Infektionen durch Stenotrophomonas maltophilia (SMA) bei Intensivpatienten - eine prospektive Fall-Kontrollstudie

Hintergrund: Stenotrophomonas maltophilia (SMA) gewinnt als opportunistischer, meist multiresistenter Keim zunehmende Bedeutung für die Entwicklung schwerer nosokomialer Infektionen.

Methodik: Der Einfluss von Risikofaktoren auf die Entwicklung von SMA-Infektionen auf einer pneumologischen Intensivstation (ITS, 8 Betten) wurde prospektiv analysiert.

Ergebnisse: Von Juli 1997 bis Juni 1998 wurden 111 Patienten (80 Männer, 31 Frauen) mehr als 5 Tage auf der ITS behandelt (mittl. Alter ± SD: 58,0 ± 13,3 Jahre). SMA wurde mit signifikanter Keimzahl aus Untersuchungsmaterialien von 16/111 Pat. isoliert (13 Männer, drei Frauen, mittl. Alter ± SD 57,8 ± 3,4 Jahre), und zwar im Bronchialsekret (68 %), Sputum (19 %) und Pleuraerguss (13 %). Die univariate Analyse ergab 15 Risikofaktoren für eine SMA-Infektion auf einem Signifikanzniveau von p < 0,05. Die multivariate Analyse zeigte drei unabhängige Risikofaktoren: Chronisch obstruktive Lungenerkrankung (COPD, OR 95 % CI [1.91;∞]), Dauer des Intensivaufenthaltes (OR 95 % CI [1.07;1.26]) und die Applikation von Carbapenemen vor Aufnahme auf die ITS (OR 95 % CI [0.56; 153]). Vier von 16 Patienten starben an der SMA-Infektion, zwei im Rahmen der Exazerbation einer purulenten chronischen Bronchitis und zwei an einer Sepsis. Die Typisierung von 18 SMA-Isolaten von 15 Patienten ergab 9 verschiedene Genotypen. Die Analyse mittels Pulsfeld-Gel-Elektrophorese machte die direkte klonale Ausbreitung eines einzelnen SMA-Genotyps nur zwischen drei Patienten wahrscheinlich.

Folgerungen: Entscheidende Risikofaktoren für die Entwicklung einer SMA-Infektion auf der pneumologischen ITS sind demnach eine schwere COPD als Grunderkrankung, die Dauer des Intensivaufenthalts und der Selektionsdruck applizierter Antibiotika, insbesondere von Carbapenemen.

Infections caused by Stenotrophomonas maltophilia (SMA) in patients in intensive care units: a prospective case-control study

Background and objective: The importance of Stenotrophomonas maltophilia (SMA) as an etiologic frequently polyresistant pathogen in severe nosocomial infections has increased.

Methods: In our prospective study we evaluated the risk factors of nosocomial infections by SMA in our internal intensive care unit (ICU) over a one year period from July 1997 to June 1998.

Results: 111 patients (80 men, 31 women, mean age ± SD: 58,0 ± 13,3 years) were treated for more than 5 days in the ICU. SMA were cultured in 16/111 patients (13 men, three women, mean age 57,8 ± 3,4 years) out of bronchial secretions (68 %), sputum (19 %) and pleural fluid (13 %). Univariate analysis resulted in 15 different risk factors (p < 0.05); however, multivariate analysis provided three independent risk factors: chronic obstructive pulmonary disease (OR 95 % CI [1.91;∞]), length of stay in the ICU (OR 95 % CI [1.07;1.26]) and therapy with carbapenems before admittance to ICU (OR 95 % CI [0.56; 153]). Four of 16 patients died due to an SMA-infection, two by purulent exacerbations of a chronic bronchitis and two by sepsis. Molecular typing of 18 SMA isolates in 15 patients resulted in 9 different genetic types and a clonal dissemination could only be confirmed in three patients.

Conclusions: In respiratory ICU SMA infections are favored by severe COPD, length of stay in the ICU and by selection pressure of applicated antibiotics, especially carbapenems.

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