The effect of pulmonary surfactant on the in vitro activity of Iclaprim against common respiratory bacterial pathogens

The in vitro antimicrobial activity of iclaprim, a novel diaminopyrimidine, against common respiratory bacteria remained unchanged in the presence of pulmonary surfactant (Survanta®) at concentrations that greatly antagonized the antimicrobial activity of daptomycin. These results indicate that iclaprim could be a potential treatment for pneumonia caused by susceptible and multidrug resistant bacteria.

A Phase II Randomized, Double-blind, Multicenter Study to Evaluate Efficacy and Safety of Intravenous Iclaprim Versus Vancomycin for the Treatment of Nosocomial Pneumonia Suspected or Confirmed to be Due to Gram-positive Pathogens

PURPOSE

The primary objective of this Phase II study was to compare the clinical cure rates of 2 iclaprim dosages versus vancomycin in the treatment of patients with nosocomial pneumonia suspected or confirmed to be caused by gram-positive pathogens.

METHODS

This study was a double-blind, randomized, multicenter trial. A total of 70 patients were randomized 1:1:1 to receive iclaprim 0.8 mg/kg IV q12h (iclaprim q12h; n = 23), iclaprim 1.2 mg/kg IV q8h (iclaprim q8h; n = 24), or vancomycin 1 g IV q12h (vancomycin; n = 23) for 7 to 14 days. The primary end point was clinical cure in the intention-to-treat population at test of cure (TOC; 7 [1] days' posttreatment) visit.

FINDINGS

The baseline and demographic characteristics of patients treated with either iclaprim or vancomycin were comparable. Cure rates in the intention-to-treat population were 73.9% (17 of 23), 62.5% (15 of 24), and 52.2% (12 of 23) at the TOC visit in the iclaprim q12h, iclaprim q8h, and vancomycin groups, respectively (iclaprim q12h vs vancomycin, P = 0.13; iclaprim q8h vs vancomycin, P = 0.47). The death rates within 28 days of the start of treatment were 8.7% (2 of 23), 12.5% (3 of 24), and 21.7% (5 of 23) for the iclaprim q12h, iclaprim q8h, and vancomycin groups (no statistically significant differences). The adverse event profile of both iclaprim dosing regimens was similar to that of vancomycin.

IMPLICATIONS

Iclaprim had clinical cure rates and a safety profile comparable with vancomycin among patients with nosocomial pneumonia. Iclaprim could be an important new therapeutic option for the treatment of nosocomial pneumonia, and a pivotal clinical trial is warranted to evaluate its safety and efficacy in this indication.

Response of HIV-Infected Patients with Asymptomatic Syphilis to Intensive Intramuscular Therapy with Ceftriaxone or Procaine Penicillin

The objective of this prospective pilot study was to evaluate the response of HIV-infected patients with asymptomatic syphilis to one of two intensive antibiotic treatment regimens. Thirty-one HIV-infected patients with serum rapid plasma reagin titre ≥1:4 and no clinical findings of syphilis were randomized to receive daily intramuscular injections of ceftriaxone or procaine penicillin (plus oral probenecid) for 15 days; 24 returned for follow-up study. Seven of 10 (70%) procaine penicillin-treated patients and 10 of 14 (71%) ceftriaxone-treated patients had a ≥4-fold decline in RPR ( P=0.94); two penicillin-treated and one ceftriaxone-treated patient relapsed. Two patients failed ceftriaxone therapy. Three penicillin-treated, and two ceftriaxone-treated patients were serofast. Serological responses were similar in those patients with and without asymptomatic neurosyphilis. There was no difference in the serologic response to daily treatment with ceftriaxone vs that with procaine penicillin plus probenecid; both treatments were associated with comparatively high rates of serological non-response and relapse.

Value of C-arm computed tomography in radiofrequency ablation of small lung lesions

This study aimed to explore the value of C-arm computed tomography (CT) applications in radiofrequency ablation (RFA) of small lung lesions. The puncture success rate, cumulative survival rate, tumor response rate, complications, and radiation dose during C-arm CT-guided RFA of 36 small lung lesions in 34 patients were analyzed. In 35 RFA procedures for 36 small lung lesions, the puncture success rate was 100%. There were 7 cases of complications, including 4 cases of pneumothorax (puncture suction or closed chest drainage was not required) and 3 cases of hemoptysis. The cumulative survival rate in the 34 patients after RFA was 100% at 6 months, 69.0% at 1 year, and 60.0% at 2 years. In assessments of 36 foci imaged during the follow-up period, the total response rates at 1 month, 3 months, and 6 months were 77.8% (28/36), 69.7% (23/33), and 61.3% (19/31), respectively. The mean cumulative dose and average effective dose during surgery were 120.1 ± 61.4 mGy and 3.5 ± 1.7 mSv, respectively. The application of C-arm CT to RFA of small lung lesions could provide abundant information to the surgeon and increase the lesion puncture success rate and is considered to be a promising image-guided technology.

Linezolid effects on bacterial toxin production and host immune response: review of the evidence

BACKGROUND

Linezolid is active against a broad range of gram-positive pathogens and has the potential to also affect production of bacterial toxins and host immune function.

OBJECTIVE

To assess the evidence for direct effects of linezolid on bacterial toxin synthesis and modulation of host immune responses.

METHODS

Literature searches were performed of the PubMed and OVID databases. Reviews and non-English language articles were excluded. Articles with information on the effect of linezolid on bacterial toxin synthesis and immune responses were selected for further review, and data were summarized.

RESULTS

Substantial in vitro evidence supports effects of linezolid on bacterial toxin production; however, the strength of the evidence and the nature of the effects are mixed. In the case of Staphylococcus aureus, repeated observations support the inhibition of production of certain staphylococcal toxins (Panton-Valentine leukocidin, protein A, and α- and β-hemolysin) by linezolid, whereas only solitary reports indicate inhibition (toxic shock syndrome toxin-1, coagulase, autolysins, and enterotoxins A and B) or stimulation (phenol-soluble modulins) of toxin production by linezolid. In the case of Streptococcus pyogenes, there are solitary reports of linezolid inhibition (protein M, deoxyribonuclease, and streptococcal pyrogenic exotoxins A, B, and F) or stimulation (immunogenic secreted protein 2 and streptococcal inhibitor of complement-mediated lysis) of toxin production, whereas published evidence for effects on streptolysin O production is conflicting. In vitro data are limited, but suggest that linezolid might also have indirect effects on host cytokine expression through inhibition of bacterial production of toxins. In vivo data from preclinical animal studies and a single clinical study in humans are limited and equivocal insofar as a potential role for linezolid in modulating the host inflammatory response; this is due in part to the difficulty in isolating antimicrobial effects and toxin synthesis inhibitory effects of linezolid from any secondary effects on host inflammatory response.

CONCLUSIONS

Available evidence supports the possibility that linezolid can inhibit, and in some cases stimulate, toxin production in clinically relevant pathogens. However, more research will be needed to determine the potential clinical relevance of those findings for linezolid.

Plasmid transferability of KPC into a virulent K2 serotype Klebsiella pneumoniae

BACKGROUND

KPC-producing carbapenem-resistant Klebsiella pneumoniae (CRKP) infections are associated with high mortality; however, their virulence determinants are not well defined.

METHODS

We investigated the virulence and plasmid transferability among KPC-containing K. pneumoniae isolates.

RESULTS

KPC-2 and -3 were successfully conjugated and retained by a virulent K2 K. pneumoniae recipient isolate. Antimicrobial susceptibility testing showed KPC-2 and -3 donor strains were resistant to more than four classes of antibiotics while the K2 isolate was only initially resistant to ampicillin. After conjugation of KPC-2 and -3, the K2 K. pneumoniae transconjugants became resistant to all beta-lactams. Additionally, the KPC K2 K. pneumoniae transconjugants continued to retain its high serum resistance and murine lethality.

CONCLUSIONS

Conjugation and retainment of KPC by virulent K2 K. pneumoniae and the ability of the tranconjugants to maintain its high serum resistance and murine lethality after conjugation was demonstrated in this study. These findings are concerning for the potential of KPC-like genes to disseminate among virulent K. pneumoniae isolates.

Combination therapy with lysin CF-301 and antibiotic is superior to antibiotic alone for treating methicillin-resistant Staphylococcus aureus-induced murine bacteremia

Lysins are bacteriophage-derived enzymes that degrade bacterial peptidoglycans. Lysin CF-301 is being developed to treat Staphylococcus aureus because of its potent, specific, and rapid bacteriolytic effects. It also demonstrates activity on drug-resistant strains, has a low resistance profile, eradicates biofilms, and acts synergistically with antibiotics. CF-301 was bacteriolytic against 250 S. aureus strains tested including 120 methicillin-resistant S. aureus (MRSA) isolates. In time-kill studies with 62 strains, CF-301 reduced S. aureus by 3-log₁₀ within 30 minutes compared to 6–12 hours required by antibiotics. In bacteremia, CF-301 increased survival by reducing blood MRSA 100-fold within 1 hour. Combinations of CF-301 with vancomycin or daptomycin synergized in vitro and increased survival significantly in staphylococcal-induced bacteremia compared to treatment with antibiotics alone (P < .0001). Superiority of CF-301 combinations with antibiotics was confirmed in 26 independent bacteremia studies. Combinations including CF-301 and antibiotics represent an attractive alternative to antibiotic monotherapies currently used to treat S. aureus bacteremia.

Lysins: the arrival of pathogen-directed anti-infectives

Lysins represent a novel class of anti-infectives derived from bacteriophage. Lysins are bacterial cell-wall hydrolytic enzymes that selectively and rapidly kill (≥3 log c.f.u. in 30 min) specific Gram-positive bacteria providing a targeted therapeutic approach with minimal impact on unrelated commensal flora. The potential for bacterial resistance to lysins is considered low due to targeting of highly conserved peptidoglycan components. Through cutting-edge genetic engineering, lysins can be assembled into large libraries of anti-infective agents tailored to any bacterium of interest including drug-resistant Gram-positive pathogens such as meticillin- and vancomycin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis and Enterococcus faecium, and penicillin-resistant Streptococcus pneumoniae. Lysins can eliminate bacteria systemically and topically from mucosal surfaces and biofilms, as evidenced by experimental models of sepsis, endocarditis, pneumonia, meningitis, and nasopharyngeal, skin and vaginal decolonization. Furthermore, lysins can act synergistically with antibiotics and, in the process, resensitize bacteria to non-susceptible antibiotics. Clinical trials are being prepared to assess the safety and pharmacokinetic properties of lysins in humans.

A risk score for identifying methicillin-resistant Staphylococcus aureus in patients presenting to the hospital with pneumonia

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) represents an important pathogen in healthcare-associated pneumonia (HCAP). The concept of HCAP, though, may not perform well as a screening test for MRSA and can lead to overuse of antibiotics. We developed a risk score to identify patients presenting to the hospital with pneumonia unlikely to have MRSA.

METHODS

We identified patients admitted with pneumonia (Apr 2005-Mar 2009) at 62 hospitals in the US. We only included patients with lab evidence of bacterial infection (e.g., positive respiratory secretions, blood, or pleural cultures or urinary antigen testing). We determined variables independently associated with the presence of MRSA based on logistic regression (two-thirds of cohort) and developed a risk prediction model based on these factors. We validated the model in the remaining population.

RESULTS

The cohort included 5975 patients and MRSA was identified in 14%. The final risk score consisted of eight variables and a potential total score of 10. Points were assigned as follows: two for recent hospitalization or ICU admission; one each for age < 30 or > 79 years, prior IV antibiotic exposure, dementia, cerebrovascular disease, female with diabetes, or recent exposure to a nursing home/long term acute care facility/skilled nursing facility. This study shows how the prevalence of MRSA rose with increasing score after stratifying the scores into Low (0 to 1 points), Medium (2 to 5 points) and High (6 or more points) risk. When the score was 0 or 1, the prevalence of MRSA was < 10% while the prevalence of MRSA climbed to > 30% when the score was 6 or greater.

CONCLUSIONS

MRSA represents a cause of pneumonia presenting to the hospital. This simple risk score identifies patients at low risk for MRSA and in whom anti-MRSA therapy might be withheld.

Rifaximin therapy of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder characterized by abdominal pain and altered bowel habits in the absence of specific organic pathology. Although the underlying pathogenesis of IBS is not well-understood, small intestinal bacterial overgrowth (SIBO) or other abnormalities in the gut flora is believed to contribute to the development of a subset of IBS cases. Rifaximin is a poorly absorbed antimicrobial with activity against enteric pathogens. A number of studies have shown a significant improvement in IBS symptoms with antibiotic therapy including rifaximin. In this review, we discuss the pharmacokinetics, in vitro susceptibility profile, and efficacy and safety data from clinical trials of rifaximin treatment of IBS.

Incidence of Intravenous Catheter-Site Complications in Patients Treated with Linezolid or Vancomycin for Skin Infections Caused by Methicillin-Resistant Staphylococcus aureus

Objective

The aim of the study was to compare all-cause adverse events (AEs) and those caused by intravenous (IV) catheter-site complications (IVCSCs) using data from a previously published study of the use of linezolid or vancomycin for treatment of complicated skin and skin structure infections (cSSSI) suspected or proven to be caused by methicillin-resistant Staphylococcus aureus.

Methods

To examine the incidence of AEs caused by the 2 antibiotic treatments, we conducted a post hoc analysis of data from a prospective, open-label, randomized, multicenter phase 4 study. Patients were randomized to treatment with either oral (PO) or IV linezolid 600 mg every 12 hours or with IV vancomycin 15 mg/kg every 12 hours with dose adjustment as needed. Study treatment was administered for 7 to 14 days. We excluded patients with baseline bacteremia (n = 11) and those who started on PO linezolid (n = 215). We analyzed data only from patients who received at least 1 dose of IV study medication.

Results

Patient demographics and types of cSSSI were comparable among patients receiving linezolid (n = 315) and vancomycin (n = 511). Mean durations of IV therapy for patients receiving linezolid and vancomycin were 4.5 days and 7.6 days (1,418 and 3,884 patient-days, respectively). All-cause AEs were reported in 50% and 51% of patients in the linezolid and vancomycin groups, respectively; all-cause IVCSCs were reported in 2% and 7%, respectively. Treatment-related IVCSCs were reported in 1 patient in the linezolid group and 16 patients in the vancomycin group.

Conclusions

The overall rate of AEs was similar among patients receiving linezolid and vancomycin, but AEs caused by IVCSCs were more frequent among patients receiving vancomycin and rare episodes of bacteremia and sepsis were more common in the linezolid group.

Phenotypic and genotypic screening and clonal analysis of carbapenem-resistant Klebsiella pneumoniae at a single hospital

Detection of bla(KPC)-harboring Klebsiella pneumoniae (KP) in the clinical laboratory remains a difficult task. Decreased ertapenem (ERT) susceptibility has been considered one of the most sensitive phenotypic indicators of K. pneumoniae carbapenemase (KPC) production, but has been found to be nonspecific. Susceptibility testing using imipenem or meropenem lacks the sensitivity for detection of KPCs, and there is limited experience using doripenem (DOR). Fifty-five individual ERT-nonsusceptible KP isolates and 19 isolates that were ERT-susceptible, extended spectrum β-lactamase-positive KP were collected from the clinical laboratory and tested for DOR susceptibility by Etest methodology. PCR screening for bla(KPC) was performed on all specimens. All but three isolates with ERT resistance were KPC positive by PCR. Compared to PCR, ERT detection of KPC had a sensitivity of 98% and a false-positive rate of 6%. Overall, there was a 97% agreement between ERT and DOR susceptibility results. However, there was one KPC-positive isolate that was discrepant (ERT susceptible, DOR nonsusceptible by Etest). Selected isolates of KP from both groups underwent pulsed-field gel electrophoresis analysis to determine the degree of genetic relatedness of KPC-positive and KPC-negative isolates. Pulsed-field gel electrophoresis of selected KPC-positive and KPC-negative KP identified a common pattern between both groups. The resistance to DOR and/or ERT is sensitive and a specific indicator for detection of bla(KPC) in KP.

Combined retrospective analysis of seven phase II and III trials of the efficacy of linezolid in the treatment of pneumonia caused by multidrug-resistant Streptococcus pneumoniae

BACKGROUND

Antimicrobial resistance among Streptococcus pneumoniae is of concern. Up to 30% of pneumococcal isolates worldwide are multidrug resistant.

OBJECTIVE

The objective of this analysis was to assess the effectiveness of linezolid for the treatment of pneumonia caused by S pneumoniae, including multidrug-resistant S pneumoniae (MDRSP).

METHODS

Data from 7 Phase II and III clinical trials that assessed the efficacy of linezolid in community- or hospital-acquired pneumonia were pooled. Adults and children (aged ≤12 years) received linezolid 600 mg and 10 mg/kg, respectively, IV or PO q12h for 7 to 14 days, with the exception of patients with documented bacteremia who could be treated for up to 28 days. Patients with a confirmed baseline isolate of S pneumoniae, including MDRSP, were assessed for clinical and microbiological outcomes. MDRSP was defined as an isolated strain of S pneumoniae that was resistant to ≥3 classes of antibiotics. Clinical cure was defined as the resolution of clinical signs and symptoms of pneumonia compared with baseline, with either improvement or absence of progression of abnormalities on chest radiography. Microbiological eradication was defined as documented or presumed eradication at the test-of-cure (TOC) visit. Results from patients with indeterminate or missing outcomes at TOC were not included in the analyses.

RESULTS

Of the patients with no bacteremia and treated with linezolid, 19 adults had MDRSP and 165 had non-MDRSP, and 3 children had MDRSP and 7 had non-MDRSP. Clinical cure and microbiological eradication rates were not significantly different between those infected with an MDRSP or non-MDRSP pathogen, respectively, in adults (16/19 [84%] and 150/164 [91%]) and children (3/3 [100%] and 7/7 [100%]).

CONCLUSION

Linezolid was efficacious for the treatment of pneumonia caused by S pneumoniae, including multidrug-resistant strains.

Evaluation of steady-state pharmacokinetic interactions between ritonavir-boosted BILR 355, a non-nucleoside reverse transcriptase inhibitor, and lamivudine/zidovudine in healthy subjects

WHAT IS KNOWN AND OBJECTIVE

BILR 355 is a second generation non-nucleoside reverse transcriptase inhibitor. It has shown promising in vitro anti-HIV-1 activities and favourable human pharmacokinetic properties after co-administration with ritonavir (RTV). Lamivudine (3TC) is a nucleoside reverse transcriptase inhibitor. It is excreted predominantly in urine by a transporter-mediated pathway. These two drugs are likely to be given together to HIV-infected patients. The objective of this study was to investigate any steady-state pharmacokinetic interactions between RTV-boosted BILR 355 and 3TC/zidovudine (ZDV).

METHODS

This was a randomized, open label, prospective study. In group A, 39 healthy subjects were given 3TC/ZDV (150 mg/300 mg) twice daily (b.i.d.) for 7 days, and then BILR 355 and RTV (BILR 355/r, 150 mg/100 mg) were co-administered with this regimen for an additional 7 days. Intensive blood samples were taken on days 7 and 14 for pharmacokinetic assessments. In group B, 12 healthy subjects were given BILR 355/r (150 mg/100 mg) b.i.d. for 7 days. The pharmacokinetic data from group B were pooled with data from group B subjects in other similar studies performed in parallel (BILR 355 alone group in BILR 355 drug-drug interaction studies with tipranavir, lopinavir/RTV, and emtricitabine/tenofovir DF; BILR 355 regimen was the same).

RESULTS AND DISCUSSION

After co-administration with BILR 355/r, the AUC(12,ss) and C(max,ss) of 3TC increased by 45% and 24%, respectively; the elimination half-life (t(1/2) ,ss) of 3TC was significantly increased. However, the pharmacokinetics of ZDV was unchanged. Co-administration with 3TC/ZDV resulted in a 22% decrease in AUC(12,ss) and a 20% decrease in C(max,ss) for BILR 355. The observed increase in exposure and prolongation of t(1/2,ss) of 3TC is potentially related to inhibition of OCT-mediated urinary excretion of 3TC.

WHAT IS NEW AND CONCLUSION

Concomitant administration of BILR 355 with 3TC/ZDV resulted in a modest decrease in exposure to BILR 355 and a 45% increase in exposure to 3TC.

The role of rifaximin in the treatment and chemoprophylaxis of travelers' diarrhea

Travelers’ diarrhea is a common illness among international travelers from developed to developing countries. Travelers’ diarrhea is caused by ingestion of contaminated food and water. Bacteria are the primary cause of travelers’ diarrhea. In most surveys, the most common diarrheal pathogen identified is enterotoxigenic Escherichia coli. There are several antimicrobial agents available for the treatment of travelers’ diarrhea including rifaximin which is approved in the United States for the treatment of travelers’ diarrhea due to noninvasive E. coli strains. In this review, we will review the most recent advances of rifaximin for the treatment and prevention of travelers’ diarrhea, with regard to its pharmacokinetics, in vitro susceptibility profile, and efficacy and safety data from clinical trials.