F. H. Van Tiel

Cross-colonisation with Pseudomonas aeruginosa of patients in an intensive care unit

BACKGROUND Ventilator-associated pneumonia (VAP) caused by Pseudomonas aeruginosa is usually preceded by colonisation of the respiratory tract. During outbreaks, colonisation with P aeruginosa is mainly derived from exogenous sources. The relative importance of different pathways of colonisation of P aeruginosa has rarely been determined in non-epidemic settings. METHODS In order to determine the importance of exogenous colonisation, all isolates of P aeruginosa obtained by surveillance and clinical cultures from two identical intensive care units (ICUs) were genotyped with pulsed field gel electrophoresis. RESULTS A total of 100 patients were studied, 44 in ICU 1 and 56 in ICU 2. Twenty three patients were colonised with P aeruginosa, seven at the start of the study or on admission and 16 of the remaining 93 patients became colonised during the study. Eight patients developed VAP due to P aeruginosa. The incidence of respiratory tract colonisation and VAP with P aeruginosa in our ICU was similar to that before and after the study period, and therefore represents an endemic situation. Genotyping of 118 isolates yielded 11 strain types: eight in one patient each, two in three patients each, and one type in eight patients. Based on chronological evaluation and genotypical identity of isolates, eight cases of cross-colonisation were identified. Eight (50%) of 16 episodes of acquired colonisation and two (25%) of eight cases of VAP due to P aeruginosa seemed to be the result of cross-colonisation. CONCLUSIONS Even in non-epidemic settings cross-colonisation seems to play an important part in the epidemiology of colonisation and infection with P aeruginosa.

Cost of the meticillin-resistant Staphylococcus aureus search and destroy policy in a Dutch university hospital

Costs related to a search and destroy policy and treatment for Staphylococcus aureus bacteraemia in the University Hospital Maastricht were calculated for the period 2000 and 2004. The financial cost-benefit break-even point of the search and destroy policy was determined by modelling. On average 22,412 patients were admitted per year for an average of 8.7 days. Each year 246 patients were screened for meticillin-resistant Staphylococcus aureus (MRSA) and 74 patients were decolonised and nursed in preventive isolation. The prevalence of MRSA in the University Hospital Maastricht was 0.7%, as calculated from positive blood cultures, and mean length of stay for all patients with S. aureus bloodstream infections was 39.9 days. The annual cost of pro-active searching for MRSA in the University Hospital Maastricht was euro 1,383,200, and euro 2,736,762 for MRSA prevention and treatment of S. aureus bloodstream infections. Simulation of a variety MRSA/meticillin-susceptible S. aureus (MSSA) ratios showed that even if the MRSA prevalence reaches 8%, prevention costs are still lower than the cost of treating S. aureus infections. In conclusion, the total cost of a search and destroy policy is lower than the cost of treating S. aureus bloodstream infections in the University Hospital Maastricht. At an MRSA prevalence of <or=8% the search and destroy policy remains cost-effective. From an economic point of view, the search and destroy policy is the best alternative at maintaining an endemic MRSA level at <1%.

Colonization and infection with Enterococcus faecalis in intensive care units: the role of antimicrobial agents.

We studied the influences of antimicrobial agents on the colonization of the respiratory tract and infection with Enterococcus faecalis in intensive care unit (ICU) patients receiving mechanical respiration for at least 3 days. In a matched-cohort analysis, patients receiving topical antimicrobial prophylaxis (TAP) of the oropharynx and stomach with antimicrobial agents not treating E. faecalis were compared with patients not receiving TAP. Patients were matched with controls on the basis of their duration in the ICU, their use of systemic antibiotics treating and not treating E. faecalis, the administration of TAP, their APACHE II score, and surgical procedures they had undergone. In all, 276 patients were analyzed. The colonization of the oropharynx and/or trachea by E. faecalis at admission was demonstrated for 43 patients (16%). Twenty patients (9%) acquired tracheal colonization and 91 patients (40%) acquired oropharyngeal colonization with E. faecalis. In the matched-cohort analysis, 43 patients receiving TAP were matched in two controls each. TAP patients more frequently acquired tracheal colonization (15 of 43 versus 2 of 86 patients, P < 0.00001) and infections with E. faecalis (6 of 43 versus 1 of 86 patients, P < 0.01). The use of topical antibiotics and treating E. faecalis increased the risk for colonization and infection with E. faecalis.

Colonization with Pseudomonas aeruginosa in patients developing ventilator-associated pneumonia.

To determine routes of colonization and genotypic variation of Pseudomonas aeruginosa leading to ventilator-associated pneumonia, colonization of the rectum, stomach, oropharynx, and trachea was studied chronologically in 10 patients. Ninety-one isolates of P aeruginosa were genotyped; seven different genotypes were identified. Patients developing ventilator-associated pneumonia caused by P aeruginosa were colonized at multiple body sites and may be colonized with multiple genotypes. The upper respiratory tract is the predominant initial site of colonization with P aeruginosa.

Value of phenotyping methods as an initial screening of Pseudomonas aeruginosa in epidemiologic studies.

SummaryWhen studying the epidemiology ofPseudomonas aeruginosa, determination of the similarity of isolates is crucial. In the present study the distinctive capacity of four phenotyping methods (antibiotic susceptibility patterns, serotyping, phage-typing and outer membrane protein [OMP] profile analysis) was determined and compared to pulsed-field gel electrophoresis (PFGE) of enzyme restricted chromosomal DNA. In all, 91 isolates ofP. aeruginosa were cultured from ten patients. Antibiotic susceptibility patterns were concordant for all isolates. Serotyping yielded five, phage-typing eight, OMP profile analysis nine and PFGE seven distinct types ofP. aeruginosa. Compared to PFGE, the distinctive capacities were 89% (81/91) for serotyping, 87% (79/91) for phage-typing, and 90% (82/91) for OMP profile analysis. When serotyping results were different, PFGE types also were different (exclusiveness 100%). However, isolates with the same serotype may have various PFGE patterns. In contrast, isolates with similar PFGE patterns could have different phage-types or OMP types. For the study of isolates ofP. aeruginosa, serotyping provides a good initial selection to reduce the number of isolates that need to be genotyped.

Topical antimicrobial prophylaxis of nosocomial pneumonia in mechanically ventilated patients. Microbiological observations

SummaryGenerally, reduction of colonization and infection with potentially pathogenic microorganisms in intensive care units (ICU) is attempted by a combination of antimicrobial agents administered topically in the digestive tract and systematically. We tested the efficacy of topical antimicrobial prophylaxis of the oropharynx and stomach administered in combination with sucralfate without systemic prophylaxis in 25 mechanically ventilated ICU patients. The regimen successfully reduced colonization with potentially pathogenic microorganisms in the oropharynx and trachea without modifying the intestinal flora. However, colonization and infections with gram-positive cocci and gram-negative rods other thanEnterobacteriaceae andPseudomonadaceae and resistant to one or both the antimicrobial agents used were observed.ZusammenfassungDurch topische Anwendung einer Kombination antimikrobieller Substanzen zur Dekontamination des Gastrointestinaltraktes und systemische Antibiotikagabe wird in Intensivstationen der Versuch einer Reduktion der Kolonisation und Infektion mit potentiell pathogenen Mikroorganismen gemacht. Wir prüften die Wirksamkeit einer topischen antimikrobiellen Prophylaxe des Oropharynx und des Magens in Kombination mit Sucralfat ohne systemische Prophylaxe bei 25 beatmeten Intensivpatienten. Durch diese Maßnahme wurde die Kolonisation des Oropharynx und der Trachea mit potentiell pathogenen Keimen reduziert; die Darmflora wurde dabei nicht verändert. Allerdings war eine Kolonisation verbunden mit Infektionen durch grampositive Kokken und gramnegative Stäbchen, die nicht denEnterobacteriaceae oderPseudomonadaceae angehörten, und die gegen eine oder beide der antimikrobiellen Substanzen resistent waren, zu beobachten.Generally, reduction of colonization and infection with potentially pathogenic microorganisms in intensive care units (ICU) is attempted by a combination of antimicrobial agents administered topically in the digestive tract and systematically. We tested the efficacy of topical antimicrobial prophylaxis of the oropharynx and stomach administered in combination with sucralfate without systemic prophylaxis in 25 mechanically ventilated ICU patients. The regimen successfully reduced colonization with potentially pathogenic microorganisms in the oropharynx and trachea without modifying the intestinal flora. However, colonization and infections with gram-positive cocci and gram-negative rods other thanEnterobacteriaceae andPseudomonadaceae and resistant to one or both the antimicrobial agents used were observed. Durch topische Anwendung einer Kombination antimikrobieller Substanzen zur Dekontamination des Gastrointestinaltraktes und systemische Antibiotikagabe wird in Intensivstationen der Versuch einer Reduktion der Kolonisation und Infektion mit potentiell pathogenen Mikroorganismen gemacht. Wir prüften die Wirksamkeit einer topischen antimikrobiellen Prophylaxe des Oropharynx und des Magens in Kombination mit Sucralfat ohne systemische Prophylaxe bei 25 beatmeten Intensivpatienten. Durch diese Maßnahme wurde die Kolonisation des Oropharynx und der Trachea mit potentiell pathogenen Keimen reduziert; die Darmflora wurde dabei nicht verändert. Allerdings war eine Kolonisation verbunden mit Infektionen durch grampositive Kokken und gramnegative Stäbchen, die nicht denEnterobacteriaceae oderPseudomonadaceae angehörten, und die gegen eine oder beide der antimikrobiellen Substanzen resistent waren, zu beobachten.

Genetic diversity of methicillin-resistant Staphylococcus aureus in a tertiary hospital in The Netherlands between 2002 and 2006

The aim of this study was to investigate the methicillin-resistant Staphylococcus aureus (MRSA) clones isolated in a Dutch university hospital, situated near the borders of Belgium and Germany, between 2002 and 2006. MRSA strains (n = 175) were characterized using spa and SCCmec typing. The presence of Panton Valentine leukocidin (PVL) was determined. Between 2002 and 2005, ST5-MRSA-IV was predominant, and the spa type of ST5-MRSA-IV changed from t002 to t447. ST5-MRSA-I, ST5-MRSA-II, ST228-MRSA-I, and ST247-MRSA-I were also observed in this period. From 2004, the MRSA genetic background became more diverse, and in 2006, ST5-MRSA-IV was only sporadically observed. From 2005, ST5-MRSA-II, ST8-MRSA-IV, ST22-MRSA-IV, and ST45-MRSA-IV were increasingly observed. Several other MRSA clones, such as ST239-MRSA-III, were found sporadically. Four PVL-positive MRSA isolates were observed, associated with ST80-MRSA-IV and ST8-MRSA-IV. ST5-MRSA-I, ST5-MRSA-II, ST5-MRSA-IV, and ST228-MRSA-I have not been described previously in The Netherlands.

In vitro antibacterial activity of sucralfate

The effect of sucralfate (12.5 mg/ml) on the growth ofEscherichia coli (ATCC 25922),Enterococcus faecalis (ATCC 29212) and two isolates ofPseudomonas aeruginosa (ATCC 27853 and a multi-resistant clinical isolate) was studied in vitro at pH values of 3.0, 4.5, 6.0 and 7.4. A bacteriostatic effect of sucralfate was demonstrated forPseudomonas aeruginosa at a pH of 6.0 and 7.4 and forEscherichia coli andEnterococcus faecalis at a pH of 6.0. The bacteriostatic effect was most pronounced at high pH values. Sucralfate had no bactericidal effect on the bacteria tested at the concentration used.

Clinical spectrum of ventilator-associated pneumonia caused by methicillin-sensitive Staphylococcus aureus

The incidence of tracheal colonization and its association with ventilator-associated pneumonia caused by methicillin-sensitiveStaphylococcus aureus (MSSA) was studied prospectively in 530 consecutively admitted mechanically ventilated patients in a general intensive care unit. Furthermore, the clinical spectrum, outcome, and microbiological results of 27 cases of staphylococcal ventilator-associated pneumonia (SVAP) were examined. Ventilator-associated pneumonia was diagnosed by protected specimen brush and/or bronchoalveolar lavage. On admission, 7% of the patients were colonized with MSSA in the trachea. Acquired tracheal colonization was demonstrated in 10% of the patients and occurred less frequently in patients with a hospital stay of > 48 h before ICU admission compared to patients admitted directly to the ICU (6% vs. 15%, p<0.001). Moreover, colonization was acquired more frequently among trauma and neurological/neurosurgical patients (22%) as compared to surgical and medical patients (7%) (p<0.0001). Twenty-one patients (4%) developed SVAP, the incidence being higher in patients colonized in the trachea with MSSA than in those not colonized (21 % vs. 1 %, p<0.00001). Staphylococcal ventilator-associated pneumonia developed more often in trauma and neurological/neurosurgical patients as compared to surgical and medical patients (8% vs. 3%, p<0.05). Moreover, patients with a hospital stay of < 48 h before admission to the ICU had a higher incidence of SVAP as compared to those with a longer hospital stay before ICU admission (7% vs. 2%, p<0.01). Crude infection-related mortality was 26%. Preceding colonization with MSSA in the trachea appears to be an important risk factor for the development of SVAP, and patients with a short duration of hospitalization before intensive care unit admission have the highest incidence of ventilator-associated pneumonia caused by MSSA.

Evidence for lectin-mediated adherence ofMoraxella catarrahlis

Clinical isolates ofMoraxella catarrhalis (n=86) were evaluated for their haemagglutinating activity with different types of erythrocytes. Of all the isolates tested, 12 did not agglutinate with any of the erythrocytes, whereas 65 reacted with human erythrocytes of type A, B, and 0, and 26 with erythrocytes from rabbit, guinea pig, dog, or rat. None of the isolates agglutinated with sheep and goat erythrocytes. The agglutination titres ranged from 0 to 64. Among these isolates, 13 different agglutination patterns could be distinguished. The agglutinating activity was Ca2+-dependent and was inhibited by proteases, by temperatures exceeding 50°C and by the addition of D-glucosamine or D-galactosamine. The adherence capacity of theM. catarrhalis isolates to tracheal epithelium correlated with their agglutination titre and could be inhibited by the same treatments. These data provide strong evidence that adherence ofM. catarrhalis is mediated by lectins located on the bacterial surface. 86 klinische Isolate vonMoraxella catarrhalis wurden auf ihre Fähigkeit zur Agglutination mit verschiedenen Erythrozytenarten geprüft. 12 der geprüften Isolate zeigten keinerlei Agglutination mit Erythrozyten. 65 reagierten mit menschlichen Erythrozyten der Blutgruppen A, B und 0 und 26 mit Erythrozyten von Kaninchen, Meerschweinchen, Hunden oder Ratten. Keines der Isolate agglutinierte Erythrozyten von Schafen oder Ziegen. Die Agglutinationstiter lagen in einem Bereich von 0–64. Die Isolate boten 13 verschiedene Agglutinationsmuster. Die Agglutinationsfähigkeit war abhängig von Ca++ und wurde durch Proteasen, Temperaturen über 50°C und die Zugabe von D-Glukosamin oder D-Galaktosamin gehemmt. Die Fähigkeit vonM. catarrhalis, sich an Trachealepithel anzuheften, korrelierte mit dem Agglutinationstiter und konnte durch dieselben Behandlungen gehemmt werden. Diese Daten bieten deutliche Hinweise dafür, daß die Adhärenz vonM. catarrhalis durch Lektine auf der Oberfläche der Bakterienzelle vermittelt wird.SummaryClinical isolates ofMoraxella catarrhalis (n=86) were evaluated for their haemagglutinating activity with different types of erythrocytes. Of all the isolates tested, 12 did not agglutinate with any of the erythrocytes, whereas 65 reacted with human erythrocytes of type A, B, and 0, and 26 with erythrocytes from rabbit, guinea pig, dog, or rat. None of the isolates agglutinated with sheep and goat erythrocytes. The agglutination titres ranged from 0 to 64. Among these isolates, 13 different agglutination patterns could be distinguished. The agglutinating activity was Ca2+-dependent and was inhibited by proteases, by temperatures exceeding 50°C and by the addition of D-glucosamine or D-galactosamine. The adherence capacity of theM. catarrhalis isolates to tracheal epithelium correlated with their agglutination titre and could be inhibited by the same treatments. These data provide strong evidence that adherence ofM. catarrhalis is mediated by lectins located on the bacterial surface.Zusammenfassung86 klinische Isolate vonMoraxella catarrhalis wurden auf ihre Fähigkeit zur Agglutination mit verschiedenen Erythrozytenarten geprüft. 12 der geprüften Isolate zeigten keinerlei Agglutination mit Erythrozyten. 65 reagierten mit menschlichen Erythrozyten der Blutgruppen A, B und 0 und 26 mit Erythrozyten von Kaninchen, Meerschweinchen, Hunden oder Ratten. Keines der Isolate agglutinierte Erythrozyten von Schafen oder Ziegen. Die Agglutinationstiter lagen in einem Bereich von 0–64. Die Isolate boten 13 verschiedene Agglutinationsmuster. Die Agglutinationsfähigkeit war abhängig von Ca++ und wurde durch Proteasen, Temperaturen über 50°C und die Zugabe von D-Glukosamin oder D-Galaktosamin gehemmt. Die Fähigkeit vonM. catarrhalis, sich an Trachealepithel anzuheften, korrelierte mit dem Agglutinationstiter und konnte durch dieselben Behandlungen gehemmt werden. Diese Daten bieten deutliche Hinweise dafür, daß die Adhärenz vonM. catarrhalis durch Lektine auf der Oberfläche der Bakterienzelle vermittelt wird.