Takashi Shinzato

Legionella pneumophila NudA Is a Nudix Hydrolase and Virulence Factor

ABSTRACT We studied the identity and function of the 528-bp gene immediately upstream of Legionella pneumophila F2310 ptsP (enzyme INtr). This gene, nudA, encoded for a Nudix hydrolase based on the inferred protein sequence. NudA had hydrolytic activity typical of other Nudix hydrolases, such as Escherichia coli YgdP, in that ApnA’s, in particular diadenosine pentaphosphate (Ap5A), were the preferred substrates. NudA hydrolyzed Ap5A to ATP plus ADP. Both ptsP and nudA were cotranscribed. Bacterial two-hybrid analysis showed no PtsP-NudA interactions. Gene nudA was present in 19 of 20 different L. pneumophila strains tested and in 5 of 10 different Legionella spp. other than L. pneumophila. An in-frame nudA mutation was made in L. pneumophila F2310 to determine the phenotype. The nudA mutant was an auxotroph that grew slowly in liquid and on solid media and had a smaller colony size than its parent. In addition, the mutant was more salt resistant than its parent and grew very poorly at 25°C; all of these characteristics, as well as auxotrophy and slow-growth rate, were reversed by transcomplementation with nudA. The nudA mutant was outcompeted by about fourfold by the parent in competition studies in macrophages; transcomplementation almost completely restored this defect. Competition studies in guinea pigs with L. pneumophila pneumonia showed that the nudA mutant was outcompeted by its parent in both lung and spleen. NudA is of major importance for resisting stress in L. pneumophila and is a virulence factor.

Computed tomographic features of 23 sporadic cases with Legionella pneumophila pneumonia

OBJECTIVE To describe the chest computed tomographic (CT) findings of Legionella pneumophila pneumonia. METHODS CT scans obtained from 23 sporadic cases of L. pneumophila pneumonia were retrospectively reviewed. Chest CT findings were analyzed with regard to the patterns and distributions of pulmonary abnormalities. We also analyzed the histopathology of lungs from guinea pigs with experimentally induced L. pneumophila pneumonia. RESULTS Consolidation and ground-glass opacity (GGO) were the main findings of CT scans in L. pneumophila pneumonia. The distribution of opacities was categorized as non-segmental (n=20) and segmental (n=4). Non-segmental distribution may follow an onset of segmental distribution. Pleural effusion was observed in 14 (58.3%) patients, of which 13 were accompanied with non-segmental distribution. Abscess formation was observed in only one immunocompromised patient. In the animal pneumonia model, the lesions comprised of terminal bronchioles, alveolar spaces, and interstitia. Small bacilli were observed to be contained by many macrophages within the alveoli. CONCLUSION Non-segmental distribution was significantly more frequent than segmental distribution in L. pneumophila pneumonia. It is possible that L. pneumophila infection initially results in segmental pneumonia, which progresses to typical non-segmental distribution.

A hemin auxotrophic Enterobacter cloacae clinical isolate with increased resistance to carbapenems and aminoglycosides

Small-colony variants (SCVs) were obtained from an Enterobacter cloacae clinical isolate in Okinawa, Japan. One variant showed auxotrophy for hemin with a deletion of 20 365 nucleotides, dosC-ydiK-mmuP-mmuM-tauA-tauB-tauC-tauD-hemB-yaiT-yaiV-ampH-yddQ-sbmA-yaiW-yaiY-yaiZ, including hemB, and was more resistant to aminoglycosides and carbapenems, but more susceptible to aztreonam, than the parent strain.

Falciparum Malaria Incidentally Pretreated with Azithromycin

A 65-year-old man, who recently returned from Liberia, visited a clinic complaining of fever, and azithromycin was prescribed. The patient presented to a general hospital 5 days after the onset of symptoms, however, a blood smear examination failed to detect malaria. Contrary to the blood smear result, a rapid antigen test in our hospital was strongly-positive for falciparum malaria, indicating a high level of malarial antigen in the blood. Moreover, laboratory examinations on admission showed a tendency for improvement. We assumed that the administration of azithromycin partially treated malaria, thus complicating the blood smear diagnosis. We should be careful in prescribing azithromycin, which is widely used in clinics, to travelers returning from malaria-endemic countries.