P. Speelman

Once versus thrice daily gentamicin in patients with serious infections

Aminoglycosides are usually given in two or three divided doses. A once-daily regimen might be more effective and less toxic. We have conducted a randomised trial in consecutive patients with serious infections for whom an aminoglycoside seemed warranted. Exclusion criteria were neutropenia or severely impaired renal function. 123 patients were enrolled. For efficacy analysis only those patients were considered in whom treatment with the aminoglycoside was not stopped within 72 h (n = 67); toxicity was analysed on patients receiving aminoglycosides for more than 48 h and not using other nephrotoxic medication (n = 85). Gentamicin 4 mg/kg every day (OD) or gentamicin 1.33 mg/kg three times daily (MD) (with dose-reduction in case of renal dysfunction) were given intravenously. In almost all patients intravenous amoxycillin 1 g every 6 h was also started. Baseline characteristics were comparable in both arms. A good clinical response was observed in 32/35 (91%) of the OD and in 25/32 (78%) in the MD group (difference 13%, 95% confidence interval -6.4% to +26.9%). 2 patients in each group died with uncontrolled infection. An insufficient bacteriological response (persistent positive cultures, resistance, or superinfection) was observed in 2 patients with OD and 3 patients with MD. In patients treated for more than 48 h duration of therapy and mean doses were 7.0 days (1590 mg) and 7.4 days (1672 mg) in OD and MD respectively. Mean first serum trough/peak levels were 0.6/10.2 mg/L and 1.4/5.2 mg/L. Nephrotoxicity (a rise in serum creatinine of 45 mumol/L or more) developed in 2/40 (5%) in OD and 11/45 (24%) in MD (p = 0.016). Risk factors for nephrotoxicity were duration of therapy and baseline creatinine clearance rate. High-tone audiometry was performed when possible; no significant differences were found in hearing loss (3/12 and 3/11) or prodromal signs of ototoxicity (5/12 and 4/11). A once-daily dosing regimen of gentamicin is at least as effective as and is less nephrotoxic than more frequent dosing.

Urokinase Receptor Is Necessary for Adequate Host Defense Against Pneumococcal Pneumonia

Cell recruitment is a multistep process regulated by cytokines, chemokines, and growth factors. Previous work has indicated that the urokinase plasminogen activator receptor (uPAR) may also play a role in this mechanism, presumably by an interaction with the β2 integrin CD11b/CD18. Indeed, an essential role of uPAR in neutrophil recruitment during pulmonary infection has been demonstrated for β2 integrin-dependent respiratory pathogens. We investigated the role of uPAR and urokinase plasminogen activator (uPA) during pneumonia caused by a β2 integrin-independent respiratory pathogen, Streptococcus pneumoniae. uPAR-deficient (uPAR−/−), uPA-deficient (uPA−/−), and wild-type (Wt) mice were intranasally inoculated with 105 CFU S. pneumoniae. uPAR−/− mice showed reduced granulocyte accumulation in alveoli and lungs when compared with Wt mice, which was associated with more S. pneumoniae CFU in lungs, enhanced dissemination of the infection, and a reduced survival. In contrast, uPA−/− mice showed enhanced host defense, with more neutrophil influx and less pneumococci in the lungs compared with Wt mice. These data suggest that uPAR is necessary for adequate recruitment of neutrophils into the alveoli and lungs during pneumonia caused by S. pneumoniae, a pathogen eliciting a β2 integrin-independent inflammatory response. This function is even more pronounced when uPAR is unoccupied by uPA.

Serum concentrations of cytokines in patients with active tuberculosis (TB) and after treatment

During TB cytokines play a role in host defence. To determine the cytokine pattern during various disease stages of TB, serum levels of IL‐12, interferon‐gamma (IFN‐γ), IL‐4, IL‐6 and IL‐10 were measured in 81 patients with active TB, 15 patients during therapy and 26 patients after anti‐tuberculous therapy as well as in 16 persons who had been in close contact with smear‐positive TB and in 17 healthy controls. IFN‐γ was elevated during active TB when compared with healthy controls, declining during and after treatment. IL‐12 (p40 and p70) serum levels were not significantly higher in patients with active TB compared with any of the other groups. IL‐4 levels were low in all groups. IL‐6 and IL‐10 serum levels were elevated in patients with active TB and during treatment. In patients with active TB serum levels of IFN‐γ and IL‐6 were higher in patients with fever, anorexia and malaise. IL‐12 levels were higher in patients with a positive smear. Cytokine levels did not correlate with localization of TB (pulmonary versus extrapulmonary), or skin test positivity. Cytokines directing a Th1 response (IL‐12) or a Th2 response (IL‐4) were not elevated in sera of this large group of patients with pulmonary and extrapulmonary TB. In patients with active TB, cytokines that were elevated in serum were IFN‐γ, IL‐6 and IL‐10.

Clinical relevance of antibiotic-induced endotoxin release.

Considerable mortality is associated with gram-negative infections, especially when they are complicated by shock (45). Although appropriate antibiotic treatment significantly reduces this mortality (45), it was already known in the early days of antibiotic treatment that fatal vasomotor collapse may occur after administration of a loading dose of chloramphenicol for typhoid fever (13). James Reilly hypothesized that the adverse clinical effects that were associated with destruction of the typhoid bacilli could be caused by an overwhelming release of endotoxin. He subsequently advised that one should start with a low dose of antibiotics: frappez doucement (hit gently) instead of frappez fort et vite (hit vigorously) (13). During the last 10 years a renewed interest in the possible deleterious effects of liberation of endotoxin (lipopolysaccharide [LPS]) during bacterial cell death has emerged. In this minireview, we review the current knowledge of the mechanisms of antibiotic-induced endotoxin release as well as their possible clinical implications.

Assessment of splenic function.

Hyposplenic patients are at risk of overwhelming post-splenectomy infection (OPSI), which carries mortality of up to 70%. Therefore, preventive measures are warranted. However, patients with diminished splenic function are difficult to identify. In this review we discuss immunological, haematological and scintigraphic parameters that can be used to measure splenic function. IgM memory B cells are a potential parameter for assessing splenic function; however, more studies are necessary for its validation. Detection of Howell–Jolly bodies does not reflect splenic function accurately, whereas determining the percentage of pitted erythrocytes is a well-evaluated method and seems a good first-line investigation for assessing splenic function. When assessing spleen function, 99mTc-labelled, heat-altered, autologous erythrocyte scintigraphy with multimodality single photon emission computed tomography (SPECT)-CT technology is the best approach, as all facets of splenic function are evaluated. In conclusion, although scintigraphic methods are most reliable, they are not suitable for screening large populations. We therefore recommend using the percentage of pitted erythrocytes, albeit suboptimal, as a first-line investigation and subsequently confirming abnormal readings by means of scintigraphy. More studies evaluating the value of potentially new markers are needed.

A Single Oral Dose of Thalidomide Enhances the Capacity of Lymphocytes to Secrete Gamma Interferon in Healthy Humans

ABSTRACT Thalidomide is increasingly being used as adjuvant therapy for patients with mycobacterial and human immunodeficiency virus (HIV) infections. The T-helper (Th)1 cytokine–Th2 cytokine balance critically determines the outcomes of these diseases. To obtain insight into the effect of thalidomide on the capacity of lymphocytes to produce Th1 and Th2 cytokines, six healthy volunteers received an oral dose (400 mg) of thalidomide. Before and at 3, 6, and 24 h after ingestion of thalidomide, peripheral blood mononuclear cells (PBMCs) were isolated and stimulated for 24 h with the T-cell stimulant staphylococcal enterotoxin B (SEB) or anti-CD3/CD28. In all six volunteers ingestion of thalidomide was associated with enhanced SEB- and anti-CD3/CD28-induced production of the Th1 cytokine gamma interferon (P < 0.05) and a decrease in the level of anti-CD3/CD28-induced interleukin-5 (IL-5) production (P < 0.05). The levels of IL-2 (Th1) and IL-4 (Th2) released remained unchanged. These changes were accompanied by an increase in the amount of IL-12p40 released by the PBMCs 6 h after ingestion of thalidomide (P < 0.05). Thus, a single oral dose of thalidomide causes a Th1-type response in healthy humans. This finding offers a potential explanation for the positive effect of thalidomide in patients with mycobacterial and HIV infections.

Serum Concentrations of Lipopolysaccharide Activity-Modulating Proteins during Tuberculosis

Lipopolysaccharide (LPS) is the principal stimulator of host defense against gram-negative bacteria. LPS-binding protein (LBP), bactericidal/permeability-increasing protein (BPI), and soluble CD14 (sCD14) bind LPS and regulate its toxicity. Lipoarabinomannan, a cell wall component of Mycobacterium tuberculosis, resembles LPS with respect to induction of inflammatory responses through recognition by LBP and sCD14. LBP, BPI, and sCD14 were measured in serum of 124 patients with tuberculosis in various stages of disease, in persons who had been in close contact with patients with contagious pulmonary tuberculosis, and in healthy controls. Levels of these LPS toxicity-regulating proteins were elevated in patients with active tuberculosis compared with those in contacts and controls and declined during treatment. The levels of LBP and sCD14 were higher in patients with fever and anorexia. LPS-regulating proteins may play a role in host defense during tuberculosis, presumably through interaction with lipoarabinomannan.

Sequential measurements of chemokines in urosepsis and experimental endotoxemia.

Chemokines are a superfamily of small chemotactic proteins. While increased levels of interleukin-8 have been measured in serum and urine during urinary tract infection, little is known about other chemokines in this condition. Monocyte chemoattractant protein (MCP)–1, macrophage inflammatory protein (MIP)–1α, MIP-1β and interferon-γ inducible protein (IP)–10 were measured in 30 patients with culture-proven urosepsis during a 3-day follow-up and in 11 healthy humans after intravenous injection of endotoxin (4 ng/kg). Urine and serum levels of MCP-1, MIP-1β, and IP-10, but not of MIP-1α, were elevated in patients on admission, and decreased after initiation of antibiotic treatment. Endotoxin administration to healthy subjects induced increases in plasma and urine concentrations of all four chemokines. These data indicate that clinical and experimental gram-negative infection in humans is associated with enhanced production of chemokines that act mainly on mononuclear cells and that these chemokines are at least in part locally produced.

Endotoxin release and cytokine production in acute and chronic meningococcaemia

Chronic meningococcaemia is a relatively benign manifestation of meningococcal disease. Whether bacterial virulence factors are responsible for this benign course has not been studied. We compared the in vitro endotoxin‐liberating ability and cytokine‐inducing potential of 31 Neisseria meningitidis isolates obtained from children with acute septic shock with that of nine isolates obtained from patients with chronic meningococcaemia and 12 isolates obtained from carriers with respiratory symptoms. The median endotoxin level released in vitro after 3u2003h of incubation was significantly higher for isolates causing septic shock compared with isolates from the other two groups (Pu2003=u20030.01 and 0.02, Mann–Whitney test). This was not explained by differences in bacterial growth rate in vitro. The median IL‐6 levels in whole blood ex vivo after 4u2003h of incubation were also significantly lower for isolates causing chronic meningococcaemia (Pu2003=u20030.04, Mann–Whitney test). The endotoxin and cytokine levels measured on admission in the 31 children with acute meningococcal septic shock showed a 1000‐fold variation. No relationship was established between the amount of endotoxin released by the causative microorganisms in vitro and the endotoxin or cytokine levels in the corresponding 31 children. These results suggest a diminished bacterial virulence for isolates causing chronic meningococcaemia. However, other factors than the endotoxin‐releasing potential of the microorganism involved are responsible for the wide variation in endotoxin and therefore cytokine levels in patients with acute meningococcal septic shock.

Anti-Tumor Necrosis Factor Antibody Impairs the Therapeutic Effect of Ceftriaxone in Murine Pneumococcal Pneumonia

Treatments aimed at inhibition of tumor necrosis factor (TNF) in patients with sepsis have been unsuccessful. Up to 50% of such patients suffer from pneumonia. To determine the effect that treatment with anti-TNF has on pneumococcal pneumonia, mice were intranasally inoculated with Streptococcus pneumoniae and, 25 h later, treated with 1 of the following: (1) control antibody, (2) anti-TNF, (3) ceftriaxone (CEF) with control antibody, or (4) CEF with anti-TNF. In the absence of treatment with CEF, mice displayed high bacterial loads in lungs, and all of these mice died within 5 days after inoculation. Anti-TNF did not influence these outcomes. In contrast, 60% of mice treated with CEF alone survived. Anti-TNF administered together with CEF reduced survival to 40% and was associated with enhanced bacterial outgrowth. These data suggest that treatment with anti-TNF impairs the therapeutic efficacy of CEF during pneumococcal pneumonia.