Clinical Symptoms Of Infection Research Articles

Rekonstruktive Chirurgie bei Patienten mit Herzunterstützungssytemen (Ventricular Assist Device, VAD) - eine interdisziplinäre Herausforderung

Ventricular assist devices (VAD) are implanted with a growing frequency in patients with end-stage heart failure. In spite of technical and therapeutic advances, there is still a high incidence of device infections and healing disturbances with a considerable mortality. Reconstructive plastic surgery is able to provide help in erradicating infections and covering defects. 11 patients with device infections and soft tissue defects were treated in our institution. All cases were treated with local myocutaneous or muscle flaps. Three patients had postoperative haematomas which had to be revised surgically. One patient had a persistent fistula of mediastinal origin but without clinical symptoms of infection. One patient exhibited an enterocutaneous fistula after defect coverage. Patients with VADs have a high possibility of perioperative complications. Therefore a close interdisciplinary approach with plastic and cardiovascular surgeons is absolutely essential.

Prevalence of spontaneous bacterial peritonitis in asymptomatic inpatients with decompensated liver cirrhosis – a pilot study

To assess the prevalence of spontaneous bacterial peritonitis (SBP) in asymptomatic patients with decompensated liver cirrhosis. Patients (pts) with symptoms of decompensation of liver cirrhosis, ascites, and no signs indicating SBP were included to our study. Exclusion criteria include: 1/ clinical symptoms of infection, 2/ developing de novo or worsening hepatic encephalopathy, 3/ gastrointestinal bleeding within the last month, 4/ renal failure, 5/ antibiotic treatment or norfloxacin prophylaxis at admission. About 60 ml of ascitic fluid were drawn for lab examination. Pathologic assessment for atypical cells was also performed. 37 patients fulfilled inclusion criteria. Their mean age was 56.2 ± 12.1. The Child-Pugh classification revealed 13 (35.1%) patients of class B and 24 (64.9%) patients of class C. The mean Model for End-Stage Liver Disease score in this group was 16.6 ± 6.8. The mean ascitic protein content was 1.85 ± 1.09 g/dL and mean neutrophil count 144.8 ± 445.1/mm3. Ascitic fluid analysis revealed: signs of bacterascites in 6 of 37 (16.2%) pts; neutrocytic ascites in 1 of 37 (2.7%) pts; and 2 of 37 (5.4%) pts met criteria for SBP. C-reactive protein level was the best predictor of infection [SBP(+) 47.9 ± 40.9 versus SBP(-) 11.7 ± 5.1; p= 0.0005]. The prevalence of SBP in asymptomatic cirrhotics with ascites is low. We observed the trend towards more frequent occurrence of the infection in patients suffered from severe liver disease (Child-Pugh C group).

Glycosylphosphatidylinositol Anchor Analogues Sequester Cholesterol and Reduce Prion Formation

A hallmark of prion diseases is the conversion of the host-encoded prion protein (PrP(C) where C is cellular) into an alternatively folded, disease-related isoform (PrP(Sc), where Sc is scrapie), the accumulation of which is associated with synapse degeneration and ultimately neuronal death. The formation of PrP(Sc) is dependent upon the presence of PrP(C) in specific, cholesterol-sensitive membrane microdomains, commonly called lipid rafts. PrP(C) is targeted to these lipid rafts because it is attached to membranes via a glycosylphosphatidylinositol anchor. Here, we show that treatment of prion-infected neuronal cell lines (ScN2a, ScGT1, or SMB cells) with synthetic glycosylphosphatidylinositol analogues, glucosamine-phosphatidylinositol (glucosamine-PI) or glucosamine 2-O-methyl inositol octadecyl phosphate, reduced the PrP(Sc) content of these cells in a dose-dependent manner. In addition, ScGT1 cells treated with glucosamine-PI did not transmit infection following intracerebral injection to mice. Treatment with glucosamine-PI increased the cholesterol content of ScGT1 cell membranes and reduced activation of cytoplasmic phospholipase A(2) (PLA(2)), consistent with the hypothesis that the composition of cell membranes affects key PLA(2)-dependent signaling pathways involved in PrP(Sc) formation. The effect of glucosamine-PI on PrP(Sc) formation was also reversed by the addition of platelet-activating factor. Glucosamine-PI caused the displacement of PrP(C) from lipid rafts and reduced expression of PrP(C) at the cell surface, putative sites for PrP(Sc) formation. We propose that treatment with glucosamine-PI modifies local micro-environments that control PrP(C) expression and activation of PLA(2) and subsequently inhibits PrP(Sc) formation.

Molecular Biology and Pathogenesis of Crimean–Congo Hemorrhagic Fever Virus

Over the last several years, we have experienced an increase of large outbreaks of Crimean–Congo hemorrhagic fever virus in European countries and neighboring areas. This disease poses a great threat to public health owing to its high mortality rate, modes of transmission and geographical distribution. Clinical symptoms of infection commonly include hemorrhage, myalgia and fever. The complexity of the technical and facility requirements, in combination with the sporadic outbreaks and consequent lack of clinical specimens has resulted in very limited research of Crimean–Congo hemorrhagic fever virus. To date, there is no vaccine available and a selective antiviral drug for the treatment of the disease is not expected in the near future. Here, we review the most recent findings on the Crimean–Congo hemorrhagic fever virus molecular biology and pathogenesis, including aspects of virus–host cell interactions.

Enhanced enzymatic activity of Candida species responsible for oral candidiasis in renal transplant recipients

Renal transplant recipients (RTRs) are regarded to be predisposed to oral candidiasis. This study was undertaken to evaluate the activity of hydrolytic enzymes in strains causing oral candidiasis in RTR. A total of 123 Candida albicans and 10 Candida krusei strains were isolated from 200 RTRs (39 RTRs suffered from symptomatic candidiasis, the remaining patients had no clinical symptoms of infection). All fungi were identified based on routine mycological procedures. Because of a small number of non-albicans strains, only C. albicans isolates were compared for enzymatic activity. The activity of 19 hydrolytic enzymes was assessed by API ZYM(®) test. The usage of mycophenolate mofetil was connected with higher ratio of clinically apparent oral candidiasis compared to immunosuppressive regimens without this drug (74.4% vs. 46.8%, respectively, P < 0.01). Candida albicans from RTRs showed higher enzymatic activity compared with strains from immunocompetent patients. Only two enzymes were found to be more active in C. albicans causing symptomatic candidiasis in RTRs (cystine arylamidase: P = 0.001, and α-fucosidase: P = 0.01) compared with saprophytic strains. Atrophic candidiasis showed higher activity of esterase lipase (C8) and α-mannosidase compared with the pseudomembraneous type. We suggest that the enhanced enzymatic activity is responsible for higher invasiveness of Candida residing in the oral cavity of RTRs.

Repeat 2-Stage Revision for Recurrent Infection of Total Hip Arthroplasty

Eleven patients who developed reinfection after 2-stage revision for infected total hip arthroplasty (THA) were treated with a repeat 2-stage rerevision. Of the 11 rerevisions, 4 were successful, with no recurrent infection at mean follow-up of 44 months. Reinfection occurred in 7 patients of whom 6 involved either a significantly compromised host or poor local wound status. Clinical symptoms of infection were controlled in 4 of the 7 reinfected cases with antibiotic therapy in 2, irrigation and debridement in 1, and a third 2-stage revision THA in 1. Repeat 2-stage treatment of infected THA is associated with a high failure rate. However, successful results can be achieved particularly if the host is not immunocompromised and healthy soft tissue coverage is present.

Coding nucleotide sequences of tick-borne encephalitis virus strains isolated from human blood without clinical symptoms of infection

Genomes of four tick-borne encephalitis virus strains, isolated from the blood of the individuals after tick bites and causing no clinical symptoms of infection, were characterized. Analysis of translated polypeptides revealed 21 amino acid positions typical of this group of strains and distinguishing them from the other tickborne encephalitis virus strains of Far Eastern subtype examined earlier. Only three mutations led to substantial amino acid changes, which probably could affect the infection process severity. It is suggested that two associated mutations, deletion of amino acid 111 in the capsid protein C and substitution (Ser1534 --> Phe) in the NS3 protein influence strictly coordinated polyprotein processing, disturbing correct arrangement of viral particles. This process can result in the development of defect viral particles, containing no RNA. Mutation (Ser917 --> Gly) in nonstructural protein NS1 results in the substitution of hydrophilic amino acid, specific to highly virulent strains, by the hydrophobic one. This could influence the effectiveness of viral replication complex, thereby affecting the infectivity of tick-borne encephalitis virus strains.

Marked increase of procalcitonin after the administration of anti-thymocyte globulin in patients before hematopoietic stem cell transplantation does not indicate sepsis: a prospective study

IntroductionProcalcitonin (PCT) and C-reactive protein (CRP) are established markers of infection in the general population. In contrast, several studies reported falsely increased PCT levels in patients receiving T-cell antibodies. We evaluated the validity of these markers in patients scheduled for hemopoietic stem cell transplantation receiving anti-thymocyte globulin (ATG) during conditioning. We also assessed renal and liver functions and their relationship to PCT and CRP changes.MethodsTwenty-six patients without clinical signs of infection were prospectively studied. ATG was administered in up to three doses over the course of 5 days. PCT, CRP, white blood cell (WBC) count, urea, creatinine, glomerular filtration rate, bilirubin, alanin amino-transferase (ALT), and gamma-glutamyl transferase (GGT) were assessed daily during ATG administration. Pharyngeal, nose, and rectal swabs and urine samples were cultured twice weekly. Blood cultures were obtained if clinical symptoms of infection were present.ResultsBaseline (BL) levels of both PCT and CRP before ATG administration were normal. WBC count decreased after ATG administration (P = 0.005). One day after ATG administration, both PCT and CRP levels increased significantly, returning to BL levels on day 4. Microbiological results were clinically unremarkable. There was no interrelationship between PCT levels and BL markers of renal or liver functions (P > 0.05 for all comparisons). Bilirubin and GGT were increased on days 2 to 5 and ALT was increased on day 3 (P < 0.05 versus BL). No difference in renal functions was observed. Three patients developed bacterial infection on days 7 to 11 with different dynamics of PCT and CRP. There was no association between the number of ATG doses and PCT levels or between the risk of developing infection and previous PCT levels.ConclusionsATG triggered a marked early surge in PCT and CRP followed by a steady decrease over the course of 3 days. The dynamics of both PCT and CRP were similar and were not associated with infection. PCT levels were independent of renal and liver functions and were not predictive of further infectious complications. A direct effect of ATG on T lymphocytes could be the underlying mechanism. Hepatotoxic effect could be a contributing factor. Neither PCT nor CRP is a useful marker that can identify infection in patients receiving ATG.

Use of the serum reactivity against Toxoplasma gondii excreted–secreted antigens in cerebral toxoplasmosis diagnosis in human immunodeficiency virus-infected patients

Despite the development of serological and molecular methods in recent years, the diagnosis of cerebral toxoplasmosis in human immunodeficiency virus (HIV)-infected patients still presents difficulties. In the present study, we investigated whether cerebral toxoplasmosis induced changes in the reactivity of serum toward Toxoplasma gondii excreted-secreted antigens (ESA) in order to develop an assay for evaluating HIV-infected patients with cerebral toxoplasmosis. The antigen selection was based on those produced by tachyzoites, since it is the form of the organism responsible for disseminating the infection, as well as stimulation of the humoral and cellular immune responses. By using an ELISA containing pooled ESA recovered from infected culture supernatants with tachyzoites-RH strain (ESA-ELISA), we found that ESA had a high specificity for sera from patients with cerebral toxoplasmosis. The reactions were compared with an ELISA using crude tachyzoites antigen, widely used in traditional serology. The assays were performed on 293 serum samples separated as follows: 100 sera from patients with cerebral toxoplasmosis and AIDS (symptomatic), 99 sera from individuals with chronic toxoplasmosis (asymptomatic) and 94 sera from healthy individuals without toxoplasmosis (control). The crude tachyzoite antigen in ELISA was able to distinguish both groups of sera with toxoplasmosis, as similar reactivity were observed in sera from patients with cerebral toxoplasmosis and those from chronic individuals. In contrast, ESA-ELISA distinguished sera from symptomatic and asymptomatic individuals (three times more reactive in the former group, 12.6 versus 4.2). The assays were reproducible based on immunoblotting and statistical analysis. These data suggest the utility of ESA-ELISA in the diagnosis of cerebral toxoplasmosis in HIV-infected patients, since it provided clear evidence that anti-ESA antibodies are present principally in patients with active infection. The absence of a significant amount of antibodies distinguished the patients without clinical symptoms of infection.

Sensitive detection of human cytomegalovirus in tumors and peripheral blood of patients diagnosed with glioblastoma

Human cytomegalovirus (HCMV) has been described to be associated with several human malignancies, though the frequency of detection remains controversial. It is unclear whether HCMV plays an active role in malignant tumor progression or becomes reactivated under pathologic conditions that result in chronic inflammation or immunosuppression. In this study, we report on the investigation of detecting HCMV in the tumors and peripheral blood of patients with newly diagnosed glioblastoma multiforme (GBM). Using immunohistochemistry, in situ hybridization, and polymerase chain reaction amplification of viral DNA, the detection of HCMV was investigated in tumor and blood specimens from patients with GBM as well as in the peripheral blood of normal volunteers and patients undergoing craniotomy for diagnoses other than GBM. We found that a high percentage (>90%) of GBM tumors, not surrounding normal brain, are associated with HCMV nucleic acids and proteins. Furthermore, a significant proportion of patients (80%) with newly diagnosed GBM have detectable HCMV DNA in their peripheral blood, while sero-positive normal donors and other surgical patients did not exhibit detectable virus, suggesting either a systemic reactivation of HCMV within patients with GBM or shedding of viral DNA from infected tumor cells into the periphery. These results confirm the association of HCMV with malignant gliomas and demonstrate that subclinical HCMV viremia (presence of viral DNA in blood without clinical symptoms of infection) is a previously unrecognized disease spectrum in patients with GBM.

Análisis microbiológico del semen de los varones en estudio de infertilidad

Introduction Bacteriospermia is frequently found in semen samples from men undergoing evaluation for infertility, even when clinical symptoms of infection of the accessory sex glands are absent. Leukocytes are also frequently found in the semen of these men, although there is controversy on the relationship between leukospermia and bacteriospermia –especially in asymptomatic patients – and on whether the presence of bacteria is simply due to contamination. The aim of the present study was to analyze the microbiological findings in semen from patients undergoing infertility evaluation and to determine the presence of pathogenic microorganisms. Methods The results of cultures from 1,376 men (first and midstream urine fractions, and semen) undergoing infertility evaluation during a 2-year period were analyzed. Results In 26% of the men studied, at least one pathogenic microorganism was detected in semen, the most frequent being Escherichia coli (24%). Ureaplasma urealyticum was found in 26% of the men. Conclusions Pathogenic microorganisms were found in more than 25% of a large sample of men. This finding indicates the need to perform urine and semen culture in these patients.

Anthrax: the challenges for decontamination

AbstractAnthrax remains endemic in many parts of the world with regular infections of livestock presenting a consequent risk to public health. In the United Kingdom anthrax has diminished as a significant threat to human health with only sporadic outbreaks in farm animals derived from ingestion of spores from soil at sites associated with previous outbreaks and the burial of carcasses. Occupationally‐derived anthrax, associated with industries involved in the processing of animal products, has historically had an impact on the occurrence of outbreaks of infection. The introduction, in 1965, of vaccination for workers in high‐risk occupations contributed significantly to the eradication of the disease from the UK. During 2001 the deliberate release of anthrax spores in the USA, disseminated through the postal system, resulted in the infection of 22 people, five of which resulted in death through inhalational anthrax. At that time anthrax was unheard of in many clinical practices and there was a lack of training and preparedness to handle such incidents; the emergency resulted in medical and public health personnel across the world having a significantly raised awareness of both the organism and the clinical symptoms of infection, and the new threat posed by bioterrorism. In the USA, the immediate public health emergency was followed by the legacy of contaminated buildings and facilities. There had been little previous systematic study of the issues surrounding sampling and decontamination of areas contaminated with Bacillus anthracis. The decontamination of large complex buildings and the equipment they contained required the urgent development and validation of new procedures for both sampling and decontamination. Copyright © 2006 Society of Chemical Industry

Cat bite wound infections: A prospective clinical and microbiological study at three emergency wards in Stockholm, Sweden

The rate of infection following cat bites appears to be greater than that from dog bites. To study the clinical picture, complications and microbiology (in humans and cats), this prospective study was performed. A prospective study with patients with clinical symptoms of infection due to cat bites from three emergency wards during two years in Stockholm, Sweden. Aerobic and anaerobic cultures from the wounds were performed as well as cultures from the biting cat's mouth. Clinical data and complications were registered. Seventy-nine episodes in 78 patients with infective cat bites were included. Pasteurella multocida was isolated in 70% of the patients; in addition anaerobic pathogens were isolated in 16% concurrently with P. multocida, while Staphylococcus aureus was isolated in only two patients. Pasteurella spp. was also isolated from 80% of the pharynx of the biting cats. The dominating symptoms of infection were erythema, pain and oedema, often emerging as early as 3h after the bite. Complications such as tendosynovitis, arthritis, abscesses and septicaemia occurred in 18% of the patients. No patient died due to the infection. The majority of the patients received penicillin or amoxicillin as antibiotic treatment. P. multocida was the dominating pathogen among patients with infected cat bites and antibiotic treatment should cover P. multocida.

Prolonged dysphagia due to Listeria-rhombencephalitis with brainstem abscess and acute polyradiculoneuritis

We report a case of previously healthy student with acute rhombencephalitis and brainstem abscess caused by Listeria monocytogenes. The disease begun with uncharacteristic prodromal symptoms of gastrointestinal infection followed by headache and vertigo. After hospital admission the patient rapidly deteriorated, presenting pronounced dysphagia and respiratory failure requiring mechanical ventilation. The diagnosis was established upon clinical symptoms of infection, brainstem involvement, typical MRI findings and positive for L. monocytogenes blood culture. Infection was complicated by acute, demyelinating neuropathy, diagnosed upon clinical symptoms of frail palsy confirmed by ENG. Initially introduced empirical doxycyclin/ceftriaxon treatment was subsequently changed to targeted ampicillin/gentamycin therapy, mechanical ventilation, intravenous human immunoglobulin treatment, tracheostomy and endoscopic gastrostomy. Prolonged dysphagia resolved after rehabilitation. After one year the patient remains well with only slight dysmetria.

Rapid serodiagnosis of Staphylococcus aureus surgical site infection following median sternotomy

To determine the sensitivity and specificity of a novel ELISA for the serodiagnosis of surgical site infection (SSI) due to staphylococci following median sternotomy. Twelve patients with a superficial sternal SSI and 19 with a deep sternal SSI due to Staphylococcus aureus were compared with 37 control patients who also underwent median sternotomy for cardiac surgery but exhibited no microbiological or clinical symptoms of infection. A further five patients with sternal SSI due to coagulase-negative (CoNS) staphylococci were studied. An ELISA incorporating a recently recognised exocellular short chain form of lipoteichoic acid (lipid S) recovered from CoNS, was used to determine serum levels of anti-lipid S IgG in all patient groups. Serum anti-lipid S IgG titres of patients with sternal SSI due to S. aureus were significantly higher than the control patients (P<0.0001). In addition, patients with deep sternal SSI had significantly higher serum anti-lipid S IgG titres than patients with superficial sternal SSI (P = 0.03). Serum anti-lipid S IgG titres of patients with sternal SSI due to CoNS were significantly higher than the control patients (P = 0.001). The lipid S ELISA may facilitate the diagnosis of sternal SSI due to S. aureus and could also be of value with infection due to CoNS.

Diagnostic non bactériologique des pneumopathies acquises sous ventilation mécanique

Pneumonia is usually suspected when clinical symptoms of infection are associated with the development of a new radiographic infiltrate. Nevertheless, these criteria are of poor specificity and can be misleading, yielding to over-diagnosis and then to an unneeded antimicrobial therapy. Several clinical, radiological and biological tools have been developed with the hope to improve the diagnostic accuracy. This review discusses some of the non microbiological means which could be used by the intensivist during the difficult diagnostic process of ventilator-associated pneumonia.

Usefulness of procalcitonin in the early detection of infection after thoracic surgery

The twofold aim of this prospective clinical study was to assess the accuracy of procalcitonin as a marker of postoperative infection after thoracic surgery and to compare it with C-reactive protein. Procalcitonin and C-reactive protein concentrations, clinical symptoms of infection and systemic inflammation were recorded preoperatively and 5 days postoperatively in 157 patients undergoing the following procedures: 52 wedge resections, 28 pneumonectomies and 77 lobectomies (or bilobectomies). Patients were classified as non-infected or infected according to predefined criteria. In non-infected patients (n=132), procalcitonin peaked on day 1 and C-reactive protein, on day 2. The procalcitonin value was significantly higher in patients having undergone a pneumonectomy (0.73+/-0.78 versus 0.54+/-0.25 ng/mL for lobectomy and 0.50+/-0.35 ng/mL for wedge resection; P=0.04). The mean value of procalcitonin was significantly higher in patients with postoperative infection (n=25) than in those with no postoperative infection (3.6+/-5.5 versus 0.63+/-0.62 ng/mL; P=0.0001). The onset of infection most frequently occurred on postoperative day 2 (43% of patients); maximum procalcitonin and C-reactive protein concentrations most frequently appeared on postoperative day 1 (56% of patients) and day 2 (63% of patients), respectively. The best cutoff value for detection of infection with procalcitonin was 1 ng/mL and with C-reactive protein, 100mg/L. Comparing the area under the Receiver Operating Characteristic curves, procalcitonin was better than C-reactive protein for detecting postoperative infection (0.92 versus 0.66; P<0.0001). Procalcitonin can be used as a reliable diagnostic parameter to detect and to monitor infectious complications in the postoperative period after thoracic surgery, especially in patients felt to be at higher risk (SIRS). It provides more information about the course of the disease than C-reactive protein does, and can be detected before the occurrence of clinical infection.

Panton valentine leukocidin (PVL) toxin positive MRSA strains isolated from companion animals

Methicillin-resistant Staphylococcus aureus (MRSA) is a highly pathogenic multiple-drug resistant (MDR) microorganism that has recently become more prevalent in the community. It has been found that MRSA strains can also contain genes that encode the panton valentine leukocidin toxin (PVL). The PVL toxin has been shown to be responsible for many of the severe clinical symptoms of infection with MRSA, such as furunculosis, severe necrotizing pneumonia, and necrotic lesions of the skin and soft tissues. The aim of this study was to determine the presence of the S. aureus PVL toxin genes (lukS-PV and lukF-PV) in MRSA strains isolated from companion animals. Eleven MRSA isolates, from a total of 23 tested, were shown to possess the mecA gene and the PVL toxin genes. Pulsed-field gel electrophoresis showed that the 11 PVL toxin positive MRSA strains were highly clonal.

Modeling the Development of Acquired Clinical Immunity to Plasmodium falciparum Malaria

Individuals living in regions where malaria is endemic develop an acquired immunity to malaria which enables them to remain asymptomatic while still carrying parasites. Field studies indicate that cumulative exposure to a variety of diverse Plasmodium parasites is required for the transition from symptomatic to asymptomatic malaria. This study used a simulation model of the within-host dynamics of P. falciparum to investigate the development of acquired clinical immunity under different transmission conditions and levels of parasite diversity. Antibodies developed to P. falciparum erythrocyte membrane protein 1 (PfEMP1), a clonally variant molecule, were assumed to be a key human immunological response to P. falciparum infection, along with responses to clonally conserved but polymorphic antigens. The time to the development of clinical immunity was found to be proportional to parasite diversity and inversely proportional to transmission intensity. The effect of early termination of symptomatic infections by chemotherapy was investigated and found not to inhibit the host's ability to develop acquired immunity. However, the time required to achieve this state was approximately double that compared to when no treatment was administered. This study demonstrates that an immune response primarily targeted against PfEMP1 has the ability to reduce clinical symptoms of infections irrespective of whether treatment is administered, supporting its role in the development of acquired clinical immunity. The results also illustrate a novel use for simulation models of P. falciparum infections, investigation of the influence of intervention strategies on the development of naturally acquired clinical immunity.

Multiple leucocyte activation markers to detect neonatal infection.

Diagnosis of congenital or neonatal infection is often based on clinical signs. However, clinical symptoms of infections may not be specific, and for this reason early diagnosis is often determined on results of laboratory tests, which may not currently be adequate. A more reliable method of detection of infection may be the demonstration of activated lymphocytes, which can be conducted rapidly and before the isolation of the infected organism. We have shown that detection of up-regulation of CD45RO, an activated/memory isoform of CD45 present on T cells, provides a reasonably sensitive screening test for neonatal infection. We also showed that dual expression of CD45RA/CD45RO was up-regulated early during the infective process in neonates with documented infection. However, other leucocytes are also activated during the infective process. To improve the sensitivity of the neonatal infection screening test and to identify the types of leucocytes involved in the immune response to the infective organism, we studied further the up-regulation of a comprehensive range of surface activation markers on T cells, monocytes and natural killer (NK) cells from a group of 17 newborn patients with positive culture, a group of 40 possibly infected patients based on clinical signs and a control group. 'Normal' ranges were established for each activation marker for each leucocyte subset from 1 to 7 and 7-14-day-old newborns <35 weeks' gestation and 35-40 weeks' gestation. There was a significant increase in the percentage of T cells expressing CD25 in the peripheral blood from infants at 2 weeks of age. Expression of HLA-DR on T cells, CD25 and CD69 on monocytes and HLA-DR on NK cells was also increased significantly in the peripheral blood from infants at 2 weeks of age and may reflect a maturation of these functional surface molecules. Up-regulation of CD69 on NK cells was the most sensitive marker for neonatal sepsis (positive in 13/16 patients). CD69 and CD25 expression was increased significantly on T cells in 11/17 and 10/17 patients, respectively. A combination of CD45RA/CD45RO and CD45RO identified 11/16 infected patients. Measurement of CD69 expression on NK cells with CD45RA, CD45RO, CD25 and CD69 expression on T cells resulted in a significant increase in at least two leucocyte activation markers from infected patients. In conclusion, this is the first report of the up-regulation of CD69 on NK cells as a sensitive marker of neonatal infection. A combination of this marker with CD45RA, CD45RO, CD25 and CD69 expression on peripheral blood derived T cells is the most sensitive and specific for neonatal infection.