Number Of Coagulase-negative Staphylococci Research Articles

Mutations in a Membrane Permease or hpt Lead to 6-Thioguanine Resistance in Staphylococcus aureus.

We recently discovered that 6-thioguanine (6-TG) is an antivirulence compound that is produced by a number of coagulase-negative staphylococci. In Staphylococcus aureus, it inhibits de novo purine biosynthesis and ribosomal protein expression, thus inhibiting growth and abrogating toxin production. Mechanisms by which S. aureus may develop resistance to this compound are currently unknown. Here, we show that 6-TG-resistant S. aureus mutants emerge spontaneously when the bacteria are subjected to high concentrations of 6-TG in vitro. Whole-genome sequencing of these mutants revealed frameshift and missense mutations in a xanthine-uracil permease family protein (stgP [six thioguanine permease]) and single nucleotide polymorphisms in hypoxanthine phosphoribosyltransferase (hpt). These mutations engender S. aureus the ability to resist both the growth inhibitory and toxin downregulation effects of 6-TG. While prophylactic administration of 6-TG ameliorates necrotic lesions in subcutaneous infection of mice with methicillin-resistant S. aureus (MRSA) strain USA300 LAC, the drug did not reduce lesion size formed by the 6-TG-resistant strains. These findings identify mechanisms of 6-TG resistance, and this information can be leveraged to inform strategies to slow the evolution of resistance.

Biochemical Characterization and Antibiotic Susceptibility of Coagulase Negative Staphylococci Isolates from Exudates and Body Fluids

Coagulase negative Staphylococci (CoNS) are increasingly being recognized as significant nosocomial pathogens, partly due to the growing appreciation of this group of organisms as opportunistic pathogens or due to increase in the use of transient or permanent medical devices in seriously ill and immunocompromised patients. Aims & Objectives : 1. Isolation of CoNS from exudates and body fluids. 2. Biochemical characterization of CoNS 3. Antibiotic susceptibility pattern of CoNS. Method: 180 CoNS isolated from various exudates and body fluids such as Pus, Wound Swabs, Endotrachial Secretions, Sputum, Branchial Aspitate, Central Lining Tube were collected. All the CoNS isolates were processed in the Microbiology laboratory and identified by colony morphology, Gram staining, Catalase, slide, tube coagulase test, anaerobic acid from mannitol, Deoxyribonuclease.Bacitracin (0.04 U) and furazolidone (100 µg) susceptibilities were done to exclude Micrococcus and Stomatococcus spp. The following biochemical tests were done for the speciation of the CoNS: Urease test, Phosphatase test, Polymyxin B disc test, Novobiocin Disk Test, Ornithine decorboxylase test, Mannitol to acid, voges - proskauer test , Mannose fermentation, Trehalose fermentationand Antibiotic susceptibility testing. Result: Out of 180 isolates, 78 are S.epidermidis ( 43.3%), 63 are S.hemolyticus (35%), 21 are S.hominis (11.6%), 18 are S.lugdunensis (10.0%). Maximum number of CoNS were isolated from pus specimens (58.33%), followed by wound swabs (18.33%). 164 out of 180 strains were negative for both bound and free coagulase. 60 strains were bound coagulase slow positive and free coagulase negative. S. epidermidis was the most frequent isolate and 68 S. epidermidis isolates were identified if Ornithine decorboxylase was considered positive, while negative ten S. epidermidis isolates required inclusion of trehalose and mannitol for speciation. Antibiotic susceptibility testing showed maximum resistance to penicillin (78.3) followed by Chloramphenicol (41.6%). No resistance to vancomycin was seen. Conclusion: The study revealed S. epidermidis is the predominant CoNS from Endotracheal secretions and also pus samples. S.hemolyticus was isolated from pus and central lining tubes, S.hominis and S.lugdunensis were isolated mainly from wound swabs. The present study suggests; if Coagulase -ve Staphylococci are repeatedly isolated from patients with infection they should be taken seriously and ABST done on these isolates for proper diagnosis and treatment especially in nosocomial infections. Keywords: Coagulase negative staphylococci, Antibiotic susceptibility, Clinical isolates of Exudates and body fluids, Biochemical Chemical characterization

Corneal Inflammatory Events with Daily Silicone Hydrogel Lens Wear

This study aimed to determine the probability and risk factors for developing a corneal inflammatory event (CIE) during daily wear of lotrafilcon A silicone hydrogel contact lenses. Eligible participants (n = 218) were fit with lotrafilcon A lenses for daily wear and followed up for 12 months. Participants were randomized to either a polyhexamethylene biguanide-preserved multipurpose solution or a one-step peroxide disinfection system. The main exposures of interest were bacterial contamination of lenses, cases, lid margins, and ocular surface. Kaplan-Meier (KM) plots were used to estimate the cumulative unadjusted probability of remaining free from a CIE, and multivariate Cox proportional hazards regression was used to model the hazard of experiencing a CIE. The KM unadjusted cumulative probability of remaining free from a CIE for both lens care groups combined was 92.3% (95% confidence interval [CI], 88.1 to 96.5%). There was one participant with microbial keratitis, five participants with asymptomatic infiltrates, and seven participants with contact lens peripheral ulcers, providing KM survival estimates of 92.8% (95% CI, 88.6 to 96.9%) and 98.1% (95% CI, 95.8 to 100.0%) for remaining free from noninfectious and symptomatic CIEs, respectively. The presence of substantial (>100 colony-forming units) coagulase-negative staphylococci bioburden on lid margins was associated with about a five-fold increased risk for the development of a CIE (p = 0.04). The probability of experiencing a CIE during daily wear of lotrafilcon A contact lenses is low, and symptomatic CIEs are rare. Patient factors, such as high levels of bacterial bioburden on lid margins, contribute to the development of noninfectious CIEs during daily wear of silicone hydrogel lenses.

Antimicrobial activity of marine sponges against coagulase-negative staphylococci isolated from bovine mastitis

Bovine mastitis remains worldwide a major challenge for the dairy industry despite the widespread implementation of control strategies. The increasing number of coagulase-negative staphylococci (CNS) causing mastitis and of bacteria resistant to conventional antibiotics has become a serious problem in recent years. Marine sponges are a rich source of bioactive compounds, and many species can be useful for the development of new antimicrobial drugs. In the present study, 49 CNS strains were isolated from bovine mastitis cases from 21 different dairy herds kept at farms in Southeast Brazil. Strains were analyzed for antimicrobial susceptibility and mecA gene detection. Fifty-nine percent of the CNS strains were resistant to at least one of the drugs tested and 12.2% were classified as multiresistant. Three strains carried the mecA gene, confering resistance to the beta-lactamic antibiotics. In addition, the CNS strains were submitted to in vitro screening for antimicrobial activities of extracts from marine sponges. Extracts from the sponge species Cinachyrella sp., Haliclona sp. and Petromica citrina showed antibacterial activity against 61% of the CNS strains, including strains resistant to conventional antibiotics. Extracts from P. citrina showed the largest spectrum of inhibitory activity. The aqueous extract inhibited 51% of the CNS strains and presented a bactericidal effect over susceptible and multiresistant-bacteria at a minimal inhibitory concentration of 1.024μg/ml. This study shows the potential of marine sponges as new sources of antibiotics and disinfectants for the control of CNS involved in bovine mastitis.

Reservoirs of coagulase negative staphylococci in preterm infants.

This investigation was undertaken to determine the magnitude of, and interrelations between, reservoirs of coagulase negative staphylococci on infants' skin at various sites (including sites used for insertion of intravascular catheters) and in faeces during the first six months of life. Sites with large numbers of coagulase negative staphylococci were identified by sampling 16 skin sites and stools from 20 preterm neonates at 8-30 days of life. A more detailed survey of numbers and types of coagulase negative staphylococci in stool and at six skin sites of 10 preterm infants was then performed over the first six months of life. Isolates of coagulase negative staphylococci were collected and characterised by speciation, antibiotic susceptibility profiling, and plasmid restriction fragment length polymorphism analysis. Large, relatively stable reservoirs were identified in the faeces, around the ear, and in the axilla and nares. Skin on the forearm and leg, sites at which peripheral catheters are frequently sited, carried small unstable numbers of coagulase negative staphylococci, which were usually indistinguishable from coagulase negative staphylococci isolated from other body sites on the same baby. Contamination of catheter insertion sites with coagulase negative staphylococci from reservoir sites on the same baby could explain these observations. These data suggest that interventions reducing cross-contamination between sites on the same baby might be as important in preventing coagulase negative staphylococcal bacteraemias as measures taken to prevent cross infection between babies. Procedures which are likely to result in heavy coagulase negative staphylococcal contamination of the hands of healthcare staff, such as changing soiled nappies, should receive particular attention.

Host response to coagulase-negative staphylococci in abscesses induced within mice

A model whereby a known number of coagulase-negative staphylococci were packed into capillary tubes and implanted into the peritoneal cavity of mice proved to be a satisfactory method for generating abscesses that could be easily removed free of extraneous host tissue, and that permitted measurement of the survival of the organisms and accumulation of lipid in the lesion. Strains of S. epidermidis, S. schleiferi and S. lugdunensis, differing in their ability to produce fatty acid modifying enzyme (FAME) and lipase, were packed into either glass or plastic capillary tubes and used to generate abscesses. Abscesses produced by S. aureus served as comparators. Lipids accumulated within the abscesses caused by S. aureus in the same manner as previously described for the organism inoculated without tubes. Lipids also accumulated within abscesses produced by all the coagulase-negative staphylococci, but the rate of accumulation was slower and the lipid droplets were smaller than seen with S. aureus. The mobilisation of lipid did not differ in response to cocci in plastic or glass tubes. Strains of S. epidermidis and S. schleiferi producing FAME and lipase were better able to survive within abscesses than strains unable to produce these enzymes. However, FAME and lipase production did not appear to be the sole determinants of survival within abscesses. Regardless of whether they produced FAME and lipase, the two S. epidermidis strains were significantly better able to survive within plastic tubes than in glass tubes. No such difference was seen with S. aureus between plastic and glass tubes.

Role of Coagulase-negative Staphylococci in Chronic Blepharitis

The eyelid margins of 100 normal volunteers and 116 patients with chronic blepharitis were cultured by a semiquantitative technique using soluble alginate swabs. This allowed calculation of numbers of coagulase-negative staphylococci (CNS) present, which were biotyped by a simplified version of Baird-Parker's scheme. In order to test for delayed-type hypersensitivity (DTH) to CNS, indicating cell-mediated immunity, our 116 patients each received an intradermal injection of 0.1 ml of heat-killed whole cells. No significant difference was found between normal volunteers and patients for their quantitative counts of CNS present on the lid margin. There was also a similar distribution of bio types within the CNS isolated for both groups. Our overall data, including previous studies for toxin production, do not support a pathogenic role for CNS in most patients with chronic blepharitis. In addition, we were unable to induce a DTH response to CNS in these patients. Keywords: Blepharitis; Staphylococcus; Biotype; Pathogenicity.