Transferable Plasmid-Mediated Resistance to Linezolid Due tocfrin a Human Clinical Isolate of Enterococcus faecalis

ABSTRACTNonmutational resistance to linezolid is due to the presence ofcfr, which encodes a methyltransferase responsible for methylation of A2503 in the 23S rRNA. Thecfrgene was first described in animal isolates of staphylococci, and more recently, it has been identified inStaphylococcus aureusfrom human clinical infections, including in an outbreak of methicillin-resistantS. aureus. In enterococci,cfrhas been described in an animal isolate ofEnterococcus faecalisfrom China. Here, we report an isolate of linezolid-resistantE. faecalis(603-50427X) recovered from a patient in Thailand who received prolonged therapy with the antibiotic for the treatment of atypical mycobacterial disease. The isolate lacked mutations in the genes coding for 23S rRNA and L3 and L4 ribosomal proteins and belonged to the multilocus sequence type (MLST) 16 (ST16), which is commonly found in enterococcal isolates from animal sources. Resistance to linezolid was associated with the presence ofcfron an ∼97-kb transferable plasmid. Thecfrgene environment exhibited DNA sequences similar to those of othercfr-carrying plasmids previously identified in staphylococci (nucleotide identity, 99 to 100%). Thecfr-carrying plasmid was transferable by conjugation to a laboratory strain ofE. faecalis(OG1RF) but not toEnterococcus faeciumorS. aureus. Thecfrgene was flanked by IS256-like sequences both upstream and downstream. This is the first characterization of the potential horizontal transferability of thecfrgene from a human linezolid-resistant isolate ofE. faecalis.

Evidence that Human Chlamydia pneumoniae Was Zoonotically Acquired

ABSTRACT Zoonotic infections are a growing threat to global health. Chlamydia pneumoniae is a major human pathogen that is widespread in human populations, causing acute respiratory disease, and has been associated with chronic disease. C. pneumoniae was first identified solely in human populations; however, its host range now includes other mammals, marsupials, amphibians, and reptiles. Australian koalas (Phascolarctos cinereus) are widely infected with two species of Chlamydia, C. pecorum and C. pneumoniae. Transmission of C. pneumoniae between animals and humans has not been reported; however, two other chlamydial species, C. psittaci and C. abortus, are known zoonotic pathogens. We have sequenced the 1,241,024-bp chromosome and a 7.5-kb cryptic chlamydial plasmid of the koala strain of C. pneumoniae (LPCoLN) using the whole-genome shotgun method. Comparative genomic analysis, including pseudogene and single-nucleotide polymorphism (SNP) distribution, and phylogenetic analysis of conserved genes and SNPs against the human isolates of C. pneumoniae show that the LPCoLN isolate is basal to human isolates. Thus, we propose based on compelling genomic and phylogenetic evidence that humans were originally infected zoonotically by an animal isolate(s) of C. pneumoniae which adapted to humans primarily through the processes of gene decay and plasmid loss, to the point where the animal reservoir is no longer required for transmission.

Milkborne Campylobacter Infection in Hungary

In April 1998, an annual 2-day animal farm sale was held in Hódmezővásárhely, where 500 to 600 visitors consumed unpasteurized milk. The first signs of disease began 2 days after the end of the sale. Fifty-two people from a wide age range fell ill, primarily with inflammatory enteritis. These cases included 34 with Campylobacter positivity: 30 with Campylobacter jejuni and 4 with Campylobacter coli. Environmental samples (raw milk, udder swabs, and rectal swabs from 12 cows in the suspected herd) were tested 2 weeks after the first signs of the disease, and two rectal swabs were found to be positive for C. jejuni.. Initially, the epidemic seemed to be sporadic and, accordingly, only 26 human and 2 animal Campylobacter isolates were reserved for randomly amplified polymorphic DNA analysis. This comparative analysis verified that fecally contaminated milk was the source of the outbreak. The DNA-banding patterns of 20 C. jejuni isolates (19 human and 1 animal) were identical. The antibiotic susceptibilities of the Campylobacter isolates were determined, and only six C. jejuni (human) isolates, one C. coli (human) isolate, and one C. jejuni (animal) isolate were resistant to tetracycline, both by disk diffusion and by E test (antimicrobial gradient strip for the quantitative determination of susceptibility or resistance of microorganisms). No plasmid was detected in these tetracycline-resistant isolates. The endotoxin production of Campylobacter isolates was examined via the cytopathogenic effect on the Vero cell line. This effect exhibited various degrees of positivity in 19 cases. Only two human C. jejuni isolates displayed ++++ positivity. Both isolates were from patients who had required antibiotic therapy and hospital care.