How long should cerebrospinal fluid cultures be held to detect shunt infections? Clinical article.

OBJECT: Infections of CSF hardware may be indolent, and some patients have received antibiotic treatment for various reasons before CSF is obtained to check for a shunt infection. At present, there are few data in the literature to guide the decision as to how long to hold CSF specimens when attempting to diagnose hardware infections, and institutions vary in the duration at which cultures are considered "final." METHODS: The authors reviewed the microbiology data from CSF specimens obtained from shunts, ventriculostomies, reservoirs, and lumbar drains at their institution over a 36-month period to discover how long after collection cultures became positive. The authors also sought to discover whether this time was affected by prior treatment with antibiotics. RESULTS: Of 158 positive CSF specimens obtained from hardware, the time to recovery ranged between 1-10 days, with a mean of 3.02 days (SD 2.37 days, 95% CI 2.66-3.38 days). One hundred and twenty-seven positive specimens were associated with clinical infections, and approximately 25% of these grew organisms after > 3 days, with some as long as 10 days after specimens were obtained. The most common organisms grown from individual patients were coagulase-negative Staphylococcus spp (34 cultures), Propionibacterium spp (21), Bacillus spp (6), Pseudomonas aeruginosa (4), and Staphylococcus aureus (4 cultures). Mean and maximum days to recovery were different across species, with S. aureus showing the shortest and Propionibacterium spp showing the longest incubation times. There appeared to be no significant difference in the time to recovery between specimens obtained in patients who had received prior antibiotic treatment versus those who had not. CONCLUSIONS: A substantial number of positive CSF specimens obtained in patients with clinical infections grew bacteria after > 3 days, with some requiring as long as 10 days. Thus, a routine 10-day observation period for CSF specimens can be justified.

Bacterial contamination of cystic fibrosis clinics.

BACKGROUND: Respiratory pathogens from CF patients can contaminate inpatient settings, which may be associated with increased risk of patient-to-patient transmission. Few data are available that assess the rate of bacterial contamination of outpatient settings. We determined the frequency of contamination of CF clinics and the effectiveness of alcohol-based disinfectants in reducing hand carriage of bacterial pathogens. METHODS: We conducted a point prevalence survey and before-after trial in outpatient clinics at 7 CF centers. The study examined CF patients with positive respiratory cultures for Pseudomonas, Staphylococcus, Stenotrophomonas or Burkholderia species. Hand carriage and environmental contamination with respiratory pathogens were assessed during clinic visits (Part I) and the effectiveness of hand hygiene performed by CF patients (Part II) was determined using molecular typing of recovered isolates. RESULTS: In Part I (n=97), the contamination rate was 13.6%. Pseudomonas and S. aureus, including methicillin-resistant strains, were cultured from patients' hands (7%), the exam room air (8%), and less commonly, environmental surfaces (1%). In Part II (n=100), the hand carriage rate of pathogens was 13.5% and 4 participants without initial detection of pathogens had hand contamination when recultured at the end of the clinic visit. CONCLUSIONS: Respiratory pathogens from CF patients can contaminate their hands and the clinic environment, but the actual risk of patient-to-patient transmission in the outpatient setting remains difficult to quantify. These findings support several recommendations CF infection control recommendations including hand hygiene for staff and patients, contact precautions for certain pathogens, and disinfecting equipment and surfaces touched by patients and staff.

Experience with universal bacterial culturing to detect contamination of apheresis platelet units in a hospital transfusion service.

BACKGROUND: Bacterial contamination of platelet units poses one of the greatest risks of morbidity and mortality to platelet transfusion recipients. A routine culture of all units (WBC-reduced apheresis platelet units) was instituted on Day 2 over a 2-year period to reduce this risk. STUDY DESIGN AND METHODS: A sterile connecting device was used to attach a small transfer pack on the morning of Day 2 after collection, and 10 mL of the unit were transferred to the small bag. After disconnection from the unit, about half of this volume was transferred to an aerobic culture bottle of an automated bacterial detection system. Units were maintained in available inventory until and unless a report was received of growth in the sample. When available, the unit or a retained aliquot was recultured if the initial sample was positive. Units were held up to 2 days beyond their 5-day outdate and used for transfusion if no other suitable units were available to meet the clinical need or were evaluated with in vitro testing on Day 8. RESULTS: Of 2678 units cultured, 16 (0.6%) were positive on initial culture. Thirteen could be recultured, and all of these samples were negative. Shortly after the 2-year period of the study, two units (split from the same collection) were documented as growing coagulase-negative Staphylococci 12 hours after sampling. Units transfused on Day 6 or 7 (n = 40) yielded expected clinical responses, and CCI available on 21 cipients 10 to 60 minutes after transfusion demonstrated acceptable results (mean, 14,400 +/- 8800; median, 12,191; 90% > 7500). More than 96 percent of units tested on Day 8 had pH greater than 6.2 and continued to demonstrate swirling. CONCLUSIONS: Routine culturing of apheresis platelet units is feasible, can be accomplished with a low rate of false positivity, and can detect contaminated units. The cost of such a protocol could be mitigated with extension of the storage period, and clinical experience with units held for 6 or 7 days was satisfactory.