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PubMedDate not supplied

Methicillin-resistant Staphylococcus aureus eradication in a burn center.

Methicillin-Resistant Staphylococcus aureus and its detection, virulence, and significance relative to morbidity, epidemics, and cost have been widely discussed in the literature. Although some experts recommend against attempting to eradicate the organism, our health center decided that under the circumstances this course should be pursued. This article describes the outbreak of Staphylococcus aureus, the rationale for pursuing its eradication, the measures successful in doing so, and the relative costs involved.

Burn Units↗
PubMed1992

[Evaluation of susceptibility to antibiotics of Staphylococcus aureus strains resistant to methicillin].

Methicillin-resistant strains of Staphylococcus aureus (MRSA) constitute a serious diagnostic and therapeutic problem. Over 500 strains of Staphylococcus aureus were tested for susceptibility to methicillin. By application of a screening method, 13.7% of these strains were classified as methicillin-resistant. Over 95% of these strains were isolated from hospital infections. Applying criteria of belonging of these strains to methicillin-resistance classes it was found that 49.3% belonged to class II, 31.2% to class III and 19.5% to class IV. Analysis of susceptibility to antibiotics of MRSA strains demonstrated significant differences between class II and between class III and IV in resistance to imipenem, gentamycin, erythromycin and tetracycline. All tested strains were susceptible to ciprofloxacin, ofloxacin, vancomycin and teicoplanin. The screening method (25 mg methicillin/l of TSA medium) results in obtaining of univocal results of determination of methicillin-resistance in S. aureus.

Anti-Bacterial Agents↗
PubMed1996

[Carriage of Staphylococcus aureus. A severity factor of erysipelas?].

INTRODUCTION: Occasional superinfection or co-infection with Staphylococcus aureus led us to search for S. aureus carriage prospectively in patients with non-necrotizing bacterial dermophypodermitis, in particular erysipelas. PATIENTS AND METHODS: This prospective study included immunocompetent patients with bacterial dermophypodermitis without signs of toxicity or local manifestations suggesting necrotizing fasciitis. Bacteriology tests included: 1) direct immunofluorescence for streptococcus (groups A, C, G) on skin biopsies taken on day 0, 2) samples from the nasal orifices, the intergluteal fold, and potential skin portals for bacteriology culture, and 3) assay of antistreptolysine O and antistreptodornase B on day 0 and 15. RESULTS: The study group included 42 patients (23 females, 19 males, mean age 64 +/- 3.5 yr). In 39 cases (93%) bacterial dermohypodermitis was located on the lower limb with a potential skin portal in 36 cases (86%). Sample culture, direct immunofluorescence or serology findings demonstrated presence of streptococci in 33 cases (79%). Nasal, intergluteal or potential portal were identified in 19 patients (45%) including 16 with demonstrated presence of streptococci. The rate of cure after oral pristinamycin did not vary significantly between carriers (79%) an non-carriers (91%) of Staphylococcus aureus. Drainage of a localized abscess was successful in 5 of 6 patients after initial failure of antibiotic treatment; 4 of them were carriers of S. aureus. CONCLUSION: This prospective study demonstrated that cutaneous-mucosal carriage of Staphylococcus aureus is frequent in patients with non-necrotizing dermohypodermitis. This carriage is not a factor of over-morbidity as shown in this group of infections largely dominated by erysipelas.

Anti-Bacterial Agents↗
PubMed1987

The susceptibility to lysozyme of beta-lactamase-producing and non-producing derivatives of Staphylococcus aureus strain 1030.

The killing of Staphylococcus aureus strain 1030 and derived variants of it by lysozyme increased with increased lysozyme concentrations or decreased concentrations of sodium chloride. beta-Lactamase-producing and non-producing derivatives of strain 1030 were constructed. The former were less susceptible to lysozyme. Induction of beta-lactamase synthesis with 2-2'carboxyphenyl-benzoyl-6-penicillanic acid increased the resistance of producer strains to lysozyme. These results are discussed in relation to the spread of beta-lactamase-producing strains of S. aureus.

Aerobiosis↗
PubMed1977

Geometry of cell division in Staphylococcus aureus.

The process of division in Staphylococcus aureus was examined by phase-contrast microscopy. The organisms appeared to divide in three alternating perpendicular planes, with sister cells remaining attached to each other after division. The resulting point of attachment was usually not exactly at the point corresponding to the center of the previous septal disk. Moreover, sister cells often changed position with respect to one another while still remaining attached. These factors are apparently responsible for the irregularity of staphylococcal clumps. Studies with penicillin and the examination of thin sections in the electron microscope confirm the conclusion, based upon light microscopy, that successive divisions in S. aureus occur in perpendicular planes.

Cell Division↗
PubMedDate not supplied

[Typing of methicillin-resistant Staphylococcus aureus with a specific type of resistance].

Methycillin resistant Staphylococcus aureus (MRSA) is the important causative agent of intrahospital infections (IHI) which could have epidemic character. Typization of strains is necessary for control of these infections. Fifty eight strains of MRSA with specific resistance to antibacterial agents have been isolated from patients at different clinics of our hospital. The determination of resistotype, biotype and plasmid profiles of these and control strains of Staphylococcus aureus (SA) was aimed at confirmation whether identical strains were in questions. Biotypization showed no difference between the studied and control strains while determination of the plasmid profile proved the presence of an epidemic strain which caused infection in several clinics of our hospital.

Bacterial Typing Techniques↗
PubMed2002

Response of Staphylococcus aureus isolates from bovine mastitis to exogenous iron sources.

Staphylococcus aureus can survive in conditions of extremely low iron concentration. The ability of S. aureus to use two exogenous hydroxamate types of siderophores (desferrioxamine and ferrichrome) and four iron-containing proteins found in cattle (hemin, hemoglobin, ferritin, and lactoferrin) were tested on 16 reference and clinical isolates. For all strains tested, ferrichrome and desferrioxamine showed strong growth-promoting activities in a disk diffusion assay and in liquid medium. The heme proteins hemin and hemoglobin were also found to support growth in culture media lacking other iron sources, while lactoferrin failed to do so. On media containing the iron chelator dipyridyl, ferritin induced a growth inhibition effect that was further enhanced in the presence of lactoferrin in seven of the 13 tested strains. Staphylococcus aureus was able to bind hemin and the level of binding activity was not increased after growth in iron-rich or -poor media. Dot-blot competition tests showed that biotin-labeled lactoferrin binds to S. aureus, and this binding can be inhibited by unlabeled lactoferrin. Expression of lactoferrin-binding activity was independent of the level of iron in the medium and the iron saturation status of lactoferrin. For each strain tested, ligand blots showed lactoferrin-binding proteins of molecular weights ranging from 32 to 92 kDa. Possible functions of these lactoferrin-binding proteins could not be related to iron acquisition mechanism in S. aureus.

Animals↗
PubMed2006

Prevalence and antimicrobial susceptibility pattern of methicillin resistant Staphylococcus aureus isolates from Trinidad & Tobago.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) has become increasingly prevalent worldwide since it was first reported in a British hospital. The prevalence however, varies markedly in hospitals in the same country, and from one country to another. We therefore sought to document comprehensively the prevalence and antimicrobial susceptibility pattern of MRSA isolates in Trinidad and Tobago. METHODS: All Staphylococcus aureus isolates encountered in routine clinical specimens received at major hospitals in the country between 2000 and 2001 were identified morphologically and biochemically by standard laboratory procedures including latex agglutination test (Staphaurex Plus; Murex Diagnostics Ltd; Dartford, England); tube coagulase test with rabbit plasma (Becton, Dickinson & Co; Sparks, MD, USA), and DNase test using DNase agar (Oxoid Ltd; Basingstoke, Hampshire, England). MRSA screening was performed using Mueller-Hinton agar containing 6 mug oxacillin and 4% NaCl, latex agglutination test (Denka Seiken Co. Ltd, Tokyo, Japan) and E-test system (AB Biodisk, Solna, Sweden). Susceptibility to antimicrobial agents was determined by the modified Kirby Bauer disc diffusion method while methicillin MICs were determined with E-test system. RESULTS: Of 1,912 S. aureus isolates received, 12.8% were methicillin (oxacillin) resistant. Majority of the isolates were recovered from wound swabs (86.9%) and the least in urine (0.4%) specimens. Highest number of isolates was encountered in the surgical (62.3%) and the least from obstetrics and gynaecology (1.6%) facilities respectively. Large proportions of methicillin sensitive isolates are >85% sensitive to commonly used and available antimicrobials in the country. All MRSA isolates were resistant to ceftriaxone, erythromycin, gentamicin and penicillin but were 100% sensitive to vancomycin, rifampin and chloramphenicol. CONCLUSION: There is a progressive increase in MRSA prevalence in the country but the present rate is still low in comparison to values in some other countries. Vancomycin is still the drug of choice for treating multidrug resistant MRSA infections. Further use of molecular studies to monitor the epidemiology of MRSA in these hospitals in the country is highly recommended too.

Humans↗
PubMed2003

Management of catheter-related Staphylococcus aureus bacteremia: when may sonographic study be unnecessary?

This study reviews the outcome of patients with uncomplicated catheter-related Staphylococcus aureus bacteremia diagnosed in our hospital from January 1997 to December 1999 and treated with short-course antibiotic therapy. Our aim was to assess the effectiveness of this regimen for minimizing complications (relapses, endocarditis and metastatic foci). A total of 213 episodes of bacteremia were registered and 167 (78.4%) were nosocomial. Among these, 87 (52.1%) were catheter-related Staphylococcus aureus bacteremia and 20 were primary nosocomial bacteremia. Endocarditis was diagnosed during the acute episode in 7/107 of these patients (2 by persistent fever after catheter removal and 5 by metastatic foci; 3 of them also had cardiac risk factors) and confirmed with transesophageal echocardiography. Among the 84/87 catheter-related Staphylococcus aureus bacteremia and 16/20 primary nosocomial bacteremia patients who did not develop endocarditis, 31 patients died during the acute episode (16 due to sepsis despite initiation of antibiotic treatment and 15 due to the underlying disease) and five had osteoarticular foci. The remaining 64 episodes were considered to be uncomplicated bacteremia (no cardiac risk factors, persistent fever, metastatic foci, or clinical signs of endocarditis) and were treated with 10-14 days of high-dose antistaphylococcal antibiotics. Echocardiography was not mandatory in these patients. Of the 64 uncomplicated episodes, 62 were followed for at least 3 months and none relapsed or developed endocarditis. Even though some of the patients might have had subclinical endocarditis, short-course therapy with high doses of antistaphylococcal antibiotics was effective for treating uncomplicated catheter-related Staphylococcus aureus bacteremia. Transesophageal echocardiography may not be necessary in these cases.

Anti-Bacterial Agents↗
PubMed2002

Methicillin resistance among isolates of Staphylococcus aureus: antibiotic sensitivity pattern & phage typing.

Out of 3988 clinical specimens from hospital admitted patients 230 strains of Staphylococcus aureus were isolated, 45 strains (19.56%) were Methicillin resistance Staphylococcus aureus (MRSA). All MRSA strains were beta lactamase producers. Multidrug resistance was observed among MRSA strains more commonly than in methicillin sensitive strains of Staphylococcus aureus (MSSA). Maximum strains were resistant to penicillin (100%), co-trimoxa zole (97%) & chloramphenicol (93.33%). As least resistant to gentamicin & ciprofloxacin shown by MRSA, these drugs can be used in few situations after susceptibility test. All strains of MRSA were sensitive to vancomicin (100%). Majority of strains (34 out of 45) showed MIC values of 4 ug/ml. Twenty eight out of 44 strains were non typable using routine phages. Study revealed that MRSA with associated multidrug resistance is common in this region. There is need to develop local set of MRSA phages for improvement of typability.

Bacteriophage Typing↗
PubMed1983

The protective effect of some food ingredients on Staphylococcus aureus MF31.

The upper limiting temperature of growth of Staphylococcus aureus MF31 in heart infusion broth (HI) was about 44 degrees C but addition of monosodium glutamate (MSG) and soy sauce permitted the organism to grow above this temperature. This effect is similar to that of NaCl. Tomato ketchup, Worcestershire and HP sauces added to HI did not allow growth at the non-permissive temperature of 46 degrees C but death was delayed. Staphylococcus aureus died in unsupplemented chicken meat slurry at 46 degrees C but grew at 48 degrees C in slurry supplemented with 5.8% NaCl and survived incubation for 18 h at 50 degrees C in slurry supplemented with 5.8% NaCl and 5% MSG. Cultures grown at 37 degrees C had a D60 value of 2 min in 50 mmol/l Tris (pH 7.2) buffer. Cultures grown at 46 degrees C in HI containing 5.8% NaCl had a D60 value of 8 min in Tris buffer. Addition of 5.8% NaCl plus 5% MSG to the buffer increased the D60 by a factor of about 7 for both cultures. In storage experiments at room temperature, the culture grown at 37 degrees C and at 46 degrees C plus 5.8% NaCl died at about the same rate in salami. In milk powder, however, the count of 37 degrees C culture decreased from 10% g to 10(6)/g in 5 weeks while the count of 46 degrees C culture remained unchanged. In cottage cheese, freeze-dried rice and macaroni, the 37 degrees C cultures also died more rapidly. It is suggested that cultures grown at 46 degrees C plus 5.8% NaCl may be suitable for experiments with artificially contaminated foods.

Cheese↗
PubMed2003

Methicillin-resistant/methicillin-sensitive Staphylococcus aureus bacteremia.

OBJECTIVE: To examine the differences between the clinical presentation, management and outcome of persons bacteremic with methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA), after controlling for age, sex and primary diagnosis. METHODS: A review of the clinical records and laboratory data of all MRSA and MSSA bacteremic patients. Fifty matched case-control pairs were further analyzed looking for differences between the 2 populations. The study was carried out in a 500-bed adult tertiary care institution in southwestern Ontario, Canada, between 1994 and 1999. RESULTS: On univariate analysis a) duration of hospitalization prior to bacteremia, b) concomitant polymicrobial bacteremia, c) time to appropriate treatment, were significantly greater in the MRSA infected population. Attributable mortality was also higher, 36%-20%, but this did not achieve significance (p=0.1). On multiple logistic regression analysis, a), b) and c) remained significantly different. CONCLUSION: In a 1:1 matched case-control study of Staphylococcus aureus bacteremia, those infected with MRSA became bacteremic later in their hospital stay, more often had a polymicrobial bacteremia and were appropriately treated later. Although mortality attributable to the MRSA bacteremia was greater, this difference did not achieve significance.

Bacteremia↗
PubMed1996

Borderline susceptibility to methicillin in Staphylococcus aureus: a new mechanism of resistance?

Staphylococcus aureus strains with borderline levels of susceptibility or resistance to antistaphylococcal penicillinase-resistant penicillins (PRPs) were initially reported as neither heteroresistant nor multiply resistant organisms, producing large amounts of beta-lactamase, and becoming fully susceptible to PRPs in the presence of beta-lactamase inhibitors. This borderline susceptibility or low-level resistance was suggested to be due to beta-lactamase hyperproduction: according to this hypothesis, the staphylococcal beta-lactamase, when hyperproduced, would succeed in partially hydrolyzing methicillin and related PRPs. However, later studies demonstrated that borderline PRP susceptibility cannot be explained soley on this basis, beta-lactamase hyperproduction being neither sufficient nor necessary to determine the borderline phenotype. Intrinsic mechanisms have also been reported to be associated with some borderline PRP susceptible S. aureus strains. The more recent discovery of a PRP-hydrolyzing beta-lactamase (methicillinase) produced, in addition to the conventional penicillinase, by borderline S. aureus strains suggests that this second, more specific beta-lactamase is more likely to be responsible for the borderline phenotype than an increased amount of the penicillinase. The slow kinetics of PRP hydrolysis by methicillinase is consistent with its association with reduced susceptibility rather than true resistance to PRPs. The combined effect of methicillinase plus penicillinase on some common substrates might explain the increased beta-lactamase activity often observed in borderline S. aureus strains.

Methicillin Resistance↗
PubMed1998

Necrotizing fasciitis caused by Staphylococcus aureus.

Two patients with rapidly progressive necrotizing fasciitis of a lower extremity due to Staphylococcus aureus as a single pathogen are described. In both patients the portal of entry was attributed to needle puncture (intra-articular injection and intravenous catheter, respectively), followed by bacteremia. Necrotizing fasciitis occurred in a site remote from the needle puncture, suggesting metastatic infection. One patient developed toxic shock syndrome and the other a sunburn-like rash and erythematous mucosae with strawberry tongue. One patient died, and the other required above-knee amputation due to secondary infectious complications. Staphylococcus aureus may mimic the presentation of invasive group A streptococcal infections. A history of needle puncture should alert the physician to the possibility of Staphylococcus aureus infection.

Aged↗
PubMed1985

[Problem of the in vitro sensitivity to cefamandole of methicillin-resistant Staphylococcus aureus].

In work involving 127 strains of methicillin resistant Staphylococcus aureus, belonging to two resistance categories, homogeneous or RO and heterogeneous or RH and using five cephalosporins, cefalotin, cefazolin, cefamandole, cefotaxime and latamoxef, the authors compared the results of their in vitro sensitivity measurements with two methods: agar disk diffusion and growth inhibition in liquid medium (Autobac). They also compared the MIC values with a significant fraction (19 strains). In order to detect heterogeneous resistance experiments were carried out in duplicate, with one series grown in hypertonic medium and incubated for 48 heures at 37 degrees C, or grown on normal medium with lower incubation at 30 degrees C. In both defined techniques and in vitro, it was observed that the 127 methicillin resistant Staphylococcus aureus strains except one were sensitive to cefamandole and that 26 were also sensitive to cefalotin. Considerable caution is necessary in the in vivo transposition of these findings. May be present media are not able to allow growth of resistant strains to cefamandole.

Bacteriological Techniques↗
PubMed2000

In vitro zones of inhibition of coated vascular catheters predict efficacy in preventing catheter infection with Staphylococcus aureus in vivo.

This report summarizes data from 35 rabbit model experiments investigating the relationship between in vitro anti-infective catheter coating zones of inhibition and in vivo efficacy. The rabbit model studies involving 15 anti-infective coatings demonstrate an inverse correlation between the sizes of zones of inhibition of Staphylococcus aureus and both the quantity of Staphylococcus aureus removed from the catheter and the risk of a purulent infection. The review of seven previously published clinical trials reveals that the use of anti-infective coated catheters, efficacious in the rabbit model, was associated with a higher success rate than the use of uncoated catheters in preventing both Staphylococcus aureus catheter colonization (odds ratio: 1.28; 95% confidence interval: 0.84-1.93) and Staphylococcus aureus catheter-related bloodstream infection (odds ratio: 3.07; 95% confidence interval: 0.98-9.60) in humans. These findings strongly suggest a correlation between zones of inhibition and in vivo efficacy. In vitro zones of inhibition may serve as a useful screening test for evaluating new anti-infective coatings.

Animals↗
PubMed1981

[Resistance development in human Staphylococcus aureus due to the use of oxytetracycline and tylosin in industrialized swine production units].

Staphylococcus aureus strains from human nasal carriers without vocational contact with pigs could be differentiated from the majority of strains obtained from pathologically affected pigs by determination of host-specific-variety, according to Meyer (1966) and Witte et al. (1977). Less unambiguous findings regarding site variability were recorded from strains in nasal mucosa of pig-handling personnel, clinically intact pigs on farms, and slaughtered pigs. Antibiotics, such as oxytetracycline and macrolides were applied to pigs but failed for all practical purposes to have any bearings on the development of Staphylococcus aureus resistance in human probands with no vocational contact with animals. Personnel of pig units, however, exhibited moderate resistance to oxytetracycline and macrolides of Staphylococcus aureus strains which were typical of man. Macrolide resistance was determined, in that context, by one single-resistance plasmid.

Animal Husbandry↗
PubMed2006

[Effect of human beta defensin 2 on Staphylococcus aureus infection: in vivo study with transgenic mice].

OBJECTIVE: To investigate the effect of human beta defensin 2 (HBD-2) on Staphylococcus aureus infection. METHODS: A minigene of HBD-2 containing pCMV promoter, full length of HBD-2 cDNA, and BGH polyA tail was generated by PCR amplification and introduced into the fertilized oocytes of C57/ICR hybridized mouse by microinjection. After gestation of 3 - 4 weeks, immunohistochemistry was used to detect the expression of HBD-2 peptide in different tissues of the transgenic young mice. Staphylococcus aureus was cultured and injected intraperitoneally to wild type mice and transgenic mice to observe their surviving status. RESULTS: PCR showed that the HBD-2 fragment had been successfully integrated into the chromosome of the mice. A widespread expression of HBD-2 gene was found in many tissues of the transgenic mice: trachea, lung, intestine, esophagus, testis, spleen, skin, endothelium, brain, etc. Four of the 7 transgenic mice survived the Staphylococcus aureus infection, and 10 wild type mice all died within 24 hours. CONCLUSION: HBD-2 may play an important role ion the host defense against Staphylococcus aureus infection.

Animals↗