Marisa Rivera

Contaminated feeding bottles: the source of an outbreak of Pseudomonas aeruginosa infections in a neonatal intensive care unit.

BACKGROUND Outbreaks of Pseudomonas aeruginosa have been reported in relationship with contamination of staff fingernails, hands, water baths, hand lotions and others. To our knowledge, contamination of milk and feeding bottles as a source of an outbreak of P aeruginosa infections has not been reported. The incidence of P aeruginosa infection/colonization in our neonatal intensive care unit increased from 1.9 per 1000 patient-days in August 2004 to 8.8 per 1000 patient-days in September 2004. METHODS Samples were collected including hand and body lotions, water from the incubator humidifying system, the health care worker hands, and the feeding bottle preparation room. Strains were epidemiologically characterized by pulsed-field gel electrophoresis of SpeI-digested genomic DNA. P aeruginosa was isolated from a total of 30 neonates during the period September 2004 to December 2004. RESULTS All cultures (139) of hand and body lotions, water from the incubator humidifying system, and hands of health care personnel were negative. Nine out of 48 samples collected from the feeding bottle preparation room were positive for P aeruginosa (6 samples of in-house prepared milk and 3 samples of water from dishwashers). Pulsed-field gel electrophoresis with SpeI showed that the strains isolated from neonates and from environmental samples were identical. Discontinuation of in-house preparation of feeding bottles and incorporation of unidose milk bottles stopped the outbreak. CONCLUSION The preparation and solution of milk from multidose powder preparation may be a source of P aeruginosa infections in a neonatal intensive care unit. The use of manufactured, nonmanipulated, unidose feeding bottles should be considered more adequate.

Rapid Detection of Staphylococcus aureus in Lower Respiratory Tract Secretions from Patients with Suspected Ventilator-Associated Pneumonia: Evaluation of the Cepheid Xpert MRSA/SA SSTI Assay

ABSTRACT A preclinical evaluation was conducted to evaluate the performance of the Cepheid Xpert assay on 135 lower respiratory tract secretions for detection of methicillin-resistant Staphylococcus aureus and S. aureus. Compared with the quantitative culture, the sensitivity, specificity, and positive and negative predictive values were 99.0%, 72.2%, 90.7%, and 96.3%, respectively.

Value of a single galactomannan determination (Platelia) for the diagnosis of invasive aspergillosis in non-hematological patients with clinical isolation of Aspergillus spp.

We studied 75 patients with non-hematological conditions from whom Aspergillus spp. were recovered from clinical specimens during the period March 2003 to August 2006. The patients were classified according to EORTC criteria and the presence of galactomannan (Platelia Aspergillus) in their sera was evaluated. Ten of these patients (13.3%) had proven or probable invasive aspergillosis, i.e., chronic obstructive pulmonary disease in five (50%), HIV infection in one (10%), lymphoma in one (10%), liver transplant in one (10%), solid malignancies in one (10%), and corticosteroid treatment in one (10%). The sensitivity, specificity, and positive and negative predictive values for the detection of galactomannan, using cut-offs of > or =0.5 ng/ml and > or =1 ng/ml were 60%/50%, 89.23%/100%, 46.15%/100%, and 93.55%/92.86% (p=0.001 and p<0.001), respectively. The determination of galactomannan in the sera of non-neutropenic patients could prove to be a useful microbiological finding when diagnosing invasive aspergillosis.

Are central venous catheter tip cultures reliable after 6-day refrigeration?

Present guidelines recommend culturing only central venous catheter (CVC) tips from patients with suspected catheter-related bloodstream infection (CR-BSI). However, a high proportion of these suspicions are not confirmed. Moreover, CVC tip culture increases laboratory workload, and reports of colonization may be meaningless or misleading for the clinician. Our working hypothesis was that CVC tips should be refrigerated and cultured only in patients with positive blood cultures. We evaluated the effect of 6-day refrigeration of 215 CVC tips. We selected all the catheters with a significant count according to the Makis roll-plate technique and randomly assigned them to 2 groups. In group A, the catheters were recultured after 24 h of refrigeration, and in group B, the catheters were recultured after 6 days more of refrigeration, so that the refrigeration time evaluated would be of 6 days. The yield of refrigerated CVC tips that grow significant colony counts of primary culture in group B was compared with the yield of refrigerated catheter tips in group A. The difference showed that 6-day refrigeration reduced the number of significant CVCs by 15.2%. Only 61 CVCs were obtained from patients with CR-BSI, and in most of them, blood cultures were already positive before CVC culture, so only 0.91% of the CR-BSI episodes would have been misdiagnosed as culture negative after refrigeration. Refrigeration of CVC tips sent for culture and culturing only those from patients with positive blood cultures reduce the workload in the microbiology laboratory without misdiagnosing CR-BSI.

Prevalence and patterns of HGV/GBV-C infection in patients with suspected HCV-related hepatitis

Hepatitis G virus (HGV) is a recently described hepatotropic parenterally transmitted flavivirus. The presence of HGV was tested in 61 patients with a request for confirmation of HCV active infection. Thirty-two patients were in haemodialysis and 29 were referred from wards other than nephrology. Active HCV and HGV infections were determined by detection of their viral RNA in serum. Evaluation of previous HGV infection was carried out by detection of antibodies to E2 antigen. HCV prevalence was 62.29% (38/61). HGV-active infection was found in 11.47% (7/61) of the population studied: in 18.7% (6/32) of the haemodialysed patients and in 3.4% (1/29) of patients belonging to the other group. HGV prevalence increased two-fold when previous infection was also considered. HGV clearance was prospectively detected in 5 out of the 7 patients with active infection, and at an earlier stage for those patients coinfected with HCV. Anti-E2 seropositivity was associated with HGV clearance in only two patients.

Applying undersampling to the nuclear magnetic resonance signal

Presents the use of undersampling in an NMR prototype equipment. The results show that undersampling is a convenient tool to be used in the processing of these signals. It allows one to easily transform bandpass free induction decay (FID) signals, centered at high frequencies, into lowpass signals or bandpass signals at much lower frequencies. The main advantages of using this technique are improved signal to noise ratio and analog electronic stages suppression.

A mini NMR imaging system for teaching and training

This work presents a mini NMR (Nuclear Magnetic Resonance) imaging system that has been developed for cost-effective bioengineering pre-graduate students teaching and training. It consists of a compact permanent magnet, an RF electronic modular system, a signal acquisition subsystem and a computer; all these parts can operate independently, allowing easy and intuitive manipulations. Manual interaction with each module is possible, although a computerised automatism can also be programmed. Being a completely open system, students can manipulate almost every parameter of an NMR signal acquisition, visualising in real time the different effects. The system has proved to be reliable enough to allow the implementation of several research experiments. To the authors best knowledge, there is no commercial system with these characteristics available on the market.