GRAM NEGATIVE COCCI_OG.pptx.pdf document

Gram-positive bacteria are a group of bacteria that have a thick cell wall composed primarily of peptidoglycan. This characteristic cell wall structure allows them to retain the crystal violet stain used in the Gram staining procedure, resulting in a purple or blue appearance under a microscope12.

These bacteria are distinguished from Gram-negative bacteria, which have a thinner peptidoglycan layer and do not retain the crystal violet stain, appearing red or pink instead1. Gram-positive bacteria include many significant genera such as Staphylococcus, Streptococcus, Bacillus, and Clostridium1.

Understanding the characteristics of Gram-positive bacteria is crucial for diagnosing infections and determining appropriate treatments, as these bacteria can cause a variety of diseases but respond differently to antibiotics compared to Gram-negative bacteria

1. GRAM NEGATIVE COCCI
DR O GCILITSHANA

2. GRAM-NEGATIVE COCCI
THE PATHOGENIC NEISSERIAE
The family Neisseriaceae consists of Gram-negative aerobic bacteria in the
genera Neisseria, Moraxella, Kingella, and Acinetobacter.
The genus Neisseria contains two important human pathogens, N.
gonorrhoeae and N. meningitidis.
N. gonorrhoeae causes gonorrhea, and N. meningitidis is a significant a
cause of acute bacterial meningitis.

3. GENERAL CHARACTERISTICS OF THE NEISSERIAE
SPECIES
All species are gram-negative diplococci, each presents a bean-shaped
configuration
All species parasitize the mucous membranes of humans
Fastidious and grow better in 5-10% carbon dioxide
Produce enzyme cytochrome oxidase, Neisseriae are oxidase-positive.
Contain endotoxin in their outer membrane.

4. Neisseria gonorrhoeae
Gonorrhoea is an infection that is spread through sexual contact and gonococci
mostly affect the mucus areas of the body
Usually symptomatic in men but often asymptomatic in women.
Anorectal and pharyngeal infections are important sources as well.
Their resistance to antibodies
Gonococci cause both localized infections and disseminated infections
Gonococci reach these organs via the bloodstream (gonococcal bacteremia).
.

5. GENITOURINARY TRACT INFECTIONS IN THE MALE
Gonococci infect primarily the mucosal surfaces (e.g., the urethra and vagina),
but dissemination occurs.
Symptoms include increasing dysuria, occasional headache and fever.
Uncomplicated gonorrhea in the adult male is an inflammatory and pyogenic
infection of the mucous membranes of the anterior urethra.
Asymptomatic infections occur in males, as well.
The organism may invade the prostate resulting in prostatitis, or extend to the
testicles resulting in orchitis
Rectal infections in homosexual men usually result from anal intercourse and are
more often symptomatic.

6. GENITOURINARY TRACT INFECTIONS IN THE FEMALE
Infection is located primarily in the endocervix, causing a purulent vaginal
discharge and intermenstrual bleeding (cervicitis).
Squamous epithelium, which lines the adult vagina, is not susceptible to infection
by the N. gonorrhoeae.
About 50% of women with cervical infections are asymptomatic.
Cervical involvement may extend through the uterus to the fallopian tubes resulting
in salpingitis, or to the ovaries resulting in ovaritis.

7. As many as 15% of women with uncomplicated cervical infections may
develop pelvic inflammatory disease (PID).
Occasionally, disseminated infections occur.
Symptoms of acute PID infection include chills, fever, bilateral lower
abdominal pain, and rebound tenderness.
Individual PIDs are defined by the site of infection: endometritis (endometrium
of the uterus) and salpingitis (fallopian tubes).
GENITOURINARY TRACT INFECTIONS IN THE FEMALE

8. Factors that contribute to the ascent of bacteria to the upper
genital tract
Insertion of intrauterine devices
Hormonal changes during menstruation.
Retrograde menstruation (The backward flow of menstrual blood up into the
fallopian tubes, thought to be a cause of endometriosis) favoring ascent.
Individual virulence factors of the microorganism associated with pathogenesis

9. EXTRAGENITAL INFECTIONS
Local Infections
Rectal infections (proctitis) with N. gonorrhoeae occur in about one-third of
women with cervical infection.
Pharyngitis
Conjunctivitis- ocular infections by N. gonorrhoeae can have serious
consequences of corneal scarring or perforation.
Ocular infections (ophthalmic neonatorum) occur most commonly in newborns
exposed to infected secretions in the birth canal of an infected mother and can
lead to blindness.

10. Disseminated Gonococcal Infections (DGI)
The most common forms of disseminated infection are:
Arthritis-dermatitis syndrome
Endocarditis and
Meningitis.

11. Laboratory Diagnosis
The diagnosis of urogenital infections depends on Gram staining and culture
of the discharge
Nucleic acid amplification tests are widely used as screening tests.
In women, the use of the Gram stain alone can be difficult to interpret;
Therefore, chocolate agar containing antibiotics that suppress normal flora.
Cultures must also be used in diagnosing suspected pharyngitis or anorectal
infections.

12. Treatment
For uncomplicated infections is a third-generation cephalosporin or a
fluoroquinolone plus an antibiotic (e.g., doxycycline or erythromycin) effective
against possible coinfection with Chlamydia trachomatis.
Sex partners should be referred and treated.
The recommended antimicrobial agents are ceftriaxone, cefixime, ciprofloxacin,
or oflaxacin.

13. NEISSERIA MENINGITIDIS
Neisseria meningitidis, the meningococcus, is identical to Neisseria gonorrhoeae.
However, at the ultrastructural level, N. meningitidis has a prominent
antiphagocytic polysaccharide capsule, an important virulence factor.
 N. meningitidis strains are grouped on the basis of their capsular polysaccharides,
into 12 sero-groups,
some of which are subdivided according to the presence of outer membrane protein
and lipopolysaccharide antigens.

14. Humans are the only natural hosts for meningococci.
The organisms are transmitted by airborne droplets; they colonize the
membranes of the nasopharynx and become part of the transient flora of the
upper respiratory tract.
From the nasopharynx, the organism can enter the bloodstream and spread
to specific sites, such as the meninges or joints, or be disseminated
throughout the body (meningococcemia).

15. Strains of N. meningitidis may be carried as normal flora in the throat, may also be
pathogenic, causing sporadic cases or epidemics of meningitis.
About 5% of people become chronic carriers and serve as a source of infection for
others. The carriage rate can be as high as 35% in people who live in close
quarters (e.g., military recruits);
Meningococcal disease can be divided into three clinical entities:
Nasopharyngitis
Meningoccal septicaemia
Meningococcal meningitis

16. Nasopharyngitis
In the nasopharynx the organisms attach to the epithelial cells.
They may form part of the normal flora without producing symptoms.
Infection of the nasopharynx is usually short-lived.
Colonize the nasopharynx can spread into the blood stream to cause
septicaemia or meningitis

17. Meningococcal septicaemia
Can be accompanied with high fever, arthritis, blockades of small vessels
and a rash.
A serious development is a fulminating sepsis, which produce haemorrhagic
necrosis of the cortex of both adrenal glands (adrenal apoplexy).
The physiological effects of adrenal insufficiency lead to rapid collapse and
death.
Fulminant meningococcemia with high fever and haemorrhagic rash lead to
disseminated intravascular coagulation and circulatory collapse (Waterhouse-
Friderichsen syndrome).

18. Meningococcal Meningitis
The term meningitis refers to pathology in the Meninges of the brain or spinal cord.
Meninges are any of the three membranes that envelope the brain and spinal
cord.
Bacterial causes include Haemophilus influenzae, Escherichia coli, Streptococcus
pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, and Neisseria
meningitidis.
Like its relative N. gonorrhoeae, the organism tends to occur intracellularly in the
cytoplasm of neutrophils, which are attracted to the site of inflammation in the
mininges, so this type of infection is called pyogenic (pus-forming).

19. Pathogenesis
Infection with N. meningitidis has two presentations, meningococcemia, characterized by skin
lesions, and acute bacterial meningitis.
More common in infants and children (70% <5yrs, most susceptible < 1yr).
Acute bacterial meningitis occurs in epidemics in closed environments like boarding schools and
military barracks.
The Meningococci are spread by direct contact with nose or throat discharges of an infected
person.
The symptoms are high fever, headache, vomiting, stiff neck and rash. 10-15% of people die in
spite of treatment with antibiotics.
Fulminant disease (with or without meningitis) is characterized by multisystem involvement and
high mortality.

20. The mildest form of disease is a transient bacteremic illness characterized by a
fever and malaise; symptoms resolve spontaneously in 1 to 2 days.
The most serious form is the Fulminant disease complicated by meningitis.
The manifestations of meningococcal meningitis are similar to acute bacterial
meningitis caused by organisms such as Streptococcus pneumoniae,
Haemophillus influenzae, and E. coli. Chills, fever, malaise, and headache are the
usual manifestations of infection.
Signs of meningeal inflammation are also present. The onset of meningococcal
meningitis may be abrupt or insidious.
Meningococci are also implicated in infections of the eye, conjunctivitis &
papillitis.

21. LABORATORY DIAGNOSIS
Diagnosis of meningococcal meningitis can be made if gram-negative cocci
are seen in a smear of spinal fluid
The organism grows best on chocolate agar incubated at 37°C in a 5% CO
2

atmosphere.
The differentiation between N. meningitidis and N. gonorrhoeae is made on
the basis of sugar fermentation: meningococci ferment maltose
Immunofluorescence can also be used to identify these species

22. Treatment
Penicillin is the drug of choice to treat meningococcemia and meningococcal
meningitis.
Either chloramphenicol or a third-generation cephalosporin such as cefotaxime or
ceftriaxone is used in persons allergic to penicillin.
Cephalosporin’s such as cefotaxime are drugs of choice for children with
meningitis.
Vaccination exists in the U.S.

23. GRAM NEGATIVE RODS
DR O GCILITSHANA

24. HAEMOPHILUS INFLUENZAE
Formerly called Pfeiffer’s bacillus or Bacillus influenzae, is a non-motile
Gram-negative coccobacillus first described in 1892 by Richard Pfeiffer
during an influenza pandemic.
It is generally aerobic, but can grow as a facultative anaerobe.
H. influenzae was mistakenly considered to be the cause of influenza until
1933
In 1930, two major categories of H. influenzae were defined:
The unencapsulated strains and the encapsulated strains.

25. DISEASES
Most strains of H. influenzae are opportunistic pathogens
There are six generally recognized types of H. influenzae: a, b, c, d, e & f
Naturally-acquired disease caused by H. influenzae seems to occur in humans only.
In infants and young children, H. influenzae type b (Hib) causes bacteraemia,
pneumonia, and acute bacterial meningitis. Occasionally, it causes cellulitis,
osteomyelitis, epiglottitis, and joint infection and lower respiratory tract infections in
infants and children in developing countries where vaccine is not widely used.
Unencapsulated H. influenzae (non-B type) causes ear (otitis media) and eye
(conjunctivitis) infections and sinusitis in children, and is associated with pneumonia.

26. Culture
Bacterial culture is preferably chocolate agar, plate with added X & V factors at
37
0
C in an enriched CO
2
incubator.
Colonies of H. influenzae appear as convex, smooth, pale, grey or transparent
colonies. Gram-stained and microscopic observation of a specimen of H.
influenzae will show Gram-negative, coccobacilli, with no specific arrangement.
The cultured organism can be further characterized using Catalase and oxidase
tests, both of which should be positive.
Further serological is necessary to distinguish the capsular polysaccharide and
differentiate between H. influenzae b and non-encapsulated species.

27. Satelitism to Staphylococcus aureus. On an agar-blood plate Haemophilus
influenzae grows near the strips of Staphylococcus aureus,

Latex Particle Agglutination Test (LAT)
Latex particle agglutination Test (LAT) is a more sensitive method to detect H.
influenzae than culture.
It also has the added benefit of being much quicker than culture methods.
However, antibiotic sensitivity is not possible with LAT, so a parallel culture is
necessary.

28. TREATMENT
Haemophilus influenzae produces beta lactamases, and it is also able to
modify its penicillin binding protein.
In severe cases, cefotaxim, and ceftriaxone are the elected antibiotics,
delivered directly into the bloodstream, and
For the less severe cases association of ampicilin and sulbactam,
cephalosporin of the second and third generation, or fluoroquinolone.

29. FOOD-BORNE DISEASES CAUSED BY GRAM NEGATIVE-
ENTERIC BACTERIA
GENERAL PROPERTIES OF GRAM-NEGATIVE BACTERIA
They are mostly members of the Enterobacteriaceae family but members of
other taxonomical groups (e.g. Vibrionaceae) are also considered in this
category.
All members are facultative anaerobes.
Most can be cultivated on ordinary media and stained with aniline dyes.
Most species are active fermenters of glucose and other carbohydrates.

30. Continue…
There are motile and non-motile species.
Pili are found on the cell surface; the sex pili are important in the transfer of
antibiotic resistant factors.
Many species are classified by their cell envelope Antigens-O, K and H.
The O or somatic antigen is the O-specific polysaccharide of the LPS
component of the cell wall, which protects some species against host
resistance factors.

31. Continue…
The capsular polysaccharide of the Enterobacteriaceae is referred to as the
K antigen. The k polysaccharide also provides a barrier to phagocytosis
because of its ability to resist activation of the complement pathway.
Flagella proteins are referred to as H antigens. They are responsible for
motility.
[Antigenic composition: Important for epidemiological reasons
 * O antigen: terminal sugar of the lipopolysaccharide (LPS)
 * K antigen: capsular polysaccharide antigen
 * H antigen: flagella antigen]

32. TYPES OF INFECTIONS: These organisms can cause either
intestinal or extra intestinal infections.
1.Intestinal:
A. Non-inflammatory enteritis
Organisms remain in the intestinal lumen; pathology mostly due to toxin
production; usually characterized by watery diarrhoea; no faecal leukocytes
in stool samples.
*Examples: Vibrio cholerae
Enterotoxigenic E. coli (ETEC)
Vibrio parahaemolyticus

33. B. Inflammatory enteritis
Organisms enter the intestinal epithelial cells; pathology mostly due to
inflammatory response or destruction of the intestinal epithelium: often
characterized by dysentery polymorphonuclear leukocytes in stool samples.
Examples: - Shigella
- Enteroinvasive (EIEC)
- Enteropathogenic (EPEC)
- Enterohemorrhagic (EHEC)
- Salmonella sp. (other than S. typhi)
- Campylobacter jejuni

34. C. Enteric fever/Typhoid fever
Organisms penetrate through the intestinal epithelium to deeper tissues
involving the reticuloendothelial system; mononuclear leukocytes in stool
samples.
*Example: -Salmonella typhi

35. PREDISPOSTNG FACTORS:
For Intestinal infections:
Age (e.g. children are more susceptible to certain E. coli infections)
Impaired intestinal motility
Achlorhydria
Antibiotic usage which alters normal flora
Immunocompromising factors

36. Escherichia coli INFECTIONS
(Escherichia coli) E. coli GASTROENTERITIS SYNDROME
Although sporadic reports of Escherichia coli related gastroenteritis of food
origin appeared prior to the 1970's, it was the 1971 outbreak in the USA
traced to imported cheese that focused attention on this organism as a food-
borne pathogen.
CAUSATIVE AGENT: Escherichia coli

37. Intestinal infections:
Classification based on the intestinal pathology:
EPEC (Enteropathogenic)
ETEC (Enterotoxigenic)
EHEC (Enterohemorrhagic)
EIEC (Enteroinvasive)
EAggEC (Enteroaggregative)

38. Pathogenesis and Clinical Manifestations
ETEC:
Acute secretory diarrhoea ("traveller's diarrhoea") mostly due to the action of
either a thermo-labile cholerae like toxin (LT) or a thermostable toxin (ST).
Transmitted by drinking water contaminated with human sewage and
infected food handlers.
LT toxin: Heat labile, similar to cholerae toxin.
ST toxin: Heat stable; binds and activates guanylate-cyclase which also
serves as receptor, increases the level of guanylate-cyclase in the cell and
alters host cell electrolyte balance.

39. EPEC:
One of the principal causes of infant diarrhoea in the developing world;
characteristic localized adherence to the intestinal epithelium.
Watery diarrhoea is associated with the attachment to, and physical alteration
of the integrity of the intestine.
Bloody-diarrhoea is associated with attachment and an acute tissue-
destructive process, perhaps caused by a toxin similar to that of Shigella
dysenteriae, also called verotoxin.

40. Continue…
In most of these strains the shiga-like toxin is cell-associated rather than
excreted.
Several virulence determinants mediate these events: lntimin (a surface
protein), bundling forming pilus (BFP), and contain a type lll secretion
pathway.

41. EHEC:
EHEC is a dangerous pathogenic type of E. coli first identified in USA in 1982
and has emerged as a cause of food-borne illness, is designated 0157: H7.
Other strains like 026:H11 and 0111:H8 have also been found.
EHEC strains produce toxins that have effects similar to those produced by
bacteria of the Shigella genus.
Causes a bloody copious diarrhoea and haemolytic uremic syndrome.
Part of the pathogenicity due to the production of large amounts of Shiga
toxin.

42. EIEC:
EIEC is caused by pathogenic Enteroinvasive strains of E. coli and are
responsible for a form of bacillary dysentery.
The EIEC strains responsible for this syndrome Shigella species.
Causes disease identical to shigellosis, virulence factors identical to
Shigella's.

43. EAggEC:
Enteroaggregative Escherichia coli (EAEC), an increasingly recognized cause
of diarrhoea in children in developing countries,
has been particularly associated with persistent diarrhoea (more than 14
days), a major cause of illness and death.
Recent outbreaks implicate EAEC as a cause of food-borne iIIness in
industrialized countries.

44. Continue…
The pathogenesis of EAEC infection is not well understood,
but a model can be proposed in which EAEC adhere to the
intestinal mucosa and elaborate enterotoxins and cytotoxins,
which result in secretory diarrhoea and mucosal damage.
EAEC's ability to stimulate the release of inflammatory mediators
may also play a role in intestinal illness.