Are variable repeats in the spa gene suitable targets for epidemiological studies of methicillin-resistant Staphylococcus aureus strains?
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Genes, Bacterial↗
Biomedical subjects
F Espersen
Publications and source records attributed to F Espersen.
Staphylococcus aureus carriage and infections among patients in four haemo- and peritoneal-dialysis centres in Denmark. The Danish Study Group of Peritonitis in Dialysis (DASPID).
A three-month prospective surveillance study was undertaken in four dialysis centres to establish the prevalence of Staphylococcus aureus carriage in a Danish population of patients on haemodialysis (HD) or on continuous ambulatory peritoneal dialysis (CAPD). General data such as sex, age, diagnosis, number of months in dialysis, hospital and ward were registered on a precoded form. Standardized nose and four skin swabs (axillae, groins, perineum) were performed on the first day of the survey. After one and two months, nose swabs were collected. Infections were registered and cultures were sent for phage-typing together with the S. aureus strains isolated from the swabs; 59.5% of HD patients and 51.2% of CAPD patients carried S. aureus. Permanent carriage was most frequent (P < 0.00009), primarily in the nose (44.0 and 34.9%, respectively in HD and CAPD). Skin carriage alone was rare (2.4 and 4.7%). Approximately one third (36.6 and 40.7%) of infections were caused by S. aureus. Although diabetics were not significantly more frequent carriers (60.5%) than non-diabetics (55.0%), the incidence of infection was much higher (26.3% vs. 10.3%, P = 0.004). In CAPD, peritonitis and tunnel/exit-site infections predominated (81.4%), often caused by S. aureus (34.8%). More than two thirds of the infections in HD patients were related to intravascular catheterization. The most serious infection was septicaemia, in all cases due to S. aureus. S aureus infections occurred significantly more frequently among carriers (P = 0.005), and more than half the patients were infected by the same or possibly the same strain as they carried in the nose or on skin. Different regimens for the elimination of S. aureus carriage in dialysis patients are discussed. A policy for risk assessment of patients should be developed, and the elimination of S. aureus carriage before dialysis should be encouraged. Controlled trials comparing the cost-effectiveness of recommended regimens to eliminate carriage in HD/CAPD patients are needed. Nose swabs are reliable indicators of carriage in dialysis patients.
Carrier State↗
Retrograde contamination and practical handling of urine-meters: a comparison of three systems for the measurement of hourly diuresis in an experimental bladder-drainage model and in clinical use.
OBJECTIVE: To compare three different urine metering systems for their ability to prevent retrograde contamination in an in vitro model of a closed urinary drainage system and for qualities important to their practical handling in a clinical setting. PATIENTS, MATERIALS AND METHODS: Using three urine-meters (the Braun Ureofix 511, the Kendall Curity 4000 and the Unoplast Unometer 500) the in vitro model was constantly flushed with a solution of Mueller-Hinton broth diluted with saline. On the first day, the urine collecting bag was inoculated with 10(8) cells of Pseudomonas aeruginosa. The system was operated for 12 days with daily sampling of the model bladder to detect any contamination. After 12 days the experiment was stopped and sampling performed at various locations, including the urine-meter and the tubing. Nine of each type of urine-meter were tested, i.e. three in three different experiments. In the clinical study, 45 patients were randomized to each of the three urine-meters and the nurses attending them were asked to complete a questionnaire on the practical handling of the urine-meters. RESULTS: When the urine-meters was omitted from the model system, the 'bladder' became contaminated with the test bacteria within 3 days. None of the nine Unometer 500 systems became contaminated, compared with four of each of the other two systems (P < 0.05). In clinical use, the Unometer 500 and Ureofix 511 were easier to suspend and empty than was the Curity 4000. The Unometer 500 was significantly easier to handle when the collecting bag was emptied. CONCLUSION: Urine-meters can prevent retrograde contamination in a closed bladder-drainage model, but the degree of prevention depends upon the type of urine-meter. In daily practice, there were differences in the ease of suspension of the systems and in the emptying of the urine-meter and collecting bag.
Attitude of Health Personnel↗
Surface heparinization of central venous catheters reduces microbial colonization in vitro and in vivo: results from a prospective, randomized trial.
OBJECTIVE: To evaluate in vitro and in vivo the efficacy of covalent end point-attached heparin to single-lumen polyurethane central venous catheters in reducing microbial adherence and colonization. DESIGN: In vitro study: A controlled bench study. In vivo study: A prospective, randomized, double-blind, clinical trial. SETTING: Intensive care unit in a 1200-bed teaching hospital. INTERVENTIONS: In vitro study: Adhesion of 17 radiolabeled clinical isolates of Staphylococci to catheters was examined in vitro. In vivo study: The outcome of heparinized and control catheters was compared in vivo in patients receiving long-term parenteral nutrition. Fifty-five adult patients were prospectively, blindly randomized to heparinized or control central venous catheters. The catheters, removed on clinical grounds, were analyzed with semiquantitative and quantitative cultures. Blood cultures were done at catheter removal. MEASUREMENTS AND MAIN RESULTS: In vitro study: Coagulase-negative Staphylococci adhered less in vitro to heparinized catheters than to control catheters (p < .05). In vivo study: Among 32 central venous catheters, or patients who completed the study, catheter-associated bacteremia or fungemia was observed in five patients in the control group (n = 19) and in no patient with a heparinized catheter (n = 13) (p = .047). Four of 13 catheters in the heparin group were colonized compared with 14 of 19 in the control group (p = .03). Coagulase-negative Staphylococci were the most frequent microorganisms in both groups. The numbers of organisms found on colonized catheters were larger in the control group than in the heparin group. CONCLUSIONS: Covalent end point surface heparinization appears to have a great impact on both in vitro and in vivo bacterial colonization of central venous catheters. Such heparinization can be a practical and economical approach to the prevention of catheter-associated bacteremia or fungemia.
Adult↗
Aminoglycoside resistance among Danish blood culture isolates of coagulase-negative staphylococci.
A sample of 137 coagulase-negative staphylococci isolated from blood cultures in Denmark over a 4-month period during 1992-1993 were tested for aminoglycoside resistance and for the presence of aminoglycoside-modifying enzymes. This was done on the basis of minimum inhibitory concentrations (MICs) measured by agar dilution, inhibition zone diameter by disk diffusion, and DNA dot blot analysis. Using the National Committee for Clinical Laboratory Standards (NCCLS) MIC breakpoints, 5%, 46%, 57%, and 63% of the strains were resistant to netilmicin, amikacin, gentamicin and tobramycin, respectively. The large majority of resistant staphylococci strains produced the bifunctional AAC(6)-III+APH(2") enzyme. The presence of AAC(6)-III+APH(2") explains the high level of resistance to gentamicin, kanamycin and tobramycin. In contrast to our results. Staphylococcus haemolyticus strains are usually reported to be more resistant than Staphylococcus epidermidis strains.
Aminoglycosides↗
A 6-month prospective study of hospital-acquired bacteremia in Copenhagen county.
During a 6-month period, 892 positive blood cultures were detected in the Copenhagen County hospitals. 302 (34%) were regarded as contaminations, and of the remaining cases 419 (71%) were community-acquired and 171 (29%) hospital-acquired, giving incidence rates of 6.8/1,000 admissions and 2.8/1,000 admissions, respectively. Both frequency and rate of hospital-acquired bacteremia were lower compared to most other studies. E. coli was more commonly found in community-acquired infections, while coagulase-negative staphylococci were the organisms most often considered as a contaminant. The main causative organisms in hospital-acquired infections were S. aureus (n = 37) and E. coli (n = 34). The proportion of polymicrobial bacteremias in this study was lower compared to most other studies (8%). E. coli from hospital-acquired infections were resistant to ampicillin in 42% of cases, but other Enterobacteriaceae showed higher percentage of resistance to beta-lactam antibiotics. S. aureus was penicillin-resistant in 92% of cases, but no methicillin-resistant strains were isolated. The frequency of antibiotic resistance was low compared to reports from other countries. A total of 136 hospital-acquired cases were followed prospectively. 61% of the patients were male and 46% were > or = 60 years of age. Most patients had predisposing diseases, 90% had foreign body and/or recent surgery performed, and 74 (54%) had an intraveneous catheter. The portal of entry was known in 132 (97%) of the cases, the most common being the urinary tract (42%), followed by an intravenous catheter (30%). The prevalence of urinary tract catheters gave an increased number of cases with E. coli bacteremia. The mortality was 16%.
Adolescent↗
In vitro activity of six macrolides, clindamycin and tetracycline on Streptococcus pneumoniae with different penicillin susceptibilities.
A collection of 99 clinical isolates of Streptococcus pneumoniae, chosen due to their different susceptibilities to penicillin, were investigated with respect to their susceptibility to the macrolides azithromycin, clarithromycin, dirithromycin, erythromycin, roxithromycin, spiramycin, and to clindamycin and tetracycline by the agar dilution method. We found complete cross resistance among the macrolides. The pneumococci were either susceptible, MIC < or = 0.5 micrograms/ml, or resistant, MIC > or = 16 micrograms/ml, to the tested macrolides, giving a bimodal distribution. In addition, complete cross resistance was observed between clindamycin and macrolides. Pneumococci resistant to macrolides were also resistant to tetracycline, and 26% of the macrolide-susceptible strains were tetracycline resistant.
Anti-Bacterial Agents↗
Aminoglycoside resistance mechanisms in Enterobacteriaceae and Pseudomonas spp. from two Danish hospitals: correlation with type of aminoglycoside used.
Sixty-two aminoglycoside-resistant Gram-negative enteric bacteria were isolated over a 3-year period from two hospitals (Bispebjerg and Esbjerg) among a total of almost 270,000 isolates. These hospitals were selected because of their different aminoglycoside policies during the years investigated. At Bispebjerg Hospital the principal aminoglycoside used was tobramycin, while gentamicin was the first choice at Esbjerg Hospital. Escherichia coli was the most frequently found aminoglycoside-resistant species. Among the 61 aminoglycoside-resistant strains studied, resistance was due to aminoglycoside-modifying enzymes in all except two Xanthomonas maltophilia strains. The ANT(2") enzyme occurred significantly more often at Esbjerg Hospital (p = 0.001), while enzymes of the AAC(3) or AAC(6') moieties were more common, but not significantly so, at Bispebjerg Hospital. The phenotypic pattern of aminoglycoside resistance, as determined by disc diffusion, correlated 100% with the ANT(2") and AAC(3)-V (the two most common enzymes among the isolates) genotype of the organisms as established using DNA probes. Median minimum inhibitory concentrations (MICs) (mg/l) for clinically utilized aminoglycosides were: amikacin (1.6), gentamicin (25.0), kanamycin (50.0), netilmicin (1.6-25.0) and tobramycin (12.5-50.0). Isolates from Bispebjerg Hospital revealed significantly higher MICs for netilmicin and tobramycin (p < 0.01) as compared to isolates from Esbjerg Hospital.
Aminoglycosides↗
[Treatment of severe staphylococcal infections].
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Anti-Bacterial Agents↗
High levels of complement-activation capacity in sera from patients with cystic fibrosis correlate with high levels of IgG3 antibodies to Pseudomonas aeruginosa antigens and poor lung function.
Heat-stable opsonins from sera of cystic fibrosis (CF) patients were investigated for their ability to activate complement. Complement activation by Pseudomonas aeruginosa after opsonization with patient serum was examined in a complement-consumption assay. Absorption of patients' sera with formalin-treated and boiled bacteria removed specific antibodies and the complement activation decreased. We found a positive correlation between serum complement-activation ability and IgG3 antibody levels to lipopolysaccharide (LPS), alginate, and a crude mixture of P. aeruginosa antigens (sonicate) in a group of patients with high levels of anti-Pseudomonas precipitins. In the same group of patients a significant negative correlation was found between complement activation and lung function. Eighteen patients have been followed longitudinally with serum samples covering the pre-infection, the early, and the late stages of chronic infection. Patients with poor lung function showed significantly higher levels of complement-activation capacity. We conclude that patients with high levels of specific IgG3 antibodies are able to induce a high level of complement activation and then develop more aggressive pulmonary tissue damage, probably secondary to local immune complex formation.
Adolescent↗
beta-Lactamase production and genetic location in Staphylococcus aureus: introduction of a beta-lactamase plasmid in strains of phage group II.
Staphylococcus aureus strains of phage group II have increased in frequency in hospital-acquired infections during recent years. A total of 184 penicillin resistant group II strains from bacteraemia cases in the years 1961-1990 were analysed for the amount of beta-lactamase produced and the location of the beta-lactamase gene. Until 1977 all strains investigated had a chromosomally located beta-lactamase gene, but since then a 21 kb beta-lactamase plasmid has increased in occurrence among group II strains, especially among those strains typable only at high phage concentrations [100 x Routine Test Dilution (RTD) and 1000 x RTD]. In 1990, 84% of the group II strains contained this plasmid. Plasmid-containing strains produced more beta-lactamase than strains without the plasmid. S. aureus strains of the 94,96 complex, which since 1984 have decreased in frequency from 18 to 9% in 1993, have remained high producers of beta-lactamase.
Bacteriophage Typing↗
Carriage of Staphylococcus aureus among 104 healthy persons during a 19-month period.
The present study was undertaken to investigate the frequency of the nasal carrier rate of Staphylococcus aureus. The investigation was performed on 104 healthy persons. The total number of swabs performed was 1498 and this resulted in isolation of 522 S. aureus strains. All strains have been identified, tested for antibiotic susceptibility, and phage-typed. The carrier-index (number of positive swabs/number of total swabs for each individual person) was compared with different sampling and culturing methods, phage type, age, and resistance to antibiotics. There was statistical difference in carrier rate according to sex (P < 0.05). Among the 104 persons 15 (14.4%) were persistent carriers, 17 (16.3%) intermittent carriers, 55 (52.9%) occasional carriers and 17 (16.3%) non-carriers. Among intermittent and occasional carriers the phage-type distribution was different from the S. aureus strains isolated from Danish hospitalized patients in 1992, while the persistent carriers had similar phage-type distribution.
Adult↗
No difference in enterotoxin production among Staphylococcus aureus strains isolated from blood compared with strains isolated from healthy carriers.
The production of enterotoxin A, B, C and D by 196 Staphylococcus aureus strains isolated from blood cultures and 95 strains from nasal carriers was investigated. Half of the bacteraemia strains were from patients who died with or because of their infection, the other half from patients who survived. The nasal strains were selected to match the bacteraemia strains regarding phage types. Overall, 30.6% of the bacteraemia strains and 40.0% of the nasal strains produced enterotoxins; enterotoxins B and C were the toxins produced most frequently in both groups. A similar incidence and pattern of enterotoxin production was found among the bacteraemia strains of S. aureus regardless of acquisition of the infection, the portal of entry, presence or absence of endocarditis and outcome of the infection. Thus, the concept that the enterotoxins play an important role in staphylococcal infections, apart from the diseases caused by the toxins per se such as food poisoning and toxic shock syndrome, cannot be substantiated by the results of the present study.
Bacteremia↗
Evaluation of staphylococci isolated from a blood culture system (Colorbact).
During a one-year period, all blood cultures positive for staphylococci from two of the smaller Danish counties with non-university hospitals only were evaluated. The isolates were speciated and coagulase-negative staphylococci (CoNS) were biotyped. Furthermore, antibiogram, phage typing and lectin typing were performed for all isolates. Clinical information was obtained by telephone, and before any bacteriological identification was performed, a preliminary judgment was made as to whether the positive blood culture was of clinical significance. A total of 3,500 blood cultures were evaluated and 426 (12.2%) were positive. One hundred and sixty blood cultures from 137 patients contained staphylococci; 36 of these patients had a pure culture of Staphylococcus aureus. One hundred and twenty-four CoNS were found and identified as S. epidermidis (81), S. hominis (19), S. haemolyticus (8), S. simulans (1), and Micrococcus species (3), and another 12 staphylococcal isolates which could not be identified to species level. A total of 35 patients had mixed cultures, including 6 with S. aureus as one of the isolates and 15 with mixed CoNS. Clinical relevance was estimated in 90% of cases where the later bacterial identification showed S. aureus, whereas clinical relevance was absent in the majority of cases including CoNS. Methicillin and gentamicin resistance was absent among S. aureus, but frequent among CoNS, especially S. epidermidis, where 40% were resistant to methicillin and 30% to gentamicin.
Bacteremia↗
Comparison of adherent and non-adherent staphylococci in the induction of polymorphonuclear leukocyte activation in vitro.
The ability to consume complement and activate neutrophils was investigated for staphylococci adherent to silicone surfaces and non-adherent staphylococci. Staphylococcus epidermidis strain ATCC 14990 and Staphylococcus aureus strain E 2371 were used in this study. The bacteria were allowed to adhere to silicone catheter segments for 2 h at 37 degrees C. Complement consumption was measured by reduction in serum haemolytic activity against sheep red blood cells. The induction of chemiluminescence was measured after opsonization of the staphylococci in 20% AB-positive human serum for 60 min at 37 degrees C. The bacteria consumed complement to approximately the same extent when adherent to the catheter segments, but more slowly in comparison with planktonic bacteria. When planktonic bacteria were compared, complement was consumed more quickly by S. epidermidis than by S. aureus. Measuring the induction of chemiluminescence by planktonic bacteria, S. epidermidis induced a lower response than S. aureus, while when adherent to the catheter segments the bacteria induced similar responses. These responses were only 15 to 20% of those induced by planktonic bacteria and only slightly higher than the spontaneous chemiluminescence by the neutrophils. Inter-strain variation was found, but all strains induced about the same low chemiluminescence when adherent to the catheter segments. The reduction in inflammatory response caused by adherence of staphylococci to catheter segments may interfere with phagocytosis and elimination of S. epidermidis during the early establishment of a foreign body infection.
Bacterial Adhesion↗
Experimental Streptococcus pneumoniae infection in mice for studying correlation of in vitro and in vivo activities of penicillin against pneumococci with various susceptibilities to penicillin.
The purpose of the study was to investigate the correlation of in vitro activity with the in vivo effect and the pharmacokinetics of penicillin in the treatment of infections with pneumococci with various susceptibilities to penicillin. We used 10 pneumococcal strains for which penicillin MICs ranged from 0.016 to 8 micrograms/ml. Time-kill curve experiments were performed with all strains. We found that the effect of penicillin in vitro is concentration independent, with a maximum effect at two to four times the MIC for penicillin-susceptible as well as penicillin-resistant pneumococci. The mouse peritonitis model with an inoculum of approximately 10(6) CFU, to which mucin was added, resulted in a reproducible lethal infection with the pneumococci. The 50% effective dose was determined for each strain, and we found a highly significant correlation between the log MIC and the log 50% effective dose of penicillin against these strains (P < 0.01). Furthermore, it was shown that the most important pharmacokinetic parameter determining the effect of penicillin in vivo was the time that the concentration of penicillin in serum was greater than the MIC.
Animals↗
Isolation and preliminary evaluation of a low-molecular-mass antigen preparation for improved detection of Helicobacter pylori immunoglobulin G antibodies.
Previously, immunoglobulin G (IgG) antibodies to five antigens with a relative molecular mass of between 15 and 30 kDa from Helicobacter pylori were found to be significantly more frequent in H. pylori-infected patients than in noninfected patients. In this study, these specific low-molecular-mass (LMW) antigens were separated by ultrafiltration of whole-cell sonicates. The LMW antigen preparation was evaluated by enzyme-linked immunosorbent assay with serum samples from 76 children with abdominal symptoms and 151 adults with dyspeptic symptoms. H. pylori was cultured or seen in 40 (53%) children and 83 (55%) adults. Increased antibody levels to H. pylori were found in serum from 35 (46%) children and 88 (58%) adults. Values for sensitivity, specificity, and predictive value of positive and negative results of the test were higher with LMW antigens than with the heat-stable antigen previously described. The low specificity and predictive value of a positive result were due to seropositive results for 21 persons with a negative culture for H. pylori and negative microscopy results for Helicobacter-like organisms in biopsies from gastric mucosa. Histologically, chronic gastritis was demonstrated in 43% of these persons, and 19% had peptic ulcer, indicating that they have or have had H. pylori infection. Specific antibodies to H. pylori were confirmed in all 21 patients by the Western immunoblot technique. Use of the LMW antigen improved the IgG antibody detection in patients with H. pylori infection, even though the results reflect the difficulties in establishing a true gold standard for diagnosis of H. pylori infection.
Adolescent↗
Staphylococcus aureus endocarditis in Danish intravenous drug users: high proportion of left-sided endocarditis.
In a retrospective study covering the years 1982-1989 episodes of Staphylococcus aureus endocarditis in 51 intravenous drug users were studied. Tricuspid involvement dominated (34/51), but the frequency of left-sided involvement (33.3%) was greater than in earlier reports. Involvement of both sides of the heart was not detected, but 27.8% of the left-sided endocarditis cases had multiple pulmonary infiltrates, indicating that some of them might have had a concomitant right-sided endocarditis. The 2 groups were compared: patients with left-sided endocarditis were significantly older and with a longer time of intravenous drug use. The complication rate was the same (44.1%) as was the duration of antibiotic treatment (median 42 days). In total, five patients underwent surgery, two (5.8%) due to right-sided failure and three (29.4%) because of left-sided endocarditis. The mortality of tricuspid endocarditis was low (2.9%), whereas 5 patients (29.4%) with left-sided involvement died. The patients who died were significantly older and had a shorter duration of symptoms before hospitalization.
Adolescent↗