MOLECULAR TYPING OF METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS STRAINS BY PCR-RFLP OF SPA GENE: A REFERENCE LABORATORY PERSPECTIVE

Genotypically Confirmed Vancomycin-Resistant Staphylococcus aureus With vanB Gene Among Clinical Isolates in Kathmandu

Purpose

Methicillin-resistant Staphylococcus aureus, a common bacterial pathogen causes various infections. The acquisition of various antimicrobial-resistant genes in S. aureus has led to the transformation of this bacterium into a superbug. Vancomycin resistance among MRSA isolates is an emerging threat in empirical therapy of various infections. The study was hence aimed to find out the susceptibility status of S. aureus isolates toward vancomycin and detect mecA, vanA, and vanB genes among the isolates.

Methods

A total of 1245 clinical samples from the participants attending a tertiary care hospital in Kathmandu were processed. S. aureus isolated from the samples were subjected to antibiotic susceptibility patterns using the modified Kirby-Bauer disk diffusion method. Agar dilution method was used to determine the minimum inhibitory concentration of vancomycin. The antibiotic-resistant genes such as mecA, vanA, and vanB among S. aureus isolates were screened by a conventional polymerase chain reaction.

Results

Of 1245 samples, 80 S. aureus were identified. Out of which, 47.5% (38/80) were phenotypically confirmed MRSA isolates. mecA gene was detected in 84.2% (32/38) of MRSA isolates. 10.5% (4/38) were confirmed as vancomycin-intermediate S. aureus (VISA) by MIC determination. None of the isolates was positive for the vanA gene; however, 2 isolates were found to possess the vanB gene. The 2 isolates have vancomycin MIC breakpoints of 4 to 8 μg/mL.

Conclusion

There might be a spreading of vancomycin resistance among S. aureus, creating serious public health problems. Therefore, measures to limit vancomycin resistance should be considered in healthcare facilities as immediately as possible.

From Hospital to Community: Exploring Antibiotic Resistance and Genes Associated with Virulence Factor Diversity of Coagulase-Positive Staphylococci

Coagulase-positive staphylococcus (CoPS), including methicillin-resistant Staphylococcus aureus (MRSA), poses a global threat. The increasing prevalence of MRSA in Saudi Arabia emphasizes the need for effective management. This study explores the prevalence of virulence-associated genes and antibiotic resistance patterns in CoPS. Nasal swabs from 200 individuals were collected, and standard protocols were used for the isolation, identification, and characterization of CoPS and coagulase-negative staphylococci (CoNS). Additionally, antimicrobial susceptibility testing and PCR were conducted. Bacterial growth was observed in 58.5% of participants, with 12% positive for CoPS and 30% positive for CoNS. Hospital personnel carriers showed a significantly higher proportion of CoNS compared with non-hospital personnel carriers. Non-hospital personnel CoPS strains displayed higher sensitivity to oxacillin than hospital personnel strains. Cefoxitin exhibited the highest sensitivity among β-lactam antibiotics. All isolates were sensitive to trimethoprim/sulfamethoxazole, rifampin, and quinupristin. Polymerase chain reaction analysis detected methicillin resistance genes in both non-hospital and hospital personnel MRSA strains. The coa and spa genes were prevalent in MRSA isolates, while the Luk-PV gene was not detected. A high prevalence of CoPS and CoNS was observed in both non-hospital and hospital personnel carriers. Occupational risk factors may contribute to the differences in the strain distribution. Varying antibiotic susceptibility patterns indicate the effectiveness of oxacillin and cefoxitin. Urgent management strategies are needed due to methicillin resistance. Further research is necessary to explore additional virulence-associated genes and develop comprehensive approaches for CoPS infection prevention and treatment in Saudi Arabia.

Detection of Genes Encoding Microbial Surface Component Recognizing Adhesive Matrix Molecules in Methicillin-Resistant Staphylococcus aureus Isolated from Pyoderma Patients

Pyoderma is a common skin infection predominantly caused by Staphylococcus aureus. In addition to methicillin resistance, this pathogen is resistant to many other antibiotics, which ultimately limits the available treatment options. Therefore, the present study aimed to compare the antibiotic-resistance pattern, to detect the mecA gene and the genes encoding microbial surface component recognizing adhesive matrix molecules (MSCRAMMs) in S. aureus isolates. A total of 116 strains were isolated from patients suffering with pyoderma. Disk diffusion assay was opted to perform antimicrobial susceptibility testing of the isolates. Out of the isolates tested, 23-42.2% strains appeared susceptible to benzylpenicillin, cefoxitin, ciprofloxacin and erythromycin. While linezolid was found to be the most effective anti-staphylococcal drug, followed by rifampin, chloramphenicol, clindamycin, gentamicin and ceftaroline. Out of 116 isolates, 73 (62.93%) were methicillin-resistant S. aureus (MRSA). Statistically significant (p ≤ 0.05) differences in antibiotic resistance patterns between MRSA and methicillin-susceptible S. aureus (MSSA) were found. A significant association of resistance to ceftaroline, rifampin, tetracycline, ciprofloxacin, clindamycin, trimethoprim-sulfamethoxazole and chloramphenicol was found in MRSA. However, no significant difference was observed between MRSA and MSSA for resistance against gentamicin, erythromycin or linezolid. All cefoxitin-resistant S. aureus, nonetheless, were positive for the mecA gene. femA was found in all the MRSA isolates. Among other virulence markers, bbp and fnbB were found in all the isolates, while can (98.3%), clfA and fnbA (99.1%) were present predominately in MRSA. Thus, this study offers an understanding of antibiotic resistance MSCRAMMs, mecA, and femA gene patterns in locally isolated strains of S. aureus.

Methicillin-Resistant Staphylococcus aureus (MRSA): Prevalence, Antimicrobial Susceptibility Pattern, and Detection of mecA Gene among Cardiac Patients from a Tertiary Care Heart Center in Kathmandu, Nepal

Background:

Methicillin Resistant Staphylococcus aureus (MRSA) is a significant human pathogen associated with nosocomial infections. mecA in the S. aureus is a marker of MRSA. The main objective of this study was to detect mecA and vanA genes conferring resistance in S. aureus among cardiac patients attending Sahid Gangalal National Heart Centre (SGNHC), Kathmandu, Nepal between May and November 2019.

Methods:

A total of 524 clinical samples (blood, urine, sputum) were collected and processed. Bacterial isolates were tested for antimicrobial susceptibility test (AST) and screening for MRSA was carried out by cefoxitin disc diffusion method. Minimum inhibitory concentration (MIC) of vancomycin for MRSA was established by agar dilution method and chromosomal DNA was extracted and used in polymerase chain reaction targeting the mecA and vanA genes.

Results:

Out of 524 specimens, 27.5% (144/524) showed bacterial growth. Among 144 culture positive isolates, S. aureus (27.1%; 39/144) was the predominant bacteria. Among 39 S. aureus isolates, all isolates were found resistant to penicillin followed by erythromycin (94.9%; 37/39), gentamicin (94.9%; 37/39) and cefoxitin (87.2%; 34/39). Out of 39 S. aureus, 87.2% (34/39) were MRSA. Among 34 MRSA, 8.8% (3/34) were vancomycin intermediate S. aureus (VISA). None of the MRSA was resistant to vancomycin. All of the 3 VISA isolates were obtained from inpatients. Of 39 S. aureus, 82.1% (32/39) harbored mecA gene. Similarly, the entire VISA isolates and 94.1% (32/34) of the MRSA isolates were tested positive for mecA gene.

Conclusions:

High prevalence of MRSA among the cardiac patients indicates the increasing burden of drug resistance among bacterial isolates. Since infection control is the crucial step in coping with the burgeoning antimicrobial resistance in the country, augmentation of diagnostic facilities with routine monitoring of drug resistance is recommended.

Antimicrobial activities encountered by sulfur nanoparticles combating Staphylococcal species harboring sccmecA recovered from acne vulgaris

Over decades, sulfur has been employed for treatment of many dermatological diseases, several skin and soft tissue, and Staphylococcus infections. Because of its abuse, resistant bacterial strains have emerged. Nanotechnology has presented a new horizon to overcome abundant problems including drug resistance. Nano-sized sulfur has proven to retain bactericidal activity. Consequently, the specific aims of this study are exclusively directed to produce various sulfur nanoparticles formulations with control of particle size and morphology and investigate the antibacterial activity response specifically classified by the category of responses of different formulations, for the treatment of acne vulgaris resistant to conventional antibiotics. In this study, we produced uncoated sulfur nanoparticles (SNPs), sulfur nano-composite with chitosan (CS-SNPs), and sulfur nanoparticles coated with polyethylene glycol (PEG-SNPs) and evaluate their bactericidal impact against Staphylococcus aureus and Staphylococcus epidermidis isolated from 173 patients clinically diagnosed acne vulgaris. Accompanied with molecular investigations of ermB and mecA resistance genes distribution among the isolates. Sulfur nanoparticles were synthesized using acid precipitation method and were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), energy dispersed x-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). Moreover, agar diffusion and broth micro-dilution methods were applied to determine their antibacterial activity and their minimum inhibitory concentration. PCR analysis for virulence factors detection. Results: TEM analysis showed particle size of SNPs (11.7 nm), PEG-SNPs (27 nm) and CS-SNPs (33 nm). Significant antibacterial activity from nanoparticles formulations in 100% dimethyl sulfoxide (DMSO) with inhibition zone 30 mm and MIC at 5.5 µg/mL. Furthermore, the prevalence of mecA gene was the most abundant among the isolates while ermB gene was infrequent. Conclusions: sulfur nanoparticles preparations are an effective treatment for most Staphylococcus bacteria causing acne vulgaris harboring multi-drug resistance virulence factors.

Characteristics of Staphylococcus aureus Isolated From Clinical Specimens in a Tertiary Care Hospital, Kathmandu, Nepal

Introduction

Methicillin resistant Staphylococcus aureus (MRSA) is a major human pathogen associated with nosocomial and community infections. mecA gene is considered one of the important virulence factors of S. aureus responsible for acquiring resistance against methicillin. The main objective of this study was to explore the prevalence, antibiotic susceptibility pattern, and mec A gene.

Methods

A total of 39 isolates of S. aureus were isolated from 954 clinical specimens processed in Microbiology laboratory of Himal Hospital, Kathmandu. Antimicrobial susceptibility test (AST) was performed by Kirby-Bauer disc diffusion method using cefoxitin, and performed Polymerase Chain Reaction (PCR) for amplification of mecA gene in MRSA isolates.

Results

Out of 954 clinical samples, (16.2%; 153/954) samples had bacterial growth. Among 153 culture positive isolates, 25.5% (39/153) were positive for S. aureus. Among 39 S. aureus (61.5%; 24/39) were multiple drug resistant (MDR). On AST, amoxicillin was detected as the least effective while vancomycin was the most effective. The prevalence of methicillin resistance was 46% (18/39) of which 72.2% (13/18) were positive for mecA gene in PCR assay.

Conclusion

One in 4 culture positive isolates from the clinical specimens were S. aureus, of which almost two-thirds were MDR. Around half of the MDR showed MRSA and significant proportion of them were positive for mecA gene. This study concludes that the mecA gene is solely dependent for methicillin resistance in S. aureus but the presence of gene is not obligatory. PCR detection of the mecA gene is reliable, valid and can be suggested for the routine use in diagnostic laboratories.

A Systemic Literature Review and Meta-Analysis Reporting the Prevalence and Impact of Methicillin-Resistant Staphylococcus aureus Infection in India

Aim and objective

This systematic review and meta-analysis was conducted to assess the prevalence, burden and epidemiology of methicillin-resistant S. aureus (MRSA). This systemic review was also aimed to highlight the challenges in the diagnosis and management of methicillin-resistant S. aureus (MRSA) in India (for all age groups). We also examined the published literature on the available treatment options and the role of prevention in the management of MRSA in India. By summarizing the currently available data, our objectives were to highlight the need for the prevention of MRSA infections and also emphasize the role of vaccination in the prevention of MRSA infections in India.

Methodology

Electronic databases such as PubMed and databases of the National Institute of Science Communication and Information Resources and Indian Council of Medical Research Embase were searched for relevant literature published from 2005/01/01 to 2020/05/13 in English language, according to the predefined inclusion and exclusion criteria. A manual search was also conducted using the key term "MRSA 'or' Methicillin Resistant Staphylococcus aureus 'and' India." An independent reviewer extracted data from the studies using a structured Microsoft Excel spreadsheet, and a meta-analysis of proportion for MRSA prevalence with a corresponding 95% confidence interval (CI) for all included individual studies were performed.

Result

A total of 34 studies involving 16 237 patients were included in the final meta-analysis. The pooled proportion of patients with MRSA infection was 26.8% (95% CI: 23.2%-30.7%). The MRSA infection was more prevalent among male patients (60.4%; 95% CI: 53.9%-66.5%) as compared to female patients (39.6%; 95% CI: 33.5%-46.1%), while the prevalence of MRSA was higher among adults (18 years and above; 32%; 95% CI: 5%-80%) in comparison to pediatric patients (0-18 years; 68%; 95% CI: 20%-94.8%). The degree of heterogeneity was found to be significant.

Conclusion

The prevalence of MRSA in India was relatively high at 27% with a higher proportion observed among men aged >18 years. The high prevalence of MRSA infections in India necessitates the implementation of surveillance and preventive measures to combat the spread of MRSA in both hospital and community settings.

Novel determination of spa gene diversity and its molecular typing among Staphylococcus aureus Iraqi isolates obtained from different clinical samples

Staphylococcus aureus is the most frequent agent causing nosocomial infections in Baghdad hospitals. This study aimed to determine S. aureus methicillin resistance, spa gene typing and phylogenic analysis in Iraqi S. aureus isolates. Two hundred samples including clinical (n = 100) and environmental (n = 100) specimens were collected. S. aureus isolates were identified using multiplex PCR amplification of femA and mecA (for methicillin-resistant S. aureus (MRSA) strains) genes. The spa gene was also amplified. Sequence alignment and identification of spa types was then obtained. Of 74 studied S. aureus isolates, 61 (82.43%) harboured the mecA gene (p < 0.001). A spa gene variation was detected in 41 (67.2%) of 61 (p 0.0011) MRSA and 6 (46.15%) of 13 methicillin-susceptible S. aureus isolates. Amino acid sequence analysis revealed a great change in amino acid pattern among local isolates compared to National Center for Biotechnology Information control. Some of the MRSA isolates had high-level similarity with t10214. No genetic relationship with the infection sources was observed. None of the environmental isolates had spa gene variations. Most S. aureus isolates were MRSA. The spa gene variations was significantly higher among clinical isolates. spa sequencing showed different tandem repeats in local MRSA isolates compared to global spa types. We conclude that there was no outbreak in hospital settings in the city of Baghdad. However, our data suggest that isolates from the hospital environment are highly clonal.

Molecular detection and typing of methicillin-resistant Staphylococcus aureus and methicillin-resistant coagulase-negative staphylococci isolated from cattle, animal handlers, and their environment from Karnataka, Southern Province of India

Background and Aim:

Methicillin-resistant staphylococci are among the emerging pathogens which have become a threat to both human and animal health. The present investigation intended to examine the occurrence and the molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MRCoNS) recovered from cattle, its handlers, and their environment.

Materials and Methods:

A total of 666 specimens were subjected to culture method and genus-specific polymerase chain reaction (PCR) for the identification of Staphylococcus. Methicillin resistance was substantiated by PCR identification of mecA and mecC resistance determinants. Species-specific identification of mecA positive isolates was conducted by multiplex PCR. The unidentified species were deciphered by 16S rRNA gene sequencing approach. The mecA positive isolates were further characterized by staphylococcal cassette chromosome mec (SCCmec) typing and multilocus sequence typing (MLST).

Results:

Duplex PCR identified 728 Staphylococcus isolates, of which 66 (9%) were positive for mecA gene. MRSA constituted 24% of the total mecA positive isolates. Among MRCoNS, Staphylococcus epidermidis (42%), and Staphylococcus haemolyticus (11%) were the most common species identified. Overall, 47% of the mecA positive isolates belonged to SCCmec type V. MLST analysis showed eight different sequence types (STs) among MRSA isolates of which five were novel STs. Among methicillin-resistant S. epidermidis, 19 different STs were found, of which nine novel STs were detected.

Conclusion:

The increase in the prevalence of mecA positive staphylococci, especially MRCoNS in cattle is a great concern in view of their transmission potential. Hence, continuous monitoring and molecular characterization of methicillin-resistant staphylococci should be elucidated in human and animal sectors so as to prevent the spread of these resistant pathogens.

Molecular characterisation of Staphylococcus aureus using spa typing as a diagnostic tool in Haryana, India

Background

Staphylococcus aureus is one of the top six most common etiologic agents of nosocomial, community and livestock acquired bacterial infections. These infections although initially were described as a major problem in hospitals have now also become a serious threat in community not only in India but also worldwide. Its prevalence varies depending on the health-care setting, country or a particular region. Thus to better understand the epidemiology of methicillin-resistant S. aureus (MRSA) in a particular geographical location, it is important to study the variations in the population using molecular tools.

Methods

This prospective study was carried out in the Department of Microbiology of Shree Guru Gobind Singh Tricentenary (SGT) Medical College. Staphylococcal protein A (spa) typing was done on 250 S. aureus isolates obtained from various clinical specimens including pus, wound swabs, urine, catheters, blood and cerebrosspinal fluid from both indoor and outdoor patients of SGT Hospital, Budhera, Gurgaon.

Results

The selected region of the spa gene of all 250 isolates which includes 87 MRSA and 163 methicillin-susceptible S. aureus were amplified. The spa gene was detected in 248 out of 250 isolates (99.2%), whereas in 2 isolates (0.8%), it remained undetected and referred as non-typable isolates. The 248 S. aureus isolates were typed into 39 spa types, which clustered into six different spa clonal clusters and eight singletons.

Conclusion

High diversity observed within S. aureus isolates indicated that many different strains circulate in the study region or in the hospital. The results would contribute in the understanding of epidemiology related to S. aureus spread and prevention.

Molecular typing of Staphylococcus aureus of different origins based on the polymorphism of the spa gene: characterization of a novel spa type

The present study was conducted to determine the molecular diversity of Staphylococcus aureus strains isolated from human, bovine and food samples based on the polymorphism of the spa gene. A total of 208 S. aureus isolated from human, bovine raw milk and food samples were assessed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and single locus sequence typing (SLST) methods, followed by determination of spa types using Ridom SpaServer. Altogether, 15 distinct RFLP patterns were recorded (I-XV). The highest heterogeneity was observed among S. aureus isolated from humans, whereas most of bovine and food S. aureus isolates indicated certain RFLP patterns. Although most of the isolates from patients showed RFLP pattern I, none of the S. aureus isolated from carriers had this spa pattern. Besides, the results of SLST led to the characterization of 16 spa types, and one of them was a novel spa type which has been registered in Ridom SpaServer for the first time and designated as type t16929. Determination of a high number of shared RFLP patterns between human and food S. aureus isolates indicated possible transmission of S. aureus and the source of food contamination. Thus, effective hygiene measures should be taken to break transmission routes. However, it seems that S. aureus isolated from patients, carriers and bovine should be considered in a different way, since some isolates had similar patterns, while the others showed their own specific pattern.

Polymorphism in spa gene of Staphylococcus aureus from bovine subclinical mastitis

Aim:

The virulence-associated protein-A of Staphylococcus aureus, encoded by spa gene shows a variation in length in different strains. In this study, the spa gene variation in S. aureus strains was studied which were isolated from subclinical cases of bovine mastitis.

Materials and Methods:

About 38 isolatesof S. aureus were recovered from Holstein–Friesian (HF) crossbred (n=16) and Rathi cattle (n=22) with subclinical mastitis as per standard procedures, and these isolates were subjected to amplification of spa gene (X-region) by polymerase chain reaction and calculation of number of tandem repeats were done.

Results:

Of the 16 isolates from H-F crossbred cattle, all with the exception of one isolate produced spa amplicon. Seven isolates produced amplicons of 200 bp, one produced 160 bp, and other seven produced spa amplicon of 150 bp with calculated number of 6, 5, and 4 repeats, respectively, whereas nine different types of amplicons were produced by 22 S. aureus isolates from Rathi cattle, viz., 280, 250, 240, 200, 190, 180, 170, 150, and 140 bp with 10, 8, 8, 6, 6, 6, 5, 4, and 4 repeats, respectively. One of the isolates from Rathi cattle produced two spa amplicons (150 and 190 bp).

Conclusion:

A greater polymorphism was observed in the S. aureus isolates from Rathi cattle than from H-F crossbreds with subclinical mastitis.

Typing of Staphylococcus aureus obtained from mastitic milk of cattle and buffalo on the basis of two virulence-associated genes (spa and clfA)

Aim:

The present study was undertaken to type Staphylococcus aureus isolates from cattle and buffalo mastitic milk on the basis of spa (X-region) and clfA genes, both responsible for producing virulence factors.

Material and Methods:

In the present investigation S. aureus isolates were isolated as per standard protocols. Typing of S. aureus was carried out by molecular detection of spa and clfA gene by polymerase chain reaction.

Results:

All the 32 isolates from cattle (16) and buffalo (16) were divisible into seven spa types with amplicon sizes ranging between 120 and 380bp. The cattle isolates produced seven different spa amplicons of 120, 150, 200, 250, 280, 300, and 330 bp with 3, 4, 6, 8, 10, 11 and 12 number of tandem repeats, respectively whereas buffalo isolates were divisible into five spa types with amplicons of 150, 200, 250, 330 and 380 bp having calculated number of repeats of 5, 7, 9, 12, and 14, respectively. Of the total isolates, 24 were considered pathogenic on the basis of more than seven number of tandem repeats. In the present investigation, clfA gene was amplified in 27 isolates from cattle and buffalo producing two different amplicons of 900 and 1000 bp sizes showing polymorphism. The most (71.80%) of the isolates produced amplicons of 900 bp while amplicon size of 1000 bp was produced by four (12.5%) of the isolates.

Conclusion:

The presence of these genes with a wide degree of polymorphism confirmed the pathogenic potential of S. aureus and their association with clinical manifestations in mastitis among cattle and buffalo.

Molecular and phenotypic characterization of methicillin-resistant Staphylococcus aureus isolates from a tertiary hospital in the Philippines

Background

Methicillin-resistant Staphylococcus aureus (MRSA) poses a major threat to public health worldwide. There are relatively few studies addressing the molecular epidemiology of MRSA in the Philippines.

Methods

This study characterized MRSA isolates in terms of their antimicrobial susceptibility profile, the SCCmec type, and the presence of lukF-lukS genes for Panton-Valentine leukocidin (PVL) and determined the relatedness of the isolates by random amplified polymorphic DNA (RAPD)-polymerase chain reaction (PCR).

Results

A total of 236 S. aureus were isolated from clinical specimens of the Makati Medical Center in Makati City, Philippines, between January 2013 and June 2013, and 108 or 45.76 % were found to be MRSA. Results showed that the MRSA strains were resistant to trimethoprim-sulfamethoxazole (20.37 %), azithromycin (10.19 %), gentamicin (5.56 %), and linezolid (4.63 %), while all were susceptible to vancomycin, nitrofurantoin, levofloxacin, minocycline, rifampin, and tetracycline. One isolate was found positive for inducible clindamycin resistance. All of the 108 MRSA strains were confirmed to carry the mecA and SCCmec genes, while the PVL genes were detected in 41 (38 %) of the isolates. Ninety-six isolates (89 %) carried SCCmec type IV, while the remaining isolates carried SCCmec type I (11 isolates) or type III (one isolate).

Conclusion

This study is the first to present a comprehensive MRSA surveillance data with molecular characterization in a tertiary hospital in the Philippines.

Occurrence, Virulence Factors, Antimicrobial Resistance, and Genotyping of Staphylococcus aureus Strains Isolated from Chicken Products and Humans

Staphylococcus aureus in food is a consequence of inadequate hygienic handling and processing, posing a potential risk to public health. The current study aimed to characterize virulence factors, as well as antimicrobial resistance of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) isolated from retail chicken products and hand swabs from vendors in Egypt. In addition, genetic relatedness of the isolates from chicken and humans was evaluated by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) using protein A as a target. A total of 110 samples were collected from chicken products (n = 80) and vendors (n = 30). Overall, 30 (37.5%) chicken products samples were positive for S. aureus, whereas hand swabs from meat handlers revealed that 18 (60%) were positive. Ten MRSA strains were characterized by the presence of the mecA gene, comprising seven isolates from chicken and three from humans. Virulence-associated factors were evaluated by PCR, revealing that 31.3% of S. aureus isolates harbored the Panton-Valentine leukocidin (PVL) gene, whereas 10.4% were positive for the sea and sed genes each, and only two isolates were positive for γ-hemolysin-associated gene. Genotyping using spa PCR-RFLP showed identical restriction banding patterns of MRSA isolates of human and chicken meat origin, indicating the genetic relatedness of the isolates. To the best of our knowledge, this is the first study to characterize PVL-positive MRSA from chicken products and to utilize spa-RFLP for evaluating the genetic relatedness between MRSA of human and chicken origin in Egypt.

Resistant Strains of Enterotoxigenic Staphylococcus aureus; Unknown Risk for Multiple Sclerosis Exacerbation

Background:

Despite all advances in neurological sciences, there are unknown aspects in the epidemiology of multiple sclerosis (MS). Based on this hypothesis, the enterotoxigenic strains of Staphylococcus aureus (S. aureus) are possible risk factors for exacerbations of MS.

Objectives:

The present study was carried out to investigate the role of resistant strains of enterotoxigenic S. aureus in MS exacerbation.

Materials and Methods:

Two-hundred nasal swab samples were collected from non-MS (n = 80), MS stable (n = 60) and MS exacerbation (n = 60) groups. Samples were cultured and those that were S. aureus-positive were analyzed for the presence of enterotoxins, using polymerase chain reaction (PCR). Antimicrobial susceptibility was performed using disk diffusion method.

Results:

Ninety out of 200 nasal samples (45%) were positive for S. aureus. The highest levels of nasal colonization were seen in MS exacerbation group (68.33%). The most commonly detected enterotoxins were sea (30%), sec (15.55%) and seb (11.11%). There were significant differences between S. aureus colonization and type of samples (P = 0.026) and, also, between type of samples and prevalence of enterotoxins (P = 0.022). The highest levels of enterotoxigenic genes were seen in MS exacerbation group. The S. aureus strains had the highest levels of resistance against tetracycline (80%), ampicillin (72.22%), methicillin (66.66%), erythromycin (66.66%), oxacillin (63.33%), trimethoprim-sulfamethoxazole (61.11%) and cotrimoxazole (55.55%).

Conclusions:

Our findings should raise awareness about the role of sea and sec enterotoxins, in resistant strains of S. aureus, as a risk factor for MS exacerbation. It is better to keep MS patients away from polluted environments of hospitals and health centers.

Evaluation of LAMP Assay Using Phenotypic Tests and Conventional PCR for Detection of nuc and mecA genes Among Clinical Isolates of Staphylococcus spp

INTRODUCTION

The purpose of this study is to develop a nuc and mecA gene specific Loop-mediated isothermal Amplification (LAMP) assay for rapid identification and detection of methicillin resistant Staphylococcus aureus among clinical isolates.

MATERIALS AND METHODS

A total of 100 (70 from pus and 30 from blood), clinical isolates of Staphylococcus spp were screened for the nuc gene to differentiate between S.aureus and Coagulase negative Staphylococci (CONS) by a nuc gene specific LAMP assay. The isolates were also screened for the presence of the mec Agene by the mecA specific LAMP assay. The results were compared with the phenotypic identification and methicillin resistance by Vitek-2 system (bioMérieux, Marcy l'Etoile, France) and conventional PCR.

RESULTS

Among 100 Staphylococcus isolates, there were 82 (82%) Staphylococcus aureus isolates and 18 (18%) coagulase negative Staphylococcus as detected by the Vitek 2, conventional PCR and the LAMP assay using the nuc gene. The mecA gene was detected by the LAMP assay in 56(56%) isolates (44 Methicillin resistant Staphylococcus aureus (MRSA) and 12 Methicillin resistant coagulase negative Staphylococcus (MRCONS), which were also identified by the Vitek 2 and conventional PCR as methicillin resistant. The results of the LAMP assay were available within 90min as compared to the Vitek 2 results (18- 24hours) and conventional PCR (3-4 hours).

CONCLUSION

The present study proved that LAMP assay can be used for the simultaneous differentiation of Staphylococcal spp and detection of methicillin resistance.

Absence of the mecA Gene in Methicillin Resistant Staphylococcus aureus Isolated from Different Clinical Specimens in Shendi City, Sudan

Absolute dependence on mecA gene as the defining standard in determining the resistance of S. aureus to methicillin became the subject of distrust by many researchers. The present study aimed to determine the frequency of mecA gene in methicillin resistant S. aureus (MRSA) isolates using polymerase chain reaction and to correlate its presence to conventional method. In this regard, two hundred S. aureus isolates were collected from patients with different diseases attending different hospitals in Shandi City, Sudan. Phenotypic Kirby-Bauer method confirmed the existence of methicillin resistant S. aureus in 61.5% of the subjected isolates with MICs ranging from 4 μg/mL to 256 μg/mL when using E-test. However, when amplifying a 310 bp fragment of the mecA gene by PCR, twelve out of the 123 MRSA isolates (9.8%) were mecA negative, whereas all the 77 methicillin sensitive S. aureus (MSSA) were mecA negative. In conclusion, this study drew attention to the credibility of the mecA gene and its usefulness in the detection of all MRSA strains without referring to the traditional methods. Hence, it is highly recommended to consider alternative mechanisms for β-lactam resistance that may compete with mecA gene in the emergence of MRSA phenomenon in the community.

Staphylococcus aureus Typing by Digestion of Protein A Coding Gene Using Bsp143I

BACKGROUND

Protein A is the virulence factors of Staphylococcus aureus rolling in its pathogenesis, and its gene is used for typing. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) with different enzymes has been used for this action.

OBJECTIVES

In this study, we used Bsp143I enzyme for digestion of the gene, coding protein A (spa gene) in S. aureus. The bacteria were isolated from patients and healthy carriers in Gorgan, north of Iran.

PATIENTS AND METHODS

DNAs of 128 S. aureus subjects (53 from healthy carriers and 75 from patients) were extracted and amplified using specific primers of the spa gene. The product was digested by Bsp143I enzyme and its pattern was assessed by gel electrophoresis.

RESULTS

There were seven spa types among the tested S. aureus samples, among which six types differed in the repeated X region of the spa gene, but the seventh type had a deletion on one of BSP143I restriction sites. The frequency of spa types among isolated S. aureus samples as well as healthy carriers was six and five, respectively. S. aureus isolated from wounds showed the most diverse spa types (five) among clinical samples. Types 1, 2 and 4 were observed in all clinical samples, while only one case of type 3 was identified among patients, whereas this type constituted over 32% of the isolates among carriers. We found seven and four spa types among methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) isolates, respectively.

CONCLUSIONS

Our results showed that typing the spa gene using PCR-RFLP using Bsp143I was an acceptable method for typing S. aureus. Furthermore, this survey showed that the types in healthy carriers and MSSA were more variable than patient and MRSA isolates, respectively. We used the Bsp143I enzyme, which was not used in any previous studies on the spa gene. The results of this study suggested that we can use PCR-RFLP of spa gene by Bsp143I for molecular typing and sequencing of S. aureus, instead of relatively expensive methods. This method is relatively rapid and inexpensive, and can be accomplished in centers with conventional molecular facilities.

Meticillin-resistant Staphylococcus aureus isolated from Iranian hospitals: virulence factors and antibiotic resistance properties

Staphylococcus aureus is an important opportunistic pathogen responsible for a variety of diseases. Indiscriminate prescription of antibiotics caused severe antibiotic resistance especially against commonly used drugs. The present investigation was carried out to study the distribution of Panton-Valentine Leukocidin gene, SCCmec types and antibiotic resistance properties of meticillin-resistant Staphylococcus aureus isolated from Iranian hospitals. A total of 132 clinical specimens were collected from two major Iranian hospitals. Samples were cultured and their positive results were subjected to several PCR methods. The patterns of antibiotic resistance were studied using the disk diffusion method. We found that 66 out of 132 samples (50%) were positive for Staphylococcus aureus. The most commonly infected samples were superficial and surgical wounds (66.12%). The incidence of mecA, tetK, ermA, ermC, tetM, aacA-D, linA, msrA, vatA, vatC and vatB antibiotic resistance genes were 80.30%, 34.84%, 30.30%, 25.75%, 24.24%, 19.69%, 7.57%, 7.57%, 6.06%, 3.03% and 1.51%, respectively. Totally, 40.90% of isolates harbored the Panton-Valentine Leukocidin gene. Of 53 mec positive strains, the distribution of SCCmec V, SCCmec III, SCCmec IVa, SCCmec IVc and SCCmec IVb were 28 (52.83%), 13 (24.52%), 6 (11.32%), 4 (7.54%) and 2 (3.77%), respectively. All isolates were resistant to penicillin, cephalothin, cefazoline and ceftriaxone. The high levels of Staphylococcus aureus resistance against commonly used antibiotics as well as high presence of SCCmec types of meticillin-resistant virulent strains of Staphylococcus aureus suggest that infections with these strains require more advanced hospital care with emerging demand for novel antibiotics.

Molecular Typing of Methicillin Resistant Staphylococcus aureus Clinical Isolates on the Basis of Protein A and Coagulase Gene Polymorphisms

Increased frequency of methicillin-resistant Staphylococcus aureus (MRSA) in hospitalized patients requires rapid and reliable characterization of isolates for control of MRSA spread in hospitals. This study evaluated polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) as a molecular typing technique for MRSA strains on the basis of protein A (spa) and coagulase (coa) gene polymorphisms to verify their ability in assessing the relatedness of isolates. Seventy-five MRSA isolates, from different ICUs of Alexandria University Main Hospital, were characterized using antibiotyping and PCR-RFLP analysis of coa and spa genes. Thirty-two antibiotypes were identified. coa gene PCR generated 3 types and 10 subtypes of band patterns. HaeIII restriction digestion of amplified coa gene products produced 5 major banding patterns and 12 subtypes. spa gene PCR products generated 4 major and 11 minor types, and their HaeII restriction digestion showed 5 major and 12 minor banding patterns. The combined coa and spa RFLP patterns generated 22 combined R types. Typing using coa PCR and PCR-RFLP had the same discriminatory index (DI) value (0.64), which was comparable to that of both spa PCR and PCR-RFLP techniques (0.68). The combined grouping increased the DI value to 0.836. The current study revealed that testing for multiple gene polymorphisms is more useful for local epidemiologic purposes.

Bacteriophage types of methicillin-resistant Staphylococcus aureus in a tertiary care hospital

BACKGROUND

Phage typing had been utilised extensively to characterise methicillin-resistant Staphylococcus aureus (MRSA) outbreak strains in the past. It is an invaluable tool even today to monitor emergence and dissemination of MRSA strains.

AIMS

The aim of this study was to determine the prevalent phage types of MRSA in south India and the association between phage types, antibiotic resistance pattern and risk factors.

METHOD

A total of 48 non-duplicate MRSA strains recovered from various clinical samples during January to December, 2010 were tested against a panel of anti-staphylococcal antibiotics. Phage typing was carried out at the National Staphylococcal Phage Typing Centre, New Delhi. Out of 48, 32 hospitalised patients were followed up for risk factors and response to empirical and post sensitivity antibiotic therapy. The risk factors were compared with a control group of 30 patients with methicillin sensitive Staphylococcus aureus (MSSA) infection.

RESULTS

Amongst the five prevalent phage types, 42E was most common (52%), followed by a non-typable variant (22.9%), 42E/47/54/75 (16.6%), 42E/47 (6.2%) and 47 (2%). Phage type 42E was the predominant strain in all wards and OPDs except in the ICU where 42E/47/54/75 was most common. Although not statistically significant, strain 42E/47/54/75 (n=8) showed higher resistance to all drugs, except ciprofloxacin and amikacin, and were mostly D-test positive (87.5%) compared to the 42E strain (32%). Duration of hospital stay, intravenous catheterisation and breach in skin were the most significant risk factors for MRSA infection.

CONCLUSION

We found MRSA strain diversity in hospital wards with differences in their antibiotic susceptibility pattern. The findings may impact infection control and antibiotic policy significantly.

A novel multiplex PCR for molecular characterization of methicillin resistant Staphylococcus aureus recovered from Jeddah, Kingdom of Saudi Arabia

BACKGROUND

Molecular characterization of staphylococcal cassette chromosome mec (SCCmec) types of methicillin-resistant Staphylococcus aureus (MRSA) is very essential for studying the epidemiology of MRSA.

OBJECTIVES

This study reports two multiplex PCR for molecular typing of MRSA collected from Jeddah, Kingdom of Saudi Arabia.

MATERIALS AND METHODS

A total of 101 clinical isolates of strains were collected from major hospital laboratories and public health centres, Jeddah, Kingdom of Saudi Arabia during the period from August 2009 to May 2011. All the strains were tested phenotypically by conventional methods and genotypically by a novel multiplex PCR targeting at the same time S. aureus 16S rRNA, Panton - valentine leucocidin (PVL) and mecA resistance genes. All the strains were tested also by multiplex PCR for typing of SCC mec types.

RESULTS

All the 101 strains previously identified phenotypically as S. aureus with bacteriological examination were positive for amplification of 756 base pair fragments specific for 16S rRNA of S. aureus. Moreover, all the strains were positive for amplification of 1339 base pair fragments specific for mecA gene, while only 38 strains (37.6%) showed positive amplification of 433 base pair fragments specific for PVL gene. The most predominant SCC mec type among the examined isolates is type V 43 (42.5) followed by SCCmec type III 39 (38.6%).

CONCLUSION

The newly modified multiplex PCR is rapid and sensitive method for detection of MRSA. Moreover, the most predominant SCC mec type among the examined isolates from Jeddah, King Saudi Arabia is type V (42.5%), followed by Type III (38.6%).

Typing of Methicillin resistant Staphylococcus aureus: a technical review

Increasing prevalence of Methicillin-resistant Staphylococcus aureus (MRSA) worldwide is a growing public health concern. MRSA typing is an essential component of an effective surveillance system to describe epidemiological trends and infection control strategies. Current challenges for MRSA typing are focused on selecting the most appropriate technique in terms of efficiency, reliability, ease of performance and cost involved. This review summarises the available information on application, potential and problems of various typing techniques in discriminating the strains and understanding the epidemiology of MRSA strains. The phenotypic methods in general are easier to perform, easier to interpret, cost effective and are widely available, however less discriminatory. The genotypic methods are expensive and technically demanding, however more discriminatory. Newer technologies involving sequencing of various genes are coming up as broadly applicable and high throughput typing systems. Still there is no consensus regarding the single best method for typing of MRSA strains. Phage typing is recommended as first line approach in epidemiological investigation of MRSA strains. PFGE remains the gold standard for characterisation of outbreak strains. DNA sequencing methods including MLST, spa typing, SCCmec typing and toxin gene profile typing are more practical methods for detecting evolutionary changes and transmission events. The choice of typing technique further depends on the purpose of the study, the facilities available and the utility of data generated to answer a desirable research question. A need for harmonisation of typing techniques by following standard protocols is emphasised to establish surveillance networks and facilitate global MRSA control.

Characterization of Staphylococcus aureus isolates from white-brined Urfa cheese

The aim of this study was to investigate the presence of Staphylococcus aureus and staphylococcal enterotoxin (SE) genes in Urfa cheese samples and to characterize the enterotoxigenic potential of these isolates. From a total of 127 Urfa cheese samples, 53 isolates (from 41.7% of the samples) were identified by a species-specific PCR assay as S. aureus. Of these isolates, 40 (75.5%) gave positive PCR results for the 3' end of the coa gene. The coa-positive S. aureus strains were characterized for their population levels and enterotoxigenic properties, including slime factor, β-lactamase, antibiotic susceptibilities, production of the classical SEs (SEA through SEE), in both cheese and liquid cultures by enzyme-linked immunosorbent assay (ELISA) and for the presence of specific genes, including classical SE genes (sea through see), mecA, femA, and spa, by PCR. The genetic relatedness among the coa-positive S. aureus isolates was investigated by PCR-based restriction fragment length polymorphism (RFLP) analysis and the 23S rRNA gene spacer. The 23S rRNA gene spacer and coa RFLP analysis using AluI and Hin6I revealed 14 different patterns. SEB, SEC, and SEA and SEE were detected by ELISA in three cheese samples. Fourteen S. aureus strains harbored enterotoxin genes sea through see, and three strains carried multiple toxin genes. The most commonly detected toxin gene was sec (25% of tested strains). Of the 40 analyzed S. aureus strains, 3 (7.5%) were mecA positive. Based on tandem repeats, four coa and spa types were identified. The results of this study indicate that S. aureus and SEs are present at significant levels in Urfa cheese. These toxins can cause staphylococcal food poisoning, creating a serious hazard for public health.

Specific detection of Salmonella enterica and Escherichia coli strains by using ELISA with bacteriophages as recognition agents

The use of bacteriophages, instead of antibodies, in the ELISA-based detection of bacterial strains was tested. This procedure appeared to be efficient, and specific strains of Salmonella enterica and Escherichia coli could be detected. The sensitivity of the assay was about 10⁵ bacterial cells/well (10⁶/ml), which is comparable with or outperforms other ELISA tests detecting intact bacterial cells without an enrichment step. The specificity of the assay depends on the kind of bacteriophage used. We conclude that the use of bacteriophages in the detection and identification of bacteria by an ELISA-based method can be an alternative to the use of specific antibodies. The advantages of the use of bacteriophages are their environmental abundance (and, thus, a possibility to isolate various phages with different specificities) and the availability of methods for obtaining large amounts of phage lysates, which are simple, rapid, cheap, and easy.

Spa Diversity among MRSA and MSSA Strains of Staphylococcus aureus in North of Iran

Protein A of Staphylococcus aureus is a pathogenic factor whose encoding gene, spa, shows a variation in length in different strains. In this study the spa gene variation in S. aureus isolated from healthy carriers and patients was studied, We also compared this variation among MRSA with MSSA strains. 208 strains of Staphylococcus aureus which we were isolated from Gorgan, north of Iran were studied, 121 cases from patients and 87 cases from healthy carriers, 59 out of them were MRSA and 149 MSSA. Samples DNA were extracted and amplified by specific primer of spa gene. In 4 (3.8%) strains of them no spa gene was detected, and 10.6% had a dual band (1200 and 1400 bp). In strains with one band, the length of spa gene differed from 1150 to 1500 bp. The most prevalent length was 1350–1400 bp (37%). The frequencies of short spa bands (1150–1200 bp) in patients strains were significantly higher. In 4 (3.8%) strains of them no spa gene was detected, and 10.6% had a dual band (1200 and 1400 bp). In strains with one band, the length of spa gene differed from 1150 to 1500 bp. The most prevalent length was 1350–1400 bp (37%). The frequencies of short spa bands (1150–1200 bp) in patients strains were significantly higher. The spa gene length of 1350–1400 bp in MSSA was more than in MRSA strains (P < .05). The average length of spa in isolated strains from urinary tract infections was more than others. It is concluded that the length of spa gene depends either on resistance to Methicillin or the source of S. aureus isolation.