Six-Year Retrospective Review of Hospital Data on Antimicrobial Resistance Profile of Staphylococcus aureus Isolated from Skin Infections from a Single Institution in Greece

In Vitro Activities of Ceftobiprole, Dalbavancin, Tedizolid and Comparators against Clinical Isolates of Methicillin-Resistant Staphylococcus aureus Associated with Skin and Soft Tissue Infections

Skin and soft tissue infections (SSTIs) are associated with significant morbidity and healthcare costs, especially when caused by methicillin-resistant Staphylococcus aureus (MRSA). Vancomycin is a preferred antimicrobial therapy for the management of complicated SSTIs (cSSTIs) caused by MRSA, with linezolid and daptomycin regarded as alternative therapeutic options. Due to the increased rates of antimicrobial resistance in MRSA, several new antibiotics with activity against MRSA have been recently introduced in clinical practice, including ceftobiprole, dalbavancin, and tedizolid. We evaluated the in vitro activities of the aforementioned antibiotics against 124 clinical isolates of MRSA obtained from consecutive patients with SSTIs during the study period (2020-2022). Minimum inhibitory concentrations (MICs) for vancomycin, daptomycin, ceftobiprole, dalbavancin, linezolid and tedizolid were evaluated by the MIC Test Strip using Liofilchem strips. We found that when compared to the in vitro activity of vancomycin (MIC₉₀ = 2 μg/mL), dalbavancin possessed the lowest MIC₉₀ (MIC₉₀ = 0.094 μg/mL), followed by tedizolid (MIC₉₀ = 0.38 μg/mL), linezolid, ceftobiprole, and daptomycin (MIC₉₀ = 1 μg/mL). Dalbavancin demonstrated significantly lower MIC₅₀ and MIC₉₀ values compared to vancomycin (0.064 vs. 1 and 0.094 vs. 2, respectively). Tedizolid exhibited an almost threefold greater level of in vitro activity than linezolid, and also had superior in vitro activity compared to ceftobiprole, daptomycin and vancomycin. Multidrug-resistant (MDR) phenotypes were detected among 71.8% of the isolates. In conclusion, ceftobiprole, dalbavancin and tedizolid exhibited potent activity against MRSA and are promising antimicrobials in the management of SSTIs caused by MRSA.

Phenotypic and Molecular Detection of Biofilm Formation in Methicillin-Resistant Staphylococcus Aureus Isolated from Different Clinical Sources in Erbil City

Background

Staphylococcus aureus is an important causative pathogen. The production of biofilms is an important factor and makes these bacteria resistant to antimicrobial therapy.

Objectives

the current study aimed to assess the prevalence of resistance to antibacterial agents and to evaluate the phenotypic and genotypic characterization of biofilm formation among S. aureus strains.

Methods

This study included 50 isolates of Methicillin-resistant S. aureus (MRSA) and Methicillin-Susceptible S. aureus (MSSA). S. aureus was identified by molecular and conventional methods, and antimicrobial resistance was tested with a disc diffusion method. The biofilm formation was performed through the Microtiter plate method. Strains were subjected to PCR to determine the presence of nuc, mecA, icaA, icaB, icaC, and icaD genes.

Results

Of the 50 S. aureus isolates, 32(64%) and 18(36%) were MRSA and MSSA, respectively. A large number of MRSA and MSSA isolates showed resistance to Penicillin and Azithromycin, and a lower number of MRSA and MSSA isolates showed resistance to Amikacin Gentamicin. None of the isolates was resistant to Vancomycin. The MRSA strains had significantly higher resistance against antibiotics than MSSA strains (P = 0.0154). All isolates (MRSA and MSSA) were able to produce biofilm with levels ranging from strong (31.25 %), (16.6%) to moderate (53.12%), (50%) to weak (15.6%), (33.3%) respectively. The MRSA strains had a significantly higher biofilm formation ability than the MSSA strains (P = 0.0079). The biofilm-encoding genes were detected among isolates with different frequencies. The majority of S. aureus isolates, 42 (84%), were positive for the icaA. The prevalence rates of the icaB, icaC and icaD genes were found to be 37 (74%), 40 (80%) and 41 (82%), respectively.

Conclusions

The prevalence of biofilm encoding genes associated with multidrug resistance in S. aureus strains is high. Therefore, identifying epidemiology, molecular characteristics, and biofilm management of S. aureus infection would be helpful.

Burden of Antibiotic Resistance at Wolaita Sodo University Comprehensive Specialized Hospital

Background

Antibiotic resistance is a serious threat to the human population everywhere. However, less attention is given to its concern in sub-Saharan Africa including Ethiopia. There is an information gap concerning antibiotic resistance and its pattern in Wolaita Sodo University Teaching Referral Hospital. This study is aimed at investigating the prevalence of antimicrobial resistance in the study area.

Methods

Five-year retrospective data of cultures and records of 581 patients were utilized to analyze the pattern of antibiotic resistance. The statistical software including SPSS version 25 and Microsoft excel 2013 were used. Laboratory records with incompletely registered age, sex, culture isolation, or drug susceptibility test data were excluded.

Results

Out of the total of 581 samples extracted from the microbiology laboratory, 237 (40.8%) samples were culture positive for bacteria. From positive culture growth, 165 (69.6%) were gram-positive bacteria whereas 72 (30.4%) were gram negative. Staphylococcus aureus was the most prevalent isolate among gram-positive isolates as Escherichia coli was for gram-negative isolates. Overall antibiotic resistance of gram-positive isolates was 57.2% whereas that of gram-negative bacteria was 58.8%.

Conclusion

S. aureus and E. coli were found to be the most prevalent pathogenic isolates among gram-positive and gram-negative bacteria, respectively. Most of the isolated pathogens showed high resistance towards the commonly prescribed antibiotic agents. The overall antibiotic resistance in this study was 57.7%, and the overall MDR prevalence was 72.2%.

Emergence of a mupirocin-resistant, methicillin-susceptible Staphylococcus aureus clone associated with skin and soft tissue infections in Greece

BACKGROUND

Staphylococcus aureus causes various infections, including skin and soft tissue infections (SSTIs). In this study, methicillin-susceptible S. aureus (MSSA) from SSTIs among patients in three tertiary-care hospitals in Greece were studied in terms of antimicrobial resistance, clonal distribution, toxin and adhesin genes carriage.

RESULTS

During a five-year period (2014-2018), 6145 S. aureus were recovered from 13,244 patients with SSTIs and tested for antimicrobial susceptibility. MSSA were 4806 (78.21 %) including 1484 isolates with mupirocin minimum inhibitory concentration (MIC) > 64 mg/L (30.88 %). Two hundred and sixty representative mupirocin-resistant MSSA were analyzed for genes encoding Panton-Valentine leukocidin (PVL, lukS/lukF-PV), exfoliative toxins (eta, etb), adhesin FnbA (fnbA) and resistance genes mupA (high-level resistance to mupirocin), fusB (fusidic acid), aminoglycosides' modifying enzymes, ermA, ermC and msrA (macrolides/lincosamides) by PCRs. Strains were classified into clones by PFGE and MLST. All mupirocin-resistant MSSA were penicillin-resistant; 92.7 % expressed resistance to fusidic acid and 88.9 % to tobramycin. All 260 molecularly analyzed isolates were mupA-positive; all fusidic acid-resistant (241/260) carried fusB whereas, the tobramycin-resistant ones (230), ant(4')-Ia. The majority carried eta (93.85 %), etb (98.08 %) and fnbA (88.85 %). PFGE typing revealed a mostly unvarying population; 260 MSSA were grouped into three types. One major eta/etb-positive clone comprising of 258/260 strains (99.2 %), PFGE type 1, was classified as ST121, including nine strains co-carrying PVL. Another PVL-positive strain was identified as ST1, and one toxins-negative as ST21.

CONCLUSIONS

A mupirocin-resistant MSSA clone, ST121, carrying resistance, exfoliative toxins and adhesin genes, was spread and predominated in SSTIs from patients in Greece during the five-year studied period.

Nationwide Surveillance on Antimicrobial Resistance Profiles of Staphylococcus aureus Isolated from Major Food Animal Carcasses in South Korea During 2010-2018

Contamination of meat with antimicrobial-resistant bacteria represents a major public health threat worldwide. In this study, we determined the antimicrobial resistance profiles and resistance trends of Staphylococcus aureus isolated from major food animal carcasses (408 cattle, 1196 pig, and 1312 chicken carcass isolates) in Korea from 2010 to 2018. Approximately 75%, 92%, and 77% of cattle, pig, and chicken carcass isolates, respectively, were resistant to at least one antimicrobial agent. Resistance to penicillin (62.1%) was the highest, followed by resistance to tetracycline (42.1%) and erythromycin (28.2%). About 30% of pig and chicken isolates were resistant to ciprofloxacin. We observed linezolid resistance only in pig isolates (2.3%). However, all S. aureus isolates were sensitive to rifampin and vancomycin. We noted an increasing but fluctuating trend of kanamycin and penicillin resistance in cattle isolates. Similarly, the chloramphenicol, ciprofloxacin, tetracycline, and trimethoprim resistance rates were increased but fluctuated through time in pig isolates. Methicillin-resistant S. aureus (MRSA) accounted for 5%, 8%, and 9% of the cattle, pig, and chicken isolates, respectively. The MRSA strains exhibited significantly high resistance rates to most of the tested antimicrobials, including ciprofloxacin, erythromycin, and tetracycline compared with methicillin-susceptible S. aureus (MSSA) strains. Notably, a relatively high percentage of MRSA strains (5.2%) recovered from pig carcasses were resistant to linezolid compared with MSSA strains (2.1%). In addition, almost 37% of the isolates were multi-drug resistant. S. aureus isolates recovered from major food animal carcasses in Korea exhibited resistance to clinically important antimicrobials, posing a public health risk.

Clonal Lineages, Antimicrobial Resistance, and PVL Carriage of Staphylococcus aureus Associated to Skin and Soft-Tissue Infections from Ambulatory Patients in Portugal

Staphylococcus aureus (S. aureus) is a leading cause of skin and soft-tissue infections (SSTIs) in the community. In this study, we characterized a collection of 34 S. aureus from SSTIs in ambulatory patients in Portugal and analyzed the presence of Panton–Valentine leucocidin (PVL)-encoding genes and antibiotic-resistance profile, which was correlated with genetic determinants, plasmid carriage, and clonal lineage. Nearly half of the isolates (15, 44.1%) were methicillin-resistant Staphylococcus aureus (MRSA) and/or multidrug resistant (MDR). We also detected resistance to penicillin (33/34, 97.1%), fluoroquinolones (17/34, 50.0%), macrolides and lincosamides (15/34, 44.1%), aminoglycosides (6/34, 17.6%), and fusidic acid (2/34, 5.9%), associated with several combinations of resistance determinants (blaZ, erm(A), erm(C), msr(A), mph(C), aacA-aphD, aadD, aph(3′)-IIIa, fusC), or mutations in target genes (fusA, grlA/gyrA). The collection presented a high genetic diversity (Simpson’s index of 0.92) with prevalence of clonal lineages CC5, CC22, and CC8, which included the MRSA and also most MDR isolates (CC5 and CC22). PVL-encoding genes were found in seven isolates (20.6%), three methicillin-susceptible Staphylococcus aureus (MSSA) (ST152-agrI and ST30-agrIII), and four MRSA (ST8-agrI). Plasmid profiling revealed seventeen distinct plasmid profiles. This work highlights the high frequency of antimicrobial resistance and PVL carriage in SSTIs-related S. aureus outside of the hospital environment.

In Silico Evaluation of Human Cathelicidin LL-37 as a Novel Therapeutic Inhibitor of Panton-Valentine Leukocidin Toxin of Methicillin-Resistant Staphylococcus aureus

Incidence of drug resistance in clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) is attributed to its diverse repertoire of virulence factors. Of these virulence determinants, Panton-Valentine Leukocidin (PVL) has been experimentally validated as a prospective drug target due to its conspicuous and comprehensive role in nosocomial infections. This study encompassed an in silico approach to elucidate the antimicrobial potentiality of human cathelicidin LL-37 against PVL toxin of MRSA. Molecular docking studies of LL-37 and its segments with the PVL toxin subunits LukS and LukF were carried out using PatchDock server and the results were refined using FireDock server. The paramount ligand-receptor combination was selected and analyzed based on diverse parametric attributes and compared with the commercial inhibitors of PVL viz. Andrimid, Beclobrate, Beta-sitosterol, Diathymosulfone, and Probucol to determine the most potent inhibitor among them. Our results elucidated that the interaction of LL-37 with the LukS subunit of PVL toxin (minimum global energy of -61.82 kcal/mol) depicted 34 molecular interactions, while the commercial PVL inhibitors depicted fewer and insubstantial interactions. SWISS-ADME (Absorption, Distribution, Metabolism, and Excretion) and ToxinPred analysis of LL-37 further corroborated its null potency of toxicity in systemic milieu. The results obtained may credit this study as basis for the development of LL-37 as a potential inhibitor against virulent MRSA toxins, thereby exalting the treatment regimes for nosocomial infections in health care facilities worldwide.

Characterization of methicillin-resistant Staphylococcus aureus through genomics approach

In the present study, a total of 35 S. aureus isolates collected from two different geographical locations viz., Germany and Hungary were tested for their methicillin-resistant phenotype which revealed a high incidence of methicillin-resistant S. aureus. The quantitative test for biofilm production revealed that 73.3% of isolates were biofilm producers. The isolates were further characterized using a set of biochemical and genotypic methods such as amplification and analysis of S. aureus species-specific sequence and mecA gene. The 33 mecA positive isolates were then characterized by the amplification of SCCmec and pvl toxin genes. Further, based on the biofilm-forming phenotype, 15 isolates were selected and characterized through PCR–RFLP of coa gene, polymorphism of spa gene and amplification of biofilm-associated genes. The dendrogram prepared from the results of both biochemical and genotypic analyses of the 15 isolates showed that except for the isolates SA G5 and SA H29, the rest of the isolates grouped themselves according to their locations. Thus, the two isolates were selected for further characterization through whole-genome sequencing. Comparative genome analysis revealed that SA G5 and SA H29 have 97.20% ANI values with 2344 gene clusters (core-genome) of which 16 genes were related to antibiotic resistance genes and 57 genes encode virulence factors. The highest numbers of singleton genes were found in SA H29 that encodes proteins for virulence, resistance, mobile elements, and lanthionine biosynthesis. The high-resolution phylogenetic trees generated based on shared proteins and SNPs revealed a clear difference between the two strains and can be useful in distinguishing closely related genomes. The present study demonstrated that the whole-genome sequence analysis technique is required to get a better insight into the MRSA strains which would be helpful in improving diagnostic investigations in real-time to improve patient care.

Prevalence of fosfomycin resistance and gene mutations in clinical isolates of methicillin-resistant Staphylococcus aureus

Background

Fosfomycin exhibits excellent in vitro activity against multidrug-resistant pathogens, including methicillin-resistant Staphylococcus aureus (MRSA). Increasing fosfomycin resistance among clinical MRSA isolates was reported previously, but little is known about the relative abundance of Fosfomycin resistance genes in MRSA isolates circulating in Taiwan.

Methods

All MRSA isolates, collected in 2002 and 2012 by the Taiwan Surveillance of Antimicrobial Resistance (TSAR) program, were used in this study. Susceptibility to various antimicrobial agents, including fosfomycin, was determined by broth microdilution. Genetic determinants of fosfomycin resistance, including fosB carriage and murA, glpT and uhpT mutations, were investigated using PCR and sequencing of amplicons. Staphylococcal protein A (spa) typing was also performed to determine the genetic relatedness of MRSA isolates.

Results

A total of 969 MRSA strains, 495 in the year 2002 and 474 in the year 2012, were analyzed. The overall in vitro susceptibility was 8.2% to erythromycin, 18.0% to clindamycin, 29.0% to tetracycline, 44.6% to ciprofloxacin, 57.5% to trimethoprim/sulfamethoxazole, 86.9% to rifampicin, 92.9% to fosfomycin and 100% to linezolid and vancomycin. A significant increase in the fosfomycin resistance rate was observed from 3.4% in 2002 to 11.0% in 2012. Of 68 fosfomycin-resistant MRSA isolates, several genetic backgrounds probably contributing to fosfomycin resistance were identified. Twelve isolates harbored the fosB gene, and various mutations in murA, uhpT, and glpT genes were noted in 11, 59, and 66 isolates, respectively. The most prevalent gene mutations were found in the combination of uhpT and glpT genes (58 isolates). The vast majority of the fosfomycin-resistant MRSA isolates belonged to spa type t002.

Conclusions

An increased fosfomycin resistance rate of MRSA isolates was observed in our present study, mostly due to mutations in the glpT and uhpT genes. Clonal spread probably contributed to the increased fosfomycin resistance.

Is coverage of S. aureus necessary in cellulitis/erysipelas? A literature review

BACKGROUND

Empirical treatment of patients with cellulitis/erysipelas usually targets both streptococci and methicillin-sensitive S. aureus (MSSA). However, the recommendation to empirically cover MSSA is weak and based on low-quality evidence.

METHODS AND OBJECTIVE

A systematic review was conducted in PubMed and clinical trial registries to assess the role of S. aureus in cellulitis/erysipelas and the need for empirical MSSA coverage.

RESULTS

Combined microbiological and serological data, and response to penicillin monotherapy suggest that streptococci are responsible for the vast majority of cases of cellulitis/erysipelas. However, most cases are non-culturable and the specificity of microbiological and serological studies is questionable based on recent studies using molecular techniques. According to epidemiological data and three randomized controlled trials, empirical coverage of methicillin-resistant S. aureus (MRSA) is not recommended for most patients, despite the high prevalence of MRSA in many areas. If MRSA is indeed not an important cause of uncomplicated cellulitis/erysipelas, then the same may apply to MSSA. Based on indirect comparison of data from clinical studies, cure rates with penicillin monotherapy (to which most MSSA are resistant) are comparable to the cure rates reported in many studies using wider-spectrum antibiotics.

CONCLUSION

Considering the limitations of microbiological studies in identifying the pathogens responsible for cellulitis/erysipelas, treatment needs to be guided by clinical trials. Trials comparing penicillin or amoxicillin monotherapy to MSSA-covering regimens are needed to definitively answer whether empirical coverage of MSSA is needed and to identify the subset of patients that can be safely treated with penicillin or amoxicillin monotherapy.

Antimicrobial overuse and misuse in the community in Greece and link to antimicrobial resistance using methicillin-resistant S. aureus as an example

Both antimicrobial consumption and antimicrobial resistance are very high in Greece, ranking among the highest of Europe. The link between antimicrobial consumption and resistance is well-known. Here, we discuss the reasons of antimicrobial overuse in Greece in the community (such as self-medication, dispersion of antibiotics by pharmacies without prescription, over-prescription by physicians, patient expectations and liability pressure) and we explore the misuse of antibiotics for common community infections. Furthermore, we discuss how such overuse/misuse can drive antimicrobial resistance, using methicillin-resistance in Staphylococcus aureus as an example. S. aureus is one of the pathogens with high rates of resistance in Greece. Comparing the rate of antimicrobial susceptibility to non-beta lactams between methicillin-resistant and methicillin-sensitive S. aureus we highlight the antibiotics that have the potential to drive methicillin-resistance through co-selection. Based on the above we identify targets for intervention in order to reduce antimicrobial overuse/misuse in the community in Greece.

Nasal Decolonisation of MRSA

The recent demonstration for the first time of urinary monic acid A as a clinical urinary biomarker of exposure to intra-nasal mupirocin during medication for methicillin-resistant Staphylococcus aureus (MRSA) offers a way of verifying adherence to the regimen. However, absence of the biomarker in some patients needs explanation, to ensure that efficient decolonisation has not been compromised by confounding circumstances, and that additional resistance to mupirocin has not unwittingly been encouraged.