National survey of methicillin-resistant Staphylococcus aureus in Belgian hospitals: detection methods, prevalence trends and infection control measures. The Groupement pour le Dépistage, l'Etude et la Prévention des Infections Hospitalières

Methicillin-ResistantStaphylococcus aureusEpidemiology and Control in Belgian Hospitals, 1991 to 1995

Objectives:To describe the Belgian methicillin-resis-tantStaphylococcus aureus(MRSA) surveillance network, the evolution of methods used in Belgian hospitals for MRSA detection and control, and MRSA incidence from 1994 to1995.

Design, Setting, and Participants:Questionnaire surveys; infection control physicians from acute-care hospitals in Belgium.

Intervention:Publication of national guidelines for MRSA control in 1993.

Results:The participation rate in surveys ranged from 42% to 57% of hospitals. In 1995, 88% of participants detected MRSA strains by disk diffusion tests, with little improvement in standardization since 1991. More centers employed the oxacillin agar screen method (27%), automated systems (29%), or a combination of methods (29%) than in 1991 (P<.005). Between 1991 and 1995, the proportion of hospitals reporting MRSA control measures increased from 68% to 95% (P<.01). Practices that were used increasingly included patient placement in private room (from 50% to 93%,P<.01) and hand decontamination with antiseptic (from 43% to 87%,P<.01). The proportion of centers that reported screening MRSA carriers and treating them topically increased two- and threefold, respectively (P<.05). Surveillance data from 1994 to 1995 showed that MRSA represented a mean of 21.3% ofS aureusclinical isolates (range, 1.6% to 62.4%). The median incidence of nosocomial MRSA acquisition was 2.8 per 1,000 admissions, with a wide range (0 to 13.7 per 1,000 admissions) across hospitals of all sizes. The median incidence decreased over the first three semesters of surveillance in hospitals with continuous participation.

Conclusion:MRSA detection and control measures have improved in Belgian hospitals after publication of national guidelines. However, MRSA incidence rates show the persistence of nosocomial transmission, with large variations between centers. The national MRSA surveillance network should indicate whether control efforts eventually will curb the problem.

Methicillin-resistant Staphylococcus aureus phage plaque size enhancement using sublethal concentrations of antibiotics

Phage therapy presents an alternative approach against the emerging methicillin-resistant Staphylococcus aureus (MRSA) threat. Some of the problems encountered during isolation of MRSA phages include the high prevalence of enteric phages in natural sources, nonspecific absorption of viable phage, and the formation of pinpoint or tiny plaques. The phage isolated in this study, MR-5, also formed tiny plaques against its host S. aureus ATCC 43300 (MRSA), making its detection and enumeration difficult. An improved method of increasing the plaque size of MRSA phage by incorporating sublethal concentrations of three different classes of antibiotics (inhibitors of protein synthesis) in the classical double-layer agar (DLA) method was investigated. The β-lactam and quinolone antibiotics commonly employed in earlier studies for increasing the plaque size did not show any significant effect on the plaque size of isolated MR-5 phage. Linezolid (oxazolidinone class), tetracycline, and ketolide antibiotics brought significant enhancements (3 times the original size) in the plaque size of MR-5 phage. Prior treatment with these antibiotics resulted in significant reductions in the time of adsorption and the latent period of MR-5 phage. To rule out whether the action of linezolid (which brought the maximum increase in plaque size) was specific for a single phage only, its effect on the plaque size of seven other S. aureus-specific phages was also assessed. Significant enhancements in the plaque size of these phages were observed. These results indicate that this modification can therefore safely be incorporated in the traditional DLA overlay method to search for new MRSA-virulent phages.

Clinical profiles of patients colonized or infected with extended-spectrum beta-lactamase producing Enterobacteriaceae isolates: a 20 month retrospective study at a Belgian University Hospital

Background

Description of the clinical pictures of patients colonized or infected by ESBL-producing Enterobacteriaceae isolates and admitted to hospital are rather scarce in Europe. However, a better delineation of the clinical patterns associated with the carriage of ESBL-producing isolates may allow healthcare providers to identify more rapidly at risk patients. This matter is of particular concern because of the growing proportion of ESBL-producing Enterobacteriaceae species isolates worldwide.

Methods

We undertook a descriptive analysis of 114 consecutive patients in whom ESBL-producing Enterobacteriaceae isolates were collected from clinical specimens over a 20-month period. Clinical data were obtained through retrospective analysis of medical record charts. Microbiological cultures were carried out by standard laboratory methods.

Results

The proportion of ESBL-producing Enterobacteriaceae strains after exclusion of duplicate isolates was 4.5% and the incidence rate was 4.3 cases/1000 patients admitted. Healthcare-associated acquisition was important (n = 104) while community-acquisition was less frequently found (n = 10). Among the former group, two-thirds of the patients were aged over 65 years and 24% of these were living in nursing homes. Sixty-eight (65%) of the patients with healthcare-associated ESBL, were considered clinically infected. In this group, the number and severity of co-morbidities was high, particularly including diabetes mellitus and chronic renal insufficiency. Other known risk factors for ESBL colonization or infection such as prior antibiotic exposure, urinary catheter or previous hospitalisation were also often found. The four main diagnostic categories were: urinary tract infections, lower respiratory tract infections, septicaemia and intra-abdominal infections. For hospitalized patients, the median hospital length of stay was 23 days and the average mortality rate during hospitalization was 13% (Confidence Interval 95%: 7-19). Escherichia coli, by far, accounted as the most common ESBL-producing Enterobacteriaceae species (77/114; [68%]) while CTX-M-1 group was by far the most prevalent ESBL enzyme (n = 56).

Conclusion

In this retrospective study, the clinical profiles of patients carrying healthcare-associated ESBL-producing Enterobacteriacae is characterized by a high prevalence rate of several major co-morbidities and potential known risk factors. Both, the length of hospital stay and overall hospital mortality rates were particularly high. A prospective case-control matched study should be designed and performed in order to control for possible inclusion bias.

Methicillin resistance among Staphylococcus aureus isolates from Saudi hospitals

OBJECTIVE

To determine the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) strains among clinical isolates collected from the 4 tertiary hospitals in Makkah, Saudi Arabia, and to test the antimicrobial susceptibility patterns of S. aureus isolates against 9 antimicrobial agents.

MATERIALS AND METHODS

A total of 512 S. aureus clinical isolates were collected during a period of 1 year starting in April 2003 in Al-Noor, King Abdul-Aziz, Hera and King Faisal Hospitals, Makkah, Saudi Arabia. The sensitivity patterns of these isolates were determined using the Kirby-Bauer disk diffusion method.

RESULTS

The prevalence of MRSA among S. aureus isolates was 38.9% (199/512). Among 199 MRSA isolates, 78.8% showed multidrug resistance to erythromycin, gentamicin and oxytetracycline.

CONCLUSION

The rate of MRSA resistance in this study was much higher than what had been reported in other areas of Saudi Arabia emphasizing the need for local or country-based surveillance to characterize and monitor MRSA and to develop strategies that will improve MRSA treatment and control.

Carriage of resistant microorganisms in repatriates from foreign hospitals to The Netherlands

In a prospective survey conducted between May 1998 and September 2001, the prevalence of carriage of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE) and gentamicin-resistant Gram-negative bacilli (GGNB) was determined in 1167 patients repatriated from foreign hospitals to The Netherlands. Swab specimens, demographic data and clinical data were obtained during transfer of the patients from the foreign hospitals. The total prevalence of carriage of resistant microorganisms was 18.2%. MRSA was carried by 2.7% of all patients, and by 4.7% of the patients repatriated to a Dutch hospital. Antimicrobial treatment (adjusted odds ratio (OR) 3.4; 95% confidence interval (CI) 1.2-9.7), length of stay in a foreign hospital of > 14 days (adjusted OR 5.4; 95% CI 2.3-12) and artificial ventilation (adjusted OR 8.5; 95% CI 1.8-41) were risk factors for carriage of MRSA. VRE and GGNB were isolated from 2.7% and 14.1% of the patients, respectively. Transfer from Asia, and southern, southeastern and eastern Europe, were risk factors for carriage of GGNB. These carriage rates were high compared to those found in patients in Dutch hospitals, where the rates are < 1% for MRSA, 2% for VRE, and 4.5% for GGNB. The highest risk of acquisition of GGNB was associated with the country from where the patient was repatriated, rather than with the antimicrobial treatment received by the individual patient in the foreign hospital.

Bacterial colonization of patients undergoing international air transport: a prospective epidemiologic study

OBJECTIVE

To investigate the incidence of multiresistant bacteria in patients treated in foreign hospitals and repatriated by international interhospital air transport.

METHODS

This was a prospective epidemiologic study on patients who were hospitalized in a foreign country and repatriated to a hospital in their home country by international aeromedical transport on scheduled airlines or ambulance jets. The study was carried out by the Department of Pediatrics, Department of Medical Microbiology, University Hospital Frankfurt, Germany, and MedCall Germany, the organizing company for repatriation. One hundred and three patients, who were hospitalized abroad, required repatriation by international interhospital air transport and met the entry criteria.

RESULTS

Four hundred and eighty-three swabs from brow, nose, ear, throat, groin or axilla were taken from 103 patients, mean age 62 years. They were transported from southern and eastern European countries, Morocco, Egypt, Ghana, Tunisia, Pakistan, the United States and the Bahamas to destinations in Germany, the UK, Belgium, Switzerland, the United States and Japan. Forty-four patients were in an intensive care unit (ICU) for 6.5 days (median) prior to transport. Forty patients received antibiotics at the time of repatriation. Acinetobacter, Enterobacter, Pseudomonas, Proteus, Staphylococcus aureus and Candida were found. Methicillin-resistant Staphylococcus aureus (MRSA) was found in three patients (3%), ventilated for 17 days, and treated in the ICU for a median of 23 days. In 2 patients, multiresistant Acinetobacter baumanii and multiresistant Klebsiella pneumoniae were found.

CONCLUSIONS

Bacterial colonization of patients undergoing international interhospital air transport does not differ from that of patients in a European hospital. Multiresistant bacteria, especially MRSA, were found only in ICU patients. There is no elevated risk of transmission of multiresistant bacteria in this patient group compared to other patients treated in hospital, especially in ICUs.

Emergence and spread of gentamicin-susceptible strains of methicillin-resistant Staphylococcus aureus in Belgian hospitals

The aim of this study was to follow the evolution of the clonal distribution and antimicrobial susceptibility of clinical strains of methicillin-resistant Staphylococcus aureus (MRSA) recovered from Belgian hospitals between 1995 and 1997-1998. MRSA strains were genotyped by inter-IS256 spacer length polymorphism PCR and SmaI macrorestriction analysis. MICs of 18 antimicrobials were determined by the agar dilution method. MRSA strains from the 1997-1998 survey were further tested by vancomycin screen agar, E-test, broth microdilution methods, and population analysis. Between 1995 and 1997-1998, epidemic group A strains decreased in proportion from 73% to 44%, whereas MRSA Group B and C strains increased from 17% to 38% and from 5% to 8%. The proportion of strains susceptible to gentamicin increased between the surveys from 22% to 48%. This was associated with a higher proportion of group B and C strains in the last survey. Heterogeneous vancomycin-intermediate S. aureus (hetero-VISA) strains were found in 2% isolates from 1997 to 1998. These hetero-VISA isolates were genotypically related to the MRSA group A strains and were resistant to gentamicin. In conclusion, two emerging epidemic MRSA genotypes, susceptible to gentamicin, have spread among Belgian hospitals during the 1990s. Hetero-VISA were present at low frequency among MRSA strains belonging to a widespread endemic genotype.

Molecular epidemiology of predominant clones and sporadic strains of methicillin resistant Staphylococcus aureus in Switzerland and comparison with European epidemic clones

OBJECTIVE

To assess the molecular epidemiology and risk factors of predominant clones and sporadic strains of methicillin-resistant Staphylococcus aureus (MRSA) in Swiss hospitals and to compare them with European strains of epidemic clones.

MATERIAL AND METHODS

One-year national survey of MRSA cases. Analysis of epidemiological and molecular typing data (PFGE) of MRSA strains.

RESULTS

In 1997, 385 cases of MRSA were recorded in the five Swiss university hospitals and in 47 community hospitals. Half of the cases were found in Geneva hospitals where MRSA was already known to be endemic. Molecular typing of 288 isolates (one per case) showed that 186 (65%) belong to four predominant clones, three of which were mostly present in Geneva hospitals. In contrast, the fourth clone (85 cases) was found in 23 hospitals (in one to 16 cases per hospital). The remaining 35% of the strains were clustered into 62 pulsed field gel electrophoresis types. They accounted for one to five patients per hospital and were defined as sporadic. Multivariate analysis revealed no independent risk factors for harboring a predominant versus a sporadic strain, except that transfer from a foreign hospital increases the risk of harboring a sporadic strain (OR, 42; 95% CI, 5-360).

CONCLUSION

While cases with predominant clones were due to the local spread of these clones, most sporadic cases appear to be due to the continuous introduction of new strains into the country. With the exception of a transfer from a hospital outside Switzerland, no difference in the clinical or epidemiological characteristics was observed between patients harboring a predominant clone and those with a sporadic strain.

Increasing resistance to vancomycin and other glycopeptides in Staphylococcus aureus

Strains of Staphylococcus aureus with reduced susceptibility to glycopeptides have been reported from Japan, the United States, Europe, and the Far East. Although isolates with homogeneous resistance to vancomycin (MICs = 8 microg/mL) continue to be rare, there are increasing reports of strains showing heteroresistance, often with vancomycin MICs in the 1-4 microg/mL range. Most isolates with reduced susceptibility to vancomycin appear to have developed from preexisting methicillin-resistant S. aureus infections. Many of the isolates with reduced susceptibility to glycopeptides have been associated with therapeutic failures with vancomycin. Although nosocomial spread of the vancomycin-intermediate S. aureus (VISA) strains has not been observed in U.S. hospitals, spread of VISA strains has apparently occurred in Japan. Broth microdilution tests held a full 24 hours are optimal for detecting resistance in the laboratory; however, methods for detecting heteroresistant strains are still in flux. Disk-diffusion tests, including the Stokes method, do not detect VISA strains. The Centers for Disease Control and Prevention and other groups have issued recommendations regarding appropriate infection control procedures for patients infected with these strains.

Epidemiology of MRSA

Staphylococcus aureus is recognized as one of the major causes of infections in humans occurring in both the community and the hospital. Up to now one of the most serious aspects as far as treatment of S. aureus infections is concerned is resistance to methicillin, which in clinical terms indicates resistance to all beta-lactam antibiotics. The growing incidence of methicillin-resistant S. aureus (MRSA) infections worldwide, their multidrug resistance, several reservoirs of resistant strains, the facility to spread also outside hospitals and to cause outbreaks requires efficacious infection control measures. For this reason microbiological and epidemiological studies are of crucial importance.

Clonal dissemination of epidemic methicillin-resistant Staphylococcus aureus in Belgium and neighboring countries

OBJECTIVES

To determine the diversity of pulsed-field gel electrophoresis (PFGE) types among epidemic strains of methicillin-resistant Staphylococcus aureus (MRSA) recovered in Belgium, France, Germany and The Netherlands over the period 1981-94.

METHODS

MRSA strains collected in a multicenter survey in Belgium (n = 171) and from reference laboratories in neighboring countries (n = 102) were characterized by PFGE analysis using the SmaI enzyme.

RESULTS

In total, 32 PFGE types were found. Epidemic PFGE type 1, first recognized in 1984, accounted for 82% of Belgian strains (87% of hospitals) and 51% of European MRSA strains. Four other internationally epidemic PFGE types (types 8, 10, 11 and 12) were less widely disseminated and more recently detected (1991-94), each recovered from two or three countries. International spread of two PFGE types was linked to transfer of colonized patients to Dutch hospitals from another country where this type was frequently recovered.

CONCLUSIONS

Genotypic analysis indicated widespread distribution of several outbreak-associated MRSA strains over large European regions, which was in some instances related to interhospital patient transfer. These findings underscore the need for standardized international surveillance and control of MRSA transmission between healthcare institutions across Europe.

Rapid dissemination of Staphylococcus aureus with classic oxacillin resistance phenotype at a new university hospital

To determine the prevalence rates of oxacillin-resistant Staphylococcus aureus (ORSA) at a new university hospital since its opening, the results of disk diffusion tests on all clinical isolates, recovered between 1990 and 1998 at the National Cheng Kung University Hospital, were reviewed. In order, to investigate the mechanisms of oxacillin resistance among strains of S. aureus in Taiwan, MICs were determined by an agar dilution method, and polymerase chain reaction and colony hybridization assays were performed on 288 isolates collected during November 1998 to detect the mecA gene. The prevalence rates of ORSA increased rapidly from 14.1% in 1990 to 61.0% in 1998. The increasing rates were most rapid in the first four-year period, ranging from 11.6 to 106.7% per year, and became steady after 1994, ranging from 1.8% to 11.6%. Of 288 clinical isolates collected in November 1998, 206 (71.5%) were resistant to oxacillin (MIC >/= 16 mg/L), and four were borderline resistant (MIC 2-8 mg/L). All 210 strains possessed the mec A gene (classic resistance). The present study demonstrated that ORSA could disseminate in a new hospital with great speed, and indicated that all ORSA strains in Taiwan revealed classic resistance phenotype.

Methicillin-resistant Staphylococcus aureus in French hospitals: A 2-month survey in 43 hospitals, 1995

OBJECTIVE

To estimate the incidence of methicillin-resistant Staphylococcus aureus (MRSA) in patients hospitalized in French public hospitals.

DESIGN

A 2-month survey that included 163,573 patients and 140,114 admissions.

SETTING AND PATIENTS

Forty-three public or public-affiliated hospitals throughout France, including 12 university-affiliated hospitals. Information was recorded on all patients having MRSA recovered from culture of any clinical sample.

RESULTS

The overall median incidence rate (per 1,000 admissions) of clinically detected MRSA was 5.9 (range, 1.8-15.8); median rates were similar in hospitals affiliated or not affiliated to universities (6.4 and 5.9, respectively). Smaller unaffiliated hospitals (<500 beds) had higher MRSA incidence rates (mean, 7.2) than larger (>500 beds) unaffiliated hospitals or university hospitals (mean, 6.7 and 6.1, respectively). The incidence density (per 1,000 patient-days) of MRSA was higher in intensive-care units [ICUs] 2.39/1,000) than in surgical (0.80/1,000) and medical (0.70/1,000) wards, respectively; comparable rates were recorded in rehabilitation units (0.67/1,000), whereas in long-term-stay units, the incidence density of MRSA was 0.27/1,000 patient-days. Of 958 MRSA isolates, 660 (69%) also were resistant to all aminoglycosides. In 411 (43%) of 958 patients, the MRSA isolate was considered imported (ie, first recovered within 72 hours of the patient's admission to the unit). More than one half (53%) of imported cases were transfer patients from other hospitals, and 17% originated from ICUs.

CONCLUSION

MRSA is extensive in French hospitals. All categories of hospitals are involved to a similar extent, and there is intense circulation of patients colonized or infected with MRSA between units and hospitals. Containment of MRSA would mandate increasing resources devoted to infection control, especially in smaller hospitals, and control programs should involve notification of carriers and screening of patients at risk of MRSA carriage on admission to detect carriers and to implement isolation precautions rapidly.

Methicillin-resistant Staphylococcus aureus and antimicrobial use in Belgian hospitals

OBJECTIVE

To investigate relationships between the incidence of methicillin-resistant Staphylococcus aureus (MRSA) and the use of different classes of antimicrobials in Belgian hospitals.

DESIGN

Using Pearson correlation coefficients, the number of new nosocomial MRSA-colonized or -infected patients in the second half of 1994 and the first half of 1995 reported by the national MRSA surveillance program was compared with use of various antimicrobial classes as reported by the National Institute for Sickness and Disability Insurance. Relationships between different classes of antimicrobials were evaluated in a correlation matrix. MRSA incidence, antimicrobial use, and potential confounding factors were included in a multiple linear regression analysis.

SETTING

50 hospitals in Belgium.

RESULTS

The use of a number of different classes of antimicrobials was interrelated. In the multivariate analysis, the incidence of nosocomial MRSA increased with increasing use of ceftazidime and cefsulodin (P=.0003), amoxicillin with clavulanic acid (P=.02), and quinolones (P=.005). No association was found between MRSA incidence and total antimicrobial use.

CONCLUSIONS

The relationships between antimicrobial use and MRSA are complex. Interventions aimed at promoting more rational prescribing patterns should be supported by adequate experimental and epidemiological evidence. Advice for preventing and controlling MRSA has focused mainly on hygienic measures and precautions to avoid cross-transmission; the role of relieving antimicrobial pressure needs to be clarified.

Incidence of antibiotic resistance in blood and urine isolates from hospitalized patients. Report from a European collaborative study. European Study Group on Antibiotic Resistance (ESGAR)

During 1992-93, 2544 isolates from blood cultures, comprising 52% gram-negative bacilli, 24% Staphylococcus aureus, 15% other staphylococci, 7% Enterococcus faecalis and 2% E. faecium, were consecutively collected and identified in 30 laboratories in 21 European countries. In addition 2512 urine isolates, comprising 82% gram-negative bacilli, 3% S. aureus, 4% other staphylococci and 11% enterococci were collected. The bacteria were sent to 3 laboratories for susceptibility testing by the microdilution method in Mueller-Hinton broth. The MICs of penicillins and aztreonam for all susceptible gram-negative bacilli were 0.25-8 mg/l, penems 0.032-2 mg/l, cefotaxime, ceftazidime and cefpirome or cefepime 0.032-0.25 mg/l, gentamicin, tobramycin and netilmicin 0.125-2 mg/l, amikacin 0.5-4 mg/l, ciprofloxacin 0.016-1 mg/l, trimethoprim 0.25-1 mg/l and tetracycline 1-2 mg/l. For susceptible staphylococci the MICs of erythromycin were 0.25-0.5 mg/l, clindamycin 0.125-0.25 mg/l, methicillin 2-8 mg/l, vancomycin and trimethoprim 1-4 mg/l, ciprofloxacin 0.25-1 mg/l, gentamicin and tobramycin 0.25-1 mg/l. For the enterococci the MICs of ampicillin and vancomycin were 2-4 mg/l and of imipenem, teicoplanin and trimethoprim 0.5-1 mg/l. The antibiotic resistance rates varied between laboratories, being lower in northern Europe, except for the penems, cefpirome and cefepime, which showed uniformly lower resistance rates. Compared to the earlier European studies the resistance rates to beta-lactam antibiotics among the gram-negatives have not changed except with an increase to cefotaxime and ceftazidime in central Europe. Resistance to aminoglycosides had also increased in central Europe from 7-8% to 20-21%, but decreased in southern Europe from 22-24% to 13-14% among the blood isolates and from 12-28% to 6-7% among the urine isolates. There was an increase in resistance to ciprofloxacin and gentamicin in staphylococci from southern Europe. The prevalence of MRSA was significant in central and southern Europe. It is of importance that collaborative national and international studies on the incidence of antibiotic resistance are being performed on a repetitive basis.

Antimicrobial resistance in staphylococci. Epidemiology, molecular mechanisms, and clinical relevance

Staphylococcal infections continue to pose important clinical problems in children and adults. Antibiotic resistance among the staphylococci has rendered therapy of these infections a therapeutic challenge. Despite early, uniform susceptibility to penicillin, staphylococci acquired a gene elaborating beta-lactamase that rendered penicillin inactive and that is borne by nearly all clinical isolates. "Penicillinase-resistant beta-lactams," such as methicillin, were introduced in the early 1960s, but resistance to them has become an increasing concern. The mechanism of the so-called "methicillin resistance" is complex. Moreover, once confined to the ecology of hospitals and other institutions, a recent increase in community-acquired methicillin-resistant S. aureus infections has been observed. Glycopeptides, until now the only uniformly reliable therapeutic modality, have been increasingly used for therapy of staphylococcal infections. The recent recognition of clinical isolates with reduced susceptibility to glycopeptides is of concern.

Methicillin-resistance among Turkish isolates of Staphylococcus aureus strains from nosocomial and community infections and their resistance patterns using various antimicrobial agents

The purposes of this study were to determine the prevalence of Turkish isolates of methicillin-resistant Staphylococcus aureus (MRSA) in nosocomial and community infections and their antibiotic resistant patterns. The oxacillin disk diffusion method for the detection of methicillin resistance and the Kirby-Bauer disk diffusion for antibiotic susceptibility tests were used. A total 383 S. aureus strains were identified from different patients. The prevalence of methicillin resistance among S. aureus strains was 31.3% (120/383). The proportions of MRSA isolated from nosocomial and community infections were 26.4% (46/174) and 35.4% (74/209), respectively. The resistance rates of MRSA to other antibiotics were as follows: 71% resistant to erythromycin, 54% to clindamycin, 52% to gentamicin, 44.5% to trimethoprim-sulfamethoxazole and 36% to ciprofloxacin. No strain resistant to vancomycin was recorded in this study.

Increasing incidence and widespread dissemination of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals in central Europe, with special reference to German hospitals

OBJECTIVE: to present data on prevalence and interregional spread of methicillin-resistant Staphylococcus aureus (MRSA) in Germany. METHODS: A nationwide collection of MRSA isolates from nosocomial infections in 143 hospitals was established from isolates (n=4368) sent to a microbiological reference center during 1993--95. As chosen by distinguishable resistance phenotypes at each time of occurrence during the study period, 1830 isolates were subjected to molecular typing by means of Smal macrorestriction patterns, PCR for RNA gene spacer patterns, and PCR for patterns of DNA stretches flanked by the ERIC-2 sequence and flanked by Tn916 and ribosomal binding site. In addition, data from a multicenter study on the incidence of antibiotic resistance have been analyzed (32 centers, 637 S. aureus isolates). RESULTS: In 1995 the prevalence of MRSA among S. aureus isolates was 8.7% overall in central Europe (including Germany), in comparison to 1.7% in 1990. From 1993 until now, a continuous interregional dissemination of six epidemic strains, which were identified by molecular typing, was recorded. Besides these epidemic strains, 15 MRSA strains were identified which could not be allocated to the epidemic MRSA or to the known clonal groups of the species S. aureus. MRSA from three cases of sporadic nosocomial infections exhibited characteristics of the clonal group of S. aureus with the capacity for toxic shock syndrome formation. The pattern of one MRSA corresponded to those of the S. aureus group exhibiting phage pattern 94,96. CONCLUSIONS: The prevalence of MRSA has increased in central Europe (and Germany) during the last 5 years, to 8.7%. The main source of infection with MRSA is obviously interregional dissemination of epidemic strains. At the same time, the mecA gene has been acquired by strains previously sensitive to methicillin.

Origin and transmission of methicillin-resistant Staphylococcus aureus in an endemic situation: differences between geriatric and intensive-care patients

Imported vs. hospital-acquisition of MRSA was assessed in > 6000 patients at a large tertiary care teaching hospital. About five percent (5.1%) of patients carried MRSA on admission, mostly without clinical symptoms; the highest percentage (11.6%) being in geriatric patients. Hospital-acquisition of MRSA occurred in 1.7% of patients and was particularly high in intensive-care units (5.2%). Phenotype and genotype analysis of 158 MRSA strains isolated from 61 patients revealed a cluster of closely related strains in the hospital-acquired MRSA infections and the close relationship of this cluster to the regional epidemic MRSA strain. The MRSA strains imported by geriatric patients were genetically different, did not spread between geriatric patients and were only a minor source of nosocomial infection.

Changes in major populations of methicillin-resistant Staphylococcus aureus in Belgium

A total of 102 epidemic methicillin-resistant Staphylococcus aureus (MRSA) isolates collected in 13 Belgian hospitals during two periods (1981-1985 and 1991-1992) were tested for phage-type, for the presence of aminoglycoside-modifying enzymes (AME), and examined by arbitrarily primed polymerase chain reaction (AP-PCR). All isolates, but five, belonged to a few distinct phage-types of group III. Most isolates expressed a combination of AAC(6')-APH(2") with APH(3')III, and ANT(4',4") or both. Both phage-typing and AME suggested a change in the MRSA population between the two periods but the AP-PCR method revealed only slight differences.

Automatic Alerts for Methicillin-Resistant Staphylococcus aureus Surveillance and Control: Role of a Hospital Information System

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is an escalating problem in hospitals worldwide. The hospital reservoir for MRSA includes recognized and unrecognized colonized or infected patients, as well as previously colonized or infected patients readmitted to the hospital. Early and appropriate infection control measures (ICM) are key elements to reduce MRSA transmission and to control the hospital reservoir.

Objective: To describe the role of an expert system applied to the control of MRSA at a large medical center (1,600 beds) with high endemic rates.

Methods: The University Hospital of Geneva has an extended hospital information system (HIS), DIOGENE, structured with an open distributed architecture. It includes administrative, medical, nursing, and laboratory applications with their relational databases. Among available patient databases, clinical microbiology laboratory and admission-discharge-transfer (ADT) databases are used to generate computer alerts. A laboratory alert (lab alert) is printed daily in the Infection Control Program (ICP) offices, listing all patients with cultures positive for MRSA detected within the preceding 24 hours. Patients might be either newly detected patients colonized or infected with MRSA, or previously recognized MRSA patients having surveillance cultures. The ICP nurses subsequently go to the ward or call the ward personnel to implement ICM. A second alert, the “readmission alert,” detects readmission to the hospital of any patient previously colonized or infected with MRSA by periodic queries (q 1 min) to the ADT database. The readmission alert is printed in the ICP offices, but also forwarded with added guidelines to the emergency room.

Results: During the first 12 months of application (July 1994 to June 1995), the lab alert detected an average of 4.6 isolates per day, corresponding to 314 hospital admissions (248 patients); the use of this alert saved time for the ICP nurses by improving work organization. There were 438 readmission alerts (1.2 alerts per day) over the study period; of 347 patients screened immediately upon readmission, 114 (33%) were positive for MRSA carriage. Delayed recognition of readmitted MRSA carriers decreased significantly after the implementation of this alert; the proportion of MRSA patients recognized at the time of admission to the hospital increased from 13% in 1993 to 40% in 1995 (P<.001).

Conclusions: Hospital information system-based alerts can play an important role in the surveillance and early prevention of MRSA transmission, and it can help to recognize patterns of colonization and transmission.

Antimicrobial resistance in staphylococci

Staphylococci have developed a variety of strategies for dealing with the presence of antibiotics encountered in clinical environments. Resistance to beta-lactams and other antimicrobial agents has been accomplished by a diverse array of molecular mechanisms. Options available to treat infections caused by staphylococci resistant to methicillin are limited, and the next generation of antibiotics to be introduced, should glycopeptide resistance become an important clinical problem, is not yet on the horizon.