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Figure 1　Maximum-likelihood (ML) tree based on single nucleotide polymorphisms (SNPs) in the core genome among contigs of strains, showing the relationships among type strains of the genus Providencia. Bootstrap values, expressed as percentages of 1,000 replications, are shown at the branching points when >50 %.In addition, P. stuartii and P. rettgeri have been found to cause pneumonia, meningitis, endocarditis, wound infections and bloodstream infections11), and P. stuartii was found to cause invasive endocar-ditis12) and neonatal sepsis13). P. alcalifaciens, P. rettgeri and P. stuartii were isolated from 17.6% of stool samples of patients with diarrhea at the Kansai airport quarantine station in 2002, with vomiting being especially frequent in patients infected with P. rettgeri, indicating that these three Providencia species cause travelers’ diarrhea5). The emergence and spread of carbapenem-resis-tant Gram-negative pathogens have become serious public health problems worldwide14). Most of these carbapenem-resistant isolates produce metallo-β- lactamases (MBLs), including IMP-, NDM- and VIM-type MBLs14), which confer high resistance against all β-lactams (penicillins, cephalosporines and carbapenems) except for monobactams15). Clinical isolates of carbapenem-resistant P. rettgeri producing IMP-1 MBL were first identified by laboratory-based surveillance in the Kinki region of Japan in 200016). Clinical isolates of P. stuartii producing VIM-19 MBL were first identified in 2008 in Algeria17). To date, there have been 16 201Providencia species as human pathogensA study of the enteropathogenicity of P. alcalifa︲ciens isolated from a child and two adults with diar-rhea demonstrated that this species causes diarrhea in humans by invading the intestinal mucosal epithe-lium7). P. alcalifaciens was subsequently isolated from 2.1% of the stool specimens of diarrheal chil-dren younger than 5 years of age, indicating that this organism is significantly associated with diar-rhea8). A large outbreak of food-borne infection caused by P. alcalifaciens occurred among children and teachers at two kindergartens and one high school in November 1996 in Fukui, Japan9). Specifi-cally, of the 610 children and teachers who ate lunch cooked at a single catering facility, 270 showed symptoms of gastroenteritis9). Recent outbreaks of P. alcalifaciens have indicated that infection with this organism is a public health concern in both developing and developed countries10). Although epidemiological studies suggest that P. alcalifaciens causes diarrhea by invading the intestinal mucosa10), the pathogenesis of P. alcalifaciens has not been established at the molecular level.P. stuartii and P. rettgeri have been found to cause hospital acquired urinary tract infections11) and have been shown to be the most common causes of urinary tract infections in hospitalized patients. Emergence of carbapenem-resistant Providencia species