Isolation of thymidine-dependent and extended-spectrum-ß-lactamase-producing Escherichia coli small-colony variant from urine of a septuagenarian female patient with recurrent cystitis: A case report with genetic investigation.

Thymidine-dependent small-colony variant (TD-SCV) of Escherichia coli was isolated from urine of a septuagenarian female patient on hemodialysis suffering from recurrent cystitis. The patient had been treated with frequent administrations of trimethoprim sulfamethoxazole (SXT), every time her cystitis symptoms developed. In the TD-SCV isolate, the deletion was detected in the thyA gene associated with thymidylate synthase. Interestingly, the isolate was found to produce extended-spectrum ß-lactamase (ESBL), and the experiment on conjugational transfer of the resistance trait was successful. By means of genetic analysis, the isolate was found to carry blaCTX-M-1 group. To the best of our knowledge, this is the first report of urinary tract infection caused by the transmissible ESBL-producing TD-SCV of E. coli. MICs of the TD-SCV were obtained only on the Mueller Hinton agar media supplemented with appropriate concentrations of thymidine, which might lead to the difficulty for proper chemotherapy in daily medicine. Furthermore, transmission of the ESBL gene via plasmid should be of concern.

Characterization of first hemin-requiring Pseudomonas aeruginosa small-colony variants from the blood of an octogenarian male-patient with double pneumonitis.

A hemin-requiring Pseudomonas aeruginosa small-colony variant (SCV) was isolated from the blood of an octogenarian male-patient with double pneumonitis. The isolate was capable of growing on both sheep blood and chocolate agars but not on MacConkey agars without blood ingredient. Furthermore, the isolate revealed to grow only around the X-factor impregnated discs when examined using the X and V disc strips. However, not only RapID-NH system but also the VITEK2 system failed to identify the isolate. The isolate was finally identified as P. aeruginosa by the sequence of the 16S rRNA genes and the MALDI-TOF MS analysis. Interestingly, the isolate represented positive reaction for δ-aminolaevulinic acid (ALA)-test despite the requirement of hemin. Detailed analysis indicated that the isolate produced protoporphyrin IX from ALA. Therefore, the reason for the hemin dependence was deduced the dysfunction of hemH-encoded ferrochelatase behaving at the end of biosynthetic pathway of heme. However, the genetic analysis of hemH gene demonstrated no variations of both the DNA and the amino-acid sequences. To the best of our knowledge, this is the first clinical isolation of a hemin-dependent P. aeruginosa SCV from blood.