Detection of methicillin resistance in Staphylococcus aureus by polymerase chain reaction and conventional methods: a comparative study

Phenotypic and genotypic characterization of methicillin resistant Staphylococcus aureus associated with pyogenic infections

Background and Objectives

Staphylococcal infections are one of the major infectious diseases affecting globally in spite of advances in development of antimicrobial agents. Knowledge and awareness about the local pattern and prevalence of MRSA infections plays a key role in treatment. The aim of this study was to identify MRSA strains by phenotypic and genotypic methods and to analyze the antibiotic susceptibility pattern of MRSA strains from patients attending a tertiary care hospital.

Materials and Methods

This study was conducted over a period of 1 year, where 296 isolates of Staphylococcus aureus were isolated from various clinical specimens. The isolated strains were examined for antibiotic susceptibility by the modified Kirby Bauer disc diffusion method. Methicillin resistance was detected by cefoxitin disk diffusion test.

Results

A total of 104 isolates were found to be MRSA and 192 were found to be MSSA. Among the 104 MRSA isolates, 10 strains that were multidrug resistant were subjected to 16S rRNA gene sequencing analysis. All the 10 strains had a 99% match with S. aureus strains that were responsible for causing some serious biofilm mediated clinical manifestations like cystic fibrosis and device mediated infections. The biofilms were quantified using crystal violet staining and their ability to produce biofilms was analyzed using scanning electron microscopy and matched with the Genbank.

Conclusion

Hence these phylogenetic analysis aid in treating the patients and combating resistance to antibiotics.

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

Background and Aim

There are numerous reports of subclinical mastitis cases in Blitar, which is consistent with the region's high milk production and dairy cattle population. Staphylococcus aureus, which is often the cause of mastitis cases, is widely known because of its multidrug-resistant properties and resistance to β-lactam antibiotic class, especially the methicillin-resistant S. aureus (MRSA) strains. This study aimed to molecular detection and sequence analysis of the mecA gene in milk and farmer's hand swabs to show that dairy cattle are reservoirs of MRSA strains.

Materials and Methods

A total of 113 milk samples and 39 farmers' hand swab samples were collected from a dairy farm for the isolation of S. aureus using Mannitol salt agar. The recovered isolates were further characterized using standard microbiological techniques. Isolates confirmed as S. aureus were tested for sensitivity to antibiotics. Oxacillin Resistance Screening Agar Base testing was used to confirm the presence of MRSA, whereas the mecA gene was detected by polymerase chain reaction and sequencing.

Results

A total of 101 samples were confirmed to be S. aureus. There were 2 S. aureus isolates that were multidrug-resistant and 14 S. aureus isolates that were MRSA. The mecA gene was detected in 4/14 (28.6%) phenotypically identified MRSA isolates. Kinship analysis showed identical results between mecA from milk and farmers' hand swabs. No visible nucleotide variation was observed in the two mecA sequences of isolates from Blitar, East Java.

Conclusion

The spread of MRSA is a serious problem because the risk of zoonotic transmission can occur not only to people who are close to livestock in the workplace, such as dairy farm workers but also to the wider community through the food chain.

Antiseptics and mupirocin resistance in clinical, environmental, and colonizing coagulase negative Staphylococcus isolates

BACKGROUND

Coagulase-Negative Staphylococci (CoNS) are opportunistic and nosocomial pathogens. The excessive use of antimicrobial agents, including antiseptics, represents one of the world's major public health problems. This study aimed to test the susceptibility of CoNS to antiseptics.

METHODS

Out of 250 specimens collected from different sections of the hospital, 55 samples were identified as CoNS, categorized into three groups based on their sources: environmental samples (n = 32), healthcare worker carriers samples (n = 14), and clinical infection samples (n = 9). Isolates were examined for susceptibility to antibiotics and antiseptics, such as benzalkonium chloride (BC), cetyltrimethylammonium bromide (CTAB), and chlorhexidine digluconate (CHDG). Mupirocin and antiseptic resistance genes, as well as the mecA gene, were detected using polymerase chain reaction. CoNS isolates with notable resistance to antiseptics and antibiotics were identified using the API-Staph system.

RESULTS

A high frequency of multidrug resistance among CoNS clinical infection isolates was observed. Approximately half of the CoNS isolates from healthcare workers were susceptible to CHDG, but 93% were resistant to BC and CTAB. The frequency of antiseptics and antibiotics resistance genes in CoNS isolates was as follows: qacA/B (51/55; 92.7%), smr (22/55; 40.0%), qacG (1/55; 1.8%), qacH (6/55; 10.9%), qacJ (4/55; 7.3%), mecA (35/55; 63.6%), mupB (10/55; 18.2%), and mupA (7/55; 12.7%). A significant difference in the prevalence of smr gene and qacJ genes between CoNS isolates from healthcare workers and other isolates was reported (P value = 0.032 and ˂0.001, respectively). Four different CoNS species; S. epidermidis, S. chromogene, S. haemolyticus, and S. hominis, were identified by API.

CONCLUSIONS

CoNS isolates colonizing healthcare workers showed a high prevalence of antiseptic resistance genes, while clinical infection samples were more resistant to antibiotics. CHDG demonstrated greater efficacy than BC and CTAB in our hospital.

Staphylococcus aureus Induced Wound Infections Which Antimicrobial Resistance, Methicillin- and Vancomycin-Resistant: Assessment of Emergence and Cross Sectional Study

Background

Wound infection is a prevalent concern in the medical field, being is a multi-step process involving several biological processes. Methicillin-resistant S. aureus (MRSA) and vancomycin-resistant S. aureus (VRSA) infections often occur in areas of damaged skin, such as abrasions and open wounds.

Methods

This research aims to light the incidence of MRSA and VRSA in wound swabs, the antimicrobial susceptibility configuration of isolated S. aureus patterns in pus/wound samples collected from Saudi Arabian tertiary hospital. The cross section study, β- lactamase detection, VRSA genotyping, MAR index, D-test and VRSA genotyping are methods, which used for completed this research.

Results

Patients of several ages and genders delivered specimens from two hospitals in the Al jouf area, in the northern province of Saudi Arabia. S. aureus was found in 188 (34.7%) of the 542 wounds. The traumatized wounds provided 71 isolates (38.8%), surgical wound provided 49 isolates (26.8%) and abscess were represented 16 by isolates (8.7%). In the study, 123 (65.4%) out of 188 were MRSA, 60 (31.9%) were MSSA, and five (2.7%) were VRSA. Linezolid and rifampin were found to be the most effective antimicrobials with 100% in vitro antibacterial activity against S. aureus isolates. The Multiple antimicrobials resistance (MAR) index revealed 73 isolates (38.9%) with a MAR index greater than 0.2, and 115 (61.1%) less than 0.2. The D-test showed that of MLSb phenotypes among S. aureus, 22 (11.7%) strains were D-test positive (MLSbi phenotype), 53 (28.2%) strains were constitutive MLSc phenotypes, and 17 (9%) strains were shown to have MSb phenotypes. All VRSA isolates (n=5) were found to be positive for vanA, and no vanB positive isolates were detected in the study.

Conclusion

Regular monitoring and an antimicrobials stewardship program should be in place to provide critical information that can be utilized for empirical therapy and future prevention strategies.

Epidemiology of clinically isolated methicillin-resistant Staphylococcus aureus (MRSA) and its susceptibility to linezolid and vancomycin in Egypt: a systematic review with meta-analysis

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen that causes severe morbidity and mortality worldwide. For the establishment of national strategies to combat MRSA infection in each country, accurate and current statistics characterizing the epidemiology of MRSA are essential. The purpose of this study was to determine the prevalence of MRSA among Staphylococcus aureus clinical isolates in Egypt. In addition, we aimed to compare different diagnostic methods for MRSA and determine the pooled resistance rate of linezolid and vancomycin to MRSA. To address this knowledge gap, we conducted a systematic review with meta-analysis.

METHODS

A comprehensive literature search from inception to October 2022 of the following databases was performed: MEDLINE [PubMed], Scopus, Google Scholar, and Web of Science. The review was conducted following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) Statement. Based on the random effects model, results were reported as proportions with a 95% confidence interval (CI). Analyses of the subgroups were conducted. A sensitivity analysis was conducted to test the robustness of the results.

RESULTS

A total of sixty-four (64) studies were included in the present meta-analysis, with a total sample size of 7171 subjects. The overall prevalence of MRSA was 63% [95% CI: 55-70]. Fifteen (15) studies used both PCR and cefoxitin disc diffusion for MRSA detection, with a pooled prevalence rate of 67% [95% CI: 54-79] and 67% [95% CI: 55-80], respectively. While nine (9) studies used both PCR and Oxacillin disc diffusion for MRSA detection, the pooled prevalences were 60% [95% CI: 45-75] and 64% [95% CI: 43-84], respectively. Furthermore, MRSA appeared to be less resistant to linezolid than vancomycin, with a pooled resistance rate of 5% [95% CI: 2-8] to linezolid and 9% [95% CI: 6-12] to vancomycin, respectively.

CONCLUSION

Our review highlights Egypt's high MRSA prevalence. The cefoxitin disc diffusion test results were found to be consistent with PCR identification of the mecA gene. A prohibition on antibiotic self-medication and efforts to educate healthcare workers and patients about the proper use of antimicrobials may be required to prevent further increases.

Characterisation and prevalence of community-associated MRSA among horses, dogs, cats and their human handlers: a cross-sectional study

Methicillin-resistant Staphylococcus aureus (MRSA) as an infectious organism of public health significance has evolved to a genetically distinct community-acquired MRSA with extended resistance to other than β-lactams. A cross-sectional study was conducted among 149 participants handling 446 animals (240 horses and 206 companion animals). The isolates were characterised as S. aureus and MRSA based on polymerase chain reaction detection of the nuc, mecA and mecC genes and the pvl gene for differentiation as community associated/livestock associated or hospital associated. The isolation rate of S. aureus from the human handlers' samples was 26 (17.4%) and 170 (38.1%) from the animal samples. The prevalence of MRSA among the isolates was 7 (4.7%) from the human handlers and 19 (4.3%) from the animals. Dogs and dog handlers had the highest isolation rates and were more likely to be colonized by S. aureus and MRSA compared with horses, cats and their handlers. The highest prevalence of MRSA was from horses (5.0%) and dog handlers (10.6%). This study has demonstrated a high prevalence of community associated MRSA in apparently healthy animals and their human handlers. This has important implications for antibiotic selection and use as well as infection control measures.

Sensitivity and Specificity of a Novel Colony Characteristic for Determination of Methicillin-Resistant Staphylococcus aureus

Purpose: To assess colony morphology of Staphylococcus aureus isolates for target shape (T1) and its utility in the identification of methicillin-resistant S. aureus (MRSA).

Methods: Staphylococcus species isolated from blood cultures were studied for colony morphology characteristics. A polymerase chain reaction (PCR) test was performed on positive blood culture bottles for the detection of S. aureus and methicillin resistance. Colony morphology was read at 24 and 48 hours and defined as follows: target shaped (T1) - an elevated colony center encircled by a pale zone, which is surrounded by a single ring of peripheral enhancement giving a ‘target’ appearance; dome-shaped (T2) with an elevated center lacking the ‘target’ appearance.

Results: At 48 hours, 73.7% of MRSA and 59.5% of coagulase-negative staphylococci (CoNS) showed T1 morphology. T1 morphology has a sensitivity of 73.68% and specificity of 93.55% amongst S. aureus for identification of methicillin resistance and a high positive predictive value (95.45%) at 48 hours.

Conclusion: T1 morphology has a modest sensitivity with specificity and positive predictive value amongst S. aureus for identification of methicillin resistance at 48 hours. It can be potentially used for the identification of MRSA, especially in resource-limited settings and wherein a molecular test is not repeated if PCR testing has already identified methicillin-sensitive S. aureus (MSSA) on a recent specimen on the same patient.

Bacteriological Profile and Outcome of Culture-Positive Neonatal Sepsis in a Special Newborn Care Unit Setting, Odisha

Introduction: Nearly one-third of neonatal mortality in India is due to neonatal sepsis and death occurs in 30% of culture-positive neonates. Pathogens such as Klebsiella pneumoniae and Escherichia coli are the most common bacteria responsible for neonatal sepsis in India and South Asia.

Materials and Methods: It was an observational study, conducted in special newborn care units (SNCUs) of Capital Hospital in Bhubaneswar, Odisha from May 2017 to October 2019. All neonates (<28 days of life) with blood culture-positive sepsis were included in this study. Blood cultures were sent in all the babies with features of clinical sepsis. The demographic profile of neonates, clinical presentations, isolated organisms, and their sensitive patterns was recorded for analysis.

Results: Blood culture was sent in 445 suspected neonates with clinical sepsis out of which 115 blood culture positive organisms were isolated. Among the isolated organisms, 42 (35.6%) cases were Staphylococcus aureus followed by Coagulase negative Staphylococcus (CONS) (20.8%), E. coli (19.1%), K. pneumoniae (10.4%), Acinetobacter baumannii (2.7%), Enterobacter spp.(4.3%), Enterococcus spp. (4.3%), and Pseudomonas aeruginosa (2.7%). S. aureus was the predominant organism found in both early and late-onset sepsis. All Gram-negative bacilli (GNB) are resistant to ampicillin whereas cephalosporin resistance was found in 68% of cases. Mortality due to sepsis was 8%.

Conclusion: S. aureus followed by CONS was found to be the most common cause of sepsis in SNCU. A high degree of resistance of organisms to penicillins and cephalosporins calls for a re-evaluation of antibiotic policy and protocols for empirical treatment in neonatal sepsis.

Eleutheroside K Isolated from Acanthopanax henryi (Oliv.) Harms Inhibits the Expression of Virulence-Related Exoproteins in Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus (S.) aureus (MRSA) is a representative pathogen that produces numerous virulence factors involving manifold cytotoxins and exotoxins. The present study was designed to investigate the influence of Eleutheroside K (ETSK), a single compound isolated from the leaves of Acanthopanax (A.) henryi (Oliv.) Harms, on the exotoxins secreted by MRSA. The transcription and translation of the exotoxins (α-hemolysin and staphylococcal enterotoxins) related to virulence in S. aureus were determined via quantitative RT-PCR and western blot analysis. The effect of ETSK on the production of tumor necrosis factor (TNF)-α was evaluated using enzyme-linked immunosorbent assay. As a result, ETSK at sub-MIC concentrations could reduce the protein expression of α-hemolysin and enterotoxin, and the expression of genes that regulate virulence factors was also inhibited. In addition, the TNF-inducing activity of S. aureus was attenuated by ETSK in a dose-dependent manner. These results revealed that ETSK not only reduced the protein and gene expression levels of related exotoxins but also suppressed the ability of S. aureus to induce macrophages to release cytokines. This study indicated that the inhibition of MRSA infection by ETSK may be achieved by reducing the virulence of S. aureus and highlighted the potential of ETSK as an innovative strategy for the prevention and treatment of MRSA infections.

In vitro antimicrobial activity of cold atmospheric microwave plasma against bacteria causing canine skin and ear infections

BACKGROUND

Cold atmospheric plasma (CAP) is a new generation medical therapeutic option for bacterial infections. CAP causes physical cell wall rupture and DNA damage, therefore making it highly useful in the treatment of various conditions such as skin infections.

HYPOTHESIS/OBJECTIVES

The antimicrobial activity of cold atmospheric microwave plasma (CAMP) against major strains in canine skin infections was tested and the difference in antimicrobial activity between the antibiotic-resistant and antibiotic-susceptible strains of Staphylococcus pseudintermedius was evaluated.

METHODS AND MATERIALS

American Type Culture Collection (ATCC) strains (Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli) and clinical isolates identified as methicillin-resistant S. pseudintermedius (n = 27) and methicillin-susceptible S. pseudintermedius (n = 13) were exposed to CAMP for 10 s, 30 s and 60 s. Afterwards, the bacterial survival rate was confirmed.

RESULTS

Gram-negative bacteria (P. aeruginosa and E. coli) were more susceptible than Gram-positive bacteria (S. aureus and S. pseudintermedius) for the same duration of CAMP exposure. Only the Gram-negative bacteria were completely killed after 60 s exposure. In S. pseudintermedius isolates, CAMP exposure had similar antibacterial effects regardless of antibiotic resistance.

CONCLUSIONS AND CLINICAL IMPORTANCE

CAMP has sufficient antimicrobial activity against major bacterial strains that cause pyoderma and otitis externa in dogs, and may be an alternative therapeutic option for S. pseudintermedius skin infections, for which antibiotics often are ineffective because of antimicrobial resistance in clinical veterinary medicine.

Prevalence and Impact of Biofilms on Bloodstream and Urinary Tract Infections: A Systematic Review and Meta-Analysis

This study sought to assess the prevalence and impact of biofilms on two commonly biofilm-related infections, bloodstream and urinary tract infections (BSI and UTI). Separated systematic reviews and meta-analyses of observational studies were carried out in PubMed and Web of Sciences databases from January 2005 to May 2020, following PRISMA protocols. Studies were selected according to specific and defined inclusion/exclusion criteria. The obtained outcomes were grouped into biofilm production (BFP) prevalence, BFP in resistant vs. susceptible strains, persistent vs. non-persistent BSI, survivor vs. non-survivor patients with BSI, and catheter-associated UTI (CAUTI) vs. non-CAUTI. Single-arm and two-arm analyses were conducted for data analysis. In vitro BFP in BSI was highly related to resistant strains (odds ratio-OR: 2.68; 95% confidence intervals-CI: 1.60–4.47; p < 0.01), especially for methicillin-resistant Staphylococci. BFP was also highly linked to BSI persistence (OR: 2.65; 95% CI: 1.28–5.48; p < 0.01) and even to mortality (OR: 2.05; 95% CI: 1.53–2.74; p < 0.01). Candida spp. was the microorganism group where the highest associations were observed. Biofilms seem to impact Candida BSI independently from clinical differences, including treatment interventions. Regarding UTI, multi-drug resistant and extended-spectrum β-lactamase-producing strains of Escherichia coli, were linked to a great BFP prevalence (OR: 2.92; 95% CI: 1.30–6.54; p < 0.01 and OR: 2.80; 95% CI: 1.33–5.86; p < 0.01). More in vitro BFP was shown in CAUTI compared to non-CAUTI, but with less statistical confidence (OR: 2.61; 95% CI: 0.67–10.17; p < 0.17). This study highlights that biofilms must be recognized as a BSI and UTI resistance factor as well as a BSI virulence factor.

Comparison of PCR and phenotypic methods for the detection of methicillin resistant Staphylococcus aureus

Background and Objectives:

Resistance to methicillin in methicillin resistant strains of Staphylococcus aureus (MRSA) is due to the presence of mec-A gene, which encodes a low affinity penicillin binding protein (PBP)-2a or PBP2. Accurate and rapid identification of MRSA in clinical specimens is essential for timely decision on effective treatment. The aim of the study was to compare three different methods for detection of MRSA namely cefoxitin disc diffusion, CHROM agar MRSA and VITEK-2 susceptibility with PCR which is the gold standard reference method and to find the antibiotic susceptibility pattern of these isolates by VITEK-2.

Materials and Methods:

A Total of 100 non-duplicate S. aureus isolates were collected from different clinical samples among both outpatient and inpatients. Detection of MRSA among these isolates was done by cefoxitin disc diffusion, VITEK-2, CHROM agar MRSA and PCR.

Results:

The sensitivity and specificity of cefoxitin disc diffusion and Vitek was found to be 97.2% and 100%, while that of CHROM agar was found to be 100% and 78.6%. The overall prevalence of MRSA in our study by PCR was 72%.

Conclusion:

Based on the findings in our study, isolates which show cefoxitin zone diameter < 22 mm can be reported as MRSA. However, those isolates which have a zone diameter between 22–24 mm, should ideally be confirmed by PCR.

Development and application of a triplex-PCR assay for rapid detection of methicillin-resistant Staphylococcus aureus from pigs

A triplex-PCR assay was developed and evaluated for rapid detection of methicillin-resistant Staphylococcus aureus (MRSA) recovered from various biological samples of pig. Three sets of primers were designed to target mecA, 16S rRNA and nuc genes of MRSA. The specific amplification generated three bands on agarose gel, with sizes 280 bp for mecA, 654 bp for 16S rRNA and 481 bp for nuc, respectively. A potential advantage of the PCR assay is its sensitivity with a detection limit of 10²  CFU per ml of bacteria. In all, 79 MRSA isolates recovered from various samples of pigs were subjected to the amplification by the triplex-PCR assay and all the isolates yielded three bands corresponding to the three genes under this study. No false-positive amplification was observed, indicating the high specificity of the developed triplex-PCR assay. This assay will be a useful and powerful method for differentiation of MRSA from methicillin-sensitive S. aureus, coagulase-negative methicillin-resistant staphylococci and coagulase-negative methicillin-sensitive staphylococci.

Eleutheroside K isolated from Acanthopanax henryi (Oliv.) Harms suppresses methicillin resistance of Staphylococcus aureus

Acanthopanax (A.) henryi (Oliv.) Harms contain many bioactive compounds commonly used in traditional Chinese medicine. The objective of the present study was to investigate the antibacterial activity of the single constituent, Eleutheroside K (ETSK) isolated from the leaves of A. henryi (Oliv.) Harms, against methicillin-resistant Staphylococcus (S.) aureus (MRSA). Broth microdilution assay was used to measure the minimal inhibitory concentration (MIC) and the MIC values of ETSK against eight clinical S. aureus strains were all 50 µg ml^-1 . At sub-inhibitory concentrations, a synergistic effect between oxacillin (OXA) and ETSK was confirmed using checkerboard dilution assay and time-kill curve analysis. The bacteriostatic effect became more pronounced when ETSK was used in combination with detergent (Triton X-100) or ATPase inhibitor (N, N'-dicyclohexylcarbodiimide). According to western blot analysis, the down-regulated expression of Penicillin-binding protein 2a (PBP2a) further validated that the bacterial activity was inhibited when treated with ETSK in a dose-dependent manner. Results based on our study verified that ETSK significantly suppressed MRSA infections and emphasized the potential application of ETSK as a novel anti-MRSA natural drug.

Identification of fusidic acid resistance in clinical isolates of Staphylococcus pseudintermedius from dogs in Korea

BACKGROUND

Staphylococcus pseudintermedius is a major bacterial species associated with canine pyoderma and otitis. Fusidic acid is used to treat skin infections caused by Gram-positive bacteria. The incidence of resistance to fusidic acid in S. pseudintermedius has importance in terms of limiting treatment options for bacterial infections.

HYPOTHESIS/OBJECTIVES

To evaluate the occurrence and mechanisms of fusidic acid resistance in clinical isolates of S. pseudintermedius.

ANIMALS

Fifty-two S. pseudintermedius isolates were collected from dogs with pyoderma (n = 36) or otitis (n = 16).

METHODS AND MATERIALS

The disk diffusion method determined that isolates <24 mm were resistant to fusidic acid. Minimum inhibitory concentrations (MICs) were measured by the E-test in those with confirmed resistance to fusidic acid by the disk diffusion method. Phenotypically fusidic acid resistant isolates were subjected to PCR to detect the presence of resistance-related genes (fusA, fusB, fusC and fusD) and fusA was further sequenced to identify point mutations.

RESULTS

Fourteen of 52 (27%) S. pseudintermedius isolates were resistant to fusidic acid and all of these showed low-level resistance. Among fusidic acid resistant isolates, fusA point mutations were confirmed in 11 isolates and amino acid substitutions were found in five. fusC was detected in seven isolates, but neither fusB nor fusD was detected.

CONCLUSIONS AND CLINICAL IMPORTANCE

This study demonstrates the occurrence and resistance mechanisms to fusidic acid in clinical isolates of S. pseudintermedius. Continuous monitoring for fusidic acid resistance is recommended.

How to select a probiotic? A review and update of methods and criteria

International competition within the dairy market and increasing public awareness about the importance of functional food consumption are providing new challenges for innovation in the probiotic sector. In this context, countless references are currently dedicated to the selection and characterization of new species and more specific strains of probiotic bacteria. In general, these studies adopt basic selection criteria established by the World Health Organization (WHO), including host-associated stress resistance, epithelium adhesion ability, and antimicrobial activity. These aspects are applied to ensure that the candidate probiotic could withstand the stressful conditions of the human digestive system and exert functional proprieties. However, it cannot be assumed that these novel microbial strains are capable of offering several biological benefits attributed to probiotics. Additionally, safety-associated selection criteria, such as plasmid-associated antibiotic resistance spreading and enterotoxin production, are often neglected. This article reviews the recent developments in the processes, strategies, and methods, such as anticarcinogenic, antidepression, antianxiety, antiobesity, antidiabetic, immunostimulatory, and cholesterol-lowering assessments, to select probiotic strains with the ultimate objective of assisting future probiotic microbe evaluation studies.

Frequency of Aminoglycoside-Resistance Genes in Methicillin-Resistant Staphylococcus aureus (MRSA) Isolates from Hospitalized Patients

Background

Staphylococcus aureus is one of the most important causative agents in community- and hospital-acquired infections. Aminoglycosides are powerful bactericidal drugs that are often used in combination with beta-lactams or glycopeptides to treat staphylococcal infections.

Objectives

The main objective of the present study was to determine the prevalence of aminoglycoside resistance among methicillin-resistant Staphylococcus aureus (MRSA) isolates in hospitalized patients in Sari and Tehran, Iran.

Methods

In this study, 174 MRSA strains isolated from different clinical samples, such as blood, sputum, tracheal exudates, bronchus, pleura, urine, wounds, and catheters, were collected from hospitalized patients in Tehran and Sari during 2014. Antibiotic susceptibility testing was performed against nine antibiotics with the Kirby-Bauer disk diffusion method according to CLSI guidelines. The MRSA strains were examined with oxacillin and cefoxitin disks. MRSA was then validated by detection of the mecA gene. PCR was used to evaluate the prevalence of the aminoglycoside-resistance genes aac (6’)-Ie/aph (2”), aph (3’)-IIIa, and ant (4’) among the MRSA isolates.

Results

The results of drug susceptibility testing showed that the highest rate of resistance was against erythromycin in Tehran (84.4%) and gentamicin (71.7%) in Sari. All isolates were sensitive to vancomycin, and all strains harbored the mecA gene. The aac (6’)-Ie/aph (2”), aph (3’)-IIIa, and ant (4’)-Ia genes were detected among 134 (77%), 119 (68.4%), and 122 (70.1%) of the isolates, respectively.

Conclusions

The present study showed a high prevalence of aminoglycoside-resistance genes among MRSA isolates in two cities in Iran.

Molecular Detection of Methicillin-Resistant Staphylococcus aureus by Non-Protein Coding RNA-Mediated Monoplex Polymerase Chain Reaction

Non-protein coding RNA (npcRNA) is a functional RNA molecule that is not translated into a protein. Bacterial npcRNAs are structurally diversified molecules, typically 50-200 nucleotides in length. They play a crucial physiological role in cellular networking, including stress responses, replication and bacterial virulence. In this study, by using an identified npcRNA gene (Sau-02) in Methicillin-resistant Staphylococcus aureus (MRSA), we identified the Gram-positive bacteria S. aureus. A Sau-02-mediated monoplex Polymerase Chain Reaction (PCR) assay was designed that displayed high sensitivity and specificity. Fourteen different bacteria and 18 S. aureus strains were tested, and the results showed that the Sau-02 gene is specific to S. aureus. The detection limit was tested against genomic DNA from MRSA and was found to be ~10 genome copies. Further, the detection was extended to whole-cell MRSA detection, and we reached the detection limit with two bacteria. The monoplex PCR assay demonstrated in this study is a novel detection method that can replicate other npcRNA-mediated detection assays.

Evaluation of Genotypic and Phenotypic Methods for Detection of Methicillin Resistant Staphylococcus aureus in a Tertiary Care Hospital of Eastern Odisha

INTRODUCTION

Methicillin resistant Staphylococcus aureus has emerged as an important pathogen in nosocomial and community acquired infections. Accurate and rapid identification of MRSA in clinical specimens is essential for timely decision of effective antimicrobial chemotherapy.

AIM

The present study was conducted to compare efficacy of four conventional phenotypic methods, with mec- A based polymerase chain reaction (PCR) for MRSA identification.

MATERIALS AND METHODS

Methicillin resistance was determined in 200 S.aureus isolates by oxacillin disc diffusion, cefoxitin disc diffusion, Oxacillin Resistance Screening Agar and E-test. The results were compared with mec-A based PCR.

RESULTS

Among 200 S.aureus isolates 62 (31%) were positive for mec-A gene by PCR. Cefoxitin disc diffusion, Oxacillin Resistance Screening Agar and E-test showed 100% specificity. Oxacillin disc diffusion had lowest sensitivity (82.5%) and specificity (98.5%) among all. The conventional methods take more time than PCR for diagnosing MRSA. Linezolid, Vancomycin & Dalfopristin were the highly sensitive drugs against MRSA isolates.

CONCLUSION

Cefoxitin disc diffusion, is rapid, simple and cheaper, hence can be used routinely as an alternative to PCR for detection of MRSA in resource constraint laboratories.

In vitro antibiogram pattern of Staphylococcus aureus isolated from wound infection and molecular analysis of mecA gene and restriction sites in methicillin resistant Staphylococcus aureus

Staphylococcus aureus is a common nosocomial pathogen with property to develop resistance to antimicrobial agents. But in the modern era, drug resistance had been developed by microbes due to its continuous usage of antibiotics. This study was carried out to evaluate antibiotic resistant pattern of methicillin resistant Staphylococcus aureus (MRSA) using molecular genotyping. In view of the present problem, the study has been conducted to detect the molecular genotyping of mecA gene from MRSA and confirmation of its restriction sites using EcoRI and BamHI. The pus samples were swabbed out, and clinical strains were isolated using standard microbiological procedures. Then the strains were subjected to in vitro antibiotic susceptibility assay and identified MRSA. Further molecular genotyping of mecA gene was determined by polymerase chain reaction technique. The percentage analysis was done. The clinical strains were isolated from the wound infected patients. A total of 60 samples were collected, of 60 samples, 40 (66.7%) were showed positive to strains of S. aureus. The in vitro antibiotic susceptibility assay was carried to find the drug sensitive and resistant patterns. Further methicillin resistant strains (35%) of S. aureus were screened and subjected to molecular genotyping of mecA gene and was confirmed by restriction digestion. Overall, 70% of plasmids show positive for the presence of mecA gene, although all strains have restriction sites. Hence, the present study revealed that the early detection of antibiotic resistant character using molecular genotyping will help the infected patient to cure short period and will reduce the development of multidrug resistance.

Comparison of four diagnostic methods for detection of methicillin resistant Staphylococcus aureus

BACKGROUND AND OBJECTIVES

Methicillin-resistant Staphylococcus aureus (MRSA) is a well-known pathogen with a worldwide distribution. Given the increasing rate of MRSA infections, implementing of reliable, accurate and rapid testing for diagnosis of MRSA is necessary. The aim of this study was to compare four diagnostic methods for detection of MRSA isolates.

MATERIALS AND METHODS

From December 2012 to April 2014, 120 S. aureus isolates were collected from three hospitals affiliated with Tehran University of Medical Sciences. MRSA isolates were detected by four different methods including cefoxitin disc diffusion test, oxacillin disc diffusion test, minimum inhibitory concentration (MIC) of oxacillin as determined by MIC test strip, and mecA detection by PCR.

RESULTS

Out of 120 S. aureus isolates, cefoxitin disc diffusion test, oxacillin disc diffusion test and MIC test strip identified 60 (50%), 48 (40%), 55 (45.83%) isolates as MRSA, respectively. The sensitivity and specificity for oxacillin disc diffusion, cefoxitin disc diffusion and MIC of oxacillin were 80% and 100%, 100% and 100%, and 91.6% and 100%, respectively.

CONCLUSION

Cefoxitin disc diffusion test is reliable substitute for detection of MRSA in clinical laboratory where MIC detection and molecular methods are not accessible.

PCR-based identification of methicillin-resistant Staphylococcus aureus strains and their antibiotic resistance profiles

OBJECTIVE

To evaluated the PCR for mecA gene compared with the conventional oxacillin disk diffusion method for methicillin-resistant Staphylococcus aureus (S. aureus) identification.

METHODS

A total of 292 S. aureus strains were isolated from various clinical specimens obtained from hospitalized patients. Susceptibility test to several antimicrobial agents was performed by disk diffusion agar according to Clinical and Laboratory Standards Institute guidelines. The PCR amplification of the mecA gene was carried out in all the clinical isolates.

RESULTS

Among antibiotics used in our study, penicillin showed the least anti-staphylococcal activity and vancomycin was the most effective. The rate of methicillin-resistant S. aureus prevalence determined by oxacillin disk diffusion method was 47.6%; whereas, 45.1% of S. aureus isolates were mecA- positive in the PCR assay.

CONCLUSIONS

This study is suggestive that the PCR for detection of mecA gene is a fast, accurate and valuable diagnostic tool, particularly in hospitals in areas where methicillin-resistant S. aureus is endemic.