Genetic characterization of a vancomycin-resistant Staphylococcus aureus isolate from the respiratory tract of a patient in a university hospital in northeastern Iran

Phenotypic and genotypic characterization of Staphylococcus aureus strains isolated from otitis externa: Emergence of CC30-spa t019-SCCmec IV carrying PVL as major genotype

The increasing emergence of Staphylococcus aureus as the primary causative agent of otitis externa has been noted; however, detailed information regarding the molecular characteristics of these strains in Iran remains scarce. The current study aims to investigate both genotypic and phenotypic attributes of S. aureus strains implicated in ear infections. In the present work, we analyzed 60 S. aureus strains isolated from cases of otitis externa over a period of 45 months. The resistance patterns were determined using disk diffusion and microbroth dilution methods. All S. aureus isolates were confirmed by the nucA polymerase chain reaction assay, and their biofilm production was assessed by a microtiter plate assay. Molecular characterization of the isolates was performed using the staphylococcal cassette chromosome mec, multilocus sequence typing, and staphylococcus protein A typing methods. Overall, the results indicated that 44 out of 60 S. aureus isolates (73.3 %) were methicillin-resistant Staphylococcus aureus. Resistance to mupirocin and vancomycin was observed in 13.3 % and 1.7 % of the tested isolates, respectively. Furthermore, out of the 60 S. aureus isolates, 56 strains (93.4 %) were classified as positive biofilm strains at different levels. Twelve distinct clonal lineages were identified. The vast majority of S. aureus isolates belonged to CC30/ST30-MRSA IV/t019 (41.7 %). Among the 31 strong biofilm producers, the majority (64.5 %) belonged to CC30/ST30-MRSA IV/t019 clone. Biofilm negative isolates belonged to CC22/ST22 (2 isolates), CC8/ST585 (one isolate), and CC8/ST8 (one isolate). Our result revealed that about three-quarters of PVL-positive strains belonged to CC30/ST30. Our data confirmed the presence of MSSA strains among CC30/ST30 and CC22/ST22 isolates. The mupirocin resistant isolates (n = 8) belonged to CC8/ST585-MRSA III/t713 (37.5 %), CC8/ST239-MRSA III/t030 (25 %), CC8/ST8-MRSA IV/t008 (12.5 %), CC8/ST239-MRSA III/t037 (12.5 %), and CC22/ST22-MRSA IV/t790 (12.5 %) lineages. The VRSA strain belonged to the CC8/ST8-MRSA IV/t008 lineage, carrying the vanA determinant. iMLSB phenotypes (n = 14) were distributed across different lineages, including CC30/ST30-MRSA IV/t019 (21.5 %), CC30/ST30-MSSA/t021 (21.5 %), CC22/ST22-MSSA/t005 (14.3 %), CC8/ST239-MRSA III/t030 (14.3 %), CC22/ST22-MSSA/t1869 (7.1 %), CC22/ST22-MRSA IV/t790 (7.1 %), CC8/ST239-MRSA III/t037 (7.1 %), and CC1/ST772-MRSA IV/t10795 (7.1 %). These findings highlight significant genotypic diversity and high biofilm formation among our isolates. The frequent occurrence of the CC/ST30 clone in S. aureus strains isolated from otitis externa reflects the emergence of these lineages as a predominant clone in Iran, posing a significant public health concern.

Antimicrobial resistance markers distribution in Staphylococcus aureus from Nsukka, Nigeria

BACKGROUND

Multidrug resistance in Staphylococcus aureus continues to influence treatment complications in clinical settings globally. Multidrug-resistant-S. aureus (MDR-SA) is often genetically driven by resistance markers transferable in pathogenic strains. This study aimed to determine the distribution of resistance markers in clinical isolates of S. aureus in Nsukka, Nigeria.

METHODS

A total of 154 clinical samples were cultured on mannitol salt agar. Isolates were characterized using conventional cultural techniques and confirmed by PCR detection of S. aureus-specific nuc gene. Antibiotic resistance profiles of the isolates were determined against selected antibiotics using the disk-diffusion method, while screening for antibiotic resistance genes (Mec A, Erm A, Erm B, Erm C, Van A, and Van B) was by PCR.

RESULTS

A total of 98 isolates were identified as S. aureus by conventional methods. Of these, 70 (71.43%) were confirmed by PCR. Phenotypically, the isolates exhibited high degrees of resistance to oxacillin (95.72%), erythromycin (81.63%), and ertapenem (78.57%) and 75.51% and 47.30% against methicillin and vancomycin, respectively. Multiple antibiotic resistance indexes of the isolates ranged from 0.3 to 1, and the most prevalent pattern of resistance was oxacillin-ertapenem-vancomycin-erythromycin-azithromycin-clarithromycin-ciprofloxacin- cefoxitin-amoxicillin-clavulanic acid. PCR screening confirmed the existence of various antibiotic resistance makers among the strains, with the most common resistance genes found in the isolates being Mec A (32.14%), Van A (21.43%), Van B (10.71%), Erm B (10.71%), and Erm C (17.86%). None possessed the Erm A gene.

CONCLUSION

The study supports the need for necessary action, including rational drug use, continuous surveillance, and deployment of adequate preventive and curative policies and actions.

Potential of Natural Phenolic Compounds as Antimicrobial Agents against Multidrug-Resistant Staphylococcus aureus in Chicken Meat

Staphylococcus aureus is one of the most widespread foodborne bacteria that cause high morbidity, mortality, and economic loss, primarily if foodborne diseases are caused by pathogenic and multidrug-resistant (MDR) strains. This study aimed to determine the prevalence of S. aureus in chicken meat in Egyptian markets. Thus, this study might be the first to assess the efficiency of different natural phenolic compounds as novel antibacterial agents against MDR S. aureus pathogens isolated from raw chicken meat in the Egyptian market. The incidence and quantification of pathogenic S. aureus were detected in retail raw chicken meat parts (breast, thigh, fillet, and giblets). In total, 73 out of 80 (91.3%) of the chicken meat parts were contaminated, with S. aureus as the only species isolated. Of the 192 identified S. aureus isolates, 143 were coagulase-positive S. aureus and 117 isolates were MDR (81.8%, 117/143). Twenty-two antibiotic resistance profile patterns were detected. One strain was randomly selected from each pattern to further analyze virulence and resistance genes. Extracted DNA was assessed for the presence of antibiotic-resistance genes, i.e., vancomycin-resistance (vanA), aminoglycosides-resistance (aacA-aphD), apramycin-resistance (apmA), and methicillin-resistance (mecA), penicillin-resistance (blaZ), and virulence genes staphylococcal enterotoxins (sea and seb), Panton-Valentine leucocidin (pvl), clumping factor A (clfA), and toxic shock syndrome toxin (tst). Clustering analyses revealed that six S. aureus strains harbored the most virulence and resistance genes. The activity of hydroquinone was significantly higher than thymol, carvacrol, eugenol, and protocatechuic acid. Therefore, phenolic compounds, particularly hydroquinone, could potentially alternate with conventional antibiotics against the pathogenic MDR S. aureus inhabiting raw chicken meat. Hence, this study indicates that urgent interventions are necessary to improve hygiene for safer meat in Egyptian markets. Moreover, hydroquinone could be a natural phenolic compound for inhibiting foodborne pathogens.

Hospital-Related Lineage of USA300 Methicillin-Resistant Staphylococcus aureus (MRSA) to Cause Bacteremia in Iran

Staphylococcus aureus is an important pathogen that causes bloodstream infections. This study is aimed at assessing the genotypic characteristics of S. aureus strains responsible for bloodstream infections. An epidemiological study was conducted using 85 S. aureus strains isolated from bloodstream infections. Susceptibility was tested using the broth microdilution method and disk diffusion. All detected methicillin-resistant S. aureus (MRSA) isolates were confirmed by mecA PCR assays. S. aureus isolated from bacteremia were characterized using SCCmec, spa, and multilocus sequence typing methods. The prevalence of S. aureus strains responsible for bloodstream infections was 38.8%. All isolates were MRSA. Multidrug resistance (MDR) was present in 84.7% of isolates. MRSA isolated categorized within six clonal complexes including CC8 (60%), CC22 (22.4%), CC5 (5.9%), CC30 (4.7%), CC45 (4.7%), and CC59 (2.3%). The main lineages found were USA300/CC8-MRSA-IV/t008 (41.2%), followed by ST22-SCCmecIV/t790 (9.4%), ST239-SCCmecIII/t037 (7.1%), ST22-SCCmecIV/t032 (7.1%), ST239-SCCmecIII/t631 (5.9%), ST239-SCCmecIII/t860 (5.9%), ST22-SCCmecIV/t852 (5.9%), ST5-SCCmecIV/t002 (4.7%), ST45-SCCmecIV/t038 (4.7%), ST30-SCCmecIV/t318 (4.7%), ST59-SCCmecIV/t437 (2.3%), and ST225-SCCmecII/t045 (1.1%). Resistance to vancomycin amounted to 5.9% of isolates that belonged to ST239-SCCmecIII/t037 (80%) and ST8-SCCmecIV/t008 (20%). The emergence of USA300 strains in bloodstream infections in our country is a serious alarm and highlights the significant invasion of this lineage into the healthcare system. MDR patterns among these strains appear to be becoming the biggest problem in healthcare treatment.

Vancomycin heteroresistance among methicillin-resistant clinical isolates S. haemolyticus, S. hominis, S. simulans, and S. warneri

Besides being an essential part of the skin microbiome, coagulase-negative staphylococci are the etiological factors of serious infections. The aim of the study was to evaluate the heteroresistance to vancomycin and the potential antimicrobial efficacy of teicoplanin and daptomycin against the multiresistant strains of S. haemolyticus, S. hominis, S. warneri, and S. simulans. The study covered 80 clinical coagulase-negative staphylococci. Teicoplanin, vancomycin, and daptomycin MICs for the tested strains were determined according to EUCAST recommendation. The vanA and vanB genes were searched. The brain heart infusion screen agar method detected vancomycin heteroresistance. The population analysis profile method and analysis of autolytic activity were applied for the strains growing on BHI containing 4 mg/L vancomycin. Seven S. haemolyticus, two S. hominis, and two S. warneri strains presented a heterogeneous resistance to vancomycin. Their subpopulations were able to grow on a medium containing 4-12 mg/L of vancomycin. Monitoring heteroresistance to peptide antibiotics, which are often the last resort in staphylococcal infections, is essential due to the severe crisis in antibiotic therapy and the lack of alternatives to treat infections with multiresistant strains. Our work highlights the selection of resistant strains and the need for more careful use of peptide antibiotics.

Molecular Basis of Methicillin and Vancomycin Resistance in Staphylococcus aureus from Cattle, Sheep Carcasses and Slaughterhouse Workers

Staphylococcus aureus (S. aureus) is a serious infection-causing pathogen in humans and animal. In particular, methicillin-resistant S. aureus (MRSA) is considered one of the major life-threatening pathogens due to its rapid resistance to several antibiotics in clinical practice. MRSA strains have recently been isolated in a number of animals utilized in food production processes, and these species are thought to be the important sources of the spread of infection and disease in both humans and animals. The main objective of the current study was to assess the prevalence of drug-resistant S. aureus, particularly vancomycin-resistant S. aureus (VRSA) and MRSA, by molecular methods. To address this issue, a total of three hundred samples (200 meat samples from cattle and sheep carcasses (100 of each), 50 hand swabs, and 50 stool samples from abattoir workers) were obtained from slaughterhouses in Egypt provinces. In total, 19% S. aureus was isolated by standard culture techniques, and the antibiotic resistance was confirmed genotypically by amplification nucA gen. Characteristic resistance genes were identified by PCR with incidence of 31.5%, 19.3%, 8.7%, and 7% for the mecA, VanA, ermA, and tet L genes, respectively, while the aac6-aph gene was not found in any of the isolates. In this study, the virulence genes responsible for S. aureus' resistance to antibiotics had the highest potential for infection or disease transmission to animal carcasses, slaughterhouse workers, and meat products.

Surveillance of osteoarticular infections caused by Staphylococcus aureus in a paediatric hospital in Mexico City

Staphylococcus aureus is the main aetiologic agent of osteoarticular infections (OAIs) in paediatric patients. The aim of this prospective unicenter study was to describe the phenotypic and genotypic characteristics of S. aureus isolates obtained from OAIs in paediatric patients admitted to tertiary care hospital. Through a surveillance program called OsteoCode, a multidisciplinary team was created and we identified 27 patients with OAIs caused by S. aureus from 2019 to 2021. The susceptibility profile, virulence factors, biofilm formation, pulsed-field gel electrophoresis (PFGE), clonal complex (CC) and sequence type (ST) were determined. In addition, the clinical characteristics and evolution of the patients presented six months after the diagnosis of OAIs were described. Ninety-two percent of the isolates were methicillin-sensitive S. aureus (MSSA). In methicillin-resistant S. aureus (MRSA), SCCmec-II and SCCmec-V were detected. The pvl gene was only observed in MSSA (18.5%) and was associated with highest fever (p=0.015), multiple localization (p=0.017), and soft tissue sites of infection beyond the bone (pyomyositis, pulmonary abscess) (p=0.017). Biofilm formation was detected in 55.6% of isolates. The most common CC were CC5 and CC30 which represent the most common linages for bone and joint infections worldwide. The isolates were distributed in different STs, and ST672 was predominant. MRSA were associated with a longer duration of intravenous treatment and a prolonged hospital stay (p=0.023). Recurrent infection occurred in five children and orthopaedic complications in 33.3% of patients. This is the first study that reflects the epidemiology of S. aureus in OAIs in paediatric patients in Mexico; a clear predominance of MSSA distributed in different STs was observed. Our findings highlight that a multidisciplinary team is required for the diagnosis and treatment of OAIs.

Prevalence and Antibiotic Resistance Pattern of Methicillin-Resistant Staphylococcus aureus Isolated from Iraqi Hospitals

Methicillin-resistant Staphylococcus aureus (MRSA) bacteria are often multi-drug resistant, resulting in a high rate of treatment failure. This study aimed to identify the antibiotics resistance profile and molecular characteristics of MRSA strains isolated from patients' samples, including skin, wounds, and burns, which are the most common infections, and collected from hospitals. The samples included 34 MRSA isolates gathered from January 2020 to September 2020. All isolates were tested using the Kirby-Bauer method to determine MRSA susceptibility against antibiotics using the minimum inhibitory concentration protocol and the E-test. The polymerase chain reaction was used for the detection of antibiotic resistance genes, including tetracycline, erythromycin, linezolid, gentamicin, rifampicin, ciprofloxacin, quinupristin-dalfopristin, clindamycin, and mecA. Staphylococcal Cassette Chromosome mec (SCCmec) was determined by multilocus sequence typing of all isolates; accordingly, the findings indicated that the sensitivity of linezolid, quinupristin-dalfopristin, rifampin, daptomycin, and vancomycin differed. Moreover, multidrug resistance of MRSA was shown to be more than 90% for penicillin and 91.1% for erythromycin. It was revealed that SCCmec III was resistant to at least four to five different antibiotics. ST585 (2.9%), ST240 (8.8%), ST45 (14.7%), ST22 (17.6%), and ST239 (higher rate) were the five sequence types found in STs (55.8%). Finally, it was indicated that the emergence of MRSA in these Iraqi hospitals highlighted further research to better understand how the infection might be effectively controlled.

High prevalence and expression of antiseptic resistance genes among infectious t037/ST239 methicillin-resistant Staphylococcus aureus (MRSA) strains in North Khorasan Province, Iran

OBJECTIVES

Staphylococcus aureus is an important infectious agent and the majority of methicillin-resistant S. aureus (MRSA) infections are of nosocomial origin. To define the level and distribution of antiseptic resistance among infectious S. aureus strains we studied MRSA and methicillin-susceptible S. aureus (MSSA) isolates collected from different infection sites in an assortment of patients.

MATERIALS AND METHODS

S. aureus isolates were investigated for in vitro susceptibility to antiseptic agents and detection of qacA/B, smr, vanA, and mecA genes.

RESULTS

Among the S. aureus isolates we studied, 25 and 41 were MRSA and MSSA, respectively. The mean of minimum inhibitory concentrations (MICs) for benzethonium chloride (BTC) among MRSA was statistically significantly higher than for MSSA (26 µg/ml versus 11.7 µg/ml, P=0.003) while there was no significant difference between MRSA and MSSA for benzalkonium chloride (BKC) and chlorhexidine digluconate (CHG). The qacA/B genes were carried in 68% of the MRSA and 58.2% of MSSA (P=0.601), while smr was carried in 39% of MRSA and 29.3% of MSSA strains (P=1.000). In 15 out of 25 cases, MRSA ST239 with spa types t037, t030, and t7688 was isolated from the infection site with 86.6% of them carrying a resistance gene (qacA/B or qacA/B + smr).

CONCLUSION

The frequent presence of antiseptic resistance genes and a consequently elevated MIC against antiseptics among ST239 MRSA emphasizes the importance of mandatorily monitoring MRSA for effective infection control.

Clonal Diversity and Epidemiological Characteristics of ST239-MRSA Strains

Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen associated with severe morbidity and mortality and poses a significant threat to public health worldwide. The genetic diversity based on sequence types of MRSA strains was illustrated in previous studies; meanwhile, the diversity along with the predominant sequence type, especially in Egypt, remains unknown. The purpose of the current study was to determine the diversity of the predominant MRSA clone ST239-MRSA (n = 50) isolated from different hosts and clinical samples and to illustrate the correlation between the resistance patterns, toxin genes, and the genetic background in Port-said and El-Sharkia Governorates, Egypt. The ST239-MRSA clone was analyzed by phenotypic antibiotyping and various genotypic assays comprising SCCmec, agr, spa, coa, and coa-RFLP in addition to toxin gene profiles. Most of the analyzed strains (40/50, 80%) were multidrug resistant (MDR), belonged to SCCmec-III, agr-I, and coa genotype I, and harbored sea and pvl genes. A negative correlation between the toxin gene profiles and antimicrobial resistance was recorded. Meanwhile, the correlation between the toxin gene profiles and the genetic background was not observed in this study. Although ST239-MRSA strains belonged to a single sequence type, they exhibited a high degree of phenotypic and genotypic diversity, indicating weak clonality and adaptability. With such diversity, it is assumed that these strains may have undergone different evolutionary processes during transmission events among and/or within a single host or tissue niche.

Molecular Confirmation of Vancomycin-Resistant Staphylococcus aureus with vanA Gene from a Hospital in Kathmandu

Staphylococcus aureus, a commensal on the skin and in the nasal cavity of humans, is one of the most serious cases of nosocomial infections. Moreover, methicillin-resistant S. aureus (MRSA) is a leading cause of morbidity and mortality worldwide. For the treatment of MRSA infections, vancomycin is considered as a drug of choice. However, the emergence of vancomycin resistance among MRSA isolates has been perceived as a formidable threat in therapeutic management. To estimate the rate of vancomycin-resistant S. aureus (VRSA) and to detect the vancomycin-resistant genes, namely, vanA and vanB, among the isolates, a hospital-based cross-sectional study was conducted from July to December 2018 in Annapurna Neurological Institute and Allied Science, Kathmandu, Nepal. S. aureus was isolated and identified from different clinical samples and processed for antibiotic susceptibility testing by the modified Kirby-Bauer disc diffusion method. The screening of MRSA was performed as per Clinical and Laboratory Standard Institute (CLSI) guidelines. VRSA was confirmed by the minimum inhibitory concentration (MIC) method by employing E-test strips. All the phenotypically confirmed VRSA were further processed to detect the vanA and vanB gene by using the conventional polymerase chain reaction (PCR) method. A total of 74 (20.3%) S. aureus were isolated, and the highest percentage of S. aureus was from the wound samples (36.5%). Of 74 S. aureus isolates, the highest number (89.2%) was resistant to penicillin, and on the other hand, linezolid was found to be an effective drug. Likewise, 45 (60.81%) were found to be MRSA, five (11.11%) were VRSA, and 93.2% of S. aureus isolates showed an MAR index greater than 0.2. Two VRSA isolates (40%) were positive for the vanA gene. The higher prevalence of MRSA and significant rate of VRSA in this study recommend routine surveillance for the MRSA and VRSA in hospital settings before empirical therapy.

Emergence of CC8/ST239- SCCmec III/t421 tigecycline resistant and CC/ST22-SCCmec IV/t790 vancomycin resistant Staphylococcus aureus strains isolated from wound: A two-year multi-center study in Tehran, Iran

Staphylococcus aureus as an opportunistic bacterial pathogen with intrinsic and acquired resistance to many antibiotics is a worldwide problem. The current study was undertaken to evaluate the resistance pattern, and determine the genetic types of multidrug-resistant S. aureus isolated from wound. This cross-sectional study was conducted over the period of two years (from December 2018 to November 2020) at the hospitals affiliated to Shahid Beheshti University of Medical Sciences, Tehran, Iran. In present study, 75 multidrug-resistant S. aureus isolates collected from wound infections were investigated. Phenotypic resistance was assessed by Kirby-Bauer disk diffusion method. Conventional PCR was performed for the detection of virulence encoding genes. Genotyping of strains was performed based on coa gene polymorphism using multiplex-PCR assay. SCCmec typing, spa typing and MLST were also used to characterize the genotype of the mupirocin, tigecycline and vancomycin resistant multidrug-resistant S. aureus isolates. All 75 multidrug-resistant S. aureus isolates in the study were confirmed as MRSA. Coagulase typing distinguished isolates into five genotypic patterns including III (40%), I (24%), IVb (16%), V (10.7%) and type X (9.3%). Resistance to tigecycline was detected in 4% of MDR-MRSA isolates and all belonged to CC8/ST239- SCCmec III/t421 lineage. According to our analysis, one VRSA strain was identified that belonged to coa type V and CC/ST22-SCCmec IV/t790 lineage. Resistance to mupirocin was detected in 9.3% of strains. All 7 mupirocin resistant MDR-MRSA isolates exhibited resistance to mupirocin in high level. Of these, 4 isolates belonged to CC/ST8-SCCmec IV/t008 (57.1%), 2 isolates belonged to CC/ST8-SCCmec IV/t064 (28.6%) and one isolate to CC/ST22-SCCmec IV/t790 (14.3%). Altogether, current survey provides a snapshot of the characteristics of S. aureus strains isolated from patients. Our observations highlighted type III as predominant coa type among multidrug-resistant MDR strains indicating low heterogeneity of these isolates. Our study also indicates the importance of continuous monitoring of the genotypes of MDR-MRSA isolates to prevent nosocomial outbreaks and the spread of MDR isolates.

Isolation and Genetic Characterization of Vancomycin-resistant and mecC+ Methicillin-resistant Staphylococcus aureus Strains in Clinical Samples of Bojnurd, Northeastern Iran

Background: The emergence of antibiotic-resistant Staphylococcus aureus strains is one of the major concerns about the various staphylococcal infections. Vancomycin is one the most important effective antibiotics on staphylococcal lethal infections. To date, vancomycin-resistant strains are increasingly isolated in different parts of the world, and it is alerting. Objectives: The current study was designed to evaluate the prevalence, and antibiotic susceptibility pattern of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant S. aureus (VRSA) isolates in the main tertiary hospital of Bojnurd, Iran. Methods: Staphylococcus aureus isolates were collected from different clinical samples in Imam Reza Hospital of Bojnurd. After identification of isolates through using conventional methods, they were evaluated by agar screening, disk diffusion, and minimum inhibitory concentration (MIC) methods to determine resistance to vancomycin and methicillin. We also performed polymerase chain reaction (PCR) for the detection of mecA, mecC, vanA, and vanB genes. After confirmation of vancomycin resistance, genetic analysis was performed using SCCmec, agr, and spa typing, and multilocus sequence typing (MLST) methods on VRSA isolates. Results: We found four vancomycin-resistant isolates (1.29%). Also, 75% of isolates were resistant to cefoxitin. Using the PCR method, mecA was found in 73%, mecC in 0.64%, and vanA in 1.29% of isolates. Interestingly, we found two mecC positive isolates in MRSA isolates. The alpha-hemolysin (81.81%) and enterotoxin C (27%) had the highest and lowest toxins percentage, respectively. Among mecA positive isolates, SCCmec IV (37%), SCCmec III (31.27%), SCCmec I (14%), SCCmec II (11%), and SCCmec V (5.7%) were the most prevalent SCCmec types, respectively. It should be noted that the two mecC positive isolates belonged to SCCmec XI. Agr I (76.29%) was the highest agr type. We recognized t037 as the dominant spa type, and ST239, ST6, ST97, and ST8 were found in VRSA isolates. Conclusions: In our study, the frequency of mecA genes in MRSA isolates was very high. It seems that the resistant isolates belonged to endemic clones of Iran.

Systematic review and meta-analysis of the epidemiology of vancomycin-resistance Staphylococcus aureus isolates

BACKGROUND

Vancomycin‑resistant Staphylococcus aureus (VRSA) is a serious public health challenging concern worldwide.

OBJECTIVES

Therefore, the objective of present study of 62 published studies was to evaluate the prevalence of VRSA based on different years, areas, isolate source, antimicrobial susceptibility testing, and the genetic determinants.

METHODS

We searched the relevant articles that focused on the prevalence rates of VRSA in PubMed, Scopus, Embase, and Web of Science from 2000 to 2019. Statistical analyses were conducted using STATA software (version 14.0).

RESULTS

The prevalence of VRSA was 2% before 2006, 5% in 2006-2014, and 7% in 2015-2020 that showed a 3.5-fold increase in the frequency of VRSA between before 2006 and 2020 years. The prevalence of VRSA was 5% in Asia, 1% in Europe, 4% in America, 3% in South America, and 16% in Africa. The frequencies of VRSA isolated from clinical, non-clinical, and mixed samples were 6%, 7%, and 14%, respectively. The prevalence of VRSA was 12% using disk diffusion agar method, 7% using MIC-base methods, and 4% using mixed-methods. The prevalence of vanA, vanB, and vanC1 positive were 71%, 26%, and 4% among VRSA strains. The most prevalent genotype was staphylococcal cassette chromosomemec (SCCmec) II, which accounted for 57% of VRSA. The most prevalent staphylococcal protein A (spa) types were t002, t030, and t037.

CONCLUSION

The prevalence of VRSA has been increasing in recent years particularly in Africa/Asia than Europe/America. The most prevalent of genetic determinants associated with VRSA were vanA and SCCmec II. This study clarifies that the rigorous monitoring of definite antibiotic policy, regular surveillance/control of nosocomial-associated infections and intensive surveillance of vancomycin-resistance are required for preventing emergence and further spreading of VRSA.

Eradication of vancomycin-resistant Staphylococcus aureus on a mouse model of third-degree burn infection by melittin: An antimicrobial peptide from bee venom

Third-degree burn infections caused by antibiotic-resistant bacteria are of high clinical concern. Chemical antibiotics are not promising in eradication of bacterial infections. In this challenging condition, antimicrobial peptides (AMPs) are recently introduced as novel promising agents to overcome the issue. Accordingly, our study aimed to evaluate the efficiency of 'melittin' as natural peptide in bee venom, in eradicating vancomycin resistant Staphylococcus aureus (VRSA) on a mouse model of third-degree burn infection. In vitro pharmacological value of melittin was determined by examining its inhibitory and killing activities on VRSA isolates at different doses and time periods. The action mechanism of 'melittin' was evaluated by fluorescent release assay and Field Emission Scanning Electron Microscopy (FE-SEM) analyses. In vivo activity and toxicity of melittin were also examined on a mouse model of third-degree burn infection. The Minimum Inhibitory Concentration (MIC) and the Minimum Bactericidal Concentration (MBC) of melittin on all isolates ranged from '0.125-2 μg/mL' and '0.125-4 μg/mL', respectively. Rapid antibacterial activity of melittin on VRSA isolates was demonstrated by killing kinetics assays. Fluorometric and FE-SEM analyses indicated the membranolytic effects of melittin on VRSA isolates. The colonized VRSA bacteria were eradicated by melittin at 16 μg, in a single dose. No dermal toxicity and in vivo hemolysis were observed in the examined mice. The lack of in vivo toxicity of melittin along with its potent antibacterial activity indicated its promising therapeutic value as a topical drug against S. aureus associated third-degree burn infections.

Molecular Characterization of Staphylococcus aureus Obtained from Blood Cultures of Paediatric Patients Treated in a Tertiary Care Hospital in Mexico

Purpose

Staphylococcus aureus is one of the main causative agents of hospital-acquired (HA) infections. In Mexico, information about the characteristics of clinical S. aureus isolates is limited. Our aim was to characterize S. aureus strains obtained from blood cultures of paediatric patients treated in a tertiary care hospital.

Materials and Methods

We analysed 249 S. aureus isolates over the period from 2006 to 2019, and their resistance profiles were determined. The isolates were classified into methicillin-resistant S. aureus (MRSA) or methicillin-sensitive S. aureus (MSSA). Staphylococcal cassettes chromosome mec (SCCmec) were detected. Virulence genes (cna, clfA, clfB, eta, etb, fnbA, fnbB, hla, pvl, sec, and tsst) were amplified, and their clonal relationships were established by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and clonal complex (CC) typing. We reviewed one hundred medical files to collect clinical information.

Results

Thirty-eight percent of the isolates were MRSA and showed an expanded profile of resistance to other non-beta-lactam antibiotics, while MSSA strains presented a reduced resistance profile. SCCmec-II was the most frequent element (86.3%). Eight virulence factors were detected in MSSA and six in MRSA. The pvl gene was detected in four MRSA-SCCmec-IV isolates (P≤0.0001). MRSA isolates were distributed among 14 clones and were classified into 15 sequence types (ST); the most frequent was ST1011 (17%). The most common CC in MRSA was CC5 (69%, P≤0.0001), and in MSSA, it was CC30 (30%, P≤0.0001). Eighty-seven percent of MRSA isolates were HA-MRSA, and 13% were community-acquired MRSA (CA-MRSA). Of 21 HA-MRSA isolates, 17 had SCCmec-II, while two CA-MRSA isolates had SCCmec-IV. Of MSSA isolates, 77% were derived from HA infections and 23% from CA infections.

Conclusion

MSSA isolates had more virulence factors. MRSA isolates were resistant to more non-beta-lactam antibiotics, and those with SCCmec-IV expressed a greater variety of virulence factors. Most S. aureus isolates belonged to CC5.

Clonal diversity and genomic characterization of Panton-valentine Leukocidin (PVL)-positive Staphylococcus aureus in Tehran, Iran

Background

Some Staphylococcus aureus strains produce Panton-Valentine leukocidin (PVL), a bi-component pore-forming toxin, which causes leukocyte lysis and tissue necrosis. Currently, there is very limited information on the molecular epidemiology of PVL-encoding S. aureus strains in Iran. This study aimed to determine the molecular epidemiology and genetic background of PVL-positive S. aureus clinical strains isolated from Iranian patients.

Methods

A total of 28 PVL-positive S. aureus strains were detected from 600 S. aureus isolates between February 2015 and March 2018 from different hospitals in Tehran, Iran. Antimicrobial susceptibility testing was performed according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Molecular genotyping was performed using SCCmec and accessory gene regulator (agr) typing, PVL haplotyping, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE).

Results

The highest antibiotic resistance rate was found to be against erythromycin (57.1%), followed by ciprofloxacin (42.8%) and clindamycin (35.7%). Moreover, 19 (67.9%) out of 28 S. aureus isolates were identified as MRSA, including CA-MRSA (14/19, 73.7%) and HA-MRSA (5/19, 26.3%). SCCmec type IVa was detected as the predominant type (10/19, 52.6%), followed by type III (5/19, 26.3%) and type V (4/19, 21.1%). The agr type I was identified as the most common type (14/28, 50%), and H and R haplotype groups were observed at frequencies of 67.9 and 32.1%, respectively. Among H variants, the predominant variant was H2 (78/9%). The isolates encompassed 21 different sequence types (STs), including 16 new STs (ST5147 to ST5162). Based on eBURST analysis, the isolates were clustered into five CCs, including CC30, CC22, CC1, CC8, and CC5 (ST5160), and nine singletons. PFGE typing showed that 24 isolates were clustered into A (4 pulsotypes), B (9 pulsotypes), and C (11 pulsotypes) clusters.

Conclusions

A high prevalence of PVL-positive CA-MRSA strains was detected in Iran. The majority of PVL-positive isolates were of H (mostly H2) variant, while R variant was harbored by 100% of PVL-positive MRSA strains. Also, CC8, CC22, and CC30 were identified as the dominant clones among PVL-encoding S. aureus strains. This study promotes a better understanding of the molecular epidemiology and evolution of PVL-positive S. aureus strains in Iran.

Efficacy of metal oxide nanoparticles as novel antimicrobial agents against multi-drug and multi-virulent Staphylococcus aureus isolates from retail raw chicken meat and giblets

Staphylococcus aureus is among the most common zoonotic pathogens originating from animals consumed as food, especially raw chicken meat (RCM). As far as we know, this might be the first report that explores the efficacy of metal oxide nanoparticles (MONPs), such as zinc peroxide nanoparticles (ZnO₂-NPs), zinc oxide nanoparticles (ZnO-NPs), and titanium dioxide nanoparticles (TiO₂-NPs) against multidrug resistant (MDR) and/or pandrug resistant (PDR) S. aureus strains with a strong biofilm-producing ability isolated from RCM and giblets. The overall prevalence of coagulase-positive staphylococci was 21%, with a contamination level range between 10² and 10⁴ CFU/g. The incidence of virulence genes See (21/36), pvl (16/36), clfA (15/36), sec (12/36), tst (12/36), and sea (11/36) among S. aureus strains were relatively higher those of seb, sed, fnbA, and fnbB. For antimicrobial resistance gene distribution, most strains harbored the blaZ gene (25/36), aacA-aphD gene (24/36), mecA gene (22/36), vanA gene (20/36), and apmA gene (20/36) confirmed the prevalence of MDR among S. aureus of RCM products. However, cfr (11/36), spc (9/36), and aadE (7/36) showed a relatively lower existence. The data of antibiogram resistance profiles was noticeably heterogeneous (25 patterns) with 32 MDR and four PDR S. aureus strains. All tested strains had a very high MAR index value (>0.2) except the P11 pattern (GEN, MXF, PMB), which showed a MAR index of 0.19. Among the strong biofilm-producing ability (BPA), 14 (70%) strains were isolated from wet markets, while only six strong BPA strains were isolated from supermarkets. The mean values of BPA ranged from 2.613 ± 0.04 to 11.013 ± 0.05. Clearly, ZnO₂-NPs show significant inhibitory activity against S. aureus strains compared with those produced by the action of ZnO-NPs and TiO₂-NPs. The results of anti-inflammatory activity suggest ZnO₂-NPs as a lead compound for designing an alternative antimicrobial agent against drug-resistant and strong biofilm-producing S. aureus isolates from retail RCM and giblets.

Prevalence and Characterization of Coagulase Positive Staphylococci from Food Products and Human Specimens in Egypt

Methicillin-resistant Staphylococcus aureus (MRSA) strains have veterinary and public health importance as they are responsible for a wide range of difficult to treat infections and food poisoning. Two hundred samples (50 samples each of minced meat, beef luncheon, Karish cheese, and human samples (pus swab from open wounds)) were cultured, and MRSA strains were identified using disk diffusion tests and mecA gene-based PCR. A total of 35% (70/200) of the examined samples were confirmed as coagulase-positive S. aureus in minced meat (46%), beef luncheon (44%), Karish cheese (44%), and human samples (22%). The MRSA strains showed resistance to amoxicillin (91.4%), penicillin (97.1%), cefoxitin (85.7%), cephradine (82.9%), tetracycline (57.2%), and erythromycin (52.8%). More than half of the tested S. aureus isolates harbored the mecA gene. The sequence analysis of the mecA gene from the minced meat, Karish cheese, and human samples revealed high genetic similarities between the S. aureus isolates from these sources. In conclusion, our findings indicate a risk for the transmission of the mecA gene of S. aureus across the food chain between humans and animal food products. Further studies should focus on finding additional epidemiological aspects of the MRSA strains in food chain.

The prevalence of drug-resistant and virulent Staphylococcus spp. in a municipal wastewater treatment plant and their spread in the environment

Drug-resistant and pathogenic Staphylococcus spp. strains can reach surface waters and air with wastewater evacuated to the environment. These strains increase the environmental pool of genetic determinants conferring antibiotic resistance and virulence, and constitute a health risk for the employees of wastewater treatment plants (WWTP) who come into daily contact with bioaerosols. The aim of this study was to identify the genetic determinants of drug resistance and virulence in Staphylococcus spp. strains isolated from untreated (UWW) and treated wastewater (TWW), an activated sludge (AS) bioreactor, river water collected upstream and downstream from the wastewater discharge point (URW and DRW), and WWTP employees. All isolates were analysed for the presence of the rpoB gene, and were subjected to clonal analysis by ERIC fingerprinting. As a result, 249 of the 455 analysed isolates were selected for PCR. The presence of the gene encoding nuclease activity in S. aureus (nuc), the methicillin resistance gene (mecA), vancomycin resistance gene (vanA), antiseptic resistance gene (qacA/B) and virulence genes (sasX, pvl, tst1, hla, sec) was determined. The prevalence of nuc, mecA, vanA and qacA/B genes in wastewater and river water was determined by quantitative PCR (qPCR). In the group of strains isolated from wastewater and water samples, 63% were identified as S. aureus, and 20% of the strains carried the vanA gene. The hla virulence gene was present in 80% of the isolates, and the pvl gene was detected in 27% of the isolates. In the group of strains isolated from the employees, 82% were identified as S. aureus, and the presence of vanA and mecA genes was confirmed in 14% and 16% of the isolates, respectively. The most prevalent virulence gene was hla (74%), whereas pvl was observed in 43% of the isolates. The quantitative analysis revealed the highest concentrations of the studied genes in UWW samples, at 2.56x10⁴ gene copies/ml for nuc, 1.18x10³ gene copies /ml for mecA, 8.28x10⁵ gene copies /ml for vanA and 3.83x10⁵ gene copies /ml for qacA/B. Some of analysed genes were identified in the isolates from both URW and DRW samples, as well as in genomic DNA of these samples. These results indicate that wastewater is not effectively treated in the analysed WWTP, which could contribute to the dissemination of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) to the environment. An analysis of the genetic relatedness of selected isolates revealed clusters of strains originating from UWW samples, AS samples and the employees. These observations suggest that ARGs and ARB are transmitted by wastewater bioaerosols to the upper respiratory tract mucosa of the plant's employees, thus increasing their exposure to infectious factors.

Global prevalence and distribution of vancomycin resistant, vancomycin intermediate and heterogeneously vancomycin intermediate Staphylococcus aureus clinical isolates: a systematic review and meta-analysis

Vancomycin-resistant Staphylococcus aureus (VRSA), Vancomycin-intermediate S. aureus (VISA) and heterogeneous VISA (hVISA) are subject to vancomycin treatment failure. The aim of the present study was to determine their precise prevalence and investigate prevalence variability depending on different years and locations. Several international databases including Medline (PubMed), Embase and Web of Sciences were searched (data from 1997 to 2019) to identify studies that addressed the prevalence of VRSA, VISA and hVISA among human clinical isolates around the world. Subgroup analyses and meta-regression were conducted to indicate potential source of variation. Publication bias was assessed using Egger's test. Statistical analyses were conducted using STATA software (version 14.0). Data analysis showed that VRSA, VISA and hVISA isolates were reported in 23, 50 and 82 studies, with an overall prevalence of 1.5% among 5855 S. aureus isolates, 1.7% among 22,277 strains and 4.6% among 47,721 strains, respectively. The overall prevalence of VRSA, VISA, and hVISA before 2010 was 1.2%, 1.2%, and 4%, respectively, while their prevalence after this year has reached 2.4%, 4.3%, and 5.3%. The results of this study showed that the frequency of VRSA, VISA and hVISA after 2010 represent a 2.0, 3.6 and 1.3-fold increase over prior years. In a subgroup analysis of different strain origins, the highest frequency of VRSA (3.6%) and hVISA (5.2%) was encountered in the USA while VISA (2.1%) was more prevalent in Asia. Meta-regression analysis showed significant increasing of VISA prevalence in recent years (p value ≤ 0.05). Based on the results of case reports (which were not included in the calculations mentioned above), the numbers of VRSA, VISA and hVISA isolates were 12, 24 and 14, respectively, among different continents. Since the prevalence of VRSA, VISA and hVISA has been increasing in recent years (especially in the Asian and American continents), rigorous monitoring of vancomycin treatment, it's the therapeutic response and the definition of appropriate control guidelines depending on geographical regions is highly recommended and essential to prevent the further spread of vancomycin-resistant S. aureus.

Bactericidal Capacity of a Heterogeneous TiO2/ZnO Nanocomposite against Multidrug-Resistant and Non-Multidrug-Resistant Bacterial Strains Associated with Nosocomial Infections

The surge of medical devices associated with nosocomial infection (NI) cases, especially by multidrug-resistant (MDR) bacterial strains, is one of the pressing issues of present health care systems. Metal oxide nanoparticles (MNPs) have become promising antibacterial agents against a wide range of bacterial strains. This work study is on the bactericidal capacity of heterogeneous TiO₂/ZnO nanocomposites with different weight percentages and concentrations against common MDR and non-MDR bacterial strains. The profiles on disk diffusion, minimum inhibitory concentration, minimum bactericidal concentration, tolerance determination, time-kill, and biofilm inhibition assay were determined after 24 h of direct contact with the nanocomposite samples. Findings from this work revealed that the heterogeneous TiO₂/ZnO nanocomposite with a 25T75Z weight ratio showed an optimal tolerance ratio against Gram-positive and -negative bacteria, indicating their bactericidal capacity. Further observation suggests that higher molar ratio of Zn²⁺ may possibly involve generation of active ion species that enhance bactericidal effect against Gram-positive bacterial strains, especially for the MDR strains. Nano-based technology using MNPs may provide a promising solution for the prevention and control of NIs. Further work on biocompatibility and cytotoxicity profiles of this nanocomposite are needed.

Effect of Ceftaroline, Vancomycin, Gentamicin, Macrolides, and Ciprofloxacin against Methicillin-Resistant Staphylococcus aureus Isolates: An In Vitro Study

Background: Methicillin-resistant Staphylococcus aureus (MRSA) infection remains a challenging threat because of limited treatment options. Ceftaroline was identified as having potent anti-MRSA activity. Aim: To evaluate the susceptibility of MRSA to gentamicin, macrolides, ciprofloxacin, vancomycin, and ceftaroline and to perform molecular characterization of different resistance genes as aminoglycoside modifying enzyme genes, ermA and ermC, and vanA and vanB genes. Patients and Methods: One hundred non-duplicate MRSA strains were isolated from different samples of hospitalized patients in Cairo University teaching hospitals from November 2015 to August 2016. Determination of antibiotic susceptibility was done using disk diffusion test and minimum inhibitory concentration followed by detection of resistance genes by multiplex polymerase chain reaction (PCR). Results: Of 100 MRSA isolates, 63 (63%) were resistant to gentamicin, erythromycin, clindamycin, and ciprofloxacin, however, all were sensitive to ceftaroline. Fifteen isolates (15%) were vancomycin intermediate resistant and were sensitive to ceftaroline as well. Conclusion: Ceftaroline was potent against MRSA, which was found to be non-susceptible to vancomycin, ciprofloxacin, erythromycin, clindamycin, and gentamicin and it may represent a successful treatment for MRSA infections.

Clinical, Epidemiologic, and Laboratory Aspects of Methicillin-Resistant Staphylococcus aureus Infections

Oxacillin-resistant Staphylococcus aureus (abbreviated MRSA for historical reasons) is a major pathogen responsible for both hospital- and community-onset disease. Resistance to oxacillin in most clinical isolates of S. aureus is mediated by PBP2a, a penicillin-binding protein with low affinity to beta-lactams, encoded primarily by the mecA gene. Rapid and accurate methods of susceptibility testing of S. aureus isolates to identify MRSA infections are important tools to limit the spread of this organism. This review focuses on the clinical significance of MRSA infections and new approaches for the laboratory diagnosis and epidemiologic typing of MRSA strains.

Incidence of Vancomycin Resistant Phenotype of the Methicillin Resistant Staphylococcus aureus Isolated from a Tertiary Care Hospital in Lahore

Staphylococcus aureus (S. aureus)-associated infections are one of the major threats to public health. The aim of the present study was to determine the antibiotic resistance pattern as well as the genetic characterization of methicillin and vancomycin resistant S. aureus (VRSA) isolated from a tertiary care hospital in Lahore. The S. aureus isolates were isolated from different clinical samples, identified by biochemical testing, and subjected to antibiotic susceptibility testing via the disc diffusion method or broth microdilution method. The methicillin resistance gene (mecA) and vancomycin resistance gene (vanA) were amplified by the polymerase chain reaction. The S. aureus isolates showed high incidences of resistance against methicillin (76%) and moderate incidences of resistance to vancomycin (14%). Isolates were also resistant to several other drugs, such as cefoxitin (76%), ertapenem (83%), ampicillin (81%), tobramycin (78%), moxifloxacin (76%), and tetracycline (74%). An encouraging finding was that 98% of isolates were susceptible to tigecycline, indicating its possible role in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) and VRSA, as well as the multi-drug resistant S. aureus. The mecA gene was detected in 33.3% of tested isolates (10/30), while the vanA gene was also detected in 30% (9/30) of the tested isolates. In conclusion, the frequent presence of methicillin and vancomycin resistance in S. aureus appraises the cautious use of these antibiotics in clinical practices. Furthermore, it is suggested that there should be continuous monitoring of tigecycline treatments in clinical setups in order to delay the development of resistance against it.

Vancomycin resistant Staphylococcus aureus infections: A review of case updating and clinical features

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MRSA infection is a global threat to public health.

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Vancomycin is one of the first-line drugs for the treatment of MRSA infections.

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MRSA with complete resistance to vancomycin have emerged in recent years.

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The total number of VRSA isolates is updated in this paper.

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Resistance mechanisms, characteristics of VRSA infections, as well as clinical treatments are reviewed.

The infection caused by methicillin-resistant Staphylococcus aureus (MRSA) is a global threat to public health. Vancomycin remains one of the first-line drugs for the treatment of MRSA infections. However, S. aureus isolates with complete resistance to vancomycin have emerged in recent years. Vancomycin-resistant S. aureus (VRSA) is mediated by a vanA gene cluster, which is transferred from vancomycin-resistant enterococcus. Since the first VRSA isolate was recovered from Michigan, USA in 2002, 52 VRSA strains have been isolated worldwide. In this paper, we review the latest progresses in VRSA, highlighting its resistance mechanism, characteristics of VRSA infections, as well as clinical treatments.

Vancomycin-resistant Staphylococcus aureus isolated from camel meat and slaughterhouse workers in Egypt

Background

The emergence of vancomycin-resistant Staphylococcus aureus (VRSA) represents a challenge for the treatment of staphylococcal infections in both human and animals worldwide. Although VRSA has been detected in several animal species worldwide, data on the bacterial prevalence in dromedary camels and workers in camel slaughterhouses are scarce.

Methods

We investigated meat samples from 200 dromedary camel carcasses from three different abattoirs that were being prepared to be sent to the markets. Twenty hand swabs were voluntarily collected from the workers in the same abattoirs. Isolation and identification of the bacterial specimens from the samples were performed using conventional cultural techniques and biochemical identification and were confirmed by PCR amplification of the nuc gene. Antimicrobial susceptibility against nine antimicrobial agents commonly used in human and camels was tested using the disc diffusion method, and genetic analysis was performed by evaluating the mecA gene in phenotypically oxacillin (OXA)- and cefoxitin (FOX)-resistant isolates. The resistance of S. aureus to vancomycin (VAN) was tested by broth microdilution and confirmed by PCR targeting the vanA and vanB genes. The vanA and vanB genes were sequenced.

Result

S. aureus was detected in both camel meat (29/200, 14.5%) and in abattoir workers (11/20, 55%). Of the collected samples, 27% (8/29, camel) and 54% (6/11, human) were identified as VRSA.

All VRSA isolates carried both the vanA and vanB genes. Additionally, all VRSA isolates were also classified as methicillin-resistant S. aureus (MRSA). The vanA amplicons of the isolates from human and camel meat were homologous and clustered with a Chinese reference isolate sequence.

Conclusion

This study demonstrated that VRSA is present in camel abattoirs in Egypt. Zoonotic transmission between animals and human is probable and reflects both a public health threat and a food safety concern.

Genetic characterization of two vancomycin-resistant Staphylococcus aureus isolates in Kerman, Iran

Aim

The aim of this study was the genetic characterization of two clinical vancomycin-resistant Staphylococcus aureus (VRSA) isolates.

Materials and methods

Resistance to vancomycin was determined by phenotypic method. PCR was used for detection of mecA, vanA, ermA, ermB, ermC, msrA/B, aph(2")-Ic, aph(3')-IIIa, pvl, Immune Evasion Cluster [sea, sep, chip, sak and scn] genes and biofilm operon icaABCD. On the other hand, multilocus sequence typing and agr typing methods were performed for the determination of clonal relationship and van operon was detected and sequenced.

Results

Vancomycin-resistant Staphylococcus aureus strain 1 (VRSA-1) was positive for vanA, ermA, ermC, aph(2")-Ic, aph(3')-IIIa, sea, sep, icaD genes, belonging to agr type I; SCCmec type III; spa type t030; and ST239. However, the genetic characterization of Vancomycin-resistant Staphylococcus aureus strain 2 (VRSA-2) revealed the presence of various types of resistance genes vanA, ermA, ermC, aph(2")-Ic, aph(3')-IIIa, sea, icaD, relating to agr type I; SCCmec type III; spa type t459; and ST239. The presence of transposon Tn1546 was determined by PCR sequencing.The Basic Local Alignment Search Tool analysis of van operon in the VRSA isolates showed 99.6% sequence homology to Tn1546 in vancomycin-resistant enterococci, indicating the vanA operon has an enterococcal origin.

Conclusion

In conclusion, the ST239 is one of the most common clones of MRSA isolates which involved the hospital-associated infections, therefore, the emergence of VRSA isolates with ST239 increased the spread of resistance to vancomycin in the hospital settings.

Screening of genes encoding adhesion factors and biofilm production in methicillin resistant strains of Staphylococcus aureus isolated from Palestinian patients

BACKGROUND

Intercellular adhesion and biofilm production by Staphylococcus aureus makes these bacteria resistant to antimicrobial therapy. Here, Methicillin-resistant Staphylococcus aureus (MRSA) strains were characterized and the prevalence of genes encoding adhesion factors and biofilm formation was determined.

RESULTS

All 248 MRSA isolates identified by cefoxitin disc diffusion were positive for the mecA gene. SCCmec-IV was the most frequently detected genotype (92.7%) and SCCmec-IVa was also very prevalent (84.3%). The quantitative microtiter plate assay showed that all the isolates were able to produce biofilm with levels ranging from high (21%) to moderate (46.4%) to low (32.7%). All the strains possessed the icaD/icaA genes and produced biofilm (P < 0.05). None of the isolates possessed the bap gene. Furthermore, 94.8% of the isolates were positive for eno, 80.2% for clfA and for clfB, 78.2% for fnbA, 76.2% for ebps, 62.2% for fib, 39.9% for cna and 29.0% for fnbB. Also, nearly 69.8% of the isolates were positive for the gene sarA. All four agr groups were present: agr group 1 was predominant with 39.5%; agr group 3. agr group 2 and 3 strains carried more toxin-producing genes, and frequently produced more toxin. Sixty-six (26.6%) of the strains were multidrug resistant. All were vancomycin sensitive. Agr group I is more resistant to ciprofloxacin and gentamicin while agr group III is more resistant to erythromycin. Maximum sensitivity was to gentamicin and SXT, and they could be considered drugs of choice for controlling MRSA mediated infections in this region.

CONCLUSIONS

Biofilm development in MRSA might be an ica dependent and one needs to investigate the involvement of other global regulators, agr and sarA, and their contribution to the biofilm phenotype, as the high rate of biofilm production among the studied strains of S. aureus.

Genetic characterization of two vancomycin-resistant Staphylococcus aureus isolates in Kerman, Iran

Aim

The aim of this study was the genetic characterization of two clinical vancomycin-resistant Staphylococcus aureus (VRSA) isolates.

Materials and methods

Resistance to vancomycin was determined by phenotypic method. PCR was used for detection of mecA, vanA, ermA, ermB, ermC, msrA/B, aph(2”)-Ic, aph(3ʹ)-IIIa, pvl, Immune Evasion Cluster [sea, sep, chip, sak and scn] genes and biofilm operon icaABCD. On the other hand, multilocus sequence typing and agr typing methods were performed for the determination of clonal relationship and van operon was detected and sequenced.

Results

Vancomycin-resistant Staphylococcus aureus strain 1 (VRSA-1) was positive for vanA, ermA, ermC, aph(2”)-Ic, aph(3ʹ)-IIIa, sea, sep, icaD genes, belonging to agr type I; SCCmec type III; spa type t030; and ST239. However, the genetic characterization of Vancomycin-resistant Staphylococcus aureus strain 2 (VRSA-2) revealed the presence of various types of resistance genes vanA, ermA, ermC, aph(2”)-Ic, aph(3ʹ)-IIIa, sea, icaD, relating to agr type I; SCCmec type III; spa type t459; and ST239. The presence of transposon Tn1546 was determined by PCR sequencing.The Basic Local Alignment Search Tool analysis of van operon in the VRSA isolates showed 99.6% sequence homology to Tn1546 in vancomycin-resistant enterococci, indicating the vanA operon has an enterococcal origin.

Conclusion

In conclusion, the ST239 is one of the most common clones of MRSA isolates which involved the hospital-associated infections, therefore, the emergence of VRSA isolates with ST239 increased the spread of resistance to vancomycin in the hospital settings.

Genetic Diversity Analysis of Methicillin-resistant Staphylococcus aureus Strains Isolated from Intensive Care Unit in Iran

Objectives

Staphylococcus aureus has emerged as a major public health concern. It is a common pathogen in high-risk hospital intensive care units (ICUs). We analyzed the molecular characteristics on the SCCmec and spa genes of S. aureus isolates gathered from ICUs. The antibiotic resistance patterns and carriage of resistance and virulence determinants were also identified.

Methods

In this cross-sectional study, 84 non-duplicated S. aureus strains isolated from ICU patients in were genotyped using SCCmec and spa typing. The Kirby-Bauer disk diffusion and micro-broth dilution methods were used to determine resistance patterns. Virulence and resistance gene profiling were also determined using the polymerase chain reaction technique.

Results

All isolates were methicillin-resistant S. aureus and belonged to seven spa types: t388 (36.9%), t852 (14.3%), t924 (13.1%), t790 (11.9%), t064 (10.7%), t037 (9.5%), and t084 (3.6%). They differed in the carriage of resistance and toxin genes. The most common SCCmec type was III detected in 50 isolates (59.5%), followed by type IV in 34 isolates (40.5%). The pvl gene was detected in 14.3% (n = 12) of isolates, of which 66.7% (n = 8) belonged to t852 and 33.3% (n = 4) belonged to t790. Among the tested strains, 9.5% (n = 8) carried the mupA gene and belonged to the t064 spa type.

Conclusions

The data revealed a high resistance rate to antibiotics, which could be a threat to ICU patients. It is necessary to detect antimicrobial resistance and resistance and toxin-encoding of gene profiles in different molecular types.

Detection of vancomycin nonsusceptible strains in clinical isolates of Staphylococcus aureus in northern Iran

Glycopeptides, particularly the cell wall-acting antibiotic vancomycin, are the safest cure for methicillin-resistant Staphylococcus aureus. The aim of this study was to evaluate nonsusceptibility of clinical isolates of S. aureus to vancomycin and investigate mutations in vraSR, a cell wall synthesis regulator gene, in vancomycin-resistant strains. Susceptibility of 110 clinical strains of S. aureus to methicillin and vancomycin were determined using disc diffusion method and determination of minimum inhibitory concentration, respectively. Presence of mecA and vanA genes was determined by PCR. Determination of spa types and mutations of the vraSR gene in vancomycin nonsusceptible isolates were assessed by PCR-sequencing analyses. In total, 47 isolates (42.73%) were recognized as MRSA, three (2.73%) strains were resistant to vancomycin, and eight (7.27%) strains were vancomycin intermediates. The MIC of vancomycin was 4-64 μg/ml in these isolates. All vancomycin nonsusceptible S. aureus strains were mecA positive and one isolate was positive for the vanA gene. Spa type t030 was found as the most common type. In vraSR sequence analysis, all 11 vancomycin nonsusceptible isolates had the D59E mutation in the vraR and E45G in vraS genes. R117H, R121S, and R121I are the other identified missense mutations in the vraR gene. The identification of a high percentage of MRSA and presence of VRSA and VISA isolates is a serious warning about the treatment of future MRSA infections and reveals the need for new and effective therapeutic agents.

Molecular Characterization of Vancomycin, Mupirocin and Antiseptic Resistant Staphylococcus aureus Strains

Background

Staphylococcus aureus is a common cause of nosocomial infections leading to a broad spectrum of diseases. Increasing antibiotic resistance among S. aureus strains, particularly methicillin-resistant S. aureus (MRSA), is a serious concern. In addition, the emergence of antiseptics resistance in MRSA helps the organism to persist and spread in healthcare environments easily. The aim of this study was to determine the molecular characteristics of vancomycin, mupirocin, and antiseptic resistant S. aureus strains.

Materials and Methods

This cross-sectional study was performed on a total of 120 MRSA isolates collected from two major hospitals in Shiraz, Iran. Minimum inhibitory concentrations (MICs) of vancomycin and mupirocin were determined by E-test method according to CLSI and Eucast guidelines. Presence of resistance genes was investigated by PCR method.

Results

Antibacterial susceptibility tests for MRSA isolates showed that three isolates (2.5%) were vancomycin-intermediate S. aureus (VISA), seven isolates (5.8%) were vancomycin-resistant S. aureus (VRSA), and 15 isolates (12.5%) were high-level mupirocin-resistant (MuH). None of the isolates had vancomycin resistance gene (vanA), but the frequency of mupirocin resistance gene was significant, and 55 (45.8%) isolates carried the mupA gene. Moreover, norA, smr and qacA/B genes were detected in 110 (91.7%), 55 (45.8%) and 36 (30%) strains, respectively.

Conclusion

This study showed the existence of VISA and VRSA strains in our region, and we also found a high frequency of mupirocin and biocide resistance genes among them.

Molecular Characterization of Methicillin and Vancomycin Resistant Staphylococcus aureus Strains Isolated from Hospitalized Patients

Objectives: Nosocomial infections caused by methicillin resistant Staphylococcus aureus (MRSA) and emergence of vancomycin resistant S. aureus (VRSA) have led to great concern in healthcare settings worldwide. Methods: A total of 100 S. aureus clinical isolates from hospitalized patients were investigated for antimicrobial susceptibility, the presence of resistance (mecA, vanA, and vanB) and virulence (hlaA, fnbpA, cna, clfA, tsst-1, eta, and spa) encoding genes, and molecular typing based on polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of spa gene. Results: All isolates were resistant to one or more antibiotics, with the most frequent resistance found against amoxicillin (69%). A total of 46 isolates were MRSA, and 40% of isolates were multidrug resistant (MDR). Of all S. aureus isolates, two isolates were confirmed as VRSA and four isolates confirmed as vancomycin intermediate S. aureus (VISA). The frequency of clfA, cna, tsst-1, and eta genes among MRSA isolates was significantly higher than methicillin sensitive S. aureus (MSSA). The significant correlation between MDR isolates and the carriage of multiple virulence genes was seen. All MDR isolates carried at least four virulence genes. Furthermore, biofilm formation in MRSA isolates was significantly higher than MSSA. The spa gene PCR products generated 4 major and 10 minor types. After digestion of spa amplicons with HindIII restriction enzyme, 10 different patterns ranging 174-938 bp were detected. S2b and S2a subtypes were detected frequently in MRSA isolates. Conclusions: It seems that the appropriate surveillance and control measures are essential to prevent the emergence and transmission of MRSA and VRSA strains in our country.

Molecular Characterization of Methicillin-Resistant Staphylococcus aureus Isolates, Isolated from a Burn Hospital in Southwest Iran in 2006 and 2014

OBJECTIVES

Incidence of methicillin-resistant Staphylococcus aureus (MRSA) is increasing every year, especially in burn patients with a high rate of morbidity and mortality. Molecular and epidemiologic studies are useful practices for understanding the relatedness of isolates in a single patient or a hospital. This study aimed at determining molecular characterizations of isolates collected in 2006 and 2014 using S. aureus-specific staphylococcal protein A (Spa) typing and Multilocus Sequence Typing (MLST) methods.

MATERIALS AND METHODS

Totally, 71 MRSA isolates were collected during the last two studies (2006 and 2014) from burn patients at Taleghani Burn Centre. After confirmation, all isolates were analysed using MLST and Spa typing methods.

RESULTS

We reported the emergence of Spa type t021, ST-30-IV MRSA isolates, which were PVL-positive in 14.6% of the cases and t12366, ST-8-IV isolates, which were PVL-negative in 9.8% of the cases. In 2014 study, Spa typing of MRSA isolates revealed five different spa types. Overall, in two studies, t037, ST-239, SCCmec III, and CC8 were predominant clones and they were reported in 63% of the cases.

CONCLUSION

The predominance of ST-239 in this region during the last eight years is a major concern. It also has a disturbing impact on the management of staphylococcal infections. Moreover, the SCCmec type IV strain is able to disseminate rapidly in hospital environments, demanding an improvement in infection-control policy.

Phenotypic and Molecular Identification of Vancomycin Resistance in Clinical Staphylococcus Aureus Isolates in Osogbo, Nigeria

The use of vancomycin for treatment of serious infections caused by MRSA strains has resulted in emergence of vancomycin-resistant Staphylococcus aureus (VRSA) in clinical settings. Following our previous report of phenotypic VRSA in Nigeria, the current study attempts to determine the genetic basis underlying this resistance. Over a period of 6 months, non-duplicate clinical S. aureus isolates from 73 consecutive patients with infective conditions at Ladoke Akintola University of Technology Teaching Hospital, Osogbo were tested against a panel of eight selected antibiotics by disk diffusion test. The Epsilom test strip was used to determine vancomycin minimum inhibitory concentration (MIC) and polymerase chain reaction (PCR) assay to amplify nuc, mecA, vanA, and vanB genes. Of 73 isolates, 61 (83.6%) had MIC of ≤2 μg/ml, 11 (15.1%) had 4-8 μg/ml and 1 (1.4%) had 16 μg/ml. The mecA gene was detected in 5 (6.8%) isolates but none contained vanA or vanB genes. Both vancomycin-susceptible and intermediate isolates were resistant to multiple antibiotics, while the only vancomycin resistant isolate was resistant to all eight antibiotics. The result confirms the occurrence of phenotypic vancomycin intermediate-resistant S. aureus (VISA) and VRSA infections in Nigeria, but the molecular basis will require further investigation.

Molecular characterization of vancomycin-resistant Staphylococcus aureus strains isolated from clinical samples: A three year study in Tehran, Iran

Introduction

Emergence of vancomycin-intermediate Staphylococcus aureus (VISA) and vancomycin-resistant S. aureus (VRSA) strains has led to great concern in global public health in both developing and developed countries. This study investigated distribution and molecular characterization of VRSA strains in Tehran’s hospitals using a combination of molecular typing methods.

Materials and methods

A total of 1789 S. aureus isolates obtained between 2014 and 2017 and were characterized using antibiogram, SCCmec typing, spa typing, and multilocus-sequence typing. Resistance to vancomycin was determined by E-test method. After confirmation of the isolated VRSA strain, genetic analysis was performed by evaluating vanA and vanB genes presence.The presence of resistance (ermA, ermB, ermC, mupA, msrA, msrB, tetM, ant (4΄)-Ia, aac (6΄)-Ie/aph (2˝), aph (3΄)-IIIa) and toxin (etb, eta, pvl, tst) encoding genes was investigated by the polymerase chain reaction (PCR) technique.

Results

Of all S. aureus tested isolates, four isolates were confirmed as VRSA isolates and two isolates confirmed as VISA isolates. ST5- SCCmec II/t002 and ST239-SCCmec III/t037 strains had MIC values of 512μg/ml, ST239-SCCmec III/t037 and ST8-SCCmecIV/t008 strains had MIC values of 64μg/ml and ST22-SCCmec IV/t790 and ST239-SCCmec III/t030 strains had MIC values ≥ 8 μg/ml. pvl-encoding gene was confirmed in ST8-SCCmecIV/t008 and ST22-SCCmec IV/t790 strains. The isolates differed in the carriage of resistance and toxin encoding genes.

Conclusions

The study revealed the existence of VRSA strains in capital of Iran, Tehran. To our knowledge, this is the first report of ST239-SCCmec III/t037 as VRSA strain. These findings support the need for future surveillance studies on VRSA strains to keep the emergence and transmission of these isolates to a minimum.

Characterization of SCCmec and spa types of methicillin-resistant Staphylococcus aureus isolates from health-care and community-acquired infections in Kerman, Iran

Spread of methicillin-resistant Staphylococcus aureus (MRSA) isolates is a worldwide problem. Molecular typing is a useful tool to understand MRSA epidemiology. Herein, we determined vancomycin-resistant, SCCmec and spa types among MRSA isolates recovered from healthcare and community-acquired infections in Kerman, Iran. A total of 170 S. aureus isolates were collected from different patients who were admitted to affiliated hospitals of Kerman University of Medical science. MRSA and vancomycin-resistant S. aureus (VRSA) isolates were detected by phenotypic methods. Polymerase chain reaction (PCR) technique was used for detection of mecA, vanA and vanB genes. Staphylococcal cassette chromosomemec (SCCmec) and spa typing were used for molecular typing of among MRSA isolates. Overall, 53% of isolates were considered as MRSA. Two MRSA isolates were resistant to vancomycin and vanA was detected in only one of VRSA isolates. SCCmec type III belonged to spa types t030 and t459 which they were the dominant spa types among community-associated MRSA (CA-MRSA) and healthcare-acquired MRSA (HA-MRSA) isolates. Our findings showed that the SCCmec type I and III spread from hospital settings to community, although the SCCmec type IV spread from community to healthcare systems. We have also reported VRSA isolates from hospitalized patients, therefore, appropriate policies should be enforced in order to prevent the spread of antibiotic resistance isolates in hospitals settings.

Detection of Panton-valentine Leukocidin Gene Isoforms of Staphylococcus aureus Isolates in Al-Zahra Hospital, Isfahan-Iran

Background:

Panton-Valentine leukocidin (PVL) is a gamma-toxin produced by Staphylococcus aureus encoded by genes lukS/lukF-PV with several single-nucleotide polymorphisms. A mutation at nucleotide position 527 results in substitution of histidine (H) to arginine (R) at amino acid 176. The groups defined based on the amino acid change, the “R isoform” group and the “H isoform” group. The purpose of this study was to determine the frequency of PVL gene isoforms in S. aureus strains isolated from patients at Al-Zahra Hospital Isfahan and molecular characterization of PVL-positive methicillin-resistant S. aureus (MRSA) strains including the detection of mecA gene and staphylococcal chromosomal cassette mec (SCCmec) typing.

Materials and Methods:

In this study, 130 isolates of S. aureus were collected from Al-Zahra Hospital. The PVL gene identified using polymerase chain reaction (PCR); PCR products were sequenced to identify the type of isoform. The molecular characterization of isolates of PVL-positive MRSA including detection of mecA gene by PCR and also SCCmec typing was performed by multiplex PCR.

Results:

Out of 130 isolates, 23% were positive for the presence of PVL genes. The PVL positive isolates were comprised 37% (11/30) of methicillin-resistant isolates and 63% (19/30) of methicillin-susceptible S. aureus (MSSA) isolates. The results showed that 17 isolated carrying isoform H and 13 isolated carrying the R isoform.

Conclusion:

The PVL gene was predominantly found in MSSA isolates. There was no relation between PVL isoforms and the presence of mecA and SCCmec types.

Distribution of SCCmec Elements and Presence of Panton-Valentine Leukocidin in Methicillin-Resistant Staphylococcusepidermidis Isolated from Clinical Samples in a University Hospital of Isfahan City, Iran

INTRODUCTION

Coagulase Negative Staphylococcus (CoNS) is considered as a major pathogen of nosocomial infections among immunosuppressed patients.

AIM

The aim of this study was to identify the types of Staphylococcal Cassette Chromosome mec (SCCmec) and Panton-Valentine Leukocidin (PVL) gene among clinical Methicillin-Resistant S. epidermidis (MRSE) isolates collected from Isfahan.

MATERIALS AND METHODS

This cross-sectional study was performed from March 2014 to January 2015 at a tertiary care hospital of Isfahan, Iran. Antimicrobial susceptibility tests of S. epidermidis isolates were performed by the disc diffusion method. All the strains were screened for methicillin resistance based on resistance to cefoxitin (30 μg) disc and presence of mecA gene. Determination of SCCmec typing and PVL toxin gene were performed by PCR method. For categorical variables different groups were compared using the Chi-square test or Fisher exact test. A p-value of <0.05 was considered significant for all statistical tests.

RESULTS

The frequency of MRSE was 53.8% according to the presence of mecA gene. The overall resistance rate was high with ciprofloxacin (81.4%). PCR analysis showed that 17% (12/70) of MRSE isolate carried the PVL gene and 43% (30/70) were SCCmec type I; 11.4% (8/70) were type II; and 34.2% (24/70) were type IV, whereas, 11.4% (8/70) of the MRSE isolates could not be typed.

CONCLUSION

SCCmec type I was the major type of SCCmec, which indicates an emergence of this SCCmec type in the studied medical centers. Increased prevalence of SCCmec types in community is cause of an increase in antibiotic resistance among microorganisms.

The emergence of vancomycin-resistant Staphylococcus aureus in an intensive care unit in Kerman, Iran

Methicillin-resistant Staphylococcus aureus (MRSA) is a global threat to public health. This study is the first report of the emergence of vancomycin-resistant MRSA in Kerman, Iran. During a period of 15 months, a total of 205 clinical isolates of S. aureus were collected from three university hospitals affiliated with the Kerman University of Medical Science, Kerman, Iran. Screening of methicillin and vancomycin resistance was carried out by phenotypic methods. The resistance and virulence genes of vancomycin-resistant isolates were detected by polymerase chain reaction (PCR). Staphylococcal cassette chromosome mec (SCCmec) and spa typing were used for molecular typing of vancomycin-resistant isolates. Two S. aureus isolates were considered vancomycin-resistant by phenotypic and genotypic methods. Both isolates showed a minimum inhibitory concentration (MIC) ≥ 64 µg/ml and belonged to SCCmec III and spa type t030. Finding vancomycin-resistant S. aureus (VRSA) isolates represents a serious problem. More stringent infection control policies are recommended to prevent transmission of such life-threatening isolates in the hospital setting.

Review on Usage of Vancomycin in Livestock and Humans: Maintaining Its Efficacy, Prevention of Resistance and Alternative Therapy

Vancomycin is one of the “last-line” classes of antibiotics used in the treatment of life-threatening infections caused by Gram-positive bacteria. Even though vancomycin was discovered in the 1950s, it was widely used after the 1980s for the treatment of infections caused by methicillin-resistant Staphylococci, as the prevalence of these strains were increased. However, it is currently evident that vancomycin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci have developed for various reasons, including the use of avaparcin—an analog of vancomycin—as a feed additive in livestock. Therefore, prophylactic and empiric use of antibiotics and their analogues need to be minimized. Herein we discuss the rational use of vancomycin in treating humans, horses, farm animals, and pet animals such as dogs, cats, and rabbits. In present day context, more attention should be paid to the prevention of the emergence of resistance to antibiotics in order to maintain their efficacy. In order to prevent emergence of resistance, proper guidance for the responsible use of antimicrobials is indispensable. Therefore, almost all stakeholders who use antibiotics should have an in-depth understanding of the antibiotic that they use. As such, it is imperative to be aware of the important aspects of vancomycin. In the present review, efforts have been made to discuss the pharmacokinetics and pharmacodynamics, indications, emergence of resistance, control of resistance, adverse effects, and alternative therapy for vancomycin.