Epidemiology of Campylobacter jejuni infections in Sweden, November 2011–October 2012: is the severity of infection associated with C. jejuni sequence type?

Figures & data

Table 1. The frequency of detection and hospital admission, length of hospital admission and mean age of individuals infected with C. jejuni MLST sequence types (ST) in Sweden, between November 2011 and October 2012

	Identified in this study			Admitted to hospital
C. jejuni type	Number	Percentage	Mean age (range)	Number	Percentage	Mean age (range)	Length of hospitalisation (days)
ST-21	139	12.9	37.3 (0–87)	28	9.7	45.2 (0–87)	3.04
ST-50	116	10.8	39.1 (1–88)	37	12.8	42.7 (2–85)	2.51
ST-45	105	9.8	48.1 (1–87)	34	11.8	57.3 (1–87)	3.41
ST-19	104	9.7	41.6 (2–73)	20	6.9	48.7 (16–73)	3.15
ST-677	90	8.4	50.5 (1–86)	25	8.7	57.9 (1–86)	3.28
ST-48	88	8.2	40.6 (0–89)	24	8.3	44.9 (1–89)	4.21
ST-257	41	3.8	39.8 (0–77)	17	5.9	45.2 (10–77)	2.65
Other^a	392	36.5	43.0 (0–95)	104	36.0	51.9 (2–95)	3.28
All	1,075		42.5 (0–95)	289		50.0 (0–95)	3.20

^aSequence types which were identified in les s than 33 isolates have been combined into this ‘other’ group.

Table 2 Potential covariates and their association with hospitalisation evaluated in univariable analysis using a 2×2 chi-square test in laboratory-confirmed domestic cases of C. jejuni in Sweden, November 2011–October 2012

Variable	Hospitalised/total	Percent	RR	95% CI	P
C. jejuni sequence type
ST-21	28/139	20.1	0.72	0.51–1.02	0.07
ST-50	37/116	31.9	1.21	0.91–1.61	0.24
ST-19	20/104	19.2	0.69	0.46–1.04	0.08
ST-45	34/105	32.4	1.23	0.02–1.66	0.22
ST-677	25/90	27.8	1.04	0.73–1.47	0.92
ST-48	24/88	27.3	1.02	0.71–1.45	1.00
ST-257	17/41	41.5	1.57	1.08–2.30	0.049
Other^a	104/392	26.5	0.98	0.79–1.20	0.89
County
Södermanland	10/34	29.4	1.09	0.65–1.87	0.89
Dalarna	12/38	31.6	1.18	0.73–1.91	0.63
Gävleborg	13/35	37.1	1.40	0.90–2.18	0.23
Västra Götaland	46/214	21.5	0.76	0.57–1.01	0.06
Halland	6/48	12.5	0.45	0.21–0.97	0.03
Jönköping	6/28	21.4	ND^b
Kalmar	8/22	36.4	ND^b
Blekinge	5/16	31.3	ND^b
Värmland	6/33	18.2	0.67	0.32–1.39	0.35
Östergötland	11/35	31.4	1.18	0.71–1.94	0.67
Norrbotten	6/18	33.3	ND^b
Skåne	24/128	18.8	0.67	0.46–0.97	0.04
Stockholm	67/238	28.2	1.06	0.84–1.34	0.68
Västernorrland	5/13	38.5	ND^b
Västerbotten	13/36	36.1	1.36	0.87–2.12	0.28
Uppsala	9/29	31.0	ND^b
Gotland	7/12	58.3	ND^b
Västmanland	7/25	28.0	ND^b
Kronoberg	7/19	36.8	ND^b
Örebro	17/46	37.0	1.40	0.95–2.07	0.16
Jämtland	4/8	50.0	ND^b
Male gender
No	169/638	26.5	–	–	–
Yes	120/437	27.5	1.04	0.85–1.27	0.78
Age (years)
<20	33/169	19.5	0.69	0.50–0.95	0.02
20–39	66/292	22.6	0.80	0.63–1.02	0.07
40–60	74/358	20.7	0.69	0.55–0.87	0.0015
>60	116/256	45.3	2.13	1.76–2.57	<0.0001
Co-morbidity
No	209/978	21.4	–	–	–
Yes	80/97	82.5	4.49	2.91–6.92	<0.0001

Variables with more than two categories (ST, county, and age group) were dichotomised by category, using all the remaining observations were as the reference group (e.g. ST-21 vs all other STs). Results for variables shown to be statistically significantly associated with hospitalisation (P>0.05) are shown in bold face.

^aContains all other C. jejuni sequence types identified in this study.

^bND = not determined for variables with prevalence <3%.

Table 3 Result of multivariable logistic regression analysis of variables associated with hospitalisation of laboratory-confirmed domestic cases of C. jejuni in Sweden, November 2011–October 2012

Variable	OR	95% CI	P
C. jejuni sequence type	0.98	0.93–1.05	0.62
ST-21	0.81	0.48–1.37	0.43
ST-50	1.59	0.96–2.62	0.07
ST-19	0.71	0.39–1.28	0.25
ST-45	1.14	0.67–1.94	0.63
ST-677	0.99	0.56–1.77	0.98
ST-48	1.28	0.72–2.29	0.40
ST-257	2.35	1.15–4.81	0.017
County	1.02	1.00–1.04	0.12
Södermanland	0.89	0.65–1.87	0.81
Dalarna	0.74	0.73–1.91	0.50
Gävleborg	1.09	0.90–2.18	0.85
Västra Götaland	0.59	0.36–0.96	0.033
Halland	0.30	0.21–0.97	0.018
Värmland	0.59	0.32–1.39	0.30
Östergötland	0.86	0.71–1.94	0.72
Skåne	0.43	0.46–0.97	0.007
Stockholm	0.76	0.84–1.34	0.24
Västerbotten	1.14	0.87–2.12	0.75
Örebro	1.31	0.95–2.07	0.48
Age (years)	1.22	1.05–1.43	0.012
20–39	0.99	0.61–1.62	0.61
40–60	0.79	0.48–1.27	0.33
>60	1.98	1.22–3.25	0.006
Co-morbidity (yes)	13.89	7.88–24.46	<0.0001

The ‘other’ categories were used as a reference groups for ST and county variables. Results for variables shown to be statistically significantly associated with hospitalisation (P>0.05) are shown in bold face.

Table 4 Variables investigated for their association with length of hospitalisation evaluated in univariable analysis using Cox regression in laboratory-confirmed domestic cases of C. jejuni in Sweden, November 2011–October 2012

Variable		Me an stay (median)	HR	95% CI	P
C. jejuni sequence type	Other	3.28 days (3 days)	–	–	–
	ST-21	3.04 days (2 days)	1.12	0.74–1.71	0.56
	ST-50	2.51 days (2 days)	1.34	0.92–1.95	0.13
	ST-19	3.15 days (2 days)	1.01	0.63–1.63	0.97
	ST-45	3.41 days (3 days)	0.85	0.58–1.26	0.42
	ST-667	3.28 days (3 days)	0.98	0.63–1.51	0.91
	ST-48	4.21 days (4 days)	0.96	0.62–1.49	0.86
	ST-257	2.65 days (2 days)	1.49	0.89–2.50	0.13
County	Other	3.25 days (2.5 days)	–	–	–
	Eskilstuna	2.30 days (2 days)	1.31	0.67–2.56	0.42
	Falun	2.92 days (3 days)	0.97	0.53–1.81	0.94
	Gävle	2.77 days (2 days)	1.07	0.59–1.95	0.82
	Göteborg	3.28 days (3 days)	0.89	0.61–1.30	0.56
	Halmstad	3.83 days (4 days)	0.89	0.39–2.06	0.79
	Karlstad	2.67 days (2.5 days)	0.84	0.36–1.93	0.68
	Linköping	4.18 days (3 days)	0.77	0.40–1.45	0.42
	Malmö	3.54 days (2.5 days)	0.85	0.52–1.34	0.46
	Stockholm	2.81 days (2 days)	1.30	0.92–1.84	0.13
	Umeå	2.69 days (2 days)	1.22	0.68–2.23	0.50
	Örebro	4.71 days (3 days)	1.05	0.62–1.81	0.84
Male gender	No	3.11 days (2 days)	–	–	–
	Yes	3.34 days (3 days)	1.01	0.80–1.27	0.95
Age (years)	<20	2.53 days (2 days)	–	–	–
	20–39	2.14 days (2 days)	1.02	0.67–1.54	0.92
	40–60	3.12 days (2 days)	0.83	0.56–1.25	0.38
	>60	4.07 days (3 days)	0.73	0.50–1.07	0.11
Co-morbidity	No	2.84 days (2 days)	–	–	–
	Yes	4.16 days (3 days)	0.92	0.73–1.17	0.51