Coagulase-negative Staphylocci Research Articles

STUDY OF SPECIES IDENTIFICATION AND ANTIMICROBIAL SUSCEPTIBILITY OF VARIOUS CLINICAL ISOLATES OF COAGULASE – NEGATIVE STAPHYLOCOCCI

BACKGROUND- Interest in CoNS is increasing because of their role as pathogens in certain clinical conditions and their marked resistance to antibiotics. Frequent isolation of CoNS from the blood, other normally sterile body fluids, intravenous catheters and various tissues presents a recurrent interpretative challenge to both the clinician and microbiologist. The ubiquity of these organisms does present problems when one is faced with making a decision as to whether their isolation in clinical laboratory represents true infection or merely contaminant .AIM-The aim of this study was to isolate, identify and speciate coagulase negative staphylocci (CoNS) from clinical specimens, along with to find their resistance to antimicrobial agents with reference to their methicillin resistance .MATERIAL & METHOD - Various clinical specimens like blood, pus, wound swab, ascitic / synovial fluid, urine, cerebro spinal fluid were processed in laboratory following the standard protocol for isolation, identification and speciation of coagulase negative staphylococci. RESULT- Present study found, S. epidermidis to be most prevalent species of coagulase negative staphylocci from clinical isolates with 47.58% strains, followed by S. haemolyticus 26.06%, and S. lugdunensis 8.54%. S. saprophyticus was the most common of CoNS species from urinary tract infection cases. Methicillin resistant CoNS (MRCoNS) were detected by cefoxitin disk diffusion method Out of 234 strains of CoNS, 153 strains (65.38%) were detected as MRCoNS. Most of the MRCoNS were found to be resistant to penicillin (100%), ceftazidime (99.35%), amoxicillin-clavulanic acid (98.69%), cotrimoxazole (92.81%), gentamicin (88.23%).Susceptibility to vancomycin and pristinamycin was 86.93 % and 99.35% respectively while all the MRCoNS isolates were susceptible to linezolid. CONCLUSION - Vancomycin is the mainstay of therapy in MDR MRCoNS infections and should be used judiciously. Looking at the possibility of emergence of resistance to the drug, newer agents like linezolid and pristinamycin might provide a valuable option for the treatment of MRCoNS infections. There is a need to have the knowledge and monitoring of antibiotic sensitivity pattern and formulation of definite antibiotic policy to improve the empirical approaches to the therapy of serious infections caused by CoNS

Diagnostic value of bronchoalveolar lavage in leukemic and bone marrow transplant patients: the impact of antimicrobial therapy.

There is significant morbidity and mortality from pneumonia in leukemic and bone marrow transplant patients. We sought to explore the diagnostic yield of bronchoalveolar lavage (BAL) in these patients with new pulmonary infiltrates. A retrospective chart review of approximately 200 Non- human immunodeficiency virus (HIV) leukemic and Hematopoietic stem cell transplantation (HSCT) patients who underwent bronchoscopy at a single academic cancer center was performed. Antimicrobial use for less than 24 hours at the time of BAL was associated with a higher yield in this population (56.8% versus 32.8%, p<0.001). This supports performing bronchoscopy with BAL within 24 hours of antimicrobial therapy in leukemic and HSCT patients.

Characterization of the ability of coagulase-negative staphylococci isolated from the milk of Canadian farms to form biofilms

Mastitis is the most common and detrimental infection of the mammary gland in dairy cows and has a major economic impact on the production of milk and dairy products. Bacterial mastitis is caused by several pathogens, and the most frequently isolated bacterial species are coagulase-negative staphylocci (CNS). Although CNS are considered minor mastitis pathogens, the importance of CNS has increased over the years. However, the mechanism and factors involved in CNS intramammary infection are poorly studied and defined. Biofilms have been proposed as an important component in the persistence of CNS intramammary infection. Biofilms are defined as a cluster of bacteria enclosed in a self-produced matrix. The objectives of this study were to investigate the ability of CNS to form biofilms. A total of 255 mastitis-associated CNS isolates were investigated using a standard microtiter plate biofilm assay. The biofilms of some isolates were also observed by using confocal microscopy. The presence of biofilm-associated genes icaA, bap, aap, embP, fbe, and atlE was determined by PCR in the 255 isolates. The 5 dominant species assayed were Staphylococcus chromogenes (n=111), Staphylococcus simulans (n=53), Staphylococcus xylosus (n=25), Staphylococcus haemolyticus (n=15), and Staphylococcus epidermidis (n=13), and these represented 85% of the isolates. The data gathered were analyzed to identify significant links with the data deposited in the Canadian Bovine Mastitis Research Network database. Overall, Staph. xylosus is the species with the strongest ability to form biofilm, and Staph. epidermidis is the species with the lowest ability to form biofilm. Regardless of the species, the presence of icaA, bap, or the combination of multiple genes was associated with a greater ability to form biofilm. A strong relationship between the strength of a biofilm and days in milk was also noted, and CNS isolated later in the lactation cycle appeared to have a greater ability to form biofilm than those isolated earlier in the lactation cycle. In conclusion, Staph. xylosus is the species with the strongest biofilm formation ability. Furthermore, days in milk and gene combinations are predicted to be the variables with the strongest effect on biofilm formation by CNS.

Lead‐Associated Endocarditis: The Important Role of Methicillin‐Resistant Staphylococcus aureus

Infection is a potentially life-threatening complication of cardiac device implantation. Lead-associated endocarditis (LAE) may be the most serious complication since it is associated with a high mortality. The medical records of patients referred to our institution for the treatment of LAE between 1999 and 2007 were reviewed. A total of 51 of 107 patients referred for device-related infections met the criteria for LAE. Of these, 19 occurred within 6 months of their most recent procedure (early), while the remaining 32 occurred more than 6 months later (mean = 31.9 months post procedure). Devices included pacemakers in 33 patients and ICDs in 18 patients. The most common organism responsible for infection was Staphylococcus aureus (S. aureus) followed by coagulase-negative staphylocci (22%) and streptococci (12%). Methicillin-resistant S. aureus (MRSA) accounted for 67% of the S. aureus infections. Coagulase-negative staphylococci were responsible for only 26% of early and 19% of late cases. A distant site of infection was common (26/51 = 51%), particularly in patients with MRSA LAE. The device and leads were removed percutaneously in all patients. Only one patient failed to respond to intravenous antibiotics. Our data suggest that methicillin-resistant S. aureus is an important pathogen in LAE. Since many infections occur months after the last device procedure, hematogenous spread of organisms from a distant site may be an important contributing factor. These data suggest that strategies to prevent hematogenous infection, particularly with S. aureus, are critical in patients with implantable cardiac devices.

Bacterial, Viral and Fungal Infections in Patients after Allogeneic Stem Cell or Bone Marrow Transplantation - A Comparison between Patients with Related and Patients with HLA-Matched Non-Related Stem Cell Donors.

Bacterial, viral and fungal pathogens frequently cause severe, life-threatening infections in immunocompromised patients after allogeneic stem cell transplantation (SCT). We investigated whether patients with related stem cell donors (group A) developed infections less frequently than patients with HLA-matched, non-related donors (group B). Fifty-nine consecutive patients treated at our transplantation unit between April 2004 and January 2005 were included into the analysis. We documented demographic and clinical characteristics at baseline, treatment, clinical course, microbiological examinations, clinical and radiological signs of infection and mortality. Of the total 59 patients analyzed, 22 received stem cells from related and 37 from HLA-matched non-related donors. Both groups were well balanced regarding age and weight. 50% of the patients in group A and 60% in group B were male. Most frequent diagnoses were acute myeloid leukemia (30 of 59 patients [50.8%]; group A: 68.2%; group B: 40.5%), multiple myeloma (15.2%), acute lymphoblastic leukemia (11.9%) and chronic myeloid leukemia (10.2%). Bone marrow was more often the stem cell source in group A (45.5%/ 10 patients) than in group B (10.8%/ 4 patients), peripheral stem cell transplantation respectively was predominant in the unrelated group (86.5%/ 32 patients) versus the family donor group (54.5%/ 12 patients), cord blood was used as unrelated stem cell source in1 patient (2.7%). Clinically documented infections occurred in 6% in group A and in 14% in group B. Pulmonary infiltrates were observed more frequently in group A (11 patients/ 50%) than in group B (16 patients/ 43.2%). The predominant findings were atypical infiltrates (total 16 patients), followed by signs of fungal (total 7 patients) and bacterial pulmonary infiltration (total 4 patients). Microbiologically documented infections were detected in all patients. The average number of pathogens was equal in both groups. Detected pathogens were HHV-6 (48 patients), coagulase-negative Staphylocci (17 patients), EBV (14 patients) and CMV (11 patients). Three fungal infections were detected by microbiological approaches in group A (2 × Candida albicans, 1 × Pitysporum ovale) compared to nine fungal infections in group B (5 × Candida albicans, 1 × Candida glabrata, 1 × Candida parapsilosis, 2 × Geotrichum capitatum). Two years after transplantation, 55.9% of patients were alive (group A: 68.2%; group B: 48.6%). Patients with AML had a two-year survival of 50% (group A: 53.3%; group B: 46.7%). In our study, we observed no clear relation between frequency of infection and donor type, yet there was a trend towards more invasive fungal infections in the unrelated group (13% group A vs. 24% group B).

Late onset infection in very low birth weight infants in Malaysian Level 3 neonatal nurseries. Malaysian Very Low Birth Weight Study Group.

The purpose of this study was to examine the rate and mortality from late onset infection occurring in very low birth weight infants admitted to Malaysian nurseries. Data on all infants 1500 g or below admitted to the 20 participating Level 3 nurseries were analyzed for late onset infection (clinical infection and positive blood or cerebrospinal fluid culture occurring after 48 h of life). The overall survival of the 962 study infants was 69%. The rate of late onset infection was 19.3%. The mortality in those with late onset infection was 30.8%. The most common infecting organism was Klebsiella pneumoniae, accounting for 38.3% of infections and 46.9% of deaths in infants with infection, followed by coagulase-negative staphylocci, 17.6 and 12.2%, respectively. On logistic regression analysis risk factors for late onset gram-negative compared with gram-positive infection were endotracheal intubation at birth and blood transfusion. Hypoglycemia was associated with gram-positive infection. The late onset infection rate in Malaysian very low birth weight infants does not differ from that reported from developed countries, but the mortality is higher. This could be because of an excess of gram-negative infections.

Susceptibility of transient and commensal skin flora to the essential oil of Melaleuca alternifolia (tea tree oil)

Objectives: The purpose of this study was to determine the susceptibility of a range of transient and commensal skin flora to the essential oil of Melaleuca alternifolia, or tea tree. Methods: A modified broth microdilution method was used. Polyoxyethylene sorbitan mono-oleate detergent was added to the test medium to enhance solubility of the tea tree oil. Results: Serratia marcescens had the lowest minimum inhibitory concentration (MIC 90) of 0.25%. The highest MIC 90 was 3% for Pseudomonas aeruginosa. The lowest minimum bactericidal concentration (MBC 90) was 0.25% for S. marcescens and Klebsiella pneumoniae, whereas the highest was 8% for Staphylococcus capitis. Conclusions: S. aureus and most of the gram-negative bacteria tested were more susceptible to tea tree oil than the coagulase-negative staphylocci and micrococci. These results suggest that tea tree oil may be useful in removing transient skin flora while suppressing but maintaining resident flora.

Skin disinfection in preterm infants.

Greater care and a more thorough approach to intravenous catheter site disinfection may be important for the prevention of catheter related sepsis, especially with coagulase negative staphylocci in preterm infants. The efficacy of skin disinfection was evaluated in preterm infants using a skin swabbing technique after disinfectant exposure. In the first part of the study, 25 peripheral intravascular catheter sites were quantitatively sampled immediately after routine cannula insertion. Bacterial counts greater than 100 colony forming units/cm2 were observed from 10 (40%) sites. In the second part, sampling for bacterial colony counts was done after skin cleansing with various durations of exposure of chlorhexidine/alcohol swabs or povidone iodine. The overall mean reduction in bacterial colony counts after skin cleansing ranged from 90-99%. Skin sterilisation was achieved in 33-92% of cases. The use of two consecutive 10 second exposures resulted in a significantly improved reduction in colony counts compared with a single 10 second wipe. A longer 30 second exposure also resulted in a greater reduction of bacterial numbers compared with a shorter duration of 5 or 10 seconds. Repopulation of disinfected sites occurred within 48 hours. This effect was delayed by occluding the cleansed site with a semipermeable dressing. There were no significant differences between povidone iodine and the chlorhexidine swabs in reducing bacterial numbers. This study has demonstrated that a brief exposure with a premoistened disinfectant swab is not sufficient for complete elimination of resident skin flora of newborn infants. The use of two consecutive cleanings, or a longer duration of cleansing is recommended for more effective skin sterilisation.

Effect of Potassium Sorbate and Vacuum Packaging on the Quality and Microflora of Dry‐Cured Intact and Boneless Hams

ABSTRACTIntact and boneless hams were dry‐cured and aged with and without potassium sorbate or vacuum packaging. Sorbate had no effect on yield but dry sorbate generally improved panel scores in boneless hams. Vacuum packaging eliminated further weight loss, decreased visual appraisal scores in intact hams but had little effect on sensory scores. After 3 months of aging, aerobic and staphylococci counts were as much as 7 logs lower in nonvacuum packaged controls than in either nonvacuum or vacuum packaged sorbate treated intact hams. Counts within all vacuum packaged groups were similar. Yeast and mold counts were lower in sorbate treated than in non‐sorbate treated vacuum packaged hams. After aging, coagulasenegative staphylocci were the predominant species.

Bacteriology of rattlesnake venom and implications for therapy.

Although the incidence of infection secondary to the bites of venomous snakes remains unknown, the routine use of prophylactic antimicrobial therapy is advocated. In this study, the venom from 15 rattlesnakes was cultured, and 58 aerobic and 28 anaerobic strains of bacteria were isolated. The most common species isolated were Pseudomonas aeruginosa, Proteus species, coagulase-negative staphylocci, and Clostridium species. Bacteroides fragilis was also recovered. When the fang sheaths of four additional rattlesnakes were retracted and the fangs of these snakes decontaminated, 50% of the samples of venom had no bacterial growth (P = 0.035). Until a clinical study is performed, the use of antimicrobial therapy that reflects that complex oral flora of rattlesnakes is still recommended in most cases of envenomization.