPOSE

Exit-site infection (ESI) and peritonitis remain the major causes of morbidity and mortality in peritoneal dialysis (PD) patients. This study compared the effectiveness of local mupirocin ointment and gentamicin cream in preventing both gram-positive and gram-negative bacterial infections in PD patients.

METHODS

Patients from two centers (n = 203) were assigned to daily mupirocin ointment or gentamicin cream application. Infections were tracked prospectively by organisms and expressed as episodes per patient-year for both ESI and peritonitis.

RESULTS

The rate of gram-positive ESI was 0.31/episode/patient-year and 0.22 episodes/patient-year (p<0.05), whereas the rate of gram-negative ESI was 0.28 episode/patient-year and 0.11 episode/patient-year (p<0.01) in the mupirocin group and gentamicin group, respectively. Gram-positive ESI occurred in 17.1% vs 10.2% of patients (p<0.05), whereas 20% of and 5.1% of patients (p<0.001) had gram-negative ESI in the 2 groups respectively. S.aureus was cultured at exit-site in the mupirocin group in 27.8% patients, 60% (16.7% of the total Gram-positive isolates) of them being with high-level mupirocin-resistance. Pseudomonas aeruginosa was cultured in 21.8% of ESI in the mupirocin group, and in only 6.7% in the gentamicin group (p<0.01). Peritonitis rates were lower using gentamicin cream, 0.17 episode/patient-year compared with mupirocin, 0.39 episode/patient-year (p<0.01). With multivariate analysis, only gentamicin exit-site use was a significant predictor for lower catheter infection rate.

CONCLUSION

Prolonged use of mupirocin for ESI-prophylaxis is associated with the emergence of mupirocin-resistant S. aureus. Gentamicin cream is superior to mupirocin ointment in the prevention of PD catheter infections.

Mupirocin and chlorhexidine resistance in Staphylococcus aureus in patients with community-onset skin and soft tissue infections

Decolonization measures, including mupirocin and chlorhexidine, are often prescribed to prevent Staphylococcus aureus skin and soft tissue infections (SSTI). The objective of this study was to determine the prevalence of high-level mupirocin and chlorhexidine resistance in S. aureus strains recovered from patients with SSTI before and after mupirocin and chlorhexidine administration and to determine whether carriage of a mupirocin- or chlorhexidine-resistant strain at baseline precluded S. aureus eradication. We recruited 1,089 patients with community-onset SSTI with or without S. aureus colonization. In addition to routine care, 483 patients were enrolled in a decolonization trial: 408 received intranasal mupirocin (with or without antimicrobial baths), and 258 performed chlorhexidine body washes. Patients were followed for up to 12 months with repeat colonization cultures. All S. aureus isolates were tested for high-level mupirocin and chlorhexidine resistance. At baseline, 23/1,089 (2.1%) patients carried a mupirocin-resistant S. aureus strain and 10/1,089 (0.9%) patients carried chlorhexidine-resistant S. aureus. Of 4 patients prescribed mupirocin, who carried a mupirocin-resistant S. aureus strain at baseline, 100% remained colonized at 1 month compared to 44% of the 324 patients without mupirocin resistance at baseline (P = 0.041). Of 2 patients prescribed chlorhexidine, who carried a chlorhexidine-resistant S. aureus strain at baseline, 50% remained colonized at 1 month compared to 48% of the 209 patients without chlorhexidine resistance at baseline (P = 1.0). The overall prevalence of mupirocin and chlorhexidine resistance is low in S. aureus isolates recovered from outpatients, but eradication efforts were less successful in patients carrying a mupirocin-resistant S. aureus strain at baseline.