Biochemical and Molecular Analysis of Staphylococcus aureus Clinical Isolates from Hospitalized Patients

Proven anti-virulence therapies in combating methicillin- and vancomycin-resistant Staphylococcus aureus infections

Introduction

Despite years of efforts to develop new antibiotics for eradicating multidrug-resistant (MDR) and multi-virulent Methicillin-Resistant Staphylococcus aureus (MRSA) and Vancomycin-Resistant Staphylococcus aureus (VRSA) infections, treatment failures and poor prognoses in most cases have been common. Therefore, there is an urgent need for new therapeutic approaches targeting virulence arrays. Our aim is to discover new anti-virulence therapies targeting MRSA and VRSA virulence arrays.

Methodology

We employed phenotypic, molecular docking, and genetic studies to screen for anti-virulence activities among selected promising compounds: Coumarin, Simvastatin, and Ibuprofen.

Results

We found that nearly all detected MRSA and VRSA strains exhibited MDR and multi-virulent profiles. The molecular docking results aligned with the phenotypic and genetic assessments of virulence production. Biofilm and hemolysin productions were inhibited, and all virulence genes were downregulated upon treatment with sub-minimum inhibitory concentration (sub-MIC) of these promising compounds. Ibuprofen was the most active compound, exhibiting the highest inhibition and downregulation of virulence gene products. Moreover, in vivo and histopathological studies confirmed these results. Interestingly, we observed a significant decrease in wound area and improvements in re-epithelialization and tissue organization in the Ibuprofen and antimicrobial treated group compared with the group treated with antimicrobial alone. These findings support the idea that a combination of Ibuprofen and antimicrobial drugs may offer a promising new therapy for MRSA and VRSA infections.

Conclusion

We hope that our findings can be implemented in clinical practice to assist physicians in making the most suitable treatment decisions.

Antibacterial and antibiofilm potentials of vancomycin-loaded niosomal drug delivery system against methicillin-resistant Staphylococcus aureus (MRSA) infections

The threat of methicillin-resistant Staphylococcus aureus (MRSA) is increasing worldwide, making it significantly necessary to discover a novel way of dealing with related infections. The quick spread of MRSA isolates among infected individuals has heightened public health concerns and significantly limited treatment options. Vancomycin (VAN) can be applied to treat severe MRSA infections, and the indiscriminate administration of this antimicrobial agent has caused several concerns in medical settings. Owing to several advantageous characteristics, a niosomal drug delivery system may increase the potential of loaded antimicrobial agents. This work aims to examine the antibacterial and anti-biofilm properties of VAN-niosome against MRSA clinical isolates with emphasis on cytotoxicity and stability studies. Furthermore, we aim to suggest an effective approach against MRSA infections by investigating the inhibitory effect of formulated niosome on the expression of the biofilm-associated gene (icaR). The thin-film hydration approach was used to prepare the niosome (Tween 60, Span 60, and cholesterol), and field emission scanning electron microscopy (FE-SEM), an in vitro drug release, dynamic light scattering (DLS), and entrapment efficiency (EE%) were used to investigate the physicochemical properties. The physical stability of VAN-niosome, including hydrodynamic size, polydispersity index (PDI), and EE%, was analyzed for a 30-day storage time at 4 °C and 25 °C. In addition, the human foreskin fibroblast (HFF) cell line was used to evaluate the cytotoxic effect of synthesized niosome. Moreover, minimum inhibitory and bactericidal concentrations (MICs/MBCs) were applied to assess the antibacterial properties of niosomal VAN formulation. Also, the antibiofilm potential of VAN-niosome was investigated by microtiter plate (MTP) and real-time PCR methods. The FE-SEM result revealed that synthesized VAN-niosome had a spherical morphology. The hydrodynamic size and PDI of VAN-niosome reported by the DLS method were 201.2 nm and 0.301, respectively. Also, the surface zeta charge of the prepared niosome was - 35.4 mV, and the EE% ranged between 58.9 and 62.5%. Moreover, in vitro release study revealed a sustained-release profile for synthesized niosomal formulation. Our study showed that VAN-niosome had acceptable stability during a 30-day storage time. Additionally, the VAN-niosome had stronger antibacterial and anti-biofilm properties against MRSA clinical isolates compared with free VAN. In conclusion, the result of our study demonstrated that niosomal VAN could be promising as a successful drug delivery system due to sustained drug release, negligible toxicity, and high encapsulation capacity. Also, the antibacterial and anti-biofilm studies showed the high capacity of VAN-niosome against MRSA clinical isolates. Furthermore, the results of real-time PCR exhibited that VAN-niosome could be proposed as a powerful strategy against MRSA biofilm via down-regulation of icaR gene expression.

Whole-Genome Sequencing-Based Screening of MRSA in Patients and Healthcare Workers in Public Hospitals in Benin

Methicillin-resistant Staphylococcus aureus (MRSA) constitutes a serious public health concern, with a considerable impact on patients' health, and substantial healthcare costs. In this study, patients and healthcare workers (HCWs) from six public hospitals in Benin were screened for MRSA. Strains were identified as MRSA using conventional microbiological methods in Benin, and confirmed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry in Belgium. Whole-genome sequencing (WGS) was used on the confirmed MRSA isolates, to characterize their genomic content and study their relatedness. Amongst the 305 isolates (304 wound swabs and 61 nasal swabs) that were collected from patients and HCWs, we detected 32 and 15 cases of MRSA, respectively. From this collection, 27 high-quality WGS datasets were obtained, which carried numerous genes and mutations associated with antimicrobial resistance. The mecA gene was detected in all the sequenced isolates. These isolates were assigned to five sequence types (STs), with ST8 (55.56%, n = 15/27), ST152 (18.52%, n = 5/27), and ST121 (18.52%, n = 5/27) being the most common. These 27 isolates carried multiple virulence genes, including the genes encoding the Panton-Valentine leukocidin toxin (48.15%, n = 13/27), and the tst gene (29.63%, n = 8/27), associated with toxic shock syndrome. This study highlights the need to implement a multimodal strategy for reducing the risk of the cross-transmission of MRSA in hospitals.

Detection of Methicillin-Resistant Staphylococcus aureus among Foodborne Pathogenic Strains and Assessment of Their Adhesion Ability and Cytotoxic Effects in HCT-116 Cells

Staphylococcus aureus is one of the high-threat pathogens equipped with a repertoire of virulence factors making it responsible for many infections in humans, including foodborne diseases. The present study aims to characterize antibiotic resistance and virulence factors in foodborne S. aureus isolates, and to investigate their cytotoxic effects in human intestinal cells (HCT-116). Our results revealed methicillin resistance phenotypes (MRSA) along with the detection of mecA gene (20%) among tested foodborne S. aureus strains. Furthermore, 40% of tested isolates showed a strong ability for adhesion and biofilm formation. A high rate of exoenzymes production by tested bacteria was also registered. Additionally, treatment with S. aureus extracts leads to a significant decrease in HCT-116 cell viability, accompanied by a reduction in the mitochondrial membrane potential (MMP), as a result of reactive oxygen species (ROS) generation. Thereby, S. aureus food poisoning remains daunting and needs particular concern to prevent foodborne illness.

Bioassay for total serum bioactivity of Atractylodes lancea

The study aimed to establish a bioassay for total bioactivity of Atractylodes lancea (AL) in human serum samples. Inhibition of bacterial growth (Staphylococcus aureus ATCC 25923) was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The calibration curve (0, 0.39, 0.78, 1.56, 3.13, 2.56, and 50 ng/μl) was linear with correlation coefficients >0.990. The limit of quantification (LOQ) was 1.66 mg/ml using 20-ml serum sample. The developed bioassay method meets the standard of the bioanalytical method for determination of serum bioactivity of AL.

Assessment of Foodborne Bacterial Pathogens in Buffalo Raw Milk Using Polymerase Chain Reaction Based Assay

Milk is a putrescible commodity that is extremely prone to microbial contamination. Primarily, milk and dairy products are believed to be easily contaminated by pathogenic microorganisms, including Listeria monocytogenes, Salmonella spp., and Staphylococcus aureus. The microbiological quality of raw milk and dairy products regarding foodborne pathogens is of paramount importance due to concern of human health. In this study 400 buffalo raw milk samples were screened for assessing the prevalence of L. monocytogenes, Salmonella spp., and S. aureus. This study implemented uniplex-polymerase chain reaction (u-PCR) and multiplex-polymerase chain reaction (m-PCR) assays for the fast simultaneous detection of these pathogens comparing to the conventional culturing methods. Raw milk samples were found contaminated with the prevalence of 2.2%, 4.0%, and 14.2% for L. monocytogenes, Salmonella spp., and S. aureus, respectively. These pathogens were detected with the optimized polymerase chain reaction assays after 6 h of enrichment. u-PCR and m-PCR demonstrated the limit of detection as 10⁴, 10², and 10 cells/mL after 6, 12, 18, and 24 h for each culture of the pathogens. A high sensitivity (10 colony-forming unit [CFU]/mL) of the m-PCR protocol was noted. The developed protocol is a cost-effective and rapid method for the simultaneous detection of pathogens associated with raw milk and dairy industries.

Phenotypic and genotypic profiling reveals a high prevalence of methicillin-resistant Staphylococcus aureus isolated from hospitals, houseflies and adjacent informal food retailers in Botswana

The increasing occurrence of methicillin-resistant Staphylococcus aureus (MRSA) in the environment, food and healthcare systems is a global public health concern. MRSA is reported to cause food poisoning, osteomyelitis and pyogenic infections of the skin, and consequently has been categorized as a high-priority pathogen by the World Health Organization. Here, we determined the presence of MRSA in clinical (n=56), food (n=150) and housefly samples (n=970) collected from two hospitals in Botswana. Characterization based on phenotypic (antimicrobial resistance, biofilm production) and genotypic (antimicrobial resistance genes and integrons) profiles were performed on all isolates. Of the total samples tested, 64 were positive for MRSA following conventional culture methods and PCR amplification of the mecA and mecC genes for confirmation of presumptive MRSA isolates. The confirmed isolates included 71 % (95 % CI 83.2-59.6) from clinical, 9 % (95 % CI 14--4.8) from food, and 1 % (95 % CI 1.6-0.4) collected from housefly samples. In total 89 % (n=57) isolates in the current study showed a multidrug resistance phenotype, among these, resistance to β-lactams and glycoside antibiotic classes were predominant. Genotypic characterization showed the domination of the blatem gene (95 %) followed by fox (63 %) and tetO (19 %) whilst vanA was only reported in 13 % of the isolates. Integrons were detected in 50 % (32/64) of the total MRSA isolates, and we report a high prevalence of etd gene, detected in 67 % (43/64) of the isolates followed by eta 38 % (24/64) whilst tsst-1 (3%) was the least detected genetic determinant. The genes etb and PVL were not detected in a ll the tested MRSA isolates. We provide the first report on the prevalence of MRSA isolated from the clinical-food-vector nexus harbouring biofilm and blatem genes, and antibiotic resistance profiles in Botswana. These results are significant for risk-assessment analysis and the development of improved MRSA infection prevention and control strategies.

Prevalence of Methicillin and β−Lactamase Resistant Pathogens Associated with Oral and Periodontal Disease of Children in Mymensingh, Bangladesh

Oral and periodontal diseases (OPD) is considered one of the main problems of dentistry worldwide. This study aimed to estimate the prevalence of oral and periodontal pathogenic bacteria along with their antimicrobial resistance pattern in 131 children patients aged between 4–10 years who attended in Mymensingh Medical College Hospital during October 2019 to March 2020. OPD pathogens were identified through isolation, cultural and biochemical properties, and nucleic acid detection. The isolates were subjected to antimicrobial susceptibility to 12 antibiotics commonly used in dentistry. In addition, the isolates were analyzed molecularly for the presence of six virulence and three antibacterial resistance genes. Five pathogens were identified, of which Staphylococcus aureus (S. aureus) (49%) and S. salivarius (46%) were noticed frequently; other bacteria included S. mutans (16.8%), S. sobrinus (0.8%) and L. fermentum (13.7%). The virulence genes—clumping factor A (clfA) was detected in 62.5% isolates of S. aureus, and gelatinase enzyme E (gelE) gene was detected in 5% isolates of S. salivarius, while other virulence genes were not detected. All the tested isolates were multidrug-resistant. The overall prevalence of MDR S. aureus, Streptococcus spp. and L. fermentum was 92.2%, 95.1% and 100%, respectively. It was observed that a high proportion of isolates were found resistant to 5–8 antibiotics. A majority of S. aureus, Streptococcus spp., and L. fermentum isolates tested positive for the β−lactamase resistance genes blaTEM and cfxA, as well as the methicillin resistance gene mecA. Phylogenetically, the resistance genes showed variable genetic character among Bangladeshi bacterial pathogens. In conclusion, S. aureus and S. salivarius were major OPD pathogens in patients attended in Mymensingh Medical College Hospital of Bangladesh, and most were Beta-lactam and methicillin resistant.

Comparative Genomic Analysis of a Panton–Valentine Leukocidin-Positive ST22 Community-Acquired Methicillin-Resistant Staphylococcus aureus from Pakistan

Staphylococcus aureus (S. aureus) ST22 is considered a clinically important clone because an epidemic strain EMRSA-15 belongs to ST22, and several outbreaks of this clone have been documented worldwide. We performed genomic analysis of an S. aureus strain Lr2 ST22 from Pakistan and determined comparative analysis with other ST22 strains. The genomic data show that Lr2 belongs to spa-type t2986 and harbors staphylococcal cassette chromosome mec (SCCmec) type IVa(2B), one complete plasmid, and seven prophages or prophage-like elements. The strain harbors several prophage-associated virulence factors, including Panton–Valentine leukocidin (PVL) and toxic shock syndrome toxin (TSST). The single nucleotide polymorphism (SNPs)-based phylogenetic relationship inferred from whole genome and core genome revealed that strain Lr2 exhibits the nearest identities to a South African community-acquired methicillin-resistant S. aureus (CA-MRSA) ST22 strain and makes a separate clade with an Indian CA-MRSA ST22 strain. Although most ST22 strains carry blaZ, mecA, and mutations in gyrA, the Lr2 strain does not have the blaZ gene but, unlike other ST22 strains, carries the antibiotic resistance genes erm(C) and aac(6′)-Ie-aph(2″)-Ia. Among ST22 strains analyzed, only the strain Lr2 possesses both PVL and TSST genes. The functional annotation of genes unique to Lr2 revealed that mobilome is the third-largest Cluster of Orthologous Genes (COGs) category, which encodes genes associated with prophages and transposons. This possibly makes methicillin-resistant S. aureus (MRSA) Lr2 ST22 strain highly virulent, and this study would improve the knowledge of MRSA ST22 strains in Pakistan. However, further studies are needed on a large collection of MRSA to comprehend the genomic epidemiology and evolution of this clone in Pakistan.

Genetic relationship of Staphylococcus aureus isolated from humans, animals, environment, and Dangke products in dairy farms of South Sulawesi Province, Indonesia

Background and Aim:

Staphylococcus aureus is a bacterium that causes several infectious diseases, including mastitis, endocarditis, and osteomyelitis, and poses a threat to human and animal health. This study aims to phenotypically and genetically identify S. aureus from the isolates collected from humans, animals, environment, and Dangke products in the dairy farms of South Sulawesi Province, Indonesia, as well as to establish a genetic relationship among the isolated S. aureus strains.

Materials and Methods:

The total number of samples was 142, comprising 30 humans (skin swab), 58 animals (raw milk), 14 dairy products (Dangke), and 40 environmental samples (water). S. aureus was phenotypically identified using the culture method, followed by Gram staining, catalase test, and coagulase test. Simultaneously, genotypic identification of S. aureus was performed using the conventional polymerase chain reaction and sequencing methods. Sequencing data were analyzed using the MEGA X software by comparing BLAST National Center for Biotechnology Information databases.

Results:

The phenotypic methods revealed that 56/142 (39.4%) animal, human, and Dangke samples grew on culture, and 56/56 (100%) were Gram stain positive, 56/56 (100%) catalase-positive, and 23/56 (41.1%) coagulase positive. The genotypic method revealed that 32/56 (57.1%) samples amplified the nuc gene. The phylogenetic analysis of 12 isolates revealed that they are all closely related and do not belong to distinct clades.

Conclusion:

It indicates that S. aureus isolates from animals (S30) are probably the same strain as human isolates (H2, H3, H4, and H5). The findings of this study can be used as information regarding the importance of preventing and controlling diseases caused by S. aureus using a health approach involving the human, animal, and environmental sectors. This study was limited to the sequencing analysis of the nuc gene.

Antibiofilm and anticancer activities of unripe and ripe Azadirachta indica (neem) seed extracts

BACKGROUND

Antibiotic resistances of pathogens and breast cancer warrant the search for new alternative strategies. Phytoextracts can eradicate microbe-borne diseases as well as cancer with lower side effects compared to conventional antibiotics.

AIM

Unripe and ripe Azadirachta indica (neem) seed extracts were explored as potential antibiofilm and anticancer agents in combating multidrug-resistant infectious bacteria as well as anticancer agents against the MDR breast cancer cell lines.

METHODS

Shed-dried neem seeds (both unripe and ripe) were pulverized and extracted using methanol. The chemical components were identified with FTIR and gas chromatography - mass spectrometry. Antibiofilm activity of neem seed extracts were assessed in terms of minimum biofilm inhibitory concentration (MBIC), minimum biofilm eradication concentration (MBEC), and fluorescence microscopic studies on Staphylococcus aureus and Vibrio cholerae. Bacterial cells were studied by fluorescence microscopy using acridine orange/ethidium bromide as the staining agents. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were evaluated to observe the antibacterial activities. Cytotoxicity of the extracts against human blood lymphocytes and the anticancer activity against drug-resistant breast cancer cell lines were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and fluorescence-activated cell sorting (FACS) studies.

RESULTS

4-Ethyl-2-hydroxy-2-cyclopentene-1-one, phthalic acid, and 2-hexyl-tetrahydro thiophane were the major compounds in unripe neem seed, whereas 3,5-dihydroxy-6-methyl-2,3-dihydro-4-H-pyran-4-one and 4-ethylbenzamide were predominant in ripe neem seed. Triazine derivatives were also common for both the extracts. MBIC values of unripe and ripe neem seed extracts for S. aureus are 75 and 100 µg/mL, respectively, and for V. cholerae, they are 100 and 300 µg/mL, respectively. MBEC values of unripe and ripe seed extracts are 500 and 300 µg/mL, respectively for S. aureus and for V. cholerae the values are 700 and 500 µg/mL, respectively. Fluorescence microscopic studies at 16 and 24 h, after bacterial culture, demonstrate enhanced antibiofilm activity for the ripe seed extract than that of the unripe seeds for both the bacteria. MTT assay reveals lower cytotoxicity of both the extracts towards normal blood lymphocytes, and anticancer activity against breast cancer cell line (MDA-MB-231) with superior activity of ripe seed extract. FACS studies further supported higher anticancer activity for ripe seed extract.

CONCLUSIONS

Methanolic extract of neem seeds could substantially inhibit and eradicate biofilm along with their potent antibacterial and anticancer activities. Both the extracts showed higher antibiofilm and antibacterial activity against S. aureus (gram-positive) than V. cholerae (gram-negative). Moreover, ripe seed extract showed higher antibiofilm and anticancer activity than unripe extracts.

Correlation between phenotypic virulence traits and antibiotic resistance in Pseudomonas aeruginosa clinical isolates

Pseudomonas aeruginosa is a ubiquitous pathogen capable of infecting virtually all tissues and its one of the standout amongst the most hazardous microorganisms of high morbidity and mortality rates especially in debilitated patients with few successful antibiotic choices available. This pathogen regulating most virulence traits by that so-called quorum sensing (QS), a cell to cell communication system. the present study was intended to phenotypically evaluate the activity of specific virulence traits (including swarming and swimming motility, protease, pyocyanin, and biofilm production) in Pseudomonas aeruginosa clinical isolates and assess the statistical correlation between these traits and antibiotic resistance. One hundred and thirteen bacterial isolates were obtained from different clinical samples and identified as P. aeruginosa, among them, 73.4% have the ability to forming biofilm with different degrees; 59.2% were able to produce pyocyanin pigment while all isolates having the ability to make swarming and swimming motility and able to produce protease enzyme with different degrees. The isolates that produce the higher levels of the virulence traits were identified by both biochemical using Vitek2 automated system and genetically via 16s rRNA gene analysis. The statistical analysis results indicate that a positive significant correlation was found between biofilm formation and other studied virulence traits except for protease (r = 0.584: 0.324, P < 0.05) while a non-significant correlation was found between biofilm formation and protease activity (r = 0.105, P ˃ 0.05). Swimming and swarming motility have a positive significant correlation with other studied virulence traits (r = 0.613: 0.297, P < 0.05) except for protease. Pyocyanin pigment production have a positive significant correlation with other studied virulence traits (r = 0.33: 0.297, P < 0.05) except for protease. on the other hand, negative significant correlations were found between biofilm formation, swimming; and swarming motility, Pyocyanin pigment production, and the susceptibility of antibiotics (r = -0.512: -0.281, P < 0.05). Detection of such correlations in P. aeruginosa is useful for study the behavior of this pathogen and may be provide a new target for the treatment of MDR infections.

Pathogenic Characteristics and Risk Factors for ESKAPE Pathogens Infection in Burn Patients

Objective

This study aimed to determine the clinical manifestations, antimicrobial resistance, molecular characteristics, and risk factors for ESKAPE pathogens infection in burn patients.

Methods

A retrospective study of 187 burn patients infected with ESKAPE pathogens was conducted at the Department of Plastic and Burn Surgery of the Affiliated Hospital of Southwest Medical University (Luzhou, China) from October 2018 to June 2021. All strains were identified using a MicroScan WalkAway 96 Plus System, and antimicrobial susceptibilities were determined using the VITEK system or the disk diffusion method. The antimicrobial resistance genes of multi-drug resistant ESKAPE (MDR-ESKAPE) were detected by polymerase chain reaction (PCR). The multivariable logistic regression analysis was used to estimate the risk factors for ESKAPE infection and MDR-ESKAPE infection.

Results

A total of 255 strains were isolated in various types of clinical specimens from 187 burn patients, of which 47.5% were ESKAPE pathogens (121/255). Among these, MDR-ESKAPE pathogens accounted for 55% (67/121). Additionally, aph3ʹIII, mecA, bla_SHV, bla_TEM, bla_PDC, and bla_SHV were the most prevalent genes detected in Enterococcus faecalis, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp., respectively. The independent risk factors for ESKAPE infection were total body surface area (TBSA) >30–50% (odds ratio [OR] = 10.428; 95% confidence interval [CI], 2.047 to 53.108), TBSA >50% (OR = 15.534; 95% CI, 1.489 to 162.021), and parenteral nutrition (OR = 3.597; 95% CI, 1.098 to 11.787). No independent risk factors were found for MDR-ESKAPE infection.

Conclusion

Clinical staff should be alert to the risk of nosocomial infection with ESKAPE pathogens in burn patients receiving parenteral nutrition and under TBSA >30%. Full attention should also be paid to the ESKAPE resistance, strict adherence to infection control protocols for the rational use of antimicrobial agents, and enhanced clinical standardization of antimicrobial agents management.

Molecular Characterization of Staphylococcus aureus Isolated from Human and Food Samples in Northern Algeria

Staphylococcus aureus is a commensal resident of the skin and nasal cavities of humans and can cause various infections. Some toxigenic strains can contaminate food matrices and cause foodborne intoxications. The present study aimed to provide relevant information (clonal complex lineages, agr types, virulence and antimicrobial resistance-associated genes) based on DNA microarray analyses as well as the origins and dissemination of several circulating clones of 60 Staphylococcus aureus isolated from food matrices (n = 24), clinical samples (n = 20), and nasal carriers (n = 16) in northern Algeria. Staphylococcus aureus were genotyped into 14 different clonal complexes. Out of 60 S. aureus, 13 and 10 isolates belonged to CC1-MSSA and CC97-MSSA, respectively. The CC 80-MRSA-IV was the predominant S. aureus strain in clinical isolates. The accessory gene regulator allele agr group III was mainly found among clinical isolates (70.4%). Panton–Valentine leukocidin genes lukF/lukS-PV were detected in 13.3% of isolates that all belonged to CC80-MRSA. The lukF/S-hlg, hlgA, and hla genes encoding for hemolysins and leucocidin components were detected in all Staphylococcusaureus isolates. Clinical and food isolates harbored more often the antibiotic resistance genes markers. Seventeen (28.3%) methicillin-resistant Staphylococcus aureus carrying the mecA gene localized on a SCCmec type IV element were identified. The penicillinase operon (blaZ/I/R) was found in 71.7% (43/60) of isolates. Food isolates belonging to CC97-MSSA carried several antibiotic resistance genes (blaZ, ermB, aphA3, sat, tetM, and tetK). The results of this study showed that all clones were found in their typical host, but interestingly, some nasal carriers had isolates assigned to CC705 thought to be absent in humans. The detection of MRSA strains among food isolates should be considered as a potential public health risk. Therefore, controlling the antibiotics prescription for a rational use in human and animal infections is mandatory.

Genomic Investigation of Methicillin-Resistant Staphylococcus aureus ST113 Strains Isolated from Tertiary Care Hospitals in Pakistan

Methicillin-resistant Staphylococcus aureus (MRSA) is a multi-drug resistant and opportunistic pathogen. The emergence of new clones of MRSA in both healthcare settings and the community warrants serious attention and epidemiological surveillance. However, epidemiological data of MRSA isolates from Pakistan are limited. We performed a whole-genome-based comparative analysis of two (P10 and R46) MRSA strains isolated from two provinces of Pakistan to understand the genetic diversity, sequence type (ST), and distribution of virulence and antibiotic-resistance genes. The strains belong to ST113 and harbor the SCCmec type IV encoding mecA gene. Both the strains contain two plasmids, and three and two complete prophage sequences are present in P10 and R46, respectively. The specific antibiotic resistance determinants in P10 include two aminoglycoside-resistance genes, aph(3’)-IIIa and aad(6), a streptothrin-resistance gene sat-4, a tetracycline-resistance gene tet(K), a mupirocin-resistance gene mupA, a point mutation in fusA conferring resistance to fusidic acid, and in strain R46 a specific plasmid associated gene ant(4’)-Ib. The strains harbor many virulence factors common to MRSA. However, no Panton-Valentine leucocidin (lukF-PV/lukS-PV) or toxic shock syndrome toxin (tsst) genes were detected in any of the genomes. The phylogenetic relationship of P10 and R46 with other prevailing MRSA strains suggests that ST113 strains are closely related to ST8 strains and ST113 strains are a single-locus variant of ST8. These findings provide important information concerning the emerging MRSA clone ST113 in Pakistan and the sequenced strains can be used as reference strains for the comparative genomic analysis of other MRSA strains in Pakistan and ST113 strains globally.

Antibiotic resistance alters through iron-regulating Sigma factors during the interaction of Staphylococcus aureus and Pseudomonas aeruginosa

Iron is a limiting factor in such a condition that usually is sequestered by the host during polymicrobial infections of Pseudomonas aeruginosa and Staphylococcus aureus. This study aimed to investigate the interaction of S. aureus and P. aeruginosa, which alters iron-related sigma factors regulation and antibiotic resistance. The antibiotic resistance of P. aeruginosa and S. aureus was investigated in a L929 cell culture model. The expression level of pvdS, hasI (P. aeruginosa sigma factors), and sigS (S. aureus sigma factor) genes was determined using Quantitative Real-Time PCR. pvdS and hasI were downregulated during co-culture with S. aureus, while the susceptibility to carbapenems increased (p-value < 0.0001). Also, there was a direct significant relationship between resistance to vancomycin with sigS. Regarding the findings of the current study, iron-related sigma factors of P. aeruginosa and S. aureus play a role in induction susceptibility to various antibiotics, including carbapenems and vancomycin.

Methicillin and Vancomycin Resistant Staphylococcus aureus and Associated Factors from Surgical Ward Inpatients at Debre Markos Referral Hospital, Northwest Ethiopia

Introduction

Staphylococcus aureus is a well-known superbug and leading causes of wound infections. The clinical epidemiology of methicillin resistant S. aureus (MRSA) and vancomycin resistant S. aureus (VRSA) is not well documented in Ethiopia. The aim of this study was to determine the proportion of MRSA, VRSA and associated factors from surgical inpatients in Debre Markos Referral Hospital (DMRH), Northwest Ethiopia.

Methods

A facility-based cross-sectional study was conducted from February to April 2020 at DMRH. A structured questionnaire was used to gather demographic and clinical data. Wound swab was collected from inpatients and then inoculated on blood agar and mannitol salt agar. The presence of MRSA and VRSA was determined using the cefoxitin (30 μg) antibiotic disk diffusion and vancomycin E-test methods, respectively. The data were analyzed using SPSS 20. Data were analyzed using bivariate and multivariate logistic regression analysis. A P-value <0.05 was considered statistically significant.

Results

A total of 242 wound cases were enrolled and the majority of them were males 172 (71.1%). Among the total enrolled cases, S. aureus was identified from 71 (29.3%) of the admitted patients. The proportion of MRSA was 32 (13.22%) and that of VRSA was 4.1%. The proportion of vancomycin intermediate S. aureus (VISA) was gauged at 4.5%. Hospital stay over 72 hrs, wound depth, current antibiotic use, and previous history of wound infection showed statistically significant association with MRSA. On the contrary, VRSA did not showed any significant association against the analyzed variables.

Conclusion

High proportions of S. aureus isolates became MRSA; resistant to all β-lactam antimicrobial agents excluding newer cephalosporin. In addition, the proportion of VRSA/VISA was also high. Multiple variables demonstrated significant associations with MRSA. Hence, intervention measures for MRSA risk groups must be in place. Furthermore, hospital infection control and an antibiotic stewardship program should be strengthened.

Micro-structural investigations on oppositely charged mixed surfactant gels with potential dermal applications

Dicarboxylic amino acid-based surfactants (N-dodecyl derivatives of -aminomalonate, -aspartate, and -glutamate) in combination with hexadecyltrimethylammonium bromide (HTAB) form a variety of aggregates. Composition and concentration-dependent mixtures exhibit liquid crystal, gel, precipitate, and clear isotropic phases. Liquid crystalline patterns, formed by surfactant mixtures, were identified by polarizing optical microscopy. FE-SEM studies reveal the existence of surface morphologies of different mixed aggregates. Phase transition and associated weight loss were found to depend on the composition where thermotropic behaviours were revealed through combined differential scanning calorimetry and thermogravimetric studies. Systems comprising more than 60 mol% HTAB demonstrate shear-thinning behaviour. Gels cause insignificant toxicity to human peripheral lymphocytes and irritation to bare mouse skin; they do not display the symptoms of cutaneous irritation, neutrophilic invasion, and inflammation (erythema, edema, and skin thinning) as evidenced by cumulative irritancy index score. Gels also exhibit substantial antibacterial effects on Staphylococcus aureus, a potent causative agent of skin and soft tissue infections, suggesting its possible application as a vehicle for topical dermatological drug delivery.

The Potential Impact of Moringa oleifera for Diminishing the Microbial Contamination and Prolonging the Quality and Shelf-Life of Chilled Meat

This study was implemented to assess the mechanism by which Moringa oleifera leaf extract (MOLE) improves the quality and prolongs shelf-life of the broilers’ breast meat. Ninety Cobb chicks were randomly allocated to 3 groups. A control group received the standard diet, whereas the other two groups received diets containing MOLE at the doses of 250 and 500 mg/kg for 21 days. Inclusion of MOLE in broilers diet significantly reduced the detrimental changes in the overall sensory attribute scores, characteristic color and odor, and the loss of breast muscle elasticity during storage. Furthermore, it significantly reduced concentrations of thiobarbituric acid, total volatile nitrogen, non-esterified fatty acids, and peroxide, during storage compared to the control samples. No effect on the concentrations of heavy metals, such as copper, cadmium, and lead, was observed. Decomposition of samples was delayed as indicated by lower pH values and higher sensory scores at 4 and 6 days of storage in the MOLE groups. Reduced contamination with E. coli and Salmonella species indicated an antibacterial effect of MOLE. Finally, the present study highlights that MOLE supplementation may play a role in improving quality and shelf-life of the chilled breast meat in broilers.

Isolation, characterisation and antibiotic susceptibility of staphylococcal isolates with special reference to methicillin-resistant Staphylococcus aureus from the anterior nares of healthcare workers in A tertiary healthcare centre

Background: Staphylococcus aureus (S. aureus) and its resistant form methicillinresistant S. aureus (MRSA) is one of the most common nosocomial pathogens causing a wide range of infections in humans. The anterior nares are the main ecological niche for S. aureus. Nasal carriage of S. aureus acts as an important reservoir of infection among the colonised healthcare workers and they transmit the infection to the community. The aim of the present study was to estimate the nasal colonisation of S. aureus (with special reference to MRSA) in healthcare workers (doctors and nursing staff) and its antibiotic susceptibility pattern. Methods: A descriptive study was planned in the Department of Microbiology, JLN Medical College, Ajmer (Rajasthan, India) after due approval from the institutional ethics committee. A total of 170 healthcare workers of either sex aged between 18 to 60 years were screened for S. aureus. Identification was done using standard microbiological techniques, by studying their morphology, colony and biochemical characteristics. MRSA was detected by cefoxitin disc diffusion test, oxacillin disc diffusion test, minimum inhibitory concentration (MIC) of oxacillin by E-test and oxacillin screen agar test. The observations were described in proportions and Chisquared test was used to find independence. Statistical significance was considered at 5 %. Results: Among 170 samples, 159 (93.53 %) samples (50 doctors and 109 nursing staff) had staphylococci colonisation. Among these 159 isolates, 34 (21.38 %) were S. aureus. Further, 8 (5.03 %) S. aureus isolates were resistant to both cefoxitin and oxacillin and had oxacillin MIC values ≥ 4 µg/mL and were considered MRSA. All the MRSA were detected in the nursing staff (males: 5.50 %, females: 1.83 %). All S. aureus and MRSA isolates were found sensitive to linezolid, vancomycin and mupirocin (minimum inhibitory concentration ≤ 4 µg/mL). Conclusion: Screening and treatment of healthcare workers colonised with MRSA should be an important component of hospital infection control policy. These measures will prevent spread of infection to patients and the community and thereby reduce the morbidity, mortality and healthcare costs associated with nosocomial infections.

Benzyl isocyanate isolated from the leaves of Psidium guajava inhibits Staphylococcus aureus biofilm formation

Benzyl isocyanate (BIC), from methanol extract of Psidium guajava leaves, exhibited substantial anti-biofilm activities against Staphylococcus aureus, the common bacterial pathogen in nosocomial infections. Major components of the extract included eugenol, BIC, phenyl-2-methoxy-4-(1-propenyl)-acetate and 2,5-pyrrolidinedione,1-penta-3-4-dienyl, analyzed by GC-MS and HPLC studies. BIC exhibited substantial anti-biofilm activitiy against S. aureus, established by assaying biofilm formation, biofilm metabolic activity, bacterial adherence to hydrocarbons, exopolysaccharide formation, and optical and scanning electron microscopic studies. BIC significantly downregulated the important biofilm markers of S. aureus, viz., icaAD, sarA and agr, observed by quantitative real time polymerase chain reaction analysis. Molecular docking studies revealed thermodynamically favorable interaction of BIC with IcaA, SarA and Agr, having Gibbs energy values of -8.45, -9.09 and -10.29 kcal mol^-1, respectively. BIC after binding to IcaR, the repressor of IcaA, influences its binding to target DNA site (E_shape, -157.27 kcal mol^-1). The results are considered to demonstrate anti-biofilm potential of BIC against bacterial infections.

Diagnostic Values of Multiplex Loop-Mediated Isothermal Amplification and Multiplex Polymerase Chain Reaction for Detection of Methicillin-Resistant Staphylococcus aureus

Background: Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a significant pathogen in community and hospital environments and is associated with high mortality and morbidity. Both polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP) methods are sensitive and acceptable molecular methods for the diagnosis of infectious diseases. Objectives: This study aimed to develop detection assays for Staphylococcal mecA and spa using multiplex PCR and LAMP. Methods: Both methods were standardized, and detection limits were determined using serial dilutions of S. aureus DNA samples. Fifty-three clinical isolates of S. aureus were confirmed to the species level using biochemical tests and multiplex PCR and multiplex LAMP for the spa gene, while disk diffusion, minimum inhibitory concentration, and detection of mecA genes were used for the assessment of methicillin resistance. Results: The PCR could detect the mecA and spa genes at 1 fg/mL and 10 fg/mL of bacterial DNA, which were equal to 35 and 350 gene copy numbers, respectively. Similarly, multiplex LAMP detected the spa and mecA genes at 0.1 fg/mL and 1 fg/mL of bacterial DNA, which were equal to 3.5 and 35 genome copy numbers, respectively. According to MIC and disk diffusion methods, four (7.54%) cases were oxacillin-sensitive methicillin-resistant S. aureus, 16 isolates were methicillin-sensitive, and 37 isolates were methicillin-resistant. According to multiplex PCR, 47.75% of the isolates were mecA-positive while in multiplex LAMP, 41 (35.77%) isolates were mecA-positive. Conclusions: The sensitivity and specificity of the multiplex LAMP were higher than those of multiplex PCR and biochemical methods. Thus, we can apply the LAMP for the routine detection of MRSA.

GLAPD: Whole Genome Based LAMP Primer Design for a Set of Target Genomes

Loop-mediated isothermal amplification (LAMP) technology has been applied in a wide range of fields such as detection of foodborne bacteria and clinical pathogens due to its simplicity and efficiency. However, existing LAMP primer designing systems require a conserved gene or a short genome region as input, and they can’t design group-specific primers. With the growing number of whole genomes available, it is possible to design better primers to target a set of genomes with high specificity based on whole genomes. We present here a whole Genome based LAMP primer designer (GLAPD), a new system to design LAMP primer for a set of target genomes using whole genomes. Candidate single primer regions are identified genome wide and then combined into LAMP primer sets. For a given set of target genomes, only primer sets amplifying them and only these genomes will be output. In order to accelerate the primer designing, a GPU version is provided as well. The effectiveness of primers designed by GLAPD has been assessed for a wide range of foodborne bacteria. GLAPD can be accessed at http://cgm.sjtu.edu.cn/GLAPD/ or https://github.com/jiqingxiaoxi/GLAPD.git. A simple online version is also supplied to help users to learn and test GLAPD: http://cgm.sjtu.edu.cn/GLAPD/online/.

An Autopsy Case of Rupture of Infectious Thoracic Aortitis Induced by Methicillin-Resistant Staphylococcus Aureus

Patient: Female, 83

Final Diagnosis: Rupture of infectious thoracic aortitis

Symptoms: Cardiac pulmonary arrest

Medication: —

Clinical Procedure: Medication

Specialty: Pathology

Alternative sigma factor B (σB) and catalase enzyme contribute to Staphylococcus epidermidis biofilm's tolerance against physico-chemical disinfection

Staphylococcus epidermidis is the predominant cause of recalcitrant biofilm-associated infections, which are often highly resistant to antibiotics. Thus, the use of physico-chemical agents for disinfection offers a more effective approach to the control of S. epidermidis biofilm infections. However, the underlying tolerance mechanisms employed by S. epidermidis biofilm against these physico-chemical disinfectants remain largely unknown. The expression of a σ^B-dependent gene, alkaline shock protein 23 (asp23) and catalase activity by S. epidermidis biofilm and planktonic cells exposed to heat (50 °C), 0.8 M sodium chloride (NaCl), 5 mM sodium hypochlorite (NaOCl) or 50 μM hydrogen peroxide (H₂O₂) for 60 minutes were compared. Significantly higher asp23 expression levels were observed in biofilms exposed to 50 °C, 5 mM NaOCl or 50 μM H₂O₂ compared to the corresponding planktonic cells (p < 0.05). Conversely, asp23 expression levels in biofilm and planktonic cells exposed to 0.8 M NaCl were not significantly different (p > 0.05). Further, biofilms exposed to 50 °C, 0.8 M NaCl, 5 mM NaOCl or 50 μM H₂O₂ exhibited significantly higher catalase activity than the planktonic cells (p < 0.05). These results suggest that activities of σ^B and catalase may be involved in the tolerance of S. epidermidis biofilm against physico-chemical disinfection.

Essential Oil, Extracts, and Sesquiterpenes Obtained From the Heartwood of Pilgerodendron uviferum Act as Potential Inhibitors of the Staphylococcus aureus NorA Multidrug Efflux Pump

Staphylococcus aureus is a serious human pathogen that is highly adaptive to environmental conditions and rapidly develops antibiotic resistance. The use of efflux pumps to reduce antibiotic concentrations at the intracellular level is one of the main mechanisms by which bacteria develop antibiotic resistance. The management of efflux pumps, specifically NorA, which is expressed by S. aureus strains, is a valuable strategy for restoring susceptibility in strains resistant to antibacterial agents. In recent years, many studies have focused on searching for natural substances that can reverse efflux pump-mediated resistance in S. aureus. Extracts and compounds obtained from plants can be efficient efflux pump inhibitors (EPIs) and represent a potentially patient-friendly strategy for controlling S. aureus. In the present study, we evaluated the ability of essential oils, petroleum ether extracts, dichloromethane extract (DCME) and six compounds isolated from the heartwood of Pilgerodendron uviferum (Cupressaceae) and two synthetic derivatives to inhibit efflux in NorA pumps in the following three S. aureus strains: K2378, which overexpressed the norA gene (norA++), K1902 (norA-deleted, ΔnorA) and the parental strain, NCTC 8325-4. Efflux activity was evaluated using a fluorometric method that measured the accumulation of the universal efflux pump substrate ethidium bromide (EtBr). Only DCME and the compounds 15-copaenol and epi-cubenol inhibited EtBr efflux by K2378. Even the lowest concentration of 15-copaenol exhibited a stronger inhibitory effect than carbonyl cyanide m-chlorophenyl hydrazone on EtBr efflux by K2378. 15-copaenal only showed inhibition of EtBr efflux in K2378 cells at 125 μg/mL, but not superior to the control inhibitor and 15-copaenyl acetate exerted no intrinsic EPI activity against K2378. Fractional inhibitory concentration index (FICI) values obtained in the checkerboard assays, indicated that all combinations between DCME, epi-cubenol and 15-copaenol, and tested antibiotics showed a synergistic effect in wild type, norA ++ and ΔnorA strains. Moreover, those were not toxic for the HeLa cell line at concentrations in which the synergistic effect and inhibitory activity of efflux pumps was determined. Other extracts and compounds obtained from P. uviferum did not display EtBr efflux-inhibiting activity against the evaluated S. aureus strains.

Emerging of antimicrobial resistance in staphylococci isolated from clinical and food samples in Algeria

Objective

The antimicrobial resistance of staphylococci rose worldwide. In total, 96 Staphylococcus isolates from food and clinical samples were collected from two provinces in Algeria. The antimicrobial susceptibility testing was performed and resistance-associated genes were detected.

Results

Fifty-one strains were isolated from food samples and differentiated into 33 Staphylococcus aureus and 18 coagulase-negative staphylococci. Forty-five staphylococci were collected from hospital and community-acquired infection cases. All S. aureus isolated from food were resistant to penicillin and 45.5% were resistant to tetracycline. The resistance rates of 45 clinical Staphylococcus isolates were 86.7%, 48.9%, 37.8% and 20.0% to penicillin, tetracycline, erythromycin and kanamycin, respectively. Nine isolates were confirmed as MRSA from food and clinical isolates. One S. aureus originated from food was confirmed as vancomycin-resistant. Multidrug-resistance was observed among 25.5% and 53.3% of food and clinical staphylococci, respectively. The tetM/K, blaZ, aacA-aphD, ermC and mecA genes were detected in food and clinical isolates. ermA gene was not found. This study provided insight into the status of antimicrobial resistance of staphylococci isolated from food and clinical samples in Algeria. Further investigations and surveillance programmes are mandatory.

Prevalence of Panton-Valentine Leukocidin Gene among Community Acquired Staphylococcus aureus: A Real-Time PCR Study

Panton-Valentine leukocidin (luk-pv) is a cytotoxin that causes leukocyte destruction and tissue necrosis. The aim of this study was to determine the prevalence of the pv1, mecA, and nuc genes in Staphylococcus aureus isolates obtained from anterior nares and superficial infection sites of skin in a slum population of West Bengal, India. Expression level of pv1 gene was also analysed. Twenty-two S. aureus strains were isolated, and phenotype and genotype specific examinations for S. aureus isolates were carried out. Molecular identification was done by PCR using species-specific 16S rRNA primer pairs and finally 22 isolates were found to be positive as S. aureus. The antibiotic responsiveness of all these isolates and the minimum inhibitory concentration (MIC) of MRSA isolates were determined using the broth dilution method with vancomycin. Antibiogram analysis of isolated S. aureus strains with respect to different antimicrobial agents revealed antibiotic resistance ranging from 27 to 91%. The results of MIC for vancomycin showed 95% of strains to be VSSA and 5% to be VISA. 68% isolates were resistant to methicillin. All the isolates were subjected to detection of pv1, mecA, and nuc genes, and 9%, 68%, and 27% were found to harbour pvl, mecA, and nuc genes, respectively. All the MRSA strains produced high to moderate levels of biofilm. pvl gene expression was carried out in vitro by Real-Time PCR. The low ∆Ct value (0.493) was indicative of high expression of pvl in one S. aureus strain. Thus, detection of pvl gene in community acquired S. aureus indicates the emergence of pathogenic S. aureus in community setup in the studied region. The existing exploration is extremely imperative and informative for the high level multi-drug resistant S. aureus infections inclusive of MRSA.

Simultaneous Detection of Nine Key Bacterial Respiratory Pathogens Using Luminex xTAG® Technology

Early diagnosis and treatment are crucial to the outcome of lower respiratory tract infections (LRTIs). In this study, we developed an assay combining multiplex PCR and Luminex technology (MPLT) for the detection of nine important respiratory bacterial pathogens, which frequently cause LRTIs. These were Streptococcus pneumoniae, Moraxella catarrhalis, Staphylococcus aureus, Streptococcus pyogenes, Haemophilus influenzae, Mycoplasma pneumoniae, Legionella spp., Pseudomonas aeruginosa, and Klebsiella pneumoniae. Through the hybridization reaction between two new synthesized multiplex PCR products and MagPlex-TAG Microspheres, we demonstrate that the detection limits for these nine pathogens were as low as 10²–10³ CFU/mL. Furthermore, 86 clinical bronchoalveolar lavage fluid specimens were used to evaluate this method. Compared with the results of nine simplex real-time PCR reactions targeting these nine pathogens, this MPLT assay demonstrated a high diagnostic accuracy for Streptococcus pneumoniae (sensitivity, 87.5% and specificity, 100%). Furthermore, sensitivity and specificity for the other eight pathogens all attained 100% diagnostic accuracy. In addition, the consistency between MPLT and the nine real-time PCR reactions exceeded 98.8%. In conclusion, MPLT is a high-throughput, labor-saving and reliable method with high sensitivity and specificity for identifying nine respiratory pathogens responsible for LRTIs. Indeed, this assay may be a promising supplement to conventional methods used to diagnose LRTIs.