荧光定量PCR对血及痰培养物中结核分枝杆菌DNA的检测

目的 评价荧光定量PCR(FQ-PCR)检测血及痰培养物中结核分枝杆菌的临床价值.方法 81例临床诊断为结核病的痰涂片阴性患者中,单纯肺结核40例(肺结核组),合并HIV感染的患者41例(合并感染组).患者的血、痰样本分别进行结核分枝杆菌及其L型培养,采用FQ-PCR技术检测血及痰培养液中结核分枝杆菌DNA.结果 肺结核组结核分枝杆菌痰培养FQ-PCR阳性率为54.1%(20/37);血培养阳性率为27.5%(11/40),血培养FQ-PCR阳性率为22.5%(9/40),血培养及其FQ-PCR总阳性率42.5%(17/40).合并感染组10例痰样本培养后2例FQ-PCR阳性;血培养阳性率为7.3%(3/41),血培养FQ-PCR阳性率为17.1%(7/41).合并感染组血培养物FQ-PCR阳性率(17.1%)与肺结核组(22.5%)相比,差异无统计学意义(P>0.05).两组痰与血培养物FQ-PCR总阳性率分别为65.0%(26/40)和22.0%(9/41),差异有统计学意义(χ2=15.305,P<0.01).结论 痰或血培养物FQ-PCR检测有助于提高结核或结核合并艾滋病患者的诊断,同时显著提高了痰涂片阴性肺结核患者的诊断.     

A comparative study of blood culture sampling from umbilical catheter line versus peripheral site

Neonatal sepsis is an important cause of death and morbidity in newborns and is diagnosed by isolation of organism in blood culture. In several reports,reliability of blood cultures were done from umbilical catheters,have been demonstrated. The objective of the present study was to determine, wether an indewelling umbilical catheter, could be an alternative site for blood culture. In a prospective study over 6 months during 2006, 141 paired blood cultures from 134 infant,were done simultaneously from peripheral site and umbilical catheter (mostly U. V. C),during the first four days of life. Majority of these infants were preterm and admitted to NICU for special care. these infants had indwelling umbilical line and had indication of sepsis workup. A total of 141 pairs of blood cultures were obtained from 134 infants. In 16 infants blood culture pairs were positive for one organism in both peripheral vein and umbilical site. 71. 6% of total cultures (n=11) pairs were negative in both sites. A total of 22 pairs were positive in one site only,with 5 positive from peripheral vein only and the other 17 from umbilical site. Two pairs were positive in both sites with two different organism. In over all 16 infant (11%) of blood were considered to be contaminated. Contamination rate were 2. 4% and 9. 2% for peripheral and umbilical catheter site. Contamination rate increased after 48 hours of age in umbilical catheter. The result showed that after 2 days contamination rate for blood culture taken from catheter line increased and specificity decreased. We recommended that blood culture via umbilical catheter in first 2 days in sick neonates with indwelling catheter can be a alternate site of blood culture sampling.     

急性呼吸窘迫综合征早期肺循环细胞学和生化改变的初步研究

给大鼠静脉注射油酸制备实验性急性呼吸窘迫综合征（ＡＲＤＳ）模型。在ＡＲＤＳ发生的早期，用肺动脉导管（ＰＡＣ）从肺小动脉中动态取血，发现肺动脉（ＰＡ）血中白细胞（ＷＢＣ）和血管紧张素Ⅰ转换酶（ＡＣＥ）活性在注射油酸后很快升高，并与肺水肿、血氧分压（ＰａＯ２）有明显相关关系（Ｐ＜０．００１）；ＰＡ血中ＷＢＣ数与股动脉（ＦＡ）血中ＷＢＣ数无明显关系（Ｐ＞０．０５）；而ＰＡ血中ＡＣＥ活性与ＦＡ血中ＡＣＥ活性有明显相关关系（Ｐ＜０．００１）。结果表明，用外周血ＷＢＣ数不能反映肺内的改变；外周血中ＡＣＥ活性的变化可以用于估计肺损伤的情况，因此，对临床ＡＲＤＳ的早期诊断可能有重要的参考价值。     

Epidemic bacteremia due to Acinetobacter baumannii in five intensive care units

From March 5, 1986 to September 4, 1987, Acinetobacter baumannii (AB) was isolated from blood or vascular catheter-tip cultures of 75 patients in five intensive care units at a hospital in New Jersey. To identify risk factors for AB bacteremia in the intensive care units, a case-control study was conducted. Characteristics of 72 case-patients were compared with those of 37 controls. Case-patients were more likely than controls to have had peripheral arterial catheters (odds ratio (OR) = 7.0, p less than 0.001), mechanical ventilation (OR = 5.8, p less than 0.001), hyperalimentation (OR = 5.7, p less than 0.001), or pulmonary arterial catheters (OR = 3.9, p less than 0.001). Arterial catheters were used with reusable pressure transducers for intravascular pressure monitoring. A logistic regression analysis identified four independent risk factors: transducers, ventilation, hyperalimentation, and days of transducer use at an insertion site. The strongest influence on the risk of AB bacteremia was exerted by number of days of transducer usage. Cultures of 70 transducer diaphragms or domes, 42 in-use and 28 in-storage, were positive for AB in 21% and 46%, respectively. Plasmid analysis showed that patient blood cultures and transducer isolates were identical. Transducers were wiped with alcohol in the units between patient uses. Since reusable transducers appeared to be the source of this outbreak, it is recommended that reusable transducers receive either high level disinfection or sterilization between patient uses.     

分娩期短时输注少量葡萄糖液对胎儿血糖及血气的影响

目的:研究分娩期输液及母儿血糖对胎儿的影响。方法:分娩过程中分别给母亲输注5％GNS和0.9％NS后,比较母儿血糖、胎儿脐动脉血pH值及新生儿并发症的差异。结果:母亲血糖与脐静脉血糖、母儿血糖梯度均呈明显的正相关性,相关系数r分别为0.929和0.697;脐动脉血pH值与母亲血糖及与脐静脉血糖均存在明显的负相关性,相关系数r分别为-0.357及-0.347;两组的脐动脉血pH值、胎儿窘迫发生率及新生儿发病率无显著性差异,P>0.05。结论:分娩期持续缓慢地给母亲输注5％GNS或0.9％NS,对母儿血糖、脐动脉血pH值及新生儿预后的影响无明显差异,分娩期母儿血糖与脐动脉血pH值呈负相关。     

CK-19mRNA、CEAmRNA检测在肺癌围术期的应用及其意义

目的探讨肺血管处理顺序的选择对癌细胞入血的影响。方法收集56例手术治疗的非小细胞肺癌患者，术前随机分为2组，即：先结扎肺静脉组和先结扎肺动脉组；术前1d和术后第7天分别采集患者的外周静脉血，用巢氏PCR检测外周静脉血中CK-19mRNA、CEAmRNA的表达。结果术后患者外周静脉血中CK-19mRNA、CEAmRNA的表达低于术前，先结扎肺静脉组的患者术后外周血中CK-19mRNA、CEAmRNA表达的阳性率低于先结扎肺动脉组。结论手术操作影响癌细胞的入血。先结扎肺静脉可减少癌细胞入血。     

A prospective study of a new protocol for 'in situ' diagnosis of central venous catheter related bacteraemia

59 patients with suspected central venous catheter related bacteraemia (CRB), while receiving parenteral nutrition, were studied prospectively. 41 (Group 1) were managed conservatively: cultures were taken from the catheter hub lumen, skin at the catheter entry site and peripheral blood; the catheter was then heparinised and locked for 24-48 h. The catheter was withdrawn only if cultures were positive; otherwise parenteral nutrition was resumed. In 18 patients the catheter was immediately withdrawn (Group 2) and the same cultures plus tip culture were performed. 13 patients of Group 1 with positive hub or skin cultures, had their catheters removed and 12 had blood cultures matching for the same micro-organism. Negative skin and hub cultures had a negative predictive value for CRB of 96%. A positive hub culture had a 100% positive predictive value for CRB. CRB was diagnosed in 11 patients out of the 18 in whom catheters were withdrawn immediately (Group 2). Thus, 1 out of 41 catheters and 7 out of 18 catheters were removed unnecessarily in Groups 1 and 2 respectively (p = 0.001, Fisher's test). In all, 24 CRBs were documented and 15 were due to coagulase negative staphylococci. The catheter hub was the commonest origin of CRB followed by the infusate and the skin. In febrile patients on parenteral nutrition, negative skin and hub cultures accurately predict or rule out CRB and should be used more often to avoid withdrawal of sterile catheters.     

Alveolar sampling and fast kinetics of tetrachloroethene in man. I. Alveolar sampling

Human subjects were exposed to tetrachloroethene (perchloroethylene, PER). The duration of exposure ranged from one to 60 minutes and the concentration of PER in inhaled air ranged from 0.02 to 0.40 mmol/m3. Alveolar air was sampled after several residence times (t*) in the lung. Both during and after exposure, the concentration of PER in alveolar air (C Alv) as a function of the residence time was studied to estimate the concentration in the pulmonary artery (C Ven: mixed venous blood) and in the pulmonary vein (C Art: arterial blood). During exposure C Alv decreased as function of t*. At t* = 10 s C Alv was 70-75% of the value presented at t* = 5 s; this decrease approximates an exponential curve. C Alv seemed to stabilise at t* = 10-12 s, whereas it decreased more rapidly at t* greater than 12 s; this decrease continued up to at least t* = 55 s when C Alv was about 40% of the value it represented at t* = 5 s. In the postexposure period C Alv increased as function of t* from 5 to 10 s. Both during and after exposure, no difference was observed between C Alv at t* = 10 s and C Alv in the exhaled part of the expiratory reserve volume. A simple gas exchange model showed that the decrease or increase of C Alv at t* less than 10 s could be explained by either absorption or excretion by mixed venous blood. C Alv at t* = 10-12 s provided a valid estimate of C Ven. To estimate C Art, its fluctuating character due to the discontinuous breathing with a breathing frequency had to be taken into account. It is shown that C Alv during normal breathing (t* = 5 s) provides a reasonable estimate of the time weighted concentration in arterial blood.     

Alveolar sampling and fast kinetics of tetrachloroethene in man. I. Alveolar sampling.

Human subjects were exposed to tetrachloroethene (perchloroethylene, PER). The duration of exposure ranged from one to 60 minutes and the concentration of PER in inhaled air ranged from 0.02 to 0.40 mmol/m3. Alveolar air was sampled after several residence times (t*) in the lung. Both during and after exposure, the concentration of PER in alveolar air (C Alv) as a function of the residence time was studied to estimate the concentration in the pulmonary artery (C Ven: mixed venous blood) and in the pulmonary vein (C Art: arterial blood). During exposure C Alv decreased as function of t*. At t* = 10 s C Alv was 70-75% of the value presented at t* = 5 s; this decrease approximates an exponential curve. C Alv seemed to stabilise at t* = 10-12 s, whereas it decreased more rapidly at t* greater than 12 s; this decrease continued up to at least t* = 55 s when C Alv was about 40% of the value it represented at t* = 5 s. In the postexposure period C Alv increased as function of t* from 5 to 10 s. Both during and after exposure, no difference was observed between C Alv at t* = 10 s and C Alv in the exhaled part of the expiratory reserve volume. A simple gas exchange model showed that the decrease or increase of C Alv at t* less than 10 s could be explained by either absorption or excretion by mixed venous blood. C Alv at t* = 10-12 s provided a valid estimate of C Ven. To estimate C Art, its fluctuating character due to the discontinuous breathing with a breathing frequency had to be taken into account. It is shown that C Alv during normal breathing (t* = 5 s) provides a reasonable estimate of the time weighted concentration in arterial blood.     

肺动脉高压大鼠肺组织Notch信号的改变

目的探讨肺动脉高压（pulmonary hypertension，PH）大鼠肺组织Notch受体的改变。方法构建肺切除＋野百合碱PH大鼠模型，与正常大鼠比较肺血管重构指标的改变。进行肺组织免疫组化Notch 1-Notch4受体染色和实时荧光定量PCR（RT—PCR）检测（Notch 1-Notch4）mRNA。结果肺切除＋野百合碱组大鼠平均肺动脉压力（mPAP）、右心指数[fulton index，RV／（LV＋S）]、肺小动脉中膜厚度百分比（WT，％）、非肌性小动脉肌化程度、管壁细胞增殖度，明显高于正常大鼠，差异有显著意义（P〈0．05），有新生内膜形成。肺组织免疫组织化染色，肺切除＋野百合碱组和正常对照组大鼠肺动脉均有Notch1，Notch3，Notch4受体表达，未见Notch2受体表达。Notch1表达于血管内皮细胞和平滑肌细胞，Notch3主要表达于平滑肌细胞，Notch4主要表达于内皮细胞。肺切除＋野百合碱组肺组织（Notch1～Notch4）mRNA水平高于正常对照组。结论Notch1，Notch3，Notch4表达于肺动脉，随着PH肺血管重构的发生，表达上调。Notch信号很可能参与了PH肺血管重构过程。     

A cluster of pseudofungemia associated with hospital renovation adjacent to the microbiology laboratory.

OBJECTIVE: To determine the clinical significance and source of fungemia following a cluster of positive blood cultures during a 3-day period. DESIGN: Chart review was used to determine the clinical significance of positive blood cultures. Microbiologic sampling of the laboratory environment was used to determine potential sources of fungal contamination. SETTING: A large, tertiary care, community teaching hospital. PATIENTS: All patients with blood cultures positive for Aspergillus species, Penicillium species, or both during the outbreak period. RESULTS: Thirteen patients, all children, were reported to have positive blood cultures for fungus during a 3-day period in early 1990. None had clinical features consistent with fungemia. Investigation of specimen processing procedures revealed that microbiologic plates were not processed--as per protocol--under the biologic hood but inadvertently were left open to air on the work bench by laboratory technicians. Settling plates left at the workbench, at door entry sites, and at sites of renovation immediately adjacent to the laboratory were positive for Aspergillus and/or Penicillium; control plates placed elsewhere were negative. Airflow patterns suggested spread into the microbiologic laboratory through an open door located near the implicated workbench station and a false ceiling above the workbench area. CONCLUSIONS: Our investigation demonstrates that faulty technique in the laboratory coupled with a change in environmental conditions can result in false-positive cultures and an outbreak of pseudofungemia.     

Phlebotomy teams reduce blood-culture contamination rate and save money

OBJECTIVE: To determine the extent of resource utilization due to contaminated blood cultures. DESIGN: Case-control retrospective analysis. Twenty-three patients who had contaminated blood cultures were matched by age, underlying diseases, and discharge diagnoses with 23 patients who had negative blood cultures. SETTING: St Luke's Medical Center, a community teaching hospital in Cleveland, Ohio. The phlebotomy team was eliminated in November 1993 to reduce the costs. RESULTS: Blood cultures drawn by the phlebotomy team had a lower contamination rate compared with those drawn by nonphlebotomists (2.6% vs 5.6%). Patients with contaminated blood cultures were compared to those with negative blood cultures. The following parameters were found to be statistically significant: total hospital length of stay (LOS; 13.9 vs 5.5 days; P = .002), postculture LOS (8.9 vs 4.6; P = .01), postculture number of days on antibiotics (5.9 vs 2.9; P = .03), vancomycin use (9 vs 2 patients; P = .03), postculture cost of antibiotics ($762 vs $121; P = .004), and postculture hospital cost per patient ($10,515 vs $4,213; P = .001). CONCLUSIONS: This study demonstrated a substantial increase in resource utilization in our hospital due to contaminated blood cultures. The reinstitution of a phlebotomy team could be a cost-effective solution with savings between $950,000 and $1.5 million per year for our hospital.     

CARDIAC FUNCTION AFTER ALCOHOL INGESTION IN PATIENTS WITH ISCHEMIC HEART DISEASE AND CARDIOMYOPATHY: A CONTROLLED STUDY

Thirty male patients with ischemic heart disease and cardiomyopathyentered a controlled study of the acute effects of alcohol oncardiac function evaluated by right heart catheterization. Twentypatients, nine with angina pectoris and 11 with congestive heartfailure, were studied during alcohol intoxication, and ten patients,five with angina pectoris and five with heart failure, servedas a control group. The mean serum ethanol concentration inthe alcohol group was 93 mg/100 ml (S.D. 17). The systemic arterialblood pressure was reduced by 6% in the alcohol group, P<0.05compared with the control group. No significant changes occurredin the central venous pressure, the pulmonary artery pressure,the pulmonary capillary wedge pressure, or in cardiac output,stroke volume and total peripheral resistance. Alcohol intakein moderate doses has no measurable effect on pulmonary bloodpressures or cardiac output in patients with ischemic heartdisease and cardiomyopathy. Such an effect may, however, bemasked by a reduction of afterload.     

A new approach to the diagnosis of central venous catheter sepsis

One hundred forty-four cancer patients harboring a central venous catheter (CVC) were prospectively investigated to assess the relationship between hub culture, clinical assessment of sepsis before removal, and CVC sepsis. In 22 patients, the CVC was removed because of clinical assessment of catheter sepsis expressed by the staff prior to the removal. For each CVC removal, peripheral blood (qualitative method), hub, and CVC tip (quantitative method) cultures were performed. Clinical sepsis (disappearance of fever after CVC removal) was observed in 13 patients, microbiologic "sepsis" (identification of the same microorganisms on the CVC tip and in the peripheral blood) in seven patients, and clinical and/or microbiologic sepsis in 16 patients. Staphylococcus epidermidis was the microorganism most frequently identified. Hub culture was negative in 48% and positive for a low number and a high number of colonies in 35% and 17%, respectively. The predictive value of hub culture was 96% when testing negative and 8% and 37% (p = 3 x 10(-3)) when testing positive for a low and a high number of colonies, respectively. Predictive values of clinical assessment were 55% if positive and 97% if negative. Combining hub cultures and clinical assessment, the risk of sepsis varied from 2% with both evaluations negative to 89% in the case of positive clinical assessment associated with positive high-count hub. Inasmuch as the CVCs used have a disposable hub, it is possible to have an accurate diagnosis of CVC sepsis without removing the CVC.     

Lung anabolic activity in patients with chronic heart failure: Potential implications for clinical practice

ObjectiveThe proteins in the lungs are in constant flux, undergoing degradation and resynthesis. We investigated pulmonary protein and amino acid metabolism, the biochemical basis of the remodeling process, in individuals with chronic heart failure receiving or not receiving β-blocker therapy with bisoprolol (BIS).MethodsClinically stable rehabilitative patients with chronic heart failure, without metabolic diseases or liver/renal failure, and with a stable weight over the preceding 3 mo underwent right heart catheterization, and radial artery cannulation. Mixed central venous and arterial blood samples were drawn simultaneously to calculate the venous-arterial difference of amino acids (pulmonary uptake and release).ResultsTwenty-two patients on BIS therapy and eight not receiving BIS were analyzed. The two groups showed a net pulmonary protein synthesis (i.e., a positive value of phenylalanine [venous-arterial difference] × cardiac index product) and amino acid extraction, the rates of which were significantly lower in patients on BIS therapy. The two groups had pulmonary hypertension (mean pulmonary artery pressure >19 mmHg). Pulmonary vascular resistance was 57% higher in patients not receiving BIS than in those on BIS therapy (6.65 ± 2.90 versus 4.23 ± 1.49 mmHg/L · min^?1 · m^?2, P < 0.05). Pulmonary vascular resistance correlated positively with the pulmonary extraction of total essential amino acids (r = +0.4576, P = 0.01) and leucine (r = +0.5083, P = 0.004), the most important amino acid for protein synthesis.ConclusionPatients with chronic heart failure have increased rates of amino acid extraction and pulmonary protein synthesis, suggesting, at least in part, an increased rate of lung remodeling. Therapy with BIS attenuates lung metabolic abnormalities.     

Skin antiseptics in venous puncture-site disinfection for prevention of blood culture contamination: systematic review with meta-analysis

Blood cultures drawn by venous puncture are common clinical procedures for the detection of bacteraemia. Blood culture contamination (BCC) can lead to clinical misinterpretation and unnecessary expenses. We aimed to systematically review randomised controlled trials (RCTs) with skin antiseptics for prevention of contamination in venous-puncture drawn blood cultures. We conducted database search using CENTRAL (Cochrane Library issue April 2010), MEDLINE, EMBASE and mRCT, in June 2010. All RCTs testing skin antiseptics in venous-puncture drawn blood cultures were retrieved. Relative risk (RR) of the BCC outcome was analysed by random effects method using confidence interval (CI) of 95%. Studies were assessed by one review author and checked by another. Six studies were identified. Single-trial comparisons showed that alcoholic iodine tincture was better than non-alcoholic povidone-iodine, and isopropyl/acetone/povidone-iodine showed superiority against isopropyl/povidone-iodine. Meta-analysis demonstrated that alcoholic chlorhexidine was better than non-alcoholic povidone-iodine (RR: 0.33; 95% CI: 0.24-0.46) in 4757 blood cultures from two trials. Alcoholic solutions were better than non-alcoholic products (0.53; 0.31-0.90) in 21,300 blood cultures from four studies. Two trials with 13,418 blood cultures showed that iodine tincture was not superior to povidone-iodine in BCC prevention (0.79; 0.54-1.18). Alcoholic iodine was not different from non-alcoholic iodine (0.79; 0.53-1.17). Comparison of chlorhexidine vs iodine compounds was not conclusive. Alcohol alone was not inferior to iodinated products for prevention of contamination in venous-puncture drawn blood cultures. The association of alcohol and povidone-iodine did not seem to be useful. Alcoholic chlorhexidine solutions reduced blood culture false positives compared with aqueous povidone-iodine.     

The cardiopulmonary haemodynamic transition at birth is not different between male and female preterm lambs

Males born preterm are at greater risk of illness and death than females, principally due to respiratory disease. Much of the excess morbidity occurs within the first few hours of life. Therefore, the aim of the present study was to investigate whether or not differences in the cardiopulmonary transition soon after birth underlie the increased morbidity in males after preterm birth. Nine female and thirteen male lambs (128±2 days gestation) underwent surgery immediately before delivery for implantation of a pulmonary arterial flow-probe and catheters into the main pulmonary artery and a carotid artery. After birth lambs were ventilated for 30 min (tidal volume 7 mL kg(-1)) while anaesthetised. Arterial pressures and flows were recorded in real time and left-ventricular output measured using Doppler echocardiography. Before birth, fetal cardiopulmonary haemodynamics, arterial blood gases, pH, glucose and lactate did not differ between sexes. Similarly, in the neonatal period there were no significant differences in arterial blood gas status, ventilation parameters, respiratory indices or cardiopulmonary haemodynamics between the sexes. Our data show that the cardiopulmonary transition at birth in ventilated, anaesthetised preterm lambs is not influenced by sex. Thus, the neonatal 'male disadvantage' is not explained by an impaired cardiovascular transition at birth.     

Determining the significance of coagulase-negative staphylococci isolated from blood cultures at a community hospital: a role for species and strain identification.

OBJECTIVES: To determine the degree to which species identification or strain relatedness assessment of successive blood culture isolates of coagulase-negative staphylococci (CNS) may improve the clinical diagnosis of bloodstream infection (BSI). SETTING: 400-bed community hospital. DESIGN: Prospective laboratory survey during which all CNS blood culture isolates obtained between mid-August 1996 and mid-February 1997 (study period) were saved and later identified to the species level; selected isolates were genotyped using pulsed-field gel electrophoresis at the Centers for Disease Control and Prevention (CDC). Retrospective review of medical records of 37 patients with multiple cultures positive for CNS. RESULTS: During the study period, 171 patients had blood cultures positive for CNS; 130 had single positive cultures and 41 had > or =2 positive cultures. Of these 41, 23 (62%) were from patients with signs and symptoms of BSI according to CDC surveillance definitions. Species identification and strain clonality of CNS isolates from patients with > or =2 positives revealed 3 (13%) of the 23 patients did not have a consistent CNS species, and another 3 (13%) did not have a consistent genotype in the > or =2 positive cultures, suggesting that CNS from these patients probably were contaminants. Thus, species identification and strain clonality assessment reduced by 27% the number of patients with BSI diagnosed based on the presence of symptoms and > or =2 positive blood cultures. CONCLUSIONS: Routine species identification and selected strain genotyping of CNS may reduce the misinterpretation of probable contaminants among patients with > or =2 positive blood cultures.     

Bacterial contamination of intravenous cannula injection ports and stopcocks

A prospective clinical study was undertaken to analyse the routes of bacterial contamination in infusion therapy. The infusion system was equipped with two membrane filters (0.45 μm), one in the infusion line and the other on the side port. The series comprised 122 days of parenteral nutrition in 44 patients. Bacterial cultures were performed from filters, catheters, skin and blood. Fourteen per cent of the filters on the side port and 3% of those in the infusion line showed bacterial growth. No correlation was found between positive filter cultures and positive catheter tip or blood cultures. Thrombophlebitis occurred in 5% of the patients. The study has shown that side ports are a common route of bacterial contamination of infusion systems, more common than infusion fluids. It is recommended that side ports, if used, be equipped with a bacterial filter.     

Preventing nosocomial transmission of pulmonary tuberculosis: when may isolation be discontinued for patients with suspected tuberculosis?

OBJECTIVE: The Centers for Disease Control and Prevention and the American Thoracic Society recommend obtaining cultures of at least three sputum specimens for acid-fast bacilli (AFB) from patients in whom tuberculosis (TB) is suspected. On the basis of this, most hospitals isolate patients with suspected TB for 3 days or more until three smear (not culture) results are negative. Our objective was to evaluate the predictive value and sensitivity of these smears. DESIGN: Observational study. SETTING: Four urban medical centers. METHODS: The posttest probability of TB given sequential negative AFB smears from 274 patients isolated for suspected TB and the sensitivity of sequential AFB smears from 209 patients with positive results on culture for pulmonary TB were measured. RESULTS: The posttest probabilities of having TB given one, two, and three negative AFB smears were low: 1.1% (3 of 265; 95% confidence interval [CI95], 0.23% to 3.27%), 0.4% (1 of 262; CI95 0% to 2.1%), and 0% (0 of 260; CI95, 0% to 1.4%), respectively. Among the 209 patients with positive results on culture for pulmonary TB, 169 (81%) had an expectorated sputum specimen sent, of which 91 (54%) were positive for AFB. Forty (24%) of the 169 patients had a second expectorated sputum specimen sent after the results of the first specimen were negative; only 6 (15%) of these had positive AFB smears. None of the 10 patients in whom the first two expectorated sputum samples yielded an AFB smear without an organism had a third AFB smear that was positive. CONCLUSION: Unless there is high clinical suspicion of pulmonary TB in a specific patient, the use of three AFB smears on expectorated sputa is a rational approach to discontinuing isolation for patients with suspected TB.