Capsular type K54, clonal group 29 and virulence plasmids: an analysis of K54 and non-K54 closely related isolates of Klebsiella pneumoniae.

Capsular type K54 of Klebsiella pneumoniae is associated with hypervirulence and we sought to discover the basis for this among isolates submitted to the UK reference laboratory between 2012 and 2017. Isolates were typed by variable number tandem repeat analysis, and capsular type and virulence elements sought by PCR. The most prevalent type found (15/31 isolates) corresponded to clonal group (CG) 29 and included five representatives carrying rmpA, rmpA2 (regulators of mucoid phenotype), iutA and iroD (from the aerobactin and salmochelin siderophore clusters) associated with virulence plasmids. These included isolate KpvK54, recovered from pus. The remaining isolates did not carry a virulence plasmid. We also noted 11 further related isolates, including NCTC 9159, not of capsular type K54, but nevertheless sometimes associated with sepsis and abscesses. Whole-genome sequencing showed that KpvK54 carried a large virulence plasmid and an ICEKp3-like structure carrying the yersiniabactin cluster, absent in NCTC 9159. Comparative chromosomal analysis with an additional four genomes showed that KpvK54 shared further genes with K1-ST23 hypervirulent isolates, and with LS358, a K54-ST29 isolate from liver abscess puncture fluid. While CG29 isolates displayed varying degrees of virulence, some, especially those with the virulence plasmid (all K54), were clearly associated with hypervirulence.

An outbreak of multidrug-resistant Pseudomonas aeruginosa in a burns service in the North of England: challenges of infection prevention and control in a complex setting.

BACKGROUND: Burns patients are at high risk of nosocomial infection, and Pseudomonas aeruginosa is one of the most common causes of wound and systemic infections resulting in significant morbidity and mortality in burns patients. AIM: To describe an outbreak of multidrug-resistant P. aeruginosa (MDR-Pa) at a specialist burns service and highlight the challenges in identifying the reservoir of infection despite extensive epidemiological, microbiological, and environmental investigations. METHODS: Multi-disciplinary outbreak control investigation. FINDINGS: Following an inter-hospital transfer of a burns patient from another country, an admission screen revealed that the patient was colonized with MDR-Pa. Subsequently nine more patients contracted MDR-Pa in the period from November 2015 to September 2017. Given the relatively long gap between confirmation of the index and subsequent cases, it was not possible to identify with certainty the reservoirs and mechanisms of spread of infection, although contamination of the burns service environment and equipment are likely to be contributory factors. CONCLUSION: Preventing infection transmission in specialist burns services is highly challenging, and it may not always be possible to identify and eradicate the reservoirs of infection for P. aeruginosa outbreaks. Our study supports the literature, providing additional evidence that inanimate, common contact surfaces play an important role in nosocomial transmission of P. aeruginosa. These surfaces should either be decontaminated efficiently between patient contacts or be single patient use. Enhanced vigilance is crucial, and, with strict adherence to infection prevention and control procedures, it is possible to reduce the risk of acquisition and spread of infection in patients.

Does screening neonates in the neonatal intensive care unit for Pseudomonas aeruginosa colonization help prevent infection?

BACKGROUND: Pseudomonas aeruginosa (PA) is a Gram-negative environmental organism that can cause severe infection in immunosuppressed patients, including preterm neonates. In recent years, it has become common practice to screen neonates for PA colonization. AIM: To assess the value of screening neonates for PA in (1) predicting the risk of developing severe PA infection and (2) directing infection control practice. METHODS: Between August 2012 and September 2015, babies admitted to the neonatal intensive care unit (NICU) at North Bristol NHS Trust were screened routinely for PA colonization on admission and weekly thereafter. Data were also collected on babies who developed PA infection. Environmental samples from the NICU were tested for the presence of PA. Variable number tandem repeat (VNTR) typing was performed on all strains of PA from babies and the environment. FINDINGS: No babies with positive screens subsequently developed PA infection. There was no VNTR strain evidence supporting cross-infection from the environment or other babies. CONCLUSION: Screening neonates for PA did not identify babies who subsequently developed PA infection. Following cessation of screening in September 2015, there was no increase in the number of babies identified with PA infection.

Pseudomonas aeruginosa intensive care unit outbreak: winnowing of transmissions with molecular and genomic typing.

BACKGROUND: Pseudomonas aeruginosa healthcare outbreaks can be time consuming and difficult to investigate. Guidance does not specify which typing technique is most practical for decision-making. AIM: To explore the usefulness of whole-genome sequencing (WGS) in the investigation of a P. aeruginosa outbreak, describing how it compares with pulsed-field gel electrophoresis (PFGE) and variable number tandem repeat (VNTR) analysis. METHODS: Six patient isolates and six environmental samples from an intensive care unit (ICU) positive for P. aeruginosa over two years underwent VNTR, PFGE and WGS. FINDINGS: VNTR and PFGE were required to fully determine the potential source of infection and rule out others. WGS results unambiguously distinguished linked isolates, giving greater assurance of the transmission route between wash-hand basin water and two patients, supporting the control measures employed. CONCLUSION: WGS provided detailed information without the need for further typing. When allied to epidemiological information, WGS can be used to understand outbreak situations rapidly and with certainty. Implementation of WGS in real-time would be a major advance in day-to-day practice. It could become a standard of care as it becomes more widespread due to its reproducibility and lower costs.

Whole-exome sequencing of the BDR cohort: evidence to support the role of the PILRA gene in Alzheimer's disease.

AIM: Late-onset Alzheimer's disease (LOAD) accounts for 95% of all Alzheimer's cases and is genetically complex in nature. Overlapping clinical and neuropathological features between AD, FTD and Parkinson's disease highlight the potential role of genetic pleiotropy across diseases. Recent genome-wide association studies (GWASs) have uncovered 20 new loci for AD risk; however, these exhibit small effect sizes. Using NGS, here we perform association analyses using exome-wide and candidate-gene-driven approaches. METHODS: Whole-exome sequencing was performed on 132 AD cases and 53 control samples. Exome-wide single-variant association and gene burden tests were performed for 76 640 nonsingleton variants. Samples were also screened for known causative mutations in familial genes in AD and other dementias. Single-variant association and burden analysis was also carried out on variants in known AD and other neurological dementia genes. RESULTS: Tentative single-variant and burden associations were seen in several genes with kinase and protease activity. Exome-wide burden analysis also revealed significant burden of variants in PILRA (P = 3.4 × 10-5 ), which has previously been linked to AD via GWAS, hit ZCWPW1. Screening for causative mutations in familial AD and other dementia genes revealed no pathogenic variants. Variants identified in ABCA7, SLC24A4, CD33 and LRRK2 were nominally associated with disease (P < 0.05) but did not withstand correction for multiple testing. APOE (P = 0.02) and CLU (P = 0.04) variants showed significant burden on AD. CONCLUSIONS: In addition, polygenic risk scores (PRS) were able to distinguish between cases and controls with 83.8% accuracy using 3268 variants, sex, age at death and APOE ε4 and ε2 status as predictors.

Ralstonia infection in cystic fibrosis.

This study aimed to determine prevalence of Ralstonia spp. in cystic fibrosis patients, look for any evidence of cross infection and to describe clinical outcomes for patients infected by Ralstonia spp. Prevalence of Ralstonia spp. was calculated annually from 2008 to 2016. Pulsed-field gel electrophoresis was performed on ⩾1 sample from patients with an isolation of Ralstonia spp. between 2008 and 2016. A prospective, longitudinal observational study of adult patients was performed with 12 months follow-up from recruitment. Prevalence of Ralstonia spp. rose from 0·6% in 2008 to 2·4% in 2016. In total 12 out of 14 (86%) patients with ⩾1 isolation of Ralstonia spp. developed chronic infection. A pair and a group of three unrelated patients with epidemiological connections shared strains of Ralstonia mannitolilytica. Lung function of Ralstonia spp. infected patients was moderately to severely impaired. Prevalence of Ralstonia spp. is low but increasing. The risk of a patient developing chronic Ralstonia spp. infection following first acquisition is high and cross-infection may be possible. Whether Ralstonia spp. infection causes increased pulmonary exacerbation frequency and lung function decline needs to be evaluated in larger prospective studies.

Novel Lethal Form of Congenital Hypopituitarism Associated With the First Recessive LHX4 Mutation.

BACKGROUND: LHX4 encodes a member of the LIM-homeodomain family of transcription factors that is required for normal development of the pituitary gland. To date, only incompletely penetrant heterozygous mutations in LHX4 have been described in patients with variable combined pituitary hormone deficiencies. OBJECTIVE/HYPOTHESIS: To report a unique family with a novel recessive variant in LHX4 associated with a lethal form of congenital hypopituitarism that was identified through screening a total of 97 patients. METHOD: We screened 97 unrelated patients with combined pituitary hormone deficiency, including 65% with an ectopic posterior pituitary, for variants in the LHX4 gene using Sanger sequencing. Control databases (1000 Genomes, dbSNP, Exome Variant Server, ExAC Browser) were consulted upon identification of variants. RESULTS: We identified the first novel homozygous missense variant (c.377C>T, p.T126M) in two deceased male patients of Pakistani origin with severe panhypopituitarism associated with anterior pituitary aplasia and posterior pituitary ectopia. Both were born small for gestational age with a small phallus, undescended testes, and mid-facial hypoplasia. The parents' first-born child was a female with mid-facial hypoplasia (DNA was unavailable). Despite rapid commencement of hydrocortisone and T4 in the brothers, all three children died within the first week of life. The LHX4(p.T126M) variant is located within the LIM2 domain, in a highly conserved location. The absence of homozygosity for the variant in over 65 000 controls suggests that it is likely to be responsible for the phenotype. CONCLUSION: We report, for the first time to our knowledge, a novel homozygous mutation in LHX4 associated with a lethal phenotype, implying that recessive mutations in LHX4 may be incompatible with life.

What may be lurking in the hospital undergrowth? Inapparent cross-transmission of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae.

BACKGROUND: Extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae pose an increasing challenge in hospitals. AIM: To describe the benefits of using molecular techniques to investigate the spread of ESBL-producing Klebsiella pneumoniae (ESBL-KP) within a tertiary referral centre. METHODS: Following the identification of a cluster of five ESBL-KP on one ward, a hospital-wide retrospective epidemiological investigation was undertaken into the incidence and spread of these organisms. Variable number tandem repeat (VNTR) profiles were used to assign patients to possible clusters. Patient outcome and length of hospital stay were reviewed. Locations of patients assigned to each cluster were investigated as possible sources of spread. Antimicrobial prescribing practices and hand hygiene compliance on affected wards were also reviewed. FINDINGS: Twenty-four ESBL-KP isolates were characterized by VNTR. The mean length of stay was 102.5 days for patients with ESBL-KP, which was significantly longer compared with the mean length of stay for all patients (10.1 days, P < 0.01). Nineteen patients were assigned to clusters with shared VNTR profiles. Review of patient transfer histories identified two instances where cross-transmission may have occurred. In both cases, compliance with good hand hygiene practice and antimicrobial prescribing was suboptimal. CONCLUSION: Molecular typing provided a valuable insight into the clones of ESBL-KP circulating within the study institution. Increased surveillance to identify colonization among patients and routine typing of isolates should be considered, but the resource implications for patient isolation are considerable.

Investigation of healthcare-acquired infections associated with Pseudomonas aeruginosa biofilms in taps in neonatal units in Northern Ireland.

BACKGROUND: In December 2011 and early 2012 four neonates died from Pseudomonas aeruginosa bacteraemia in hospitals in Northern Ireland. AIM: To assess whether P. aeruginosa was associated with the neonatal unit taps and whether waterborne isolates were consistent with patient isolates. METHODS: Thirty taps and eight flow straighteners from the relevant hospitals were categorized and dismantled into 494 components and assessed for aerobic colony and P. aeruginosa counts using non-selective and selective agars. P. aeruginosa isolates were typed by variable number tandem repeat (VNTR) analysis. Selected tap components were subjected to epifluorescence and scanning electron microscopy to visualize biofilm. FINDINGS: The highest P. aeruginosa counts were from the flow straighteners, metal support collars and the tap bodies surrounding these two components. Complex flow straighteners had a significantly higher P. aeruginosa count than other types of flow straighteners (P < 0.05). Highest aerobic colony counts were associated with integrated mixers and solenoids (P < 0.05), but there was not a strong correlation (r = 0.33) between the aerobic colony counts and P. aeruginosa counts. Representative P. aeruginosa tap isolates from two hospital neonatal units had VNTR profiles consistent with strains from the tap water and infected neonates. CONCLUSION: P. aeruginosa was predominantly found in biofilms in flow straighteners and associated components in the tap outlets and was a possible source of the infections observed. Healthcare providers should be aware that water outlets can be a source of P. aeruginosa contamination and should take steps to reduce such contamination, monitor it and have strategies to minimize risk to susceptible patients.

Outbreak of Stenotrophomonas maltophilia on an intensive care unit.

BACKGROUND: Stenotrophomonas maltophilia causes opportunistic infections and remains a problem pathogen on intensive care unit (ICU) due to its multidrug resistance. AIM: An outbreak of S. maltophilia on ICU is described in order to highlight the risk from contaminated devices for supply of drinking water. METHODS: The outbreak was investigated by a combination of epidemiology, environmental sampling and molecular typing. FINDINGS: From 2009 to 2011 isolates of S. maltophilia from 23 patients were found to belong to only two genotypes by contrast with isolates from 52 other patients during this period, which represented distinct strains. The monthly incidence for all S. maltophilia strains ranged from 0 to 11% and for the two outbreak strains from 0 to 9%. Admission and weekly pharyngeal screening on ICU showed that the outbreak strains were acquired on ICU (range: 3-90 days). The majority of isolates (74%) were from the respiratory tract. Only two of 12 (17%) colonized intubated patients developed pneumonia. Environmental sampling found the two outbreak strains in two sinks and in the drinking water of the cooling unit in the ICU kitchen. S. maltophilia had formed a biofilm in the flexible tube from the carbon filter to the chiller and from the latter to the tap at the kitchen sink. This cooled water was used for providing drinking water and mouth care to ICU patients. The outbreak strains disappeared after removal of the water-cooler and the monthly incidence fell to <2% of ICU admissions. CONCLUSION: This outbreak report highlights the risk from biofilms in devices that supply drinking water for ICU patients.

Emergence of carbapenem-resistant Enterobacteriaceae in a UK paediatric hospital.

BACKGROUND: Carbapenem-resistant Enterobacteriaceae are an emerging global infection threat. However, there are few data describing their clinical importance in children. AIM: This retrospective study reviewed the prevalence and resistance mechanisms of carbapenem-resistant Enterobacteriaceae grown from clinical and surveillance samples in a large tertiary referral children's hospital in the UK. METHODS: Carbapenem-resistant Enterobacteriaceae were sought in specimens submitted for diagnostic and surveillance purposes at Alder Hey Children's NHS Foundation Trust, Liverpool, between September 2011 and August 2012. Mechanisms of resistance were identified using phenotypic and/or molecular methods. Variable number tandem repeat profiling was used to type carbapenemase-producing strains. FINDINGS: During the 12-month study period, carbapenem-resistant Enterobacteriaceae were recovered from 24 patients. Five isolates were from clinical diagnostic specimens whereas 19 of 421 patients had positive rectal surveillance swabs (4.5%). Of the 24 isolates, seven (all Klebsiella spp.) harboured carbapenemases: three had blaKPC and four blaNDM, whereas 17 had resistance due to combinations of AmpC or extended-spectrum ß-lactamase activity plus impermeability. CONCLUSION: Carbapenem-resistant Enterobacteriaceae and, in particular, those with carbapenemases, are an emerging infection problem in a major paediatric hospital in the UK. Active surveillance is required to monitor and control their spread.

Two novel mutations in the POU1F1 gene generate null alleles through different mechanisms leading to combined pituitary hormone deficiency.

BACKGROUND: Mutations in the POU1F1 gene severely affect the development and function of the anterior pituitary gland and lead to combined pituitary hormone deficiency (CPHD). OBJECTIVE: The clinical and genetic analysis of a patient presenting with CPHD and functional characterization of identified mutations. PATIENT: We describe a male patient with extreme short stature, learning difficulties, anterior pituitary hypoplasia, secondary hypothyroidism and undetectable prolactin, growth hormone (GH) and insulin-like growth factor 1 (IGF1), with normal random cortisol. DESIGN: The POU1F1 coding region was amplified by PCR and sequenced; the functional consequence of the mutations was analysed by cell transfection and in vitro assays. RESULTS: Genetic analysis revealed compound heterozygosity for two novel putative loss of function mutations in POU1F1: a transition at position +3 of intron 1 [IVS1+3nt(A>G)] and a point mutation in exon 6 resulting in a substitution of arginine by tryptophan (R265W). Functional analysis revealed that IVS1+3nt(A>G) results in a reduction in the correctly spliced POU1F1 mRNA, which could be corrected by mutations of the +4, +5 and +6 nucleotides. Analysis of POU1F1(R265W) revealed complete loss of function resulting from severely reduced protein stability. CONCLUSIONS: Combined pituitary hormone deficiency in this patient is caused by loss of POU1F1 function by two novel mechanisms, namely aberrant splicing (IVS1+3nt (A>G) and protein instability (R265W). Identification of the genetic basis of CPHD enabled the cessation of hydrocortisone therapy without the need for further assessment for evolving endocrinopathy.

'Sink or swim': an evaluation of the clinical characteristics of individuals with high bone mass.

SUMMARY: High bone mineral density on routine dual energy X-ray absorptiometry (DXA) may indicate an underlying skeletal dysplasia. Two hundred fifty-eight individuals with unexplained high bone mass (HBM), 236 relatives (41% with HBM) and 58 spouses were studied. Cases could not float, had mandible enlargement, extra bone, broad frames, larger shoe sizes and increased body mass index (BMI). HBM cases may harbour an underlying genetic disorder. INTRODUCTION: High bone mineral density is a sporadic incidental finding on routine DXA scanning of apparently asymptomatic individuals. Such individuals may have an underlying skeletal dysplasia, as seen in LRP5 mutations. We aimed to characterize unexplained HBM and determine the potential for an underlying skeletal dysplasia. METHODS: Two hundred fifty-eight individuals with unexplained HBM (defined as L1 Z-score ≥ +3.2 plus total hip Z-score ≥ +1.2, or total hip Z-score ≥ +3.2) were recruited from 15 UK centres, by screening 335,115 DXA scans. Unexplained HBM affected 0.181% of DXA scans. Next 236 relatives were recruited of whom 94 (41%) had HBM (defined as L1 Z-score + total hip Z-score ≥ +3.2). Fifty-eight spouses were also recruited together with the unaffected relatives as controls. Phenotypes of cases and controls, obtained from clinical assessment, were compared using random-effects linear and logistic regression models, clustered by family, adjusted for confounders, including age and sex. RESULTS: Individuals with unexplained HBM had an excess of sinking when swimming (7.11 [3.65, 13.84], p < 0.001; adjusted odds ratio with 95% confidence interval shown), mandible enlargement (4.16 [2.34, 7.39], p < 0.001), extra bone at tendon/ligament insertions (2.07 [1.13, 3.78], p = 0.018) and broad frame (3.55 [2.12, 5.95], p < 0.001). HBM cases also had a larger shoe size (mean difference 0.4 [0.1, 0.7] UK sizes, p = 0.009) and increased BMI (mean difference 2.2 [1.3, 3.1] kg/m(2), p < 0.001). CONCLUSION: Individuals with unexplained HBM have an excess of clinical characteristics associated with skeletal dysplasia and their relatives are commonly affected, suggesting many may harbour an underlying genetic disorder affecting bone mass.

Impact of a clonal outbreak of extended-spectrum ß-lactamase-producing Klebsiella pneumoniae in the development and evolution of bloodstream infections by K. pneumoniae and Escherichia coli: an 11 year experience in Oxfordshire, UK.

OBJECTIVES: The objectives of this study were: (i) to describe an outbreak of multidrug-resistant Klebsiella pneumoniae in our population; (ii) to identify the potential source of this outbreak by examining antibiotic resistance trends in urocultures; (iii) to evaluate the contribution of this outbreak to resistance patterns over time in the two commonest Gram-negative blood culture isolates, namely K. pneumoniae and Escherichia coli; and (iv) to assess risk factors for multidrug resistance and the impact of this resistance on mortality and length of stay. METHODS: We searched Microbiology and Patient Administration Service databases retrospectively and describe resistance trends in E. coli and K. pneumoniae bloodstream infections (BSIs) in Oxfordshire, UK, over an 11 year period. RESULTS: An outbreak of a multidrug-resistant, CTX-M-15 extended-spectrum ß-lactamase (ESBL)-producing K. pneumoniae clone was identified and shown by multilocus sequence typing to belong to a novel sequence type designated ST490. This was associated with a sporadic change in resistance rates in K. pneumoniae BSIs with rates of multidrug resistance (defined as resistance to three or more antibiotic classes) reaching 40%. A case-control study showed prior antibiotic exposure as a risk factor for infection with this organism. During the same time period, rates of ESBL-producing Klebsiella spp. isolated from urocultures increased from 0.5% to almost 6%. By contrast, the rate of multidrug resistance in E. coli rose more steadily from 0% in 2000 to 10% in 2010. CONCLUSIONS: Changes in resistance rates may be associated with outbreaks of resistant clones in K. pneumoniae. Changing resistance patterns may affect important health economic issues such as length of stay.

Molecular and epidemiological characterisation of clinical isolates of carbapenem-resistant Acinetobacter baumannii from public and private sector intensive care units in Karachi, Pakistan.

The purpose of this study was to identify molecular and epidemiological characteristics of hospital-acquired carbapenem-resistant Acinetobacter baumannii (CRAB) from two different intensive care unit (ICU) settings in Karachi, Pakistan. A cross-sectional study was performed in the adult ICUs of a private sector tertiary care hospital (PS-ICU) and of a government sector hospital (GS-ICU) between November 2007 and August 2008. Deduplicated CRAB isolates from clinical specimens were examined for carbapenemase and class 1 integrase genes. Isolates were typed using sequence-based multiplex polymerase chain reaction, pulsed-field gel electrophoresis (PFGE) and variable number tandem repeat (VNTR). A total of 50 patients (33 from PS-ICU and 17 from GS-ICU) were recruited. There were statistically significant differences between patients in the two ICUs in terms of mean age, comorbidities, the presence of central venous pressure lines, urinary catheters, and average length of stay. bla(OxA-23-like) acquired-oxacillinase genes were found in 47/50 isolates. Class 1 integrase genes were found in 50% (25/50) of the organisms. The majority of isolates belonged to strains of European clones I and II. PFGE typing grouped the isolates into eight distinct clusters, three of which were found in both hospitals. Most of the isolates within each PFGE cluster shared identical or highly similar VNTR profiles, suggesting close epidemiological association. Irrespective of differences in risk factors and infection control policies and practices, the extent of clonality among CRAB isolates was very similar in both ICU settings.

Evaluation of a nine-locus variable-number tandem-repeat scheme for typing of Pseudomonas aeruginosa.

Repeat numbers at nine variable-number tandem-repeat (VNTR) loci were determined for 177 isolates of Pseudomonas aeruginosa representing 77 strains distinguished by pulsed-field gel electrophoresis (PFGE). Eight loci provided for discrimination similar to that provided by PFGE, with variation at the ninth locus (ms61) sometimes allowing discrimination within a PFGE-defined type. The Liverpool and Midlands 1 strains, which are common among patients with cystic fibrosis in the UK, could be unambiguously identified by their characteristic VNTR profiles. In rare cases, the repeat number at the ninth locus alone provided discrimination among isolates that were distinct according to PFGE. In each case, the two isolates shared the same bla(OXA-50-like) allele and belonged to the same oprD sequence type group, supporting the VNTR results in suggesting that they are similar.

First identification of blaOXA-51-like in non-baumannii Acinetobacter spp.

Bla(OXA-51-like), the intrinsic carbapenemase gene in Acinetobacter baumannii previously found only in this species, was detected in a clinical isolate of Acinetobacter genomic species 13tU. this study aimed to characterize this gene in the isolate. Genomic species identification was confirmed by amplified ribosomal DNA restriction analysis and sequence analysis of 16S-23S ribosomal DNA intergenic spacer, rpoB and recA. The bla(OXA-51-like) gene, with an upstream ISAba1 insertion, was plasmid-encoded and the surrounding sequences suggested that its origin was from A. baumannii. Transformation of Acinetobacter genomic species 13TU AtCC 17903 with recombinant plasmid bearing ISAba1-bla(OXA-51-like) from the isolate increased the minimum inhibitory concentrations (MICs) of meropenem and imipenem 256-fold. This is the first report of bla(OXA-51-like) in an organism other than A. baumannii. This plasmid-borne bla(OXA-51-like) gene with an upstream ISAba1 insertion confers a high level of carbapenem resistance to Acinetobacter genomic species 13TU.

Molecular analysis of novel PROP1 mutations associated with combined pituitary hormone deficiency (CPHD).

OBJECTIVE: Homozygous mutations in the gene encoding the pituitary transcription factor PROP1 are associated with combined pituitary hormone deficiency (CPHD) in both mice and humans with a highly variable phenotype with respect to the severity and time of initiation of pituitary hormone deficiency. We have ascertained three pedigrees with PROP1 mutations from a large cohort of patients with variable degrees of CPHD who were screened for mutations in PROP1. RESULTS: Affected individuals from all three pedigrees were found to harbour novel PROP1 mutations. We have identified two siblings in one family who were homozygous for an intronic mutation (c.343-11C > G) that disrupts correct splicing resulting in the loss of exon 3 from the PROP1 transcript. Two siblings from a second, unrelated family are compound heterozygotes for two point mutations in the coding region, a missense mutation (p.R125W) that leads to impaired transcriptional activation, and a deletion of a single nucleotide (c.310delC) resulting in a frameshift and nonfunctional mutant protein. Additionally, we identified a homozygous deletion of the PROP1 locus in two patients born to consanguineous parents. CONCLUSION: Mutations in PROP1 are a frequent cause of familial CPHD. We have described four novel mutations in PROP1 in 3 pedigrees, all resulting in PROP1 deficiency by different mechanisms. The phenotypic variation observed in association with PROP1 mutations both within and between families, together with the evolving nature of hormone deficiencies and sometimes changing pituitary morphology indicates a need for continual monitoring of these patients.