Low-level Mupirocin Resistance Research Articles

Identification of Iles Gene Encoding Low-Level Mupirocin Resistance in Clinical Isolates of MRSA And MSSA

Identification of Iles Gene Encoding Low-Level Mupirocin Resistance in Clinical Isolates of MRSA And MSSA

Antimicrobial susceptibility pattern and mupirocin resistance among methicillin-resistant Staphylococcus aureus isolated from skin and soft-tissue infection patients attending a tertiary care hospital in North India

Background: Antimicrobial susceptibility among bacterial isolates varies from center to center. Mupirocin is a topical antibacterial antibiotic used to treat wound infections caused by methicillin-resistant Staphylococcus aureus (MRSA). Aim and Objectives: This study was conducted to know the prevalence of high and low levels of mupirocin resistance along with antimicrobial susceptibility in MRSA isolates from skin and soft-tissue infection in patients admitted to a tertiary care hospital in North India. Materials and Methods: A total of 97 non-repetitive isolates of MRSA from various pus samples over a period of 1 year were included in this study. These strains were identified as per standard laboratory protocols given by the Clinical Laboratory Standards Institute. High- and low-level mupirocin resistance of the isolates was tested by using mupirocin discs of 200 μg and 5 μg, respectively. Mupirocin strips of 256 μg and 512 μg were used for the E-test to detect low-level and high-level mupirocin resistance, respectively. The isolates were reported as sensitive to mupirocin, with minimum inhibitory concentrations of <4 mg/L. Results: Overall, 9.27% of mupirocin resistance was found, of which 2.06% of isolates were high-level resistant to mupirocin, while 7.21% had low-level resistance. All MRSA strains were susceptible to vancomycin, followed by linezolid (94.84%), teicoplanin (91.75%), and fusidic acid (88.65%). Conclusion: Regular monitoring, good infection control practices, and proper awareness about utilizing mupirocin therapeutically and prophylactically may help prevent the emergence of mupirocin resistance in health-care facilities.

Phenotypic and genotypic detection of multi drug resistant coagulase-positive Staphylococcus spp. isolates from canine pyoderma.

Dermatological infections in dogs are challenging to treat due to antibiotic resistance, which leads to longer recovery time and the need for stronger antibiotics. Aims: This study was undertaken to determine the prevalence of antimicrobial resistance in coagulase-positive staphylococcal isolates from pyoderma infection in dogs. This study also aimed to identify isolates with methicillin-resistance and multidrug resistance. 73 coagulase-positive staphylococci isolated from varying degrees of canine pyoderma cases. The samples were analyzed for the presence of Staphylococcus spp. using polymerase chain reaction (PCR) and resistance against antibiotics was studied by antimicrobial profile, minimum inhibitory concentration (MIC), and PCR on isolated bacteria. Out of 75 bacterial isolates identified, 73 isolates were confirmed as Staphylococcus species by PCR. A higher percentage of antibiotic resistance was observed against penicillin-G (46.27%), followed by amoxiclav (38.81%), enrofloxacin (32.84%), cefpodoxime, oxytetracycline (28.36% each), levofloxacin (26.86%), and co-trimoxazole (22.39%). 29 (49.15%) S. pseudintermedius, three (50.00%) S. schleiferi subsp. coagulans, and two (100%) S. aureus isolates exhibited multidrug resistance. However, one (1.49%) isolate (S. pseudintermedius) revealed low-level mupirocin resistance in the E-test. Also, 12 (20.34%) methicillin-resistant Staphylococcus pseudintermedius (MRSP), one (16.67%) methicillin-resistant S. schleiferi subsp. coagulans (MRSS) and one (50%) methicillin-resistant S. aureus (MRSA) were reported using PCR. This study helps to understand the increased level and pattern of resistance in coagulase-positive staphylococci isolated from different types of canine pyoderma cases.

Antimicrobial susceptibilities and genomic characteristics of methicillin-resistant Staphylococcus aureus resistant to mupirocin in Stockholm, Sweden.

The aim of this study was to investigate antimicrobial susceptibilities and genomic characteristics of mupirocin-resistant MRSA isolates in Stockholm, Sweden. In total, 44 non-duplicate mupirocin-resistant MRSA isolates detected in Stockholm during 2010-2022 were investigated. Antimicrobial susceptibility testing was performed using broth microdilution method and further tested for high-level mupirocin-resistance (MuH) and rifampicin by Etest®. All isolates were subjected to whole genome sequencing. 41 isolates presented MuH with MICs ≥1024 mg/L whilst three isolates displayed low-level mupirocin resistance (MuL). mupA-gene was detected in all MuH isolates. Point mutations in ileS gene leading to N213D and V588F were identified in the three MuL isolates. Mutation in rpoB (H481N) was detected in a rifampicin-resistant isolate. Among the isolates, 15 multi-locus sequence types (MLST) were identified, with the four most common sequence types (ST22, ST72, ST8, and ST125) accounting for 66% of the isolates. Mupirocin-resistant MRSA in Stockholm was uncommon, with a percentage of <0.5% among MRSA cases during 2010-2022. In the present study, most mupirocin-resistant isolates were MuH and mupA-positive, predominantly linked to ST22 or ST72 isolates. MuL-resistance was associated with a point mutation in the IleS protein. A multidrug-resistant ST1-MRSA-IV strain was resistant to both mupirocin and rifampicin.

Prevalence of High and Low-Level Mupirocin Resistance in Clinical Isolates of Staphylococcus Aureus from Skin and Soft Tissue Infection

The skin has an extremely diverse ecology of organisms that may produce infection. The clinical manifestations of skin and soft tissue infection(SSTIs) culminate in a two-step process involving invasion and the interaction of bacteria with host defenses. Approximately 7% to 10% of hospitalized patientsare affected by SSTIs. Mupirocin has been used to treat skin infections and eradicate the nasal carriage of MRSA. Our aim is to estimate the prevalence of lowand high-level Mupirocin resistance among the clinical isolates of Staphylococcus aureus from skin and soft tissue infection. The study was conducted in theDepartment of Microbiology, Krishna Institute of Medical Sciences, Krishna Hospital and Medical Research Centre, Karad, District- Satara. Specimen collectionand processing of samples were performed as per standards. The Kirby -Bauer disc diffusion method was used for the sensitivity to common antibioticsrecommended Clinical and Laboratory Standard Institute (CLSI 2021). Mupirocin resistance was detected using 5μg and 200μg Mupirocin discs to determineLow and High -level resistance. 135 Staphylococcus aureus isolates were obtained from patients admitted to various medical, surgical, and intensive care unitsand patients attending outpatient departments. Out of 415 clinically suspected cases of skin and soft tissue infection, 91.33% were culture positive, and 8.67%were culture negative. Out of 379 microorganisms, 44.06% were Gram-positive cocci, 27.44% were Gram negative bacilli, 24.27% were Gram negative cocci,and 14.22% were Gram-positive bacilli. Out of 167 Gram positive cocci, 135 (80.84%) were Staphylococcus aureus, 22 (13.17%) were Coagulase NegativeStaphylococcus and 10 (5.99%) were Micrococcus. We conclude that the prevalence of Staphylococcus aureus was 32.53%, among which Mupirocin high and lowlevelresistance was 5.92% and 7.41%, respectively.

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.

MINIMUM INHIBITORY CONCENTRATION LEVELS OF MUPIROCIN BY E-TEST AMONG STAPHYLOCOCCUS AUREUS ISOLATES AND THEIR ANTIMICROBIAL SUSCEPTIBILITY PATTERN

Objective: This study was done to evaluate the susceptibility of Staphylococcus aureus to mupirocin and to determine the antimicrobial susceptibility pattern of Staphylococcus aureus among various clinical isolates. Methods: All the consecutive, non-duplicative Staphylococcus aureus isolates collected during the year 2020 were subjected to the disk diffusion method to evaluate the antimicrobial susceptibility pattern and were stocked. Mupirocin susceptibility for all stocked Staphylococcus aureus was detected by Minimal inhibitory concentration (MIC) determination by Epsilometer test (E-test). Results: The total number of Staphylococcus aureus was 52. The maximum number of Staphylococcus aureus was isolated from pus sample 40 (76.9%). Among the 52 isolates, 26 (50%) were found to be methicillin-resistant Staphylococcus aureus (MRSA). All the isolates were susceptible to tetracycline (100%), vancomycin (100%), teicoplanin (100%), and linezolid (100%). By E-test, the overall prevalence of mupirocin resistance was 63.5%. Low-level Mupirocin resistance (MupRL) of 8-256 µg/ml was 59.6% and high-level mupirocin resistance (MupRH) of ≥512 µg/ml was 3.9%. Conclusion: The present study shows a high prevalence of mupirocin resistance (63.5%) which is a serious concern. Therefore, indiscriminate use of topical mupirocin in carriers is not advisable. It may be recommended only in case of an outbreak of skin and soft tissue infection attributed to Staphylococcus aureus.

Comparison of Disk Diffusion and Agar Dilution Method for the Detection of Mupirocin Resistance in Staphylococcal Isolates from Skin and Soft Tissue Infections.

Aims and Objectives Mupirocin is a widely used topical antibiotic for the treatment of skin and soft tissue infections. This has resulted in resistance leading to treatment failure. Hence, the present study aimed to determine the prevalence of mupirocin resistance among staphylococcal isolates obtained from the skin and soft tissue infections. Also, comparison of disc diffusion and agar dilution method in detecting mupirocin resistance was done. Materials and Methods This cross-sectional study was conducted in the Department of Microbiology of a tertiary health care center in Karnataka from January to December, 2018. Clinical samples such as wound swabs, tissues, and pus were included in the study. All staphylococcal isolates were screened for mupirocin resistance using 5 µg and 200 µg discs for low-level (MuL) and high-level mupirocin resistance (MuH), respectively. Minimum inhibitory concentration (MIC) was determined using the agar dilution method. Results Out of 100 staphylococcal isolates, 68 were Staphylococcus aureus and 32 were CoNS. MuH was detected in 11 isolates. MuH was more common in CoNS (10/11) compared with S. aureus (1/11). MuL was not found in the study. Discussion In our study, 10 out of 11 mupirocin-resistant isolates were methicillin resistant, which is statistically significant ( p < 0.05). The correlation between results of disc diffusion and MIC were appropriate in this study. Conclusion Judicial prescription of mupirocin after knowing the susceptibility report should become the standard practice. Screening for mupirocin resistance can be done by disc diffusion in resource-limited settings.

Dissemination of Methicillin-Resistant Staphylococcus aureus Sequence Type 764 Isolates with Mupirocin Resistance in China.

Mupirocin, a topical antimicrobial agent, is an important component in the eradication of methicillin-resistant Staphylococcus aureus (MRSA) colonization. The molecular characteristics of 46 mupirocin-resistant MRSA (MR-MRSA) clinical isolates were analyzed by multilocus sequence typing (MLST), staphylococcal cassette chromosome mec element (SCCmec) typing, spa typing, and analysis of virulence genes. All 26 MRSA isolates with low-level mupirocin resistance possessed a V588F mutation in ileS. Among 20 MRSA isolates with high-level resistance to mupirocin, all carried mupA; 2 isolates also possessed the V588F mutation in ileS, and 1 possessed the V631F mutation in ileS (isoleucyl-tRNA synthetase). The majority of MR-MRSA isolates were resistant to erythromycin, clindamycin, tetracycline, ciprofloxacin, and gentamicin, but the rates of resistance to rifampin and fusidic acid were 8.7% and 6.5%, respectively. Eight sequence types (STs) were found among the 46 MR-MRSA isolates, of which ST764 was the most prevalent (76.1%). The most frequent spa type identified was t1084 (52.2%). The SCCmec type most frequently found was type II (80.4%). The most common clone among low-level MR-MRSA isolates was ST764-MRSA-SCCmec type II-t1084 (23 isolates), while ST764-MRSA-SCCmec type II-t002 (9 isolates) was the most common clone among high-level MR-MRSA isolates. Additionally, all toxin genes except the seb gene were not identified among ST764 isolates. Among clonal complex 5 (CC5) isolates, immune evasion cluster (IEC)-associated genes (chp, sak, and scn) and seb were present in ST764 but absent in ST5, while sec, sel1, tsst-1, and hlb genes were identified in ST5 but absent in ST764. In conclusion, the spread of CC5 clones, especially a novel ST764-MRSA-SCCmec type II-t1084 clone with high-level resistance to mupirocin, was responsible for the increase in mupirocin resistance. These findings indicated that the emergence of the ST764 MR-MRSA clone involves a therapeutic challenge for treating serious MRSA infections. IMPORTANCE Mupirocin, a topical antibiotic that is commonly used for the nasal decolonization of MRSA and methicillin-sensitive Staphylococcus aureus in hospital settings and nursing homes, was introduced as a highly effective antibiotic against MRSA. Mupirocin acts by competitively binding isoleucyl-tRNA synthetase, thereby disrupting protein synthesis. This drug shows bacteriostatic and bactericidal activity at low and high concentrations, respectively. However, with the increase in mupirocin use, low-level and high-level resistance during nasal mupirocin treatment has been reported. In a previous study, the proportion of MRSA strains with high-level mupirocin resistance in a Canadian hospital increased from 1.6% in the first 5 years of surveillance (1995 to 1999) to 7.0% (2000 to 2004).

Dynamics of the Catalytic Active Site of Isoleucyl tRNA Synthetase from Staphylococcus aureus bound with Adenylate and Mupirocin.

The development of new antimicrobial drugs is critically needed due to the alarming increase in antibiotic resistance in bacterial pathogens. The active sites of different bacterial aminoacyl tRNA synthetases (aaRS) are validated targets of antibiotics. At present, the only aaRS inhibitor approved is mupirocin (MRC) which targets bacterial isoleucyl tRNA synthetase (IleRS). The present work is aimed at understanding the lacunae of knowledge concerning the active site conformational dynamics in IleRS in the presence of inhibitor mupirocin. With this end in view, we have carried out classical molecular dynamics simulation and metadynamics simulations of the open state of IleRS from Staphylococcus aureus (SaIleRS), the closed state tripartite complex bound with cognate adenylate (Ile-AMP) and tRNA, the closed state tripartite complex bound with noncognate MRC, and the closed state tripartite complex bound with tRNA and MRC with mutated SaIleRS (V588F). The present simulation established a dynamic picture of SaIleRS complexed with cognate and the noncognate substrates which are completely consistent with crystallographic and biochemical studies and explain the existing lacunae of knowledge. The active site is significantly more compact in the Ile-AMP bound complex compared to the open state due to the closure of the KMSKS and HMGH loops and clamping down of the tRNA acceptor end near the active site gate. The present result shows that the unusual open conformational state of the KMSKS loop observed in the cognate substrate-bound complex in the crystal is due to crystallographic constraints. Although the mupirocin tightly fits the catalytic active site in the MRC-bound complex, the nonanoic acid moiety is partly exposed to the water. The KMSKS loop is pushed open in the MRC-bound complex to accommodate the noncognate MRC. New tunnels open up, extending to the editing site in the complex. Out of its three broad segments, the C12 to C17 segment, the conjugated segment, and the nonanoic moiety, the conjugated part of MRC binds most effectively with the active site of the MRC-bound complex. The aromatic residues packing around the C12 to C17 segment of MRC stabilize the tRNA hairpin conformation in a similar way as observed in the TrpRS. The V588F mutation is weakening the interaction between this region of the active site and weakens the binding of MRC in the active site. This result explains why the V588F mutation is responsible for low-level mupirocin resistance. The free energy of unbinding the conjugated segment (and C12 to C17 segment, as well) largely contributes to the total free energy of unbinding the MRC. The active site organization of IleRS from eukaryotic Candida albicans is compared with the bacterial IleRS active site to understand the low binding affinity in eukaryotic IleRS. The present study could be a starting point of future studies related to the development of effective drug binding in the SaIleRS.

Detection and Distribution of Low Level and High Level Mupirocin Resistance among Clinical Methicillin Resistant Staphylococcus aureus Isolates

Introduction: Prolonged and improper use of antibiotics increases the resistance among pathogens and leads to life threatening implications and increases mortality. The incidence of mupirocin resistance in Methicillin Resistant Staphylococcus aureus (MRSA) clinical isolates were reportedly increasing. Aim: To determine the rate of high level and low level mupirocin resistance in clinical MRSA isolates in a tertiary care hospital. Materials and Methods: A cross-sectional study was carried out for a period of three months from December 2019- February 2020 in Department of Microbiology, PSG Institute of Medical Sciences and Research (PSG IMSR), Coimbatore, Tamil Nadu, India. A total of 100 non duplicate Staphylococcus aureus isolates from different specimens were subjected to mupirocin susceptibility by Kirby-Bauer disc diffusion method as per Clinical and Laboratory Standards Institute (CLSI) 2019 standards. The low (MuL) and high (MuH) level mupirocin resistance were detected by using 5 and 200 μg mupirocin discs (Himedia) respectively. The isolate exhibiting diameter of ≥14 mm indicates its susceptibility. The isolate exhibiting diameter ≤13 mm for both 5 and 200 μg indicates MuL and MuH strains respectively. Pearson’s Chi-square test calculated, p-value of &lt;0.05 was considered as statistically significant. Results: About 51 out of 100 (51%) Staphylococcus aureus isolates were found to be MRSA. In present study, 6 out of 51 (11.7 %) MRSA isolates were found to exhibit MuL and 5 out of 51 (9.8%) MRSA isolates were found to be having MuH. Low level and high level mupirocin resistance were not observed in Methicillin Sensitive Staphylococcus aureus (MSSA). Conclusion: The incidence of MuH and MuL resistance among MRSA were found to be 9.8% and 11.7% respectively. Screening for mupirocin resistant MRSA to be carried out periodically and stringent infection control practices to be in place to prevent further spread of mupirocin resistant MRSA.

Mupirocin Resistance of Staphylococcus aureus in Clinical Isolates of National Hospital and in the Nasal Carriage of Healthy Undergraduates in Colombo, Sri Lanka

Introduction and Objectives : Mupirocin resistance in Staphylococcus aureus is increasingly reported in many parts of the world. This study was conducted with the objective of describing high-level and low-level mupirocin resistance of S. aureus in clinical isolates and nasal carriage. Materials and Methods : A descriptive study was conducted including 45 nasal isolates of S. aureus collected from healthy university students in Colombo and 249 clinical isolates of S. aureus from the patient specimens in National Hospital of Sri Lanka. All of the confirmed S. aureus strains were tested for methicillin resistance using cefoxitin disc (30μg). S. aureus isolates were considered methicillin-resistant if the diameter of zone of inhibition was 21mm or less (CLSI, 2017). The S. aureus isolates were then tested for mupirocin resistance. Disk diffusion method was utilized with 5μg and 200μg mupirocin discs to determine low-level and high-level resistances respectively. The criterion employed for interpretation of mupirocin resistance was a combination of the widely accepted criterion described by Finlay, Miller, and Poupard (1997) for low-level mupirocin resistance and CLSI (2017) criterion for high-level mupirocin resistance. If both inhibition zone diameters for 5μg disk and 200μg were ≥14mm, the isolate was considered mupirocin sensitive. If 5μg disc displays &lt;14mm and 200 μg disk displayed ≥14mm inhibition zone diameter, the isolate was considered to be mupirocin low level resistant. If there is no inhibition zone in 200μg disk, the isolate was considered as mupirocin high level resistant. Results : From the 45 nasal carriage isolates, 33 (73%) were Methicillin sensitive Staphylococcus aureus (MSSA) and 12 (27%) were Methicillin Resistant Staphylococcus aureus (MRSA). Among the clinical isolates, majority (n=158, 63%) were MRSA while only 91 (37%) MSSA. An overall mupirocin resistance rate of 4.4% among S. aureus was observed. Low-level mupirocin resistance was observed in 3.7% Staphylococcus aureus isolates and high-level mupirocin resistance was observed in 0.7% isolates. Mupirocin low-level and high-level resistance in MRSA isolates were 5.3% and 0.6% respectively. MSSA isolates demonstrated 1.6% (n=2) and 0.8% (n=1) mupirocin low-level and high-level resistances respectively. None of the nasal isolates were resistant to mupirocin while 6% (n=15) mupirocin low-level resistance and 0.8% (n=2) mupirocin high-level resistance was observed in clinical isolates. Conclusion : This initial survey of mupirocin resistance among S. aureus in a country with fairly high usage of mupirocin emphasizes that although the overall mupirocin resistance is relatively low in this population, regular surveillance of mupirocin resistance remains a necessity.

Mupirocin Resistance in Staphylococcus aureus Isolated from Nasal Swabs of ICU and OT Staff- A Study from A Tertiary Care Hospital

Staphylococcus aureus is one of the common causes of Healthcare-associated infection. Staphylococcus colonizes the anterior nares of the nose and tends to disseminate and secondarily colonize several other body sites including the skin and the gut. Colonized hospital personnel may be an important factor in dissemination. Staphylococcus aureus to patients and vice-versa. Mupirocin is an excellent topical anti-staphylococcal antimicrobial agent used for eradicating nasal carriage. Resistance to Mupirocin is a threat for future use of this drug in eliminating nasal carriage of Staphylococcus aureus. Thus, this study was conducted to determine the rate of Mupirocin resistance among Staphylococcus aureus isolated from nasal swabs of Health care workers (HCWs ) of Operation Theatres (OTs) and Intensive Care Units (ICUs). A single nasal swab was collected from both the anterior nares of participating health care workers of ICU and OT once at the end of their shift. Antibiotic susceptibility testing of Staphylococcus aureus to various antibiotics was done by Kirby-Bauer disk diffusion method using CLSI guidelines. High and low-level Mupirocin resistance was determined. Among 282 nasal swabs collected, Staphylococcus aureus was isolated in 62 samples. Of Staphylococcus aureus 19 came out to be Methicillin-resistant (MRSA) and the remaining 43 Methicillin sensitive (MSSA). Mupirocin resistance was seen in 3 MRSA strains and 1 MSSA strain. Thus, overall 4/62 (6.5%) strains were MupR strains. Mupirocin is the most effective antibiotic used against colonization of Staphylococcus aureus in anterior nares. Resistance to this antibiotic is thus an alarm as well as a matter of great concern. Necessary steps, policies and guidelines need to be framed to stop the spread of this resistance.

Assessment of Mupirocin Resistance among Clinical Isolates of Methicillin Resistant Staphylococcus aureus

Background: Methicillin-resistant Staphylococcus aureus (MRSA) colonization is considered a major risk factor for nosocomial infections and its decolonization has reduced these infections. Mupirocin (MUP) is the topical antibiotic of choice for decolonization. MUP decolonization failure is attributed to MUP resistance. Objective: The aim of the current study is to assess MUP resistance among MRSA isolates phenotypically and genotypically. Methodology: Fifty MRSA isolates were identified in Microbiology Department in the Medical Research Institute hospital, Alexandria University. Antibiotic susceptibility to different classes of antibiotics by disk diffusion method was done. MUP minimum inhibitory concentration (MIC) was determined phenotypically by MUP Ezy MIC™ Strips. MUP resistance was determined genetically by multiplex PCR detection of mupA and mupB. Results: Of all MRSA isolates, 6% exhibited high level and none showed low level MUP resistance. Only mupA was detected in all resistant isolates. Conclusion: Despite low prevalence of MUP resistance, it is appropriate to test MUP resistance prior nasal decolonization

Prevalence of biocide resistance genes and chlorhexidine and mupirocin non-susceptibility in Portuguese hospitals during a 31-year period (1985–2016)

ObjectivesMethicillin-resistantStaphylococcus aureus (MRSA) remains a major human pathogen. MRSA decolonisation strategies frequently combine chlorhexidine baths and mupirocin nasal ointment. Although MRSA remains widespread in Portuguese hospitals, information regarding resistance to biocides and mupirocin is scarce. We evaluated the prevalence of biocide resistance genes and chlorhexidine and mupirocin non-susceptibility in a representative and well-characterised collection of MRSA isolated in Portuguese hospitals during a 31-year period (1985–2016). MethodsPrevalence of five biocide resistance genes (lmrS, mepA, sepA, qacAB and smr) was determined by PCR. Antibiotic susceptibility was assessed by disk diffusion and by MIC determination using broth microdilution (chlorhexidine) and Etest (mupirocin). ResultsChromosomal genessepA and mepA were detected in all isolates, while lmrS was found in 87.1%. The prevalence of plasmid-borne genes was significant for qacAB (22.4%), associated with the Iberian (ST247-I/IA) clone (P < 0.0001), and low for smr (1.0%) detected among isolates belonging to the ST239-III/IIIvariant clone. Chlorhexidine non-susceptibility (MIC ≥ 4 mg/L) was observed in two isolates belonging to the EMRSA-15 clone (ST22-IV). Non-susceptibility to mupirocin (MIC > 1 mg/L) was significant (15.4%; n = 31) and mainly found among isolates of the EMRSA-15 clone (P < 0.0001; n = 29). One isolate presented low-level mupirocin resistance (MIC = 32 mg/L), and two missense mutations N213D (A637G) and V588F (G1762T) were identified in the ileS gene. ConclusionConcerningly, we detected a high prevalence of biocide resistance genes and an association of mupirocin and chlorhexidine non-susceptibility with the dominant EMRSA-15 clone in Portuguese hospitals.

Eradication of Staphylococcus aureus colonization by chronic use of mupirocin in patients on home parenteral nutrition.

Although in other groups Staphylococcus aureus eradication has proven to be an effective infection prevention measure, to our knowledge, no such studies have been performed in patients on home parenteral nutrition (HPN). The aim of this study was to investigate the efficacy of chronic nasal mupirocin use on S. aureus eradication and prevention of catheter related infections in patients on HPN. This was a cohort study with data collected from adult patients on HPN who were screened for S. aureus carriage. In case of carriage, the patient was instructed to apply mupirocin nasal ointment monthly. Outcomes were the percentage of successful S. aureus eradication and the effect on the incidence of catheter-related infections and development of mupirocin resistance. S. aureus nasal carriage was found in 54% of the patients. Eradication was successful in 66% (70 of 106) of patients treated with mupirocin. Overall S. aureus catheter-related infection rates decreased by 50% (P=0.02). The decrease was mostly due to a drop in central line-associated bloodstream infection (CLABSI) rates (0.26versus 0.1 per 1000 central venous catheter days; P=0.04). The overall CLABSI rates decreased as well (incidence ratio rate, 0.43; 95% confidence interval. 0.24-0.76; P < 0.01). Low-level mupirocin resistance was observed in four patients. Findings from the present study highlighted the potential usefulness of mupirocin ointment prophylaxis to establish S. aureus eradication in patients on HPN. However, awareness for the development of mupirocin resistance is prudent. Further research needs to be carried out to validate these findings.

Localization and Characterization of MupA Gene in High and Low-Level Mupirocin Resistant Methicillin Resistant Staphylococcus Aureus

Background: Two types of mupirocin resistance among methicillin resistant Staphylococcus aureus (MRSA) have been reported; low-level mupirocin resistance (LL-MR), and high-level mupirocin resistance (HL-MR). The mupA gene is typically located on mobile genetic elements which facilitate the resistance dissemination. Objective: The aim of this work was to identify the mupA gene location, as well as the restriction fragment length polymorphism (RFLP) patterns in high and low-level mupirocin resistant MRSA. Methodology: This study was conducted on 100 MRSA isolates; seven of them were mupirocin resistant. The E test was used to identify high and low level mupirocin resistance. Amplification of mupA gene in total and plasmid DNA was performed. We also detected the spacer region (trsLM–IS257-like–mupA) in the 7 isolates by PCR then we investigated its RFLP patterns. Results: Four MR MRSA isolates had low level resistance, their MupA gene was located on chromosomal DNA, whereas, three isolates showed high level MR, their MupA gene was located on plasmid DNA. Four types of different RFLP patterns of the spacer region were identified; type-1 included two LL-MR isolates, each of type-2 and 3 included both HL-MR and LL-MR isolates, and type-4 included one HL-MR isolate. Conclusions: Staphylococcus aureus mupA gene responsible for LL-MR is located on the chromosome while that responsible for HL-MR is plasmid-mediated. The spacer region variations appear to occur in both chromosomal and plasmid-located mupA gene regardless the type of mupirocin resistance.

Prevalence and molecular characterization of methicillin-resistant Staphylococcus aureus with mupirocin, fusidic acid and/or retapamulin resistance

BackgroundThe data on the prevalence of resistance to mupirocin (MUP), fusidic acid (FA) and retapamulin (RET) in methicillin-resistant Staphylococcus aureus (MRSA) from China are still limited. This study aimed to examine these three antibiotics resistance in 1206 MRSA clinical isolates from Eastern China. Phenotypic MUP, FA and RET resistance was determined by minimum inhibitory concentrations (MICs), and genotypic by PCR and DNA sequencing of the mupA/B, fusB-D, cfr, vgaA/Av/ALC/B/C/E, lsaA-C/E and salA and mutations in ileS, fusA/E, rplC, and 23S RNA V domain. The genetic characteristics of resistance isolates were conducted by pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST).ResultsOverall MRSA MUP, FA and RET resistance was low (5.1, 1.0 and 0.3%, respectively). MupA was the mechanism of high-level MUP resistance. All low-level MUP resistance isolates possessed an equivocal mutation N213D in IleS; of these, 2 reported an additional V588F mutation with an impact on the Rossman fold. FusA mutations, such as L461K, H457Q, H457Y and V90I were the primary FA mechanisms among high-level resistance isolates, most of which also contained fusC; however, all low-level resistance strains carried fusB. Except lsaE gene detected in one isolate, no other resistance mechanisms tested were found among RET-resistant isolates. Additionally, sixteen PFGE types (A-P) were observed, among which type B was the most common (49/76, 64.5%), followed by types E and G (4/76, 5.3% each) and types C and M (3/76, 3.9% each). All resistant strains were divided into 15 ST types by MLST. ST764 (24/76, 31.6%), ST630 (11/76, 14.5%), ST239 (9/76, 11.8%) and ST5 (7/76, 9.2%) were the major types. PFGE type B isolates with the aforementioned STs were mainly found in mupirocin resistant isolates.ConclusionsMUP, FA and RET exhibited highly activity against the MRSA isolates. Acquired genes and chromosome-borne genes mutations were responsible for MUP and FA resistance; however, the mechanism for some RET-resistant isolates remains to be further elucidated. Also, the surveillance to MUP in MRSA should be strengthened to prevent elevated resistance due to the expansion of clones.

Genetic analysis of toxic shock syndrome toxin (TST) positive Staphylococcus aureus strains isolated from wound infections in Tehran hospitals, Iran

Today Staphylococcus aureus strains harboring tst gene are considered to be one of the major public health challenges around the world. Regarding to lack of data on molecular characteristics of these strains, the present study was performed to investigate characteristics and prevalence of antibiotic resistance genes of different agr types of Staphylococcus aureus strains carrying tst gene. In this cross-sectional study, 58 Staphylococcus aureus isolates carrying tst gene related to wound infectiofns were investigated. Isolates were characterized for in vitro antimicrobial susceptibility, mecA gene presence, resistance gene detection, and agr typing. Prevalence of S. aureus harboring tst gene was 29.7%. Methicillin-resistant S. aureus were mainly present in S. aureus harboring tst gene (56.9%). Twenty-seven (46.2%) isolates were confirmed as multidrug resistance (MDR). Out of 12 mupirocin resistant isolates (20.7%), 4 (6.9%) and 8 (13.8%) were high and low-level mupirocin resistance respectively. The frequencies of cMLSB, iMLSB, and MS phenotypes were detected 25.9%, 17.2% and 6.9%, respectively. Among tested isolates, the predominant genes were mecA in 56.9% isolates, followed by tet(M) in 48.3%, aac (6′)-Ie/aph (2″) in 27.6%, ant (4′)-Ia and erm(C) each in 20.7%, aph (3′)-IIIa in 17.2%, msr(B) in 10.3%, erm(A) and mupA each in 6.9% and msr(A) in 1.7% of isolates. agr types detected in tested strains were mainly type I (36.2%), III (25.9%), II (20.7%), and IV (17.2%). These findings indicated relatively high resistance among methicillin-resistant S. aureus harboring tst gene which was distributed in agr type I highlighting particular importance of diagnosis of tst-positive S. aureus strains to choose appropriate antibiotics for the effective treatment of infections due to these bacteria.

The prevalence and molecular mechanisms of mupirocin resistance in Staphylococcus aureus isolates from a Hospital in Cape Town, South Africa

BackgroundAntimicrobial resistance is an increasingly serious problem in public health globally. Monitoring resistance levels within healthcare and community settings is critical to combat its ongoing increase. This study aimed to describe the rates and molecular mechanisms of mupirocin resistance in clinical Staphylococcus aureus isolates from Tygerberg Hospital, and to describe its association with strain types.MethodsWe retrospectively selected 212 S. aureus isolates which were identified from blood samples and pus swabs during the years 2009–2011 and 2015–2017. The isolates were identified using conventional microbiological methods and genotyping was done using spa typing. Cefoxitin (30 μg) disc diffusion and the two disc strategy (5 μg and 200 μg) were used to determine susceptibility to methicillin and mupirocin, respectively. Isolates with high-level resistance were screened for the plasmid mediated genes mupA and mupB by PCR, and sequencing of the ileS gene was done for all isolates exhibiting low-level resistance to describe the mutations associated with this phenotype. Chi-square test was used to assess the associations between mupirocin resistance and S. aureus genotypes.ResultsOf 212 S. aureus isolates, 12% (n = 25) were resistant to mupirocin, and 44% (n = 93) were methicillin resistant. Strain typing identified 73 spa types with spa t045 being the most predominant constituting 11% of the isolates. High-level mupirocin resistance was observed in 2% (n = 5), and low-level resistance in 9% (n = 20) of the isolates. The prevalence of high-level mupirocin resistance amongst MRSA and MSSA was 4 and 1% respectively, while the prevalence of low-level mupirocin resistance was significantly higher in MRSA (18%) compared to MSSA (3%), (p = 0.032). mupA was the only resistance determinant for high-level resistance, and the IleS mutation V588F was identified in 95% of the isolates which showed low-level resistance. A significant association was observed between spa type t032 and high-level mupirocin resistance, and types t037 and t012 and low-level resistance (p < 0.0001).ConclusionThe study reported higher rates of low-level mupirocin resistance compared to high-level resistance, and in our setting, mupirocin resistance was driven by certain genotypes. Our study advocates for the continuous screening for mupirocin resistance in S. aureus in clinical settings to better guide treatment and prescribing practices.