Vancomycin-resistant Staphylococci Research Articles

Radiology Department: A Potential Source of Multidrug-Resistant Microorganisms: A Cross-Sectional Study at Tertiary Hospital, Palestine.

Globally, healthcare facilities face a great challenge in the form of hospital-acquired infections (HAIs). Aside from the morbidity and mortality they cause, these illnesses are also extremely costly. Research on infection transmission in the medical field has been considerable, but not so much in the radiology department. This study aims to identify the presence of multidrug-resistant (MDR) microbes on surfaces that are frequently touched in computed tomography (CT), magnetic resonance imaging (MRI), ultrasound (US), plain X-ray examination rooms, and portable radiography that are susceptible to contamination as well as to investigate the potential dangers of contracting MDR organisms to patients and healthcare providers. Materials and Method. In this study, 160 swab samples were collected from the radiology department during May and June 2022. Samples were obtained from 80 predefined surfaces twice within and outside of CT and MRI examination rooms as well as from US and plain X-ray machines and portable X-ray machines. Samples were taken at 7:00 a.m. using cotton swabs following the regular cleaning procedure. Bacterial colony-forming units (CFUs) per square centimeter were calculated after swabbing a 100 cm2 surface. Nearly all of the surfaces tested had bacterial CFUs. The highest contamination rate was found on keyboards ranging from (1.2-8) CFU/cm2, the sides of patient tables (1.2-20) CFU/cm2, knee coil (2.4-3) CFU/cm2, and patient leg supports (1.2-8) CFU/cm2. A noticeable increase in the contamination was noticed in June compared to May, and this was consistent with the increase in the number of isolated patients in the hospital, the workload in the radiology department, and the number of patients referred to the hospital. In our study, none of the examined sites showed contamination with MDR Gram-negative bacteria such as extended-spectrum beta-lactamases producing Enterobacterales (ESPL) or Carbapenemase-producing Enterobacterales (CPE). On the other hand, methicillin-resistant Staphylococcus (MRS), vancomycin-resistant Staphylococcus (VRS), and vancomycin-resistant Enterococcus (VRE) were detected. All of the radiology department equipment and sites could be a source of bacterial infection including MDR, so the obligatory and committed disinfection protocol must be revised and implemented in the morning and between patients.

Evaluation of Rational Use of Linezolid in Hospitalized Patient in Shahid Chamran Hospital in Isfahan City during the Second Six Months of the 2021

Introduction: The rational use of drugs is one of the main elements of achieving the best pharmacotherapy method for patients. Linezolid is used for infections caused by gram-positive bacteria, including vancomycin-resistant staphylococci and vancomycin-resistant enterococci, but the inappropriate use of this drug has led to the emergence of linezolid-resistant strains. The purpose of this study was to investigate the manner of Linezolid prescription in Shahid Chamran Hospital of Isfahan City in 2021.
 Methods: This cross sectional study was conducted during a period of 6 months (From September 1, 2021 to February 31, 2022) on 102 patients admitted to Shahid Chamran Hospital in Isfahan City. Patient information such as demographic information, indication and dosages of drugs, the basis of drug prescription, side effects and drug interactions, etc. were extracted from the medical records of patients and hospital systems and recorded in designed forms. After matching the information with the relevant guidelines, statistical analysis was performed using SPSS-16 software.
 Results: Out of the 102 patients, who received linezolid, 75.1% were men and the rest were women. 99% of the cases were prescribed experimentally and 1% was based on culture. In 40.2% of the patients, drugs were prescribed irrationally in terms of prescription indications. In 84.3% of the cases, a change in treatment regimen was observed after receiving the culture results.
 Conclusion: A large percentage of cases of linezolid drug prescription was not done correctly. Furthermore, it has not been attention to the side effects caused by the drug, especially thrombocytopenia.

Shapeshifting bullvalene-linked vancomycin dimers as effective antibiotics against multidrug-resistant gram-positive bacteria

The alarming rise in superbugs that are resistant to drugs of last resort, including vancomycin-resistant enterococci and staphylococci, has become a significant global health hazard. Here, we report the click chemistry synthesis of an unprecedented class of shapeshifting vancomycin dimers (SVDs) that display potent activity against bacteria that are resistant to the parent drug, including the ESKAPE pathogens, vancomycin-resistant Enterococcus (VRE), methicillin-resistant Staphylococcus aureus (MRSA), as well as vancomycin-resistant S. aureus (VRSA). The shapeshifting modality of the dimers is powered by a triazole-linked bullvalene core, exploiting the dynamic covalent rearrangements of the fluxional carbon cage and creating ligands with the capacity to inhibit bacterial cell wall biosynthesis. The new shapeshifting antibiotics are not disadvantaged by the common mechanism of vancomycin resistance resulting from the alteration of the C-terminal dipeptide with the corresponding d-Ala-d-Lac depsipeptide. Further, evidence suggests that the shapeshifting ligands destabilize the complex formed between the flippase MurJ and lipid II, implying the potential for a new mode of action for polyvalent glycopeptides. The SVDs show little propensity for acquired resistance by enterococci, suggesting that this new class of shapeshifting antibiotic will display durable antimicrobial activity not prone to rapidly acquired clinical resistance.

Improving theantimicrobial activity of oldantibacterial drug mafenide: Schiff bases and their bioactivity targeting resistant pathogens.

Background: Increasing rates of acquired resistance have justified the critical need for novel antimicrobial drugs. One viable concept is the modification of known drugs. Methods & results: 21 mafenide-based compounds were prepared via condensation reactions and screened for antimicrobial efficacy, which demonstrated promising activity against both Gram-positive and Gram-negative pathogens, pathogenic fungi and mycobacterial strains (minimum inhibitory concentrations from 3.91μM). Importantly, they retained activity against a panel of superbugs (methicillin- and vancomycin-resistant staphylococci, enterococci, multidrug-resistant Mycobacterium tuberculosis) without any cross-resistance. Unlike mafenide, most of its imines were bactericidal. Toxicity to HepG2 cells was also investigated. Conclusion: Schiff bases were significantly more active than the parent drug, with iodinated salicylidene and 5-nitrofuran/thiophene-methylidene scaffolds being preferred in identifying the most promising drug candidates.

EVALUATING THE CHANGING TRENDS IN EMERGENCE OF MULTIDRUG RESISTANCE AMONG GRAM POSITIVE ORGANISMS ISOLATED FROM SKIN AND SOFT TISSUE INFECTIONS FROM A TERTIARY CARE HOSPITAL, JHARKHAND

Drug resistance among gram positive aerobic cocci poses a significant problem in management of patients with skin and soft tissue infections (SSTI's). S. aureus is the most common organism that causes mild skin and soft tissue infections to serious infections such as sepsis and toxic shock syndrome. Enterococcus and Streptococcus species have also emerged as a cause of skin and soft tissue infections and health care associated infections (HAI's). SSTI's is an inflammatory microbial invasion of epidermis, dermis and subcutaneous tissue. It is classified according to the layer of infection, severity of infection and microbiologic etiology. The practice guidelines of the Infectious Disease Society of America (IDSA) for the diagnosis and management of skin and soft tissue infection classifies SSTI's into five categories comprising superficial and complicated infections which include impetigo, erysipelas, cellulitis, necrotizing fasciitis, surgical site infection. Risk factors associated with development of SSTI's include poor hygiene, overcrowding, co- morbidities like diabetes, immunocompromised state, overuse of antibiotics, prolonged hospital stay, burn patients etc. Prompt recognition, timely surgical debridement or drainage with appropriate antibiotic therapy is the mainstay treatment for SSTI's. Empirical therapy includes penicillin, cephalosporins, clindamycin and cotrimoxazole. Multi-Drug resistance is of major concern commonly caused by MRSA (Methicillin resistant staphylococcus aureus) which includes CA-MRSA (Community acquired methicillin resistant Staphylococcus aureus), HA-MRSA (hospital acquired methicillin resistant Staphylococcus aureus), VRSA (vancomycin resistant staphylococcus aureus) & VRE (vancomycin resistant Enterococci). HA-MRSA is generally susceptible to clindamycin, vancomycin, Linezolid & trimethoprim- sulfamethoxazole. In contrast, CA-MRSA is usually sensitive to these former antibiotics as well as broader range of oral antimicrobial agents like clindamycin, linezolid, quinolones, daptomycin, tigecycline etc. These empirical therapeutic agents provide coverage for both S. aureus, Streptococcus species and Enterococcus species. Therefore, demographic knowledge of antimicrobial agents and their resistance pattern plays a significant role in management of SSTI's.

Enterotoxin- and Antibiotic-Resistance-Encoding Genes Are Present in Both Coagulase-Positive and Coagulase-Negative Foodborne Staphylococcus Strains

Food poisoning by staphylococcal enterotoxins (SE) is a major cause of foodborne illness, often associated with coagulase-positive staphylococci (CPS). The increase in the number of methicillin-resistant Staphylococcus aureus (MRSA) strains is another major problem associated with CPS. However, reports of the association of SE and methicillin-resistant Staphylococcus with coagulase-negative staphylococci (CNS) are beginning to re-emerge. In this context, the aim of this study is to investigate the presence of staphylococcal enterotoxin genes and to characterize the phenotypic and genotypic antimicrobial resistance in 66 isolates of Staphylococcus spp. (47 CNS and 19 CPS) recovered from ready-to-eat (RTE) street food sold in Maputo, Mozambique. Seven virulence genes encoding SE (sea, seb, sec, sed and see) and two toxins (hlb and sak) were screened by multiplex PCR (MPCR). Antimicrobial resistance against 12 antibiotics was evaluated by the disk diffusion method. The presence of genes encoding resistance to penicillin, methicillin, vancomycin and erythromycin (blaZ, mecA, vancA, vancB, ermA, ermB and ermC) were also screened by PCR. At least one of the seven virulence genes assessed in this study was detected in 57.9% and 51% of CPS and CNS isolates, respectively. In CPS isolates, the most frequent gene was hlb (47.4%), followed by sec (15.8%) and sea, seb and sed genes with 5.3% each. In CNS isolates, the most frequent gene was sec (36.2%) followed by sak (17%), hlb (14.9%), sed (12.8%) and seb (6.4%). Five of the twelve CPS in which virulence genes were detected were also antibiotic-resistant. All the CNS isolates harboring virulence genes (n = 27, 57.4%) were antimicrobial-resistant. The prevalence of multidrug resistance was higher (59.6%) in CNS than in CPS (26.3%) isolates. Regarding the presence of antibiotic-resistance genes, blaZ (penicillin-resistant) was the most frequent in both CPS (42.1%) and CNS (87.2%), followed by the mecA (encoding methicillin resistance) and vancA genes (vancomycin-resistant), which represented 36.8% and 31.6% in CPS isolates and 46.8% in CNS isolates, respectively. The prevalence of vancomycin-resistant staphylococci has been increasing worldwide and, to our knowledge, this is the first study to report the occurrence of vancomycin-resistant staphylococci in Mozambique. These results emphasize the need to investigate CNS isolates in parallel with CPS, as both constitute public health hazards, given their potential to produce SE and spread antimicrobial resistance genes.

Alkyl-Aryl-Vancomycins: Multimodal Glycopeptides with Weak Dependence on the Bacterial Metabolic State.

Resistance to last-resort antibiotics such as vancomycin for Gram-positive bacterial infections necessitates the development of new therapeutics. Furthermore, the ability of bacteria to survive antibiotic therapy through formation of biofilms and persister cells complicates treatment. Toward this, we report alkyl-aryl-vancomycins (AAVs), with high potency against vancomycin-resistant enterococci and staphylococci. Unlike vancomycin, the lead compound AAV-qC10 was bactericidal and weakly dependent on bacterial metabolism. This resulted in complete eradication of non-growing cells of MRSA and disruption of its biofilms. In addition to inhibiting cell wall biosynthesis like vancomycin, AAV-qC10 also depolarizes and permeabilizes the membrane. More importantly, the compound delocalized the cell division protein MinD, thereby impairing bacterial growth through multiple pathways. The potential of AAV-qC10 is exemplified by its superior efficacy against MRSA in a murine thigh infection model as compared to vancomycin. This work paves the way for structural optimization and drug development for combating drug-resistant bacterial infections.

PAMAM dendrimers with dual-conjugated vancomycin and Ag-nanoparticles do not induce bacterial resistance and kill vancomycin-resistant Staphylococci

The effective life-time of new antimicrobials until the appearance of the first resistant strains is steadily decreasing, which discourages incentives for commercialization required for clinical translation and application. Therefore, development of new antimicrobials should not only focus on better and better killing of antimicrobial-resistant strains, but as a paradigm shift on developing antimicrobials that prevent induction of resistance. Heterofunctionalized, poly-(amido-amine) (PAMAM) dendrimers with amide-conjugated vancomycin (Van) and incorporated Ag nanoparticles (AgNP) showed a 6–7 log reduction in colony-forming-units of a vancomycin-resistant Staphylococcus aureus strain in vitro, while not inducing resistance in a vancomycin-susceptible strain. Healing of a superficial wound in mice infected with the vancomycin-resistant S. aureus was significantly faster and more effective by irrigation with low-dose, dual-conjugated Van-PAMAM-AgNP dendrimer suspension than by irrigation with vancomycin in solution or a PAMAM-AgNP dendrimer suspension. Herewith, dual-conjugation of vancomycin together with AgNPs in heterofunctionalized PAMAM dendrimers fulfills the need for new, prolonged life-time antimicrobials killing resistant pathogens without inducing resistance in susceptible strains. Important for clinical translation, this better use of antibiotics can be achieved with currently approved and clinically applied antibiotics, provided suitable for amide-conjugation.

Antibiotics in Bone Cements Used for Prosthesis Fixation: An Efficient Way to Prevent Staphylococcus aureus and Staphylococcus epidermidis Prosthetic Joint Infection.

Prosthetic joint infections (PJIs) are one of the most frequent reasons for arthroplasty revision. These infections are mostly associated with the formation of biofilm, notably by staphylococci, such as Staphylococcus aureus and Staphylococcus epidermidis. To minimize the rates of PJIs following primary or revision total joint arthroplasty, antibiotic-loaded bone cements (ALBCs) can be used for prosthesis fixation. However, its use is still debated. Indeed, various studies reported opposite results. In this context, we aimed to compare the prophylactic anti-biofilm activity of ALBCs loaded with two antibiotics with ALBC loaded with only one antibiotic. We compared commercial ready-to-use cements containing gentamicin alone, gentamicin plus vancomycin, and gentamicin plus clindamycin to plain cement (no antibiotic), investigating staphylococcal biofilm formation for 10 strains of S. aureus and S. epidermidis with specific resistance to gentamicin, vancomycin, or clindamycin. Firstly, we performed disk diffusion assays with the elution solutions. We reported that only the cement containing gentamicin and clindamycin was able to inhibit bacterial growth at Day 9, whereas cements with gentamicin only or gentamicin and vancomycin lost their antibacterial activity at Day 3. Then, we observed that all the tested ALBCs can inhibit biofilm formation by methicillin-susceptible staphylococci without other antibiotic resistance ability. Similar results were observed when we tested vancomycin-resistant or clindamycin-resistant staphylococci, with some strain-dependent significant increase of efficacy for the two antibiotic ALBCs when compared with gentamicin-loaded cement. However, adding vancomycin or clindamycin to gentamicin allows a better inhibition of biofilm formation when gentamicin-resistant strains were used. Our in vitro results suggest that using commercially available bone cements loaded with gentamicin plus vancomycin or clindamycin for prosthesis fixation can help in preventing staphylococcal PJIs following primary arthroplasties, non-septic revisions or septic revisions, especially to prevent PJIs caused by gentamicin-resistant staphylococci.

Evaluation of fosfomycin combined with vancomycin against vancomycin-resistant coagulase negative staphylococci

The pathogenic potential of coagulase-negative staphylococci (CoNS) is increasingly recognized worldwide. The aim of the present study was to evaluate different combinations of fosfomycin (FOS) with vancomycin (VAN) or oxacillin (OXA) against vancomycin-resistant clinical isolates of CoNS. Characterization of VAN resistance in selected isolates was also sought. Antibiotic susceptibility of isolates was tested by disc diffusion method, MICs of antibiotics were determined by the agar dilution method, and fosfomycin combinations were evaluated by a time-kill assay according to the guidelines of the CLSI. Moreover, oxacillin and glycopeptides (vancomycin and teichoplanin) resistances were also characterized phenotypically and genotypically in this study. Out of 258 staphylococci, 52 were CoNS (20.2%). All isolates were multidrug resistant with 75% (n = 39) oxacillin-resistant, most of them with oxacillin MIC levels of >32 mg/L. Moreover, vancomycin non-susceptibility was observed in 46.2% (n = 24) of the tested isolates with MIC range of 4-32 mg/L. Identification of selected isolates revealed that S. epidermidis was the most abundant among tested CoNS, followed by S. hominis, S. saprophyticus, and interestingly S. caseolyticus. Furthermore, Synergistic and bactericidal effects of FOS + VAN combination were observed in 3 of 9 isolates after 6 h of treatment and in all studied isolates at 24 h. On the other hand, FOS + OXA combinations were ineffective. This study provides evidence that fosfomycin combination with vancomycin could be considered as a therapeutic alternative for CoNS infections. It also sheds some light on the possible emergence of the otherwise harmless bacterium S. caseolyticus as a human pathogen.

Prevalence and phylogenetic relationship among methicillin- and vancomycin-resistant Staphylococci isolated from hospital's dairy food, food handlers, and patients.

Objective:The aim of the present work was to investigate the mutual role that may be played by the served dairy food and food handlers in the transmission of methicillin- and vancomycin-resistant Staphylococcus aureus and coagulase-negative Staphylococci to patients who were hospitalized in Qena City, Egypt.Materials and Methods:A total of 210 samples including 90 dairy food samples which offered to the patients in the hospital, 60 nasal and hand swabs from food handlers working in the hospital, and 60 nasal and diarrheal swabs from patients suffering from diarrhea were investigated for the presence of coagulase-positive S. aureus and coagulase-negative Staphylococci, then isolates were screened for methicillin and vancomycin resistance phenotypically and genotypically. 16s rRNA gene sequencing was employed to construct the neighbor-joining tree.Results:Unlike food samples, both coagulase-positive S. aureus and coagulase-negative Staphylococci occurred in human samples. Methicillin- and vancomycin-resistant coagulase-negative Staphylococci could be detected in 41.7% & 20.8%, 68% & 31.9%, and 81.3% & 55.2% of isolates obtained from dairy food, food handlers, and patients’ samples, respectively. Whereas 81% & 64.3%, and 75.4% & 38.6% of coagulase-positive S. aureus obtained from food handlers and patients’ samples exhibited resistance to methicillin and vancomycin, respectively. Phenotypic resistance was confirmed molecularly through detection of mecA and vanA genes.Conclusion:A significant role can be played by food and food handlers in the transmission of methicillin- and vancomycin-resistant Staphylococci to patients, which has been proved in this study through the close phylogenetic relation between S. epidermidis isolated from food, food handlers, and patients’ diarrheal samples.

Molecular Study of Vancomycin Resistance in Hospital Acquired Staphylococcus Infection

Purpose: Vancomycin is treatment of choice in MRSA infection. In the last years there is increasing incidence of vancomycin resistance either vancomycin intermediate S. aureus (VISA) or vancomycin-resistant staphylococci (VRSA). This increasing in resistance strains is challenging problem especially in hospital acquired infection. The present study was carried out to find the incidence of(VISA)and(VRSA) among MRSA in children hospital in Egypt with correlation of molecular study for mec A gene and Vancomycin resistance gene Van A, Van B and Van C genes by multiplex PCR. Method: Out of 678 hospital acquired infection (365) staphylococcal isolates was obtained in which coagulase negative were (152) (41.6%) and positive (213) (58.4%) were isolated from various samples which confirmed to be hospital acquired infection according to CDC guidelines. All Staphylococcal aureus isolates and coagulase negative (CoNS) were suspected to antibiotic disc diffusion. MRSA strain were subjected to MIC for vancomycine and molecular study for detection mec A and Van A, Van B and Van C genes by multiplex PCR Results: MRSA was reported in (103) staphylococcal and (10) CONS mec gene was present in all MRSA stain. Vancomycine resistance gene was not found in any of CoNS. While in staphylococcal aureus vanA was present in 2 VRSA and 4 VISA isolates and van B was present in 6 VISA and in one VRSA isolates vanC gene was not found either in Staphylococcus aureus nor CoNS. Conclusion: The results of the current study illustrate the emergence of vancomycin resistance among methicillin-resistant S. aureus isolated from children with healthcare-associated infections. The majority revealed the occurrence of vanA and vanB as an accountable mechanism for this resistance.

Frequency and comparison among antibiotic resistant Staphylococcus aureus strains in selected hospitals of Peshawar, Pakistan.

To assess and compare the frequency of antibiotic-resistant staphylococcus aureus strains. A retrospective study was conducted at the privately-owned Welfare Medical Laboratory, Peshawar, Pakistan, and comprised record related to the period between 07th February 2017 and 23rd March 2018 of patients referred for pus-testing from Khyber Teaching Hospital, Lady Reading Hospital and the Hayatabad Medical Complex. Pus samples were obtained from various parts of body with cotton swabs. The samples were cultured and the isolated staphylococcus aureus strains were analysed against selected antibiotics. The frequency of the isolated strains was tested and compared using Prism 7 software. Of the 6780 samples, staphylococcus aureus was found in 4315(63.64%). Wild-type staphylococcus aureus strains were 2133(31.46%), followed by 825(12.16%) methicillin resistant, 792(11.68%) vancomycin intermediate, and 565(8.33%) vancomycin-resistant staphylococcus aureus strains. The isolated strains were significant (p<0.0001) for operated wounds, and non-significant (p=0.8915) for diabetic foot cases. The frequency of antibiotic-resistant staphylococcu saureus strains was high.

Prevalence and Antimicrobial Susceptibility of Vancomycin Resistant Staphylococci in an Egyptian University Hospital

Staphylococci can cause many nosocomial and community acquired infections with high rates of morbidity and mortality. The large scale of spread of resistance to vancomycin and other antibiotics has been perceived as a fearsome threat to the already challenging therapy of Staphylococci. A total of 982 clinical samples were obtained from different departments of Tanta university hospital. Microscopical examination and standard biochemical tests revealed that 437 isolates were Staphylococci. Resistance to vancomycin was determined using disk diffusion and agar dilution methods which revealed that 89 were vancomycin resistant Staphylococci (VRS). The susceptibility of VRS isolates to 15 different antimicrobial agents was performed using agar dilution method. All VRS isolates were multidrug resistant (MDR). Polymerase chain reaction (PCR) studies were performed on selected Staphylococci isolates with different vancomycin MICs ranging from 2 to 512 μg/ml for detection of vancomycin resistance genes (van genes). The vanA gene was detected in VRS isolates only with vancomycin MICs from 32 to 512 μg/ml. Neither vanB nor vanC gene was detected. β-Lactamase production by VRS isolates was investigated. A total of 88.7% of isolates produced β-lactamase enzyme. Disk approximation test was performed on all VRS isolates that were resistant to erythromycin and sensitive to clindamycin. Out of the 29 isolates on which the test was performed, 24 (82.8%) tested positive. Ciprofloxacin resistant VRS isolates were selected to study the presence of efflux mechanism of resistance. All the tested isolates were efflux positive. The VRS isolates in hospitals as well as in community are alarming to the clinicians and multi drug resistance in these isolates is very dangerous. In this study we tried to investigate the prevalence of VRS isolates in Tanta and to determine their antibiotic susceptibility.

Molecular Study of Methicillin Resistant Staphylococcus aureus Isolated from Different Hospitals in Najaf-Iraq

1 Professor of microbiology, College of Medicine, Kufa University 2 Lecturer in Molecular Biology, College of medicine, Kufa University 3 MSc, Student, Department of Microbiology, College of Medicine, Kufa University Email: hkrooz7@yahoo.com Abstract Aim of Study: The aim is to do molecular characterization of Staphylococcus aureus isolated from hospital staff and environment, in order to determine the gene(s) that is (are) responsible for antibiotics resistance especially mecA and SCCmec. Methodology: This study that aimed to detect methicillin resistant Staphylococcus aureus in isolates from AlSader Teaching Hospital and al-Hakeem General Hospital in Annajaf during the period from November 2015 to April 2016. From a total of 250 clinical samples that were collected to isolate Staphylococcus aureus from the hospital staff (nurses, doctors, workers, medical student ---etc.), and also from different parts of hospital environments. A total of 50 Staphylococcus aureus isolate were detected and confirmed by different morphological and biochemical confirmatory test. Results: These 50 isolates then studied by VITEC2 and also by cefoxitin disc susceptibility test .It was able to detect only 41 isolates that had cefoxitin resistance which represented 82% of the total Staphylococcus isolates which are regarded as Methicillin Resistant Staphylococcus aureus phenotypically. Polymerase chain reaction test was done to find out the genes that are responsible for methicillin resistance in these isolates, using three types of primers one was for Sa442 gene which was designed to confirm that the isolates were Staphylococcus aureus and two other genes to confirm that the isolates were methicillin resistant which were mecA and SCCmec with the different subtypes of the last gene, and it was found that from the 41 isolates which were phenotypically confirimed to be methicillin resistant only 32 were found to harbor these genes which represented only 78% of the phenotypically confirmed MRSA; It was found also that the subtype SCCmec type IV was the most dominant gene among SCCmec types in these isolates as it was detected in 23 out of 32 isolates (71.9%), followed by SCCmec type III Which was found in 5(15.6%) of the isolates. Conclusions: Polymerase chain reaction is the golden slandered for identification of methicillin resistant Staphylococcus aureus MRSA. The SCC mec type IV was the most dominant among SCCmec genotypes of MRSA strains that were isolated from hospitals in the present study. Recommandation: Vancomycin resistant staphylococcus aureas (VRSA) should be taken in consideration when we are working with hospital cross infection. Further studies on large scale should be performed in order to study MRSA in the whole country. Antibiotic prescribing policy should be put under observation and guidenece inside and outside hospitals.

Effects of Halide Ions on the Carbamidocyclophane Biosynthesis in Nostoc sp. CAVN2.

In this study, the influence of halide ions on [7.7]paracyclophane biosynthesis in the cyanobacterium Nostoc sp. CAVN2 was investigated. In contrast to KI and KF, supplementation of the culture medium with KCl or KBr resulted not only in an increase of growth but also in an up-regulation of carbamidocyclophane production. LC-MS analysis indicated the presence of chlorinated, brominated, but also non-halogenated derivatives. In addition to 22 known cylindrocyclophanes and carbamidocyclophanes, 27 putative congeners have been detected. Nine compounds, carbamidocyclophanes M−U, were isolated, and their structural elucidation by 1D and 2D NMR experiments in combination with HRMS and ECD analysis revealed that they are brominated analogues of chlorinated carbamidocyclophanes. Quantification of the carbamidocyclophanes showed that chloride is the preferably utilized halide, but incorporation is reduced in the presence of bromide. Evaluation of the antibacterial activity of 30 [7.7]paracyclophanes and related derivatives against selected pathogenic Gram-positive and Gram-negative bacteria exhibited remarkable effects especially against methicillin- and vancomycin-resistant staphylococci and Mycobacterium tuberculosis. For deeper insights into the mechanisms of biosynthesis, the carbamidocyclophane biosynthetic gene cluster in Nostoc sp. CAVN2 was studied. The gene putatively coding for the carbamoyltransferase has been identified. Based on bioinformatic analyses, a possible biosynthetic assembly is discussed.

Colonization and infection of methicillin-resistant staphylococcus aureus in neonatal intensive care unit

With the development and wide application of antibiotics, the number of resistant strains keeps growing and there is a trend towards a higher isolation rate of methicillin-resistant staphylococcus aureus(MRSA)year by year, accompanied by the increasing drug resistance.As reported in recent years, vancomycin resistant or intermediate staphylococcus aureus was isolated from different geographical regions.The prevalence of MRSA infection has become a serious public health problem, which is also the global focus in the medical field.This review focuses on the prevalence of MRSA colonization and infection, drug resistance mechanism, mode of transmission, prevention and efficacy in neonatal intensive care unit. Key words: Neonatal intensive care unit; Methicillin-resistant staphylococcus aureus; Colonization; Infection

Lipophilic vancomycin aglycon dimer with high activity against vancomycin-resistant bacteria.

Antibiotic-resistant superbugs such as vancomycin-resistant Enterococci (VRE) and Staphylococci have become a major global health hazard. To address this issue, we synthesized vancomycin aglycon dimers to systematically probe the impact of a linker on biological activity. A dimer having a pendant lipophilic moiety in the linker showed ∼300-fold more activity than vancomycin against VRE. The high activity of the compound is attributed to its enhanced binding affinity to target peptides which resulted in improved peptidoglycan (cell wall) biosynthesis inhibition. Therefore, our studies suggest that these compounds, prepared by using facile synthetic methodology, can be used to combat vancomycin-resistant bacterial infections.

Structural Variations of the Cell Wall Precursor Lipid II and Their Influence on Binding and Activity of the Lipoglycopeptide Antibiotic Oritavancin

Oritavancin is a semisynthetic derivative of the glycopeptide antibiotic chloroeremomycin with activity against Gram-positive pathogens, including vancomycin-resistant staphylococci and enterococci. Compared to vancomycin, oritavancin is characterized by the presence of two additional residues, a hydrophobic 4'-chlorobiphenyl methyl moiety and a 4-epi-vancosamine substituent, which is also present in chloroeremomycin. Here, we show that oritavancin and its des-N-methylleucyl variant (des-oritavancin) effectively inhibit lipid I- and lipid II-consuming peptidoglycan biosynthesis reactions in vitro. In contrast to that for vancomycin, the binding affinity of oritavancin to the cell wall precursor lipid II appears to involve, in addition to the D-Ala-D-Ala terminus, other species-specific binding sites of the lipid II molecule, i.e., the crossbridge and D-isoglutamine in position 2 of the lipid II stem peptide, both characteristic for a number of Gram-positive pathogens, including staphylococci and enterococci. Using purified lipid II and modified lipid II variants, we studied the impact of these modifications on the binding of oritavancin and compared it to those of vancomycin, chloroeremomycin, and des-oritavancin. Analysis of the binding parameters revealed that additional intramolecular interactions of oritavancin with the peptidoglycan precursor appear to compensate for the loss of a crucial hydrogen bond in vancomycin-resistant strains, resulting in enhanced binding affinity. Augmenting previous findings, we show that amidation of the lipid II stem peptide predominantly accounts for the increased binding of oritavancin to the modified intermediates ending in D-Ala-D-Lac. Corroborating our conclusions, we further provide biochemical evidence for the phenomenon of the antagonistic effects of mecA and vanA resistance determinants in Staphylococcus aureus, thus partially explaining the low frequency of methicillin-resistant S. aureus (MRSA) acquiring high-level vancomycin resistance.

Staphylococcal Colonisation of Intravenous Cannula and Antimicrobial Patterns of Isolated Staphylococcus Species

Cannula-related infections are amongst the most important nosocomial infections. Staphylococcus aureus and coagulase negative Staphylococci (CONS) are the most frequent causes of colonizing the intravenous cannula through which infection may occur. The aim of the study was to isolate the colonized staphylococci and to study the antimicrobial sensitivity pattern against them. Cultures of cannula tips were raised by semi-quantitative method. Antibiotic susceptibility test was performed by Kirby Bauer disc diffusion method as per The Clinical and Laboratory Standard Institute (CLSI) guidelines. Coagulase positive Staphylococcus was confirmed by coagulase slide test followed by tube test. CONS were distinguished by novobiocin sensitivity test. Out of 200 samples of cannula tips collected and processed, 45 (22.5%) isolates were S. aureus, 15 (7.5%) were S. epidermidis and 16 (8%) were other CONS. The highest occurance (30.7%) of S. aureus and the CONS (18.4%) was found in the nephrology ward and the surgical ward respectively. All the 76 isolates were tested for antimicrobial susceptibility pattern. Novobiocin was used to differentiate S. epidermidis from other CONS. All isolates were sensitive to ampicillin and ofloxacin. Out of total, 46.7% isolates of S. aureus and 12.9% isolates of CONS were multidrug resistant; 35.5% and 20 % isolates of S. aureus were oxacillin (methicillin) resistant and vancomycin resistant respectively. Four (12.9%) isolates of CONS [2(13.3%) of other CONS and 2(12.5%) of S. epidermidis] were oxacillin (methicillin) and vancomycin resistant. In our study, vancomycin resistant staphylococci were found and it was concluded that the precautions for inserting intravenous cannula is necessary as different kinds of pathogens may colonize such devices. DOI: http://dx.doi.org/10.3126/njst.v14i2.10426 Nepal Journal of Science and Technology Vol. 14, No. 2 (2013) 131-136