This document summarizes characteristics of the Salmonella genus, including pathogenic species such as Salmonella typhi and Salmonella paratyphia. It describes Salmonella's morphology, optimal growth conditions, virulence factors, mechanisms of pathogenesis, and diseases caused such as gastroenteritis and typhoid fever. The document also outlines methods for laboratory diagnosis of Salmonella including culture-based identification and biochemical testing, as well as treatments including antibiotics and preventive vaccination measures.
The genus Shigella exclusively infects human intestine.
Shigella dysenteriae is the causative agent of bacillary dysentery or shigellosis in humans.
It is a diarrheal illness which is characterized by frequent passage of blood stained mucopurulent stools.
The four important species of the genus Shigella are:
Shigella dysenteriae
Shigella flexneri
Shigella sonnei
Shigella boydii.
The genus Shigella exclusively infects human intestine.
Shigella dysenteriae is the causative agent of bacillary dysentery or shigellosis in humans.
It is a diarrheal illness which is characterized by frequent passage of blood stained mucopurulent stools.
The four important species of the genus Shigella are:
Shigella dysenteriae
Shigella flexneri
Shigella sonnei
Shigella boydii.
prof . dr. ihsan edan alsaimary
department of microbiology - college of medicine - university of basrah - basrah -IRAQ
ihsanalsaimary@gmail.com
00964 7801410838
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
2. SYNOPSIS:
General Characteristics
Pathogenic species
Pathogenicity
Virulence factors
Pathogenesis
Clinical Diseases
Laboratory diagnosis
Colony morphology on
Culture medium
Biochemical Tests
Serology
Treatment and Prevention
3. General Characteristics:
Gram Staining – Gram negative
Shape – Rod Shape(Bacilli)
Motility – Motile
Capsule – Absent
Endospore – Absent
Respiration – Aerobic/Facultative
anaerobic
Optimum Temperature – 34°C to
37°C
Optimum pH – 6.5 to 7.5
Habitat – Intestinal tract of humans and
other animals
The genus “Salmonella” was named after
Daniel Elmer Salmon, a veterinary
pathologist who ran a The United States
Department of Agriculture (USDA)
microorganism research program in the
1800s. Together with Theobald Smith, he
found Salmonella in hogs that succumbed
to the disease known as hog cholera.
4. PATHOGENIC SPECIES OF
Salmonella sp
Salmonella typhi
Salmonella paratyphi
Salmonella choleraesuis
Salmonella typhimurium
Salmonella enteritidis
5. PATHOGENICITY OF Salmonella sp.
DISEASE TRANSMISSION
Ingestion of contaminated food
and water
INCUBATION PERIOD
8 to 14 Days
VIRULENCE FACTORS OF Salmonella sp.
i. Endotoxin
ii. Vi antigen (that increases virulence)
iii. Lipopolysaccharides
iv. Invasion proteins
v. Core polysaccharides
vi. Somatic O antigen
vii.Flagella H antigen
6. PATHOGENESIS OF
Salmonella sp.
After ingestion and passage through
the stomach, Salmonella sp. attach to
the mucosa of the Small intestine.
bacteria remain in Endocytic vacuoles
and replicate Bacteria transported across the Cytoplasm
and released into the Blood
Attachment, engulfment, and replication is
controlled primarily by two large clusters
of genes (pathogenicity island I and II) on
the bacterial chromosome.
7. CLINICAL DISEASES CAUSED BY Salmonella sp.
(i) Gastroenteritis
Gastroenteritis is the most common
form
Symptoms generally appear 6 to 48
hours after the consumption of
contaminated food or water
Fever, Abdominal cramps, Myalgia
and Headache are also common
Colonic involvement can be
demonstrated
Symptoms can persist from 2 to 7
days before spontaneous resolution.
(ii) Bacteremia
All Salmonella species can cause
Bacteremia
Risk For Salmonella bacteremia is
higher in Pediatric and
Immunocompromised patients
Gram negative Bacteremia. However,
Localized infections (e.g.,
Osteomyelitis, Endocarditis and
Arthritis) can occur in as many as 10 %
of patients.
8. (iii) Enteric fever or Typhoid fever
A febrile illness called typhoid
fever.
A milder form of this disease,
referred to as paratyphoid fever,
is produced by salmonella
paratyphi a
Other salmonella serotypes can
rarely produce a similar
syndrome.
Fever that starts low and
increases daily, possibly reaching
as high as 104.9 f (40.5 °c)
(pyrexia)
(iv) Asymptomatic colonization
The strains of Salmonella
responsible for causing Typhoid
and Paratyphoid fevers are
maintained by human
colonization.
Chronic colonization
Chronic colonization with other
species of Salmonella
9. LABORATORY DIAGNOSIS OF Salmonella sp.
Microscopic examination
Gram staining – Pink
coloured Gram negative
rods
Motility test - Motile
10. Colony morphology on culture
medium
Nutrient agar - Colonies are
circular, low convex, smooth,
greyish white and translucent.
Blood agar – Gamma
Hemolysis
MacConkey agar – Non -
Lactose fermenting colonies
Wilson – Blair Bismuth Sulfite
agar – Jet black opaque
colonies with metallic sheen.
Xylose Lysine Deoxycholate
(XLD) agar – Red translucent
opaque colonies with black
centre.
Deoxycholate citrate agar
(DCA) – Pale colonies.
Salmonella – Shigella colonies
(SSA) – Black colonies.
Hektoen Enteric (HE) Agar –
Transparent green colonies.
11. BIOCHEMICAL TESTS
Catalase test - Positive
Oxidase test – Negative
Urease test – Negative
Indole test – Positive
Methyl Red (MR) test – Positive
Voges Proskauer (VP) test – Negative
Citrate utilization test – Positive
SEROLOGY
WIDAL Test (Widely Investigated
Disease Assay Laboratory)
Hydrogen Sulphide Test – Positive
Ornithine Decarboxylase Test –
Positive
Triple Sugar Iron (TSI) Test –
Alkaline slant, Acid butt, Gas
produced and Hydrogen Sulphide
produced.
12. TREATMENT AND PREVENTIVE MEASURES
Antibiotic Therapy
Infections with Salmonella typhi and
Salmonella paratyphi or disseminated
infections with other organisms should
be treated with an effective antibiotics
like
a)Fluoroquinolones (e.g., Ciprofloxacin)
b)Chloramphenicol
c)Trimethoprim – Sulfamethoxazole
d)Broad-spectrum Cephalosporin
13. Vaccination and Preventive
measures
Carriers of Salmonella typhi and
Salmonella paratyphi should be
identified and treated.
Vaccination against Salmonella
typhi can reduce the risk of disease
for travelers into endemic areas.
Most infections can be controlled
by proper preparation of poultry
and eggs (completely cooked) and
avoidance of contamination of
other foods with uncooked poultry
products
