Changing epidemiology of pediatric Staphylococcus aureus bacteremia in Denmark from 1971 through 2000.

BACKGROUND: Staphylococcus aureus is known to be a leading cause of bacteremia in childhood, and is associated with severe morbidity and increased mortality. To determine developments in incidence and mortality rates, as well as risk factors associated with outcome, we analyzed data from 1971 through 2000. METHODS: Nationwide registration of S. aureus bacteremia (SAB) among children and adolescents from birth to 20 years of age was performed. Data on age, sex, source of bacteremia, comorbidity and outcome were extracted from discharge records. Rates were population adjusted and risk factors for death were assessed by multivariate logistic regression analysis. RESULTS: During the 30-year study period, 2648 cases of SAB were reported. Incidence increased from 4.6 to 8.4 cases per 100,000 population and case-mortality rates decreased from 19.6% to 2.5% (P = 0.0001). Incidence in the infant age group (<1 year) were 10- to 17-fold greater compared with that in the other age strata and mortality rate was twice as high. Hospital-acquired infections dominated the infant group, accounting for 73.9%-91.0% versus 39.2%-50.5% in the other age groups. By multivariate analysis, pulmonary infection and endocarditis for all age groups, comorbidity for the older than 1 year, and hospital-acquired infections for the oldest group were independently associated with an increased risk of death. CONCLUSIONS: Mortality rates associated with SAB decreased significantly in the past 3 decades, possibly because of new and improved treatment modalities. However, incidence rates have increased significantly in the same period, underscoring that S. aureus remains an important invasive pathogen.

Blocking of leukocyte accumulation in the cerebrospinal fluid augments bacteremia and increases lethality in experimental pneumococcal meningitis.

The role of leukocyte accumulation in the cerebrospinal fluid (CSF) in the evolution of the pathophysiological changes that occur in bacterial meningitis is unclear. Here, we investigate how leukocyte recruitment to the CSF, modulated by the leukocyte blocker fucoidin, affects the extent of brain damage and outcome in pneumococcal meningitis in rats treated with ceftriaxone from 28 h after infection. Rats treated with fucoidin from time of infection had an excess risk of a fatal outcome compared to rats not receiving fucoidin (25/63 versus 5/34, p=0.012), whereas the risk of cortical damage in surviving animals was comparable (16/44 versus 9/29, p=0.8). Pre-treatment with fucoidin attenuated CSF pleocytosis 24 h after infection (median 400 versus 800x10(6) cells/l, p=0.01) without affecting CSF bacterial counts (2.3x10(5) versus 3.6x10(5) CFU/ml, p=0.54). A significant increase in blood bacterial counts was found among rats pre-treated with fucoidin (median 9.6x10(2) versus 5.2x10(2) CFU/ml, p=0.03). Furthermore, blood bacterial count was found to be an important predictor of fatal outcome as shown by multivariate logistical regression analysis (OR 4.43, 95% CI [1.16-17.0] p=0.03). In summary, blocking leukocyte entry to the central nervous system in experimental pneumococcal meningitis compromises the survival prognosis but does not affect the risk of brain damage or level of infection in this compartment. Conversely, poorer prognosis was associated with an increase in bacterial load in blood, suggesting that leukocyte blockage affects the host's ability to control systemic infection.

Susceptibility testing of urinary isolates of Escherichia coli to mecillinam using NCCLS methodology.

Criteria for susceptibility testing of mecillinam against 533 isolates of Escherichia coli and a further 309 Enterobacteriaceae, according to NCCLS methodology, were determined. Correlation of MIC to inhibition zones was good for all species. For urinary isolates of E. coli, the following agar dilution breakpoints and corresponding interpretive zone diameters seem appropriate: < or = 8 mg/L/> or = 15 mm for susceptible; 16 mg/L/12-14 mm for intermediate susceptible and > or = 32 mg/L/< or = 11 mm for resistant. The appearance of isolated colonies within the inhibition zone was sometimes noted with disc diffusion, particularly for non-E. coli Enterobacteriaceae. The relevance of these colonies to clinical (bacteriological) efficacy was determined and the results suggested that they could be ignored when testing urinary E. coli.

Treatment and outcome of Staphylococcus aureus bacteremia: a prospective study of 278 cases.

BACKGROUND: Staphylococcus aureus bacteremia is still a serious problem, and the optimal treatment is under debate. Only a few studies concerning treatment are available. METHODS: The study population was all patients with a positive blood culture result for S aureus in Copenhagen County, Denmark, from May 1994 through April 1996. Of 278 patients with S aureus bacteremia, 186 were evaluated according to outcome in a prospective, observational follow-up study. The time above the minimum inhibitory concentration was estimated for dicloxacillin sodium for each treatment regimen and evaluated by logistic regression along with other potential risk factors. RESULTS: The following variables were statistically associated with death: the presence of an uneradicated focus (odds ratio [OR], 6.7; 95% confidence interval [CI], 2.1-21.0); the presence of septic shock (OR, 3.7; 95% CI, 1.5-9.1); the total daily dose of penicillinase-stable penicillin less than 4 g (OR, 3.7; 95% CI, 1.3-11.1); and age 60 years or older (OR, 2.4; 95% CI, 1.1-5.3). The following variables were significantly associated with recurrence: the total daily dose of penicillinase-stable penicillin less than 3 g (OR, 3.9; 95% CI, 1.6-10.0) and the presence of a secondary focus (OR, 3.2; 95% CI, 1.3-7.7). Among 155 patients with observation time longer than duration of treatment, this factor (duration of treatment, <14 days) was significantly related to mortality (OR, 0.84; 95% CI, 0.76-0.94). CONCLUSIONS: Focus eradication and the dosing of penicillinase-stable penicillin are important to the outcome of S aureus bacteremia. We recommend treatment with at least 1 g of penicillinase-stable penicillins 4 times daily for longer than 14 days.

In vitro susceptibility of Staphylococcus aureus towards amoxycillin-clavulanic acid, penicillin-clavulanic acid, dicloxacillin and cefuroxime.

Sixty-three Staphylococcus aureus isolates with a wide distribution in quantitative beta-lactamase production were tested in vitro against amoxycillin and penicillin in combination with clavulanic acid to establish the influence of total amount of beta-lactamase present on the ability of clavulanic acid to protect against beta-lactamase degradation. The beta-lactamase stability of cefuroxime and dicloxacillin was also evaluated. MIC was determined by agar dilution using Mueller-Hinton agar with both a conventional as well as a 100 times higher inoculum. The strains were tested both with and without induction of the beta-lactamase production. Clavulanic acid was highly effective in protecting against beta-lactamase degradation of both penicillin and amoxycillin. Even when using a high inoculum of strains with induced beta-lactamase production, all strains had MICs below the NCCLS breakpoint of 4/2 mg/l for amoxycillin-clavulanic acid. Both cefuroxime and dicloxacillin were highly stable against staphylococcal beta-lactamase degradation. This study encourages further in vivo evaluation of amoxycillin-clavulanic acid for severe staphylococcal infections.

Evaluation of different disk diffusion/media combinations for detection of methicillin resistance in Staphylococcus aureus and coagulase-negative staphylococci.

In order to find a disk diffusion method with both high sensitivity and specificity for determination of methicillin resistance primarily for S. aureus but also for coagulase-negative staphylococci we screened several methodological variants using a material of 66 S. aureus comprising of 11 methicillin-susceptible, 18 borderline-resistant, and 37 methicillin-resistant strains. Only four of the combinations studied performed with both high sensitivity and specificity. Two of these, the Columbia agar +4.5% NaCl and Mueller Hinton agar +2% NaCl combined with a 5 microg oxacillin disk, confluent inoculum and 24 h incubation at 35 degrees C were further evaluated using 105 MRSA and 91 mecA-negative S. aureus and 193 clinical isolates of coagulase-negative staphylococci. The Columbia agar +4.5% NaCl performed excellently for both S. aureus and coagulase-negative staphylococci. For Columbia agar +4.5% NaCl using a 5 microg oxacillin disk we suggest an interpretive zone diameter of R < or =15 mm and S > or =16 mm for S. aureus and R < or =24 mm and S >or =26 mm for coagulase-negative staphylococci. The Mueller Hinton agar +2% NaCl performed well for coagulase-negative staphylococci but for S. aureus at least three (3%) very major errors were found, making this method less attractive.

Tentative interpretative zone diameters for fusidic acid Neosensitabs on Mueller Hinton agar and three blood containing media.

Two hundred and ninety-two staphylococci were tested using fusidic acid Neosensitabs, a semiconfluent inoculum on Mueller Hinton agar and three blood containing agar media in order to investigate the interpretative zone diameters published by the manufacturer (Rosco). Zone diameters were, as expected, smaller on blood containing agar compared with Mueller Hinton agar. Many susceptible strains were intermediate on Danish Blood agar using the current breakpoints. We suggest that the interpretative zone diameters be changed to S>or=32, Ror=24, R

[Staphylococcus aureus infections--the clinical picture and treatment]. / Infektioner med Staphylococcus aureus--klinik og behandling.

Infections caused by Staphylococcus aureus comprise relatively benign local skin infections, as well as serious generalised conditions. In Denmark, more than 85% of all S. aureus isolates are found resistant to penicillin, whereas resistance to methicillin is rare (< 1%) and therefore one of the penicillinase-stable penicillins is still the drug of choice. Dicloxacillin is usually chosen, because of its superior penicillinase stability. Infections caused by methicillin resistant strains may be treated with different combinations of macrolides, fusidic acid, aminoglycosides, fluoroquinolones, and rifampicin, but vancomycin is generally used. Newer drugs like the oxazolidinones and streptogramins are effective against methicillin-resistant strains and will be available in Denmark within a short time. Antibiotic treatment, however, is most often only a supplement to surgical intervention. This paper deals with the clinical picture and treatment of some common S. aureus infections.

Evaluation of fusidic acid in therapy of experimental Staphylococcus aureus meningitis.

OBJECTIVES: Combination therapy that includes fusidic acid, an antimicrobial agent highly active against staphylococci, has been recommended in the treatment of patients with Staphylococcus aureus meningitis. The aim of this study was to evaluate the pharmacokinetic, CSF bactericidal and anti-inflammatory properties of fusidic acid. METHODS: The pharmacokinetics, treatment efficacy and parameters of the meningeal inflammatory response were studied in rabbits, using an experimental meningitis model against S. aureus (MICs of fusidic acid and methicillin were 0.125 and 1 mg/L, respectively). RESULTS: Fusidic acid entered the CSF, with peak values within 0.5-1 h of the intravenous bolus injection/infusion and with a percentage penetration (AUCCSF/AUCserum) into uninfected and purulent CSF of 1.9% +/- 0.7 and 4.5% +/- 0.7, respectively. Rabbits treated with antibiotics [fusidic acid 80 mg/kg/6 h (n = 6), methicillin 80 mg/kg/3 h (n = 7) and the two combined (n = 6)] had significantly higher bacterial kill rates than untreated controls (n = 6, P < 0.05). Combination therapy was less effective, with significantly less killing after 6 h of treatment than methicillin alone (P < 0.05). CSF white blood cells and CSF levels of interleukin-8 (IL-8), glucose, lactate and protein were altered during staphylococcal meningitis, but with no significant difference between antibiotic-treated and untreated rabbits. CONCLUSIONS: Antagonism between methicillin and fusidic acid was observed in staphylococcal meningitis.

Validation of FLEXICULT SSI-Urinary Kit for use in the primary health care setting.

The efficacy of the FLEXICULT SSI-Urinary Kit for point-of-care diagnosis and susceptibility testing of urinary tract pathogens was evaluated. The kit, which was exclusively developed for urine culture in the primary health care setting, is designed as an ordinary Petri dish divided into 6 compartments: I large one for quantitative analysis and 5 smaller ones for susceptibility testing. The agar in each small compartment contains 1 of 5 antimicrobials (trimethoprim, sulfamethoxazole, ampicillin, nitrofurantoin and mecillinam) at a concentration adjusted to the breakpoint, and growth in these compartments indicates resistance. The kit was tested in-house with 116 urinary tract pathogens and by 19 general practitioners in a field trial with 121 diagnostic urine specimens. The kit was flooded with the urine specimens for a couple of seconds, incubated overnight and read the following day. Quantitative readings were evaluated by comparing with standardized inoculi and the susceptibility tests were compared with the MIC value of the strain for each of the 5 antimicrobials. In the field trial, the quantitation had an overall error rate of 4% and correctly determined susceptibility in 93% of the tested bacteria. Although identification of the isolates is not a feature of this kit, it is suitable for point-of-care diagnosis and for susceptibility testing of uncomplicated urinary tract infections in the primary health care setting.

Epidemiology of Staphylococcus aureus bacteremia in Denmark from 1957 to 1990.

OBJECTIVE: To investigate the changes in epidemiology of Staphylococcus aureus (SA) bacteremia in Denmark over a 30-year period, where the population has remained stable. METHODS: Bacteriologic and clinical data were generated on 17 712 SA strains from virtually all SA bacteremia cases in Denmark from 1957 to 1990 submitted to our laboratory for phage typing. The data were related to information about population, hospital activity and blood-culturing activity during that period. RESULTS: SA bacteremia cases increased from 3 to 20/100 000 inhabitants per year, with the largest increases in incidence rates for the <1-year and >50-year age groups. While blood-culturing activity increased three-fold during the period, the rate of SA bacteremias actually decreased relative to the number of blood cultures taken. The increase in SA bacteremia cases was mainly due to increases in nosocomial infections for all age groups and was related to the increasing admission rates to Danish hospitals. Major shifts in antibiotic resistance patterns and phage types took place during the period, i.e. a marked reduction in multiresistant (including methicillin-resistant) strains, but could not explain the change in the epidemiology of the infections. CONCLUSIONS: The data indicate that increases in SA bacteremia rates correlated significantly with increasing numbers of admissions to hospitals. The main increase in SA bacteremia rates was represented by nosocomial infection, although increasing blood-culturing activity during the period may have contributed.

Attenuation of the bacterial load in blood by pretreatment with granulocyte-colony-stimulating factor protects rats from fatal outcome and brain damage during Streptococcus pneumoniae meningitis.

A model of pneumococcal meningitis in young adult rats receiving antibiotics once the infection was established was developed. The intent was to mimic clinical and histopathological features of pneumococcal meningitis in humans. The primary aim of the present study was to evaluate whether medical boosting of the peripheral neutrophil count affected the outcome of the meningitis. The risk of terminal illness over the first 7 days after infection was significantly reduced for rats who had elevated peripheral white blood cell counts after receiving granulocyte-colony-stimulating factor (G-CSF) prior to the infection compared to that for untreated rats (P = 0.039 by the log rank test). The improved outcome was associated with reduced signs of cerebral cortical damage (P = 0.008). Furthermore, the beneficial effects of G-CSF were associated with reduced bacterial loads in the cerebrospinal fluid (median, 1.1 x 10(5) versus 2.9 x 10(5) CFU/ml; P = 0.023) and in blood (median, 2.9 x 10(2) versus 6.3 x 10(2) CFU/ml; P = 0.024), as well as attenuated pleocytosis (median, 800 x 10(6) versus 1,231 x 10(6) cells/liter; P = 0.025), 24 h after the infection. Conversely, initiation of G-CSF therapy 28 h postinfection did not alter the clinical or histological outcome relative to that for non-G-CSF-treated rats. The magnitude of bacteremia and pretreatment with G-CSF were found to be prognostic factors for both outcome and brain damage. In summary, elevated neutrophil levels prior to the development of meningitis result in reduced risks of death and brain damage. This beneficial effect is most likely achieved through improved control of the systemic disease.

Selection of resistant Streptococcus pneumoniae during penicillin treatment in vitro and in three animal models.

Pharmacokinetic (PK) and pharmacodynamic (PD) properties for the selection of resistant pneumococci were studied by using three strains of the same serotype (6B) for mixed-culture infection in time-kill experiments in vitro and in three different animal models, the mouse peritonitis, the mouse thigh, and the rabbit tissue cage models. Treatment regimens with penicillin were designed to give a wide range of T(>MIC)s, the amounts of time for which the drug concentrations in serum were above the MIC. The mixed culture of the three pneumococcal strains, 10(7) CFU of strain A (MIC of penicillin, 0.016 micro g/ml; erythromycin resistant)/ml, 10(6) CFU of strain B (MIC of penicillin, 0.25 micro g/ml)/ml, and 10(5) CFU of strain C (MIC of penicillin, 4 micro g/ml)/ml, was used in the two mouse models, and a mixture of 10(5) CFU of strain A/ml, 10(4) CFU of strain B/ml, and 10(3) CFU of strain C/ml was used in the rabbit tissue cage model. During the different treatment regimens, the differences in numbers of CFU between treated and control animals were calculated to measure the efficacies of the regimens. Selective media with erythromycin or different penicillin concentrations were used to quantify the strains separately. The efficacies of penicillin in vitro were similar when individual strains or mixed cultures were studied. The eradication of the bacteria, independent of the susceptibility of the strain or strains or the presence of the strains in a mixture or on their own, followed the well-known PK and PD rules for treatment with beta-lactams: a maximum efficacy was seen when the T(>MIC) was >40 to 50% of the observation time and the ratio of the maximum concentration of the drug in serum to the MIC was >10. It was possible in all three models to select for the less-susceptible strains by using insufficient treatments. In the rabbit tissue cage model, a regrowth of pneumococci was observed; in the mouse thigh model, the ratio between the different strains changed in favor of the less-susceptible strains; and in the mouse peritonitis model, the susceptible strain disappeared and was overgrown by the less-susceptible strains. These findings with the experimental infection models confirm the importance of eradicating all the bacteria taking part in the infectious process in order to avoid selection of resistant clones.