David J. Waine

Environmental Burkholderia cepacia complex isolates in human infections

Members of the Burkholderia cepacia complex (Bcc), found in many environments, are associated with clinical infections. Examining diverse species and strains from different environments with multilocus sequence typing, we identified >20% of 381 clinical isolates as indistinguishable from those in the environment. This finding links the natural environment with the emergence of many Bcc infections.

Elucidating Global Epidemiology of Burkholderia multivorans in Cases of Cystic Fibrosis by Multilocus Sequence Typing

ABSTRACT Burkholderia multivorans is a prominent B. cepacia complex (BCC) species causing infection in people with cystic fibrosis. Despite infection control measures being introduced to reduce the spread of BCC there is a continued emergence of infections by B. multivorans. Our objective was to analyze a global collection of B. multivorans isolates, comparing those from environmental and clinical sources with those from reported outbreaks. Multilocus sequence typing (MLST) was performed on 107 B. multivorans isolates to provide a detailed analysis of the global population biology of this species. MLST resolved 64 B. multivorans sequence types. Twelve of these were globally distributed and associated with human infection; two of these (ST-21 and ST-375) were also composed of environmental isolates. These global lineages included strains previously linked to large outbreaks (e.g., French epidemic clone ST-16). Though few environmental isolates of B. multivorans were available for analysis, of six strains identified, three were identical to strains recovered from cystic fibrosis (CF) infection. Although the ability of B. multivorans to cause CF outbreaks is known, our report here concerning the existence of globally distributed B. multivorans CF strains is a new observation for this emerging B. cepacia complex pathogen and suggests that certain strain types may be better adapted to human infection than others. Common transmission-associated risk factors were not obviously linked to the globally distributed strains; however, the overlap in strains recovered from water environments, industrial products, and human infection suggests that environmental sources may be an important reservoir for infection with B. multivorans.

Association between Hypermutator Phenotype, Clinical Variables, Mucoid Phenotype, and Antimicrobial Resistance in Pseudomonas aeruginosa

ABSTRACT The presence of hypermutator Pseudomonas aeruginosa was associated with poorer lung function in patients at the Adult West Midlands CF Unit. Mucoid isolates were more likely to be hypermutators. The presence of resistant mutant subpopulations was associated with hypermutator phenotype but was not good enough to be used as a test for this phenotype.

Cross-Sectional and Longitudinal Multilocus Sequence Typing of Pseudomonas aeruginosa in Cystic Fibrosis Sputum Samples

ABSTRACT Multilocus sequence typing (MLST) is a genetic typing tool designed to provide information about the relatedness of isolates at the core genome level. The utility of MLST in regard to cystic fibrosis (CF)-related infection with Pseudomonas aeruginosa is unknown. The molecular clock speed of the MLST genes was studied using 219 colonies isolated longitudinally from 49 patients with CF. A cross-sectional study examining 27 to 46 colonies per sputum sample for samples from 16 patients was also undertaken. The molecular clock speed was estimated to be 2.05 × 10−5 (upper 95% confidence limit) or 4.75 × 10−6 (50% confidence limit) point mutations per nucleotide per year. In the cross-sectional study, 50% of patients were infected with more than one sequence type. There was evidence of point mutations, recombination events, and coinfection with epidemic and unique strains. A clonal complex that was highly genetically distinct from the rest of the P. aeruginosa population was identified. The MLST scheme uses genes with an appropriate clock speed and provides useful information about the genetic variation of P. aeruginosa within and between patients with CF.

The effect of intravenous antibiotics on anaemia in cystic fibrosis

Infective exacerbation +0.7 (51) b0.001 Anaemic on admission Infective exacerbation +0.2 (105) 0.047 Not anaemic on admission a Infective exacerbation +0.6 (21) 0.005 Anaemic on admission On iron supplements Infective exacerbation +0.7 (30) b0.001 Anaemic on admission Not on iron supplements Other, varied reasons for admission, −1.6 (8) The report by Hoo and Wildman [1] of their experience of parenteral iron infusions makes cautionary reading. Traditional measure of iron deficiency (serum iron, ferritin, transferrin, transferrin saturation) does not distinguish between “true” iron deficient anaemia and the anaemia of chronic disease caused by the physiological restriction of iron [2]. Dietary iron is absorbed by duodenal enterocytes. It is released into the circulation by the iron exporter protein, ferroportin. When ferroportin activity is low, iron accumulates in enterocytes and is lost when old enterocytes are sloughed into the gut lumen. Ferroportin on the surface ofmacrophages regulates the release of iron, which is recycled when aged red blood cells are destroyed. Ferroportin activity is controlled by hepcidin, a peptide produced by the liver, which also has anti-microbial activity. Hepcidin causes ferroportin internalisation and degradation. So, when hepcidin levels are high, iron accumulates in enterocytes and macrophages, restricting availability to erythropoietic cells and resulting in anaemia [4,5]. Hepcidin levels fall in response to anaemia and hypoxaemia, but increase in response to high levels of interleukin-6 (IL6) found in infection and inflammation [3,4]. Suppressing this inflammatory response will reduce hepcidin and increase iron availability. Therefore, we tested whether treatment of exacerbations with antibiotics resulted in an increase in haemoglobin, without the use of intravenous iron. 200 consecutive admissions of patients between January 2008 and January 2013 with cystic fibrosis were analysed. Haemoglobin concentrations in blood samples taken nearest the admission and discharge dates were compared. Admissions were divided according to reason for admission, and subdivided according to the presence of anaemia on admission and whether the patient was already on oral iron supplements at time of admission. Many admissions for reasons other than treatment of infective exacerbations were brief and only 1 blood sample had been taken and so