Therapeutics for Vancomycin-Resistant Enterococcal Bloodstream Infections.

Vancomycin-resistant enterococci (VRE) are common causes of bloodstream infections (BSIs) with high morbidity and mortality rates. They are pathogens of global concern with a limited treatment pipeline. Significant challenges exist in the management of VRE BSI, including drug dosing, the emergence of resistance, and the optimal treatment for persistent bacteremia and infective endocarditis. Therapeutic drug monitoring (TDM) for antimicrobial therapy is evolving for VRE-active agents; however, there are significant gaps in the literature for predicting antimicrobial efficacy for VRE BSIs. To date, TDM has the greatest evidence for predicting drug toxicity for the three main VRE-active antimicrobial agents daptomycin, linezolid, and teicoplanin. This article presents an overview of the treatment options for VRE BSIs, the role of antimicrobial dose optimization through TDM in supporting clinical infection management, and challenges and perspectives for the future.

Nocardia species distribution and antimicrobial susceptibility within Australia.

BACKGROUND: Nocardia is a ubiquitous saprophyte capable of causing human disease. Disease is primarily respiratory or cutaneous, usually acquired via inhalation or inoculation. Under the influence of environmental and host factors, Nocardia incidence and species distribution demonstrate geographical variation. AIMS: To examine for differences in Nocardia incidence within Western Australia (WA) and analyse species distribution in the context of prior published studies. To analyse antibiogram data from a nationwide passive antimicrobial resistance surveillance program. METHODS: Retrospective extraction of laboratory data for Western Australian Nocardia isolates over a 21-year period. Analysis of Nocardia antimicrobial susceptibility testing data submitted to the Australian Passive Antimicrobial Resistance Surveillance (APAS) program between 2005 and 2022. RESULTS: Nine hundred sixty WA isolates were identified, giving an annual incidence of 3.03 per 100 000 population with apparent latitudinal variation. The four most common species identified within WA and amongst APAS isolates were N. nova, N. cyriacigeorgica, N. brasiliensis and N. farcinica. APAS data demonstrated that all species exhibited high rates of susceptibility to linezolid (100%) and trimethoprim-sulfamethoxazole (98%). Amikacin (>90% susceptibility for all species except N. transvalensis) was the next most active parenteral agent, superior to both carbapenems and third-generation cephalosporins. Susceptibility to oral antimicrobials (other than linezolid) demonstrated significant interspecies variation. CONCLUSIONS: We demonstrate geographical variation in the distribution of Nocardia incidence. Four species predominate in the Australian setting, and nationwide data confirm a high in vitro susceptibility to trimethoprim-sulphamethoxazole and linezolid, justifying their ongoing role as part of first-line empiric therapy.

Oral ciprofloxacin activity against ceftriaxone-resistant Escherichia coli in an in vitro bladder infection model.

OBJECTIVES: Pharmacodynamic profiling of oral ciprofloxacin dosing for urinary tract infections caused by ceftriaxone-resistant Escherichia coli isolates with ciprofloxacin MIC ≥ 0.25 mg/L. BACKGROUND: Urine-specific breakpoints for ciprofloxacin do not exist. However, high urinary concentrations may promote efficacy in isolates with low-level resistance. METHODS: Ceftriaxone-resistant E. coli urinary isolates were screened for ciprofloxacin susceptibility. Fifteen representative strains were selected and tested using a dynamic bladder infection model. Oral ciprofloxacin dosing was simulated over 3 days (250 mg daily, 500 mg daily, 250 mg 12 hourly, 500 mg 12 hourly and 750 mg 12 hourly). The model was run for 96 h. Primary endpoint was change in bacterial density at 72 h. Secondary endpoints were follow-up change in bacterial density at 96 h and area-under-bacterial-kill-curve. Bacterial response was related to exposure (AUC0-24/MIC; Cmax/MIC). PTA was determined using Monte-Carlo simulation. RESULTS: Ninety-three clinical isolates demonstrated a trimodal ciprofloxacin MIC distribution (modal MICs at 0.016, 0.25 and 32 mg/L). Fifteen selected clinical isolates (ciprofloxacin MIC 0.25-512 mg/L) had a broad range of quinolone-resistance genes. Following ciprofloxacin exposure, E. coli ATCC 25922 (MIC 0.008 mg/L) was killed in all dosing experiments. Six isolates (MIC ≥ 16 mg/L) regrew in all experiments. Remaining isolates (MIC 0.25-8 mg/L) regrew variably after an initial period of killing, depending on simulated ciprofloxacin dose. A >95% PTA, using AUC0-24/MIC targets, supported 250 mg 12 hourly for susceptible isolates (MIC ≤ 0.25 mg/L). For isolates with MIC ≤ 1 mg/L, 750 mg 12 hourly promoted 3 log10 kill at the end of treatment (72 h), 1 log10 kill at follow-up (96 h) and 90% maximal activity (AUBKC0-96). CONCLUSIONS: Bladder infection modelling supports oral ciprofloxacin activity against E. coli with low-level resistance (ciprofloxacin MIC ≤ 1 mg/L) when using high dose therapy (750 mg 12 hourly).

Oral fosfomycin activity against Klebsiella pneumoniae in a dynamic bladder infection in vitro model.

INTRODUCTION: The use of oral fosfomycin for urinary tract infections (UTIs) caused by non-Escherichia coli uropathogens is uncertain, including Klebsiella pneumoniae, the second most common uropathogen. METHODS: A multicompartment bladder infection in vitro model was used with standard media and synthetic human urine (SHU) to simulate urinary fosfomycin exposure after a single 3 g oral dose (fAUC0-72 16884 mg·h/L, t½ 5.5 h) against 15 K. pneumoniae isolates including ATCC 13883 (MIC 2 to >1024 mg/L) with a constant media inflow (20 mL/h) and 4-hourly voiding of each bladder. The impact of the media (CAMHB + G6P versus SHU) on fosfomycin MIC measurements, drug-free growth kinetics and regrowth after fosfomycin administration was assessed. A low and high starting inoculum (5.5 versus 7.5 log10 cfu/mL) was assessed in the bladder infection model. RESULTS: Compared with CAMHB, isolates in SHU had a slower growth rate doubling time (37.7 versus 24.1 min) and reduced growth capacity (9.0 ± 0.3 versus 9.4 ± 0.3 log10 cfu/mL), which was further restricted with increased inflow rate (40 mL/h) and more frequent voids (2-hourly). Regrowth was commonly observed in both media with emergence of fosfomycin resistance promoted by a high starting inoculum in CAMHB (MIC rise to ≥1024 mg/L in 13/14 isolates). Resistance was rarely detected in SHU, even with a high starting inoculum (MIC rise to ≥1024 mg/L in 2/14 isolates). CONCLUSIONS: Simulated in an in vitro UTI model, the regrowth of K. pneumoniae urinary isolates was inadequately suppressed following oral fosfomycin therapy. Efficacy was further reduced by a high starting inoculum.

Pharmacokinetic/pharmacodynamic analysis of oral fosfomycin against Enterobacterales, Pseudomonas aeruginosa and Enterococcus spp. in an in vitro bladder infection model: impact on clinical breakpoints.

OBJECTIVES: Fosfomycin is an established treatment for uncomplicated urinary tract infections (UTIs), yet evidence supporting susceptibility breakpoints is limited. We examine the UTI susceptibility criteria. METHODS: Fosfomycin susceptibility, heteroresistance and in vitro growth in a bladder infection model, after a single 3 g dose of oral fosfomycin, were bridged to human pharmacokinetics with pharmacokinetic/pharmacodynamic and Monte Carlo analyses. Data from common uropathogens (24 Escherichia coli, 20 Klebsiella pneumoniae, 4 Enterobacter cloacae, 14 Pseudomonas aeruginosa, 8 Enterococcus faecalis and 8 Enterococcus faecium) were compared and analysed to ascertain species-specific PTA. RESULTS: Glucose-6-phosphate (G6P) increased MICs of E. coli, K. pneumoniae and E. cloacae (median 2-fold dilutions 3-5), but not of P. aeruginosa and Enterococcus. Atypical E. coli lacking G6P potentiation were killed in the bladder infection model despite high MICs (32-128 mg/L). Fosfomycin heteroresistance was uncommon in E. coli (MIC > 2 mg/L) but was detected in the majority of K. pneumoniae (MIC > 1 mg/L) and P. aeruginosa (MIC >8 mg/L). For these species, baseline heteroresistance was a strong predictor for treatment failure in the model. No heteroresistance was found in Enterococcus. The fAUC/MIC targets for stasis were 1935, 3393, 9968, 2738 and 283 for typical E. coli, K. pneumoniae, E. cloacae, P. aeruginosa and E. faecalis, respectively (synthetic human urine medium alone promoted a 1 log10 kill in E. faecium). A >95% PTA for stasis was only found at MIC ≤ epidemiological cut-off (ECOFF) for E. coli (4 mg/L). For other species, PTAs were low for WT populations. CONCLUSIONS: With the exception of E. coli, fosfomycin is a poor target for other uropathogen species. A reduction in oral fosfomycin UTI breakpoints is supported.

Genomic surveillance of antimicrobial resistant bacterial colonisation and infection in intensive care patients.

BACKGROUND: Third-generation cephalosporin-resistant Gram-negatives (3GCR-GN) and vancomycin-resistant enterococci (VRE) are common causes of multi-drug resistant healthcare-associated infections, for which gut colonisation is considered a prerequisite. However, there remains a key knowledge gap about colonisation and infection dynamics in high-risk settings such as the intensive care unit (ICU), thus hampering infection prevention efforts. METHODS: We performed a three-month prospective genomic survey of infecting and gut-colonising 3GCR-GN and VRE among patients admitted to an Australian ICU. Bacteria were isolated from rectal swabs (n = 287 and n = 103 patients ≤2 and > 2 days from admission, respectively) and diagnostic clinical specimens between Dec 2013 and March 2014. Isolates were subjected to Illumina whole-genome sequencing (n = 127 3GCR-GN, n = 41 VRE). Multi-locus sequence types (STs) and antimicrobial resistance determinants were identified from de novo assemblies. Twenty-three isolates were selected for sequencing on the Oxford Nanopore MinION device to generate completed reference genomes (one for each ST isolated from ≥2 patients). Single nucleotide variants (SNVs) were identified by read mapping and variant calling against these references. RESULTS: Among 287 patients screened on admission, 17.4 and 8.4% were colonised by 3GCR-GN and VRE, respectively. Escherichia coli was the most common species (n = 36 episodes, 58.1%) and the most common cause of 3GCR-GN infection. Only two VRE infections were identified. The rate of infection among patients colonised with E. coli was low, but higher than those who were not colonised on admission (n = 2/33, 6% vs n = 4/254, 2%, respectively, p = 0.3). While few patients were colonised with 3GCR- Klebsiella pneumoniae or Pseudomonas aeruginosa on admission (n = 4), all such patients developed infections with the colonising strain. Genomic analyses revealed 10 putative nosocomial transmission clusters (≤20 SNVs for 3GCR-GN, ≤3 SNVs for VRE): four VRE, six 3GCR-GN, with epidemiologically linked clusters accounting for 21 and 6% of episodes, respectively (OR 4.3, p = 0.02). CONCLUSIONS: 3GCR-E. coli and VRE were the most common gut colonisers. E. coli was the most common cause of 3GCR-GN infection, but other 3GCR-GN species showed greater risk for infection in colonised patients. Larger studies are warranted to elucidate the relative risks of different colonisers and guide the use of screening in ICU infection control.

Treatment of invasive IMP-4 Enterobacter cloacae infection in transplant recipients using ceftazidime/avibactam with aztreonam: A case series and literature review.

Infections caused by carbapenemase-producing Enterobacteriaceae (CPE) are an emerging threat in both solid organ and stem cell transplant recipients. Invasive CPE infections in transplant recipients are associated with a high mortality, often due to limited therapeutic options and antibacterial toxicities. One of the most therapeutically challenging group of CPE are the metallo-ß-lactamase (MBL)-producing Gram-negative bacteria, which are now found worldwide, and often need treatment with older, highly toxic antimicrobial regimens. Newer ß-lactamase inhibitors such as avibactam have well-established activity against certain carbapenemases such as Klebsiella pneumoniae carbapenemases (KPC), but have no activity against MBL-producing organisms. Conversely, aztreonam has activity against MBL-producing organisms but is often inactivated by other co-existing ß-lactamases. Here, we report four cases of invasive MBL-CPE infections in transplant recipients caused by IMP-4-producing Enterobacter cloacae who were successfully treated with a new, mechanism-driven antimicrobial combination of ceftazidime/avibactam with aztreonam. This novel antimicrobial combination offers a useful treatment option for high-risk patients with CPE infection, with reduced drug interactions and toxicity.

Oral Fosfomycin Efficacy with Variable Urinary Exposures following Single and Multiple Doses against Enterobacterales: the Importance of Heteroresistance for Growth Outcome.

Oral fosfomycin trometamol is licensed as a single oral dose for the treatment of uncomplicated urinary tract infections, with activity against multidrug-resistant uropathogens. The impact of interindividual variability in urinary concentrations on antimicrobial efficacy, and any benefit of giving multiple doses, is uncertain. We therefore performed pharmacodynamic profiling of oral fosfomycin, using a dynamic bladder infection in vitro model, to assess high and low urinary exposures following a single oral dose and three repeat doses given every 72 h, 48 h, and 24 h against 16 clinical isolates with various MICs of fosfomycin (8 Escherichia coli, 4 Enterobacter cloacae, and 4 Klebsiella pneumoniae isolates). Baseline fosfomycin high-level-resistant (HLR) subpopulations were detected prior to drug exposure in half of the isolates (2 E. coli, 2 E. cloacae, and 4 K. pneumoniae isolates; proportion, 1 × 10-5 to 5 × 10-4% of the total population). Fosfomycin exposures were accurately reproduced compared to mathematical modeling (linear regression slope, 1.1; R2, 0.99), with a bias of 3.8% ± 5.7%. All 5/5 isolates with MICs of ≤1 µg/ml had no HLR and were killed, whereas 8/11 isolates with higher MICs regrew regardless of exposure to high or low urinary concentrations. A disk diffusion zone of <24 mm was a better predictor for baseline HLR and regrowth. Administering 3 doses with average exposures provided very limited additional kill. These results suggest that baseline heteroresistance is important for treatment response, while increased drug exposure and administering multiple doses may not be better than standard single-dose fosfomycin therapy.

Oral Fosfomycin Treatment for Enterococcal Urinary Tract Infections in a Dynamic In Vitro Model.

There are limited treatment options for enterococcal urinary tract infections, especially vancomycin-resistant Enterococcus (VRE). Oral fosfomycin is a potential option, although limited data are available guiding dosing and susceptibility. We undertook pharmacodynamic profiling of fosfomycin against E. faecalis and E. faecium isolates using a dynamic in vitro bladder infection model. Eighty-four isolates underwent fosfomycin agar dilution susceptibility testing (E. faecalis MIC50/90 32/64 µg/ml; E. faecium MIC50/90 64/128 µg/ml). Sixteen isolates (including E. faecalis ATCC 29212 and E. faecium ATCC 35667) were chosen to reflect the MIC range and tested in the bladder infection model with synthetic human urine (SHU). Under drug-free conditions, E. faecium demonstrated greater growth restriction in SHU compared to E. faecalis (E. faecium maximal growth 5.8 ± 0.6 log10 CFU/ml; E. faecalis 8.0 ± 1.0 log10 CFU/ml). Isolates were exposed to high and low fosfomycin urinary concentrations after a single dose, and after two doses given over two days with low urinary concentration exposure. Simulated concentrations closely matched the target (bias 2.3%). E. faecalis isolates required greater fosfomycin exposure for 3 log10 kill from the starting inoculum compared with E. faecium The ƒAUC0-72/MIC and ƒ%T > MIC0-72 for E. faecalis were 672 and 70%, compared to 216 and 51% for E. faecium, respectively. There was no rise in fosfomycin MIC postexposure. Two doses of fosfomycin with low urinary concentrations resulted in equivalent growth inhibition to a single dose with high urinary concentrations. With this urinary exposure, fosfomycin was effective in promoting suppression of regrowth (>3 log10 kill) in the majority of isolates.

Efficacy of single and multiple oral doses of fosfomycin against Pseudomonas aeruginosa urinary tract infections in a dynamic in vitro bladder infection model.

OBJECTIVES: We used a dynamic bladder infection in vitro model with synthetic human urine (SHU) to examine fosfomycin exposures to effectively kill, or prevent emergence of resistance, among Pseudomonas aeruginosa isolates. METHODS: Dynamic urinary fosfomycin concentrations after 3 g oral fosfomycin were simulated, comparing single and multiple (daily for 7 days) doses. Pharmacodynamic response of 16 P. aeruginosa (MIC range 1 to >1024 mg/L) were examined. Baseline disc diffusion susceptibility, broth microdilution MIC and detection of heteroresistance were assessed. Pathogen kill and emergence of resistance over 72 h following a single dose, and over 216 h following daily dosing for 7 days, were investigated. The fAUC0-24/MIC associated with stasis and 1, 2 and 3 log10 kill were determined. RESULTS: Pre-exposure high-level resistant (HLR) subpopulations were detected in 11/16 isolates after drug-free incubation in the bladder infection model. Five of 16 isolates had >2 log10 kill after single dose, reducing to 2/16 after seven doses. Post-exposure HLR amplification occurred in 8/16 isolates following a single dose and in 11/16 isolates after seven doses. Baseline MIC ≥8 mg/L with an HLR subpopulation predicted post-exposure emergence of resistance following the multiple doses. A PK/PD target of fAUC0-24/MIC >5000 was associated with 3 log10 kill at 72 h and 7 day-stasis. CONCLUSIONS: Simulated treatment of P. aeruginosa urinary tract infections with oral fosfomycin was ineffective, despite exposure to high urinary concentrations and repeated daily doses for 7 days. Emergence of resistance was observed in the majority of isolates and worsened following prolonged therapy. Detection of a baseline resistant subpopulation predicted treatment failure.

Impact of bacterial species and baseline resistance on fosfomycin efficacy in urinary tract infections.

OBJECTIVES: To assess the antibacterial effects of a single 3 g oral fosfomycin dose on Escherichia coli and Klebsiella pneumoniae clinical isolates within a dynamic bladder infection model. METHODS: An in vitro model simulating dynamic urinary fosfomycin concentrations was used. Target fosfomycin exposure (Cmax = 1984 mg/L and Tmax = 7.5 h) was validated by LC-MS/MS. Pharmacodynamic responses of 24 E. coli and 20 K. pneumoniae clinical isolates were examined (fosfomycin MIC ≤0.25-128 mg/L). Mutant prevention concentration (MPC), fosfomycin heteroresistance, fosfomycin resistance genes and fosA expression were examined. Pathogen kill and emergence of high-level resistance (HLR; MIC >1024 mg/L) were quantified. RESULTS: Following fosfomycin exposure, 20 of 24 E. coli exhibited reductions in bacterial counts below the lower limit of quantification without regrowth, despite baseline fosfomycin MICs up to 128 mg/L. Four E. coli regrew (MIC = 4-32 mg/L) with HLR population replacement. At baseline, these isolates had detectable HLR subpopulations and MPC >1024 mg/L. All E. coli isolates were fosA negative. In contrast, 17 of 20 K. pneumoniae regrew post exposure, 6 with emergence of HLR (proportion = 0.01%-100%). The three isolates without regrowth did not have a detectable HLR subpopulation after dynamic drug-free incubation. All K. pneumoniae had MPC >1024 mg/L and were fosA positive. WGS analysis and fosA expression failed to predict fosfomycin efficacy. CONCLUSIONS: E. coli and K. pneumoniae isolates demonstrate discrepant responses to a single fosfomycin dose in a dynamic bladder infection in vitro model. Treatment failure against E. coli was related to an HLR subpopulation, not identified by standard MIC testing. Activity against K. pneumoniae appeared limited, regardless of MIC testing, due to universal baseline heteroresistance.

Evolution of Daptomycin Resistance in Coagulase-Negative Staphylococci Involves Mutations of the Essential Two-Component Regulator WalKR.

Coagulase-negative staphylococci (CoNS) represent one of the major causes of health care- and medical device-associated infections. Emerging antimicrobial resistance has complicated the treatment of systemic infections caused by CoNS. Here, we describe the prevalence of antimicrobial resistance in clinical CoNS strains from a tertiary care hospital over a 4-year period, and we observed a significant increase in resistance to daptomycin. Notably, Staphylococcus capitis accounted for the majority of these daptomycin-resistant (DAP-R) CoNS. To further investigate the mechanisms of daptomycin resistance in CoNS, daptomycin-susceptible clinical strains of S. capitis and Staphylococcus epidermidis underwent in vitro daptomycin exposure to generate DAP-R CoNS mutants. Unlike that seen with Staphylococcus aureus, alteration of cell surface charge was not observed in the DAP-R CoNS strains, but biofilm formation was compromised. Whole-genome sequencing analysis of the DAP-R CoNS strains identified single nucleotide polymorphisms (SNPs) in walKR, the essential two-component regulatory system controlling cell wall biogenesis. PCR and sequencing of walK and walR from 17 DAP-R CoNS clinical isolates identified seven nonsynonymous mutations. The results were confirmed by the recreation of the walK SNP in S. epidermidis, which resulted in reduced susceptibility to daptomycin and vancomycin. This study highlights the significance of CoNS in evolving daptomycin resistance and showed that walKR is shared among the staphylococcal species and is involved in antibiotic resistance development. Notably, we did not observe mutations in genes responsible for phospholipid biosynthesis or an altered cell surface charge, suggesting that reduced daptomycin susceptibility in CoNS may emerge in a fashion distinct from that in S. aureus.

Fosfomycin efficacy and emergence of resistance among Enterobacteriaceae in an in vitro dynamic bladder infection model.

Background: Urinary tract infections (UTIs) are among the most common bacterial infections and a frequent indication for antibiotic use. Fosfomycin, an important oral antibiotic for outpatient UTIs, remains a viable option for MDR uropathogens. We aimed to perform pharmacodynamic profiling simulating urinary concentrations to assess the adequacy of the current dosing regimen. Methods: A dynamic in vitro bladder infection model was developed, replicating urinary fosfomycin concentrations after gastrointestinal absorption, systemic distribution and urinary elimination. Concentrations were measured by LC-MS/MS. Twenty-four Enterobacteriaceae strains (Escherichia coli, Klebsiella pneumoniae and Enterobacter cloacae; MIC range 0.25-64 mg/L) were examined. Pathogen kill and emergence of resistance was assessed over 72 h. Results: Observed in vitro fosfomycin concentrations accurately simulated urinary fosfomycin exposures (Tmax 3.8 ±âŸ0.5 h; Cmax 2630.1 ±âŸ245.7 mg/L; AUC0-24 33 932.5 ±âŸ1964.2 mg·h/L). Fifteen of 24 isolates regrew, with significant rises in fosfomycin MIC (total population MIC50 4 to 64 mg/L, MIC90 64 to > 1024 mg/L, P = 0.0039; resistant subpopulation MIC50 128 to > 1024 mg/L, MIC90 >1024 mg/L, P = 0.0020). E. coli and E. cloacae isolates were killed with pharmacokinetic/pharmacodynamic EI50 of fAUC0-24/MIC = 1922, fCmax/MIC = 149 and fTime>4×MIC = 44 h. In contrast, K. pneumoniae isolates were not reliably killed. Conclusions: Using dynamic in vitro simulations of urinary fosfomycin exposures, E. coli and E. cloacae isolates with MIC >16 mg/L, and all K. pneumoniae isolates, were not reliably killed. Emergence of resistance was significant. This challenges fosfomycin dosing and clinical breakpoints, and questions the utility of fosfomycin against K. pneumoniae. Further work on in vitro dose optimization is required.

Herpes simplex virus-2 transmission following solid organ transplantation: Donor-derived infection and transplantation from prior organ recipients.

BACKGROUND: Owing to limited availability of donor organs, previous solid organ transplant (SOT) recipients are increasingly considered as potential organ donors. We report donor-derived transmission of herpes simplex virus type-2 (HSV-2) to two clusters of SOT recipients with transmission from the original donor and an HSV-2-infected recipient who subsequently became a donor. METHODS: We reviewed medical records of the donors and recipients in both clusters. Pre-transplant serology and virological features of HSV-2 were characterized. Genotyping of HSV-2 isolates to determine potential for donor transmission of HSV-2 through transplantation of organs from prior organ recipients was performed. RESULTS: A kidney-pancreas recipient died day 9 post transplant. Following confirmation of brain death, the lungs and recently transplanted kidney were donated to two further recipients. The liver was not retrieved, but biopsy confirmed HSV-2 infection. Testing on the original donor showed negative HSV-2 polymerase chain reaction and HSV immunoglobulin (Ig)M, but positive HSV-2 IgG. The liver recipient from the original donor developed HSV-2 hepatitis and cutaneous infection that responded to treatment with intravenous acyclovir. In the second cluster, lung and kidney recipients both developed HSV-2 viremia that was successfully treated with antiviral therapy. Genotyping of all HSV-2-positive samples showed 100% sequence homology for three recipients. CONCLUSIONS: Donor-derived HSV infection affected two clusters of recipients because of transplantation of organs from a prior organ recipient. HSV should be considered as a possible cause of illness in febrile SOT recipients in the immediate post-transplant period and may cause disseminated disease and re-infection in HSV-2-seropositive recipients. Testing of HSV serology and prophylaxis may be considered in SOT recipients not receiving cytomegalovirus prophylaxis.

Epstein-Barr virus encephalitis in solid organ transplantation.

Epstein-Barr virus (EBV) is typically associated with post transplant lymphoproliferative disease (PTLD) after solid organ and stem cell transplantation. However, it is rarely associated with neurological complications. We report a case of severe encephalitis complicating primary EBV infection six months post renal transplantation, and review the literature on EBV encephalitis in solid organ transplantation in adults. A 55-year-old male presented 6 months post cadaveric renal transplant with headache, fever and confusion. Neuroimaging was unremarkable, but an electroencephalogram was consistent with diffuse encephalopathy. EBV DNA was detected in both cerebrospinal fluid (13,177 copies/ml), and plasma (14,166 copies/ml). Management included reduction of immunosuppression, intravenous ganciclovir and intravenous immunoglobulin, and resulted in a reduction in EBV viral load in both plasma and cerebrospinal fluid. The patient made a full recovery with no long-term neurological deficits and preservation of the graft. This case highlights the importance of knowing donor and recipient EBV serostatus at time of transplant, and closely monitoring EBV DNA when there is a mismatch. Ganciclovir or valganciclovir prophylaxis has also been shown to reduce the incidence of primary EBV infection in renal transplantation in these recipients. Treatment options for EBV infection post-transplant include reduction of immunosuppression, antiviral therapy, IVIg, and monoclonal antibody therapy directed toward infected B lymphocytes.

Lab on a chip sensor for rapid detection and antibiotic resistance determination of Staphylococcus aureus.

The Gram-positive bacterium, Staphylococcus aureus (S. aureus), is a major pathogen responsible for a variety of infectious diseases ranging from cellulitis to more serious conditions such as septic arthritis and septicaemia. Timely treatment with appropriate antibiotic therapy is essential to ensure clinical defervescence and to prevent further complications such as infective endocarditis or organ impairment due to septic shock. To date, initial antibiotic choice is empirical, using a "best guess" of likely organism and sensitivity- an approach adopted due to the lack of rapid identification methods for bacteria. Current culture based methods take up to 5 days to identify the causative bacterial pathogen and its antibiotic sensitivity. This paper provides proof of concept for a biosensor, based on interdigitated electrodes, to detect the presence of S. aureus and ascertain its sensitivity to flucloxacillin rapidly (within 2 hours) in a cost effective manner. The proposed method is label-free and uses non-faradic measurements. This is the first study to successfully employ interdigitated electrodes for the rapid detection of antibiotic resistance. The method described has important potential outcomes of faster definitive antibiotic treatment and more rapid clinical response to treatment.

Stenotrophomonas, Achromobacter, and nonmelioid Burkholderia species: antimicrobial resistance and therapeutic strategies.

Stenotrophomonas maltophilia, Achromobacter xylosoxidans, and nonmelioid Burkholderia species, namely, Burkholderia cepacia complex, collectively are a group of troublesome nonfermenters. Although not inherently virulent organisms, these environmental Gram negatives can complicate treatment in those who are immunocompromised, critically ill in the intensive care unit and those patients with suppurative lung disease, such as cystic fibrosis. Through a range of intrinsic antimicrobial resistance mechanisms, virulence factors, and the ability to survive in biofilms, these opportunistic pathogens are well suited to persist, both in the environment and the host. Treatment recommendations are hindered by the difficulties in laboratory identification, the lack of reproducibility of antimicrobial susceptibility testing, the lack of clinical breakpoints, and the absence of clinical outcome data. Despite trimethoprim-sulfamethoxazole often being the mainstay of treatment, resistance is widely encountered, and alternative regimens, including combination therapy, are often used. This review will highlight the important aspects and unique challenges that these three nonfermenters pose, and, in the absence of clinical outcome data, our therapeutic recommendations will be based on reported antimicrobial susceptibility and pharmacokinetic/pharmacodynamic profiles.

Prescribing trends before and after implementation of an antimicrobial stewardship program.

OBJECTIVES: Antimicrobial stewardship programs are recommended to reduce antimicrobial resistance by reducing inappropriate use of antimicrobials. We implemented an antimicrobial stewardship program and aimed to evaluate its effect on broad-spectrum antimicrobial use. DESIGN, SETTING AND PARTICIPANTS: Observational study with historical control using interrupted time series analysis conducted in a tertiary referral hospital. Hospital inpatients prescribed restricted antimicrobials for non-standard indications, where approval had expired or without approval. INTERVENTION: Baseline period of 30 months immediately followed by an 18-03 intervention period commencing January 2011. MAIN OUTCOME MEASURES: Number and type of interventions made by antimicrobial stewardship team; monthly rate of use of broad-spectrum antimicrobial agents (in defined daily doses/1000 occupied bed-18s). RESULTS: The antimicrobial stewardship team made 1104 recommendations in 779 patients during the 18-03 intervention period. In 64% of cases, the recommendation was made to cease or de-escalate the antimicrobial therapy, or to change from intravenous to oral therapy. The introduction of the intervention resulted in an immediate 17% (95% CI, 13%-20%) reduction in broad-spectrum antimicrobial use in the intensive care unit and a 10% (95% CI, 4%-16%) reduction in broad-spectrum antimicrobial use outside the intensive care unit. Reductions were particularly seen in cephalosporin and glycopeptide use, although these were partially offset by increases in the use of ß-lactam-ß-lactamase inhibitors. CONCLUSIONS: The introduction of an antimicrobial stewardship program, including postprescription review, resulted in an immediate reduction in broad-spectrum antimicrobial use in a tertiary referral centre. However, the effect of this intervention reduced over time.