Beta-haemolytic group A streptococci emm75 carrying altered pyrogenic exotoxin A linked to scarlet fever in adults.
OBJECTIVE
To determine the etiological cause of a food-borne outbreak of scarlet fever in adults.


METHODS
Swabs from the throats of the patients and asymptomatic control were cultured on blood agar plates individually. Biochemical identification of all isolates was performed with a VITEX automated system. Antibiotic susceptibility was examined by using the Kirby-Bauer disc diffusion method. emm gene and extracellular pyrogenic exotoxins of each isolate were amplified by using polymerase chain reaction and subjected to DNA sequencing. Sequence differences between the isolated and the highly similar reference sequences were compared on BLAST. Bioinformatics was used to predict protein structures.


RESULTS
Beta-haemolytic group A streptococci (GAS) emm75 were identified from 10 of 13 available patients. The isolates were susceptible to penicillin, ampicillin, vancomycin, cefatriaxone, ofloxacin, linezolid and quinupristin. All of the isolates carried pyrogenic exotoxin A (speA) and cysteine protease (speB). Isolated speA was phylogenetically different from 30 highly similar references on BLAST. Differences in the primary sequence of the deduced protein were 14.37-20.12% between the speA and each of 11 references. Secondary protein structure of the speA was different from the references at the N-terminal.


CONCLUSIONS
GAS emm75 encoding altered speA was responsible for the food-borne outbreak of scarlet fever in adults.
Dong
Hongjun
H
Department of Infectious Disease, Ningbo Municipal Center for Disease Control and Prevention, Ningbo 315010, China.
Xu
Guozhang
G
Li
Shuhua
S
Song
Qifa
Q
Liu
Shijian
S
Lin
Hui
H
Chai
Yibiao
Y
Zhou
Aimin
A
Fang
Ting
T
Zhang
Hongwei
H
Jin
Chunguang
C
Lu
Wei
W
Cao
Guangwen
G
D000293:Adolescent; D000328:Adult; D000667:Ampicillin / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001427:Bacterial Toxins / Q000235:genetics*; D002506:Cephalexin / Q000494:pharmacology; D002645:Chickens / Q000382:microbiology; D002648:Child; D002681:China / Q000453:epidemiology; D030561:Databases, Nucleic Acid; D004196:Disease Outbreaks; D005098:Exotoxins / Q000235:genetics; D005506:Food Contamination; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D012541:Scarlet Fever / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D013290:Streptococcal Infections / Q000188:drug therapy / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000235:genetics* / Q000302:isolation & purification; D014947:Wounds and Injuries / Q000150:complications / Q000382:microbiology
D000900:Anti-Bacterial Agents; D001427:Bacterial Toxins; D005098:Exotoxins; D000667:Ampicillin; D002506:Cephalexin