S. De Lorenzi

Codon and Aminoacid Usage Patterns in Mycobacteria

The large number of organisms and of genes sequenced at the present time permits now to study molecular evolution in such lower clades as genera, species, and subspecies. Here, we focus our attention on the genus Mycobacterium, in which we examined codon and aminoacid usage in 13 species, and in 12 subspecies for a total of 8,836,513 codons from 26,755 sequences. Within the genus Mycobacterium, frequencies of codon and aminoacid usage correlate between species and between subspecies. In the groups studied, aminoacid molecular weight and codon degeneracy influence correlations between frequencies, while GC content is the main factor influencing the effective number of codons. The coding GC, which is highly correlated with total genomic GC content, seems to be the main factor influencing present synonymous codon usage in the genus. In particular, the GC content at the 3rd base position seems to shape heavily the effective number of codons, giving indication that here mutational bias dominates over translational selection. Evolutionary trees based on codon and aminoacid usage are consistent with traditional phylogenies of species within the genus.

General preadaptation of viral infectors to their hosts.

We tested the hypothesis of optimal adaptation of viral infectors to eukaryotic hosts, using (1) correlation in codon and amino acid usage between organisms, and (2) canonical correlation between groups of hosts and infectors. The codon correlations between parasites and hosts vary, being low between swine and African swine fever virus (ASF; r = 0.18), and highest between potato and potato virus X (r = 0.60). The correlations might indicate different stages of evolution toward optimal adaptation of the parasite codon distribution to the host tRNA pools. The amino acid correlations vary from r = 0.71 between pig and ASF, to 0.88 between catfish and its herpesvirus. It was observed that both in virus and hosts, there is a negative correlation between frequency of an amino acid and molecular weight. Therefore, it was advanced that viral infectors might be preadapted to their hosts because of similarities of the tRNA pools of hosts, and that evolution toward optimization would be dependent on the size of the divergence between the codon distributions of infector and host. Preadaptation does not imply origin of the virus by lateral transfer from the present host, since the correlation of the molecular weight of amino acids with their abundance in proteins is a general phenomenon.

Reducing microbial contamination of surfaces using RelyOn Virkosept aerosol spray

1. Manian FA, Griesenauer S, Senkel D. Impact of an intensive terminal cleaning and disinfection (C/D) protocol involving selected hospital rooms on endemic nosocomial infection (NI) rates of common pathogens at a tertiary care medical center. 5th Decennial Meeting of the Society for Healthcare Epidemiology of America (SHEA); Atlanta, GA, USA. Abstract LB6. 2010. 2. Boyce JM, Havill NL, Otter JA, et al. Impact of hydrogen peroxide vapor room decontamination on Clostridium difficile environmental contamination and transmission in a healthcare setting. Infect Control Hosp Epidemiol 2008;29: 723–729. 3. Otter JA, French GL. Survival of nosocomial bacteria and spores on surfaces and inactivation by hydrogen peroxide vapor. J Clin Microbiol 2009;47:205–207. 4. Department of Health and NHS Purchasing and Supply Agency. HCAI Technology Innovation Programme. Showcase Hospitals report number 3. The Bioquell Hydrogen Peroxide Vapour (HPV) Disinfection System. 5. Otter JA, Puchowicz M, Ryan D, et al. Feasibility of routinely using hydrogen peroxide vapor to decontaminate rooms in a busy United States hospital. Infect Control Hosp Epidemiol 2009;30:574–577. 6. DepartmentofHealthandHealthProtectionAgency.Clostridiumdifficile infection:how to deal with the problem. Department of Health, London (2009). T. Cooper* M. O’Leary S. Yezli J.A. Otter South London Healthcare NHS Trust, Sidcup, UK Southampton University Hospitals NHS Trust, UK Bioquell, Andover, Hampshire, UK * Corresponding author. Address: Director of Infection Prevention & Control, Trust Management Offices, South London Healthcare NHS Trust, Queen Mary’s Hospital, Frognal Avenue, Sidcup DA14 6LT, UK. Tel.: þ44 (0) 208 302 2678. E-mail address: tcooper1@nhs.net (T. Cooper).

Use of terminal filters to prevent Legionnaires' disease

In developed countries, the incidence of inpatient hospital-acquired infections has been estimated to range between 5.1% and 11.6%, worsening patients’ health and leading to a number of deaths that would not have been expected on the basis of the pathologies for which they had been admitted. Water in the mains plays an important role in the onset of hospital-acquired infections, particularly given the rise in pulmonary disease due to Legionella pneumophila. Advantages of using antibacterial terminal filters at the points where such water is drawn are that application can be limited to the departments with high-risk patients, and installation and maintenance are simple and inexpensive. We assessed the efficacy of SBS water main terminal filters (Nuova S.B. System S.r.l., Paderno Dugnano, Milan, Italy; Model WF1 for washbasins and bidets and Model WF2 for showers and water-birth tubs) composed of a polypropylene prefilter (1 mm) and a double-layer polyethersulphone filtration membrane (0.2 mm). Under experimental laboratory conditions, we initially assessed the ability of these filters to retain high bioburdens (> 1 10) of Brevundimonas diminuta ATCC 19146 which, given its reduced size (0.2e0.9 mm), is indicated in the ASTM F 838-05 Guidelines as the micro-organism of choice for testing filtering membranes. Subsequently, the effectiveness of these filters as a method of prevention of legionellosis was tested for 30 days in hospital departments. For each filter analysed, one 100-mL aliquot of the suspension was drawn upstream of the filter and three 100mL aliquots of the filtered suspension were drawn downstream. From the prefilter aliquot, following dilution of 1 10 , 1-mL replicates of the suspension were used for mass seeding in a suitable agar culture medium. The postfilter aliquots were filtered through sterile membrane filters (0.20 mm) and deposited on the surfaces of a suitable agar culture medium. The number of developed colonies was counted. The filters remained able to retain the entire initial bioburden of B. diminuta for up to 42 days, and thus beyond the 31 days stated by the manufacturer. Next, the ability of the filters, installed at the terminal points along the water mains in three hospital facilities in northern Italy, to retain Legionella pneumophila was evaluated. At Facility A, 40 points along the mains were taken into account (37 washbasins and bidets, three showers), all of which were devoid of terminal filters. The number of L. pneumophila colonies was <1000 colony-forming units (CFU)/L at 20 points, between 1000 and 10,000 CFU/L at 17 points, and >10,000 (peak of 26,000 CFU/L) at three points along the mains. The most common serotype was Group 2e14 (34 cases), while Group 1 was found in five cases. Legionella was not found in any of the water samples drawn at the 26 points along the mains where filters had been installed for 30 days, including 21 showers or bidets. At Facility B, 21 terminal points without filters and 13 taps with filters were examined. Of the points without filters, the L. pneumophila count was <1000 CFU/L at 18 points and >10,000 (peak of 60,000 CFU/L) at three points. When identified, Group 1 was the main serotype, and three cases of Group 2e14 were identified. Legionella was not found at any of the points where the filters had been installed for 30 days. At Facility C, 16 terminal points without filters and 18 taps with filters were examined. At the points without filters, the L. pneumophila count was <1000 CFU/L at two points, between 1000 and 10,000 CFU/L at eight points, and >10,000 CFU/L (peak of 34,000 CFU/L) at six points. Legionella was not found at any of the points where the filters had been installed for 30 days. From the above, it is clear that SBS filters (Model WF) are an effective way to reinstate the quality of water from contaminated mains under experimental conditions.

Persistent bactericidal action by a silver disinfectant on surfaces of hospital furniture.

Aims: In hospitals, surfaces are often colonized by potentially pathogenic micro organisms which can remain alive for long periods of time, thus playing a major role in hospitalacquired infections. One way to overcome this drawback could be to use disinfectants with long-term action. Recent studies have shown that not only do disinfectants containing silver present an immediate effect, reducing the surface bacterial load, but that this action also appears persistent in time. This work assesses the bactericidal activity of a long-lasting disinfectant complex composed of silicon oxide, silver ions and a cationic surfactant (BACTERCLINE ENERGY BLAST) applied on the surfaces of two surgery ward rooms and left in place for different amounts of time (15 min and 72 hours). Study Design: An experimental study. Place and Duration of Study: The investigation was carried out in two rooms of a surgical ward at the Villa Erbosa health care facility in Bologna (Italy) over a period of seven weeks. Methodology: The samples were taken using contact plates (diameter: 24 cm) containing an adequate agar culture medium (Tryptic Soy Agar). After incubation at the temperature of 36±1oC for 24 and 48h, the number of colonies was counted and the statistical analysis of results was performed. Results: The product was able to achieve a high degree of decontamination (around 90%) Research Article British Microbiology Research Journal, 3(2): 158-164, 2013 159 immediately after application and that, after 72 hours, decontamination remained at about 55%. The results are statistically significant. Conclusion: It may be concluded that the tested product could be profitably used to decontaminate surfaces in hospital wards.