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Pseudomonas: -
The term pseudomonads describes a large group of aerobes non- fermentative, Gram –Ve bacilli belonging to over 200 species that were originally contained within the genus pseudomonas.
Most are saprophytes found widely in soil, water and other moist environments. Pathogenic member is Ps.aeruginosa.
Ps.aeruginosa:- about (4–12)% of humans carry P.aeruginosa as part of normal faecal flora.

Morphology:-
It is Gram -Ve bacillus about (1.5– 3× 0.5)µm, motile with usually one polar flagellum , non- spore forming , non- capsulate.
Cultural characters:-
It is strict aerobic, growing on simple nutrient media. The growth range (5– 42)˚C, Optimum 37˚c
a) Broth:- Uniform turbidity and surface pellicle. Bluish green pigment due to formation of pyocyanin pigment.
b) Nutrient agar:- It produces large, opaque, low convex, irregular colonies. It gives fruity odour. Most strains produce diffusible pigments which color the colonies slightly and color the surrounding medium with Bluish green due to pyocoyanin, and the yellow – green due to pyoverdin; additional pigment include pyorubrin (red) and melanin (brown). Some strains may be non- pigmented.
c) Blood agar:- It shows beta hemolysis.
d) MacConkey agar:- It produces pale non lactose fermenting colonies.

Biochemical reaction:-
• Glucose is used oxidatively forming acid only.
• Catalase and oxidase are positive.
• Indole and H2S not produced.
• VP and MR are negative.
• Citrate is positive.

Typing for epidemiological purposes or to investigate relationships between isolates, It is include pyocin typing , serotyping and phage typing.

Resistance:-
Heating at 56˚c kills the organisms. It is resistant to antiseptic and disinfectant. It is resistant to most of antibiotics.



Toxin:-
Most strains produce exotoxin A, it's mechanism of action similar to diphtheria toxin and a variety of cytotoxic substance include proteases, phospholipases, an alginate like exopolysaccharide is responsible for the mucoid phenotype.

Pathogenesis:-
Ps.aeruginosa can infect almost any external site or organ. In hospital patients, infections are more common, more severe, occur as in catheter – related urinary tract infection, infected ulcers, bed sores , burns and eye infection. Ps.aeruginosa cause septicaemia and necrotizing pneumonia.

Laboratory diagnosis:-
Isolation of Ps.aeruginosa with selective Cetrimide broth or Cetrimide agar in addition to blood agar and macConkey agar. Ps.aeruginosa can be rapidly identified by it's green blue pigment on solid media, by it's fruity odour. It's positive oxidase test.
Formal identification can be made with a multi-test system such as API 20S. (specimens: pus, wound swab , urine, sputum , CSF or blood).

Treatment:-
With a combination of an aminoglycoside such as gentamicin or tobramycin with β – lactam such as azolcillin, ticarcillin and ceftazidime.
Passive vaccination may be useful for the treatment of septicaemia and burn infection due to Ps.aeraginosa.

Note:-
Antigenic structure include (O) antigens 19 distinct, group–specific O antigens heat stable. (H) antigens (two–heat labile H antigens).

Genus: Proteus:
The organisms are free-living saprophytes in soil, vegetation , water and sewage and are found in the intestine in many healthy persons.

Morphology:-
Gram- ve rods about 1-3µm x 0,6µm, varying in length from short coccobacilli to long filaments. Most strains are highly motile and show swarming motility. It is non- spore forming and non- capsulated.

Cultural characters:-
It is aerobic and facultative anaerobic. Proteus organisms are first recognized by their fishy smell. A notable property of pr.vulgaris and pr.mirabilis strains is the ability to swarm on solid media (Nutrient agar, blood agar) at 37˚c after 18 hr. incubation.
Swarming:- it is the bacterial growth spreads progressively from the edge of the colony and covers the whole surface of the medium. Swarming can be suppressed by 6% agar in the media or sodium a zide or Boric acid.
On Broth it shows uniform, moderate turbidity. There is powdery deposit and ammonical odor.
On MacConkey agar, swarming does not occur and the colonies are pale (non- lactose fermenting).

Biochemical reactions:-
It forms acid and gas from glucose. It's ability to hydrolyse urea rapidly (within a few hours) and it's ability to deaminate phenyalanine to phenylpyruvic acid (PPA test). Pr.mirabilis is Indole –ve while Pr.Vulgaris is Indole +ve. The strains are MR +ve and VP -ve. Viriable in citrate, (+ve) in gelatin liquefaction, (+ve) in H2s.


Antigenic structure:-
Strains are produced somatic(O) antigens and Flagellar(H) antigens. Certain types of Proteus are agglutinated by the serum of patients with typhus fever, because of common antigenic factor (O)antigen of Proteus and a somatic antigen of Rickettsiae. This reaction, the weil–Felix reaction, is used as a diagnostic test.

Pathogenecity:-
It may cause urinary tract infection and may provoke the formation of stones in the urinary tract. Infection of wound, ear or respiratory tract.

Laboratory diagnosis:-
On culture of material (urine, pus, sputum), we find swarming type of growth on blood agar. It can be further identified by biochemical tests.

Treatment:-
Most strains of Pr.mirabilis are sensitive to benzyl penicillin, ampicillin. Pr. Vulgaris strains are resistant to penicillin. All strains are resistant to polymyxins.
Urinary tract infection Pr.mirabilis respond to ampicillin or trimethoprim. Serious infection with other Proteus strains can be treated with an aminoglycoside or cefotaxime.

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Medical bacteriology
Introduction
Medical bacteriology:-
It's the study of the causative agents (bacteria) of infectious diseases of man, pathogenesis , Various methods of diagnosis, treatment and prevention.
In other words, it deals with pathogens, laboratory diagnosis, treatment and control of infections.

Bacteria in health and disease:
Skin, alimentary tract other mucous membranes are continually contaminated by microorganisms from the environment.
Based on their relationship they can be divided into:
• Saprophytes are free-living microbes that live on dead or decaying organic matter. They are found in soil and water. They are generally incapable of multiplying on living tissues. However, sometimes when host resistance is lowered, some saprophytes like Bacillus subtilis may cause infection.
• Parasites are the microorganisms that can enter and multiply in hosts.
They are of two types:-
• Micro-parasites which include viruses, bacteria, fungi and protozoa
• Macro-parasites which include helminthes.

Pathogens:
Pathogens are the microorganisms which are capable of producing disease in man and animals.
They are of two types:
• Opportunistic: rarely cause disease in individuals with intact immunological and anatomical defenses. In immunocompromised hosts these bacteria are able to cause disease. For example, Escherichia coli is normally carried in human intestine. If they enter in to urinary tract they lead to urinary tract infection.
• Primary pathogens: are the organisms which are capable of causing disease in previously healthy individuals with intact immunity.

Commensals: (organisms of normal flora or normal microbiota)
are the microorganisms which live in complete harmony with the host without causing any damage to it.
For first nine months of life, the human foetus is in a sterile environment protected from microbes. However, pathogens such as Toxoplasma gondii , rubella virus, human immunodeficiency virus, malaria parasites are able to infect the fetus through the placenta. At the time of birth when the newborn is confronted with the mother's vaginal microbes and environmental organisms, so the state of fetus sterility comes to an abrupt end. Also the infant's skin surface is initially colonized and then the or pharynx, gastrointestinal tract and other mucosal surfaces rapidly become populated.
The normal microbiota maintain a protected environment that prevents colonization with pathogenic organisms.
The organisms differ at different parts of the body. This is due to local environmental factors which tend to select certain species.
These organisms obtain their nutrition from the secretions and waste products of the body. The normal microbial flora may be divided in to:
• Resident flora:
It consists of organisms which are regularly present in a given area at a given and when disturbed, it promptly reestablishes itself. For example, E.coli in the intestine of man and many other animal species in all parts of the world. Similarly, α-haemolytic streptococci and lactobacilli are present in nasopharynx.
Role of resident flora
A. Beneficial role
1- They prevent or suppress the colonization of the body by pathogen by bacterial interference.
2- Members of the resident flora in the intestinal tract synthesize vitamins, especially vitamin K several B vitamins.
3- Antibodies produced in response to commensals cross-react with pathogens thus raising the overall immune status of the host.
4- Bacteriocins produced by some organisms of normal flora have harmful effect on pathogens.
5- The endotoxins liberated by them may help the defense mechanisms of the body by triggering the complement pathway.
B. Disease production:
1- Most members of the normal micro biota are generally non-pathogenic some may assume a pathogenic role when resistance of the host is lowered as in cases of leukaemia, diabetes and AIDS and in patients on immunosuppressive drugs ( opportunistic pathogens).
2- Streptococcus mutans may cause dental caries.
3- Peritonitis may follow the accidental introduction of gut organisms in to the peritoneum during operation on the bowel.
4- Peaicillinase producing organisms can aggravate infection by interference with therapy.
5- Use of broad- spectrum antibiotics affects the gut microbiota by inhibiting or killing sensitive bacteria allowing overproduction of resistant bacteria as well as pathogenic bacteria.
6- Isolation of normal flora may cause confusion in the diagnosis.

• Transient flora:
It consists of both pathogens and non pathogens that inhabit the skin or mucous membrane for a limited period. If the resident flora is intact, there is very little significance of the transient flora. If the normal flora is disturbed, the transient flora may colonize, proliferate and produce disease. Pathogens such as the pneumococcus, meningococcus and Haemophilus influenzac may found among nasopharyngeal microbiota of man from time to time.

Normal flora of the skin:-
Skin is the largest organ in the body, having an area of about 1.75 meter2. It contains a rich resident flora, 102-104 organisms per Cm2. There are found at the surface but also in the depths of the skin, in loose squamous layers and in sebaceous follicles.
Important factors which help in elimination of non-resident microorganisms from the skin include low pH, fatty acids in sebaceous secretions and presence of lysozyme. External auditory canal may also carry pseudomonas aeruginosa and streptococcus pneumoniae.

Normal flora in the mouth:
The normal microbial flora of the oral cavity is complex and consists of a large number of species of bacteria, In addition to Mycoplasma, fungi and protozoa. The oral cavity may be considered as an ideal microbial incubator. It possesses an abundance of moisture, an excellent supply of various types of foods and differences in oxygen tension. Many aerobic, facultative and anaerobic organisms find conditions favorable for growth.
At birth the mouth of the newborn is usually sterile. Within a few hours of the birth streptococci, of which Strep. salivarius is dominant. During the first month of life other species of Streptococci , Staphylococci, Lactobacilli, Neisseriae, Actinomyces. By the first year of life, the oral microbial flora of the child resemble that of adult.

Normal flora of the nares and nasopharynx
Relatively small number of organisms are present in the nares with Staphylococcus including Staph. aureus and coagulase-negative species, Corynebacterium, Peptostreptococcus and Fusobacterium species.
The microbial population of nasopharynx is more complex with a predominance of Streptococci and Neisseria species.

Normal flora of the oro pharynx
The oropharynx contains a mixture of Streptococci. A number of species of the viridans group can be isolated, including Strep.mitis, Strep.mutans, Strep.milleri and Strep.salivarius. In addition to diphtheroids.

Normal flora of the gastrointestinal tract:
The gastrointestinal tract of the fetus is sterile but becomes contaminate with microorganisms either during or shortly after birth.
In breast-fed infants, the intestine contains anaerobic bacilli of the genus Bifidobacterium (particularly B.bifidum). Coliforms, Enterococci, Staphylococci and Lactobacilli may occur in some of them.
In bottle-fed infants, the intestine contains Leptotrichia, anaerobic Lactobacilli and aerobic and anaerobic spore- bearing organisms.
The normal flora of the stomach comprises of Lactobacillus and Enterococcus spp., also these bacteria predominate in the duodenum and upper ileum, but in lower ileum and caccum , the flora resembles the flora present in the large intestine and faeces.

Normal flora of the genitourinary tract
The kidneys, bladder and fallopian tubes are normally free of microorganism. The urethra is colonized in it’s outermost segment by those organisms found on the skin.
During child-bearing years, the vagina is colonized with Lactobacilli and anaerobic G-ve rods and G+ve cocci.

Normal flora of the conjuctiva:
The conjuctival flora is normally held in check by fhishing action of tears and due to presence of lysozyme in it. The normal flora are Corynebacterium spp, Staph epidermidis, nonhaemolytic Streptococci, Neisseriae.

Infection:
• It's a process of microbial invasion of the body.
• These infective diseases that are readily communicable from person to person are called " infectious".
Sources of infection
Infections may be endogenous, due to organisms of the normal flora, and exogenous, due to organisms derived from a source outside the body.
 Endogenous infections:
There are also referred to as autoinfections Organisms of normal flora are usually non-pathogenic but occasionally they may lead to infection. e.g. E coli the normal flora of intestines, may cause urinary tract infection.
 Exogenous infections:
Most of the infections are exogenous in origin. The sources of exogenous infections are as under:
1. Human and carriers
2. Animal
3. Insects
4. Environment

1. Human and carriers
The commonest source of human infection is man himself who may be a patient or a carrier. Infection due to some organisms are acquired mainly or exclusively from ill persons e.g. AIDS, Ssyphilis, tuberculosis, hepatitis B, influenza, etc.
A carrier is a person who harbours the pathogenic organisms without suffering from it. There are several types of carriers.
 Healthy carr:
One who harbours the pathogen but never suffered from the disease caused by it.
 Convalescent carr:
One who has recovered from the disease but continues to harbour the pathogen on his body.
 Temporary carr:
When carrier state lasts for less than six months.
 Chromic carr:
When carrier state lasts for years or may be for the life of the patient.
 Paradoxical carr:
Who acquires the organisms from another carrier.
 Contact carr:
Who acquires the organisms from a patient.

2. Animal
Certain pathogens are capable of causing infection in both man and animal. Therefore, animal may act as a source of infection of such organisms. The infection may be acquired by contact with the animal bite and ingestion of milk or meat. Infection in animal may be asymptomatic and these animals may serve as reservoir for human infection.
Infectious diseases transmitted from animals to man are known as zoo noses. For example:
• Bacterial : Bovine tuberculosis, anthrax, plague
• Viral : Rabies
• Protozoal: Leishmaniasis
• Fungal: Microsporum canis

3. Insects
Blood- sucking insects such as mosquitoes, ticks, files, lice act as a source of a number of human and animal infections.
Insects transmitting pathogens are known as "vectors". They are two types:
• Mechanical vectors:
Which carry the organisms on their legs, wings and body and transmit them to eatables which then act as a source of infection e.g. transmission of Salmonellosis through food by domestic fly.
• Biological vectors:
Are those in whom the pathogens multiply or undergo development changes e.g. malaria parasite in female anopheles mosquito.

4. Environment
This includes soil, water and food. A few infective diseases of man are caused by saprophytic microbes derived from soil. e.g. spores of tetanus and gas gangrene bacilli remain viable in the soil for several decades and serve as a source of infection. The normal habitat of these organisms is the human and animal intestines and they enter the soil through their faeces .
Water contaminated with Salmonella, Vibrio cholerae, Hepatitis A , virus, Polio virus.
Contaminated food acts as a source of organisms causing food poisoning, gastroenteritis, diarrhea and dysentery.

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