In surviving meningococcal disease patients serogroup B was the most frequent serogroup (60.4%) followed by serogroup C ( 36.7%) and others.
O157 was the most frequent serogroup (33.6 %), although a decrease of this serogroup was seen over the last decade.
Indeed, S. flexneri, as the most frequent serogroup, accounted for 44.0%, 58.0%, and 65.0%, respectively, of shigellosis cases in Saudi Arabia [ 16], Pakistan [ 17] and Jordan [ 18].
Among the 248 cases with confirmed meningococcal etiology, the most frequent serogroup was W135 (n = 121, 48.8%), followed by A (n = 116, 46.8%) and X (n = 2), indicating that serogroup W135 had increased markedly compared with the past 2 years.
In particular, as O26, the most frequent serogroup detected among childcare facilities, tends to be more asymptomatic than O157, asymptomatic cases may contribute to further spread, resulting in larger outbreaks.
Notwithstanding, the most frequent STEC serogroups in patients, except O91, were only rarely found in food.
The distribution of the four most frequent STEC serogroups associated with HUS cases by year is shown in the Figure.
In culture-negative patients for whom serum samples are available, detection of antibodies against LPSs of the most frequent E. coli serogroups associated with HUS (both O157 and non-O157) can be an alternative approach to detect infection with both EHEC and EHEC-LST.
The serogroup found most frequently, serogroup H, was not found at all in two of the farms.
