Klaus Weist

How many infections are caused by patient-to-patient transmission in intensive care units?*

Objective:The proportion of intensive care unit (ICU)-acquired infections that are a consequence of nosocomial cross-transmission between patients in tertiary ICUs is unknown. Such information would be useful for the implementation of appropriate infection control measures. Design:A prospective cohort study during 18 months. Setting:Five ICUs from two university hospitals. Patients:All patients admitted for ≥48 hrs. Measurement:ICU-acquired infections were ascertained during daily bedside patient and chart reviews. Episodes of potential cross-transmission were identified by highly discriminating genetic typing of all clinical and surveillance isolates of the ten bacterial species most frequently associated with nosocomial infections in ICUs. Isolation of indistinguishable isolates in two or more patients defined potential transmission episodes. Main Results:During 28,498 patient days, 431 ICU-acquired infections and 141 episodes of nosocomial transmissions were identified. A total of 278 infections were caused by the ten species that were genotyped, and 41 of these (14.5%) could be associated with transmissions between patients. Conclusion:Infections acquired during treatment in modern tertiary ICUs are common, but a causative role of direct patient-to-patient transmission can only be ascertained for a minority of these infections on the basis of routine microbiological investigations.

An outbreak of pyodermas among neonates caused by ultrasound gel contaminated with methicillin-susceptible Staphylococcus aureus.

OBJECTIVE To investigate an outbreak of methicillin-susceptible Staphylococcus aureus (MSSA) infections in a neonatal clinic. DESIGN Prospective chart review, environmental sampling, and genotyping by two independent methods: pulsed-field gel electrophoresis (PFGE) and randomly amplified polymorphic DNA polymerase chain reaction (RAPD-PCR). A case-control study was performed with 31 controls from the same clinic. SETTING A German 1,350-bed tertiary-care teaching university hospital. RESULTS There was a significant increase in the incidence of pyodermas with MSSA; 10 neonates in good physical condition with no infection immediately after birth developed pyodermas. A shared spatula and ultrasound gel were the only identified infection sources. The gel contained MSSA and was used for hip joint sonographies in all neonates. PFGE and RAPD-PCR patterns from 6 neonates and from the gel were indistinguishable and thus genetically related clones. The case-control study revealed no significant risk factor with the exception of cesarean section (P=.006). The attack rate by days of hip-joint sonography between April 15 and April 27, 1994, was 11.8% to 40%. CONCLUSIONS Inappropriate hygienic measures in connection with lubricants during routine ultrasound scanning may lead to nosocomial S. aureus infections of the skin. To our knowledge this source of S. aureus infections has not previously been described.

Catheter-associated primary bloodstream infections: Epidemiology and preventive methods

SummaryThe incidence of catheter-associated primary bloodstream infections (BSIs) in Germany as defined by the CDC (Centers for Disease Control) has been determined on the basis of (a) a national prevalence study in a representative sample of 72 hospitals (NIDEP*), and (b) an incidence study in which data about the use and duration of insertion of central venous catheters (CVC) and of catheter-associated BSI were collected from 25 intensive-care units (ICUs) participating in the hospital infection surveillance system (KISS+) and analyzed. The first study showed primary bloodstream infection to be the fourth most frequent nosocomial infection at 8.3% of all nosocomial infections. With an ICU prevalence of 2.1%, primary BSI comprises 12.8% of all nosocomial infections observated in ICU patients. The second study showed a 60.4% prevalence of CVC use in German ICUs. An analysis of 55,400 CVC days in 14,988 ICU patients in the KISS hospitals yielded 2.2 CVC-associated BSIs per 1,000 CVC days (CI95 1.8–2.6). The rates of CVC-associated BSI on individual hospital wards were very variable and indicates a reduction potential. A reduction in the number of infections of about one-third would prevent 1,000–1,400 deaths due to CVC-associated BSI annually as well as about 40,000 to 60,000 extra days of hospital stay and the associated costs.

Is there an association between nosocomial infection rates and bacterial cross transmissions

Objective:Surveillance data of nosocomial infection rates are increasingly used for public reporting and interhospital comparisons. Approximately 15% of nosocomial infections on intensive care units are the result of patient-to-patient transmissions of the causative organisms. These exogenous infections could be prevented by adherence to basic infection control measures. The association between bacterial cross transmissions and nosocomial infection rates was analyzed. Design:Prospective cohort study during 24 months. Setting:Eleven intensive care units from two university hospitals. Patients:All inpatients. Interventions:None. Measurements and Main Results:Primary isolates of six indicator organisms (Acinetobacter baumannii, Enterococcus faecalis and E. faecium, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus) cultured from clinical samples or methicillin-resistant S. aureus surveillance testing of all inpatients were genotyped. Indistinguishable isolates in ≥2 patients defined potential episodes of transmissions. Surveillance of nosocomial infection rates was performed according to the German nosocomial infection surveillance system, Krankenhaus Infektions Surveillance System. Transmission events and nosocomial infection rates were pooled by intensive care unit to calculate Spearmans rank-correlation test. During 100,781 patient days, 100,829 microbiological specimens from 24,362 patients were sampled (average investigation density: 1.0 sample per patient and day) and 3419 primary indicator organisms were cultured. Altogether, 462 transmissions (incidence density of 4.6 transmissions per 1000 patient days; range, 1.4–8.4 days) and 1216 nosocomial infections (incidence density of 12.1 per 1000 patient days; range, 6.2–16.6 days) were discerned. Correlation analysis was unable to reveal any association between the incidence of cross transmissions and nosocomial infections, duration of hospitalization, or device use. Conclusions:Differences in nosocomial infection rates between study intensive care units are not explained solely by cross transmissions. Other factors, like the severity of the patients underlying diseases, the patients endogenous flora, or invasive procedures, likely have a dominant effect on the magnitude of nosocomial infection rates.

Evaluation of the BBL Crystal MRSA ID System for detection of oxacillin resistance in Staphylococcus aureus.

AIMS: To evaluate the BBL Crystal MRSA ID System for detection of oxacillin resistance in Staphylococcus aureus. METHODS: 52 methicillin resistant S aureus (MRSA) from five different countries and 85 methicillin susceptible S aureus (MSSA) were included. The species was confirmed by tube coagulation and detection of the clumping factor using the Staphaurex Plus. Clonal non-identity of the MRSA isolates was shown by pulsed field gel electrophoresis. MIC values (oxacillin) were determined using the Etest. Polymerase chain reaction was carried out to detect the mecA gene. The BBL Crystal MRSA ID System was carried out according to the manufacturers instructions. RESULTS: The BBL Crystal MRSA ID System showed fluorescence in 45 of 52 MRSA (sensitivity 86.5%; negative predicitive value 92.2%), and the specificity was 97.6% (positive predicitive value 95.7%). Two of seven MRSA that failed to show fluorescence had MIC values (oxacillin) of 4 mg/litre. CONCLUSIONS: The BBL Crystal MRSA ID System is a valuable test for detecting oxacillin resistance in S aureus. Its major advantage is the short time (4-5 hours) required to perform the test when organisms are grown on tryptic soy agar or sheep blood agar. Difficulties may arise in borderline resistant isolates.

Prävention nosokomialer Infektionen in der Intensivstation und im OP

ZusammenfassungNosokomiale Infektionen (NI) sind systemische oder lokale Infektionen, die bei der Krankenhausaufnahme weder vorhanden noch in der Inkubationsphase waren. Auf Intensivstationen wird ihr Auftreten besonders begünstigt, denn bei Intensivpatienten liegen häufig bereits bei der Aufnahme auf die Intensivstation wesentliche prädisponierende Faktoren für das Entstehen von NI vor,viele infektionsbegünstigende invasive diagnostische und therapeutische Maßnahmen müssen angewandt werden,es ist ein besonders hoher Pflegeaufwand erforderlich und damit ein intensiver Kontakt zwischen Patient und Personal, unddurch das insgesamt häufigere Auftreten von Infektionen auf Intensivstationen, u.a. auch durch multiresistente Erreger, sind die Möglichkeiten der Exposition ungleich größer als in anderen Krankenhausbereichen.Abgesehen von den verschiedenen prädisponierenden Faktoren der Patienten hat vor allem das Geschehen im OP wesentlichen Einfluß auf das Zustandekommen von postoperativen Wundinfektionen. Deshalb können Anästhesisten mit ihren Kenntnissen und ihrem Verhalten auch hier erheblich zur Infektionsprophylaxe beitragen.

Untersuchung von Infektionsausbrüchen im Krankenhaus

Von einem Ausbruch nosokomialer Infektionen wird gesprochen, wenn es zu einer Häufung einer Infektionskrankheit oder der Besiedlung mit einem bestimmten Erreger kommt, die im zeitlichen Zusammenhang mit einer stationären oder einer ambulanten medizinischen Maßnahme steht, soweit die Krankheit nicht bereits vorher bestand oder in Inkubation war. Um einen Ausbruch zu bekämpfen, ist eine genaue wissenschaftliche Untersuchung unter Anwendung epidemiologischer Methoden notwendig. Ein Ausbruch wird in der Epidemiologie definiert als das Auftreten von mehr Fällen einer Krankheit als räumlich und zeitlich zu erwarten wären. Es wird in der Regel davon ausgegangen, dass diese Fälle eine gemeinsame Ursache haben oder miteinander in Verbindung stehen. Im Infektionsschutzgesetz (IfSG) wird ein Ausbruch definiert als das gehäufte Auftreten von Infektionen, bei denen ein epidemischer Zusammenhang wahrscheinlich ist oder vermutet wird. (§ 6 Absatz 3 IfSG).