James S. Molton

The Global Spread of Healthcare-Associated Multidrug-Resistant Bacteria: A Perspective From Asia

Since antibiotics were first used, each new introduced class has been followed by a global wave of emergent resistance, largely originating in Europe and North America where they were first used. Methicillin-resistant Staphylococcus aureus spread from the United Kingdom and North America across Europe and then Asia over more than a decade. Vancomycin-resistant enterococci and Klebsiella pneumoniae carbapenemase-producing K. pneumoniae followed a similar path some 20 years later. Recently however, metallo-β-lactamases have originated in Asia. New Delhi metallo-β-lactamase-1 was found in almost every continent within a year of its emergence in India. Metallo-β-lactamase enzymes are encoded on highly transmissible plasmids that spread rapidly between bacteria, rather than relying on clonal proliferation. Global air travel may have helped facilitate rapid dissemination. As the antibiotic pipeline offers little in the short term, our most important tools against the spread of antibiotic resistant organisms are intensified infection control, surveillance, and antimicrobial stewardship.

Differential host susceptibility and bacterial virulence factors driving Klebsiella liver abscess in an ethnically diverse population

Hypervirulent Klebsiella pneumoniae is an emerging cause of community-acquired pyogenic liver abscess. First described in Asia, it is now increasingly recognized in Western countries, commonly afflicting those with Asian descent. This raises the question of genetic predisposition versus geospecific strain acquisition. We leveraged on the Antibiotics for Klebsiella Liver Abscess Syndrome Study (A-KLASS) clinical trial ongoing in ethnically diverse Singapore, to prospectively examine the profiles of 70 patients together with their isolates’ genotypic and phenotypic characteristics. The majority of isolates belonged to capsule type K1, a genetically homogenous group corresponding to sequence-type 23. The remaining K2, K5, K16, K28, K57 and K63 isolates as well as two novel cps isolates were genetically heterogeneous. K1 isolates carried higher frequencies of virulence-associated genes including rmpA (regulator of mucoid phenotype A), kfu (Klebsiella ferric uptake transporter), iuc (aerobactin), iro (salmochelin) and irp (yersiniabactin) than non-K1 isolates. The Chinese in our patient cohort, mostly non-diabetic, had higher prevalence of K1 infection than the predominantly diabetic non-Chinese (Malays, Indian and Caucasian). This differential susceptibility to different capsule types among the various ethnic groups suggests patterns of transmission (e.g. environmental source, familial transmission) and/or genetic predisposition unique to each race despite being in the same geographical location.

Impact of Regional Vein Thrombosis in Patients with Klebsiella pneumoniae Liver Abscess

Klebsiella liver abscess (KLA) is an emerging infection in Asia caused by hypermucoviscous strains of Klebsiella pneumoniae. It is associated with thrombophlebitis of portal and hepatic veins. The natural history and role of anticoagulation for this regional thrombophlebitis is unclear. In a retrospective study of 169 subjects with KLA over 7 years, thrombophlebitis was identified in 53/169 (31.4%). Only 1 received therapeutic anticoagulation. Despite this 30/49 (73.2%) of those with follow up scan available showed improvement or recanalization (mean duration between scans 44 days). Abscess resolution was associated with improvement in thrombophlebitis.

Prospective single-arm interventional pilot study to assess a smartphone-based system for measuring and supporting adherence to medication

Objectives Suboptimal medication adherence for infectious diseases such as tuberculosis (TB) results in poor clinical outcomes and ongoing infectivity. Directly observed therapy (DOT) is now standard of care for TB treatment monitoring but has a number of limitations. We aimed to develop and evaluate a smartphone-based system to facilitate remotely observed therapy via transmission of videos rather than in-person observation. Design We developed an integrated smartphone and web-based system (Mobile Interactive Supervised Therapy, MIST) to provide regular medication reminders and facilitate video recording of pill ingestion at predetermined timings each day, for upload and later review by a healthcare worker. We evaluated the system in a single arm, prospective study of adherence to a dietary supplement. Healthy volunteers were recruited through an online portal. Entry criteria included age ≥21 and owning an iOS or Android-based device. Participants took a dietary supplement pill once, twice or three-times a day for 2 months. We instructed them to video each pill taking episode using the system. Outcome Adherence as measured by the smartphone system and by pill count. Results 42 eligible participants were recruited (median age 24; 86% students). Videos were classified as received—confirmed pill intake (3475, 82.7% of the 4200 videos expected), received—uncertain pill intake (16, <1%), received—fake pill intake (31, <1%), not received—technical issues (223, 5.3%) or not received—assumed non-adherence (455, 10.8%). Overall median estimated participant adherence by MIST was 90.0%, similar to that obtained by pill count (93.8%). There was a good relationship between participant adherence as measured by MIST and by pill count (Spearmans rs 0.66, p<0.001). Conclusions We have demonstrated the feasibility, acceptability and accuracy of a smartphone-based adherence support and monitoring system. The system has the potential to supplement and support the provision of DOT for TB and also to improve adherence in other conditions such as HIV and hepatitis C.

Population genomics of hypervirulent Klebsiella pneumoniae clonal-group 23 reveals early emergence and rapid global dissemination

Severe liver abscess infections caused by hypervirulent clonal-group CG23 Klebsiella pneumoniae have been increasingly reported since the mid-1980s. Strains typically possess several virulence factors including an integrative, conjugative element ICEKp encoding the siderophore yersiniabactin and genotoxin colibactin. Here we investigate CG23’s evolutionary history, showing several deep-branching sublineages associated with distinct ICEKp acquisitions. Over 80% of liver abscess isolates belong to sublineage CG23-I, which emerged in ~1928 following acquisition of ICEKp10 (encoding yersiniabactin and colibactin), and then disseminated globally within the human population. CG23-I’s distinguishing feature is the colibactin synthesis locus, which reportedly promotes gut colonisation and metastatic infection in murine models. These data show circulation of CG23 K. pneumoniae decades before the liver abscess epidemic was first recognised, and provide a framework for future epidemiological and experimental studies of hypervirulent K. pneumoniae. To support such studies we present an open access, completely sequenced CG23-I human liver abscess isolate, SGH10.Since the 1980s, hypervirulent clonal-group CG23 serotype K1 Klebsiella pneumoniae has been recognised as a prominent cause of community-acquired liver abscess and other severe infections. Here, the authors investigate the genomic evolutionary history of CG23 and suggest a new reference strain for CG23.

A comparison of 18F-FDG PET/MR with PET/CT in pulmonary tuberculosis

Purpose PET/computed tomography (CT) has been shown to detect lesions in patients with pulmonary tuberculosis (PTB) and may be useful for assessing PTB disease in clinical research studies. However, radiation dose is of concern for clinical research in individuals with an underlying curable disease. This study aimed to determine whether PET/MR is equivalent to PET/CT in PTB. Materials and methods Ten patients with microbiologically confirmed PTB were recruited. Patients received 129.0±4.1 MBq of fluorine-18-fluorodeoxyglucose. Five of the 10 patients underwent a PET/MR scan, followed by PET/CT. The remaining five were first imaged on the PET/CT, followed by the PET/MRI. PET acquisition began at 66.7±14.4 min (mean±SD) after injection when performing PET/MR first (PET/CT: 117.2±5.6 min) and 92.4±7.6 min when patients were imaged on PET/MR second (PET/CT: 61.1±3.9 min). PET data were reconstructed iteratively with Ordinary-Poisson Ordered-Subset Expectation-Maximization and reconstruction parameters were matched across the two scanners. A visual lesion detection task and a standardized uptake value (SUV) analysis were carried out. The CT Hounsfield unit values of PTB lesions were also compared with MR-based attenuation correction mu-map tissue classes. Results A total of 108 PTB lesions were detected on PET/MR and 112 on PET/CT. SUV analysis was carried out on 50 of these lesions that were observed with both modalities. Mean standardized uptake value (SUVmean) and maximum standardized uptake value (SUVmax) were significantly lower on PET/MR (SUVmean: 2.6±1.4; SUVmax: 4.3±2.5) than PET/CT (SUVmean: 3.5±1.5; SUVmax: 5.3±2.4). Conclusion PET/MR visual performance was shown to be comparable to PET/CT in terms of the number of PTB lesions detected. SUVs were significantly lower on PET/MR. Dixon-based attenuation correction underestimates the linear attenuation coefficient of PTB lesions, resulting in lower SUVs compared with PET/CT. However, the use of PET/MR to measure the response of lung lesions to assess response to treatment in research studies is unlikely to be affected by these differences in quantification.

Comparison of diabetic and non-diabetic human leukocytic responses to different capsule types of klebsiella pneumoniae responsible for causing pyogenic liver abscess

The major risk factor for Klebsiella liver abscess (KLA) is type 2 diabetes mellitus (DM), but the immunological mechanisms involved in the increased susceptibility are poorly defined. We investigated the responses of neutrophils and peripheral blood mononuclear cells (PBMCs) to hypervirulent Klebsiella pneumoniae (hvKP), the causative agent of KLA. DNA and myeloperoxidase levels were elevated in the plasma of KLA patients compared to uninfected individuals indicating neutrophil activation, but diabetic status had no effect on these neutrophil extracellular trap (NET) biomarkers in both subject groups. Clinical hvKP isolates universally stimulated KLA patient neutrophils to produce NETs ex vivo, regardless of host diabetic status. Ability of representative capsule types (K1, K2, and non-K1/K2 strains) to survive intra- and extra-cellular killing by type 2 DM and healthy neutrophils was subsequently examined. Key findings were: (1) type 2 DM and healthy neutrophils exhibited comparable total, phagocytic, and NETs killing against hvKP, (2) phagocytic and NETs killing were equally effective against hvKP, and (3) hypermucoviscous K1 and K2 strains were more resistant to total, phagocytic, and NETs killing compared to the non-mucoviscous, non-K1/K2 strain. The cytokine response and intracellular killing ability of type 2 DM as well as healthy PBMCs upon encounter with the different capsule types was also examined. Notably, the IL-12–IFNγ axis and its downstream chemokines MIG, IP-10, and RANTES were produced at slightly lower levels by type 2 DM PBMCs than healthy PBMCs in response to representative K1 and non-K1/K2 strains. Furthermore, type 2 DM PBMCs have a mild defect in its ability to control hvKP replication relative to healthy PBMCs. In summary, our work demonstrates that type 2 DM does not overtly impact neutrophil intra- and extra-cellular killing of hvKP, but may influence cytokine/chemokine production and intracellular killing by PBMCs.

A Novel Approach to CT, MR, and PET Examination of Patients with Infections Requiring Stringent Airborne Precautions

PURPOSE To investigate the feasibility of using a modified portable isolation chamber, which conforms to Centers for Disease Control and Prevention (CDC) isolation requirements, in the imaging of infectious patients. MATERIALS AND METHODS This study was approved by the ethics committee, and all participants gave written informed consent. In this prospective study, the isolation chamber was assessed for computed tomographic (CT), magnetic resonance (MR), and positron emission tomographic (PET) image uniformity and noise by using uniform phantoms. For each modality, equivalent phantom examinations were performed without the isolation chamber. Paired analyses of the differences from these baseline values were conducted by finding the mean difference in the matched sections for each image quality parameter. A potential increase in CT patient dose was assessed, and MR radiofrequency (RF) interference was monitored. Eight participants with active pulmonary tuberculosis (mean age, 48.1 years; age range, 26-88 years; five men, three women) were then examined within a hybrid PET/MR imager. The 95% confidence intervals for the difference in the two matched population means were determined by using the two-sided t distribution for each of the phantom study imaging modalities. RESULTS Phantom images were evaluated for image uniformity and noise. Increased image noise can affect low contrast resolution, which has the potential to mimic or mask abnormalities when the differences between healthy and diseased tissues are small; clinically, CT image noise is maintained at a constant level with dose modulation. Increased attenuation of annihilation photons, when not corrected for, could lead to photopenic areas on the PET image; PET image nonuniformity complied with guidelines. Artifacts on the MR image due to RF noise spikes could mask abnormalities; paired analysis of variations in MR imaging mean signal-to-noise ratio and uniformity from baseline were within 5% for both gradient-echo and spin-echo sequences. In the eight participants who underwent imaging, the increased radiation dose for the attenuation of the isolation chamber would have resulted in a mean increase in patient size-specific dose estimate of 0.32 mGy ± 0.04 (standard deviation). The RF noise assessment revealed no prominent increase at any frequency band. The eight participants were examined within the isolation chamber without incident. CONCLUSION A modified portable isolation chamber, which conforms to CDC infection control guidelines, was found to be feasible within the confines of CT, MR imaging, and PET environments.

Dengue virus not detected in human semen

Zika and Ebola viruses can persist in semen and pose a risk for sexual transmission. To determine if dengue virus, another flavivirus, is similarly detectable in semen, we performed dengue PCR on semen in five patients with acute dengue virus infection. All five tested negative, suggesting that dengue does not pose a risk for sexual transmission.