Mycoplasma mycoides, from "mycoides Small Colony" to "capri". A microevolutionary perspective.

BACKGROUND: The Mycoplasma mycoides cluster consists of five species or subspecies that are ruminant pathogens. One subspecies, Mycoplasma mycoides subspecies mycoides Small Colony (MmmSC), is the causative agent of contagious bovine pleuropneumonia. Its very close relative, Mycoplasma mycoides subsp. capri (Mmc), is a more ubiquitous pathogen in small ruminants causing mastitis, arthritis, keratitis, pneumonia and septicaemia and is also found as saprophyte in the ear canal. To understand the genetics underlying these phenotypic differences, we compared the MmmSC PG1 type strain genome, which was already available, with the genome of an Mmc field strain (95010) that was sequenced in this study. We also compared the 95010 genome with the recently published genome of another Mmc strain (GM12) to evaluate Mmc strain diversity. RESULTS: The MmmSC PG1 genome is 1,212 kbp and that of Mmc 95010 is ca. 58 kbp shorter. Most of the sequences present in PG1 but not 95010 are highly repeated Insertion Sequences (three types of IS) and large duplicated DNA fragments. The 95010 genome contains five types of IS, present in fewer copies than in PG1, and two copies of an integrative conjugative element. These mobile genetic elements have played a key role in genome plasticity, leading to inversions of large DNA fragments. Comparison of the two genomes suggested a marked decay of the PG1 genome that seems to be correlated with a greater number of IS. The repertoire of gene families encoding surface proteins is smaller in PG1. Several genes involved in polysaccharide metabolism and protein degradation are also absent from, or degraded in, PG1. CONCLUSIONS: The genome of MmmSC PG1 is larger than that of Mmc 95010, its very close relative, but has less coding capacity. This is the result of large genetic rearrangements due to mobile elements that have also led to marked gene decay. This is consistent with a non-adaptative genomic complexity theory, allowing duplications or pseudogenes to be maintained in the absence of adaptive selection that would lead to purifying selection and genome streamlining over longer evolutionary times. These findings also suggest that MmmSC only recently adapted to its bovine host.

Antimicrobial resistance pattern of Salmonella serotypes isolated from apparently healthy slaughtered camels (Camelus dromedarius) in eastern Ethiopia.

A total of 714 samples consisting of faeces, mesenteric lymph nodes, liver, spleen, abdominal and diaphragmatic muscles (each 119) were collected from November 2001 to April 2002 from apparently healthy slaughtered camels (Camelus dromedarius) in eastern Ethiopia. One hundred sixteen (16.2%) Salmonella strains belonging to 16 different serovars were isolated. All Salmonella strains isolated were examined for antimicrobial resistance to 17 selected antimicrobials. The minimum inhibitory concentration (MIC) values were determined by the microdilution broth test. Fifty-two (44.8%) of the Salmonella isolates were resistant to one or more antimicrobials. Thirty-nine of the 52 (75%) resistant Salmonella serovars exhibited multiple resistance to up to eight different antimicrobials. Among the serovars tested, S. Typhimurium, S. Heidelberg, S. Braenderup and S. Hadar displayed multiple resistance mainly to streptomycin (35.3%), spectinomycin (28.4%), sulfamethoxazole (25.0%), ampicillin (24.1%), trimethoprim (22.4%), trimethoprim/sulfamethoxazole (18.9%), tetracycline (12.9%) and colistin (11.2%). All Salmonella strains tested were susceptible to ciprofloxacin, nalidixic acid, gentamicin, kanamycin and neomycin. The present study showed the importance of camels as a potential source of single and multiple resistant Salmonella strains to different antimicrobials that are also used in the public health sector for the treatment of different bacterial diseases in Ethiopia.