Andrea Buzzigoli

Long-Term Effects of Hospital Water Network Disinfection on Legionella and Other Waterborne Bacteria in an Italian University Hospital

OBJECTIVE AND DESIGN Legionella control still remains a critical issue in healthcare settings where the preferred approach to health risk assessment and management is to develop a water safety plan. We report the experience of a university hospital, where a water safety plan has been applied since 2002, and the results obtained with the application of different methods for disinfecting hot water distribution systems in order to provide guidance for the management of water risk. INTERVENTIONS The disinfection procedures included continuous chlorination with chlorine dioxide (0.4-0.6 mg/L in recirculation loops) reinforced by endpoint filtration in critical areas and a water treatment based on monochloramine (2-3 mg/L). Real-time polymerase chain reaction and a new immunoseparation and adenosine triphosphate bioluminescence analysis were applied in environmental monitoring. RESULTS After 9 years, the integrated disinfection-filtration strategy significantly reduced positive sites by 55% and the mean count by 78% (P < .05); however, the high costs and the occurrence of a chlorine-tolerant clone belonging to Legionella pneumophila ST269 prompted us to test a new disinfectant. The shift to monochloramine allowed us to eliminate planktonic Legionella and did not require additional endpoint filtration; however, nontuberculous mycobacteria were isolated more frequently as long as the monochloramine concentration was 2 mg/L; their cultivability was never regained by increasing the concentration up to 3 mg/L. CONCLUSIONS Any disinfection method needs to be adjusted/fine-tuned in individual hospitals in order to maintain satisfactory results over time, and only a locally adapted evidence-based approach allows assessment of the efficacy and disadvantages of the control measures.

High phylogenetic proximity of isolates of Mycobacterium avium subsp. hominissuis over a two decades-period.

The genetic diversity of 47 human isolates of Mycobacterium avium subsp. hominissuis (MAH) was determined by MIRU-VNTR genotyping. Sixteen unique VNTR patterns and eight clusters including a total 39 isolates were detected; six clusters included strains isolated during at least a 15-year period. Minimum spanning tree analysis showed that 14 VNTR patterns, occurring either as clustered or unique isolates, differed from the nearest one for one allelic variation and that the remaining two patterns differed for two allelic variations. The high phylogenetic proximity of the isolates, even over a long time period, indicates that the MAH genotype is highly homogeneous and conserved.

Genomic Variability of Mycobacterium tuberculosis Strains of the Euro-American Lineage Based on Large Sequence Deletions and 15-Locus MIRU-VNTR Polymorphism

A sample of 260 Mycobacterium tuberculosis strains assigned to the Euro-American family was studied to identify phylogenetically informative genomic regions of difference (RD). Mutually exclusive deletions of regions RD115, RD122, RD174, RD182, RD183, RD193, RD219, RD726 and RD761 were found in 202 strains; the RDRio deletion was detected exclusively among the RD174-deleted strains. Although certain deletions were found more frequently in certain spoligotype families (i.e., deletion RD115 in T and LAM, RD174 in LAM, RD182 in Haarlem, RD219 in T and RD726 in the “Cameroon” family), the RD-defined sublineages did not specifically match with spoligotype-defined families, thus arguing against the use of spoligotyping for establishing exact phylogenetic relationships between strains. Notably, when tested for katG463/gyrA95 polymorphism, all the RD-defined sublineages belonged to Principal Genotypic Group (PGG) 2, except sublineage RD219 exclusively belonging to PGG3; the 58 Euro-American strains with no deletion were of either PGG2 or 3. A representative sample of 197 isolates was then analyzed by standard 15-locus MIRU-VNTR typing, a suitable approach to independently assess genetic relationships among the strains. Analysis of the MIRU-VNTR typing results by using a minimum spanning tree (MST) and a classical dendrogram showed groupings that were largely concordant with those obtained by RD-based analysis. Isolates of a given RD profile show, in addition to closely related MIRU-VNTR profiles, related spoligotype profiles that can serve as a basis for better spoligotype-based classification.

Best practice approach to the risk management of Legionella infection in health care facilities

Aim of this study is to summarize and re-evaluate our eight year experience in the application of a water safety plan (WSP) in a 1500-bed teaching hospital.

Is multi-drugs resistant Acinetobacter baumannii epidemic spread related to reduced susceptibility to biocides?

Aim of this study was to assess the role of active extrusion in mediating decreased susceptibility to biocides in the persistance and spread of multi-drugs resistant of A. baumannii strains isolated in intensive care units of a tertiary-care teaching hospital.