Shigella flexneri caused an outbreak of dysentery among children in a social welfare center in China from September to October 2015. S. flexneri serotype 2a was identified from stool samples of infected children. Pulsed-field gel electrophoresis (PFGE) analysis demonstrated that the strains from different children were genetically related. Antibiotic susceptibility testing found resistance to multiple antibiotics. Person-to-person transmission was concluded to be the mode of transmission, as no vehicle was identified to have spread the bacteria. Treatment should be guided by antibiotic susceptibility testing given the multi-drug resistant nature of the outbreak strain.

1. Presented by: Andrea Jaramillo C y Juan Pedro Neira

2. Shigella
Introduction
Gram-negative
Genus
Facultative anaerobic
Nonspore-forming
Nonmotile
Spicies
S. dysenteriae: Deadly epidemics in developed countries
S. flexneri: 1/3 of the infections,
especially serotypes X and 2a
S. boydii
S. sonnei: Main cause of infection

3. Antibiotic resistance
¿Immunization
mechanism?
DNA
Modification
Types of antibiotic resistance
Natural
Acquired
Transmitted
Direct
Crossed
Slow
Fast
Mechanisms
Antibiotic
inactivation
Target
modification
Alterations in
permeability
or transport
Antibiotic
expulsion

4. Causes of
antibiotic
resistance

5. Shigella’s resistance 1930 – 1940
Sulfonamides 90 %
Acquisition
of plasmids
Chromosome
mutation
Shigella’s mechanisms
• Production of drug-
inactivating enzymes
• Struggle in the uptake of
the antimicrobial agent
• Less antimicrobial
accumulation
B lactamases
Cefalosporinases
Chloranphenicol
transferases

6. Uncommon in
other animal
species than
humans
Transmission mechanism
Person-to-person
Vehicles
The causative
organism is
frequently found in
water polluted
with human feces
•Diarrhea (often
containingbloodor
mucus)
•Abdominal pain or
cramps
•Fever
•Nausea and vomiting
Shigellosis
Symptoms

7. Objective
To check which organism was
responsible for dysentery
presented in SCWI`s children,
establish it’s transmision
mechanism, and analyze it´s
drug-resistance spectre for
selecting a treatment plan to
avoid it’s spread.

8. Materiales y métodos
Aspectosgenerales
Condado
de Anhui
Condado de
Shenzhen
28 niños
menores de 5
años con
deficiencia
cognitiva
Septiembre 1 a Octubre 27 del 2015, China
o Aglomeración
o Baja ventilación
o Malnutrición
o Convivencia en la
misma habitación pero
en diferentes camas
Ceftriaxona

9. 14 MUESTRAS
FECALES DE
“PACIENTES
CASO”
Muestra
PACIENTES
CASO
DIARREA GRAVE + OTRO SINTOMA
(vómito, fiebre o
eritrocitos/leuccitos en
heces) A PARTIR DEL 23 DE
AGOSTO.
24 MUESTRAS
FECALES DEL
PERSONAL DE
ATENCIÓN
12 MUESTRAS
DE OBJETOS
“POSIBLES
VEHICULOS”

10. qIdentificación de Shigella
Sensititre GNID
32 pruebas bioquímicas con
señal fluorescente para detectar
crecimiento y actividad
enzimática correspondientes a
bacterias Gram -
Serotipificación
Slide
aglutination
Antígeno desconocido
Anticuerpo conocido
Carácterísticas moleculares de
superficie:
Ag K: Cápsula
Ag H: Flagelo
Ag O: Lipopolisacáridos

11. qTest de susceptibilidad
Sistema Vitek 2
64 pozos con sustrato de
prueba individual que
mide hidrólisis,
acidificación,
alcalinización, y
desarrollo en presencia
de sustancias inhibidoras
Pasos:
1. Inoculación
2. Sellado e
incubación
3. Lectura (15 min)
Resultado de
turbiedad
analizados por
Software
Antibióticos contra:
Enterobacterias,
bastones gram – no
fermentadores,
estafilococos,
estreptococos, S.
Pneumoniae,
enterococos.

12. Pfge (electroforesis en gel de campo pulsatil)
Separa fragmentos de DNA con
longitudes mayores a 30 Kb y 2Mb
Gel poroso de Agarosa al 1%
La dirección y la intensidad del campo
se cambia periódicamente (PULSO)
Separación de
moléculas según su
movilidad en un campo
eléctrico según la
carga y el peso Charles CantorDavid C. Schwartz
1984

13. ¿Cómo funciona?

14. Resultados

15. Resultados

16. Resultados

17. Discussion
REFERENCE STATEMENT
DuPont HL, Levine MM,
Hornick RB, Formal SB.
“The onset of symptoms of
these ill persons occurred
after they stayed with Child
A, indicating this outbreak
was caused by secondary
person-to-person spread of
the Shigella, since as few as
10 Shigella organisms can
cause illnes.”

18. Discussion
REFERENCE STATEMENT
Mahoney FJ, Farley TA,
Burbank DF, Leslie NH,
McFarland LM.
“The case patientes were
only found at the rooms
where Child A have stayed
in, consistent with previous
investigation that duration
of diarrhea may have
increased the risk of
infection for other residents
within the same unit.”

19. Discussion
REFERENCE STATEMENT
Lew JF, Swerdlow DL,
Dance ME, Griffin PM,
Bopp CA, Gillenwater
MJ, et al.
“Multiple vehicles were
identified in the outbreak of
shigellosis caused by S.
felxneri in which food(s)
were implicated.”

20. REFERENCE STATEMENT
Varsano I, Eidlitz-
Marcus T, Nussinovitch
M, Elian I.
“… , the in vitro
antibiotics succeptibility
results were stll
guidelines for selecting
appropriate antibiotics
for treatment.”
Discussion

21. Conclusions
SHIGELLA FLEXNERY HAS GREAT CAPACITY FOR
ACQUIRING PLASMID-ENCODED RESISTANCE,
WHICH MAKES SHIGELLOSIS A TRICKY DISEASE
TO TREAT.
DUE TO THE ACQUIRED RESISTANCE, DIFFERENT
SHIGELLA FLEXNERY 2A STRAINS ARE SPREADED
AROUND THE WORLD. SOME OF THEM SHOW A
HIGHER RATE OF DRUG-RESISTANCE THAN OTHERS.

22. Conclusions
S. FLEXNERY WAS SPREADED IN THE SCWI MAINLY
BECAUSE OF PERSON-TO-PERSON CONTACT. THERE
WAS NO PROOF OF THE AGENT USING ANY VEHICLE
FOR TRANSMITTING THE DISEASE.
WHEN IT COMES TO MULTI-DRUG-RESISTANT
BACTERIA STRAINS, THE TREATMENT SHOULD BE
SELECTED ACCORDING TO THE SUSCEPTIBILITY TEST
RESULT.

25. “Lo admirable es que el
hombre siga luchando
y creando belleza, en
medio de un mundo
bárbaro y hostil”
- Ernesto Sábato -