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

First reported isolation of hemin-requiring Proteus vulgaris small-colony variant from urine culture

A hemin-requiring Proteus vulgaris small-colony variant (SCV) was isolated from a urine culture. This isolate was grown on 5% sheep blood agar but not on modified Drigalski agar. The single nucleotide substitution was found in the SCV of the hemC gene (c.55C > T), and this substitution caused a nonsense mutation (p.Gln19Ter). Porphyrin test results showed that the biosynthesis of δ-aminolevulinic acid stopped up to porphobilinogen and not pre-uroporphyrinogen due to a mutation in the hemC gene. To our knowledge, this is the first report of hemin-requiring P. vulgaris.

Septic shock caused by a carbon dioxide-dependent and extended spectrum β-lactamase-producing Proteus mirabilis small colony variant in a long-term bedridden patient

Here, we report a 60-year-old chronically bedridden man with cerebral palsy who had septic shock following a history of urinary tract infection with extended spectrum β-lactamase-producing and auxotrophic Proteus mirabilis detected on blood and urine cultures. This auxotroph formed small colonies only on the blood agar at 24 h in 5% CO₂, but not in the conditions without CO₂, and lacked motility and some biochemical activities. The five-year history of stones in the right renal pelvis suggests chronic urinary tract infection with P. mirabilis requiring a 28-day antibiotic treatment. This paper highlights that the CO₂-dependent P. mirabilis small colony variant may cause sepsis, probably due to chronic infection in uroliths, which should warrant immediate identification.

Isolation of thymidine-dependent and extended-spectrum-β-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 β-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 bla_{CTX-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.