Chapter 20

Neisseria

Only genus of G- cocci that regularly causes disease in humans, non motile, aerobic, arranged as diplococci (coffee bean shaped), oxidase positive, pathogenic strains have fimbriae, capsules, and variable cell wall antigens composed of lipooligosaccharide. Fastidious in nature, grows on chocolate agar or Thayer-Martin medium. Two species pathogenic to humans, N. gonorrhoeae, and N. meningitidis

Neisseria gonorrohoeae

Causes gonorrhea, gonococci adhere to the genital, urinary, and digestive tract via fimbriae and capsules. Protected by secreting a protease enzyme that cleaves lgA.

Gonorrhea

Causes painful urination and pus filled discharge in men, often asymptomatic in women but can trigger pelvic inflammatory disease, proctitis, gingivitis, pharyngitis, infection of children can occur during childbirth

Neisseria gonorrohoeae

Diagnosed by genetic probes, G- diplococci in pus, can be cultured on Thayer-Martin agar

Neisseria gonorrohoeae

Treated by broad spectrum drugs like cephalosporins, long term immunity cannot develop due to variable strains

Neisseria gonorrohoeae

Prevention methods include abstinence and monogamy

Neisseria meningitidis

13 antigenic strains, ABC and W135 are the most common, can survive in neutrophils and macrophages, polysaccharide capsule resist lytic enzymes of phagocytes, causes blebbing

Blebbing

a process of shedding outer membrane

Neisseria meningitidis

Life threatening when bacteria invade blood or CSF. Most common cause of meningitis in individuals under 20 yo. Bacteria transmitted among people living in close contact. LOS may trigger shock, petechiae

Meningococcal meningitis

Can cause death within 6 hrs of symptoms (abrupt sore throat, fever, headache, stiff neck, vomiting, and convulsions)

Meningococcal septicemia

(blood poisoning) can also be life threatening

Neisseria meningitidis

Diagnosed G- diplococci in phagocytes of the CNS, presence of antibodies against N. meningitidis

Neisseria meningitidis

Treated with antibiotics such as ceftriaxone, a cephalosporin

Neisseria meningitidis

Prevented by vaccination against all strains, asymptomatic carriers make eradication unlikely.

Enterobacteriaceae and Pasteurellaceae

Pathogenic, G-, facultative anaerobic bacilli, oxidase test distinguishes between families, E is -, P is +

Enterobacteriaceae

Intestinal microbiota of most animals and humans, ubiquitous in water, soil, and decaying vegetation, are the most common G- pathogens of humans. Some have capsules, only a loose slime layer, all contain LPS consisting of core polysaccharide, O polysaccharide, and lipid A.

Enterobacteriaceae

Diagnosed by enteric bacteria in urine, blood, and CSF, biochemical tests rapidly identify enteric bacteria

Enterobacteriaceae

Internal infections are treated with antimicrobials

Enterobacteriaceae

Prevention by proper hygiene and sewage control

Coliforms

aerobic or facultatively anaerobic Gram-negative non-spore forming rods that produce gas from lactose and can be diagnosed by growth on MacConkey's agar or Eosin=Methylene blue agar, commonly found in soil, in plants, on decaying vegetation, colonize intestinal tracts of humans and animals, coliforms in water indicative of impurity

Escherichia coli

Most common and important of the coliforms, numerous antigens, virulent strains have genes for fimbriae, adhesins, exotoxins, located on virulence plasmids

Escherichia coli

Can cause septiciemia, UTIs, meningitis, but gastroenteritis is the most common disease, mediated by exotoxins. Treatment includes cephalosporins, sulfonamides, semi-synthetic pincillins

Escherichia coli O157:H7

Most prevalent, dangerous serotype of E.coli, causes diarrhea, UTI, neonatal meningitis, sepsis, pneumonia, hemorrhagic colitis, hemolytic uremic syndrome. Associated with consumption of uncooked ground beef or contaminated milk. Produces shiga like toxin which inhibits protein synthesis. (Pt 1, slide 23, 25)

Klebsiella

Opportunistic coliform, non motile, in digestive and respiratory systems of animals and humans, can cause opportunistic infections, capsule protects bacteria from phagocytosis

Klebsiella pneumoniaw

Most commonly isolated pathogenic species, causes violent pneumonia involving bloody sputum, may be involved in bacteremia, meningitis, wound infections, UTIs

Serratia

Opportunistic coliform, produces red pigment when grown at room temp, can grow on catheters, saline solutions, can cause life threatening opportunistic infections in immunocompromised patients, defficult to treat due to resistance

Proteus

Opportunistic noncoliform, G-, facultative anaerobe, very motile

Proteus mirabilis

most commonly associated with human disease, causes UTI in patients with long term urinary catheters, infection induced kidney stones can help, produces urease enzyme which breaks down urea to CO2 and ammonia. Raises pH leading to precipitation of ions. Resistant to many antimicrobials

Salmonella

Truly pathogenic enterobacteria, G-, motile bacilli, does not ferment lactose, urease -, oxidase -, produces H2S, Type III secretion system is an important virulence factor. In the intestines and feces of birds, reptiles, and mammals, most human infections due to food contaminated with animal feces, poultry and eggs a common source. Can cause salmonellosis and typhoid fever

Typhoid fever

Caused by salmonella enterica, ingest bacteria in contaminated food or water, can pass through intestines into bloodstream carrying it to liver, spleen, and gallbladder. Peritonitis can result. Can be treated with fluid and electrolyte replacement, as well as ampicillin and ciprofloxacin, vaccine can give temporary protection.

Shigella

G-, non motile, oxidase-, urease -, primarily a parasite in the digestive tract of humans, produces diarrhea inducing enterotoxin, causes shigellosis characterized by abdominal cramps, diarrhea, and bloody stools.

Shigella dysenteriae

Produces Shiga toxin (acts on 60s ribosome to inhibit protein synthesis)

yersinia

Normal pathogen of animals, conains virulence plasmids coding for adhesins and type III secretion system

Yersinia enterocolitica

causes inflammation of the intestinal tract, transmitted by fecal-oral route

Yersinia pseudotuberculosis

Similar to Y. enterocolitica but less severe

Yersinia pestis

Extremely virulent, causes bubonic pneumonic plague

Bubonic plague

High fever, swollen, painful lymph nodes called buboes

Yersinia

Characteristics symptoms usually enough for diagnosis and many antibacterial drugs are effective against yersinia

Pasteurellaceae

Small, non motile facultative anaerobes, oxidase +, fastidious, require heme or cytochromes for growth

Pasterurella

In normal oral and nasopharyngeal microbiota of animals, humans infected by animal bites or inhalation of aerosols, produce localized inflammation and swelling of lymph nodes

Pasteurella multocida

Causes most human cases of pasteurella

Pasteurella

Diagnosis by identification of bacteria in patient specimens, can be cultured on blood agar/chocolate agar, antibacterials are effective

Haemophilus

Require heme and NAD+ for growth, hence are obligate parasites, H.influenzae is the most significant, common cause of meningitis between children 3-18 months of age, symptoms include lethargy, vomiting, photophobia, stiff neck, can cause swelling of epiglottis, IV cephalosporin is recommended, Hib vaccine for prevention

H. ducreyi

Sexually transmitted Haemophilus, causes a painful, soft genital ulcer called chancroid or soft chancre by producing a toxin that kills human epithelial cells, often asymptomatic in women

Bartonella

Aerboc bacilli, found in animals but only causes disease in humans, growth requirements are 37 degrees C with CO2

Bartonella bacilliformis

Invades and weakens erythrocytes, causes bartonellosis, sand flies of genus phlebotomus transmit the bacterium

Bartonellosis

fatal disease characterized by fever, anemia, muscle pain

Bartonallea quintana

Causes trench fever, trasnmitted by human body lice, headaches, fever, pain in the long bones

Bartonella henselae

Causes cat scratch disease, transmitted through cat scratches and bites through flea, affects children primarily, disease involves prolonged fever and localized swelling at site of infection and lymph nodes, triggers angiogenesis

Brucella

small, non motile, aerobic coccobacilli, lacks capsule but survives phagocytosis by preventing fusions of phagosomes containing bacteria with lysosomes, can infect animals or humans, lives as an intracellular parasite in organs like uterus, placenta, and epidydimus. causes brucellosis

Brucellosis

Undulant fever, Bang's disease, Malta fever, often asymptomatic or mild disease in animals, but can cause abortion or sterility. Illness in humans characterized by fluctuating fever, chills, myalgia, human infection due to contact with contaminated dairy products or infected animal parts

Bordetella

Small, aerboci, nonmotile, coccobacillus, B. pertussis is the most important

Bordetella pertussis

Causes pertussis (whooping cough) by interfering with action of ciliated epithelial cells of the trachea. Most cases of the disease are in children, adhesins and toxins mediate the disease, bacteria inhaled in aerosols and multiply in epithelial cells

Filamentous hemagglutinin, and pertussis toxin

Two major adhesins of pertussis

Pertusis toxin

Results in increased mucous production

Adenylate cyclase toxin

increased mucus, inhibits killing

Dermonecrotic toxin

localized constriction and hemorrhage of blood vessels, tissue destruction

Tracheal cytotoxin

inhibits movement of cilia and causes expulsion of cells from the lining of trachea

Bordetella

Pertussis symptoms are diagnostic, bacteria are sensitive to dessication, so inoculated immediately in Boder-Gengou medium

Bordetella

Treatment is mainly supportive, recovery depends on the regeneration of epithelium

Bordetella

Immunization with DTaP

Burkholderia

aerobic, flagellated, found in soil

Burkholderia cepacia

can decompose organic molecules, likely involved in clean up of contaminated environmental sites, used by farmers to reduce fungal infections of plant crops, opportunistic pathogen of cystic fibrosis patients, metabolizes copious mucous secretions, resistant to many antimicrobials, treated with beta-lactams

Burkholderia pseudomallei

Causes melioidosis, emerging endemic in southeast Asia and Australia, categorized by CDC as a potential bioterror agent

Pseudomonads

G-, aerobic bacilli, ubiquitous in soil, decaying organic matter, moist environments, problematic in hospitalsEntner-Dourdoroff pathway is a major means of glucose metabolism instead of regular Embden-Meyerhoff pathway

Pseudomonas aeruginosa

Rarely causes disease, opportunistic pathogen, can colonize any organ or system, often infects burn victims and lungs of cystic fibrosis patients. treatment is difficult due to drug resistance, aminoglycosides, beta-lactam fluorquinolones, polymyxin

Fimbriae

Used with other adhesins by P. aeruginosa for attachment to host cells

Neuraminidase

Used by P. aeruginosa to enhance attachment

Elastase

Used by P. aeruginosa to break down elastic fibers, degrades complement components, and cleaves lgA and lgG

Exotoxin A and exoenzyme S

Used by P. aeruginosa to inhibit protein synthesis and cause cell death

Moraxella and Acinetobacter

Aerobic, short, plump bacilli

Moraxella catarrhalis

causes opportunistic infections of the sinuses, bronchi, ears, and lungs

Acinetobacter

Grows in soil, water, and sewage, causes opportunistic infections of the respiratory, urinary, and CNS, antibiotic resistance is a huge problem

Francisella tularensis

nonmotile, strictly aerobic coccbacillus, intracellular parasite, most common reservoir is rabbits and ticks, causes tularemia

Tularemia

(rabbit fever, tick fever), spread through bit of infected tick, swollen lymph nodes most common symptom, highly infectious, vaccine for at-rick individuals, streptomycin the drug of choice

Legionella

Causes Legionnaire's disease, aerobic, slender pleomorphic bacteria, extremely fastidious (charcoal yeast extract agar is used). Humans inhale bacteria in aerosols from water sources. L. pneumophilia causes most disease, results in fever, chills, pneumonia. Diagnosed by fab staining, treated with fluoroquinolones, azithromycin

Coxiella burnetii

Small, aerobic bacteria, infective body allows for survival in harsh environments, obligate intracellular parasite, grows inside phagolysosomes. Causes Q fever, transmission occurs by inhalation, infects mammalian and avian hosts, transmitted by ticks.

Q fever

Incubation period of more than 20 days, high fever, chills, muscle pain, mild pneumonia, occurs among ranchers, veterinarians, food handlers, chronic disease may lead to endocarditis, diagnosis by serological testing, treatment by oral doxycycline

Bacteroides

Normal microbiota of intestinal and upper respiratory tracts, possess LPS, but lipid A has little endotoxin activity

Bacteroides fragilis

Involved in a variety of conditions, accounts for 85% of GIT diseases, virulence factors are fimbriae, capsule, and short chain fatty acids. Abdominal infections, genital infections in women, wound infections of the skin, grows on bile-eschulin agar in anaerobic environment, metronidazole is drug of choice

Prevotella

Anaerobic, G- bacteria, normal microbiota of urinary, genital, and upper respiratory tracts. Sensitive to bile. Involved in sinus and ear infection, periodontal infection, gyno infections, brain abscesses, abdominal infections. Treatment includes surgical removal of infected tissue and use of antmicrobials