间日疟对HIV感染者/AIDS患者CD4淋巴细胞凋亡率的影响

目的观察急性间日疟对HIV感染者CD4淋巴细胞凋亡(百分)率的影响,探讨疟疾疗法治疗HIV感染的部分机理.方法 12例HIV-1感染者(CD4细胞计数基线水平范围为1217×106/L～15×106/L)接受疟疾疗法(治疗性急性间日疟)治疗,用流式细胞仪碘化丙啶染色法检测CD4细胞凋亡率.另选20例年龄相配的HIV阴性志愿者作为对照组.结果 CD4细胞凋亡率在疟疾期显著升高,但在终止疟疾后迅速下降至低于疟疾疗法前的基线水平(HIV感染者/AIDS患者组的CD4细胞凋亡率在疟疾疗法前显著高于HIV阴性对照组,但在终止疟疾后两组无显著性差异).结论疟疾疗法治疗HIV感染的部分机理是减少CD4细胞的凋亡.     

疟疾疗法对HIV感染者安全性及不良反应

目的　观察疟疾疗法 (急性血源间日疟 )治疗人免疫缺陷病毒 (HIV)感染的不良反应或并发症 ,探索疟疾疗法治疗HIV阳性患者的安全操作程序。方法　 2 0例HIV阳性患者 (CD4细胞计数基线水平范围为 186 8～ 15× 10 6/L)接受疟疾疗法 ,经 10～ 2 0次疟疾阵发后用氯喹治愈疟疾。于疟疾前、疟疾期和终止疟疾后 10d观察临床表现并做相关的实验室检查。结果　血源间日疟的临床潜伏期为 5～ 17d。所有患者均有每日或隔日的疟疾发热发作 ,均有疟原虫血症。在疟疾期 ,肝和脾肿大分别占 4 / 2 0和 15 / 2 0 ,轻到中度贫血者占 19/ 2 0 ,血小板减少占 6 / 2 0 (但均无出血的表现 ) ,血清丙氨酸转氨酶 (ALT)升高占 2 / 2 0 ,只有在疟疾发热时卡氏 (Karnofsky)评分的分值降低 ,所有这些表现均在终止疟疾后消失或恢复。 1例晚期获得性免疫缺陷综合征 (AIDS)患者经疟疾疗法治疗后机会性感染消失。结论　疟疾疗法治疗HIV/AIDS的不良反应短暂而有限 ,在改善患者免疫指标的同时不导致严重的不良反应或并发症     

疟疾疗法治疗HIV感染的适应症

目的探讨疟疾疗法治疗HIV感染的适应症.方法按美国疾病控制中心(CDC)1993年修订的分类标准选择12例HIV-1感染者接受疟疾疗法治疗,其中5例诊断为CDCⅠ类(CD4细胞计数≥500×106/L),5例CDCⅡ类(CD4细胞计数200～499×106/L),2例CDCⅢ类(CD4细胞计数＜200×106/L).用流式细胞仪法检测CD4细胞计数和百分率,bDNA法检测病毒载量.分别于治疗前第1次和第2次、第1次疟疾发热、第5次发热、第10次发热、终止疟疾后第10天、1个月、3个月、6个月、12个月、18个月和24个月采集血标本做检测.结果病毒载量在所有CDCⅠ类和Ⅱ类患者于疟疾期均升高,在大部分Ⅰ类和所有Ⅱ类患者于终止疟疾后回降到治疗前基线水平;2例CDCⅢ类患者经疟疾疗法治疗后病毒载量升高.治疗后3～24个月期间,Ⅰ类患者CD4计数均降低,CD4百分率3例降低,2例升高;Ⅱ类患者CD4计数3例升高,2例维持稳定,CD4百分率4例升高,1例维持稳定;2例Ⅲ类患者CD4计数和百分率维持相对稳定不变.结论疟疾疗法可能对CDCⅡ类HIV感染者有疗效.应该选CDCⅡ类患者做Ⅱ期(设对照组)临床试验,以进一步验证其疗效.     

静脉吸毒人群HIV感染者CD+3 CD+4 CD+8 T淋巴细胞定量研究与分析

目的　定量分析静脉吸毒人群艾滋病病毒 (HIV)感染者CD+ 3 、CD+ 4 、CD+ 8T淋巴细胞水平。方法　采用流式细胞技术 (FCM) ,对 76例无症状抗 HIV阳性的静脉吸毒者 ,16 5例抗 HIV阴性的静脉吸毒者及 6 1名正常对照 ,分别检测CD+ 3 、CD+ 4 、CD+ 8T淋巴细胞绝对计数和CD+ 4 /CD+ 8比值。结果　HIV感染组与静脉吸毒组及正常对照组各项指标间差异有非常显著的统计学意义 (F =10 5 0 2、15 9 13、2 2 0 0 8,P均 <0 0 1) ;CD+ 4 细胞计数和CD+ 4 /CD+ 8比值表现为HIV感染组 <静脉吸毒组 <正常对照组 (q =18 4、2 4 6、11 1,P均 <0 0 1) ,CD+ 3 细胞计数呈现为HIV感染组 >健康对照组 >静脉吸毒组 (q=19 8、6 5、10 8,P均 <0 0 1) ,CD+ 8细胞计数表现为HIV感染组 >静脉吸毒组 >健康对照组 (q=2 7 2、2 4 9,P均 <0 0 1;q =3 4 8,P均 <0 0 5 )。结论　HIV感染和 /或静脉吸毒均可不同程度的导致CD+ 4 和CD+ 8细胞水平的改变 ,有关静脉吸毒合并HIV感染对免疫细胞水平的影响尚需进一步深入研究。     

人类免疫缺陷病毒感染者CD4+T淋巴细胞计数与结核分枝杆菌共感染的相关性

目的 探讨HIV合并结核分枝杆菌感染患者外周血CD4+T淋巴细胞的变化及其对酶联免疫斑点试验(ELISPOT)的影响.方法 应用结核酶联免疫斑点试验(T-SPOT.TB)对云南省和上海地区193例明确诊断的HIV感染者的血标本进行结核分枝杆菌特异性T淋巴细胞检测,同时应用流式细胞仪检测外周血CD4+T淋巴细胞计数,采用t检验进行统计学分析.结果 HIV感染者中潜伏性结核发生率达30.6％.HIV合并活动性结核患者的外周血CD4+T淋巴细胞计数平均值为190×106/L,显著低于HIV合并潜伏性结核组的484×106/L(t=6.665,P＜0.01).根据CD4+T淋巴细胞计数＞500×106/L、200×106～500×106/L、＜200×106/L进行分层分析发现,活动性结核组和潜伏性结核组构成比依次为1∶16.2、1∶1.3、5.6∶1.79例T-SPOT.TB阳性的病例中,共有20例HIV合并活动性结核患者,其中14例患者CD4+T淋巴细胞计数平均值＜200×106/L,5例为200×106/L～500×106/L,1例＞500×106/L.59例潜伏性结核患者中,52例CD4+T淋巴细胞计数＞200×106/L.结论 我国HIV感染人群中有较高的潜伏性结核发生率,HIV合并活动性结核患者的总体细胞免疫应答功能严重受损,随着CD4ˉT淋巴细胞计数的下降,HIV患者合并的潜伏性结核更易进展为活动性结核.当CD4+T淋巴细胞＜200×106/L时,对T-SPOT.TB检测结果可能有影响.     

人类免疫缺陷病毒合并结核分枝杆菌感染者的抗结核细胞免疫功能

目的 评价HIV合并结核分枝杆菌潜伏感染或合并活动性结核患者的抗结核细胞免疫功能.方法 应用早期分泌性抗原靶蛋白(ESAT)-6和培养滤出蛋白(CFP)-10诱导的结核酶联免疫斑点法对云南地区100例明确诊断的HIV感染者的血液标本进行结核分枝杆菌特异性T淋巴细胞检测,同时应用流式细胞仪检测外周血CD3+CD4+T淋巴细胞和CD3+CD8+T淋巴细胞的绝对计数水平.采用Mann-Whitney检验进行非参数统计分析.结果临床上无活动性结核感染证据的HIV感染者中合并结核分枝杆菌潜伏感染的感染率高达67.6%.HIV合并结核分枝杆菌潜伏感染者的外周血CD3+CD4+T淋巴细胞(532×106/L)和CD3+CD8+T淋巴细胞(473×106/L)绝对计数与单纯HIV感染者(406×106/L和504 × 106/L)相比,差异无统计学意义.HIV合并活动性结核感染者的外周血CD3+CD4+T淋巴细胞绝对计数平均值为189 × 106/L,CD3+CD8+T淋巴细胞绝对计数平均值为293×106/L,均显著低于单纯HIV合并结核潜伏感染组和HIV组(U=168.0,U=163.0;U=147.0,U=374.0;均P<0.01).HIV合并活动性结核感染者的ESAT-6和CFP-10抗原特异性斑点形成细胞数(31/106细胞和82/106细胞)显著低于HIV合并结核分枝杆菌潜伏感染者(92/106细胞和109/106细胞.U=507.0,U=529.5,均P<0.01).结论 我国无活动性结核临床证据的HIV感染人群中有较高的结核潜伏感染率,HIV合并活动性结核感染者的总体细胞免疫应答功能及特异性抗结核免疫应答功能均严重受损.     

人免疫缺陷病毒抗体阴性与阳性者播散性马尔尼菲青霉菌病的临床及实验室特征

目的 比较人免疫缺陷病毒(HIV)抗体阴性与阳性者播散性马尔尼菲青霉菌病(PSM)临床及实验室特征.方法 回顾性分析广西医科大学第一附属医院2002年3月至2007年3月确诊的33例PSM患者的临床资料.将33例分为HIV抗体阳性组:22例,男18例,女4例,年龄9～60岁,平均(39.5±4.4)岁;HIV抗体阴性组:11例,男8例,女3例,年龄(2～66岁),平均(45.1±4.6)岁.比较分析两组患者的特点.结果 两组患者均以体力劳动者为主,临床均表现发热及多器官功能损害,以发热、肺部、皮肤、消化系统损害和淋巴结肿大为主,预后差.两组比较,有明显区别:(1)HIV抗体阴性组病程(中位数为180 d)较HIV抗体阳性组(45 d)长,前者表现为慢性起病,后者多为急性或亚急性起病;HIV抗体阴性组11例中合并其他基础疾病5例,误诊7例;HIV抗体阳性组未见.(2)HIV抗体阳性组持续高热、呼吸困难出现早,以皮肤软疣样损伤为突出表现;HIV抗体阴性组间歇性反复发热,皮下结节或脓肿明显,而浅表淋巴结肿大(10/11)、骨痛(5/11)、胸痛(7/11)者较HIV抗体阳性组更突出(10/22、2/22、0/22).(3)HIV抗体阴性组白细胞总数增高多见(9例),而HIV抗体阳性组正常(15例)或降低(7例),且白细胞总数、中性粒细胞与淋巴细胞计数HIV抗体阴性组(中位数为18.6×109/L、14.24×109/L、2.08×109/L)高于HIV抗体阳性组(中佗数为4.71×109/L、4.16×109/L、0.42 x 109/L).(4)HIV抗体阴性患者CD4/CD8＞0.5,HIV抗体阳性患者低于0.5;(5)HIV抗体阳性组马尔尼菲青霉菌血培养18例均阳性,骨髓培养20例中14例阳性,HIV抗体阴性组分别为7/10例和2/8例.(6)两组胸部影像检查表现为广泛多样的实质性或间质性病变,HIV抗体阴性组常出现高密度实变影及胸膜炎表现,溶骨现象仅见于HIV抗体阴性组(4例).(7)HIV抗体阴性组临床症状好转7例,恶化及死亡各2例,而HIV抗体阳性组分别为8例、12例及2例.结论 两组均以发热、多器官功能损害及预后差为共同特征,但两组在基础疾病、发病症状、病程经过及血白细胞计数等方面有明显区别,提爪免疫状况影响两组患者的临床表现及疗效.     

HIV急性期/早期感染者合并HBV感染的临床特征

目的探讨艾滋病病毒(HIV)急性期/早期感染者合并感染乙型肝炎病毒(HBV)的临床特点及实验室特征,进一步明确影响HIV/HBV重叠感染疾病进展的关键因素。方法采用回顾性分析的方法,了解单独HIV急性期/早期感染者(单独HIV感染组)和合并HBV的HIV急性期/早期感染者(HIV/HBV重叠感染组)的初始CD+4T淋巴细胞(简称CD4细胞)计数和病毒载量调定点,以及两组病人感染HIV一年内CD4细胞计数和HIV病毒载量的动态变化,和HIV急性期/早期合并HBV感染的临床特征。结果 20例HIV/HBV重叠感染组的初始CD4细胞计数平均值为(443.55±197.00)个/μL(213~985个/μL),病毒载量调定点(4.34±0.99)Log10拷贝/mL(1.82~5.47Log10拷贝/mL)。30例单独HIV感染组病人的初始CD4细胞计数平均值为(497.37±121.29)个/μL(196~792个/μL),病毒载量调定点(3.87±0.62)Log10拷贝/mL(2.77~5.19Log10拷贝/mL)。HIV/HBV重叠感染组的初始CD4细胞计数明显低于单独HIV感染组,两组比较差异有统计学意义(P0.05)。HIV/HBV重叠感染组的病毒载量调定点明显高于单独HIV感染组,两组间差异有统计学意义(P0.05)。结论在我国HIV急性期/早期感染者中,HIV/HBV重叠感染者与单独HIV感染者比较,初始CD4细胞计数明显降低,病毒载量调定点明显升高,HIV病毒复制更为活跃。     

初发HIV感染男性病人静息心率及QTc间期分析

目的分析初发艾滋病病毒(HIV)感染男性病人的12导联心电图中静息心率及QTc间期特点。方法收集首都医科大学附属北京地坛医院初次确诊的HIV抗体阳性的男性病人,并选取男性健康志愿者为对照组,应用12导联心电图检查,比较组间静息心率、QRS间期及QTc间期的差异,并按CD4+T淋巴细胞(简称CD4细胞)计数水平分级,按HIV病毒载量水平分组,比较组间静息心率、QRS间期及QTc间期的差异。结果共纳入病例组病人及健康对照组各154例,其中QTc间期延长病例组17例(11.04%),对照组2例(1.30%),两组比较差异无统计学意义(P 0.05);病例组静息心率(83.81±14.13)bpm较对照组的静息心率(72.08±7.42)bpm明显增加(P 0.05);病例组亚组中,静息心率随CD4细胞计数的减少而增加,CD4细胞200个/μL组病人的静息心率(88.53±16.78)bpm高于CD4细胞200～500个/μL组病人的静息心率(82.14±13.12)bpm(P 0.05);病例组亚组中,QTc间期随HIV核糖核酸(RNA)载量的升高而延长,HIV RNA载量 5拷贝/mL组病人的QTc间期(418.29±17.96)ms较HIV RNA载量4拷贝/mL组病人的QTc间期(407.41±23.29)ms延长(P 0.05)。结论初发HIV感染男性病人的静息心率较健康男性增加,QTc间期较健康男性无明显延长,免疫功能水平低下时静息心率增加,高HIV RNA载量时QTc间期延长。     

干细胞移植后合并巨细胞病毒感染时淋巴细胞亚群变化

目的　研究异基因外周血干细胞移植 (PBSCT)后早期巨细胞病毒 (CMV)活动性感染时淋巴细胞亚群变化及其意义 ,探讨活动性CMV感染对免疫的影响。方法　根据CMV感染情况 ,将 2 7例早期PBSCT受者分为症状性感染、无症状活动性感染以及同期未出现活动性感染 3组 ,5 1例正常人作为对照组 ,用流式细胞仪测定其淋巴细胞表面CD3 、CD4、CD8、CD16、CD56、CD19、CD2 8的表达 ,比较各组间的差异。结果　PBSCT后早期CD+ 4 T和B细胞数量显著低于正常人 (P值均 <0 0 1) ;2 7例受者中无活动性CMV感染 5例、无症状活动性CMV感染 10例和症状性CMV感染 12例。上述 3组病人的平均CD+ 4 T细胞计数 (× 10 6/L)分别为 32 8± 2 0 3、2 39± 2 18和 199± 92 ;CD+ 8T细胞计数 (× 10 6/L)分别为 4 0 0± 380、2 6 7± 2 0 6和 6 0 3± 4 6 1;CD+ 4 CD+ 2 8的功能细胞亚群的比例分别为 (89 2± 8 9) %、(84 2±10 1) %和 (6 3 5± 11 4 ) % ;自然杀伤 (NK)细胞比例分别为 (16 2± 11 1) %、(2 9 3± 9 9) %和 (19 2±10 2 ) %。与无活动性CMV感染者相比 ,无症状CMV活动性感染者除NK细胞升高外 (P <0 0 1) ,其他指标差异无显著性 ;而症状性CMV感染者和无症状CMV感染者相比 ,其CD+ 4 T细胞数量显著减少(P <0 0 1) ,CD+ 8T     

The immunoneuroendocrine role of melatonin

Abstract: A tight, physiological link between the pineal gland and the immune system is emerging from a series of experimental studies. This link might reflect the evolutionary connection between self-recognition and reproduction. Pinealectomy or other experimental methods which inhibit melatonin synthesis and secretion induce a state of immunodepression which is counteracted by melatonin. In general, melatonin seems to have an immunoenhancing effect that is particularly apparent in immunodepressive states. The negative effect of acute stress or immunosuppressive pharmacological treatments on various immune parameters are counteracted by melatonin. It seems important to note that one of the main targets of melatonin is the thymus, i.e., the central organ of the immune system. The clinical use of melatonin as an immunotherapeutic agent seems promising in primary and secondary immunodeficiencies as well as in cancer immunotherapy. The immunoenhancing action of melatonin seems to be mediated by T-helper cell-derived opioid peptides as well as by lymphokines and, perhaps, by pituitary hormones. Melatonin-induced-immuno-opioids (MHO) and lymphokines imply the presence of specific binding sites or melatonin receptors on cells of the immune system. On the other hand, lymphokines such as -γ-interferon and interleukin-2 as well as thymic hormones can modulate the synthesis of melatonin in the pineal gland. The pineal gland might thus be viewed as the crux of a sophisticated immunoneuroendocrine network which functions as an unconscious, diffuse sensory organ.     

Changes in connexin43, the gap junction protein of astrocytes, during development of the rat pineal gland

Abstract: The abundance of gap junctions between rat pineal astrocytes formed by connexin43 (Cx43) was studied during development. Levels and distribution of Cx43 were measured by immunoblotting and indirect immunofluorescence, respectively. The amount of Cx43 in cells located within the gland was low until about the 7th postnatal day and increased to adult values between the 14th and 21st days postpartum. Although astrocytes, recognized by their vimentin immunoreactivity, were scarce before birth, they were abundant by the 7th postnatal day suggesting that the low levels of Cx43 found at this age corresponded to a low expression of this protein. Localization of the immunoreactivity to Cx43 and vimentin showed a close correlation, indicating that mature or immature pineal astrocytes form gap junctions made of Cx43. Since Cx43 levels attained their adult values at about the time the innervation and the functional state of the gland reached maturity (2–3 weeks after birth), it is proposed that astrocyte gap junctions are involved in the function of the adult rat pineal gland.     

Response of rat pineal melatonin to calcium, magnesium, and lithium is circadian stage dependent

Abstract: Herein we documented the response of pineal melatonin production to electrolytes known to be effective on pineal function in view of a possible circadian stage dependence. We studied the release of melatonin by perifused rat pineal glands at 2 different circadian stages corresponding to the middle of the light and dark periods, i.e., respectively, 7 and 19 HALO (Hours After Light Onset, L:D = 12:12). The initial efflux rates were, as expected, much higher in the perifusates of glands removed from rats sacrificed during the dark phase than of those removed during the light phase. After 3 hr of perifusion, melatonin release reached similar levels which were found constant up to the 8th hr of perifusion, whatever the circadian stage. Perifusion of the glands with physiological concentrations for the rat of calcium (5.2 mmol/1) and magnesium (1.34 mmol/1) resulted in a stimulatory effect on the pineal glands removed from rats sacrificed in the middle of the dark period (19 HALO), whereas no effects were observed on the pineal glands removed from rats sacrificed during the light (7 HALO). Lithium (0.28 and 0.55 mmol/1) was ineffective on melatonin release in pineal glands removed 7 and 19 HALO. Our results show differences in the initial efflux rates of melatonin and in the response of perifused pineal glands to calcium and magnesium according to the circadian stage.     

Conservative management of perforated duodenal diverticulum： A case report and review of the literature

Duodenal diverticula are a relatively common condition. They are asymptomatic, unless they become complicated, with perforation being the rarest but most severe complication. Surgical treatment is the most frequently performed approach. We report the case of a patient with a perforated duodenal diverticulum, which was diagnosed early and treated conservatively with antibiotics and percutaneous drainage of secondary retroperitoneal abscesses. We suggest this method could be an acceptable option for the management of similar cases, provided that the patient is in good general condition and without septic signs.     

Presence of immunoreactive growth hormone and prolactin in the ovine pineal gland

Abstract: The use of antisera raised against bovine growth hormone (GH) and ovine prolactin (PRL) enabled the detection of related immunoreactive (ir) sequences of proteins in ovine pineal tissue. The isolation of PRL-like ir-material was accomplished using a 0.25 M ammonium sulphate (pH 5.5) extraction followed by ethanol precipitation, whereas the resulting 2.0 M ammonium sulphate (pH 7.0) precipitate contained a GH-like immunoreactivity. Gel chromatography of the GH-like immunoreactivity (Sephadex G-100) indicated the presence of several GH-like fragments ranging in the M_r range of 7,000 to 55,000. Analyses of the PRL-like ir-material found in pineal tissue on HPLC using a TSK 545-DEAE column led to the resolution into a single peak of immunoreactivity. A single peak of activity was also observed following chromatofocusing and hydrophobic interaction chromatography of the ir-peak from the TSK 545-DEAE column. The PRL-like ir-material inhibited the binding of [¹²⁵I]ovine PRL-S14 to anti-ovine PRL antibodies without showing an affinity for binding to anti-rat PRL or anti-bovine GH antibodies. Scatchard analysis of the binding of pineal PRL-like ir-material and pituitary ovine PRL-S14 to liver membranes from day-20 pregnant rats revealed similar affinity constants (K_a of 4.7 ± 0.2 × 10⁹ M^-1). In addition, the replication of Nb 2 Node rat lymphoma cells was stimulated by pineal PRL-like ir-material, an effect known to be specific for lactogenic hormones. The pineal PRL-like immunoreactivity appeared on sodium dodecyl sulfate polyacrylamide gels as a single major band of M_r 24,000. The functional status of PRL-and GH-like ir-material in the ovine pineal remains to be determined, but evidence is presented that the overall protein synthesis rate of the rat pineal responded to circulating concentrations of PRL.     

Microbiology of human immunodeficiency virus anorectal disease

PURPOSE: Individuals who are seropositive for the human immunodeficiency virus are at high risk for opportunistic infection and anorectal disorders. Little prospective information is available regarding anorectal pathogens in these patients. METHODS: One hundred sixty-three HIV-seropositive patients presented to the colorectal clinic between 1989 and 1992. Forty-seven (29 percent) patients were thought to have an infectious process and were prospectively studied using a standardized multiculture protocol. RESULTS: Mean age was 33 (range, 19–59) years. All were male; high-risk behavior accounted for 87 percent of HIV transmissions. Presenting complaints included anorectal pain (79 percent), pus per anum (28 percent), and blood per anum (26 percent). Examination revealed perianal tenderness (60 percent), condyloma (38 percent), perianal ulcers (38 percent), and anal fissures (34 percent). Sixty-six sets of cultures were performed; 28 patients had one set, 15 had two sets, and 4 had three sets. Thirty-two of these 47 patients (68 percent) had positive cultures including herpes (50 percent), cytomegalovirus (25 percent),Neisseria gonorrhoeae (16 percent), chlamydia (16 percent), acidfast bacilli (2 percent), and others (9 percent). Six of 32 patients with positive cultures had more than one organism cultured. Sixteen (50 percent) patients with positive cultures were treated medically, 8 (25 percent) were treated surgically and 8 (25 percent) were treated with both modalities. Sixty-one procedures were performed on 17 patients for condylomata. Eighteen patients had 20 procedures for abscesses, 50 percent of whom had positive cultures for other than common bowel flora; all improved. Fourteen patients underwent 33 procedures for perianal fistulas.Mycobacterium fortuitum was cultured from one patient who required 13 procedures for abscesses and fistulas. Forty-five (96 percent) patients were followed for an average of 12.5 months ±2.9 SEM (range, 1–94 months). Symptoms were improved or resolved in 22 of 32 (69 percent) patients with positive cultures and in 11 of 13 (84 percent) with negative cultures. CONCLUSIONS: Specific pathogens may often be identified in human immunodeficiency virus-seropositive patients with anorectal disorders if aggressively sought. Although patients without specific pathogens identified may be expected to improve with planned empiric treatment, positive identification allows more directed therapy.