Triple lumen catheters for parenteral nutrition

We retrospectively reviewed the charts of 61 patients in whom a total of 101 triple lumen catheters (TLCs) were used for parenteral nutrition for a total of 1,512 days (mean 15 +/- 11 days). Patients were categorized as those having culture-negative TLC tips either with or without infection elsewhere (groups 1 and 2, respectively) and those with culture-positive TLC tips (group 3). Temperature, WBC, alkaline phosphatase value, and SGOT level were recorded one or two days before TLC removal (period 1) and one or two days or three to five days after TLC removal (periods 2 and 3, respectively). The incidence of catheter sepsis was 4%. Fourteen other tips were contaminated. Patients in group 1 remained afebrile during all three periods, and all tips removed were culture-negative. Removal of the TLC in groups 2 and 3 caused neither defervescence nor decreased WBC. We conclude that TLCs can be used for total parenteral nutrition with a low incidence of infection, that TLC tips need not be cultured in afebrile patients without other sources of infection, and that a TLC can be safely left in place so long as the patient is afebrile. However, the risk of infection or contamination is high for catheters left in place for more than two weeks.     

Has the presence or absence of Borrelia burgdorferi sensu lato as detected by skin culture any influence on the course of erythema migrans?

The aim of this prospective study was to compare epidemiological and clinical data in patients with a positive Borrelia burgdorferi sensu lato culture and culture-negative erythema migrans skin lesions. Of the 546 adult patients with erythema migrans seen at our institution in 1997 in whom a skin biopsy was performed and the specimen cultured for the presence of B. burgdorferi sensu lato, 235 (43%) had a positive and 311 (57%) a negative skin culture. More women than men were present in both groups and women were also significantly older than men. Tick bites resulting in culture-positive erythema migrans predominated in May (p = 0.012), while in August and September tick bites with subsequent culture-negative skin lesions were more common (p = 0.018 and 0.011, respectively). Similarly, erythema migrans lesions noticed by our patients in May were significantly more often Borrelia culture positive than negative (p = 0.004), while lesions appearing in October were significantly more often culture negative (p = 0.004). In addition to these seasonal differences, the comparison of the large number of Borrelia skin culture-positive and -negative patients with erythema migrans also revealed differences in several clinical parameters including a larger diameter of skin lesions in the culture-positive group (p = 0.007 at presentation, and p = 0.039 at registration, respectively), a lesser number of multiple skin lesions (7/235 versus 27/311, p = 0.006), and a lower frequency of signs/symptoms (p = 0.039) associated with erythema migrans lesions in culture-positive than in culture-negative patients. We have no plausible explanation for the majority of these rather unexpected findings. Of the 59 patients who, prior to biopsy, had received brief courses of antibiotics known to be effective in the treatment of erythema migrans, 12 (20.3%) were culture positive. As anticipated, the ratio of culture positivity in pretreated patients was significantly lower (p < 0.001) than in those without antecedent antibiotic therapy.     

Infection and peripheral venous catheterization

A prospective bacteriological and clinical study was carried out to determine the incidence of local and systemic infection associated with peripheral venous catheterization in a 630-bed general hospital with 24 hr intravenous team coverage. In all, 1,696 cannulas were obtained using standardized techniques and were cultured by a semiquantitative method on solid media. 41 cannulas (2.4%) yielded positive cultures (15 or more colonies). An additional 318 (18.8%) showed lesser growth indicative of contamination. No case of septicemia was encountered. Local signs of inflammation showed no correlation with positive cannula culture. The semiquantitative culture technique is easily performed and yields clear results. However, the upper limit for the number of colonies which should be regarded as contamination and criteria for phlebitis require further study. Although the infective risk of peripheral venous catheterization must not be ignored, an extremely low rate can be achieved with continuous IV team coverage and strict aseptic technique.     

Fibrin sheath enhances central venous catheter infection

OBJECTIVE: To determine whether fibrin-coated central venous catheters have a higher infection rate, and spawn more septic emboli, than uncoated catheters after exposure to bacteremia. DESIGN: Animal study comparing catheter infection and blood cultures of fibrin-coated and uncoated catheters exposed to bacteremia. SETTING: Animal laboratory. SUBJECTS: Adult male Sprague-Dawley rats. INTERVENTIONS: A total of 210 rats had catheters placed with the proximal end buried subcutaneously. Rats were divided into three groups: tail vein bacterial injection on day 0 (no fibrin group) or on day 10 (fibrin group), or no injection/saline injection (control, n = 40). Bacterial injections were 1 x 108 colony forming units of either Staphylococcus epidermidis (n = 100) or Enterobacter cloacae (n = 60). Animals were killed 3 days after injection. Blood cultures were obtained via cardiac puncture, and catheters were removed via the chest. Half of the catheter was rolled onto agar and the other half was placed in trypticase soy broth. Plates and broth were incubated at 37 degrees C for 48 hrs. The presence of >15 colonies on roll plates, or growth in broth, was accepted as a positive sign of infection. Microscopy was performed on day 20-10 catheters. Thirty animals without catheters had bacterial injections and underwent blood culture 3 days after injection. MEASUREMENTS AND MAIN RESULTS: Catheter infection with S. epidermidis occurred in 32% of roll plates and 80% of broth from the fibrin group vs. 4% and 20% from the no fibrin group (p <.01 for each). Catheter infection with E. cloacae occurred in 50% of roll plates and 80% of broth from the fibrin group vs. 0% and 12% from the no fibrin group (p <.01 for each). Positive blood cultures occurred in 47 of 68 animals from the fibrin group vs. 8 of 68 from the no fibrin group (p <.01). Microscopy showed a fibrin sheath on 20 of 20 catheters. Without catheters, 30 of 30 blood cultures were negative. CONCLUSION: The fibrin sheath significantly enhanced catheter-related infection and persistent bacteremia.     

Characteristics and outcomes of culture-negative versus culture-positive severe sepsis

Introduction

Culture-negative sepsis is a common but relatively understudied condition. The aim of this study was to compare the characteristics and outcomes of culture-negative versus culture-positive severe sepsis.

Methods

This was a prospective observational cohort study of 1001 patients who were admitted to the medical intensive care unit (ICU) of a university hospital from 2004 to 2009 with severe sepsis. Patients with documented fungal, viral, and parasitic infections were excluded.

Results

There were 415 culture-negative patients (41.5%) and 586 culture-positive patients (58.5%). Gram-positive bacteria were isolated in 257 patients, and gram-negative bacteria in 390 patients. Culture-negative patients were more often women and had fewer comorbidities, less tachycardia, higher blood pressure, lower procalcitonin levels, lower Acute Physiology and Chronic Health Evaluation II (median 25.0 (interquartile range 19.0 to 32.0) versus 27.0 (21.0 to 33.0), P = 0.001) and Sequential Organ Failure Assessment scores, less cardiovascular, central nervous system, and coagulation failures, and less need for vasoactive agents than culture-positive patients. The lungs were a more common site of infection, while urinary tract, soft tissue and skin infections, infective endocarditis and primary bacteremia were less common in culture-negative than in culture-positive patients. Culture-negative patients had a shorter duration of hospital stay (12 days (7.0 to 21.0) versus 15.0 (7.0 to27.0), P = 0.02) and lower ICU mortality than culture-positive patients. Hospital mortality was lower in the culture-negative group (35.9%) than in the culture-positive group (44.0%, P = 0.01), the culture-positive subgroup, which received early appropriate antibiotics (41.9%, P = 0.11), and the culture-positive subgroup, which did not (55.5%, P < 0.001). After adjusting for covariates, culture positivity was not independently associated with mortality on multivariable analysis.

Conclusions

Significant differences between culture-negative and culture-positive sepsis are identified, with the former group having fewer comorbidities, milder severity of illness, shorter hospitalizations, and lower mortality.     

Prospective study of catheter-related infection during prolonged arterial catheterization

Ninety-six arterial catheters from 75 different anatomical sites in 56 surgical ICU patients were studied prospectively to determine the rate of catheter-related infection associated with prolonged arterial catheterization (defined as greater than 96 h). Every 96 h, all catheters were semiquantitatively (SQ) cultured and the percutaneous entry site was swab cultured. Sites were used indefinitely by exchanging the catheters over a guide-wire every 96 h as long as arterial monitoring was necessary and SQ cultures remained negative (less than or equal to 15 colonies). No sites used less than 96 h developed skin colonization, while 14/51 (27%) sites used greater than 96 h developed positive swab cultures. No SQ cultures were positive in sites with negative swab cultures (p less than .001). Catheter-related infection (a positive SQ culture) developed in 4/42 (9.5%) radial or femoral sites compared to 4/9 (44%) axillary sites used greater than 96 h (p less than .01). It is concluded that arterial catheter-related infection develops in less than 10% of radial or femoral sites used greater than 96 h, and 90% of radial and femoral sites may be used safely for prolonged periods if skin colonization at the percutaneous sites is controlled and SQ catheter cultures remain negative. Skin site swab cultures may be useful for determining when arterial catheters should be removed and SQ cultured.     

Culture results of heart valves resected because of streptococcal endocarditis: insights into duration of treatment to achieve valve sterilization

OBJECTIVES: To analyse the culture results of heart valves removed following streptococcal endocarditis in order to gain insight into the duration of treatment required for valve sterilization. PATIENTS AND METHODS: Retrospective review of 131 episodes of streptococcal endocarditis: 94 due to alpha-haemolytic streptococci; 15 due to beta-haemolytic streptococci; 10 due to nutritionally deficient streptococci; eight due to the Streptococcus anginosus group and four due to Streptococcus pneumoniae. Patients had their valves removed during antimicrobial treatment. Culture results were analysed with respect to duration of treatment before surgery. RESULTS: For alpha-haemolytic streptococci, 17 (18%) valves were culture-positive and 77 (82%) culture-negative after a median (range) of 4 (1-20) and 16 (4-58) days of treatment, respectively, P < 0.001. For beta-haemolytic streptococci, two valves (13%) were culture-positive; both patients had received < or = 4 days of treatment. Four patients (40%) with nutritionally deficient streptococci were culture-positive, and had received < or = 8 days of treatment. For the S. anginosus group, two valves (25%) were culture-positive; both patients had received < or = 4 days of treatment before operation. Overall, only one of 131 (0.8%) valves was culture-positive after 14 days of treatment. All valves infected with beta-haemolytic streptococci, nutritionally deficient streptococci and the S. anginosus group, who were treated for more than 8 days before surgery, were culture-negative. CONCLUSIONS: Our findings support current treatment guidelines for endocarditis caused by alpha-haemolytic streptococci. We suggest that the recommended duration of treatment for endocarditis resulting from other streptococci may be excessive and treatment trials evaluating 2 and 4 week regimens are justified.     

初次治疗菌阳肺结核与菌阴肺结核的MSCT影像比较

目的：探讨未经治疗的菌阳肺结核与未经治疗的菌阴肺结核的MSCT影像的异同。材料与方法：回顾性分析560例肺结核的MSCT扫描图像,其中菌阳肺结核240例,菌阴肺结核320例。结果-菌阳肺结核一般表现为病灶密度较低,边缘模糊常见,空洞较菌阴肺结核明显为多,菌阴肺结核一般表现为条索影、斑块状阴影、钙化等硬化灶,但也有部分与菌阳肺结核极为相似。结论：菌阳肺结核和菌阴肺结核各有其影像学特点,二者之间有一定的鉴别点。     

PCR-monitoring of gastric juice obtained with the capsuled string for the evaluation of H. pylori eradication

We have developed a highly sensitive semi-nested PCR assay, URA-PCR, for the detection of H. pylori ureA gene in gastric juice. The primers were designed according to nucleotide sequence analyses of clinical isolates. The PCR assay has higher sensitivity than conventional methods such as culture. Characteristics of culture-negative but PCR-positive patients were similar to those of culture-positive ones. The PCR assay, using gastric juice samples obtained with capsuled strings, detected 97% cases of relapsed infection within eight weeks after antimicrobial therapy.     

Streptococcus pneumoniae in nasopharyngeal secretions of healthy children: comparison of real-time PCR and culture from STGG-transport medium

Precise methods for the detection of Streptococcus pneumoniae are needed for predicting the consequences of pneumococcal conjugate vaccines on nasopharyngeal carriage. In this study, 400 nasopharyngeal swab samples from children were analyzed using a real-time pneumolysin (ply)-PCR method. The specimens were originally collected into STGG-transport medium and cultured in 1999, after which they were stored at -80 degrees C until analyzed by real-time PCR in 2001. The sensitivities of real-time PCR and culture methods were also studied by analyzing 10-fold dilutions of a pneumococcal broth culture using both methods. Of the 400 nasopharyngeal swab samples, 158 (40%) were positive in culture and 276 (69%) by real-time PCR. A minor part (4%) of the culture-positive samples remained negative by PCR. There was a trend between the quantity of genome equivalents detected by PCR and the number of colonies found in culture. When analyzing 10-fold dilutions of a pneumococcal broth culture, a higher number of genome equivalents were detected using real-time PCR than the number of colonies detected by culture. Quantitative real-time PCR provides feasible means for quantifying pneumococcal carriage. Further studies are needed to confirm that positive PCR findings really indicate the presence of viable pneumococcus in nasopharyngeal specimens.     

Are anaerobic bacteria involved in peripheral vein catheter associated thrombophlebitis?

While thrombophlebitis is a common complication of intravenous therapy, infection has been shown to be a cause of this problem in only a minority of cases. However, the methodology employed in the past would not have detected the anaerobes as a cause of this problem. As anaerobes are associated with thrombophlebitis in situations such as septic pelvic thrombophlebitis, we undertook a study to see if they might also be involved in thrombophlebitis associated with peripheral vein catheters. We prospectively studied 26 episodes of peripheral intravenous catheter associated thrombophlebitis. These catheters were all cultured under aerobic conditions by the semiquantitative technique on blood agar plates. In addition, they were promptly processed and cultured under optimal anaerobic conditions. In none of the episodes of thrombophlebitis were the catheters positive on semiquantitative culture. In addition, we did not show the presence of anaerobes on any of these catheters. We conclude that there is no evidence that anaerobes are associated with peripheral vein thrombophlebitis.     

Infectious and mechanical complications of central venous catheters placed by percutaneous venipuncture and over guidewires.

OBJECTIVE: To compare the frequency of infectious and mechanical complications of central venous and pulmonary artery catheters placed by initial venipuncture vs. over a guidewire at existing sites. HYPOTHESIS: Exchange of central venous catheters and pulmonary artery catheters over a guidewire as opposed to fresh venipuncture reduces mechanical complications without increasing risk of infection. DESIGN: Chart audit. PATIENTS: Medical, surgical, and coronary ICU patients requiring invasive monitoring or central venous access. INTERVENTIONS: Patients requiring prolonged catheterization underwent periodic exchange of catheters over a guidewire. Rates of catheter-related infections and mechanical complications were determined for central venous catheters placed by initial venipuncture and those catheters placed by guidewire exchange. MEASUREMENTS AND MAIN RESULTS: Over a 12-month period, 939 catheters were inserted in 454 patients. Of these 939 catheters, 534 were placed by guidewire exchange. Use of a guidewire was associated with a decreased frequency of pneumothorax and hemothorax compared with initial venipuncture (0/405 [0%] vs. 7/534 [1.3%], respectively; p < .05) but not with increased risk of infection (9/405 [2.2%] vs. 14/534 [2.6%], respectively; NS). Guidewire-facilitated replacement of multiple consecutive catheters at the same site did not increase the risk of catheter-related infection. Catheters placed via internal jugular veins were more likely to become infected than catheters placed via subclavian veins (17/477 [3.6%] vs. 3/430 [0.7%], respectively; p < .01). CONCLUSIONS: When prolonged central venous or pulmonary artery catheterization is necessary, periodic catheter replacement over a guidewire is associated with fewer mechanical complications than initial venipuncture. Periodic catheter replacement over a guidewire is also associated with no increase in risk of infection.     

In situ diagnosis of intravascular catheter-related bloodstream infection: a comparison of quantitative culture, differential time to positivity, and endoluminal brushing

OBJECTIVE: To compare the accuracy of three techniques that do not require central venous catheter removal to diagnose catheter-related bloodstream infection. DESIGN: Prospective cohort study of central venous catheters from suspected cases of catheter-related bloodstream infection. SETTING: University teaching hospital. PATIENTS: One hundred and twenty-five central venous catheters from patients with suspected catheter-related bloodstream infection (a raised peripheral white blood cell count, temperature >37 degrees C, and/or local signs of infection at the catheter skin entry site) in intensive care and surgical patients in a large teaching hospital were assessed. INTERVENTIONS: None. MEASUREMENTS: Three techniques were compared: the differential time to positivity of central venous catheter vs. peripheral-blood cultures, quantitative culture of central venous catheter vs. peripheral blood, and the endoluminal brush with peripheral blood culture. MAIN RESULTS: Central venous catheters with a median dwell time of 11 days were examined. There were 36 episodes of catheter-related bloodstream infection, defined as a positive result from at least two of the three tests in the presence of a peripheral blood culture growing the same microorganism and without an identifiable alternative source of sepsis. The sensitivities of the endoluminal brush, quantitative culture, and differential time to positivity techniques were 100%, 89%, and 72%, respectively, with corresponding specificities of 89%, 97%, and 95%. Blood could be directly aspirated from only 231 of 312 (74%) lumens. In the 20 cases of catheter-related bloodstream infection associated with multiple-lumen central venous catheters, endoluminal brushing was positive for one, two, and three lumens in nine (45%), six (30%), and five (25%) cases, respectively. CONCLUSIONS: All three techniques had relatively high sensitivity. However, inability to obtain samples via central venous catheters is a major drawback of the differential time to positivity and quantitative blood culture approaches. Differential time to positivity is simple to perform and has high specificity and therefore could be used as a first line approach, with the endoluminal brush reserved for cases where blood cannot be obtained. All lumens of multiple-lumen central venous catheters must be sampled to ensure maximal sensitivity.     

Performance Comparison of GeneXpert MTB/RIF and ProbeTec ET Tests for Rapid Molecular Diagnosis of Extrapulmonary Tuberculosis in a Low TB/MDR-TB Incidence Country

ObjectiveThis study evaluated the performance of GeneXpert MTB/RIF (Xpert) and ProbeTec ET (PTec-ET) assays in diagnosing extrapulmonary tuberculosis (EPTB) in Kuwait.Materials and MethodsWe tested nonrespiratory clinical specimens (n = 3,995) collected from 3,995 patients suspected to have EPTB. These included cavitary fluids (n = 2,054), fine-needle aspirate (FNA)/pus/tissue biopsy (n = 1,461), urine (n = 302), cerebrospinal fluid (CSF, n = 118), and others (n = 60). All specimens were processed for acid-fast bacilli (AFB), culture in mycobacteria growth indicator tube 960 system, and nucleic acid detection by Xpert and PTec-ET according to manufacturer''s instructions.ResultsOf 3,995 specimens, 95 were AFB-positive, 403 were culture-positive, and an additional 86 samples had histopathology suggestive of TB. Using culture as reference, the sensitivity and specificity values were 88.33 and 97.3% for Xpert and 72.95 and 97.80% for PTec-ET, respectively. Although performance of both tests was comparable in AFB-positive samples, Xpert detected significantly more cases in culture-positive samples. Among culture-negative samples, Xpert detected 18 more cases including 16 with histopathological evidence of TB. Lowest positivity was detected for both tests in cavitary fluids. Xpert performed better than PTec-ET in culture-positive FNA/pus/tissue biopsy and CSF samples.ConclusionsAlthough performance of both tests was suboptimal for AFB-negative/culture-positive samples, Xpert performed better than PTec-ET and also detected more cases of AFB-negative/culture-negative/histopathology-positive samples. PTec-ET was positive in 3, while Xpert was positive in all 6 culture-positive CSF specimens for rapid diagnosis of TB meningitis. Xpert was thus superior to PTec-ET or smear microscopy in rapid diagnosis of EPTB.     

Incidence of infection related to arterial catheterization in children: a prospective study

The incidence of infection related to arterial catheterization has not been studied in critically ill children, using systematic catheter cultures. We studied prospectively 68 children in whom 70 arterial catheters were inserted. After the aseptic catheterization procedure, no component of the system was changed. The insertion site was inspected daily for signs of inflammation. Upon removal, catheters were cultured using a semiquantitative method. Blood and infusion fluid specimens were also cultured if septicemia was clinically suspected. Mean duration of catheterization was 59 +/- 6 (SE) h. In our series, all catheter and infusion fluid cultures were negative. Local inflammation was not predictive of catheter tip infection and correlated poorly with duration of catheterization (r = 0.2). In our experience, the incidence of infection related to arterial catheterization is low. Routine change of infusion fluid, tubing, dressing and insertion site as well as systematic catheter culture in the absence of fever appears unwarranted.     

Use of lactophenol cotton blue mounts of corneal scrapings as an aid to the diagnosis of mycotic keratitis.

Lactophenol cotton blue (LPCB) mounts of corneal ulcer scrapings were assessed as a diagnostic tool in cases of mycotic keratitis over a period of 15 months. We investigated 568 cases of ulcerative keratitis by microbiological techniques consisting of direct microscopic examination of LPCB mounts and Gram-stained smears as well as culture of material scraped from the ulcer. Fungi were isolated in large numbers on multiple media from the corneal scrapings of 179 patients (culture-proven mycotic keratitis). Direct microscopic examination of LPCB mounts of corneal scrapings yielded positive results in 140 (78%) of 179 culture-positive patients and negative results in 371 (95%) of 389 culture-negative patients. There was a significant difference between the percentage of positive results obtained by LPCB mounts and by Gram-stained smears in the culture-positive cases. The LPCB mount was positive in greater than 80% of cases of keratitis due to Fusarium spp. and Aspergillus spp. The LPCB mount is strongly recommended as a simple, rapid, inexpensive, and sensitive diagnostic technique in cases of mycotic keratitis.     

Quantitative tip culture methods and the diagnosis of central venous catheter-related infections.

The diagnostic usefulness of two quantitative catheter culture methods was compared in a prospective study of central venous arterial catheters. The roll-plate method followed by sonication was used to culture 177 catheters from 85 patients, and the sonication method was used to culture 136 catheters from 68 patients. All patients were evaluated for catheter-related infections. Catheter-related infections were associated with greater than or equal to 100 colony-forming units (CFU) isolated from catheter tips by either roll plate (p = 0.01) or sonication (p less than 0.001). The sensitivity, specificity, and positive and negative predictive values of greater than or equal to 10(3) CFU by roll plate for catheter-related septicemia were 56%, 97%, 63%, and 96% compared with 93%, 95%, 76%, and 99%, respectively, for the same level by sonication. For central venous and arterial catheters, the sonication method can distinguish infection from contamination and is superior to the roll-plate method in that it may offer a more sensitive and predictive alternative in the diagnosis of catheter-related septicemia.     

Comparison of quantitative polymerase chain reaction,acid fast bacilli smear,and culture results in patients receiving therapy for pulmonary tuberculosis

Quantitative-competitive polymerase chain reaction (QPCR) was performed on serial sputum samples from 22 consecutive cases of acid fast bacilli (AFB) smear-positive pulmonary tuberculosis. Of 94 specimens, 55, 72, and 83% were positive by culture, AFB smear, and QPCR, respectively. Of 52 culture-positive specimens, 6% were negative by PCR, and 13% were negative by AFB smear. Of 42 culture-negative specimens, AFB smear and QPCR were positive in 55 and 61%, respectively. AFB smear and QPCR results were strongly correlated (r = 0.75, p < 0.001), but each correlated less strongly with culture (r = 0.54, p < 0.005 for smear and r = 0.52, p < 0.005 for QPCR). When patients were classified by microbiologic response, responders tended to have less DNA in their sputum and shorter time to a negative PCR result compared to nonresponders. These data do not suggest a great advantage of QPCR over AFB smear for predicting culture results in patients with pulmonary tuberculosis.     

The challenge of anticipating catheter tip colonization in major heart surgery patients in the intensive care unit: are surface cultures useful?

OBJECTIVE: Patients undergoing heart surgery show a high risk of catheter colonization and catheter-related bloodstream infections. We evaluated whether skin insertion site and catheter hub surveillance cultures ("surface cultures") could predict catheter colonization and help establish the origin of bloodstream infections. DESIGN:: Prospective cohort study. SETTING: An 11-bed heart surgery intensive care unit in a tertiary university hospital. PATIENTS: Heart surgery patients spending >4 days in intensive care over an 11-month period. INTERVENTIONS: All catheters were surveyed. Cultures were obtained from the skin insertion site and all hubs on day 5 after surgery, every 72 hrs thereafter, and on catheter removal. Swabs were processed semiquantitatively by streaking the surface of a Columbia agar plate. Catheters were processed using Maki's method. The observation of > or = 15 colonies/plate was taken to indicate a positive skin or catheter colonization culture result. MEASUREMENTS AND MAIN RESULTS: Over the study period, 561 catheters were inserted in 130 patients. The median time a catheter was in place was 6 days (interquartile range 3-11), and 3,712 surface cultures were obtained (median four per patient). Catheter colonization occurred in 133 catheters, and there were 15 episodes of catheter-related bloodstream infection (incidence density of colonization 29.3 and of catheter-related bloodstream infection 8.8 per 1,000 catheter-days). Validity indexes for the capacity of surface cultures to predict catheter colonization and catheter-related bloodstream infection, respectively, were as follows: accuracy, 71.4, 65.6; sensitivity, 83.5%, 100%; specificity, 67.1%, 64.7%; positive predictive value, 47.6%, 7.2%; negative predictive value, 91.9%, 100%; positive likelihood ratio, 2.5, 2.83; and negative likelihood ratio, 0.2, 0. Surface cultures correctly predicted 77.4% of all bacteremia episodes (catheter-related and non-catheter-related). CONCLUSIONS: Systematic surveillance cultures of catheter hub and skin insertion sites in patients admitted to a heart surgery intensive care unit could help identify patients who would benefit from decontamination and preventive measures and establish whether catheters are the portal of entry of bloodstream infection.     

Isolation of pneumococcal DNA from nasopharyngeal samples for real-time, quantitative PCR: comparison of three methods.

BACKGROUND: Real-time PCR is a useful method for detecting and quantifying bacterial DNA in clinical samples. DNA extraction is a crucial step when performing quantitative PCR. METHODS: We compared three methods, QIAamp. The use of tradenames is for product identification purposes only and does not imply endorsement. DNA Mini kit, MagNAPure trade mark LC DNA Isolation Kit II together with PickPen trade mark magnetic particle transfer device, and KingFisher genomic DNA purification Kit with KingFisher mL instrument, for purification of Streptococcus pneumoniae DNA from 50 nasopharyngeal swab samples, collected into skim milk-tryptone-glucose-glycerin medium. Pneumococcal DNA was detected and quantified by real-time PCR and results were compared to culture findings. RESULTS: The 22 (44%) pneumococcal culture-positive specimens were all positive by PCR regardless of DNA extraction method used, except that one KingFisher-extracted sample was positive only when repeatedly tested. Additionally, 71%, 57%, and 82% of the culture-negative samples were positive by real-time PCR when DNA was extracted by QIAamp, MagNAPure-PickPen, and KingFisher methods, respectively. The number of genome equivalents detected by real-time PCR varied, but was mainly low in culture-negative samples. The sensitivities of culture and real-time PCR were hence compared by analyzing different dilutions of a pneumococcal suspension. Real-time PCR detected significantly higher numbers of genome equivalents than the numbers of bacteria detected by culture. CONCLUSIONS: The results indicate that the DNA extraction method used for quantitative PCR should be evaluated and that real-time PCR is more sensitive than bacterial culture for detecting pneumococcus in nasopharyngeal swab samples.