Mycobacterium aquaticum sp. nov., a rapidly growing species isolated from haemodialysis water.

The characterization of five Iranian isolates, four from hospital haemodialysis water and one from the sputum of a patient, led to the detection of a novel mycobacterium species. The strains were characterized by mucoid colonies developing in 3-5 days at temperatures ranging from 25 to 37 °C. The biochemical test pattern was unremarkable while the HPLC profile of mycolic acids resembled that of Mycobacterium fortuitum. The sequences of three major housekeeping genes (16S rRNA, hsp65 and rpoB) were unique and differed from those of any other mycobacterium. Mycobacterium brisbanense, which is the species that shared the highest 16S rRNA gene sequence similarity (99.03 %), was distinct, as shown by the average nucleotide identity and by the genome to genome distance values (91.05 and 43.10 %, respectively). The strains are thus considered to represent a novel species of the genus Mycobacterium, for which the name Mycobacterium aquaticum sp. nov. is proposed. The type strain is RW6T (=DSM 104277T=CIP111198T).

Survey of 150 strains belonging to the Mycobacterium terrae complex and description of Mycobacterium engbaekii sp. nov., Mycobacterium heraklionense sp. nov. and Mycobacterium longobardum sp. nov.

A thorough phenotypic and genotypic analysis of 150 strains belonging to the Mycobacterium terrae complex resulted in the identification of a number of previously unreported sequevars (sqvs) within the species known to belong to the complex. For the species Mycobacterium arupense, three sqvs were detected in the 16S rRNA gene, six sqvs in the hsp65 gene and 15 sqvs in the rpoB gene; in Mycobacterium senuense two sqvs were present in each of the three genetic regions; in Mycobacterium kumamotonense four, two and nine sqvs were found, respectively, and in M. terrae three, four and six sqvs were found, respectively. The inappropriate inclusion of Mycobacterium triviale within the M. terrae complex was confirmed. The limited utility of biochemical tests and of mycolic acid analyses for the differentiation of the members of M. terrae complex was also confirmed. The survey allowed the recognition of three previously undescribed species that were characterized by unique sequences in the 16S rRNA, hsp65 and rpoB genes. Mycobacterium engbaekii sp. nov. (proposed previously 40 years ago but never validly published) was characterized by pink photochromogenic pigmentation and rapid growth; phylogenetically it was related to Mycobacterium hiberniae. The type strain of this species, of which eight strains were investigated, is ATCC 27353(T) ( = DSM 45694(T)). A cluster of 24 strains was the basis for the description of Mycobacterium heraklionense sp. nov., which has an intermediate growth rate and is unpigmented; nitrate reductase activity is typically strong. Closely related to M. arupense with respect to the 16S rRNA gene, M. heraklionense sp. nov. could be clearly differentiated from the latter species in the other genetic regions investigated. The type strain is NCTC 13432(T) ( = LMG 24735(T) = CECT 7509(T)). Mycobacterium longobardum sp. nov., represented in the study by seven strains, was characterized by a unique phylogenetic location within the M. terrae complex, clearly divergent from any other species. The type strain is DSM 45394(T) ( = CCUG 58460(T)).

Mycobacterium europaeum sp. nov., a scotochromogenic species related to the Mycobacterium simiae complex.

Four strains isolated in the last 15 years were revealed to be identical in their 16S rRNA gene sequences to MCRO19, the sequence of which was deposited in GenBank in 1995. In a polyphasic analysis including phenotypic and genotypic features, the five strains (including MCRO19), which had been isolated in four European countries, turned out to represent a unique taxonomic entity. They are scotochromogenic slow growers and are genetically related to the group that included Mycobacterium simiae and 15 other species. The novel species Mycobacterium europaeum sp. nov. is proposed to accommodate these five strains. Strain FI-95228(T) ( = DSM 45397(T)  = CCUG 58464(T)) was chosen as the type strain. In addition, a thorough revision of the phenotypic and genotypic characters of the species related to M. simiae was conducted which leads us to suggest the denomination of the 'Mycobacterium simiae complex' for this group.

Molecular characterization of acinetobacter isolates collected in intensive care units of six hospitals in Florence, Italy, during a 3-year surveillance program: a population structure analysis.

The strain diversity and the population structure of nosocomial Acinetobacter isolated from patients admitted to different hospitals in Florence, Italy, during a 3-year surveillance program, were investigated by amplified fragment length polymorphism (AFLP). The majority of isolates (84.5%) were identified as A. baumannii, confirming this species as the most common hospital Acinetobacter. Three very distinct A. baumannii clonal groups (A1, A2, and A3) were defined. The A1 isolates appeared to be genetically related to the well-characterized European EU II clone. A2 was responsible for three outbreaks which occurred in two intensive care units. Space/time population dynamic analysis showed that A1 and A2 were successful nosocomial clones. Most of the A. baumannnii isolates were imipenem resistant. The genetic determinants of carbapenem resistance were investigated by multiplex PCR, showing that resistance, independently of hospital origin, period of isolation, or clonal group, was associated with the presence of a bla (OXA-58-like) gene and with ISAba2 and ISAba3 elements flanking this gene. bla (OXA-58) appeared to be horizontally transferred. This study showed that the high discriminatory power of AFLP is useful for identification and typing of nosocomial Acinetobacter isolates. Moreover the use of AFLP in a real-time surveillance program allowed us the recognition of clinically relevant and widespread clones and their monitoring in hospital settings. The correlation between clone diffusion, imipenem resistance, and the presence of the bla(OXA-58-like) gene is discussed.

Molecular surveillance and population structure analysis of methicillin-susceptible and methicillin-resistant Staphylococcus aureus in high-risk wards.

In this study we report the results of analysis of 253 isolates of Staphylococcus aureus (132 methicillin [meticillin]-resistant S. aureus [MRSA] isolates and 121 methicillin-susceptible S. aureus [MSSA] isolates) from 209 patients admitted to 18 high-risk wards of six hospitals located in Florence, Italy, over an 8-month period during which a program of epidemiological surveillance of hospital-acquired infections was conducted. The majority (69%) of the 87 reported S. aureus infections were caused by MRSA. No outbreak events have been reported. All the isolates were typed by amplified fragment length polymorphism (AFLP), and AFLP profiles were analyzed in order to define similarity groups. The discriminatory power of AFLP is very high with MSSA (Simpson index of diversity [D], 95.9%), whereas its resolution capability with MRSA (D, 44.7%) is hampered by the well-known high clonality of these populations (the main MRSA group accounted for 74% of the MRSA isolates). Combining AFLP, improved by visual inspection of polymorphisms, with multiplex PCR greatly increases MRSA resolution (D, 85.5%), resolving the MRSA population to a level that is one of the highest reported in the literature. Widespread and sporadic clones of MSSA and MRSA were identified, and their diffusion in the different hospitals and wards over the surveillance period was studied. The understanding of MSSA and MRSA population structures should be the starting point for the design of a more rational surveillance program for S. aureus species, maximizing benefits and reducing the cost of infection control strategies.