cDNA cloning and expression of a hamster alpha-thrombin receptor coupled to Ca2+ mobilization

The serine protease alpha-thrombin (thrombin) potently stimulates G-protein-coupled signaling pathways and DNA synthesis in CCL39 hamster lung fibroblasts. To clone a thrombin receptor cDNA, selective amplification of mRNA sequences displaying homology to the transmembrane domains of G-protein-coupled receptor genes was performed by polymerase chain reaction. Using reverse transcribed poly(A)+ RNA from CCL39 cells and degenerate primers corresponding to conserved regions of several phospholipase C-coupled receptors, three novel putative receptor sequences were identified. One corresponds to an mRNA transcript of 3.4 kb in CCL39 cells and a relatively abundant cDNA. Microinjection of RNA transcribed in vitro from this cDNA in Xenopus oocytes leads to the expression of a functional thrombin receptor. The hamster thrombin receptor consists of 427 amino acid residues with 8 hydrophobic domains, including one at the extreme N-terminus that is likely to represent a signal peptide. A thrombin consensus cleavage site is present in the N-terminal extracellular region of the receptor sequence followed by a negatively charged cluster of residues present in a number of proteins that interact with the anion-binding exosite of thrombin.

Epstein-Barr virus DNA in peripheral blood leukocytes of patients with posttransplant lymphoproliferative disease

We tested the hypotheses that Epstein-Barr virus (EBV) DNA levels in peripheral blood leukocytes (PBL) of transplant recipients with posttransplant lymphoproliferative disease (PTLD) (1) exceed those of patients without PTLD, (2) rise with or before clinical detection of the disease, and (3) fall with effective therapy. Using the polymerase chain reaction (PCR) and an endpoint dilution technique, we compared EBV DNA levels in sequential specimens from 5 patients with PTLD, 16 solid organ transplant recipients without PTLD, and 5 young adults with primary infectious mononucleosis (IM), and in single specimens from 21 healthy seropositive subjects. EBV DNA levels in the first two groups rose with induction of immunosuppression despite prophylactic acyclovir. Markedly elevated levels of EBV DNA were seen in 4 of 5 patients with PTLD at or before clinical diagnosis. The peak levels in these patients exceeded those of transplant recipients without PTLD (P = 0.02) and healthy adults with IM (P = 0.02). EBV DNA levels fell dramatically with effective therapy. Four of 21 healthy seropositive subjects demonstrated low levels of EBV DNA, similar to levels seen late in the course of patients with IM. We conclude that a semiquantitative PCR assay for EBV DNA in PBL can assist in the detection of PTLD and in monitoring the effect of therapy.

Cost-effectiveness of blood cultures for adult patients with cellulitis

To assess the cost-effectiveness of blood cultures for patients with cellulitis, a retrospective review was conducted of clinical and microbiological data for all 757 patients admitted to a medical center because of community-acquired cellulitis during a 41-month period. Blood cultures were performed for 553 patients (73%); there were a total of 710 blood samples (i.e., a mean of 1.3 cultures were performed per patient). In only 11 cases (2.0%) was a significant patient-specific microbial strain isolated, mainly beta-hemolytic streptococci (8 patients [73%]). An organism that was considered a contaminant was isolated from an additional 20 culture bottles (3. 6%). The cost of laboratory workup of the 710 culture sets was $36, 050. Isolation of streptococci led to a change from empirical treatment with cefazolin to penicillin therapy for 8 patients. All patients recovered. In conclusion, the yield of blood cultures is very low, has a marginal impact on clinical management, and does not appear to be cost-effective for most patients with cellulitis.

Procalcitonin in preterm infants during the first few days of life: introducing an age related nomogram

OBJECTIVE

To determine normal concentrations of procalcitonin in preterm infants shortly after birth and to assess its accuracy in detecting bacterial infection.

METHODS

Blood samples of 100 preterm infants were prospectively drawn during the first 4 days of life for determination of procalcitonin concentration. Infants were classified into four groups according to their sepsis status.

RESULTS

Mean (SD) gestational age and birth weight were 32 (2.9) weeks and 1682 (500) g respectively. A total of 283 procalcitonin concentrations from healthy infants were plotted to construct nomograms of physiologically raised procalcitonin concentration after birth, stratified by two groups to 24-30 and 31-36 weeks gestation. The peak 95th centile procalcitonin concentration was plotted at 28 hours of age; values return to normal after 4 days of life. Only 12 infants were infected, and 13 of their 16 procalcitonin concentrations after birth were higher than the 95th centile, whereas samples taken at birth were lower. In a multivariable analysis, gestational age, premature rupture of membrane, and sepsis status influenced procalcitonin concentration independently, but maternal infection status did not.

CONCLUSIONS

The suggested neonatal nomograms of preterm infants are different from those of term infants. Procalcitonin concentrations exceeding the 95th centile may be helpful in detecting congenital infection, but not at birth.

Influence of adenoviral fiber mutations on viral encapsidation, infectivity and in vivo tropism

Targeting of adenovirus (Ad)-encoded therapeutic genes to specific cell types has become a major goal in gene therapy. Redirecting the specificity of infection requires the abrogation of the natural interaction between the viral fiber and its cellular receptors (CAR) and the simultaneous introduction of a new binding specificity into the viral capsid. To abrogate the natural affinity of the fiber, we have mutated residues presumed to be directly or indirectly involved in CAR-binding in the knob domain of the fiber protein. These residues are located in the AB loop (Ser408) and in the DG loop (Tyr491, Ala494, Ala503). The mutations Ser408Glu, Tyr491Asp, Ala494Asp and Ala503Asp did not prevent the incorporation of trimeric fibers in the viral capsid but led to loss of CAR binding in vitro. Infectivity of the mutant viruses could be restored in vitro by introducing a ligand at the C-terminal end of the knob, confirming that the reduced infectivity of the fiber-modified virus was due to an impaired interaction of the viral particle with the CAR receptor. However, after systemic delivery, the in vivo biodistribution of impaired CAR-binding viruses without addition of a specific ligand was not altered when compared with wild-type Ad.

Fiberless recombinant adenoviruses: virus maturation and infectivity in the absence of fiber

In vivo targeting of therapeutic genes to specific tissues has become a major issue in gene therapy, in particular when recombinant adenovirus vectors are used. Restriction of the viral tropism to selected cell types requires the abrogation of the interaction between the viral fiber and its natural cellular receptors and the introduction of a new binding specificity into the virion. In this context, fiberless adenoviruses are attractive vectors, since they may be used as substrates for the insertion of a new ligand in other capsid proteins. In this study, we confirm by using cloned full-length adenovirus genomes with the fiber gene deleted that efficient virus particle formation can occur in the absence of fiber. As expected, the infectivity of such fiberless viruses was severely reduced, but it could be only partially restored when the viruses were produced in cells stably providing the fiber in trans. Although incorporation of penton base into the fiberless particles was normal and binding of the particles to the cellular integrins was functional, several pieces of experimental evidence suggest that later steps in the cell entry process are impaired in correlation with an incorrect maturation of several structural proteins of the fiberless particles. These observations support the hypothesis that the fiber protein may have additional biological functions besides its role in cell binding. Together with the fiber complementation cells, such fiberless vectors constitute unique tools to investigate the role of the fiber in virus assembly, maturation, and cell entry and to explore the possibility of deriving gene transfer vectors with novel target specificities.

Herpes simplex virus type 2 meningitis in the absence of genital lesions: improved recognition with use of the polymerase chain reaction

Herpes simplex virus type 2 (HSV-2) is known to cause aseptic meningitis, which can be recurrent. The diagnosis of HSV-2 infection is suggested when meningitis occurs simultaneously with genital lesions but may be obscure if genital lesions are not present or are not appreciated. Viral culture of the CSF is sometimes positive, but it may also be negative, especially in cases of recurrent disease. We report three cases of HSV meningitis in young women who did not have a history of genital herpetic lesions and for whom genital lesions were not noted on presentation. With use of the polymerase chain reaction (PCR), HSV DNA was detected in CSF from all three patients. The diagnosis of HSV meningitis was further confirmed by a positive culture of CSF in one patient's case and by demonstration of intrathecal synthesis of HSV antibodies in a second patient's case. The use of PCR can improve the recognition of HSV meningitis in adults presenting with aseptic meningitis, even in the absence of herpetic lesions.

A week-by-week analysis of the low-risk criteria for serious bacterial infection in febrile neonates

OBJECTIVE

To examine the reliability of "low-risk" criteria (LRC) to exclude serious bacterial infection (SBI) in febrile neonates (< or =28 days), according to age in weeks.

DESIGN

Epidemiological and clinical data and final diagnosis of all febrile neonates presenting to the emergency room from June 1997 to May 2006 were reviewed. Neonates who fulfilled specific LRC for the presence of SBI were classified as LRC+. The prevalence of SBI and the percentage of LRC+ neonates who had SBI were calculated for each of the first 4 weeks of life.

RESULTS

A total of 449 neonates were evaluated. Eighty-seven (19.4%) neonates had an SBI. The prevalence of SBI among infants 3-7, 8-14, 15-21 and 22-28 days of age was 21.6%, 26.1%, 17.9% and 12.1%, respectively (p = 0.007 for linear trend after second week of life). Of the 226 LRC+ neonates, 14 (6.2%) had an SBI, including one case of bacteraemia and meningitis and 13 cases of urinary tract infection (UTI). The negative predictive value (NPV) of the LRC for SBI was 93.8% (95% CI 90.1% to 96.4%). The prevalence of SBI among LRC+ infants 3-7, 8-14, 15-21 and 22-28 days of age was similar, with rates of 15%, 6.3%, 3.0% and 6.7%, respectively.

CONCLUSION

LRC are not sufficiently reliable to exclude the presence of SBI, including bacteraemia and meningitis in febrile neonates of all ages. All febrile neonates should therefore be hospitalised, undergo a full "sepsis evaluation" and receive empirical intravenous antibiotic therapy.

Prevalence and predictive features of bacteremic urinary tract infection in emergency department patients

The aim of this study was to determine the prevalence and predictive features of bacteremia among patients evaluated in the emergency department for urinary tract infection. Of the 350 patients with symptomatic urinary tract infection included in this retrospective study, 53 (15%; 95%CI 11.6-19.4%) were bacteremic. Five variables were independently associated with bacteremia: residence at home rather than in an institution (OR 4; 95%CI 1.5-10.7), presence of an indwelling urinary catheter (OR 3.3; 95%CI 1.3-8.8), presence of band forms in the blood count (OR 3.3; 95%CI 1.5-7.2), shaking chills (OR 2.3; 95%CI 1.1-4.8), and neutrophilia (OR 1.1; 95%CI 1.04-1.15). These easily assessable parameters may assist in the diagnosis of bacteremic urinary tract infection and the selection of empiric antibiotic treatment, thus potentially improving a patient's prognosis.

Expanded spectrum of herpes simplex encephalitis in childhood

We designed a polymerase chain reaction method to detect herpes simplex virus (HSV) DNA in spinal fluid from patients with encephalitis. The polymerase chain reaction amplified a 211 base-pair segment of the HSV DNA polymerase gene. Applying this method, we diagnosed HSV type 1 infection in three young children, aged 7 to 13 months, who had atypical forms of the illness. On the basis of magnetic resonance imaging, their disease was diffuse or multifocal in two cases and, in all three, lacked the temporal lobe involvement considered characteristic of HSV encephalitis beyond the neonatal period. Most of the diffuse or multifocal abnormalities detected by magnetic resonance imaging were not apparent by computed tomography. Restriction enzyme analysis of the polymerase chain reaction products from all three patients indicated that their disease was caused by HSV type 1. We conclude that in preschool-age children beyond the neonatal period, the spectrum of HSV encephalitis includes multifocal or diffuse involvement of the brain, which may be detected most efficiently by magnetic resonance imaging. The polymerase chain reaction method has the potential for providing an early diagnosis, but further studies are required to define the sensitivity and specificity of the polymerase chain reaction before it can be used for routine clinical decision making.

MR imaging of herpes simplex type 1 encephalitis in infants and young children: a separate pattern of findings

OBJECTIVE

We sought to identify the initial MR findings of herpes simplex encephalitis in infants and young children.

CONCLUSION

MR imaging findings of herpes encephalitis in infants and young children appear to differ from those seen in neonates, older children, and adults. Appreciation of this MR imaging pattern coupled with a strong clinical suspicion of herpes helps to ensure the correct diagnosis is made.

Longitudinal surveillance of antibiotic use in the hospital

We evaluated antimicrobial use in our hospital by department, including indications for use, source of infections, use of the microbiology laboratory, and appropriateness of prescribing, in a prospective, comparative, non-interventional study of all patients receiving antimicrobial agents. We excluded departments where antimicrobial use was negligible. The other 19 departments were followed for 3 (n=4) or 4 (n=15) months, including 2 consecutive months in the spring-summer and either 1 or 2 in the autumn-winter. Antimicrobial therapy was followed from initiation, through possible adaptations, and possible change from intravenous to oral therapy, until discontinuation of treatment. Overall, 6376 antibiotics were given to 2306 patients. Of the surveyed hospitalized patients, 62%+/-22% received antibiotics, with a range of 4-100% per department. Antibiotics were prescribed for infections acquired in the community (3037 instances, 47%), in the hospital (2182, 34%), in a nursing home (575, 9%), and for prophylaxis continued post-operatively (582, 9%). The most common indications for antimicrobial use were: respiratory tract infection (1729, 27%), urinary tract infection (955, 15%), sepsis (701, 11%), intra-abdominal infections (663, 10%), prophylaxis 582 (9%), soft-tissue infection (572, 9%), and surgical site infection (319, 5%). Univariate indicators for appropriateness of treatment were: age, department, site of infection, source of infection, antimicrobial drug and serum creatinine (all p<0.001). Forty-nine antimicrobials were prescribed in 279 combinations, 58% as single agent and 42% as drug combinations. Half of all antimicrobial use consisted of four agents: cefuroxime (19.1%), metronidazole (11.3%), gentamicin (10.6%) and ampicillin (10.2%), which together accounted for 20% of expenditure on antibiotics. Although use of as many as 53% of antimicrobials (26/49) surveyed was restricted, use in this category accounted for only 29% of all antimicrobial courses. Of 6376 antibiotic courses, 4101 (64%) were given intravenously and 2275 (36%) orally. Appropriateness of use of restricted drugs was lower (70%) than of unrestricted ones (84%, p<0.001). Of 24571 defined daily doses (DDD) given orally, 4587 (19%) were restricted, compared to 7264 (34%) of 21602 DDDs given intravenously (p<0.001). Antibiotic treatment in our hospital appears to be substantial and increasing, justifying efforts to improve appropriateness of therapy and improve clinical and financial results.

Surveillance of antimicrobial prophylaxis for surgical procedures

OBJECTIVE

To assess the practice of antimicrobial prophylaxis for surgical procedures in eight surgical departments in a 550-bed teaching hospital.

METHODS

A list of all major procedures performed in our hospital, with recommendations for prophylaxis based upon the literature, has been distributed since 1993 and is updated periodically. The practice of surgical prophylaxis between January 1 and March 31, 1996, was examined by assessing four variables: (1) Did the particular procedure justify prophylaxis, and was it provided? (2) Was timing optimal, ie, within 1 hour prior to surgery? (3) Was the appropriate antimicrobial selected? (4) Was duration optimal, ie, < or =24 hours?

RESULTS

During the study period, 2,117 operations were performed, of which 1,631 (77%) were reviewed. Sixty-six percent were clean surgery, 28% clean-contaminated, and 6% contaminated; 72% of procedures were elective, 28% emergencies. Of 1,631 operations requiring prophylaxis, 1,142 (70%) received it, 489 (30%) did not. Of 1,631 patients, 1,392 (85%) received appropriate care: 929 (67%) appropriately received prophylaxis, and 463 (33%) appropriately did not receive prophylaxis. Of 955 patients who received prophylaxis, 26 (3%) did so inappropriately. Of 1,142 patients who should have received prophylaxis, 213 (19%) did not receive it. Female gender, clean surgery, elective operations, and infrequently performed procedures were all significant indicators of inappropriately withheld prophylaxis (P<.001). In addition, the rate of appropriately provided prophylaxis varied between departments from 71% to 97% (P<.001). Assessment of the 929 procedures for which prophylaxis was justified and given revealed that 100% of patients received it on time, the choice of antimicrobial was appropriate in 95% of cases, and duration was < or =24 hours in 91%.

CONCLUSIONS

Audits of surgical prophylaxis are expected to detect different errors in different institutions. Conducting audits of surgical prophylaxis probably should be part of the routine activity of infection control teams. Feeding the information back to surgeons could improve adherence to recommended guidelines and might contribute to reduced wound infection rates.

Cytomegalovirus-associated protein-losing gastropathy in childhood

Menetrier's disease is an uncommon disease in childhood, characterized by gastric hypertrophy and hypoalbuminemia secondary to protein loss through the gastric mucosa. This paper describes a series report of protein-losing gastropathy associated with cytomegalovirus (CMV) infection in children and reviews the literature. We reviewed the medical records of eight children with diagnosis of Menetrier's disease or protein-losing gastropathy with evidence of acute CMV infection. During a five-year period there were eight children that were diagnosed with CMV-associated protein-losing gastropathy, all in one medium-sized pediatric ward in a general hospital. The mean age was 32 months and there was no gender predominance. The most common presenting symptoms were vomiting and edema. Average symptoms' duration prior to admission was 3.2 weeks and mean albumin at presentation was 1.8 g/dl (range, 1.5-2.5 g/dl; normal values, 3.5-5 g/dl). All eight children fully recovered. In conclusion, CMV infection should be suspected in every child who presents with protein-losing gastropathy. The availability of newer, rapid diagnostic techniques such as polymerase chain reaction (PCR) may facilitate diagnosis, as serology studies may be misleading. Usually, only supportive care is required, but treatment with ganciclovir may be considered for severe or prolonged cases.

Changing epidemiology of infective endocarditis: a retrospective survey of 108 cases, 1990-1999

The aim of this study was to report the experience with infective endocarditis over the past decade, describe the changing clinical and epidemiological features of the disease, and attempt to determine the optimal number of blood culture sets required for diagnosis. All cases diagnosed during a 10-year period were reviewed clinically and microbiologically. In addition, a retrospective assessment of blood culture data was performed. From the period 1990-1999, 108 cases that met the von Reyn or Duke's criteria were recorded. The major underlying cardiac condition was the presence of a prosthetic valve ( n=33 patients, 31%). Among patients with native valves, nonrheumatic valvular heart disease of the elderly was the most common underlying factor ( n=19 patients, 25%). Overall, 13 patients (11%) died. Predictors on admission for increased mortality were shortness of breath, age >60 years, time to defervescence, erythrocyturia, hemoglobin level <10 g/dl, and leukocytosis >15,000 (all P<0.05). Analysis of blood culture data showed that the diagnostic yield among groups from whom either only one or more than six blood culture sets were drawn was reduced compared with that among groups from whom between two and five culture sets had been taken. The outcome of endocarditis in this series from a community hospital was much more favorable compared with that reported in surveys from large tertiary centers. Moreover, obtaining more than two or three blood cultures is neither helpful nor cost-effective in the initial assessment of patients with suspected endocarditis.

Prospective hospital-wide studies of 505 patients with nosocomial bacteraemia in 1997 and 2002

We conducted surveys in 1997 and 2002 to determine the rate, underlying sources and outcome of nosocomial bacteraemia. Blood culture results were reviewed daily. All patients with positive cultures drawn >or=48 h after hospitalization were included in the study and their charts were reviewed. The underlying source of infection was determined by pre-defined clinical and/or microbiological criteria. Patients were followed until discharge or death. In 1997 and 2002, 851 and 857 patient-unique cases of bacteraemia were diagnosed, respectively, excluding contaminants; of these, 228 (27%) and 277 (32%) cases, respectively, were hospital acquired (P<0.05). The overall rate decreased from 7.5 to 7.0 per 1,000 admissions (P<0.001). The sources of bacteraemia in 1997 and 2002, respectively, were: intravascular catheters (36% and 27%, P<0.05), urinary tract (8% and 15%, P<0.05), respiratory tract (5% and 13%, P<0.01) and surgical sites (14% and 4%, P<0.001). In one-third of patients, the source of bacteraemia could not be determined. Only 52% and 54%, respectively, of these patients were discharged alive (difference was not significant). In 1997, Staphylococcus aureus was the most frequent isolate (26%), followed by coagulase-negative Staphylococcus (13%) and Klebsiella pneumoniae (11%). By 2002, the incidence of S. aureus had fallen to 11% (P<0.001), acinetobacter was the single most frequently isolated organism (increased from 6% to 17%) (P<0.001). In-hospital mortality associated with acinetobacter bacteraemia (57%) was significantly higher than that for other organisms (31-43%) (P<0.05). In conclusion, prospective surveys of nosocomial bacteraemias provide valuable information, facilitating the pursuit of successful interventions.

Adult patients with occult bacteremia discharged from the emergency department: epidemiological and clinical characteristics

To determine the epidemiological and clinical characteristics of patients who were discharged from the emergency department (ED) and subsequently proved to have bacteremia, we prospectively assessed all patients examined in the ED during an 18-month period from whose blood cultures a significant organism was isolated. Discharged patients were contacted and reevaluated. Two case-control studies were conducted, in which each study patient was matched with a total of 4 control patients. During the study period, 46,336 patients were examined in the ED; 78% were adults and 22% were children. Blood cultures were performed for 25% of the adult patients and for 44% of the children. Although the occurrence of occult bacteremia in patients who were discharged from the ED is 3.7 times more common in children than in adults, the absolute numbers of discharged adults and children with occult bacteremia are similar. Careful clinical assessment will not prevent discharge of some of these patients; however, these patients in general do well and can be safely recalled for reevaluation and complementation of therapy.

Novel human gene transfer vectors: evaluation of wild-type and recombinant animal adenoviruses in human-derived cells

Major disadvantages of human adenovirus (hAd) vectors in gene therapy include preexisting or induced immune responses, and possible coreplication of recombinant hAd in the presence of wild-type hAds. These disadvantages may be overcome by using nonhuman, animal adenoviruses (aAds). We evaluated four different aAds for their potential use as viral vectors. The canine adenovirus type 2 (CAV2) and bovine adenovirus type 3 (BAV3) appeared to be suitable systems, as they infect human cells. CAV2, but not BAV3, caused cytotoxicity, and only limited (CAV2) or no (BAV3) production of infectious virus particles was observed after infection of human cell lines. CAV2 showed higher expression of endogenous genes than did BAV3 in the tested human cells. No interference between hAd and CAV2 or BAV3, such as recombination of DNA or cross-activation of virus replication, was observed in up to five passages in double-infected human cells. Transfection of cloned genomic CAV2 or BAV3 DNA into appropriate permissive cell lines rescued infectious virus. Furthermore, we produced a recombinant E1-deleted BAV3, and showed that it could infect and express a reporter gene in various human cell types. The goal was to construct and evaluate recombinant (E1-deleted) animal adenoviruses (aAds) as new vector systems for human gene therapy. The rationale for developing aAds for human use is the potential higher safety and efficiency, as compared with human adenoviruses (hAds). Coreplication and recombination with preexisting hAds should not be possible owing to lack of homology, and preexisting immunity in the general population should be limited. Of the four aAds we evaluated, BAV3 appeared to be the best candidate. It infects human cells without showing growth or cytotoxic effects, viral gene expression was barely detectable, and no trans-activation of either virus was detected in coinfections with hAd5. Rescue of virus in permissive cells, from plasmids containing the CAV2 or BAV3 genome, confirmed our approach. Furthermore, an E1-deleted recombinant BAV3 was constructed and shown to transduce and express the lacZ reporter gene in human cells.