Methicillin-resistant S. Aureus Strains Research Articles

Occurrence of high level methicillin resistance Staphylococcus aureus in patients from health facilities in Akwa Ibom State, Nigeria

Background: Methicillin resistant S. aureus (MRSA) has become a major public health predicament worldwide. This is owing to its involvement in the evolution of MDR strains and difficulty in therapeutic management of infected patients. This study was conducted to investigate the prevalence of methicillin resistance Staphylococcus aureus among patients in two health facilities in Akwa Ibom State, Nigeria. Materials and Methods: Clinical isolates of patients from University of Uyo Teaching Hospital (UUTH), Uyo and General Hospital, Ikot Abasi (GHIA) were investigated based on the strategic location of the hospitals. The study design was a descriptive cross-sectional study. Three hundred clinical samples were collected from male and female in and out-patients of all ages and processed using standard bacteriological methods. Detection of Staphylococcus aureus and MRSA strains were done according to standard protocols while antibiotic susceptibility testing of MRSA isolates was conducted using Kirby-Bauer disc diffusion method and interpreted following the CLSI 2021 guidelines. Results: The prevalence of MRSA strains in this study was 42.9%. Majority of patients with MRSA were from UUTH (44%) closely followed by patients from GHIA (40%). High antibiotics resistant rates of MRSA were recorded for ampicillin (96.6%), ciprofloxacin (73.3%), erythromycin (63.3%) and cotrimoxazole (60%). Gentamicin and ceftriaxone sensitivity rates were 53.3% and 63.4%, respectively. Conclusion: Health facilities in the state should institute effective antimicrobial stewardship, intensify surveillance and screening of Staphylococcus aureus for MRSA strains to guard against dissemination of multidrug resistant strains in both hospital and community settings because of the clinical implications.

Kinship analysis of mecA gene of methicillin-resistant Staphylococcus aureus isolated from milk and risk factors from the farmers in Blitar, Indonesia.

There are numerous reports of subclinical mastitis cases in Blitar, which is consistent with the region's high milk production and dairy cattle population. Staphylococcus aureus, which is often the cause of mastitis cases, is widely known because of its multidrug-resistant properties and resistance to β-lactam antibiotic class, especially the methicillin-resistant S. aureus (MRSA) strains. This study aimed to molecular detection and sequence analysis of the mecA gene in milk and farmer's hand swabs to show that dairy cattle are reservoirs of MRSA strains. A total of 113 milk samples and 39 farmers' hand swab samples were collected from a dairy farm for the isolation of S. aureus using Mannitol salt agar. The recovered isolates were further characterized using standard microbiological techniques. Isolates confirmed as S. aureus were tested for sensitivity to antibiotics. Oxacillin Resistance Screening Agar Base testing was used to confirm the presence of MRSA, whereas the mecA gene was detected by polymerase chain reaction and sequencing. A total of 101 samples were confirmed to be S. aureus. There were 2 S. aureus isolates that were multidrug-resistant and 14 S. aureus isolates that were MRSA. The mecA gene was detected in 4/14 (28.6%) phenotypically identified MRSA isolates. Kinship analysis showed identical results between mecA from milk and farmers' hand swabs. No visible nucleotide variation was observed in the two mecA sequences of isolates from Blitar, East Java. The spread of MRSA is a serious problem because the risk of zoonotic transmission can occur not only to people who are close to livestock in the workplace, such as dairy farm workers but also to the wider community through the food chain.

Methicillin-resistant staphylococci in clinical bovine mastitis: occurrence, molecular analysis, and biofilm production.

Staphylococcus aureus is an important pathogen that causes mastitis in cattle, and the emergence of methicillin-resistant S. aureus (MRSA) poses a threat to veterinary and human medicine. The aims of the study were to investigate the prevalence of MRSA and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) isolated from clinical mastitis, their ability to form biofilms, and the antimicrobial susceptibility of S. aureus strains. In addition, the Staphylococcal Cassette Chromosome mec (SCCmec) type, spa type and the presence of Panton-Valentine Leucocidin in MRSA were evaluated. A total of 326 staphylococcal strains were screened by multiplex-PCR for S. aureus and Staphylococcus intermedius group (SIG) identification. The S. aureus strains (n = 163) were subjected to phenotypic testing for antimicrobial susceptibility and biofilm formation. Molecular analysis was performed on MRSA mecA-positive strains. Of 163 S. aureus isolates, 142 strains (87.1%) were resistant to at least one antibiotic, and all 19 MRSA strains were resistant to at least four out of five antibiotics tested. All S. aureus strains harboured the icaA gene and were biofilm producers. Nineteen MR-CoNS strains were also isolated. The most prevalent spa types among MRSA were t001 (57.9%) and t037 (31.6%), while one MRSA was type t008 and one was type t041. Most MRSA were SCCmec type I (63.2%) and III (31.6%) and only one strain was type IV. None of the MRSA isolates had the PVL gene. The prevalence of multidrug-resistant S. aureus in bovine mastitis is a serious concern. The finding of MRSA with spa types predominant in humans and infrequent in Italian cows and with SCCmec infrequently found in bovine milk or cheese suggest a human origin of these strains. The ability of MRSA and MR-CoNS involved in bovine mastitis to be transferred to humans and vice versa poses a public health concern.

Molecular and Clinical Features of Heterogeneous Vancomycin-Intermediate Staphylococcus aureus in Tertiary Care Hospitals in South India

Objectives: This study aimed to detect heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) among methicillin-resistant S. aureus (MRSA) isolated from healthcare-associated infections and identify staphylococcal cassette chromosome mec (SCCmec) types. Methods: This study was conducted from February 2019 to March 2020 and included patients admitted in 4 tertiary care hospitals in Karnataka, India. Isolation and identification of MRSA were done using standard bacteriological methods. Antimicrobial susceptibility testing was done using Kirby–Bauer disc diffusion; macrolide-lincosamide-streptogramin B phenotypes were identified using the D test. The minimum inhibitory concentration (MIC) of vancomycin was determined using agar dilution. hVISA were confirmed by the modified population analysis profile-area under the curve test. SCCmec types and the Panton- Valentine leukocidin (pvl) gene were detected using multiplex polymerase chain reaction. Results: Of 220 MRSA stains, 14 (6.4%) were hVISA. None of the MRSA isolates was vancomycin-intermediate or -resistant and all hVISA were susceptible to linezolid and teicoplanin. The macrolide-streptogramin B phenotype was present in 42.9% of hVISA; 92.9% of the hVISA strains had vancomycin MIC in the range of 1–2 μg/mL. Majority of the hVISA and vancomycin-susceptible MRSA were isolated from patients with skin and soft tissue infections. SCCmec III and IV were present in 50% and 35.7% of hVISA, respectively; 14.3% of the hVISA harboured SCCmec V. Conclusion: The prevalence rate of hVISA among MRSA was 6.4%. Therefore, MRSA strains should be tested for hVISA before starting vancomycin treatment. None of the isolates was vancomycin-intermediate or -resistant and all the hVISA strains were susceptible to linezolid and teicoplanin. The majority of the hVISA were isolated from patients with skin and soft tissue infections and harboured SCCmec III and IV. Keywords: MRSA; Hospital Infection; Molecular Typing; Vancomycin; India.

Importance of Toxin Genes and Polymerase Chain Reaction-Based Open Reading Frame Type Analyses for Severe Staphylococcus aureus Infection in Children.

This study analyzed 26 Staphylococcus aureus strains, including 16 methicillin-resistant S. aureus (MRSA) and 10 methicillin-susceptible S. aureus (MSSA), collected from eight medical institutions in the Chiba Prefecture that requested a toxin gene analysis between 2015 and 2021. A total of 14 Panton-Valentine leukocidin (PVL) positive strains were identified, including MSSA. PVL-positive strains were classified into seven types according to polymerase chain reaction-based open reading frame typing (POT); of these types, three POT MRSA strains have not been previously reported, and one has been previously reported as PVL-negative. Some strains tested positive for both PVL and toxic shock syndrome toxin 1. One POT type was identified in both PVL-positive and PVL-negative strains. To the best of our knowledge, this is the first report on the regional spread of highly pathogenic S. aureus strains based on the POT method in children from multiple medical institutions. This method is useful for estimating the spread of toxin gene-carrying strains in the community owing to its association with toxin genes. As the number of PVL-positive strains in Japan increases, it is important to analyze the isolates of severe S. aureus infections in children by combining toxin gene analyses with the POT method.

Phytochemical, cytotoxic, antileishmania and antimicrobial potentials of Rhodes grass (Chloris gayana Kunth)

The present study aimed to analyze the cytotoxic and antimicrobial activity of the plant Chloris gayana Kunth (Poaceae) proceeding from the ethanol extract, taking into consideration its major secondary metabolites, such as alkaloids, triterpenes, steroids, flavonoids, and tannins. The ethanol extract showed no antimicrobial activity against Staphylococcus aureus, Escherichia coli and Candida krusei. However, the ethanol extract was able to potentiate the activity of amikacin against a strain of S. aureus MRSA (methicillin resistant S. aureus), suggesting a possible application of the extract itself or its isolated phytochemicals, as adjuvants of amikacin in the treatment of infections caused by MRSA strains resistant to this antibiotic. Potential antileishmanial activity was observed, but further research on the isolated action of these metabolites is needed.

Targeting Dalbavancin Inoculum Effect: Adjunctive Single Dose of Daptomycin.

Daptomycin (DAP) has proven to be a viable alternative amid vancomycin resistance; however, the use of DAP post vancomycin treatment has led to the development of DAP non-susceptible (DNS) strains. Dalbavancin (DAL), a novel single-dosed lipoglycopeptide, has shown enhanced activity against highly resistant Staphylococcus aureus strains. However, on the basis of previous reports and our observations, DAL does not demonstrate similar activity at high versus low inoculum levels. Therefore, we hypothesized that addition of DAP even at minimal concentrations (single dose on day1) will lower the inoculum to the level that can be cleared by dalbavancin. Isolates from methicillin-resistant S.aureus (MRSA)-infected patients with varying susceptibility profiles were evaluated using broth microdilution methods. Two DNS-VISA strains (vancomycin intermediate resistant S.aureus) and one MRSA strain were further evaluated in a one-compartment PK/PD model using a high starting initial inoculum of 109CFU/mL as well as low initial inoculum of 107CFU/mL over 168h to assess the activity of DAL and DAP monotherapy and in combination. Single therapies were not bactericidal when evaluated in the 168h in vitro one-compartment model with an initial inoculum of 109; however, the combination of DAL plus single dose of DAP resulted in enhanced killing at the end of the 168-h exposure. DAL single therapy caused reduction in colony counts down to detection limit (2log10 CFU/ml) at a lower inoculum but did not show enhancement (< 2log10 CFU/ml) at higher initial inoculums (P < 0.01) for all three strains. Similarly, DAP caused initial bacterial reduction up to 4log10 CFU/ml with regrowth at about 32h of exposure, which stayed at initial inoculum levels for the duration of the model for all three strains. Dalbavancin inoculum effect is a major issue in bacterial infections with high bacterial loads and the combination of DAL plus single dose of DAP showed promise in eradicating resistant S.aureus strains at high inoculums.

Accessory gene regulators and virulence genes associated with the pathogenicity of Staphylococcus aureus from clinical and community settings in Lagos, Nigeria

Staphylococcus aureus is a prominent pathogen that causes serious community and hospital-acquired infections globally. Its pathogenicity is attributed to a variety of secreted and cell surface associated proteins that are modulated by the quorum-sensing accessory gene regulator (agr) system. In this study, we investigated the presence of toxin genes and agr involved with S. aureus from clinical samples and apparently healthy individuals. Unequivocal identification of the isolates was obtained with the Vitek 2 system. We screened 70 clinical (CL) and 22 community (C) S. aureus strains for the methicillin resistance (mecA) gene, agr and superantigens (SAg) (enterotoxins and toxic shock syndrome toxin-1) using PCR techniques. A total of 12 clinical isolates were classified as methicillin-resistant S. aureus (MRSA); 89 isolates belonged to one of the four agr groups (agr1-4), and 3 isolates were non-typeable. Of the agr groups, agr1 was the most prominent and mostly consisted of isolates from pus/wounds. The methicillin-susceptible S. aureus (MSSA) isolates were distributed within the four agr groups while MRSA strains were restricted to agr1 and agr3. The most common enterotoxin gene, sei, was likewise more prevalent in MSSA strains than in MRSA strains, where sea predominated. The co-existence of two or more enterotoxins was confirmed in 40% of the isolates. sea occurred through all the agr groups except agr3 and sei was not found in agr1 and agr4. The toxic shock toxin (tst) gene was detected in six MSSA. These findings suggest that MSSA may cause more lethal infections than MRSA because of the increased frequency of toxic genotypes seen in MSSA strains. Significance: Isolates in the agr1,3 groups had more SAg toxin genes, whereas isolates in the agr4 groups possessed more tst genes. The MSSA isolates contained higher proportions of virulence genes than MRSA. The clinical implications of this discovery include that MSSA may cause more lethal infections than MRSA due to the greater number of toxigenic genotypes discovered.

Identification of Potential Inhibitors for Beta-Lactamase in Methicillin- Resistant Staphylococcus aureus from Flavonoids Using a Computational Drug Discovery Approach

Background: Staphylococcus aureus (S. aureus) is a Gram-positive bacterium causing a wide range of human infections, leading to life-threatening invasive disorders, hospitalization, and mortality. Producing β-lactamase enzymes in S. aureus is one of the main mechanisms of the pathogen that makes the bacteria resistant to beta-lactam antibiotics, resulting in methicillin-resistant S. aureus (MRSA) strains. Therefore, it is crucial to identify novel β-lactamase inhibitors to combat infections caused by MRSA strains. Methods: In silico virtual screening approach was executed to evaluate the binding affinity of several natural flavonoids to the MRSA β-lactamase active site. After that, the stability of interactions between top inhibitors and the residues incorporated inside the β-lactamase was examined by molecular dynamics (MD) simulation. Moreover, the most connected amino acid within the catalytic domain of the enzyme was determined. Results: Rutin, isoquercitrin, nicotiflorin, quercetin-3-rhamnoside, vicenin-2, quercitrin, and orientin demonstrated a salient binding affinity with the β-lactamase active site (ΔG binding &lt; −10 kcal/mol). Interestingly, the inhibition constant value (Ki) for rutin was estimated at the picomolar scale. The docked poses of these compounds were demonstrated to be stable. Moreover, Gln237 was revealed to be the most crucial residue involved in ligand binding. Conclusion: Rutin, isoquercitrin, nicotiflorin, quercetin-3-rhamnoside, vicenin-2, quercitrin, and orientin may be potent inhibitors of β-lactamase and may be helpful for the treatment of several invasive infections caused by MRSA strains. However, experimental studies are needed in the future to validate our findings.

Characterization of Staphylococcus aureus and methicillin‐resistant S. aureus from yak

AbstractStaphylococcus aureus, particularly methicillin‐resistant S. aureus (MRSA), is an important zoonotic pathogen which not only causes significant economic loss in livestock production but also emerges as a potential threat to public health. Compared with bovines, the information on the colonization of S. aureus and MRSA in yaks, the only bovine species providing meat and other necessities for Tibetans living at high altitude, is very limited. Therefore, in the current study, S. aureus and MRSA prevalence, virulence genes, and antibiotic and antiseptic resistance properties in yaks from 18 counties of Ganzi Prefecture, Sichuan province, China were investigated. The results revealed that the overall prevalence of S. aureus during yak breeding was 7.10% among 1281 samples (91/1281), containing 9.44% from nasal (62/657) and 4.65% from anus (29/624). Nearly all of the S. aureus isolates carried at least one staphylococcal enterotoxin (SE) gene and the predominant enterotoxin gene was selx (51.65%). In addition, virulence genes (hlα, hlβ, pvl, and tsst‐1), antiseptic resistance genes (qacA/B, qacC, and qacG), and heavy metal resistance genes (copA, arsB, cadD, and arsA) were also found. Furthermore, 24 MRSA strains were identified. SCCmec, spa, and multilocus sequence typing typing revealed that the predominant types of MRSA were ST59‐IVa‐t437 and ST59‐III‐t437. It was noteworthy that all these methicillin‐resistant strains were resistant to two or more antibiotics and possessed virulence genes. The minimal inhibitory concentration (MIC) values of antiseptic peroxyacetic acid, sodium hypochlorite, and benzalkonium bromide against these MRSA strains were measured and the MIC values of benzalkonium bromide (1.22–9.77 μg/mL) were relatively low. Furthermore, the challenge with 1/4 MIC of oxacillin sodium or ofloxacin or benzalkonium bromide for 216 h increased the resistance of the MRSA strain YB786 to these antibiotics but decreased the MIC value of benzalkonium bromide. The results provide an indication of the health risks associated with these S. aureus strains, especially methicillin‐resistant strains from yaks and new approaches are needed to treat these strains.

Molecular detection of SPA-type of methicillin-resistant Staphylococcus aureus from Urinary Tract Infection patient in Wasit Province, Iraq

Abstract Background: Staphylococcus aureus, a commonly occurring pathogen, is associated with severe diseases both in community and hospital settings and has been a significant concern for public health. Methicillin-resistant S. aureus (MRSA) infections have become widespread in many regions worldwide. Objective: The objective of their study was to employ polymerase chain reaction to identify certain virulence genes and determine the antibiotic susceptibility profiles of S. aureus strains. Materials and Methods: Initially, the identification of these isolates involved culture, microscopic examination, and biochemical tests. S. aureus accounted for 36.4% of the growth observed. Results: The findings of antibiotic susceptibility testing for MRSA S. aureus indicated the highest resistance rates to cefoxitin and amoxicillin-clavulanic acid, followed by clindamycin and tetracycline. On the other hand, S. aureus showed maximum sensitivity to gentamicin and nitrofurantoin. It was suggested that Imipenem and nitrofurantoin exhibited the least antibiotic resistance in urinary tract infection patients. The DNA was extracted from the isolates, and the purity of the nucleic acid samples ranged from 1.8 to 2.0, while the concentration varied from 50 to 360 mg/μL. Molecular analysis of the genes showed that 33.3% of the isolates possessed the icaD gene, whereas none of the MRSA strains exhibited the presence of the icaA gene. Conclusion: The study findings indicate a relatively high prevalence of MRSA strains among S. aureus isolates in hospitals located in Wasit Province. Moreover, a significant proportion of these MRSA strains exhibit robust biofilm production capabilities.

Reduction of methicillin-resistant Staphylococcus aureus biofilm growth and development using arctic berry extracts.

Surgical site infection remains a devastating and feared complication of surgery caused mainly by Staphylococcus aureus (S. aureus). More specifically, methicillin-resistant S. aureus (MRSA) infection poses a serious threat to global health. Therefore, developing new antibacterial agents to address drug resistance are urgently needed. Compounds derived from natural berries have shown a strong antimicrobial potential. This study aimed to evaluate the effect of various extracts from two arctic berries, cloudberry (Rubus chamaemorus) and raspberry (Rubus idaeus), on the development of an MRSA biofilm and as treatment on a mature MRSA biofilm. Furthermore, we evaluated the ability of two cloudberry seed-coat fractions, hydrothermal extract and ethanol extract, and the wet-milled hydrothermal extract of a raspberry press cake to inhibit and treat biofilm development in a wound-like medium. To do so, we used a model strain and two clinical strains isolated from infected patients. All berry extracts prevented biofilm development of the three MRSA strains, except the raspberry press cake hydrothermal extract, which produced a diminished anti-staphylococcal effect. The studied arctic berry extracts can be used as a treatment for a mature MRSA biofilm, however some limitations in their use exist.

Population structure of food-borne Staphylococcus aureus in China

Objective: To understand the population structure of food-borne Staphylococcus (S.) aureus in China. Methods: Whole genome sequencing was used to analyze 763 food-borne S. aureus strains from 16 provinces in China from 2006 to 2020. Multilocus sequence typing (MLST), staphylococcal protein A gene (spa) typing, and staphylococcal chromosome cassettemec (SCCmec) typing were conducted, and minimum spanning tree based on ST types (STs) was constructed by BioNumerics 7.5 software. Thirty-one S. aureus strains isolated from imported food products were also included in constructing the genome phylogenetic tree. Results: A total of 90 STs (20 novel types) and 160 spa types were detected in the 763 S. aureus isolates. The 72 STs (72/90, 80.0%) were related to 22 clone complexes. The predominant clone complexes were CC7, CC1, CC5, CC398, CC188, CC59, CC6, CC88, CC15, and CC25, accounting for 82.44% (629/763) of the total. The STs and spa types in the predominant clone complexes changed over the years. The methicillin-resistant S. aureus (MRSA) detection rate was 7.60%, and 7 SCCmec types were identified. The ST59-t437-Ⅳa (17.24%, 10/58), ST239-t030-Ⅲ (12.07%, 7/58), ST59-t437-Ⅴb (8.62%, 5/58), ST338-t437-Ⅴb (6.90%, 4/58) and ST338-t441-Ⅴb (6.90%, 4/58) were the main types in MRSA strains. The genome phylogenetic tree had two clades, and the strains with the same CC, ST, and spa types clustered together. All CC7 methicillin sensitive S. aureus strains were included in Clade1, while 21 clone complexes and all MRSA strains were in Clade2. The MRSA strains clustered according to the SCCmec and STs. The strains from imported food products in CC398, CC7, CC30, CC12, and CC188 had far distances from Chinese strains in the tree. Conclusions: In this study, the predominant clone complexes of food-borne strains were CC7, CC1, CC5, CC398, CC188, CC59, CC6, CC88, CC15, and CC25, which overlapped with the previously reported clone complexes of hospital and community-associated strains in China, suggesting that close attention needs to be paid to food, a vehicle of pathogen transmission in community and food poisoning.

The Occurrence of Methicillin-Resistant Staphylococcus Aureus (MRSA) Around the World and Antibiotic Therapy for Selected Infections Caused By MRSA

Abstract Staphylococcus aureus is a Gram-positive bacterium, which can cause serious bacterial infections in humans. It constitutes an important etiological factor of many diseases, for instance, soft tissue and skin infections (including skin boils and abscesses), as well as life-threatening necrotizing pneumonia or toxic shock syndrome. It is estimated that about 25–30% of people are carriers of S. aureus mainly in the anterior nostrils. A smaller percentage of people are carriers of methicillin-resistant S. aureus (MRSA). In accordance with its definition, methicillin-resistant S. aureus is resistant to almost all β-lactam antibiotics. This phenomenon is mainly caused by the presence of penicillin-binding protein in the cell wall – PBP2a, which is the product of the mecA gene, which is part of the complex called SCCmec (staphylococcal cassette chromosome mec). Methicillin-resistant S. aureus (MRSA) results in endemic in hospitals around the world and are one of the leading causes of morbidity and mortality in society. Infections initiated by hospital strains of MRSA (health care-associated MRSA, HA-MRSA) concern mainly immunocompromised patients after surgery. In addition, there are populations of acommunity-associated MRSA (CA-MRSA) strains and populations of livestock-associated MRSA (LA-MRSA) strains. The treatment of infections with MRSA etiology, after exhausting the possibilities of standard antibiotic therapy with the use of i.e. vancomycin, is based on treatment with new-generation antibiotics, such as dalbavacin.

Molecular Characteristics of Staphylococcus aureus Strains to Carry Panton-Valentine Leukocidin Genes Isolated from Hospitalized Patients in Tehran, Iran

Background: Staphylococcus aureus with concurrent resistance to antibacterial agents is emerging globally. This emergence might be due to the production of different virulence determinants, notably Panton-Valentine leukocidin (PVL). Objectives: This study aimed to investigate the genetic characteristics of PVL-positive S. aureus strains isolates from clinical samples. Methods: An epidemiological study was conducted on 65 S. aureus isolates carrying pvl genes. An antibiogram test by the disk diffusion and broth microdilution methods was conducted to assess antimicrobial resistance profiles. Results: All detected methicillin-resistant S. aureus (MRSA) isolates were confirmed by mecA polymerase chain reaction (PCR) assays. The PVL-positive isolates were characterized using multiplex PCR assay to detect staphylococcal cassette chromosome mec (SCCmec) and agr types. The PVL frequency was 19.5% and 17.6% in MRSA and methicillin-susceptible S. aureus (MSSA), respectively. Among the PVL-positive isolates, 66.2% and 33.8% were MRSA and MSSA, respectively. Multidrug resistance amounted to 84.6% of the isolates (MRSA: 61.5%, MSSA: 23.1%). Staphylococcal cassette chromosome mec III was dominated (55.8%; 24/43). The most commonly identified agr was type III (53.8%; 35/65). Resistance to vancomycin amounted to 12.3% of the isolates, and all belonged to agr type III and SCCmec type III. The frequency of inducible and constitutive clindamycin resistance among PVL-positive MRSA strains (12.3% and 26.1%) was higher than PVL-positive MSSA strains (7.7% and 15.4%). Most constitutive and inducible clindamycin resistance isolates belonged to agr type III (26.2% and 18.5%) and SCCmec type III (each 27.9%). In the present study, 32.3% of the isolates were confirmed as mupirocin resistant, and all were MRSA, 9 (42.9%) and 12 (57.1%) isolates of which exhibited high-level mupirocin resistant (HLMUPR) and low-level mupirocin resistant phenotypes. All HLMUPR MRSA isolates belonged to SCCmec III and recovered from wound samples. Conclusions: The emergence of vancomycin-resistant S. aureus strains among PVL-positive S. aureus strains in Iran is a serious alarm and seems to be becoming the greatest concern in the treatment of staphylococcal infections in the healthcare setting. The present study reinforces plausible direct transfers between community and nosocomial PVL-positive S. aureus types.

Comparing the Synergistic and Antagonistic Interactions of Ciprofloxacin and Levofloxacin Combined with Rifampin against Drug-Resistant Staphylococcus aureus: A Time-Kill Assay.

Treatment of device-related infections by drug-resistant Staphylococcus aureus can be challenging, and combination therapy has been proposed as a potential solution. We compared the effectiveness of levofloxacin-rifampin and ciprofloxacin-rifampin combinations in killing methicillin-resistant S. aureus (MRSA) using a time-kill assay. We randomly selected 15 vancomycin-susceptible S. aureus (VSSA) strains, 3 vancomycin-intermediate S. aureus (VISA) strains, and 12 heterogeneous VISA (hVISA) strains from the Asian Bacterial Bank. Time-kill experiments were performed in duplicate for each isolate. Viable bacterial counts were determined at 0 h, 4 h, 8 h, and 24 h for the ciprofloxacin- and levofloxacin-rifampin combinations at 1× MIC and 0.5× MIC. We compared synergistic and antagonistic interactions between the two combinations. The viable bacterial count significantly decreased after 24 h of exposure to ciprofloxacin-rifampin and levofloxacin-rifampin combinations, with synergy observed more frequently in isolates exposed to ciprofloxacin-rifampin (43.3%) than levofloxacin-rifampin (20.0%) (p = 0.0082). The synergistic interactions of both combinations were more frequently observed in resistant strains with high MICs of ciprofloxacin (≥16 mg/L) and levofloxacin (≥8 mg/L). Levofloxacin tended to exhibit more frequent antagonistic interactions with rifampin than ciprofloxacin, although there was no statistical difference in antagonism between the two combinations. Our study demonstrated that ciprofloxacin exhibits superior synergistic activity against MRSA strains, including VISA/hVISA, when combined with rifampin compared with levofloxacin. High MICs of fluoroquinolones were found to predict synergism. Our results suggest that ciprofloxacin may be a more effective choice than levofloxacin for combination therapy with rifampin in the treatment of MRSA infections.

Synthesis, characterization, and antibacterial activities of a heteroscorpionate derivative platinum complex against methicillin-resistant Staphylococcus aureus.

Staphylococcus aureus is one of the species with the greatest clinical importance and greatest impact on public health. In fact, methicillin-resistant S. aureus (MRSA) is considered a pandemic pathogen, being essential to develop effective medicines and combat its rapid spread. This study aimed to foster the translation of clinical research outcomes based on metallodrugs into clinical practice for the treatment of MRSA. Bearing in mind the promising anti-Gram-positive effect of the heteroscorpionate ligand 1,1'-(2-(4-isopropylphenyl)ethane-1,1-diyl)bis(3,5-dimethyl-1H-pyrazole) (2P), we propose the coordination of this compound to platinum as a clinical strategy with the ultimate aim of overcoming resistance in the treatment of MRSA. Therefore, the novel metallodrug 2P-Pt were synthetized, fully characterized and its antibacterial effect against the planktonic and biofilm state of S. aureus evaluated. In this sense, three different strains of S. aureus were studied, one collection strain of S. aureus sensitive to methicillin and two clinical MRSA strains. To appraise the antibacterial activity, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), minimum biofilm inhibitory concentration (MBIC), and minimum biofilm eradication concentration (MBEC) were determined. Moreover, successful outcomes on the development of biofilm in a wound-like medium were obtained. The mechanism of action for 2P-Pt was proposed by measuring the MIC and MBC with EDTA (cation mediated mechanism) and DMSO (exogenous oxidative stress mechanism). Moreover, to shed light on the plausible antistaphylococcal mechanism of this novel platinum agent, additional experiments using transmission electron microscopy were carried out. 2P-Pt inhibited the growth and eradicated the three strains evaluated in the planktonic state. Another point worth stressing is the inhibition in the growth of MRSA biofilm even in a wounded medium. The results of this work support this novel agent as a promising therapeutic alternative for preventing infections caused by MRSA.

Molecular Characteristics of Staphylococcus aureus Strains Isolated from Nasal Cavity and Wound Infections Among Diabetic Patients.

Staphylococcus aureus is the most common pathogen contributing to diabetic foot infections (DFI). Nasal transmission of S. aureus potentially increases the risk of endogenous infection. The aim of this study was to determine the genetic diversity and antibiotic resistance profile of S. aureus isolates in nasal and wound samples from diabetic patients. A cross-sectional study was conducted from July 2018 to September 2019. S. aureus was isolated from the anterior nares and wounds of diabetic patients. All S. aureus isolates were characterized by detection of resistance and virulence genes (mecA, ermA, ermC, hla, hlb, hlg, sea, lukDE, pvl), staphylococcal cassette chromosome mec (SCCmec)-typing and staphylococcal protein A (spa)-typing. A total of 34 S. aureus were isolated from the wounds of 115 diabetic patients with DFI. Twenty-four S. aureus isolates were collected from the anterior nares of patients, and thirteen patients had concurrent S. aureus in nasal and wound specimens. The prevalence of methicillin-resistant S. aureus (MRSA) in nasal specimens was noticeable (41.7%), and the most common spa-type in nasal and wound specimens was t14870. Nearly half of the patients with concurrent S. aureus in wound and nasal specimens had similar isolates from both sites. Our data suggest that detection and screening of S. aureus colonization in the nasal cavity may prevent subsequent endogenous infections, particularly with MRSA strains.

Vernonia polyanthes Less. (Asteraceae Bercht. & Presl), a Natural Source of Bioactive Compounds with Antibiotic Effect against Multidrug-Resistant Staphylococcus aureus.

Vernonia polyanthes is a medicinal plant used to treat many disorders, including infectious diseases. This study investigated the chemical constituents and the antibacterial activity of V. polyanthes leaf rinse extract (Vp-LRE). The chemical characterization of Vp-LRE was established using ultra-high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS), and glaucolide A was identified through 1H and 13C nuclear magnetic resonance (NMR) and mass fragmentation. The cytotoxicity was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). The antibacterial activity was assessed by minimal inhibitory concentration and minimal bactericidal concentration. Interactions between ligands and beta-lactamase were evaluated via molecular docking. UHPLC/Q-TOF-MS detected acacetin, apigenin, chrysoeriol, isorhamnetin, isorhamnetin isomer, kaempferide, 3',4'-dimethoxyluteolin, 3,7-dimethoxy-5,3',4'-trihydroxyflavone, piptocarphin A and glaucolide A. Vp-LRE (30 µg/mL) and glaucolide A (10 and 20 μg/mL) were cytotoxic against RAW 264.7 cells. Glaucolide A was not active, but Vp-LRE inhibited the Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Escherichia coli, Salmonella Choleraesuis and Typhimurium, with a bacteriostatic effect. The compounds (glaucolide A, 3',4'-dimethoxyluteolin, acacetin and apigenin) were able to interact with beta-lactamase, mainly through hydrogen bonding, with free energy between -6.2 to -7.5 kcal/mol. These results indicate that V. polyanthes is a potential natural source of phytochemicals with a significant antibiotic effect against MRSA strains.

Investigation of nasal Staphylococcus aureus carriage by real-time PCR in patients receiving hemodialysis treatment

Objectives: Staphylococcus aureus, coagulase-negative staphylococci (CoNS), and methicillin-resistant S. aureus (MRSA), which are significant nosocomial pathogens, have become a growing global problem because their carriage and diseases have become resistant to many antibiotics. This study aimed to investigate and determine the rate of MRSA carriage among patients receiving hemodialysis treatment using molecular methods. Methods: In the 254 hemodialysis patients, the nasal carriage rates, susceptibility and resistance to S. aureus, CoNS and MRSA were examined using culture and real-time PCR methods. Nasal samples from hemodialysis patients were examined using real-time PCR. Microscopic examination was performed using the Gram staining method, and S. aureus was identified using catalase and coagulase. The strains were then tested for antibiotic susceptibility. Staphylococci was isolated from 231 of the 254 patients. Results: S. aureus carriage was detected in 50 patients, MRSA in 16, methicillin-susceptible S. aureus (MSSA) in 33, CoNS in 66, methicillin-resistant CoNS (MR-CoNS) in 38, and methicillin-susceptible CoNS (MS-CoNS) in 28. S. aureus and MRSA strains exhibited 100% susceptibility to nitrofurantoin, and vancomycin. MSSA strains showed the highest susceptibility to chloramphenicol, clindamycin (84.8%), and co-trimoxazole (36.4%). CoNS showed 100% susceptibility to vancomycin, and 16.7% susceptibility to ampicillin. Vancomycin was found to be the most effective antibiotic against S. aureus, CoNS, and MRSA pathogens identified in patients undergoing hemodialysis, whereas penicillin resistance was found. Conclusions: It can be concluded that one of the most effective ways to prevent the formation of antibiotic resistant strains is the hygiene of the hospital and hospital staff. Real-time PCR is very important for analyzing with high sensitivity.