Effects of antibiotic class on the macrophage inflammatory response to Streptococcus pneumoniae

Thymidine starvation promotes c-di-AMP-dependent inflammation during pathogenic bacterial infection

Antimicrobials can impact bacterial physiology and host immunity with negative treatment outcomes. Extensive exposure to antifolate antibiotics promotes thymidine-dependent Staphylococcus aureus small colony variants (TD-SCVs), commonly associated with worse clinical outcomes. We show that antibiotic-mediated disruption of thymidine synthesis promotes elevated levels of the bacterial second messenger cyclic di-AMP (c-di-AMP), consequently inducing host STING activation and inflammation. An initial antibiotic screen in Firmicutes revealed that c-di-AMP production was largely driven by antifolate antibiotics targeting dihydrofolate reductase (DHFR), which promotes folate regeneration required for thymidine biosynthesis. Additionally, TD-SCVs exhibited excessive c-di-AMP production and STING activation in a thymidine-dependent manner. Murine lung infection with TD-SCVs revealed STING-dependent elevation of proinflammatory cytokines, causing higher airway neutrophil infiltration and activation compared with normal-colony S. aureus and hemin-dependent SCVs. Collectively, our results suggest that thymidine metabolism disruption in Firmicutes leads to elevated c-di-AMP-mediated STING-dependent inflammation, with potential impacts on antibiotic usage and infection outcomes.

Prophylactic Topical Treatment for EGFR Inhibitor-Induced Papulopustular Rash: A Randomized Clinical Trial

BACKGROUND

The incidence of epidermal growth factor receptor inhibitor (EGFRI)-induced papulopustular rash is 60-85%.

OBJECTIVE

To investigate prophylactic topical treatment for EGFRI-induced rash.

METHODS

A single-center, randomized, double-blind, placebo-controlled trial. Adult cancer patients initiating treatment with EGFRIs were randomized to receive facial topical treatment with chloramphenicol 3% + prednisolone 0.5% (CHL-PRED) ointment, chloramphenicol 3% (CHL) ointment, or aqua cream (AQUA). The primary end points were the incidence of ≥grade 3 rash using the Common Terminology Criteria for Adverse Events (CTCAE), on days 14 and 30. A subanalysis was conducted for incidence of a protocol-specified significant rash, defined as ≥10 facial papulopustular lesions.

RESULTS

The per-protocol analysis on day 14 included 69 patients, who received CHL-PRED (21), CHL (23), or AQUA (25). The incidence of CTCAE ≥grade 3 rash was not statistically significant between arms; however, the incidence of the protocol-specified significant rash was: CHL-PRED 14%, CHL 39%, and AQUA 48% (p = 0.03, CHL-PRED vs. AQUA). At 30 days, the CTCAE ≥grade 3 incidence was similar, but the incidences of protocol-specified significant rash were 6%, 16%, and 43% (p = 0.03, CHL-PRED vs. AQUA). No significant differences were found between CHL and CHL-PRED and between CHL and AQUA.

CONCLUSIONS

Prophylactic topical CHL-PRED was efficacious when compared to AQUA, in the treatment of EGFRI-induced facial papulopustular rash.

Evaluation of the proinflammatory effects of contaminated bathing water

Contaminated marine bathing water has been reported to adversely affect human health. Our data demonstrated a correlation between total endotoxin (lipopolysaccharide; LPS) levels and degree of contamination of marine bathing waters. To assess the potential health implications of LPS present in marine bathing waters, the inflammation-inducing potency of water samples collected at different time points at multiple sampling sites were assessed using a cell culture-based assay. The numbers of fecal indicator bacteria (FIB) were also examined in the same samples. Water samples were used to stimulate two cell culture models: (1) a novel non-transformed continuously growing murine cell line Max Plank Institute (MPI) characteristic of alveolar macrophages and (2) human MonoMac 6 monocyte cell line. The inflammatory potential of the samples was assessed by measuring the release of inflammatory cytokines. The presence of high levels of LPS in contaminated bathing water led to induction of inflammatory response from our in vitro cell-based bioassays suggesting its potential health impact. This finding introduces an in vitro culture assay that reflects the level of LPS in water samples. These observations further promote previous finding that LPS is a reliable surrogate biomarker for fecal contamination of bathing water.

Early-Onset Neonatal Sepsis

Despite the great progress made in neonatal and perinatal medicine over the last couple of decades, sepsis remains one of the main causes of morbidity and mortality. Sepsis in pediatric population was defined at the Pediatric Sepsis Consensus Conference in 2005. There is still no consensus on the definition of neonatal sepsis. Neonatal sepsis is a sepsis that occurs in the neonatal period. According to the time of occurrence, neonatal sepsis can be of early onset, when it occurs within the first 72 hours of birth and results from vertical transmission, and of late onset, in which the source of infection is found most often in the environment and occurs after the third day of life. The most common causes of early-onset sepsis are Group B Streptococcus (GBS) and E. coli. Risk factors can be mother-related and newborn-related. Clinical symptoms and signs of sepsis are quite unspecific. The dysfunction of different organs may imitate sepsis. On the other hand, infectious and non-infectious factors may exist simultaneously. The start of the antimicrobial therapy in any newborn with suspected sepsis should not be delayed. Pentoxifylline may have potential benefits in preterm newborns with sepsis. The only proven intervention that has been shown to reduce the risk of early-onset neonatal sepsis is intrapartum intravenous antibiotic administration to prevent GBS infection. It is still a great challenge to discontinue antibiotic treatment in non-infected newborns as soon as possible, because any extended antibiotic use may later be associated with other pathological conditions.

Immunomodulation to Prevent or Treat Neonatal Sepsis: Past, Present, and Future

Despite continued advances in neonatal medicine, sepsis remains a leading cause of death worldwide in neonatal intensive care units. The clinical presentation of sepsis in neonates varies markedly from that in older children and adults, and distinct acute inflammatory responses results in age-specific inflammatory and protective immune response to infection. This review first provides an overview of the neonatal immune system, then covers current mainstream, and experimental preventive and adjuvant therapies in neonatal sepsis. We also discuss how the distinct physiology of the perinatal period shapes early life immune responses and review strategies to reduce neonatal sepsis-related morbidity and mortality. A summary of studies that characterize immune ontogeny and neonatal sepsis is presented, followed by discussion of clinical trials assessing interventions such as breast milk, lactoferrin, probiotics, and pentoxifylline. Finally, we critically appraise future treatment options such as stem cell therapy, other antimicrobial protein and peptides, and targeting of pattern recognition receptors in an effort to prevent and/or treat sepsis in this highly vulnerable neonatal population.

Combination therapy with ampicillin and azithromycin improved outcomes in a mouse model of group B streptococcal sepsis

BACKGROUND

Evidence suggests that β-lactam monotherapy of streptococcal infections may incite stronger inflammation and is inferior to combination therapy with macrolides. We hypothesized that use of macrolides alone or in combination with a β-lactam for group B streptococcal (GBS) sepsis would improve outcomes by reducing inflammation.

METHODS

TNF-α was measured from supernatants of RAW 264.7 cells stimulated with GBS isolates, in presence of four treatment regimens: ampicillin alone, azithromycin alone, or combination of azithromycin plus ampicillin. Mouse model of GBS sepsis was developed and treated with same four regimens. Clinical sepsis scores were monitored; serum cytokines (TNF-α, IL-6, IL-10) and chemokines (MIP-1α) were measured at the end.

RESULTS

GBS isolates exposed to azithromycin or combination (compared to ampicillin alone) stimulated less TNF production in vitro. In the murine sepsis model, mortality was lower along with decreased sepsis scores in mice treated with combination therapy. Mean serum IL-6 was lower in mice treated with azithromycin alone (66±52 pg/ml) or combination of ampicillin plus azithromycin (52±22 pg/ml) compared to ampicillin alone (260±160 pg/ml) (p<0.005).

CONCLUSIONS

Combination therapy of ampicillin+azithromycin improved outcomes in a murine GBS sepsis model; this therapeutic approach deserves additional study.

Isoniazid-induced control of Mycobacterium tuberculosis by primary human cells requires interleukin-1 receptor and tumor necrosis factor

Proinflammatory cytokines are critical mediators that control Mycobacterium tuberculosis (Mtb) growth during active tuberculosis (ATB). To further inhibit bacterial proliferation in diseased individuals, drug inhibitors of cell wall synthesis such as isoniazid (INH) are employed. However, whether INH presents an indirect effect on bacterial growth by regulating host cytokines during ATB is not well known. To examine this hypothesis, we used an in vitro human granuloma system generated with primary leukocytes from healthy donors adapted to model ATB. Intense Mtb proliferation in cell cultures was associated with monocyte/macrophage activation and secretion of IL-1β and TNF. Treatment with INH significantly reduced Mtb survival, but altered neither T-cell-mediated Mtb killing, nor production of IL-1β and TNF. However, blockade of both IL-1R1 and TNF signaling rescued INH-induced killing, suggesting synergistic roles of these cytokines in mediating control of Mtb proliferation. Additionally, mycobacterial killing by INH was highly dependent upon drug activation by the pathogen catalase-peroxidase KatG and involved a host PI3K-dependent pathway. Finally, experiments using coinfected (KatG-mutated and H37Rv strains) cells suggested that active INH does not directly enhance host-mediated killing of Mtb. Our results thus indicate that Mtb-stimulated host IL-1 and TNF have potential roles in TB chemotherapy.

Azithromycin Inhibits Macrophage Tumor Necrosis Factor Secretion in Response to Both Azithromycin-Susceptible and Azithromycin-Resistant Pneumococci

We studied the effect of azithromycin (AZM) on macrophage responses to pneumococci. We found that exposure of pneumococci to AZM led to reduced tumor necrosis factor (TNF) secretion by macrophages; this effect was observed in response to both AZM-susceptible and AZM-resistant (AZM-R) pneumococci.

Combination therapy with ampicillin and azithromycin in an experimental pneumococcal pneumonia is bactericidal and effective in down regulating inflammation in mice

Objectives

Emergence of multidrug resistance among Streptococcus pneumoniae (SP), has limited the available options used to treat infections caused by this organism. The objective of this study was to compare the role of monotherapy and combination therapy with ampicillin (AMP) and azithromycin (AZM) in eradicating bacterial burden and down regulating lung inflammation in a murine experimental pneumococcal infection model.

Methods

Balb/C mice were infected with 10⁶ CFU of SP. Treatments with intravenous ampicillin (200 mg/kg) and azithromycin (50 mg/kg) either alone or in combination was initiated 18 h post infection, animals were sacrificed from 0 – 6 h after initiation of treatment. AMP and AZM were quantified in serum by microbiological assay. Levels of TNF-α, IFN-γ IL-6, and IL-10 in serum and in lungs, along with myeloperoxidase, inflammatory cell count in broncho alveolar lavage fluid, COX-2 and histopathological changes in lungs were estimated.

Results

Combination therapy down regulated lung inflammation and accelerated bacterial clearance. This approach also significantly decreased TNF-α, IFN-γ, IL-6 and increased IL-10 level in serum and lungs along with decreased myeloperoxidase, pulmonary vascular permeability, inflammatory cell numbers and COX-2 levels in lungs.

Conclusions

Combinatorial therapy resulted in comparable bactericidal activity against the multi-drug resistant isolate and may represent an alternative dosing strategy, which may help to alleviate problems with pneumococcal pneumonia.

Role of bacterial components in macrophage activation by the LAC and MW2 strains of community-associated, methicillin-resistant Staphylococcus aureus

We tested the contribution of four staphylococcal components - PSM-α, PSM-β, δ-toxin, and PVL - in triggering macrophage secretion of tumor necrosis factor (TNF) and interleukins 6 (IL-6) and 12 (IL-12) by two prominent, circulating strains of community-associated, methicillin-resistant Staphylococcus aureus (CA-MRSA): LAC, USA300; MW2, USA400. RAW 264.7 murine macrophages were stimulated with live, antibiotic-exposed bacteria, and cytokine secretion was quantitated in supernatants. Deletion of PSM-α expression in LAC led to >50% reduction in macrophage TNF and IL-6 secretion and a 20% reduction in IL-12 secretion, while PSM-α deletion in MW2 did not significantly reduce macrophage TNF secretion but resulted in a 15-20% reduction in IL-6 and IL-12 secretion. Deletion of δ-toxin in either strain led to more than 50% reduction in macrophage IL-6 secretion and smaller reductions in macrophage TNF and IL-12 secretion (8-25%). Our data implicate both PSM-α and δ-toxin in stimulating macrophage cytokine responses to CA-MRSA bacteria.

Mathematical model of a three-stage innate immune response to a pneumococcal lung infection

Pneumococcal pneumonia is a leading cause of death and a major source of human morbidity. The initial immune response plays a central role in determining the course and outcome of pneumococcal disease. We combine bacterial titer measurements from mice infected with Streptococcus pneumoniae with mathematical modeling to investigate the coordination of immune responses and the effects of initial inoculum on outcome. To evaluate the contributions of individual components, we systematically build a mathematical model from three subsystems that describe the succession of defensive cells in the lung: resident alveolar macrophages, neutrophils and monocyte-derived macrophages. The alveolar macrophage response, which can be modeled by a single differential equation, can by itself rapidly clear small initial numbers of pneumococci. Extending the model to include the neutrophil response required additional equations for recruitment cytokines and host cell status and damage. With these dynamics, two outcomes can be predicted: bacterial clearance or sustained bacterial growth. Finally, a model including monocyte-derived macrophage recruitment by neutrophils suggests that sustained bacterial growth is possible even in their presence. Our model quantifies the contributions of cytotoxicity and immune-mediated damage in pneumococcal pathogenesis.

Does radiographic evidence of prior pulmonary tubercular infection influence the choice of empiric antibiotics for community-acquired pneumonia in a tuberculosis-endemic area?

BACKGROUND/PURPOSE

Recent medical literature suggests that use of fluoroquinolones (FQs) might be associated with the delayed diagnosis of pulmonary tuberculosis (TB). The purpose of this study was to assess the impact of radiographic evidence of prior pulmonary TB infection on empiric antibiotic choice in cases of community-acquired pneumonia (CAP), as well as the effect of antibiotic regimens on clinical outcome.

METHODS

A total of 280 patients with CAP between 1 May and 31 December 2007 were included in the study and their medical records were retrospectively reviewed. Patients were divided into two groups: those receiving FQs (FQ group) or those receiving β-lactam-based regimens (β-lactam group). Their demographic data, underlying diseases, clinical features, diseases severity and outcomes were compared.

RESULTS

Radiographic evidence of a previous pulmonary TB infection (odds ratio = 3.507, 95% confidence interval = 1.422-8.645; p = 0.006) was an independent factor associated with β-lactam-based regimens. Patients with a modified pneumonia severity index (mPSI) category V were more likely to receive FQ therapy (odds ratio = 2.53, 95% confidence interval = 1.140-5.615; p = 0.022). Of the patients with mPSI category V, the 14-day mortality rate of those in the β-lactam group was significantly lower than that of those in the FQ group (0%vs. 23%, respectively; p = 0.044).

CONCLUSION

Radiographic evidence of a previous pulmonary TB infection and a lower mPSI score increases the probability of the selection of a β-lactam-based regimen for the treatment of CAP.

Sphingosine kinase-1 (SphK-1) regulates Mycobacterium smegmatis infection in macrophages

Sphingosine kinase-1 is known to mediate Mycobacterium smegmatis induced inflammatory responses in macrophages, but its role in controlling infection has not been reported to date. We aimed to unravel the significance of SphK-1 in controlling M. smegmatis infection in RAW 264.7 macrophages. Our results demonstrated for the first time that selective inhibition of SphK-1 by either D, L threo dihydrosphingosine (DHS; a competitive inhibitor of Sphk-1) or Sphk-1 siRNA rendered RAW macrophages sensitive to M. smegmatis infection. This was due to the reduction in the expression of iNOs, p38, pp-38, late phagosomal marker, LAMP-2 and stabilization of the RelA (pp-65) subunit of NF-kappaB. This led to a reduction in the generation of NO and secretion of TNF-alpha in infected macrophages. Congruently, overexpression of SphK-1 conferred resistance in macrophages to infection which was due to enhancement in the generation of NO and expression of iNOs, pp38 and LAMP-2. In addition, our results also unraveled a novel regulation of p38MAPK by SphK-1 during M. smegmatis infection and generation of NO in macrophages. Enhanced NO generation and expression of iNOs in SphK-1++ infected macrophages demonstrated their M-1(bright) phenotype of these macrophages. These findings thus suggested a novel antimycobacterial role of SphK-1 in macrophages.

Short-term rifampicin pretreatment reduces inflammation and neuronal cell death in a rabbit model of bacterial meningitis

OBJECTIVE

In bacterial meningitis, severe systemic and local inflammation causes long-term impairment and death of affected patients. The current antibiotic therapy relies on cell wall-active beta-lactam antibiotics, which rapidly sterilize the cerebrospinal fluid (CSF). However, beta-lactams inhibit cell wall synthesis, induce bacteriolysis, and thereby evoke a sudden release of high amounts of toxic and proinflammatory bacterial products. Because tissue damage in bacterial meningitis is the result of bacterial toxins and the inflammatory host response, any reduction of free bacterial compounds promises to prevent neuronal damage.

DESIGN

In vitro experiments and randomized prospective animal study.

SETTING

University research laboratories.

SUBJECTS

Streptococcus pneumoniae broth cultures and New Zealand White rabbits.

INTERVENTIONS

We evaluated a concept to improve bacterial meningitis therapy in which a short-term pretreatment with the protein synthesis-inhibiting antibiotic rifampicin precedes the standard antibiotic therapy with ceftriaxone. First, logarithmically growing pneumococcal cultures were subdivided and exposed to different antibiotics. Then, rabbits suffering from pneumococcal meningitis were randomized to receive rifampicin pretreatment or ceftriaxone alone.

MEASUREMENTS AND MAIN RESULTS

In pneumococcal cultures, quantitative immunoblotting and real-time polymerase chain reaction revealed a reduced release of pneumolysin and bacterial DNA by rifampicin pretreatment for 30 minutes in comparison with ceftriaxone treatment alone. In vivo, a 1-hour rifampicin pretreatment reduced the release of bacterial products and attenuated the inflammatory host response, as demonstrated by decreased CSF levels of prostaglandin E2 and total protein and increased glucose CSF/plasma ratios. Rifampicin pretreatment reduced infection-associated neuronal apoptotic cell loss compared with ceftriaxone-treated controls.

CONCLUSIONS

A short-term pretreatment with rifampicin reduced the beta-lactam-induced release of deleterious bacterial products, attenuated inflammation, and thereby decreased neuronal cell loss in experimental bacterial meningitis. This concept has the potential to reduce inflammation-associated neuronal injury in bacterial meningitis and should be evaluated in a clinical trial.

Treatment with protein synthesis inhibitors improves outcomes of secondary bacterial pneumonia after influenza

Pneumonia occurring as a secondary infection after influenza is a major cause of excess morbidity and mortality, despite the availability and use of antibiotics active against Streptococcus pneumoniae. We hypothesized that the use of a bacteriostatic protein synthesis inhibitor would improve outcomes by reducing the inflammatory response. BALB/cJ mice infected with influenza virus and superinfected with S. pneumoniae were treated with either the cell-wall-active antibiotic ampicillin or the protein synthesis inhibitor clindamycin or azithromycin. In the model, ampicillin therapy performed significantly worse (survival rate, 56%) than (1) clindamycin therapy used either alone (82%) or in combination with ampicillin (80%) and (2) azithromycin (92%). Improved survival appeared to be mediated by decreased inflammation manifested as lower levels of inflammatory cells and proinflammatory cytokines in the lungs and by observation of less-severe histopathologic findings. These data suggest that beta-lactam therapy may not be optimal as a first-line treatment for community-acquired pneumonia when it follows influenza.

Improving therapeutic strategies for secondary bacterial pneumonia following influenza

Secondary bacterial pneumonia following influenza is an old problem, which is re-emerging. Despite rapid advances in our armamentarium of antimicrobials, the case-fatality rate for this frequent complication of influenza remains high. In some settings, common treatment options may actually contribute to poor outcomes, as rapid lysis of pathogenic bacteria on the backdrop of an activated immune system responding to influenza may lead to inflammatory damage in the lung. An understanding of the inter-related contributions of the antecedent viral infection, the invading bacteria and the host immune response is necessary to formulate an appropriate therapeutic approach. Prevention and resolution of these fulminant infections will require new approaches, including alternate treatment strategies, combination therapies targeting several aspects of the pathogenic process and, potentially, immunomodulation. In the not-so-distant future, strategies aimed at disarming pathogens without eliminating them may be more effective than our current treatment paradigms.

Comparison of beta-lactam and macrolide combination therapy versus fluoroquinolone monotherapy in hospitalized Veterans Affairs patients with community-acquired pneumonia

Data comparing the treatment outcomes of the two most frequently recommended empirical antibiotic regimens for community-acquired pneumonia (CAP)--combination therapy with an extended-spectrum beta-lactam and a macrolide (BL+M) or fluoroquinolone (F) monotherapy--for patients with severe CAP are sparse. The purpose of this study was to compare empirical BL+M combination therapy with F monotherapy for Veterans Affairs (VA) patients with severe CAP. This retrospective study included patients with CAP who received empirical therapy with BL+M or F between October 1999 and May 2003 in the Upstate New York VA Network. Outcome measures were 14-day mortality, 30-day mortality, and length of hospital stay (LOS). Severe CAP was defined as a class V pneumonia severity index (PSI). During the study period, 261 patients received BL+M and 254 received F. Disease severity was similar for the two treatment groups at admission, and the presence of tachycardia was the only difference noted. For PSI class V patients, there were lower 14-day and 30-day mortality rates with BL+M than with F (14-day rates, 8.2% versus 26.8% [P = 0.02]; 30-day rates, 18.4% versus 36.6% [P = 0.05]). No differences in mortality between treatment groups were noted for the lower PSI classes. The overall median LOS was significantly longer for the BL+M combination group than for the F monotherapy group (6.0 days versus 5.0 days, respectively [P = 0.01]), but no difference in LOS was noted among PSI class V patients. Our study showed that improved outcomes may be realized with BL+M in cases of severe CAP. A randomized clinical study is warranted based on these results.

Adjuvant TACE inhibitor treatment improves the outcome of TLR2-/- mice with experimental pneumococcal meningitis

Background

Streptococcus (S.) pneumoniae meningitis has a high lethality despite antibiotic treatment. Inflammation is a major pathogenetic factor, which is unresponsive to antibiotics. Therefore adjunctive therapies with antiinflammatory compounds have been developed. TNF484 is a TNF-alpha converting enzyme (TACE) inhibitor and has been found efficacious in experimental meningitis. Toll-like receptor 2 (TLR2) contributes to host response in pneumococcal meningitis by enhancing bacterial clearing and downmodulating inflammation. In this study, TNF484 was applied in mice, which lacked TLR2 and exhibited a strong meningeal inflammation.

Methods

10³ CFU S. pneumoniae serotype 3 was inoculated subarachnoidally into C57BL/6 wild type (wt) mice or TLR2^-/-, CD14^-/- and CD14^-/-/TLR2^-/- mice. Severity of disease and survival was followed over 9 days. Response to antibiotics (80 mg/kg ceftriaxone i.p. for 5 days) and/or TACE inhibitor treatment (1 mg/kg s.c. twice daily for 4 days) was evaluated. Animals were sacrificed after 12, 24, and 48 h for analysis of bacterial load in cerebrospinal fluid (CSF) and brain and for TNF and leukocyte measurements in CSF.

Results

TLR2^-/- mice were significantly sicker than the other mouse strains 24 h after infection. All knockout mice showed higher disease severity after 48 h and died earlier than wt mice. TNF release into CSF was significantly more elevated in TLR2^-/- than in the other strains after 24 h. Brain bacterial numbers were significantly higher in all knockout than wt mice after 24 h. Modulation of outcome by antibiotic and TACE inhibitor treatment was evaluated. With antibiotic therapy all wt, CD14^-/- and TLR2^-/-/CD14^-/- mice, but only 79% of TLR2^-/- mice, were rescued. TACE inhibitor treatment alone did not rescue, but prolonged survival in wt mice, and in TLR2^-/- and CD14^-/- mice to the values observed in untreated wt mice. By combined antibiotic and TACE inhibitor treatment 95% of TLR2^-/- mice were rescued.

Conclusion

During pneumococcal meningitis strong inflammation in TLR2-deficiency was associated with incomplete responsiveness to antibiotics and complete response to combined antibiotic and TACE inhibitor treatment. TACE inhibitor treatment offers a promising adjuvant therapeutic strategy in pneumococcal meningitis.

Group B streptococci exposed to rifampin or clindamycin (versus ampicillin or cefotaxime) stimulate reduced production of inflammatory mediators by murine macrophages

Streptococcus agalactiae (group B Streptococcus, GBS) is an important cause of sepsis and meningitis in neonates, and excessive production of the inflammatory mediators tumor necrosis factor (TNF) and nitric oxide (NO) causes tissue injury during severe infections. We hypothesized that exposure of GBS to different antimicrobial agents would affect the magnitude of the macrophage inflammatory response to this organism. We stimulated RAW 264.7 murine macrophages with a type-Ia GBS isolate in the presence of ampicillin, cefotaxime, rifampin, clindamycin, or gentamicin, singly or in combination. We found that GBS exposed to rifampin or clindamycin (versus beta-lactam antibiotics) stimulated less TNF secretion and inducible nitric oxide synthase (iNOS) protein accumulation in RAW 264.7 cells. Furthermore, GBS exposed to combinations of antibiotics that included a protein synthesis inhibitor stimulated less macrophage TNF and iNOS production than did organisms exposed to beta-lactam antibiotics singly or in combination. We conclude that exposure of GBS to rifampin or clindamycin leads to a less pronounced macrophage inflammatory mediator response than does exposure of the organism to cell wall-active antibiotics.

Comparative effects of ciprofloxacin and ceftazidime on cytokine production in patients with severe sepsis caused by gram-negative bacteria

In the present study the effect of ciprofloxacin versus ceftazidime on concentrations of pro- and anti-inflammatory cytokines in the sera of patients with severe sepsis was evaluated. The study included 58 previously healthy patients suffering from severe sepsis caused by gram-negative bacteria, treated with either ciprofloxacin or ceftazidime after thorough clinical and microbiological evaluation and followed up for clinical outcome. Levels of the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-1b (IL-1b), IL-6, and IL-8 and of the anti-inflammatory cytokine IL-10, as well as of IL-1 receptor antagonist and soluble TNF receptors I and II, in serum were measured at baseline and 24 and 48 h after the first antimicrobial dose. Mean SAPS-II scores, development of septic shock, and mortality rates were similar in the two groups (43.2 +/- 9.2, 21.4%, and 14.3% in the ceftazidime group versus 49.8 +/- 11.3, 20%, and 13.3% in the ciprofloxacin group). Serum TNF-alpha and IL-6 levels at 24 and 48 h were significantly lower in the ciprofloxacin group, while the IL-10/TNF-alpha ratio was significantly higher, than those for the ceftazidime group. Among patients with high baseline TNF-alpha levels, there were significant increases in the IL-10/TNF-alpha ratio at both 24 and 48 h over that at admission for the ciprofloxacin group, while no differences were noted in the ceftazidime group. These results indicate that ciprofloxacin may have an immunomodulatory effect on septic patients by attenuating the proinflammatory response, while there is no evidence that differences in the cytokines measured have any impact on the final outcome.

Protein synthesis inhibiting clindamycin improves outcome in a mouse model of Staphylococcus aureus sepsis compared with the cell wall active ceftriaxone

OBJECTIVE

The release of proinflammatory components from bacteria depends on the mode of action of the antibacterial therapy used. We studied whether this influences mortality in experimental sepsis.

DESIGN

In a lethal murine model of Staphylococcus aureus sepsis, animals were randomly assigned to receive the protein synthesis inhibitor clindamycin (CLI) or the beta-lactam ceftriaxone (CRO).

SETTING

Therapy was introduced subcutaneously 5 hrs after intraperitoneal injection of 10 colony forming units of S. aureus American Type Culture Collection 29213 and was continued every 8 hrs for 3 days.

MEASUREMENTS AND RESULTS

Survival was higher in mice receiving CLI (29/50 animals [58%]) than in mice receiving CRO (16/50 animals [32%]; p =.015). Mice treated with CRO died earlier than mice receiving CLI (p =.002). Eight hours after the first antibiotic dose, the motor performance of mice receiving CRO had deteriorated more than it did for mice receiving CLI (p =.009). Higher levels of tumor necrosis factor-alpha were measured in serum (p =.027) and peritoneal fluid (p =.001) of CRO-treated mice. In vitro, CLI released smaller amounts of staphylococcal enterotoxin A than CRO.

CONCLUSIONS

Antibiotic treatment of Gram-positive sepsis with a protein synthesis inhibitor decreases morbidity and mortality compared with a bacteriolytic compound. This may be caused by a reduction of the concentrations of proinflammatory/toxic bacterial components and cytokines.

Antibiotic induced endotoxin release and clinical sepsis: a review

Sepsis and peritonitis have not lost much of their danger for patients. The mortality rate in peritonitis has only marginally decreased during the last 30 years despite aggressive surgical and sophisticated intensive care treatment. In intra-abdominal infection and peritonitis source control remains the mainstay of treatment, although general principles and denominators of successful source control need to be established. Endotoxin has been recognized as a major player in the pathogenesis of sepsis and its significance in clinical disease has been investigated in clinical studies for more than 20 years. Since the Sixties there is a growing interest in the effect of antibiotics and other compounds on the release of endotoxin. The effect of antibiotics on the release of endotoxin and inflammatory parameters, e.g., cytokines, remains to be clarified despite a growing body of in-vitro studies, animal studies and a few clinical studies. The purpose of this review is to evaluate the evidence of endotoxin release in clinical studies and the effect that antibiotic treatment may have in-vitro, in-vivo and in clinical studies on endotoxin and cytokine release. In-vitro antibiotic-induced endotoxin release may depend on antibiotic class, presence of serum, type of organism, site of antibiotic action and Gram-stain. Endotoxin release may be different in late or early lysis, proportional to the number of killed pathogens. Morphology of bacteria may have an impact on endotoxin release and phagocytosis. Antibiotic-treated animals may show higher endotoxin levels with a higher survival rate than untreated animals. Plasma endotoxin may increase despite decreasing bacteremia. There may be a similar killing rate by different antibiotics but a difference in endotoxin release. Intestinal endotoxin does not necessarily correlate to the level of gram-negative bacteria. However, the alteration of the gut content by pretreatment may be associated with reduced endotoxemia and increased survival. Antibiotic-induced endotoxin release may be different depending on the type of infection, the location of infection, the virulence of strains, Gram-stain, mode of application and dosage of antibiotic. Different antibiotics may induce the release of different forms of endotoxin which may be lethal for sensitized animals. The combination of antibiotics with inhibitors of endotoxin or the pro-inflammatory response may be responsible for increased survival by decrease of endotoxin release. The clinical significance of antibiotic-induced endotoxin release is documented only in a few clinical disorders, e.g., meningitis, urosepsis. The difference in endotoxin release by PBP 2-specific antibiotics, e.g., imipenem, and PBP 3-specific antibiotics, e.g., ceftazidime, may not be visible in each study. Patients with increased multi-organ failure (MOF) scores may profit from treatment with antibiotics known to decrease endotoxin. In conclusion, the clinical significance of antibiotic-induced endotoxin release remains to be clarified. Type of pathogen and its virulence may be more important than recently suggested. gram-positive pathogens were just recently recognized as an important factor for the development of the host response. In case of fever of unknown origin in intensive care patients either failure of treatment, e.g., failure of source control in intra-abdominal infection, or a side effect of antibiotic treatment, e.g., endotoxin release, should be considered as a cause of the fever.