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Whole genome sequencing of meticillin-resistant Staphylococcus aureus.

BACKGROUND: Staphylococcus aureus is one of the major causes of community-acquired and hospital-acquired infections. It produces numerous toxins including superantigens that cause unique disease entities such as toxic-shock syndrome and staphylococcal scarlet fever, and has acquired resistance to practically all antibiotics. Whole genome analysis is a necessary step towards future development of countermeasures against this organism. METHODS: Whole genome sequences of two related S aureus strains (N315 and Mu50) were determined by shot-gun random sequencing. N315 is a meticillin-resistant S aureus (MRSA) strain isolated in 1982, and Mu50 is an MRSA strain with vancomycin resistance isolated in 1997. The open reading frames were identified by use of GAMBLER and GLIMMER programs, and annotation of each was done with a BLAST homology search, motif analysis, and protein localisation prediction. FINDINGS: The Staphylococcus genome was composed of a complex mixture of genes, many of which seem to have been acquired by lateral gene transfer. Most of the antibiotic resistance genes were carried either by plasmids or by mobile genetic elements including a unique resistance island. Three classes of new pathogenicity islands were identified in the genome: a toxic-shock-syndrome toxin island family, exotoxin islands, and enterotoxin islands. In the latter two pathogenicity islands, clusters of exotoxin and enterotoxin genes were found closely linked with other gene clusters encoding putative pathogenic factors. The analysis also identified 70 candidates for new virulence factors. INTERPRETATION: The remarkable ability of S aureus to acquire useful genes from various organisms was revealed through the observation of genome complexity and evidence of lateral gene transfer. Repeated duplication of genes encoding superantigens explains why S aureus is capable of infecting humans of diverse genetic backgrounds, eliciting severe immune reactions. Investigation of many newly identified gene products, including the 70 putative virulence factors, will greatly improve our understanding of the biology of staphylococci and the processes of infectious diseases caused by S aureus.

Animals↗

Epidemic infection by a gentamicin-resistant Staphylococcus aureus in three hospitals.

A Staphylococcus aureus strain, resistant to aminoglycosides, including gentamicin and tobramycin, and to penicillin, lincomycin, and other antibiotics, caused an outbreak of hospital infection in a surgical ward which spread to the intensive-therapy unit and to two other hospitals. 21 patients were colonised and 9 of these had overt clinical infection. Administration of antibiotics to which the staphylococcus was resistant was associated with colonisation. The use of gentamicin, tobramycin, and lincomycin in these hospitals has increased as has the occurrence of bacterial resistance to these agents. An antibiotic policy to control their use is essential to preserve their value in life-threatening infections by bacteria resistant to other agents.

Acetyltransferases↗

Development of specific PCR primers for a rapid and accurate identification of Staphylococcus xylosus, a species used in food fermentation.

Twenty-seven Staphylococcus strains isolated from food and food environments were assigned to Staphylococcus xylosus by API-Staph system. But only seven isolates had similar patterns to this species when compared to the pulse-field gel electrophoresis patterns of 12 S. xylosus strains. To perform a rapid identification of the S. xylosus species, a random amplified polymorphic DNA product of 539-bp shared by all of the S. xylosus strains was used to design a pair of primers. These primers were species-specific for S. xylosus when tested by PCR on 21 staphylococci species. This specific PCR assay confirms the identification of the seven isolates identified by PFGE to S. xylosus. In conclusion, we developed specific PCR primers for a rapid and accurate identification of the S. xylosus species.

DNA Primers↗

Specific binding of collagen to Staphylococcus aureus.

In this study the specific binding of soluble type I collagen to several strains of Staphylococcus aureus was investigated. Both type I procollagen and soluble, pepsin-treated, lathyritic rat skin type I collagen bound to these bacteria in a manner which could be blocked by the addition of gelatin to the binding assay. Saturation binding studies showed more than one class of binding sites for [125 I]-lathyritic rat skin collagen to be present with each bacterium of the Cowan I strain containing approximately 135 high affinity sites with an apparent KA of 2.3 X 10(7)M-1. Like Cowan I strain, American Type Culture Collection (ATCC) strain 25923 also bound type I collagen. IgG inhibited collagen binding in a dose dependent manner. This observation together with the finding that the protein A-deficient Wood strain did not bind collagen suggested that protein A might be the collagen binding site. However, failure of protein A-Sepharose to bind soluble collagen or protein A in solution to inhibit binding of collagen to Cowan I cells suggests that bacterial protein A does not mediate the binding. Addition of fibronectin to the binding assay did not affect the level of collagen binding, suggesting a) that the collagen binding site is different from the fibronectin binding site and b) that fibronectin does not mediate the binding of collagen to these cells. These results demonstrate a new example of bacterial binding to an extracellular matrix protein and suggest a possible mechanism whereby Staphylococcus aureus may adhere to mammalian tissue.

Animals↗

Frequency of pseudocoagulase production in Staphylococcus aureus.

Staphylocoagulase activity could only be separated from that of pseudocoagulase after addition of 4 inhibitors: 3 proteases inhibitors (EDTA, N-ethylmaleimid, aprotinin) and heparin. Of the 32 collection strains studied, only the strains 1503 and NCTC 10 345 (mutant of WOOD 46) exhibited pseudocoagulase activity alone. No other WOOD 46 strain had this isolated activity; on the other hand, 22% of them had simultaneous coagulase and pseudocoagulase activities. One out of 286 Staphylococcus aureus strains of human origin was found to be productive of pseudocoagulase alone, 32% of the strains having both activities. The search for staphylocoagulase coagulating activity in rabbit plasma is a valid test for the identification of Staphylococcus aureus; taxonomical implications are limited without use of a specific detection of coagulase.

Aprotinin↗

Effects of Staphylococcus epidermidis on cellular immunity to infection with Listeria monocytogenes.

With the present study, the effects of intravenous applications of Staphylococcus epidermidis (SE) on the course of experimental infections of mice with Listeria monocytogenes were evaluated. SE treatment 24 h prior to Listeria infection led to a reduced growth of Listeria organisms in both livers and spleens and to an increased resistance of infected animals against a lethal Listeria challenge. SE treatment 24 h after Listeria infection resulted in an enhanced growth of and retarded elimination of Listeria organisms from animal organs as well as in a reduction of delayed-type hypersensitivity to soluble Listeria antigen. Adoptive immunotherapy accomplished by transferring immune peritoneal exudate T-lymphocyte-enriched cells (PETLEs) to Listeria-infected recipients 24 h before SE treatment did not prevent the delay in clearance of Listeria organisms. When Listeria-infected recipients compromised in their immune response by SE treatment were infused with immune PETLEs either immediately or 24 h after the application of SE, the immunosuppression induced by SE proved to be reversible. It is concluded that, in analogy to other bacterial immunomodulators, Staphylococcus epidermidis is able to either nonspecifically activate macrophages or interfere with T-lymphocyte functions.

Animals↗

All Wales surveillance of methicillin-resistant Staphylococcus aureus (MRSA): the first year's results.

Over the last five years, hospitals in Wales have experienced difficulties with increasing numbers of isolates of methicillin-resistant Staphylococcus aureus (MRSA). Continuous total population surveillance of MRSA was introduced with the objectives of gaining an understanding of the extent and variation in time and place of its occurrence, the burden of disease and possible risk factors associated with its isolation and resistance to other antibiotics. All first isolates of MRSA from both hospital and community settings and all isolates of methicillin-sensitive Staphylococcus aureus (MSSA) associated with bacteraemia and cerebrospinal fluid (CSF) isolates detected in medical microbiology laboratories in Wales were collected via CoSurv, a set of interconnected data-base modules for communicable disease control. A data set was collected on each isolate and the patient associated with that isolate and compiled centrally at CDSC (Wales) for all-Wales analysis of the MRSA situation. Surveillance started in January 1996 and at the end of the first year, 2700 new isolates of MRSA had been reported from hospital and community settings, giving a rate of 92.43/100,000 population. The incidence of MRSA from bacteraemias and CSF was 5.20/100,000 compared with 12.70/100,000 for MSSA. MRSA from bacteraemia and CSF was significantly more commonly associated with male patients than MSSA. MRSA patients were significantly older. For all MRSA isolates, the highest reporting rate was in men aged 75+ (647.21/100,000). The highest incidence of invasive disease was also in men aged 75+ (45.69/100,000). Isolates from post-surgical patients were more likely to be involved in invasive disease (OR = 2.59), P < 0.001) than strains from other sources. The majority of isolates were resistant to at least two antibiotics in addition to methicillin, most frequently erythromycin and the fluoroquinolones. Very little resistance to fusidic acid, mupirocin or rifampicin was reported. Continuous total population surveillance has provided a minimum incidence of MRSA in Wales and has allowed a simple and intelligible picture of the problem to be determined, which has been fed back to hospitals to assist decisions on control.

Adolescent↗

An assessment of triclosan susceptibility in methicillin-resistant and methicillin-sensitive Staphylococcus aureus.

Triclosan is widely used to reduce skin colonization with staphylococci and is incorporated into methicillin-resistant Staphylococcus aureus (MRSA) eradication regimes. Using an agar dilution method, the minimum inhibitory concentration (MIC) to triclosan was determined for 186 isolates of MRSA and methicillin sensitive Staphylococcus aureus (MSSA). Fourteen isolates (7.5%) were detected with a MIC > or = 1.0 part per million (ppm). There was no significant difference between the incidence of triclosan resistance in strains of MSSA and MRSA. None of 16 strains of MRSA which exhibited low-level mupirocin resistance had MIC's > or = 1.0 ppm. Increased MIC's of staphylococci to triclosan may contribute to treatment failure when used to eradicate staphylococcal carriage. We suggest that routine susceptibility testing of staphylococci against triclosan might now be indicated.

Anti-Infective Agents, Local↗

Antibiotic and biocide resistance in methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococcus.

Concern has been growing regarding the potential of antibiotic and disinfectant co-resistance in clinically important bacteria. In this study, the susceptibilities of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) to chlorhexidine (CHX), the quaternary ammonium compounds cetylpyridinium chloride (CPC) and benzalkonium chloride (BC), triclosan, dibromopropamidine isethionate (DBPI) and triclocarban were compared. MRSA exhibited low-level resistance to CHX and the QACs, with MICs of 1.5 to 3-fold (CHX), and 2 to 4-fold (QACs) higher than MSSA. However, the MIC values for MRSA ranged between 0.025 (the MIC of MSSA) and 1 microg/mL with triclosan, and between <5 (the MIC of MSSA) and 75 microg/mL with DPBI. Nevertheless, these strains remain relatively sensitive to most of these antimicrobial agents. The bactericidal efficacy of CHX, CPC and DBPI (with the exception of one strain) correlated with their MIC value. This was not observed using triclosan; MRSA and MSSA strains were equally susceptible to its killing effect, regardless of MIC. The permeabilizing agent, ethylenediamine tetraacetic acid (EDTA) was unable to potentiate the antibacterial activities of the biocides against any of the strains tested. Attempts to select for staphylococcal strains with increased resistance to triclosan, CPC or CHX, using disc diffusion, step-wise broth, or repeated exposure/recovery technique, were only partially successful, and resistance was found to be unstable. The susceptibilities of vancomycin-resistant enterococcus (VRE) and vancomycin-sensitive enterococcus (VSE) to the biocides were also compared and found to be similar both in terms of MIC testing and time-kill studies.

Anti-Bacterial Agents↗

Staphylococcus intermedius: clinical presentation of a new human dog bite pathogen.

Staphylococcus intermedius is a Gram-positive, coagulase-positive coccus that can be distinguished from Staphylococcus aureus by routine microbiological testing. Whereas S intermedius is recognized as flora and pathogen of dogs, it has never been isolated from human infections. We hypothesized that S intermedius may cause human dog bite wound infections and that it has been previously misidentified as S aureus. Fourteen isolates from clinically infected dog bite wounds that were originally identified as S aureus were subjected to further testing; three (22%) were found to be S intermedius. The clinical and microbiological characteristics of these three S intermedius cases are described. All three patients were nonimmunocompromised persons seen within 24 hours for bites on the upper extremity. All patients developed cellulitis within one to three days. All S intermedius isolates were distinguished from S aureus by the lack of acetoin production and by the presence of beta-galactosidase activity. S intermedius was susceptible to a wide range of antibiotics; one isolate was resistant to penicillin. Two patients were treated with penicillin, one with amoxicillin-clavulanate, and all were clinically cured. These are the first three reported human infections involving S intermedius. Further study is necessary to define its clinical importance as a potential human pathogen.

Adult↗

[Staphylococcus lugdunensis infection: Report of thirteen cases].

INTRODUCTION: Staphylococcus lugdunensis is a coagulase-negative staphylococcus associated with infections such as aggressive endocarditis, repeated abscess formation and opportunist infections. MATERIALS AND METHODS: S. lugdunensis isolates recovered at our hospital during three years (1997-2000) were studied. The fibrinogen affinity factor and tube free-coagulase were analysed. The identification was made by the Crystal GPID (Becton-Dickinson) and Wider (Soria Melguizo) systems. Antibiotic sensitivity testing was performed with Wider panels. The clinical records of patients with S. lugdunensis recovered were studied. RESULTS: Thirteen S. Lugdunensis isolates were recovered from the following sources: abscess (9), surgical wound (2), blood culture (1), and urine (1). In ten cases the microorganism was obtained in pure culture; in the remaining three cases, S. lugdunensis grew in mixed culture. Two cases were excluded, as S. lugdunensis was considered not to be associated with the clinical condition. Lesions were located at: inguinal region (4), gluteal region (2), breast (2), abdominal wall (1), foot (1), unknown (1). Tent of the 13 isolates (76%) had fibrinogen affinity factor. Penicillin sensitivity was observed in 11/13 strains (84.6%). In one case, the isolate was beta-lactamase producer (7.6%); and in other case, the isolate was resistant to methicillin (7.6%). CONCLUSIONS: In this study we observed that S. lugdunensis is associated with skin and soft tisue infections, particularly abscess formation. The infection occurs most frequently in cancer patients, as observed in three cases in our series. The necessity of correctly identifying S. Lugdunensis is underscored. The recovery of coagulase-negative staphylococci should not reassure us unless a potentially pathogen species has been ruled out.

Adult↗

[Staphylococcus aureus bacteremia and a mass in the right atrium in a patient carrying a central port].

A male heroin abuser was admitted because of Candida endophthalmitis. A permanent central venous line was inserted. Three months later, he had positive catheter and blood cultures with Staphylococcus aureus. Transthoracic and transesophageal echocardiography and magnetic resonance revealed a right atrial mass. Treatment with antibiotics in addition to clinical and echocardiographic follow up was decided upon. Six weeks later, a transesophageal echocardiography showed a decrease in right atrial mass size and the patient was discharged asymptomatic without treatment. Three months later, he was well and a new transesophageal echocardiography showed a further decrease in atrial mass size with signs of fibrosis. This follow up supports the clinical suspicion of thrombus in the right atrium attributable to a central venous line and Staphylococcus aureus bacteremia.

Adult↗

Characterization of Staphylococcus aureus isolates from oral surgical outpatients compared to isolates from hospitalized and non-hospitalized individuals.

In 160 patients, 114 strains of Staphylococcus aureus were isolated from gingival mucosa, saliva, throat and nose. The patients were divided into 4 groups: one group from an oral surgery clinic for outpatients, one group from a dental clinic, one group from a general surgery clinic for inpatients and one group from a clinic for chronically ill and aged patients. The highest frequency of staphylococcal carriers was found in the outpatient groups (oral surgery and dental clinic), 55% and 45%, respectively. Antibiotic sensitivity testing revealed the majority of the strains to be penicillin resistant, but sensitive to isoxazolyl-penicillins, clindamycin and lincomycin. 50% of the strains produced penicillinase. About 90% of all strains produced lipase, nuclease and a haemolysin most active on rabbit erythrocytes. Human and sheep erythrocytes were lysed by 70% and 46% of the strains, respectively. 77% of the strains were bacteriolytic active. No strain produced lecitinase or elastase. No significant difference was found between the 4 groups in the formation of any of these factors. Phage-type I and III dominated but there was no correlation to enzyme production or patient groups. Thus the 4 patient groups were colonized with strains of Staphylococcus aureus that showed mainly the same pathogenetic factors.

Adolescent↗

Methicillin-resistant Staphylococcus aureus in burns patients--why all the fuss?

Procedures designed to limit spread of methicillin-resistant Staphylococcus aureus (MRSA) in burns units demand time and resources. To assess the significance of MRSA in burns patients we performed a retrospective review of MRSA colonization in in-patients over a 41-month period at the North Trent Sub-regional Burns Unit. Patients were compared with MRSA free controls, matched for age and percentage body surface area (BSA) burn and admitted during the same time period. Length of stay, number of operations and deaths were outcome indicators. All patients managed non-operatively were excluded, leaving 40 MRSA patients and 46 controls. There was no statistical difference between the two groups with regard to number of operations (p= 0.07), duration of admission (p = 0.12) or mortality (p = 0.09). Of the control group, 83% had wound swabs positive for methicillin-sensitive Staphylococcus aureus (MSSA). there was no statistical difference in any outcome variables between this sub-group of controls and MRSA patients. Colonization with S. aureus (both MRSA and MSSA) was associated with larger burns (p<0.05), twice as many operative procedures (p<0.05) and prolonged admissions (p<0.01). Mortality was unaltered by staphylococcal colonization (p = 0.8). Although our study lacks power, we would suggest that methicillin resistance per se is not associated with increased morbidity or mortality in burns patients.

Adult↗

[Staphylococcus aureus: new detection of intrinsic resistance using the diffusion method].

Because of an heterogeneously-expressed resistance among methicillin-resistant Staphylococcus aureus strains the conditions for antibiogram determination had rapidly to be modified so as to improve their detection. The newly recommended conditions (incubation at +30 degrees C or on hypersalted agar medium) remain widely used at the moment, although they appear to be more and more often badly adapted, particularly because of the recently-observed renewed outbreak of wild strains with a weak in vitro phenotypic expression. It is the reason why we searched for a new and more reliable phenotypic method although still accessible for any laboratory. Sixty-five strains of Staphylococcus aureus entered the study. The absence or presence of mecA gene was previously investigated by gene amplification. These strains were of various origins and had often caused difficulties for the detection of intrinsic resistance to methicillin on the antibiogram. Our results confirm the failures of the classical methods (false negative results at +30 degrees C, false negative or positive results on hypersalted agar medium incubated at +37 degrees C). They also allow to propose a new method which relies on the determination of the susceptibility to cefoxitin using the usual conditions for antibiogram determination. In our series of strains, this new method proved to widely improve both the sensitivity and the susceptibility for the detection of methicillin-resistance by diffusion on the antibiogram.

Agar↗

Infection and/or colonization by methicillin-resistant Staphylococcus epidermidis (MRSE).

We analyzed the parameters predictive of identification of methicillin-resistant Staphylococcus epidermidis (MRSE) in sample performed in hospitalized patients. One hundred six Staphylococcus epidermidis strains (60 MRSE and 46 MSSE) were collected. Three variables were independently linked to MRSE isolation in multivariate analysis: hospitalization during the month preceding the current admission; on-going antimicrobial therapy before sampling, and on-going infection at the time of sampling. MRSE isolation was associated with a poor vital prognosis. The air and surfaces sampling in the rooms of two patients with nasal MRSE carriage yielded the same strains as those carried by the patient, and could play a role in the epidemiological chain of hospital-acquired MRSE infections.

Carrier State↗

[Antibiotic resistance of Staphylococcus aureus at north Lebanon: place of the methicillin resistance and comparison of detection methods].

The aim of this study was to evaluate the susceptibility of 100 Staphylococcus aureus strains isolated from the laboratory of Microbiology of the Islami Hospital of Tripoli (Lebanon) to 19 antibiotics, and to determine the prevalence of methicillin resistant strains. 30% of strains studied were methicillin resistant, 96% were resistant to the penicillin G. Clavulanic acid restaurated the amoxicillin activity to 29%. The resistance level was 34% for amikacin, 3% for gentamycin and tobramycin, 10% for chloramphenicol, 44.33% for tetracyclin, 7% for erythromycin, 4.04% for clindamycin, 20% for trimethoprim-sulfametoxasol and 0% for vancomycin and teicoplanin. The methicillin-resistant Staphylococcus aureus possess more important resistant level in comparison with the methicillin sensitive strains. We compared the ability of latex agglutination test (Slidex(R) SARM, bioMérieux, France) to detect the production of penicillin-binding protein 2' (PBP 2') in 100 clinical isolates of S. aureus with two reference methods: the oxacillin disk diffusion test and the MIC determination by the E-test (AB BIODISK, Sweden). The two reference methods give the same results for the detection of methicillin resistant S. aureus. The Slidex test was positive for all 30 isolates determined to be methicillin resistant by the reference methods (sensitivity 100%). The latex test was negative for 42 of 70 isolates determined to be methicillin susceptible by the reference methods, and the latex test was positive for 28 isolates determined to be susceptible (specificity 60%).

Drug Resistance, Bacterial↗

Genetic and biochemical characterization of glutamyl endopeptidase of Staphylococcus warneri M.

A Staphylococcus warneri strain M, newly isolated from processed seafood (smoked Watasenia scintillans), produced an extracellular protease. The protease, designated to as m-PROM (the mature form of PROM), selectively cleaved the carbonyl side of glutamic acid residues in beta-casein. Sequence of N-terminal 27 amino acids of m-PROM, RANVILPNNDRHQINDTTLGHYAPVTF, was found to be similar to those of other glutamyl endopeptidases, V8 protease (Staphylococcus aureus strain V8) and SPase (S. aureus ATCC 12600). To determine the complete primary structure and precursor of PROM, its gene (proM) was cloned and sequenced. The gene proM was found to encode for a protein of 316 amino acids. The amino acid residues from 64 to 90 completely coincided with the N-terminal 27 amino acids of the m-PROM, suggesting that the N-terminal 63 amino acids region of p-PROM (the precursor form of PROM) might be processed posttranslationally. Moreover, the whole amino acid sequence deduced from the primary structure of proM shows significant similarity to those of other glutamyl endopeptidases, V8 protease and SPase. These results suggested that PROM belongs to the glutamyl endopeptidase class. PROM, however, differs from V8 and SPase proteases in the processing site and the C-terminal region.

Amino Acid Sequence↗