Differential metabolic host response to pathogens associated with community-acquired pneumonia

Background

Metabolic changes induced by the host immune response to pathogens found in patients with community-acquired pneumonia (CAP) may provide insight into its pathogenesis. In this study, we characterized differences in the host metabolic response to common CAP-associated pathogens.

Method

Targeted metabolomic profiling was performed on serum samples obtained from hospitalized CAP patients (n = 119) at admission. We quantified 347 unique metabolites across multiple biochemical classes, including amines, acylcarnitines, and signaling lipids. We evaluated if unique associations between metabolite levels and specific CAP-associated pathogens could be identified.

Results

Several acylcarnitines were found to be elevated in C. burnetii and herpes simplex virus and lowered in M. pneumoniae as compared to other pathogens. Phenylalanine and kynurenine were found elevated in L. pneumophila as compared to other pathogens. S-methylcysteine was elevated in patients with M. pneumoniae, and these patients also showed lowered cortisol levels in comparison to almost all other pathogens. For the herpes simplex virus, we observed a unique elevation of eicosanoids and several amines. Many lysophosphatidylcholines showed an altered profile in C. burnetii versus S. pneumoniae, L. pneumophila, and respiratory syncytial virus. Finally, phosphatidylcholines were negatively affected by the influenza virus in comparison to S. pneumoniae.

Conclusions

In this exploratory analysis, metabolites from different biochemical classes were found to be altered in serum samples from patients with different CAP-associated pathogens, which may be used for hypothesis generation in studies on differences in pathogen host response and pathogenesis of CAP.

Latent class analysis-based subgroups and response to corticosteroids in hospitalised community-acquired pneumonia patients: a validation study

In patients with community-acquired pneumonia, LCA can identify robust prognostic subgroups based on clinical and inflammatory parameters. Yet, these subgroups have not proven robust in predicting response to adjunctive dexamethasone treatment. https://bit.ly/3O5eaxz.

Overweight and obesity are not associated with worse clinical outcomes in COVID-19 patients treated with fixed-dose 6 mg dexamethasone

Objective

A fixed 6 mg dexamethasone dose for 10 days is the standard treatment for all hospitalised COVID-19 patients who require supplemental oxygen. Yet, the pharmacokinetic properties of dexamethasone can lead to diminishing systemic dexamethasone exposure with increasing body mass index (BMI). The present study examines whether this translates to overweight and obesity being associated with worse clinical outcomes, defined as ICU admission or in hospital death, in COVID-19 patients treated with fixed-dose dexamethasone.

Methods

We conducted a single centre retrospective cohort study in COVID-19 patients who were admitted to a non-ICU ward and were treated with dexamethasone (6 mg once daily for a maximum of ten days) between June 2020 and January 2021. Univariable and multivariable logistic regression analyses were conducted to assess the association between BMI-categories and an unfavourable clinical course (ICU admission and/or in hospital death). Analyses were adjusted for age, comorbidities, inflammatory status, and oxygen requirement at admission. For reference, similar analyses were repeated in a cohort of patients hospitalised before dexamethasone was introduced (March 2020 through May 2020).

Results

In patients treated with dexamethasone (n = 385) an unfavourable clinical course was most prevalent in patients with normal weight (BMI < 25) compared to patients with overweight (BMI 25–30) and patients with obesity (BMI ≥ 30) with percentages of 33, 26 and 21% respectively. In multivariable analyses, there was no association between BMI-category and an unfavourable clinical course (respectively with aORs of 0.81 (0.43–1.53) and 0.61 (0.30–1.27) with normal weight as reference). In the reference cohort (n = 249) the opposite was observed with an unfavourable clinical course being most prevalent in patients with overweight (39% vs 28%; aOR 2.17 (0.99–4.76)). In both cohorts, CRP level at admission was higher and lymphocyte count was lower in patients with normal weight compared to patients with obesity.

Conclusions

Overweight and obesity are not associated with an unfavourable clinical course in COVID-19 patients admitted to a non-ICU ward and treated with 6 mg dexamethasone once daily.

Neutrophil count, lymphocyte count and neutrophil-to-lymphocyte ratio in relation to response to adjunctive dexamethasone treatment in community-acquired pneumonia

BACKGROUND

It is hypothesised that community-acquired pneumonia (CAP) patients with more severe disease or inflammation might benefit more from adjunctive corticosteroid treatment. Neutrophil count, lymphocyte count and neutrophil-lymphocyte ratio (NLR) have been associated with inflammation and disease severity in CAP. We investigated the interaction between these parameters and adjunctive dexamethasone effects on clinical outcomes in CAP.

METHODS

We conducted a post hoc analysis of the randomised placebo-controlled Santeon-CAP trial (n = 401), which showed a positive effect of adjunctive oral dexamethasone on length of stay (LOS) in CAP patients. White blood cell (WBC) count, neutrophil count, NLR (highest tertile vs. lowest two tertiles) and lymphocyte count (lowest tertile vs. highest two tertiles) were examined as potential effect modifiers of treatment with dexamethasone on LOS (primary outcome) and ICU-admission, 30-day mortality and hospital readmission.

RESULTS

WBC differential counts were available for 354 patients. The effect of dexamethasone on LOS was more pronounced in high WBC count, high neutrophil count or high NLR subgroups (difference in median LOS of 2 days versus zero days in the reference subgroups, p for interaction < 0.05). There was no effect modification for the other outcomes. Patients with low WBC and low neutrophil counts did not benefit from dexamethasone, while hospital readmission rate was higher in those treated with dexamethasone (6% vs. 11%).

CONCLUSIONS

WBC count and/or neutrophil might be easily available biomarkers to guide selection of CAP patients who are more likely to benefit from adjunctive dexamethasone treatment. Future prospective trials are needed to confirm this predictive potential.

Community-acquired pneumonia subgroups and differential response to corticosteroids: a secondary analysis of controlled studies

Background

Latent class analysis (LCA) has identified subgroups with meaningful treatment implications in acute respiratory distress syndrome. We performed a secondary analysis of three studies to assess whether LCA can identify clinically distinct subgroups in community-acquired pneumonia (CAP) and whether the treatment effect of adjunctive corticosteroids differs between subgroups.

Methods

LCA was performed on baseline clinical and biomarker data from the Ovidius trial (n=304) and the Steroids in Pneumonia (STEP) trial (n=727), both randomised controlled trials investigating adjunctive corticosteroid treatment in CAP, and the observational TripleP cohort (n=201). Analyses were conducted independently in two cohorts (Ovidius–TripleP combined and the STEP trial). In both cohorts, differences in clinical outcomes and response to adjunctive corticosteroid treatment were examined between subgroups identified through LCA.

Results

A two-class model fitted both cohorts best. Class 2 patients had more signs of systemic inflammation compared to class 1. In both cohorts, length of stay was longer and in-hospital mortality rate was higher in class 2. In the Ovidius trial, corticosteroids reduced the median length of stay in class 2 (6.5 versus 9.5 days) but not in class 1 (p-value for interaction=0.02). In the STEP trial, there was no significant interaction for length of stay. We found no significant interaction between class assignment and adjunctive corticosteroid treatment for secondary outcomes.

Conclusions

In two independent cohorts, LCA identified two classes of CAP patients with different clinical characteristics and outcomes. Given the different response to adjunctive corticosteroids in the Ovidius trial, LCA might provide a useful basis to improve patient selection for future trials.

Latent class analysis of baseline clinical and biomarker data identified two distinct classes of patients with community-acquired pneumonia in two cohorts. In one cohort, the response to adjunctive corticosteroid treatment differed between classes.https://bit.ly/3ClR92L

Adjunctive treatment with oral dexamethasone in non-ICU patients hospitalised with community-acquired pneumonia: a randomised clinical trial

BACKGROUND

Adjunctive intravenous corticosteroid treatment has been shown to reduce length of stay (LOS) in adults hospitalised with community-acquired pneumonia (CAP). We aimed to assess the effect of oral dexamethasone on LOS and whether this effect is disease severity dependent.

METHODS

In this multicentre, stratified randomised, double-blind, placebo-controlled trial, immunocompetent adults with CAP were randomly assigned (1:1 ratio) to receive oral dexamethasone (6 mg once daily) or placebo for 4 days in four teaching hospitals in the Netherlands. Randomisation (blocks of four) was stratified by CAP severity (pneumonia severity index class I-III and IV-V). The primary outcome was LOS.

RESULTS

Between December 2012 and November 2018, 401 patients were randomised to receive dexamethasone (n=203) or placebo (n=198). Median LOS was shorter in the dexamethasone group (4.5 days, 95% CI 4.0-5.0 days) than in the placebo group (5.0 days, 95% CI 4.6-5.4 days; p=0.033). Within both CAP severity subgroups, differences in LOS between treatment groups were not statistically significant. The secondary ICU admission rate was lower in the dexamethasone arm (5 (3%) versus 14 (7%); p=0.030); 30-day mortality did not differ between groups. In the dexamethasone group the rate of hospital readmission tended to be higher (20 (10%) versus 9 (5%); p=0.051) and hyperglycaemia (14 (7%) versus 1 (1%); p=0.001) was more prevalent.

CONCLUSION

Oral dexamethasone reduced LOS and ICU admission rate in adults hospitalised with CAP. It remains unclear for which patients the risk-benefit ratio is optimal.

Chlorhexidine 0.5%/70% Alcohol and Iodine 1%/70% Alcohol Both Reduce Bacterial Load in Clean Foot Surgery: A Randomized, Controlled Trial

No consensus exists regarding which cleansing technique, solution, and concentration should be used in orthopedic surgery. The aim of this randomized, controlled trial was to compare the effect of chlorhexidine 0.5%/70% alcohol with iodine 1%/70% alcohol on lowering positive cultures before elective foot surgery and to study any wound complications, infections and allergic reactions. Consecutive patients ≥18 years of age scheduled for a hallux valgus correction or arthrodesis of the first metatarsophalangeal joint were included. Swabs were taken from 2 sites before and twice after preparing the skin and were quantitatively and qualitatively analyzed. The study group consisted of 49 patients with a mean age of 52.3 ± 14.4 (range 22 to 75) years of whom 42 (86%) were female. No significant differences were observed for positive cultures between the chlorhexidine (73%, 2%, and 12%) and iodine (68%, 7%, and 9%) group at any time point. Coagulase-negative staphylococci were the most commonly isolated micro-organisms found after skin preparation. Occasionally, Bacillus spp and Corynebacterium spp were cultured. The complication rate 2 weeks postoperatively was 0% in the chlorhexidine group versus 8.7% (n = 2) in the iodine group (delayed wound healing; p = .215). The complication rate at 6 weeks postoperatively was, respectively, 3.8% (n = 1) versus 4.3% (n = 1; both showed swelling and redness; p > .999). There was no significant difference in postoperative wound problems or infection rates between the 2 skin preparation solutions. Chlorhexidine 0.5%/70% alcohol and iodine 1%/70% alcohol both decreased the amount of positive cultures in elective foot surgery.

Inter-hospital variation in the utilization of diagnostics and their proportionality in the management of adult community-acquired pneumonia

BACKGROUND

Utilization of diagnostics and biomarkers are the second largest cost drivers in the management of patients hospitalized with community-acquired pneumonia (CAP). The present study aimed to systematically assess the inter-hospital variation in these cost drivers in relation to antibiotic use in CAP.

METHODS

Detailed resource utilization data from 300 patients who participated in a multicenter placebo-controlled trial investigating dexamethasone as adjunctive treatment for community-acquired pneumonia was grouped into 3 categories: clinical chemistry testing, radiological exams, and microbiological testing. Based on the identified top 5 items per category, average costs were calculated per category and per hospital. Antibiotic de-escalation at day 3 and secondary ICU admission were assessed as outcomes for proportionality of diagnostics use.

RESULTS

The mean costs for diagnostics varied between hospitals from 350 (SD 31) to 841 (SD 37) euro per patient (p < 0.001). This difference was primarily explained by variation in costs for microbiological testing (mean 195 vs. 726 euro per patient, p < 0.001). There was no difference in number of secondary ICU admissions but there was an inverse association between the costs of microbiological testing and level of antibiotic de-escalation. De-escalation occurred most frequently in the hospital with the lowest cost for microbiological testing (48% vs. 30%; p = 0.018). The latter hospital had an automated physician alert system in place to consider a timely iv-to-oral switch of antibiotics.

CONCLUSIONS

Large inter-hospital variation exists in resource utilization, mainly in microbiological diagnostics in the management of adult patients with community-acquired pneumonia. A counterintuitive inverse association between the magnitude of these costs and the amount of antibiotic de-escalation was found. Future studies about the optimal cost-effective set of microbiological testing for antimicrobial stewardship in pneumonia patients should acknowledge the interaction between testing, way of communication of results and triggered physician alert systems.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01743755.

PAI-1 Synthesis in the Human Hepatoma Cell Line Hep G2 Is Increased by Cytokines - Evidence that the Liver Contributes to Acute Phase Behaviour of PAI-1

The acute phase behaviour of the fast inhibitor of tissue-type plasminogen activator (PAI-1) in vivo has been attributed to increased synthesis by endothelial cells. However, most other acute phase proteins in vivo are synthesized in the liver, which process is regulated by cytokines and can be studied in the hepatoma derived cell line HepG2.

In this study, we investigated whether the synthesis of PAI-1 by HepG2 cells is regulated by the cytokines recombinant IL-1, rlL-6 and rTNF. Recombinant IL-1 and rTNF each increased PAI-1 synthesis by Hep G2 cells two to three fold, whereas rIL-6 hardly had an effect. Mixtures of rIL-1, rIL-6 and rTNF increased PAI-1 synthesis up to eleven fold. The effects observed were not due to non-specific effects on Hep G2 cell metabolism, since synthesis of alpha-2-antiplasmin was not effected by any of those cytokines, whereas fibrinogen synthesis was increased three to four fold by rIL-6, but was unaffected by rIL-1. Thus, our results demonstrate that synthesis of PAI-1 by Hep G2 cells is regulated by cytokines and implicate that the acute phase behaviour of PAI-1 in vivo at least in part may be due to an increased synthesis by the liver.

First human case of tick-borne encephalitis virus infection acquired in the Netherlands, July 2016

In July 2016, the first autochthonous case of tick-borne encephalitis was diagnosed in the Netherlands, five days after a report that tick-borne encephalitis virus (TBEV) had been found in Dutch ticks. A person in their 60s without recent travel history suffered from neurological symptoms after a tick bite. TBEV serology was positive and the tick was positive in TBEV qRT-PCR. TBEV infection should be considered in patients with compatible symptoms in the Netherlands.

Dexamethasone and length of hospital stay in patients with community-acquired pneumonia: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Whether addition of corticosteroids to antibiotic treatment benefits patients with community-acquired pneumonia who are not in intensive care units is unclear. We aimed to assess effect of addition of dexamethasone on length of stay in this group, which might result in earlier resolution of pneumonia through dampening of systemic inflammation.

METHODS

In our double-blind, placebo-controlled trial, we randomly assigned adults aged 18 years or older with confirmed community-acquired pneumonia who presented to emergency departments of two teaching hospitals in the Netherlands to receive intravenous dexamethasone (5 mg once a day) or placebo for 4 days from admission. Patients were ineligible if they were immunocompromised, needed immediate transfer to an intensive-care unit, or were already receiving corticosteroids or immunosuppressive drugs. We randomly allocated patients on a one-to-one basis to treatment groups with a computerised randomisation allocation sequence in blocks of 20. The primary outcome was length of hospital stay in all enrolled patients. This study is registered with ClinicalTrials.gov, number NCT00471640.

FINDINGS

Between November, 2007, and September, 2010, we enrolled 304 patients and randomly allocated 153 to the placebo group and 151 to the dexamethasone group. 143 (47%) of 304 enrolled patients had pneumonia of pneumonia severity index class 4-5 (79 [52%] patients in the dexamethasone group and 64 [42%] controls). Median length of stay was 6·5 days (IQR 5·0-9·0) in the dexamethasone group compared with 7·5 days (5·3-11·5) in the placebo group (95% CI of difference in medians 0-2 days; p=0·0480). In-hospital mortality and severe adverse events were infrequent and rates did not differ between groups, although 67 (44%) of 151 patients in the dexamethasone group had hyperglycaemia compared with 35 (23%) of 153 controls (p<0·0001).

INTERPRETATION

Dexamethasone can reduce length of hospital stay when added to antibiotic treatment in non-immunocompromised patients with community-acquired pneumonia.

FUNDING

None.

Microbial evaluation of proton-pump inhibitors and the risk of pneumonia

Recent initiation of proton-pump inhibitor (PPI) treatment may increase the risk of community-acquired pneumonia (CAP), hypothetically by allowing colonisation of the oropharynx by gastrointestinal bacteria. The aim of this study was to assess the causal pathway by considering microbial aetiology of pneumonia and indications for initiation of PPI treatment. This was a population-based, case-control study with 430 cases with pneumonia and 1,720 matched controls. An elaborate diagnostic protocol was used to identify the causative microorganism of pneumonia. For patients recently starting PPI treatment, indications for treatment were assessed. Recent initiation of PPI treatment (<30 days) was associated with an increased risk of CAP (adjusted OR 3.1, 95% CI 1.4-7.1). Oropharyngeal bacteria were evenly distributed among current users, past users and nonusers of PPIs (p=0.41). Gastrointestinal bacteria were identified in only five (1.2%) patients with pneumonia (two current users and three nonusers). Excluding patients who were possibly prescribed PPI treatment for early symptoms of pneumonia (protopathic bias) did not alter the study findings. This study reaffirmed that use of PPIs is associated with an increased risk of CAP, especially when treatment has recently been started. Neither protopathic bias nor shifts in microbial aetiology seem to explain the association.

Clinical features predicting failure of pathogen identification in patients with community acquired pneumonia

Community acquired pneumonia (CAP) is caused by a variety of microorganisms. By identifying patients at risk for failure of pathogen identification, it is possible to make an early decision on the extent of diagnostic procedures to be performed. This is especially important in patients with severe CAP. The aim of this study was to identify these patients by using clinical and laboratory features. In 201 patients hospitalized for CAP, clinical and laboratory variables were collected. Pathogen identification was performed by culture of sputum and blood, urine antigen tests, polymerase chain reaction of sputum, serological testing and viral culture of the pharynx. In 128 patients a respiratory microorganism was identified. In both univariate and multivariate analysis, failure of pathogen identification was predicted by pre-hospital antibiotic therapy, a medical history of hypertension and a low C-reactive protein. We conclude that patients with pre-hospital antibiotic therapy, a medical history of hypertension and a relatively low C-reactive protein are at risk for failure of pathogen identification. These predictors should be confirmed in a larger population. Invasive testing in high-risk patients with CAP in the presence of these predictors should be considered at an early phase of hospitalization.

Prior outpatient antibiotic use as predictor for microbial aetiology of community-acquired pneumonia: hospital-based study

OBJECTIVE

The causative micro-organism in community-acquired pneumonia (CAP) is often difficult to predict. Different studies have examined chronic morbidity and clinical symptoms as predictors for microbial aetiology of pneumonia. The aim of our study was to assess whether prior outpatient antimicrobial treatment is predictive for determining the microbial aetiology of CAP.

METHODS

This was a hospital-based prospective observational study including all patients admitted with CAP between 1 October 2004 and 1 August 2006. Microbial investigations included sputum, blood culture, sputum PCR, antigen testing and serology. Exposure to antimicrobial drugs prior to hospital admission was ascertained through community pharmacy dispensing records. Multivariate logistic regression analysis was conducted to assess whether prior outpatient antimicrobial treatment is a predictor of microbial aetiology. Patient demographics, co-morbidities and pneumonia severity were considered to be other potential predictors.

RESULTS

Overall, 201 patients were included in the study. The microbial aetiology was determined in 64% of the patients. The five most prevalent pathogens were Streptococcus pneumoniae, Heamophilus influenzae, Legionella spp., Mycoplasma pneumoniae and Influenza virus A+B. Forty-seven of the patients (23%) had received initial antimicrobial treatment as outpatients. Multivariate analyses revealed that initial outpatient beta-lactam treatment was associated with a threefold increased chance of finding atypical pathogens and a threefold decreased probability of pneumococcal infection; the corresponding odds ratios were 3.51 (95% CI 1.25-9.99) and 0.30 (95% CI 0.10-0.90), respectively. Patients who received macrolides prior to hospitalisation had an increased probability of viral pneumonia.

CONCLUSION

Prior outpatient antimicrobial therapy has a predictive value in the diagnostic workup aimed at identifying the causative pathogen and planning corresponding antimicrobial treatment in patients hospitalised for pneumonia.

Occurrence of extended-spectrum betalactamases (ESBL) in Dutch hospitals

The prevalence of ESBL was determined among isolates of Escherichia coli (n = 571) and Klebsiella spp. (n = 196) collected during a 1-week study period in 8 university and 3 large regional laboratories all over the Netherlands. 18 isolates were positive for at least one of the screening tests used, i.e., VITEK-ESBL, E-test ESBL and MIC ratio of ceftazidime/ceftazidime-clavulanic acid, cefotaxime/cefotaxime-clavulanic acid. In 5 of these 18 putative ESBLs no betalactamase production was detectable. A TEM type was found in three E. coli and two Klebsiella spp. An SHV type was present in five Klebsiella spp. In one E. coli and one Klebsiella pneumoniae both enzymes were present. In one Klebsiella oxytoca neither of the two enzymes was present. Using PCR for both ESBL TEM and ESBL SHV, an SHV ESBL was found in one E. coli and four Klebsiella isolates. The mutations at position 238 and 240 were already described. In one E. coli isolate a TEM ESBL was found with three mutations, at position 21, 164 and 265. These mutations were already described in other ESBLs but not in this combination suggesting a new TEM ESBL. The overall prevalence of ESBL producing E. coli and Klebsiella spp. was less than 1% (6 out of 767).

Effectiveness of resins in neutralizing antibiotic activities in bactec plus Aerobic/F culture medium

Incorporating resins in blood culture media can effectively reduce the activities of several antibiotics. It was shown that the activities of some generally used antibiotics decreased by 80 to 90% within 2 h in Bactec Plus Aerobic/F resin-containing culture medium. Bactec vials containing resins were still found to be positive for bacteria when antibiotics were present. The addition of beta-lactamase shortened the detection time irrespective of the presence of resins.

Evaluation of a new identification system, Crystal Enteric/Non-Fermenter, for gram-negative bacilli

A total of 505 fermentative and 201 nonfermentative gram-negative bacilli, identified by conventional methods, were tested by the Crystal Enteric/Non-Fermenter ID kit and by the API 20E or API 20NE identification system. The overall correct results for fermenters were 92.9% by the Crystal kit and 89.1% by the API 20E system. The false identifications (genus and species incorrect) accounted for 3.1 and 7.1% for the Crystal and API systems, respectively. For nonfermenters, figures for correct identifications by the two systems were comparable (Crystal, 75.9%; API 20NE, 75.3%) while the API 20NE system gave twice as many incorrect results (13.8%) as Crystal (6.3%); however, Crystal failed to precisely identify several species included in a "miscellaneous" group. The Crystal Enteric/Non-Fermenter system is an easy-to-use kit which compares favorably with other commercial systems.

In vitro development and stability of tolerance to cloxacillin and vancomycin in Staphylococcus aureus

The stability of tolerance of Staphylococcus aureus during subculturing at 37 degrees C and development of this property after repeated exposure to cloxacillin or vancomycin were investigated in vitro. Four of five tolerant strains lost this property during repeated subculturing at 37 degrees C for 50 days. Conversely, tolerance emerged in two of four nontolerant strains after repeated cycles of exposure to 25 micrograms of cloxacillin/ml or 10 micrograms of vancomycin/ml alternating with growth in antibiotic-free medium. Previous in vivo exposure to cloxacillin did not enhance the development of tolerance in vitro. MICs of both cloxacillin and vancomycin did not change significantly during this procedure. Whether the conversion of nontolerant strains to the tolerant state can also occur during antibiotic exposure in treatment of patients remains to be determined.

Efficacy of ciprofloxacin in treatment and prophylaxis of experimental Staphylococcus aureus endocarditis caused by a cloxacillin-tolerant strain and its non-tolerant variant

The efficacy of ciprofloxacin in treatment and prophylaxis of Staphylococcus aureus endocarditis in rats infected with a strain tolerant to the standard anti-staphylococcal antibiotics cloxacillin, vancomycin and teicoplanin was compared with its non-tolerant variant. After 5 days of treatment with ciprofloxacin 30 mg/kg subcutaneously every 8 h bacterial densities in vegetations from animals infected with the tolerant and the non-tolerant strain were similar. Resistance to ciprofloxacin did not emerge in either strain of S. aureus during treatment. In prophylaxis experiments a single dose of ciprofloxacin (30 mg/kg) administered 30 min before bacterial challenge afforded almost full protection for both the tolerant and the non-tolerant strain. At a lower dose of 6 mg/kg the protective effect was less compared with the higher dose, but no difference in the proportion of sterile vegetations was found between the two strains. Thus tolerance influenced neither treatment nor prophylaxis with ciprofloxacin. For strains of S. aureus tolerant to the usual anti-staphylococcal antibiotics ciprofloxacin could be a useful alternative for the treatment of infections.

Role of tolerance in treatment and prophylaxis of experimental Staphylococcus aureus endocarditis with vancomycin, teicoplanin, and daptomycin

The role of Staphylococcus aureus tolerance in the treatment and prophylaxis of endocarditis in rats was investigated. The efficacies of vancomycin, teicoplanin, and daptomycin, alone and in combination with rifampin, were compared in rats with endocarditis infected with a tolerant strain of S. aureus and in rats with endocarditis infected with its nontolerant variant. In vitro the cloxacillin-tolerant strain was also tolerant to vancomycin and teicoplanin, but not to daptomycin. However, tolerance to these antibiotics did not influence the results of treatment of experimental S. aureus endocarditis. There was no difference in the bacterial densities in the vegetations of rats infected with either the tolerant or the nontolerant strain after 5 days of treatment with any of the antibiotic regimens. Of all antibiotics, daptomycin was the most effective in reducing bacterial numbers in vegetations. Combination of rifampin with vancomycin or teicoplanin improved the results of treatment for the tolerant as well as the nontolerant strains. Daptomycin was as effective alone as in combination with rifampin. In contrast, tolerance influenced the prophylactic effects of vancomycin and teicoplanin. The proportion of rats with sterile vegetations after prophylaxis with vancomycin or teicoplanin at a low dose was lower for those infected with the tolerant strain than for those infected with the nontolerant strain. A low dose of daptomycin was equally effective against the tolerant and the nontolerant strains. However, higher doses of all three antibiotics afforded almost full protection against both strains.

Paradoxical dose effect of continuously administered cloxacillin in treatment of tolerant Staphylococcus aureus endocarditis in rats

The efficacies of different doses of cloxacillin administered by continuous infusion were compared in the treatment of endocarditis in rats caused by a beta-lactam tolerant strain of Staphylococcus aureus and its non-tolerant variant. In-vitro killing of the tolerant strain was maximal at a concentration near the MIC, while at higher concentrations the rate of killing gradually decreased, a paradoxical effect, not found for the non-tolerant strain. During treatment of endocarditis caused by a tolerant strain, the reduction of bacterial numbers in the infected vegetations decreased significantly with increasing doses of cloxacillin. Thus for the tolerant strain a paradoxical dose effect was also apparent in vivo. For the non-tolerant strain this paradoxical effect was not found. Furthermore, continuous administration of cloxacillin was significantly less effective in reducing bacterial numbers in the vegetations for the tolerant strain than for the non-tolerant strain. The results of this study suggest that the phenomenon of tolerance, demonstrated in vitro, may have a significant influence on the outcome of treatment of S. aureus endocarditis with continuously administered cloxacillin, particularly when high doses of antibiotic are used.

Role of tolerance in cloxacillin prophylaxis of experimental Staphylococcus aureus endocarditis

The role of tolerance was investigated in the prophylaxis of Staphylococcus aureus endocarditis with cloxacillin in rats. The effect of a single dose of 500 mg/kg, two 80 mg/kg doses 3 h apart, and a single dose of 80 mg/kg, alone or in combination with a single dose of 4 mg of gentamicin/kg, were compared for a tolerant strain of S. aureus and its isogenic nontolerant variant. At all dosages, cloxacillin was significantly less effective in preventing endocarditis with the tolerant strain than with the nontolerant variant. With the high dose of cloxacillin or two successive lower doses, nearly complete protection could be obtained against the nontolerant strain. However, for the tolerant strain, only the combination of cloxacillin and gentamicin afforded almost complete protection. For the tolerant strain, no serum bactericidal activity was found at the time of bacterial challenge after an injection of any dose of cloxacillin. These results suggest that the in vitro phenomenon of tolerance may have relevance in vivo.

Role of tolerance in cloxacillin treatment of experimental Staphylococcus aureus endocarditis

The role of Staphylococcus aureus tolerance was investigated in endocarditis in rats. The efficacies of cloxacillin, gentamicin, and a combination of the two were compared for animals infected with a tolerant strain, its kill-sensitive variant, or a nonisogenic nontolerant strain of S. aureus. Cloxacillin was significantly less effective for treating the tolerant than for the nontolerant strains. The addition of gentamicin to cloxacillin reduced bacterial numbers in endocardial vegetations for the tolerant strain comparable to the reduction by cloxacillin alone for the nontolerant strains, but had no additional effect for the nontolerant strains. Isolates from animals infected with the tolerant or nontolerant strains during antibiotic treatment remained tolerant or nontolerant. These results show that the in vitro phenomenon of tolerance is relevant in vivo.

PAI-1 synthesis in the human hepatoma cell line HepG2 is increased by cytokines--evidence that the liver contributes to acute phase behaviour of PAI-1

The acute phase behaviour of the fast inhibitor of tissue-type plasminogen activator (PAI-1) in vivo has been attributed to increased synthesis by endothelial cells. However, most other acute phase proteins in vivo are synthesized in the liver, which process is regulated by cytokines and can be studied in the hepatoma derived cell line HepG2. In this study, we investigated whether the synthesis of PAI-1 by HepG2 cells is regulated by the cytokines recombinant IL-1, rIL-6 and rTNF. Recombinant IL-1 and rTNF each increased PAI-1 synthesis by HepG2 cells two to three fold, whereas rIL-6 hardly had an effect. Mixtures of rIL-1, rIL-6 and rTNF increased PAI-1 synthesis up to eleven fold. The effects observed were not due to non-specific effects on HepG2 cell metabolism, since synthesis of alpha-2-antiplasmin was not effected by any of those cytokines, whereas fibrinogen synthesis was increased three to four fold by rIL-6, but was unaffected by rIL-1. Thus, our results demonstrate that synthesis of PAI-1 by HepG2 cells is regulated by cytokines and implicate that the acute phase behaviour of PAI-1 in vivo at least in part may be due to an increased synthesis by the liver.