The role of femA regulating gene on methicillin-resistant Staphylococcus aureus clinical isolates

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus among Patients Diagnosed with Surgical Site Infection at Four Hospitals in Ethiopia

Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of severe surgical site infections (SSI). The molecular epidemiology of MRSA is poorly documented in Ethiopia. This study is designed to determine the prevalence of MRSA and associated factors among patients diagnosed with SSI. A multicenter study was conducted at four hospitals in Ethiopia. A wound culture was performed among 752 SSI patients. This study isolated S. aureus and identified MRSA using standard bacteriology, Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS), and cefoxitin disk diffusion test. The genes mecA, femA, vanA, and vanB were detected through PCR tests. S. aureus was identified in 21.6% of participants, with 24.5% of these being methicillin-resistant Staphylococci and 0.6% showing vancomycin resistance. Using MALDI-TOF MS for the 40 methicillin-resistant Staphylococci, we confirmed that 31 (77.5%) were S. aureus, 6 (15%) were Mammaliicoccus sciuri, and the other 3 (2.5%) were Staphylococcus warneri, Staphylococcus epidermidis, and Staphylococcus haemolyticus. The gene mecA was detected from 27.5% (11/40) of Staphylococci through PCR. Only 36.4% (4/11) were detected in S. aureus, and no vanA or vanB genes were identified. Out of 11 mecA-gene-positive Staphylococci, 8 (72.7%) were detected in Debre Tabor Comprehensive Specialized Hospital. Methicillin-resistant staphylococcal infections were associated with the following risk factors: age ≥ 61 years, prolonged duration of hospital stay, and history of previous antibiotic use, p-values < 0.05. Hospitals should strengthen infection prevention and control strategies and start antimicrobial stewardship programs.

Single-cell scattering and auto-fluorescence-based fast antibiotic susceptibility testing for gram-negative and gram-positive bacteria

In this study, we assess the scattering of light and auto-fluorescence from single bacterial cells to address the challenge of fast (<2 h), label-free phenotypic antimicrobial susceptibility testing (AST). Label-free flow cytometry is used for monitoring both the respiration-related auto-fluorescence in two different fluorescence channels corresponding to FAD and NADH, and the morphological and structural information contained in the light scattered by individual bacteria during incubation with or without antibiotic. Large multi-parameter data are analyzed using dimensionality reduction methods, based either on a combination of 2D binning and Principal Component Analysis, or with a one-class Support Vector Machine approach, with the objective to predict the Susceptible or Resistant phenotype of the strain. For the first time, both Escherichia coli (Gram-negative) and Staphylococcus epidermidis (Gram-positive) isolates were tested with a label-free approach, and, in the presence of two groups of bactericidal antibiotic molecules, aminoglycosides and beta-lactams. Our results support the feasibility of label-free AST in less than 2 h and suggest that single cell auto-fluorescence adds value to the Susceptible/Resistant phenotyping over single-cell scattering alone, in particular for the mecA+ Staphylococcus (i.e., resistant) strains treated with oxacillin.

Recent Progress in the Diagnosis of Staphylococcus in Clinical Settings

Staphylococci are mainly found on the skin or in the nose. These bacteria are typically friendly, causing no harm to healthy individuals or resulting in only minor issues that can go away on their own. However, under certain circumstances, staphylococcal bacteria could invade the bloodstream, affect the entire body, and lead to life-threatening problems like septic shock. In addition, antibiotic-resistant Staphylococcus is another issue because of its difficulty in the treatment of infections, such as the notorious methicillin-resistant Staphylococcus aureus (MRSA) which is resistant to most of the currently known antibiotics. Therefore, rapid and accurate diagnosis of Staphylococcus and characterization of the antibiotic resistance profiles are essential in clinical settings for efficient prevention, control, and treatment of the bacteria. This chapter highlights recent advances in the diagnosis of Staphylococci in clinical settings with a focus on the advanced technique of surface-enhanced Raman spectroscopy (SERS), which will provide a framework for the real-world applications of novel diagnostic techniques in medical laboratories via bench-top instruments and at the bedside through point-of-care devices.

Ultrastructural changes in methicillin-resistant Staphylococcus aureus (MRSA) induced by a novel cyclic peptide ASP-1 from Bacillus subtilis: A scanning electron microscopy (SEM) study

Increasing antimicrobial resistance among Staphylococcus aureus necessitates a new antimicrobial with a different site of action. We have isolated a novel cyclic peptide-1 (ASP-1) from Bacillussubtilis with potent activity against methicillin-resistant S. aureus (MRSA) at a minimum inhibitory concentration (MIC) of 8-64μg/ml. Scanning electron micrographs demonstrated drastic changes in the cellular architecture of ASP-1 treated cells of S. aureus ATCC 29213 and an MRSA clinical isolate at MICs, with damages to the cell wall, membrane lysis and probable leakage of cytoplasmic contents at minimum bactericidal concentrations. The ultrastructure alterations induced by ASP-1 have also been compared with those of oxacillin-treated MRSA cells at its MIC using scanning electron microscopy.

Decreased expression of femXAB genes and fnbp mediated biofilm pathways in OS-MRSA clinical isolates

Methicillin-Resistant Staphylococcus aureus (MRSA) is a significant threat to human health. Additionally, biofilm forming bacteria becomes more tolerant to antibiotics and act as bacterial reservoir leading to chronic infection. In this study, we characterised the antibiotic susceptibility, biofilm production and sequence types (ST) of 74 randomly selected clinical isolates of S. aureus causing ocular infections. Antibiotic susceptibility revealed 74% of the isolates as resistant against one or two antibiotics, followed by 16% multidrug-resistant isolates (MDR), and 10% sensitive. The isolates were characterized as MRSA (n = 15), Methicillin-sensitive S. aureus (MSSA, n = 48) and oxacillin susceptible mecA positive S. aureus (OS-MRSA, n = 11) based on oxacillin susceptibility, mecA gene PCR and PBP2a agglutination test. All OS-MRSA would have been misclassified as MSSA on the basis of susceptibility test. Therefore, both phenotypic and genotypic tests should be included to prevent strain misrepresentation. In addition, in-depth studies for understanding the emerging OS-MRSA phenotype is required. The role of fem XAB gene family has been earlier reported in OS-MRSA phenotype. Sequence analysis of the fem XAB genes revealed mutations in fem × (K3R, H11N, N18H and I51V) and fem B (L410F) genes. The fem XAB genes were also found down-regulated in OS-MRSA isolates in comparison to MRSA. In OS-MRSA isolates, biofilm formation is regulated by fibronectin binding proteins A & B. Molecular typing of the isolates revealed genetic diversity. All the isolates produced biofilm, however, MRSA isolates with strong biofilm phenotype represent a worrisome situation and may even result in treatment failure.

Determining the prevalence of SCCmec polymorphism, virulence and antibiotic resistance genes among methicillin-resistant Staphylococcus aureus (MRSA) isolates collected from selected hospitals in west of Iran

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important pathogens worldwide and compared to other staphylococcal species that are associated with higher mortality rate. A total of 500 Staphylococcus spp. was collected from selected hospitals in Ilam, Kermanshah, Khorram Abad and Hamadan cities and, via phenotypic and genotypic methods, was assessed to find MRSA. The presence or absence of prevalent antibiotic resistance genes and virulence genes was evaluated among MRSA isolates, using polymerase chain reaction (PCR) method, and then the SCCmec typing of these isolates was assayed by multiplex PCR. A total of 372 (74.4%) Stapylococcus spp. isolates were identified as S. aureus, among which 200 (53.8%) possessed the mecA gene and were distinguished as MRSA. All of MRSA isolates contained blaZ gene. The frequency of ermA and ermC genes among erythromycin-resistant MRSA isolates was 21.6% and 66.7%, respectively. The frequency of the virulence genes eta, hla and sea among MRSA isolates was 10%, 80.5% and 100%, respectively. SCCmec type IV accounted for 30.6% of the MRSA isolates and SCCmec type III, SCCmec type II and SCCmec type I accounted for 30%, 22% and 17.5% of the isolates, respectively. The antibiotic resistance genes and the virulence genes of blaZ, hla, sea, eta and ermC had high frequencies among the MRSA isolates. This study showed that the antibiotic resistance genes had higher frequencies among SCCmec types I and IV, which confirms the previous reports in this field.

Overcoming resistance to β-lactam antibiotics

β-Lactam antibiotics are one of the most important antibiotic classes but are plagued by problems of resistance, and the development of new β-lactam antibiotics through side-chain modification of existing β-lactam classes is not keeping pace with resistance development. In this JOCSynopsis, we summarize small molecule strategies to overcome resistance to β-lactam antibiotics. These approaches include the development of β-lactamase inhibitors and compounds that interfere with the ability of the bacteria to sense an antibiotic threat and activate their resistance mechanisms.