Increasing threat of Gram-positive bacterial infections in the intensive care unit setting

Rising Klebsiella pneumoniae Infections and Its Expanding Drug Resistance in the Intensive Care Unit of a Tertiary Healthcare Hospital, Saudi Arabia

Nosocomial infections caused by Klebsiella pneumoniae and other Gram-negative organisms have emerged as a significant health problem especially in intensive care units (ICU). This study aims to examine K. pneumoniae infections in the ICU of Aseer Central Hospital and to determine their antimicrobial susceptibility and their relationship to patients' clinical outcomes. This is a retrospective observational study done in a tertiary care center in the Aseer region in Saudi Arabia. The study spanned from January 2018 to December 2019. Demographic, microbiologic, and patient outcomes were collected from 276 patients with various infections. Identification of isolates and in vitro susceptibility to 32 antimicrobial agents were done by the Vitek 2 automated system (bioMérieux, Marcy-l'Étoile, France). Prevalence of K. pneumoniae bacteria, their susceptibility to antimicrobials, and effect on clinical outcome were studied. Two hundred seventy-six K. pneumoniae were recovered from ICU patients with various infections. K. pneumoniae isolates (n=276) were collected mainly from the respiratory tract (61%) and K. pneumoniae represented 39% of the major causal agents of ICU infections, followed by Acinetobacter spp. (30%), Pseudomonas aeruginosa (10.0%), Escherichia coli (7%), and others (14%). The mortality among the 276 ICU patients was 33.3%; K. pneumoniae was connected to 42% of the cases and 67% of the total deaths were between 50 and 90 years of age. K. pneumoniae demonstrated high sensitivity and hence can be recommended for in vivo treatment for tigecycline (81%), cefazolin (77.2%), colistin (64.9%), and to a lesser extent norfloxacin (60%) and imipenem (55.5%). High resistance was detected for ampicillin (100%), extended-spectrum β-lactamases-sulbactam (ESBL-SCM) (100%), piperacillin (100%), and ceftazidime (92.5%). Resistance to carbapenems was elevated in ertapenem (65.2%) and meropenem (61.7%). The increase of K. pneumoniae represents a threat to ICU patients, although K. pneumoniae infections were results rather than the causes, as it was connected to almost half of the ICU mortalities. Tigecycline alone or in combination with colistin on high-dose regimens could be a more effective therapy for treating carbapenem-resistant K. pneumoniae infections.

Antibiotic Prescribing in Response to Bacterial Isolates in the Intensive Care Unit

This study aimed to identify potential knowledge-performance gaps in antibiotic prescribing for bacterial isolates in the Intensive Care Unit (ICU) in order to guide the development of interventions such as antibiotic policies, decision support, and improved systems for communication between the laboratory and the bedside. A prospective observational cohort study of all patients admitted to a mixed medical/surgical ICU was undertaken over a six-month period in an Australian adult tertiary hospital. From a cohort of 524 patients, 108 had 303 isolates that were eligible for inclusion. Overall, 14.3% and 30.8% of sterile and non-sterile isolates respectively were associated with inadequate initial antibiotic therapy after identification of the bacteria. After sensitivity results were available inadequate directed therapy was observed in 4.0% and 21.3% of sterile and non-sterile isolates respectively. Problems were most commonly associated with isolates of Pseudomonas spp., Stenotrophomonas spp., Acinetobacter spp., S. aureus, enterococci and group III Enterobacteriaceae. Inadequate antibiotic therapy was found to be independently associated with prolonged length of ICU stay. Narrower spectrum antibiotic therapy was potentially available for 30% of isolates after sensitivity results were known. We conclude that there is scope to improve antibiotic prescribing in the ICU by providing clinicians with access to information regarding local susceptibility patterns and intrinsic resistance of bacteria, and spectra of antibiotic cover. Timely notification of laboratory results at the point of care may also facilitate improved prescribing performance.

The 2016 Garrod Lecture: The role of the healthcare epidemiologist in antimicrobial chemotherapy-a view from the USA

Antimicrobial chemotherapy now spans 80 years and four generations. The healthcare epidemiologist has an important role to play in this field. Efforts focus in three areas: (i) minimizing the transmission of antimicrobial-resistant bacteria in healthcare settings (infection control); (ii) optimizing use of currently available antibacterial drugs (antibiotic stewardship); and (iii) recognizing and responding to opportunities for new drug development. For each area, the epidemiologist provides data that address four practical questions-'What is the problem?', 'What should be done?', 'Is it being done?' and 'Is it working?'. A team approach is crucial to acting on the epidemiological data. Examples are presented to illustrate different roles of the epidemiologist, and tools and measures that have been developed to address some problems of current importance. Monitoring of quality, integrity and security of data remains a major focus. The epidemiologist will continue to have a key role in antimicrobial chemotherapy.

Occurrence and distribution of antibiotic-resistant bacteria and transfer of resistance genes in Lake Taihu

The overuse of antibiotics has accelerated antibiotic resistance in the natural environment, especially fresh water, generating a potential risk for public health around the world. In this study, antibiotic resistance in Lake Taihu was investigated and this was the first thorough data obtained through culture-dependent methods. High percentages of resistance to streptomycin and ampicillin among bacterial isolates were detected, followed by tetracycline and chloramphenicol. Especially high levels of ampicillin resistance in the western and northern regions were illustrated. Bacterial identification of the isolates selected for further study indicated the prevalence of some opportunistic pathogens and 62.0% of the 78 isolates exhibited multiple antibiotic resistance. The presence of ESBLs genes was in the following sequence: bla_TEM > bla_SHV > bla_CTMX and 38.5% of the isolates had a class I integrase gene. Of all tested strains, 80.8% were able to transfer antibiotic resistance through conjugation. We also concluded that some new families of human-associated ESBLs and AmpC genes can be found in natural environmental isolates. The prevalence of antibiotic resistance and the dissemination of transferable antibiotic resistance in bacterial isolates (especially in opportunistic pathogens) was alarming and clearly indicated the urgency of realizing the health risks of antibiotic resistance to human and animal populations who are dependent on Lake Taihu for water consumption.

Linezolid versus glycopeptide or beta-lactam for treatment of Gram-positive bacterial infections: meta-analysis of randomised controlled trials

Linezolid has been approved for the treatment of patients with infections caused by Gram-positive cocci that are resistant to traditionally used antibiotics, including glycopeptides. This oxazolidinone antibiotic has been reported to have excellent pharmacokinetics and effectiveness. We did a meta-analysis of randomised controlled trials (RCTs) to clarify whether linezolid is superior to glycopeptides or beta-lactams for the treatment of Gram-positive infections. 12 RCTs, involving 6093 patients, were included. Overall, with respect to treatment success, linezolid was more effective than glycopeptides or beta-lactams (odds ratio [OR] 1.41 [95% CI 1.11-1.81]). Mortality was similar between the groups (OR 0.97 [0.79-1.19]). Linezolid was more effective than comparators in patients with skin and soft-tissue infections (OR 1.67 [1.31-2.12]) and bacteraemia (OR 2.07 [1.13-3.78]). However, there was no difference in treatment success for patients with pneumonia (OR 1.03 [0.75-1.42]). Treatment with linezolid was not associated with more adverse effects in general (OR 1.40 [0.95-2.06]); however, thrombocytopenia was recorded more commonly in patients receiving linezolid (OR 11.72 [3.66-37.57]). Although linezolid is more effective than its comparators for the empirical treatment of selected patients, several points, such as the use of less potent antistaphylococcal beta-lactams, the same all-cause mortality, and the higher probability of thrombocytopenia, should be taken into account and may limit the use of linezolid to specific patient populations or infections that are difficult to treat with other antibiotics.

Lipopolysaccharide primes macrophages to increase nitric oxide production in response to Staphylococcus Aureus

Sepsis, the leading cause of death in intensive care units, is associated with overproduction of nitric oxide (NO). The mechanism concerning the NO production in the sepsis caused by both Gram-negative and Gram-positive bacteria is largely unknown. The present study examines the effect of lipopolysaccharide (LPS) on Staphylococcus aureus-induced NO production in macrophages. In the naïve murine macrophage cell line RAW264.7, heat-killed Staphylococcus aureus (HKSa) induced a significant NO production at a high concentration (100 microg/ml). However, pretreatment of the cells with increasing concentration of LPS (10-50 ng/ml) resulted in induction of NO production by HKSa even at the doses of 1 and 10 microg/ml. The expression of inducible NO synthase (iNOS) in response to HKSa was also enhanced by LPS pretreatment, suggesting that LPS priming NO production is due to the enhancement of iNOS expression. We examined whether protein kinase C (PKC), mitogen-activated protein kinases (MAPKs) and calcineurin signaling pathways are involved in the priming effects of LPS. It was found that the PKC inhibitor Gö6976, the p38 inhibitor SB203580 and the calcineurin inhibitor cyclosporine A significantly reversed the priming effects of LPS on HKSa-induced NO production and iNOS expression. In contrast, the ERK1/2 inhibitor PD98059 did not block the induction of priming by LPS. These data support the hypothesis that LPS primes macrophages for enhancement of HKSa-induced NO production, and indicate that PKC, p38 and calcineurin might be involved in the LPS-induced priming.

Differential regulation of lipopolysaccharide and Gram-positive bacteria induced cytokine and chemokine production in macrophages by Galpha(i) proteins

Heterotrimeric G(i) proteins play a role in signalling activated by lipopolysaccharide (LPS), Staphylococcus aureus (SA) and group B streptococci (GBS), leading to production of inflammatory mediators. We hypothesized that genetic deletion of G(i) proteins would alter cytokine and chemokine production induced by LPS, SA and GBS stimulation. LPS-induced, heat-killed SA-induced and heat-killed GBS-induced cytokine and chemokine production in peritoneal macrophages from wild-type (WT), Galpha(i2) (-/-) or Galpha(i1/3) (-/-) mice were investigated. LPS induced production of tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), IL-10 and interferon-gamma-inducible protein-10 (IP-10); SA induced TNF-alpha, and IL-1beta production; and GBS induced TNF-alpha, IL-6, IL-1beta, macrophage inflammatory protein-1alpha (MIP-1alpha) and keratinocyte chemoattract (KC) production were all decreased (P < 0.05) in Galpha(i2) (-/-) or Galpha(i1/3) (-/-) mice compared with WT mice. In contrast to the role of G(i) proteins as a positive regulator of mediators, LPS-induced production of MIP-1alpha and granulocyte-macrophage colony-stimulating factor (GM-CSF) were increased in macrophages from Galpha(i1/3) (-/-) mice, and SA-induced MIP-1alpha production was increased in both groups of Galpha(i) protein-depleted mice. LPS-induced production of KC and IL-1beta, SA-induced production of GM-CSF, KC and IP-10, and GBS-induced production of IL-10, GM-CSF and IP-10 were unchanged in macrophages from Galpha(i2) (-/-) or Galpha(i1/3) (-/-) mice compared with WT mice. These data suggest that G(i2) and G(i1/3) proteins are both involved and differentially regulate murine inflammatory cytokine and chemokine production in response to both LPS and Gram-positive microbial stimuli.

Development of a real-time Staphylococcus aureus and MRSA (SAM-) PCR for routine blood culture

The notification of "Gram-positive cocci, possibly staphylococcus" in a blood culture drawn from a seriously ill patient is responsible for a large amount of vancomycin prescribing in institutions where methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of bacteraemia. A duplex real-time TaqMan polymerase chain reaction targeting the species-specific nuc gene, and the mecA gene encoding methicillin-resistance, was developed as a tool for rapid identification and detection of S. aureus and methicillin-resistance, and optimised for immediate as-needs testing. Three different DNA extraction methods achieved varying DNA quality, with PCR inhibition the main problem. Serial blood cultures (n=120) identified as possible staphylococci on Gram stain from our clinical laboratory were examined. There was one false negative result for a methicillin-resistant Staphylococcus epidermidis, which was positive on repeat testing, and one false negative result due to DNA extraction failure for MRSA from peritoneal dialysate inoculated into blood culture medium. Sensitivity and specificity of 97% and 100%, respectively, were obtained for mecA; and sensitivity and specificity of 98% and 100%, respectively, for nuc. Detection of slow-growing coagulase-negative staphylococci as co-infecting strains may be reduced. The assay quickly and reliably identified S. aureus in mixed infection, and identified methicillin resistance in both S. epidermidis and S. aureus strains.

Superantigen-induced multiple organ dysfunction in a toxin-concentration-controlled and sequential parameter-monitored swine sepsis model

OBJECTIVE

In order to examine the biological activity of low-dose and continuously infused superantigen, and to establish a superantigen-induced multiple organ dysfunction animal model, several pathophysiological parameters were sequentially monitored in a toxin-concentration-controlled pig model.

METHODS

Anesthetized, mechanically ventilated and Swan-Ganz thermodilution catheter-inserted pigs were treated with toxic shock syndrome toxin-1 (TSST-1) by infusion at 2 microg/kg/h for 5 h. Monitoring was performed for both the infusion period and a subsequent 1-h post-infusion period.

RESULTS

The serum concentration of TSST-1 was controlled so as to elevate it to a level over 1000 pg/mL within 1 h of initiation of infusion, and then gradually increased further and reached a plateau of about 2500 pg/mL at 4h after initiation. The animals showed a significant increase in cardiac output, the intrapulmonary arteriovenous shunt ratio, and infiltration of white blood cells into the lung. Although the observed increase in pulmonary vascular resistance was not statistically significant, it did correlate with the reduction in white blood cell counts.

CONCLUSION

The superantigen TSST-1 plays an important role in the pathogenesis of Gram-positive bacterial sepsis by inducing multiple organ dysfunction. Thus, this model provides the first tool to allow the simultaneous examination of the serum toxin levels and other organ parameters in a time-course manner.

Nosocomial bacterial infections in Intensive Care Units. I: Organisms and mechanisms of antibiotic resistance

Hospital-acquired infection is an increasing problem in intensive care units, where the patients are more susceptible and the organisms often more resistant than in other environments. This review discusses the reasons for these phenomena and describes the mechanisms underlying antibiotic resistance and the common intensive care unit-acquired organisms.

TOLL-LIKE RECEPTOR 4 COUPLED GI PROTEIN SIGNALING PATHWAYS REGULATE EXTRACELLULAR SIGNAL-REGULATED KINASE PHOSPHORYLATION AND AP-1 ACTIVATION INDEPENDENT OF NFκB ACTIVATION

Previous studies have implicated heterotrimeric Gi proteins in signaling leading to inflammatory mediator production induced by lipopolysaccharide (LPS). TLR4 has recently been shown to play a central role in response to LPS activation. We hypothesized that Gi proteins are coupled to TLR4 activation of signaling pathways. To inhibit Gi protein function, human embryonic kidney (HEK) 293 cells or RAW 264.7 cells were pretreated with pertussis toxin (PTx), an inhibitor of receptor-Galphai interaction, or transfected with dominant negative Galphai3 (Galphai3dn) or Galphai2 minigene (an inhibitory carboxyl terminus of Galphai2) plasmid. The cells were subsequently transfected with constitutively active TLR4 (TLR4ca) plasmid or TLR4ca together with an NFkappaB or AP-1 reporter construct. TLR4ca transfection induced ERK 1/2 activation (157 +/- 14%, P < 0.01), AP-1 activation (4.0 +/- 0.2-fold, P < 0.01), and NFkappaB activation (8.1 +/- 0.4-fold, P < 0.01) compared with empty vector controls. Pretreatment with PTx inhibited TLR4ca-induced ERK 1/2 phosphorylation (30 +/- 7%, P < 0.05) and AP-1 activation (36 +/- 3%, P < 0.05) but did not inhibit NFkappaB activation. Cotransfection of TLR4ca with Galphai3dn or Galphai2 minigene also reduced TLR4ca-induced ERK 1/2 phosphorylation (34 +/- 10% and 33 +/- 5%, respectively, P < 0.05). Constitutively active Galphai2 and Galphai3 plasmids potentiated TLR4ca-induced ERK 1/2 phosphorylation (27 +/- 3% and 41 +/- 6%, respectively, P < 0.05). betaARK-ct plasmid, which inhibits the function of betagamma subunit of G protein, has no effect on TLR4ca-induced ERK 1/2 phosphorylation. These data support our hypothesis and provide the first evidence that Galphai-coupled signaling pathways are activated by TLR4. The TLR4-activated Galphai signaling pathway activates ERK 1/2 phosphorylation and AP-1 activation independently of TLR4-mediated signaling to NFkappaB activation.

Role of peroxisome proliferator-activated receptor-gamma in the protection afforded by 15-deoxydelta12,14 prostaglandin J2 against the multiple organ failure caused by endotoxin

OBJECTIVE

The cyclopentenone prostaglandin 15-deoxydelta-prostaglandin J2 (15 d-PGJ2) exerts potent anti-inflammatory effects in vivo, which are in part due to the activation of peroxisome proliferator-activated receptor (PPAR)-gamma. Here we investigate the effects of 15 d-PGJ2 on the multiple organ injury/dysfunction associated with severe endotoxemia.

DESIGN

Prospective, randomized study.

SETTING

University-based research laboratory.

SUBJECTS

Seventy anesthetized male Wistar rats.

INTERVENTIONS

Rats received either Escherichia coli lipopolysaccharide (endotoxin, 6 mg/kg intravenously) or vehicle (saline, 1 mL/kg intravenously). 15 d-PGJ2 (0.3 mg/kg intravenously) or vehicle (10% dimethyl sulfoxide) was administered 30 mins before endotoxin. The selective PPAR-gamma antagonist GW9662 (0.3 mg/kg intravenously) or its vehicle (10% dimethyl sulfoxide) was given 45 mins before endotoxin.

MEASUREMENTS AND MAIN RESULTS

Endotoxemia for 6 hrs increased serum concentrations of creatinine (indicator of renal dysfunction), aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, bilirubin (markers for hepatic injury and dysfunction), lipase (indicator of pancreatic injury), and creatine kinase (an indicator of neuromuscular skeletal muscle or cardiac injury). The potent PPAR-gamma agonist 15 d-PGJ2 attenuated the increases in the serum concentrations of these variables, indicating a protective effect of 15 d-PGJ2 against the multiple organ injury/dysfunction caused by endotoxin. The specific PPAR-gamma antagonist GW9662 reduced the protective effects afforded by 15 d-PGJ2. 15 d-PGJ2 did not affect the biphasic decrease in blood pressure or the increase in heart rate caused by endotoxemia.

CONCLUSIONS

The potent PPAR-gamma agonist 15 d-PGJ2 reduces the multiple organ injury and dysfunction, but not the hypotension, caused by endotoxin in the rat. The mechanisms of the protective effect of this cyclopentenone prostaglandin are--at least in part--PPAR-gamma dependent, as the protection afforded by 15 d-PGJ2 was reduced by the PPAR-gamma antagonist GW9662. We propose that 15 d-PGJ2 or other ligands for PPAR-gamma may be useful in treating organ injury associated with endotoxic shock.

Staphylococcus aureus and Lipopolysaccharide Induce Homologous Tolerance but Heterologous Priming: Role of Interferon-??

Lipopolysaccharide (LPS), the gram-negative bacterial cell wall component, induces tolerance to a secondary challenge of LPS in macrophages (Mphi) as evidenced by reduced inflammatory mediator production. However, it is uncertain if heat-killed (HK) gram-positive bacteria Staphylococcus aureus (Sa) can induce a similar tolerance and alter responses to LPS. We hypothesized that HKSa induces homologous tolerance and cross tolerance to LPS stimulation in human promonocytic THP-1 cells. We measured TNF-alpha, TxB2, and IFN-gamma production and the phosphorylation of p38, JNK, and ERK-1/2 in human promonocytic THP-1 cells. HKSa (10 microg/mL) significantly stimulated naive (nonpretreated) cell TNF-alpha (P<0.05) and TxB2 production (P<0.05). However, HKSa-pretreated cells challenged secondarily with HKSa (10 microg/mL) exhibited a decrease in the production of TNF-alpha (89 +/- 5%, P<0.05) and TxB2 (85 +/- 3%, P<0.05) compared with HKSa-stimulated naive cells. By contrast, secondary LPS challenge of HKSa-pretreated cells augmented TNF-alpha (41 +/- 3%, P<0.05) and TxB2 (42 +/- 6%, P<0.05) compared with LPS-stimulated naive cells. In naive cells, HKSa and LPS stimulation also significantly phosphorylated the mitogen-activated kinases (MAPKs) p38, JNK, and ERK-1/2 (P<0.005) compared with basal levels. HKSa and LPS induced homologous tolerance as evidenced by the down-regulation of the three MAPK (P<0.05), thus paralleling data on mediator production. HKSa-pretreated cells' priming responses to LPS correlated with augmented phosphorylation of JNK and p38 (P<0.05), whereas ERK-1/2 phosphorylation remained down-regulated. In contrast to TNF-alpha and TxB2 production, HKSa-induced IFN-gamma was up-regulated (26 +/- 5%) in HKSa-pretreated cells compared with HKSa-stimulated naive cells. IFN-gamma antibody exhibited reversed priming in HKSa-pretreated cells as evidenced by a reduction in TNF-alpha. Exogenous human IFN-gamma- (1 microg/mL) and HKSa-pretreated cells secondarily stimulated with HKSa did not prevent the induction of tolerance. In contrast, exogenous IFN-gamma pretreatment prevented the induction of LPS homologous tolerance resulting in an increase in TNF-alpha production. The data demonstrate that HKSa induces homologous tolerance but causes priming to LPS.

Linezolid for treatment of ventilator-associated pneumonia: A cost-effective alternative to vancomycin*

OBJECTIVES

To determine the incremental cost-effectiveness of linezolid compared with vancomycin for treatment of ventilator-associated pneumonia due to Staphylococcus aureus.

DESIGN

Decision model analysis of the cost and efficacy of linezolid vs. vancomycin for treatment of ventilator-associated pneumonia. The primary outcome was the incremental cost-effectiveness of linezolid in terms of cost per added quality-adjusted life-year gained. Other outcomes were the marginal costs per hospital survivor and per year of life saved generated by using linezolid. Model estimates were derived from prospective trials of linezolid for ventilator-associated pneumonia and from other studies describing the costs and outcomes for ventilator-associated pneumonia.

SETTING AND PATIENTS

Hypothetical cohort of 1,000 patients diagnosed with ventilator-associated pneumonia.

INTERVENTIONS

In the model, patients received either linezolid or vancomycin.

MEASUREMENTS AND MAIN RESULTS

The incremental cost-effectiveness of linezolid was calculated as the additional quality-adjusted life-years resulting from therapy with linezolid divided by the sum of the incremental costs arising because of use of linezolid (e.g., higher direct costs for linezolid, costs per in-hospital care of survivors, and posthospitalization costs). Despite its higher cost, linezolid was cost-effective for treatment of ventilator-associated pneumonia. The cost per quality-adjusted life-year equals approximately 30,000 dollars. The model was moderately sensitive to the estimated efficacy of linezolid over vancomycin. Nonetheless, even with all inputs simultaneously skewed against, linezolid remains a cost-effective option (cost per quality-adjusted life-year approximately 100,000 dollars). Based on Monte Carlo simulation, the results of our analysis are robust across a range of model inputs and assumptions (95% confidence interval for cost per quality-adjusted life-year ranges from 23,637 dollars to 42,785 dollars).

CONCLUSIONS

Linezolid is a cost-effective alternative to vancomycin for the treatment of ventilator-associated pneumonia.

Pyrimidinone antibiotics--heterocyclic analogues with improved antibacterial spectrum

We report the synthesis and pharmacological evaluation of new derivatives of the natural dipeptide antibiotic TAN 1057 A,B containing heterocycles either in the beta-amino acid side chain or as mimics of the urea function. In the course of this program, we identified novel analogues that display activity towards a broader panel of Gram-positive bacteriae.

Involvement of G(i) proteins and Src tyrosine kinase in TNFalpha production induced by lipopolysaccharide, group B Streptococci and Staphylococcus aureus

Previous studies have suggested that heterotrimeric G(i) proteins, Src tyrosine kinase and phosphatidylinositol-3 kinase (PI3 Kinase) are involved in signaling events induced by lipopolysaccharide (LPS) leading to pro-inflammatory cytokines gene expression. To investigate the involvement of these mediators in Gram-positive bacteria induced pro-inflammatory cytokine expression, LPS (10 ng/ml), heat killed group B Streptococci (GBS 1 microg/ml) and Staphylococcus aureus (SA 10 microg/ml) were used to induce TNFalpha production in the murine J774A.1 macrophage (MØ) cell line and human promonocytic THP-1 cell line. Pertussis toxin (PTx, 1 microg/ml), an inhibitor of G(i) protein; pyrazolopyrimidine-2 (PP2, 1 or 25 microM), a Src tyrosine kinase inhibitor; and LY294002 (100 nM), an inhibitor of PI3 Kinase were used to examine the involvement of G(i), Src tyrosine kinase and PI3 Kinase, respectively, in TNFalpha production. In J774A.1 cells, pretreatment with PTx and PP2 attenuated TNFalpha production induced by LPS (60+/-9% and 81+/-11% inhibition, n=3, p<0.05, respectively), GBS (95+/-1% and 80+/-6% inhibition, n=3, p<0.05, respectively) and SA (51+/-18% and 68+/-16% inhibition, n=4, p<0.05, respectively). However, pretreatment with LY 294002 inhibited LPS induced TNFalpha production (82+/-13% inhibition, n=3, p<0.05), but did not inhibit GBS or SA induced TNFalpha production. In THP-1 cells, pretreatment with PTx, PP2 and LY 294002 inhibited TNFalpha production induced by LPS (84+/-3%, 59+/-12% and 84+/-4% inhibition, n=3, p<0.05, respectively) and SA (56+/-7%, 87+/-1% and 35+/-6% inhibition, n=3, p<0.05, respectively). These data support our hypothesis that G(i)-coupled and Src tyrosine kinase-coupled signaling pathways are involved in both Gram-negative and Gram-positive bacteria induced pro-inflammatory cytokine expression. However, unlike LPS, involvement of PI3 Kinase in Gram-positive bacteria induced signaling pathways are species dependent.

Baseline study to determine in vitro activities of daptomycin against gram-positive pathogens isolated in the United States in 2000-2001

The activity of daptomycin was assessed by using 6,973 gram-positive bacteria isolated at 50 United States hospitals in 2000 and 2001. Among the isolates of Streptococcus pneumoniae (n = 1,163) collected, the rate of penicillin resistance was 16.1%; rates of oxacillin resistance among Staphylococcus aureus isolates (n = 1,018) and vancomycin resistance among Enterococcus faecium isolates (n = 368) were 30.0 and 59.5%, respectively. Multidrug-resistant (MDR) phenotypes (isolates resistant to three or more different chemical classes of antimicrobial agents) accounted for 14.2% of S. pneumoniae isolates, 27.1% of S. aureus isolates, and 58.4% of E. faecium isolates. For all gram-positive species tested, MICs at which 90% of the isolates tested were inhibited (MIC(90)s) and MIC ranges for directed-spectrum agents (daptomycin, quinupristin-dalfopristin, and linezolid) were identical or highly similar for isolates susceptible or resistant to other agents or MDR. Daptomycin had a MIC(90) of 0.12 micro g/ml for both penicillin-susceptible and -resistant isolates of S. pneumoniae. Against oxacillin-resistant S. aureus daptomycin had a MIC(90) of 0.5 micro g/ml, and it had a MIC(90) of 4 micro g/ml against both vancomycin-susceptible and -resistant E. faecium. The MIC(90)s for daptomycin and other directed-spectrum agents were unaffected by the regional or anatomical origin of isolates or patient demographic parameters (patient age, gender, and inpatient or outpatient care). Our results confirm the gram-positive spectrum of activity of daptomycin and that its activity is independent of susceptibility or resistance to commonly prescribed and tested antimicrobial agents. This study may serve as a baseline to monitor future changes in the susceptibility of gram-positive species to daptomycin following its introduction into clinical use.

Selective decontamination of the digestive tract

Ventilator-associated pneumonia usually originates from the patient's oropharyngeal microflora. In selective digestive decontamination, topical antibiotics are applied to the oropharynx and stomach for prevention of pneumonia and other infections, possibly reducing infection-related mortality. Selective digestive decontamination is also used for the prevention of gut-derived infections in acute necrotizing pancreatitis and liver transplantation. Despite numerous clinical trials, selective digestive decontamination remains controversial. Reduction of the incidence of pneumonia is accepted, but the extent of reduction is debated. Mortality was not reduced in most individual trials, but this finding was calculated in meta-analyses, especially for combined use of topical and systemic antibiotics in surgical ICU patients. Some investigators reported increased resistance and a shift to Gram-positive pathogens. Today, it appears that selective means not only selective suppression of pathogenic bacteria but also selection of appropriate groups of patients for underlying diseases and severity of illness, and selection of ICUs, where the endemic resistance patterns might allow the use of selective digestive decontamination at a relatively low risk for increased selection pressure.

Treatment of post-burns bacterial infections by bacteriophages, specifically ubiquitous Pseudomonas spp. notoriously resistant to antibiotics

Post-burn microbial infections are a major problem in recovering from the trauma of third-degree burns, and the survival of patients can depend upon the severity of the burn and the infections encountered. Within 24 hours, patients can start suffering from opportunistic bacterial attacks, which can vary from simple infection, such as those easily treatable by antibiotics, to more complicated types, which may have natural or acquired resistance to drugs. Infection by multiple drug-resistant bacteria can create additional complexity to the problem. As an alternative to treating bacterial infections by antibiotics, bacteriophages have been in use in certain parts of the world, such as at Tbilisi in Georgia and in Poland, and this approach has now been more widely recognized. Results have shown that phage therapy has an 80% success rate against Enterococcus infections and up to 90% against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae. Here it is proposed that bacteriophages can effectively be used for the treatment of post-burn infections, particularly the ubiquitous opportunistic pathogens, Pseudomonas spp., known to be notoriously resistant to a variety of antibiotics. This kind of treatment may be of particular importance in Third World countries where the incidence of burns and infections, due to lack of stringent safety regulations and proper hygiene respectively, may be more common and where cocktails of antibiotics may be less affordable. Phages that can possibly be employed in the treatment and their advantages compared to the use of antibiotics are also highlighted.

Treatment of gram-positive infections: past, present, and future

The need for strategic planning for antimicrobial use has reached a critical point. The rise in resistant nosocomial and community gram-positive bacteria mandates appropriate antibiotic selection and dosing. The development of new compounds is not the answer, because many are based off existing structures to which bacteria have already developed resistance. New antimicrobial agents are falling to the resistant mechanisms developed by the bacteria, after only limited clinical exposure. Judicious use of antimicrobial agents and applying pharmacokinetic principles when dosing can help slow the rate of resistance.

Toll-like receptors

The ability of a host to sense invasion by pathogenic organisms and to respond appropriately to control infection is paramount to survival. In the case of sepsis and septic shock, however, an exaggerated systemic response may, in fact, contribute to the morbidity and mortality associated with overwhelming infections. The innate immune system has evolved as the first line of defense against invading microorganisms. The Toll-like receptors (TLRs) are a part of this innate immune defense, recognizing conserved patterns on microorganisms. These TLRs and their signaling pathways are represented in such diverse creatures as mammals, fruit flies, and plants. Ten members of the TLR family have been identified in humans, and several of them appear to recognize specific microbial products, including lipopolysaccharide, bacterial lipoproteins, peptidoglycan, and bacterial DNA. Signals initiated by the interaction of TLRs with specific microbial patterns direct the subsequent inflammatory response. Thus, TLR signaling represents a key component of the innate immune response to microbial infection.