This document discusses four gram-negative rod bacteria associated with respiratory disease: Haemophilus influenzae, Bordetella pertussis, Legionella pneumophila, and Acinetobacter baumannii. It provides details on the transmission, pathogenesis, symptoms, and treatment for each bacterium. H. influenzae and B. pertussis primarily affect humans while L. pneumophila is found in water sources. A. baumannii can be found in both environmental water and as a nosocomial infection in humans with weakened immune systems. The standard treatments involve various antibiotics, though drug resistance is a concern for some bacteria like A. baumannii.

1. GRAM NEGATIVE ROD
BACTERIA
(RESPIRATORY
DISEASE)
Maaz Shah

2. Introduction
■ There are four medically important gram-negative rods typically
associated with the respiratory tract, namely, Haemophilus
influenzae, Bordetella pertussis, Legionella pneumophila, and
Acinetobacter baumannii. H. influenzae and B. pertussis are
found only in humans, whereas L. pneumophila is found primarily
in environmental water sources. A. baumannii is found in
environmental water sources but also colonizes the skin and
upper respiratory tract.

3. 1- Haemophilus influenzae
■ Conditions
■ Haemophilus influenzae type b (Hib) is a life-threatening infection that can
lead to serious illness, especially in children. Symptoms include severe
headache, stiff neck, convulsions or seizures, severe drowsiness, difficulty
waking up, loss of consciousness or difficulty with breathing.

4. Precautions
■ Precautions
■ Prevention. Staying up to date with recommended vaccines and maintaining
healthy habits, like washing hands often and not having close contact with
people who are sick, help prevent disease caused by Haemophilus influenzae.

5. Diagnosis & complications
■ Diagnosis
■ Doctors usually diagnose Haemophilus influenzae infection with one or more
laboratory tests. The most common testing methods use a sample of blood or
spinal fluid.
■ Complications
■ Even with appropriate treatment, some H. influenzae infections can result in long-
term problems or death. For example, bloodstream infections can result in loss of
limbs. Meningitis can cause brain damage or hearing loss.
■ Complications are rare and typically not severe for bronchitis and ear infections
caused by H. influenzae.

6. Treatment
■ Treatment
■ People diagnosed with H. influenzae disease take antibiotics to treat the infection.
Depending on how serious the infection is, people with H. influenzae disease may need care
in a hospital. Other treatments may include:
■
■ Breathing support
■ Medication to treat low blood pressure
■ Wound care for parts of the body with damaged skin
■ When H. influenzae cause milder infections, like bronchitis or ear infections, doctors may
give antibiotics to prevent complications.

7. Medicine
■ An antibiotic, such as ceftriaxone, cefotaxime, or cefuroxime, is given. Other
infections due to Haemophilus influenzae are treated with various antibiotics
given by mouth. They include amoxicillin/clavulanate, azithromycin,
cephalosporins.

8. 2- Bordetella pertussis
Bordetella pertussis is a Gram-negative, aerobic, pathogenic,
encapsulated. The causative agent of pertussis or whooping cough.
B. pertussis is motile and expresses a flagellum-like structure.
Its virulence factors include pertussis toxin, adenylate cyclase
toxin, filamentous hæmagglutinin, pertactin, fimbria, and tracheal
cytotoxin.

9. Transmission & Host
■ The bacterium is spread by airborne droplets; its incubation
period is 7–10 days on average (range 6–20 days). Humans are the
only known reservoir for B. pertussis.
■ B. pertussis infects its host by colonizing lung epithelial cells.
The bacterium contains a surface protein, filamentous
haemagglutinin adhesin, which binds to the sulfatides found on
cilia of epithelial cells. Other adhesins are fimbriae and
petractin.

10. ■ Once anchored, the bacterium produces tracheal cytotoxin, which stops the
cilia from beating. This prevents the cilia from clearing debris from the lungs,
so the body responds by sending the host into a coughing fit. These coughs
expel some bacteria into the air, which can then infect other hosts.

11. Disease
■ Pertussis is also known as whooping cough. It is a highly
infectious bacterial disease involving the respiratory tract. It is
caused by a bacterium (Bordetella pertussis or Bordetella
parapertussis ) that is found in the mouth, nose and throat of an
infected person.
■ Pertussis is an infection of the respiratory system characterized
by a “whooping” sound when the person breathes in. In the US, it
killed between 10,000 and 20,000 people per year before a
vaccine was available.

12. ■ B. pertussis has the ability to inhibit the function of the host’s
immune system. The toxin, known as pertussis toxin (or PTx),
inhibits G protein coupling that regulates an adenylate cyclase-
mediated conversion of ATP to cyclic AMP. The end result is that
phagocytes convert too much ATP to cAMP, causing disturbances
in cellular signaling mechanisms, and preventing phagocytes from
correctly responding to the infection.

13. ■ It limits neutrophil migration to the lungs. It also decreases the
function of tissue-resident macrophages, which are responsible
for some bacterial clearance.

14. Treatment
■ The introduction of vaccination in England in 1957, the rate of
pertussis infection has dropped by 97%.
■ Whooping cough is treated by macrolides, for example
erythromycin. The therapy is most effective when started during
the incubation period or the catarrhal period.

15. 3- Legionella pneumophila
■ Legionella pneumophila is a thin, aerobic, pleomorphic,
flagellated, non-spore-forming.
■ L. pneumophila is the primary human pathogenic bacterium in
this group and is the causative agent of Legionnaires’ disease,
also known as legionellosis.

16. Survival of bacteria
■ In nature, L. pneumophila infects freshwater and soil amoebae of
the genera Acanthamoeba and Naegleria.
■ L. pneumophila is a facultative intracellular parasite that can
invade and replicate inside amoebae in the environment,
especially species of the genera Acanthamoeba and Naegleria,
which can thus serve as a reservoir for L. pneumophila. These
hosts also provide protection from environmental stresses, such
as chlorination.

17. Pathogenesis
■ In humans, L. pneumophila invades and replicates inside
macrophages. The internalization of the bacteria can be
enhanced by the presence of antibody and complement, but is
not absolutely required. Internalization of the bacteria appears
to occur through phagocytosis.Once internalized, the bacteria
surround themselves in a membrane-bound vacuole that does not
fuse with lysosomes that would otherwise degrade the bacteria.
In this protected compartment, the bacteria multiply.

18. Disease
■ Legionnaires’ (LEE-juh-nares) disease is a serious type of pneumonia (lung
infection) caused by Legionella (LEE-juh-nell-a) bacteria. People can get sick
when they breathe in small droplets of water or accidently swallow water
containing Legionella into the lungs.
■ Legionnaires’ disease usually develops two to 10 days after exposure to
legionella bacteria. It frequently begins with the following signs and
symptoms:
■ Headache
■ Muscle aches
■ Fever that may be 104 F (40 C) or higher

19. ■ By the second or third day, you’ll develop other signs and
symptoms that can include:
■ Cough, which might bring up mucus and sometimes blood
■ Shortness of breath
■ Chest pain
■ Gastrointestinal symptoms, such as nausea, vomiting and
diarrhea
■ Confusion or other mental changes

20. Treatment
■ Macrolides (azithromycin or clarithromycin) or fluoroquinolones
(levofloxacin or moxifloxacin) are the standard treatment for
Legionella pneumonia in humans.

21. 4- Acinetobacter baumannii
■ Acinetobacter baumannii is a typically short, almost round, rod-
shaped Gram-negative bacterium. It can be an opportunistic
pathogen in humans, affecting people with compromised immune
systems, and is becoming increasingly important as a hospital-
derived (nosocomial) infection.
■ Occasionally it has been found in environmental soil and water
samples,[4] its natural habitat is still not known.

22. Sign & symptoms
■ A. baumannii is an opportunistic pathogen with a range of different diseases,
each with their own symptoms. Some possible types of A. baumannii infections
include:[citation needed]
■ Pneumonia
■ Bloodstream infections
■ Meningitis
■ Wound and surgical site infections, including necrotizing fasciitis
■ Urinary tract infections

23. ■ Symptoms of A. baumannii infections in turn range from fevers
and chills, rash, confusion and/or altered mental states, pain or
burning sensations when urinating, strong urge to urinate
frequently, sensitivity to bright light, nausea (with or without
vomiting), muscle and chest pains, breathing problems, and
cough (with or without yellow, green, or bloody mucus)

24. Treatment
■ An A. baumannii infection was recently treated using phage therapy. Phages are viruses that
attack bacteria, and have also been demonstrated to resensitize A. baumannii to antibiotics
it normally resists.
■ Medications to which Acinetobacter is usually sensitive include the following:
■ Meropenem.
■ Colistin.
■ Polymyxin B.
■ Amikacin.
■ Rifampin.
■ Minocycline.
■ Tigecycline.