Heterogeneity of hemolysin expression during neonatal Streptococcus agalactiae sepsis.

The beta-hemolysin of Streptococcus agalactiae is a major virulence factor; consequently, nonhemolytic strains rarely cause infections. We report on a case of neonatal sepsis caused by a strain displaying heterogeneous hemolysin expression. It was detected by the simultaneous isolation of hemolytic and nonhemolytic colonies from cultures of the infant's blood.

Rapid identification of Fusobacterium nucleatum and Fusobacterium necrophorum by fluorescence in situ hybridization.

Identification of clinically relevant Fusobacterium spp. is hampered by their slow growth, their frequent occurrence in polymicrobial culture, and the low reliability of biochemical differentiation methods. A newly developed fluorescence in situ hybridization (FISH) assay allowed reliable and rapid identification of Fusobacterium necrophorum and Fusobacterium nucleatum from culture. Preliminary results show that the method offers the perspective for direct detection of these pathogens in blood cultures and abscess aspirates.

Rapid detection of Brucella spp. in blood cultures by fluorescence in situ hybridization.

Brucellosis is a severe systemic disease in humans. We describe a new 16S rRNA-based fluorescence in situ hybridization assay that facilitates rapid and specific detection of all human pathogenic species of Brucella and that can be applied directly to positive blood cultures.

Superiority of molecular techniques for identification of gram-negative, oxidase-positive rods, including morphologically nontypical Pseudomonas aeruginosa, from patients with cystic fibrosis.

Phenotypic identification of gram-negative bacteria from Cystic Fibrosis (CF) patients carries a high risk of misidentification. Therefore, we compared the results of biochemical identification by API 20NE with 16S rRNA gene sequencing in 88 gram-negative, oxidase-positive rods, other than morphologically and biochemically typical P. aeruginosa, from respiratory secretions of CF patients. The API 20NE allowed correct identification of the bacterial species in 15 out of 88 (17%) isolates investigated. Agreement between the API and the 16S rRNA gene sequencing results was high only in isolates with an API result classified as "excellent identification". Even API results classified as "very good identification" or "good identification" showed a high rate of misidentification (67% and 84%). Fifty-two isolates of morphological and biochemical nontypical Pseudomonas aeruginosa, representing 59% of all isolates investigated, were not identifiable or misidentified in the API 20NE. Therefore, rapid molecular diagnostic techniques like real-time PCR and fluorescence in situ hybridization (FISH) were evaluated in this particular group of bacteria for identification of the clinically most relevant pathogen, P. aeruginosa. The LightCycler PCR assay with a P. aeruginosa-specific probe showed a sensitivity and specificity of 98.1% and 100%, respectively. For FISH analysis, a newly designed P. aeruginosa-specific probe had a sensitivity and specificity of 100%. In conclusion, molecular methods are superior over biochemical tests for identification of gram-negative, oxidase-positive rods in CF patients. In addition, real-time PCR and FISH allowed identification of morphologically nontypical isolates of P. aeruginosa within a few hours.

Impact of fluoroquinolone prophylaxis on reduced infection-related mortality among patients with neutropenia and hematologic malignancies.

BACKGROUND: Fluoroquinolone prophylaxis during neutropenia in patients with cancer has been associated with decreased incidence of gram-negative bacteremia. Bacterial antimicrobial resistance is likely to cause a progressive lack of efficacy of fluoroquinolones, but no convincing evidence from clinicoepidemiologic observations has proved this hypothesis. METHODS: This prospective observational study assessed the impact of discontinuing fluoroquinolone prophylaxis on the incidences of fever and bacteremia and on mortality among patients with neutropenia, after chemotherapy for hematologic malignancies. RESULTS: After a 12-month baseline period of levofloxacin prophylaxis, a period of discontinuation of fluoroquinolone prophylaxis was planned but was stopped prematurely after 9 neutropenic episodes over 3 weeks, because the mortality rate (33.3%) was higher than that with routine fluoroquinolone prophylaxis (2.9%) (odds ratio [OR], 16.6; 95% confidence interval [CI], 3.6-77.2). Fewer patients had gram-negative bacteremia during the baseline period (4.8%; n=15) than during the discontinuation period (44.4%; n=4) (OR, 16.9; 95% CI, 4.1-70.0). After levofloxacin therapy was reintroduced, the incidence of gram-negative bacteremia and the mortality rate were comparable to those during the first period. Escherichia coli isolated during the discontinuation period was susceptible to levofloxacin in vitro, whereas all E. coli isolates isolated during both prophylaxis periods were resistant. Bloodstream infections were caused by a single agent when the patient had received levofloxacin prophylaxis, whereas most cases of gram-negative bacteremia were polymicrobial after discontinuation. CONCLUSIONS: These findings suggest that, despite increasing rates of antimicrobial resistance, levofloxacin prophylaxis during neutropenia may have a beneficial impact on morbidity and infection-related mortality. Continued monitoring of the rate of gram-negative bacteremia is warranted for timely detection of the loss of efficacy of fluoroquinolone prophylaxis.

Analysis of transmission pathways of Pseudomonas aeruginosa between patients and tap water outlets.

OBJECTIVE: To study the association between infection and faucet contamination in a surgical intensive care unit (SICU). DESIGN: Prospective cohort study. SETTING: One SICU and 12 peripheral wards. PATIENTS: From 45 patients colonized or infected with P. aeruginosa, 87 positive isolates were collected. INTERVENTIONS: P. aeruginosa also was found in 150 of 259 (58%) tap water samples taken from patient rooms. MEASUREMENTS AND MAIN RESULTS: Clonal relationships between patient and tap water isolates were established by random amplification of polymorphic DNA-polymerase chain reaction. A long-time contamination (144 wks) with a single specific genotype for each of the faucets in our SICU was observed. Additional genotypes found in tap water from these faucets were only isolated over short periods of time. P. aeruginosa was shown to reside in single faucets and did not originate from the supplying mains. In 15 of 45 patients (33%), P. aeruginosa genotypes were identical to those from the faucets in the patient rooms. In six other patients, the same genotype was found in faucets from neighboring rooms. Faucets served as the source of infection for patients in 35% of cases, and on the other hand a retrograde contamination of faucets by patients was observed in 15% of cases. CONCLUSIONS: Tap water from faucets contaminated with P. aeruginosa plays an important role in the propagation of this pathogen among patients. A high number of transmissions were shown to occur both from faucet to patient and from patient to faucet. Our SICU served as an epicenter for the spread of P. aeruginosa to peripheral wards. It appears prudent to follow strict hygienic precautions such as wearing gloves and performing thorough alcoholic rub disinfection of hands after patient care and after hand washing at locations known to harbor.