Quadriceps tendon malalignment is an independent anatomical deformity which is the primary abnormality associated with lateral facet patellofemoral joint osteoarthritis

PURPOSE

The purposes of this study are to, firstly, develop techniques to accurately identify extensor mechanism malalignment by measuring the alignment of the quadriceps tendon (QTA) with computerized tomography (CT) scans. Secondly, to investigate correlations between QTA and lower limb bony anatomical variations within a representative normal population. Lastly, to evaluate the clinical significance of QTA by establishing its potential connection with lateral facet patellofemoral joint osteoarthritis (LFPFJOA).

METHOD

CT scans were orientated to a mechanical axis reference frame and three techniques developed to measure the alignment of the quadriceps tendon. Multiple measurement of bony alignment from the hip to the ankle were performed on each scan. A series of 110 cadaveric CT scans were measured to determine normal values, reproducibility, and correlations with bony anatomy. Secondly, a comparison between 2 groups of 25 patients, 1 group with LFPFJOA and 1 group with isolated medial OA and no LFPFJOA.

RESULTS

From the cadaveric study, it was determined that the alignment of the quadriceps tendon is on average 4.3° (SD 3.9) varus and the apex of the tendon is 9.1 mm (SD 7.7 mm) lateral to the trochlear groove and externally rotated 1.9° (SD 12.4°) from the centre of the femoral shaft. There was no association between the quadriceps tendon alignment and any other bony measurements including tibial tubercle trochlear groove distance (TTTG), coronal alignment, trochlear groove alignment and femoral neck anteversion. A lateralized QTA was significantly associated with LFPFJOA. QTA in the LFPFJOA group was 9.6° varus (SD 2.8°), 21.3 mm (SD 6.6) lateralised and 17.3° ER (SD 11°) compared to 5.5° (SD 2.3°), 10.7 mm (SD 4.9) and 3.3° (SD 7.2°), respectively, in the control group (p < 0.001). A significant association with LFPFJOA was also found for TTTG (17.2 mm (SD 5.7) vs 12.1 mm (SD 4.3), p < 0.01). Logistic regression analysis confirmed the QTA as having the stronger association with LFPFJOA than TTTG (AUC 0.87 to 0.92 for QTA vs 0.79 for TTTG).

CONCLUSION

These studies have confirmed the ability to accurately determine QTA on CT scans. The normal values indicate that the QTA is highly variable and unrelated to bony anatomy. The comparative study has determined that QTA is clinically relevant and a lateralised QTA is the dominant predictor of severe LFPFJOA. This deformity should be considered when assessing patella maltracking associated with patella osteoarthritis, patella instability and arthroplasty.

LEVEL OF EVIDENCE

III (retrospective cohort study).

BRCA1 and BRCA2 carriers with breast, ovarian and prostate cancer demonstrate a different pattern of metastatic disease compared with non-carriers: results from a rapid autopsy programme

AIM

To catalogue and compare the pattern of metastatic disease in germline BRCA1/2 pathogenic mutation carriers and non-carriers with breast, ovarian and prostate cancer from a rapid autopsy programme.

METHODS AND RESULTS

The number of metastases in the major body systems and the proportion of participants with metastases were documented in 50 participants (19 germline mutation carriers). Analysis was conducted on the participants' pattern of disease for the different cancers and mutation subgroups. The four commonly affected organ systems were the digestive (liver only) (82%), respiratory (76%), gastrointestinal (65%) and reticuloendothelial (42%). There were significant differences in the pattern of metastatic breast cancer in BRCA1/2 germline carriers compared with non-carriers. Breast cancer carriers had significantly fewer organ systems involved (median n = 3, range = 1-3) compared with non-carriers (median n = 9, range = 1-7) (P = 0.03). BRCA1/2 carriers with ovarian carcinomas had significantly more organ systems with metastatic carcinoma (median n = 10, range = 3-8) than non-carriers (median n = 5, range = 3-5) (P < 0.001). There were no significant differences in the number of involved systems in BRCA2 carriers compared with non-carriers with prostate cancer (P = 1.0). There was an absence of locoregional disease (6.5%) compared with distant disease (93.5%) among the three cancer subtypes (P < 0.001). The majority of metastatic deposits (97%) collected during the autopsy were identified by recent diagnostic imaging.

CONCLUSION

Even though a major limitation of this study is that our numbers are small, especially in the breast cancer carrier group, the metastatic patterns of breast and ovarian cancers may be impacted by BRCA1/2 carrier status, suggesting that tumours derived from patients with these mutations use different mechanisms of dissemination. The findings may focus clinical diagnostic imaging for monitoring metastases where whole-body imaging resources are scant.

Survey on postmortem screening and management of COVID-19 related deaths

The COVID-19 pandemic is associated with a high case fatality rate in some countries even thought the majority of cases are asymptomatic. Scientific studies on this novel virus is limited and there is uncertainty regarding the best practices for death investigations both in terms of detection of the disease as well as autopsy safety. An online survey was conducted to identify how different institutions responded to the screening and management of dead bodies during the early phase of the pandemic from January to May. A questionnaire was developed using Google Forms and data was collected from 14 different forensic and pathological institutions in 9 countries. None of the institutions had performed any screening prior to March. Four institutions stated that screening was done routinely. In total, 322 cases had been screened using RT-PCR, out of which 40 positive cases were detected among four institutions. The commonest types of samples obtained were nasopharyngeal and oropharyngeal swabs which also had the highest rates of positivity followed by tracheal swab. Blood, swabs from cut surfaces of lung and lung tissue also gave positive results in some cases. Majority of the positive cases were > 65 years with a history suggestive of respiratory infection and were clinically suspected to have COVID-19 before death. Except for one institution which performed limited dissections, standard autopsies were conducted on all positive cases. Disposal of bodies involved the use of sealed body bags and labelling as COVID positive. Funeral rites were restricted and none of the institutions advocated cremation. There were no reports of disease transmission to those who handled COVID positive bodies.

Post-mortem CT lung findings at a medicolegal institute in SARS-CoV-2 RT-PCR positive cases with autopsy correlation

CoVID-19 is a novel viral infection with now well-established clinical radiological findings. There is limited data on post-mortem imaging. We explore the proposition that PMCT could be used as screening test. In an 11-week period, 39 deceased persons were referred for medicolegal investigation with pre-existing or subsequent nasopharyngeal swabs showing positivity on SARS-CoV-2 RT-PCR testing. All 39 had routine whole-body CT scans on admission and 12 underwent medicolegal autopsy. These cases were contrasted with 4 others which were negative on nasopharyngeal swabs despite PMCT findings suggestive of CoVID-19 pneumonia (designated false positive). Nine of the 12 autopsies showed lung histology consistent with those reported in CoVID-19 pneumonia. Typical clinical CoVID-19 lung findings on PMCT were only detected in 5 (42%). In 3 of the 4 false positive cases, lung findings showed non-COVID-19 histology but in 1, findings were identical. PMCT CoVID-19 findings in the lungs are therefore not specific and may not be detected in all cases due to obscuration by expected agonal CT findings or other pathologies that pre-dated SARS-CoV-2 infection. PMCT findings may otherwise be subtle. Although PMCT may hint at CoVID-19, we believe that nasopharyngeal swabs are still required for definitive diagnosis. Even with positive swabs, clinical CoVID-19 lung findings on PMCT are often not detected. PMCT findings can be subtle, extreme or obscured by agonal changes. Given this range of PMCT changes, the challenge for pathologists is to determine whether death has been caused by, or merely associated with, SARS-CoV-2 infection.

The effect of intestinal microbiota dysbiosis on growth and detection of carbapenemase-producing Enterobacterales within an in vitro gut model

BACKGROUND

Carbapenemase-producing Enterobacterales (CPE) can colonize the gut and are of major clinical concern. Identification of CPE colonization is problematic; there is no gold-standard detection method, and the effects of antibiotic exposure and microbiota dysbiosis on detection are unknown.

AIM

Based on a national survey we selected four CPE screening assays in common use. We used a clinically reflective in vitro model of human gut microbiota to investigate the performance of each test to detect three different CPE strains under different, clinically relevant antibiotic exposures.

METHODS

Twelve gut models were seeded with a pooled faecal slurry and exposed to CPE either before, after, concomitant with, or in the absence of piperacillin-tazobactam (358 mg/L, 3 × daily, seven days). Total Enterobacterales and CPE populations were enumerated daily. Regular screening for CPE was performed using Cepheid Xpert® Carba-R molecular test, and with Brilliance™ CRE, Colorex™ mSuperCARBA and CHROMID® CARBA SMART agars.

FINDINGS

Detection of CPE when the microbiota are intact is problematic. Antibiotic exposure disrupts microbiota populations and allows CPE proliferation, increasing detection. The performances of assays varied, particularly with respect to different CPE strains. The Cepheid assay performed better than the three agar methods for detecting a low level of CPE within an intact microbiota, although performance of all screening methods was comparable when CPE populations increased in a disrupted microbiota.

CONCLUSION

CPE strains differed in their dynamics of colonization in an in vitro gut model and in their subsequent response to antibiotic exposure. This affected detection by molecular and screening methods, which has implications for the sensitivity of CPE screening in healthcare settings.

Evolution of late-stage metastatic melanoma is dominated by aneuploidy and whole genome doubling

Although melanoma is initiated by acquisition of point mutations and limited focal copy number alterations in melanocytes-of-origin, the nature of genetic changes that characterise lethal metastatic disease is poorly understood. Here, we analyze the evolution of human melanoma progressing from early to late disease in 13 patients by sampling their tumours at multiple sites and times. Whole exome and genome sequencing data from 88 tumour samples reveals only limited gain of point mutations generally, with net mutational loss in some metastases. In contrast, melanoma evolution is dominated by whole genome doubling and large-scale aneuploidy, in which widespread loss of heterozygosity sculpts the burden of point mutations, neoantigens and structural variants even in treatment-naïve and primary cutaneous melanomas in some patients. These results imply that dysregulation of genomic integrity is a key driver of selective clonal advantage during melanoma progression.

Difference in the characteristics of mortality reports during a heatwave period: retrospective analysis comparing deaths during a heatwave in January 2014 with the same period a year earlier

OBJECTIVES

To describe the characteristics of deaths reported to the Coroners Court of Victoria (CCOV) during Victoria's last heatwave (14-17 January 2014) and subsequent 4 days (18-21 January) using medicolegal data obtained from both the police investigation report and the pathologist's report.

DESIGN, SETTING AND PARTICIPANTS

A single-jurisdiction population-based retrospective analysis of consecutive heat-related deaths (HRDs) reported to the CCOV between 14 and 21 January 2014 with a historical comparison group.

MAIN OUTCOME MEASURES

Descriptive statistics were used to summarise case demographics, causes of death and the types of investigations performed. The cases from 2014 were subgrouped into HRD and non-HRD.

RESULTS

Of the 222 cases during the study period in 2014, 94 (42.3%) were HRDs and 128 (57.7%) were non-HRDs. HRDs were significantly older than non-HRDs (70.5 years: SD=13.8 vs 61.0 years: SD=22.4, t(220)=3.60, p<0.001, 95% CI 4.3 to 14.6). The most common primary cause of death in HRDs was circulatory system disease (n=57, 60.6%), which was significantly higher when compared with non-HRDs (n=39, 30.5%; χ²=20.1, p<0.001, OR 3.5, 95% CI 2.0 to 6.2). HRDs required significantly greater toxicology investigation (89.4% (n=84) vs 71.9% (n=92); χ²=10.9, p<0.001, OR 3.3, 95% CI 1.54 to 7.03) and greater vitreous biochemistry testing (40.4% (n=38) vs 16.4% (n=21); χ²=16.0, p<0.001, OR 3.5, 95% CI 1.9 to 6.5).

CONCLUSIONS

A heatwave places a significant burden on death investigation services. The inclusion of additional laboratory tests and more detailed circumstantial information are essential if the factors that contribute to HRDs are to be identified.

Emergence of Candida auris in Russia

This paper reports the emergence of Candida auris infections in an intensive care unit at a hospital in Moscow. Forty-nine cases were diagnosed in 2016-2017, and the risk factors and antifungal susceptibilities are described. The 30-day all-cause mortality for 19 bloodstream infections in patients who did not receive appropriate antifungal therapy was 42.1%. Phylogenetic analysis of the internal transcribed spacer and D1-D2 regions and K143R substitution in the ERG11 gene indicated that the studied C. auris strains were of South Asian origin. This first reported series of C. auris infections in Russia demonstrates the rapid dissemination of this species, and the need for international surveillance and control measures.

An evaluation of the electronic reporting system for the enhanced surveillance of carbapenemase-producing Gram-negative bacteria in England

BACKGROUND

An electronic reporting system (ERS) for the enhanced surveillance of carbapenemase-producing Gram-negative bacteria (CPGNB) was launched by Public Health England in May 2015.

AIM

This evaluation aimed to assess uptake, timeliness and completeness of data provided and explore potential barriers and facilitators to adopting the system.

METHODS

The evaluation comprised a retrospective analysis of surveillance data and semi-structured interviews with ERS users.

FINDINGS

The proportion of organisms referred for investigation of carbapenem resistance via ERS increased over the first 12 months post-implementation from 35% to 73%; uptake varied widely across regions of England. Completeness of enhanced data fields was poor in 78% of submitted isolates. The median number of days to report confirmatory test results via ERS was 1 day for the regional service and nine days for the national reference laboratory, which additionally conducts phenotypic testing to confirm carbapenemase negativity. Hindrances to ERS utility included: a lack of designated, ongoing resource for system maintenance, technical support and development; uncertainty about how and when to use ERS and workload. Incomplete data prevented gaining a better understanding of important risk factors and transmission routes of CPGNB in England.

CONCLUSION

The ERS is the only surveillance system in England with the potential to gather intelligence on important risk factors for CPGNB to inform public health measures to control their spread. Although the ERS captures more information on CPGNB than other surveillance systems, timeliness and completeness of the enhanced data require substantial improvements in order to deliver the desired health benefits.

Survey of screening methods, rates and policies for the detection of carbapenemase-producing Enterobacteriaceae in English hospitals

Multi-drug-resistant Gram-negative bacteria are of major clinical concern. The increasing prevalence of carbapenemase-producing Enterobacteriaceae (CPE), resistant to all beta-lactams including carbapenems and able to colonize the large intestine, represents a key threat. Rapid, accurate detection of intestinal CPE colonization is critical to minimize transmission, and hence reduce costly, difficult-to-treat CPE infections. There is currently no 'gold standard' CPE detection method. A survey of diagnostic laboratories in England found considerable heterogeneity in diagnostic CPE testing methods and procedures.

First outbreak of colonization by linezolid- and glycopeptide-resistant Enterococcus faecium harbouring the cfr gene in a UK nephrology unit

AIM

To describe an outbreak of colonization by linezolid- and glycopeptide-resistant Enterococcus faecium harbouring the cfr gene in a UK nephrology unit.

METHODS

Isolates of linezolid-resistant E. faecium were typed by pulsed-field gel electrophoresis (PFGE), and examined by polymerase chain reaction (PCR) and sequencing for the transmissible cfr gene that confers resistance to linezolid. Enhanced environmental cleaning, initial and weekly screening of all patients, and monitoring of adherence to standard infection control precautions were implemented.

FINDINGS

Five patients with pre-existing renal disease were found to have rectal colonization with linezolid-resistant E. faecium over a two-week period. The index case was a 57-year-old male from India who had travelled to the UK. One patient also had a linezolid-resistant E. faecium of a different PFGE profile isolated from a heel wound. All isolates were confirmed to harbour the cfr gene by PCR and Sanger sequencing, and all were resistant to glycopeptides (VanA phenotype).

CONCLUSIONS

This article describes the first UK outbreak with a single strain of linezolid- and glycopeptide-resistant E. faecium harbouring the cfr gene, affecting five patients in a nephrology unit. Following the implementation of aggressive infection control measures, no further cases were detected beyond a two-week period.

Carriage of extended-spectrum beta-lactamase-producing Enterobacteriaceae in HIV-infected children in Zimbabwe

Background

Antimicrobial resistance is an emerging global health issue. Data on the epidemiology of multidrug-resistant organisms are scarce for Africa, especially in HIV-infected individuals who often have frequent contact with healthcare. We investigated the prevalence of extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) carriage in stool among HIV-infected children attending an HIV outpatient department in Harare, Zimbabwe.

Methods

We recruited children who were stable on antiretroviral therapy (ART) attending a HIV clinic from August 2014 to June 2015. Information was collected on antibiotic use and hospitalization. Stool was tested for ESBL-E through combination disc diffusion. API20E identification and antimicrobial susceptibility was performed on the positive samples followed by whole genome sequencing.

Results

Stool was collected from 175/202 (86.6 %) children. Median age was 11 [inter-quartile range (IQR) 9–12] years. Median time on ART was 4.6 years (IQR 2.4–6.4). ESBL-Es were found in 24/175 samples (13.7 %); 50 % of all ESBL-Es were resistant to amoxicillin-clavulanate, 100 % to co-trimoxazole, 45.8 % to chloramphenicol, 91.6 % to ceftriaxone, 20.8 % to gentamicin and 62.5 % to ciprofloxacin. ESBL-Es variously encoded CTX-M, OXA, TEM and SHV enzymes. The odds of ESBL-E carriage were 8.5 times (95 % CI 2.2–32.3) higher in those on ART for less than one year (versus longer) and 8.5 times (95 % CI 1.1–32.3) higher in those recently hospitalized for a chest infection.

Conclusion

We found a 13.7 % prevalence of ESBL-E carriage in a population where ESBL-E carriage has not been described previously. Antimicrobial resistance (AMR) in Africa merits further study, particularly given the high HIV prevalence and limited diagnostic and therapeutic options available.

The role of whole genome sequencing in antimicrobial susceptibility testing of bacteria: report from the EUCAST Subcommittee

Whole genome sequencing (WGS) offers the potential to predict antimicrobial susceptibility from a single assay. The European Committee on Antimicrobial Susceptibility Testing established a subcommittee to review the current development status of WGS for bacterial antimicrobial susceptibility testing (AST). The published evidence for using WGS as a tool to infer antimicrobial susceptibility accurately is currently either poor or non-existent and the evidence / knowledge base requires significant expansion. The primary comparators for assessing genotypic-phenotypic concordance from WGS data should be changed to epidemiological cut-off values in order to improve differentiation of wild-type from non-wild-type isolates (harbouring an acquired resistance). Clinical breakpoints should be a secondary comparator. This assessment will reveal whether genetic predictions could also be used to guide clinical decision making. Internationally agreed principles and quality control (QC) metrics will facilitate early harmonization of analytical approaches and interpretive criteria for WGS-based predictive AST. Only data sets that pass agreed QC metrics should be used in AST predictions. Minimum performance standards should exist and comparative accuracies across different WGS laboratories and processes should be measured. To facilitate comparisons, a single public database of all known resistance loci should be established, regularly updated and strictly curated using minimum standards for the inclusion of resistance loci. For most bacterial species the major limitations to widespread adoption for WGS-based AST in clinical laboratories remain the current high-cost and limited speed of inferring antimicrobial susceptibility from WGS data as well as the dependency on previous culture because analysis directly on specimens remains challenging. For most bacterial species there is currently insufficient evidence to support the use of WGS-inferred AST to guide clinical decision making. WGS-AST should be a funding priority if it is to become a rival to phenotypic AST. This report will be updated as the available evidence increases.

Identification of bacterial pathogens and antimicrobial resistance directly from clinical urines by nanopore-based metagenomic sequencing

OBJECTIVES

The introduction of metagenomic sequencing to diagnostic microbiology has been hampered by slowness, cost and complexity. We explored whether MinION nanopore sequencing could accelerate diagnosis and resistance profiling, using complicated urinary tract infections as an exemplar.

METHODS

Bacterial DNA was enriched from clinical urines (n = 10) and from healthy urines 'spiked' with multiresistant Escherichia coli (n = 5), then sequenced by MinION. Sequences were analysed using external databases and bioinformatic pipelines or, ultimately, using integrated real-time analysis applications. Results were compared with Illumina data and resistance phenotypes.

RESULTS

MinION correctly identified pathogens without culture and, among 55 acquired resistance genes detected in the cultivated bacteria by Illumina sequencing, 51 were found by MinION sequencing directly from the urines; with three of the four failures in an early run with low genome coverage. Resistance-conferring mutations and allelic variants were not reliably identified.

CONCLUSIONS

MinION sequencing comprehensively identified pathogens and acquired resistance genes from urine in a timeframe similar to PCR (4 h from sample to result). Bioinformatic pipeline optimization is needed to better detect resistances conferred by point mutations. Metagenomic-sequencing-based diagnosis will enable clinicians to adjust antimicrobial therapy before the second dose of a typical (i.e. every 8 h) antibiotic.

Population structure of Escherichia coli causing bacteraemia in the UK and Ireland between 2001 and 2010

OBJECTIVES

Escherichia coli is the most common agent of bacteraemia, bacterial gastroenteritis and urinary tract infections (UTIs). Lineages causing UTIs and gastrointestinal disease are well defined, but less is known about those causing bacteraemia. We therefore investigated the population structure of E. coli from bacteraemia in the UK and Ireland between 2001 and 2010.

METHODS

E. coli isolates (n = 2166) were submitted to the BSAC Bacteraemia Surveillance Programme from 18 UK and Irish centres from 2001 to 2010. Genotypes were analysed by MLST using the Achtman scheme; MICs, blaCTX-M group and patient demographics were previously determined in the BSAC surveillance.

RESULTS

Four hundred and forty-eight STs were identified, but five of these, and their associated clonal complexes (CCs), accounted for 58.4% (1264 of 2166) of isolates: CC73 was the most common (20.7%), followed by CC131 (13.9%), CC95 (11.3%), CC69 (6.9%) and CC12 (5.5%). All these, except CC69 (group D), belong to phylogenetic group B2. CC131 isolates were much more often MDR than other STs were: they rose from 2.9% of isolates in 2001 to 20.5%-20.7% in 2007-08 and then declined to 14.3% in 2010. Resistance rates to cephalosporins, aminoglycosides and fluoroquinolones remained below 10% in other major CCs throughout.

CONCLUSIONS

The five most prevalent bacteraemia STs have all been associated previously with UTIs. They dominated in all years, but their proportions fluctuated, most notably for ST131, a globally disseminated high-risk clone that is often MDR.

Comparison of the Victorian Audit of Surgical Mortality with coronial cause of death

BACKGROUND

The Victorian Audit of Surgical Mortality (VASM) is designed to improve the level of patient care by educating surgeons of areas for improvement in patient management during a surgical admission. Coronial data obtained via the National Coronial Information System were used as an independent method to validate the cause of death as determined by the treating surgeon.

METHOD

The audit prospectively collected 4905 cases that underwent peer assessment and 842 (17%) received an in-depth second-line assessment of which 200 (24%) also underwent a coronial review. Using the coronial assessment as the reference standard, retrospective comparison of coronial diagnoses compared with the audit case outcomes was conducted to determine the overall accuracy of the stated cause of death. The degree of agreement was also analysed based on whether the patient received a full autopsy (internal examination) or an external examination only. The time taken to obtain the coronial and audit case closure was also analysed.

RESULTS

Overall, 195 of the 200 cases had a cause of death identified by the coroner. In 82%, the cause of death reported to VASM by the treating surgeon matched the cause of death determined by the coroner. Concordance was not affected by the extent of post-mortem performed. Time taken to finalize cases was slightly shorter for the coronial process, but unclosed coronial findings resulted in the exclusion of 103 cases.

CONCLUSION

The causes of death data in VASM are accurate when compared with the coronial data independent of whether the coronial investigation included a complete autopsy.

The development of a protocol for post-mortem management of Ebola virus disease in the setting of developed countries

The management of the recent Ebola virus disease (EVD) epidemic continues to pose currently insuperable challenges to health care providers in the resource-deprived countries of West Africa. In an age where air travel facilitates rapid movement of people between countries and continents, there is an urgent requirement for health systems around the globe to develop management strategies and protocols in the event that EVD cases are suspected or confirmed. Departments of forensic pathology play an important, and underestimated, role in public health service delivery, particularly at times of novel infectious disease emergence. This role can include disease identification, characterization, and notification, as well as close engagement with agencies responsible for disease surveillance and treatment provision. A mass outbreak of EVD in the Western world is considered highly unlikely; however, there is clear responsibility on departments of forensic pathology to develop protocols for rapid assessment of sporadic or suspected cases while ensuring the health and safety of mortuary and pathology personnel. The Ontario Forensic Pathology Service and the Victorian Institute of Forensic Medicine have collaborated on the development of a protocol for management of EVD cases presenting at a scene or in the mortuary. It is hoped that this trans-national, inter-departmental exercise will serve as a model for future co-operative endeavors. The protocol has been distributed to forensic pathology departments around Australia and may be modified to accommodate local resource capabilities.

Activity of colistin in combination with tigecycline or rifampicin against multidrug-resistant Stenotrophomonas maltophilia

The antimicrobial treatment of Stenotrophomonas maltophilia infections is complicated by intrinsic multidrug resistance and a lack of reliable susceptibility data. We assessed the activity of colistin (COL), rifampicin (RIF) and tigecycline (TGC) alone and in combination using a range of in vitro susceptibility testing methodologies and a simple invertebrate model of S. maltophilia infection (Galleria mellonella). Synergy [fractional inhibitory concentration indices (FICIs) ≤0.5] between COL and either RIF or TGC was observed against 92 % and 88 % of 25 S. maltophilia isolates, respectively, despite resistance to one or another of the single agents alone. In time-kill assays, COL combined with either RIF or TGC was superior to single agents, but only the COL/RIF regimen was reliably bactericidal. The in vitro findings correlated with treatment outcomes in G. mellonella, with heightened survival observed for larvae treated with COL/RIF or COL/TGC compared with COL, RIF or TGC alone. COL combined with RIF was the most effective combination overall in both in vitro and in vivo (p < 0.05) assays. Given the difficulty in selecting appropriate therapy for S. maltophilia infections, regimens consisting of COL combined with RIF or TGC could be considered for clinical use.

Development and evaluation of a multiplex PCR for eight plasmid-mediated quinolone-resistance determinants

The objective of this study was to develop and validate an expanded multiplex PCR assay for the simultaneous detection of eight plasmid-mediated quinolone-resistance determinants in Enterobacteriaceae. Primers were designed to amplify conserved fragments of qnrABCDS, qepA, oqxAB and aac(6′)-Ib-cr genes and were optimized in uniplex and multiplex PCR assays with control template DNA. The assay was used to determine the prevalence of plasmid-mediated quinolone resistance (PMQR) genes in 174 ciprofloxacin-resistant and 43 ciprofloxacin-susceptible extraintestinal pathogenic Escherichia coli isolates. Each resistance gene could be detected alone and in combination. PMQR determinants were detected in 65 ciprofloxacin-resistant isolates (37 %) and one ciprofloxacin-susceptible isolate (2 %). Prevalences of the identified determinants were: aac(6′)-Ib-cr, 34.5 %; qnrS, 1.1 %; qepA, 1.1 %; and oqxAB, 0.6 %. In conclusion, we developed an eight-target multiplex PCR for the accurate detection of PMQR genes and confirmed that PMQR prevalence remains low among human Escherichia coli clinical isolates in the UK.

First report of IMI-1-producing colistin-resistant Enterobacter clinical isolate in Ireland, March 2013

We report the first case in Ireland of an IMI-1 carbapenemase-producing Enterobacter asburiae, which was resistant to both colistin and fosfomycin. The circumstances under which this isolate was acquired were unclear. Several reports of IMI-producing Enterobacter spp. have emerged in recent years, and colistin resistance in Enterobacteriaceae is also increasingly reported. Laboratories should be aware of the unusual antibiograms of IMI-producing isolates.

Carbapenemase-producing Enterobacteriaceae in Europe: a survey among national experts from 39 countries, February 2013

The spread of carbapenemase-producing Enterobacteriaceae (CPE) is a threat to healthcare delivery, although its extent differs substantially from country to country. In February 2013, national experts from 39 European countries were invited to self-assess the current epidemiological situation of CPE in their country. Information about national management of CPE was also reported. The results highlight the urgent need for a coordinated European effort on early diagnosis, active surveillance, and guidance on infection control measures.

Rapid evolution and spread of carbapenemases among Enterobacteriaceae in Europe

Plasmid-acquired carbapenemases in Enterobacteriaceae, which were first discovered in Europe in the 1990s, are now increasingly being identified at an alarming rate. Although their hydrolysis spectrum may vary, they hydrolyse most β-lactams, including carbapenems. They are mostly of the KPC, VIM, NDM and OXA-48 types. Their prevalence in Europe as reported in 2011 varies significantly from high (Greece and Italy) to low (Nordic countries). The types of carbapenemase vary among countries, partially depending on the cultural/population exchange relationship between the European countries and the possible reservoirs of each carbapenemase. Carbapenemase producers are mainly identified among Klebsiella pneumoniae and Escherichia coli, and still mostly in hospital settings and rarely in the community. Although important nosocomial outbreaks with carbapenemase-producing Enterobacteriaceae have been extensively reported, many new cases are still related to importation from a foreign country. Rapid identification of colonized or infected patients and screening of carriers is possible, and will probably be effective for prevention of a scenario of endemicity, as now reported for extended-spectrum β-lactamase (mainly CTX-M) producers in all European countries.