4) Other antimicrobial-resistant bacteria
ⅰ. Campylobacter spp.
Source: Tokyo Metropolitan Institute of Public Health
Tokyo Metropolitan Institute of Public Health has conducted trend surveillance concerning the proportion of
antimicrobial-resistant Campylobacter spp. Among the 119 outbreaks of food-borne illness that occurred in Tokyo
in 2019, 36 outbreaks (30.3%) were caused by Campylobacter spp., being the largest cause of bacterial food-borne
illness.[1] Among the Campylobacter jejuni (C. jejuni) isolated from patients with diarrhea in 2018, the proportion
of ciprofloxacin (CPFX)-resistant strains was 51.8%, higher than 2017. The proportion of CPFX-resistant
Campylobacter coli (C. coli) strains was 37.5%, which was lower than the previous year. Note that, however, the
number of tested strains was smaller for C. coli and this should be taken into consideration upon interpretation of
the result.
Table 17. The proportion (%) of antimicrobial-resistant Campylobacter jejuni* isolated from diarrhea
cases
(Number of samples)
EM

2011
(108)
3.7

NA
CPFX

2012
(83)
2.4

53.7
62.7
53.7
62.7
* Strains isolated from diarrhea cases in Tokyo

2013
(85)

2014
(125)

2015
(116)

2016
(113)

2017
(115)

2018
(110)

1.2

0.8

0.9

0.9

1.7

1.8

50.6
50.6

50.4
50.4

37.1
37.1

53.1
52.2

46.1
43.5

51.7
51.8

Prepared from [5] with partial modification.

Table 18. The proportion (%) of antimicrobial-resistant Campylobacter coli* isolated from diarrhea cases
(Number of samples)
EM
NA
CPFX

2011
(8)

2012
(9)

12.5
22.2
87.5
66.7
87.5
66.7
* Strains isolated from diarrhea cases in Tokyo

2013
(12)

2014
(7)

2015
(8)

2016
(14)

2017
(8)

2018
(8)

16.7
75.0
75.0

28.6
57.1
57.1

0.0
50.0
50.0

14.3
50.0
35.7

25.0
62.5
62.5

62.5
50
37.5

Prepared from [5] with partial modification.

ⅱ. Non-typhoidal Salmonella spp.
Source: Public Health Institutes
The 21 Public Health Institutes across Japan conducted research on the multidrug-resistant status of the 2,338
Salmonella strains that were isolated between 2015 and 2019, using standardized methodology.[2] Table 19 lists
the key serotypes of human-derived strains and food-derived strains.
In total, 39.8% of the 1,755 human-derived strains and 91.7% of the 586 food-derived strains indicated
resistance to one or more antimicrobials (Tables 20 and 21). Although this investigation was not conducted as a
routine national surveillance operation, the results here are considered to reflect the current status in Japan, given
that the investigation covered all regions of Japan and the proportion of resistant strains isolated between 2015 and
2019 was similar. Table 20 appears to show that rates of resistance to cephalosporins (CTX, CAZ, CFX) rose in
strains isolated between 2017 and 2019, but the same trend was seen in 2015 and 2016 when the focus was limited
to domestic chicken meat (figures in parentheses), suggesting that the strains isolated between 2017 and 2019
contained a high proportion of strains from foreign chicken meat. As for multidrug resistance, the proportion of
three-drug resistance was large both among human-derived strains and among food-derived strains. Thirty-three
among human-derived strains, and 50 among food-derived strains, indicated multidrug resistance to as many as
six to 11 drugs.
Tables 22 and 23 show antimicrobial resistance in the top two serotypes of food-derived strains (S. Infantis and
S. Schwarzengrund), while Tables 24 to 28 show antimicrobial resistance in the top five serotypes of humanderived strains (S. Infantis, S. Enteritidis, S. Thompson, S. 4:i:-, and S. Saintpaul). Among food-derived strains,
trends in resistance by serotype have many aspects in common, but distinctive features were observed in serotypespecific resistance trends among human-derived strains.
In a comparison of antimicrobial resistance rates between human- and food-derived strains for the three
serotypes (S. Schwarzengrund, S. Infantis, and S. Manhattan) appearing in both the top five serotypes among foodderived strains and the top 10 serotypes among human-derived strains (Table 29), clear similarities were observed
in the overall trends in resistance rates for each serotype between human-derived strains and food-derived strains,
suggesting a strong association between food-derived and human-derived antimicrobial-resistant bacteria.
In addition to antimicrobial susceptibility tests, strains isolated between 2015 and 2018 that demonstrated
resistance to one or more of the agents CTX, CAZ, and CFX (26 human-derived strains and 31 food-derived
strains) underwent testing to detect extended-spectrum beta-lactamase (ESBL) and AmpC beta-lactamase (AmpC)
21