ch11 bacteria (gram negative)

microbiology

Rickettsia rickettsii

• Obligate intracellular

• causes Rocky Mountain Spotted Fever

• transmitted by ticks

• signs and symptoms: spotted rash (palms & soles), fever, muscle pain

• diagnosis: cell/tissue culture or direct serology

• treatment: antibiotics

Neisseria gonorrhoeae

• diplococci (coffee bean shape) fastidious capnophiles

• causes gonorrhea

• transmitted sexually or perinatal (ophthalmic neonatorum)

• signs and symptoms: Males have urethral discharge/pus, fever, inflammation, WBCs present, may cause gonococcal arthritis (joint pain); Females mostly asymptomatic but can develop PID, scarred fallopian tubes, infertility, ectopic pregnancy

• diagnosis: Gram stain, Thayer Martin Agar with CO2 generator, ELISA, DNA probes, PCR urine sample

• treatment: antibiotics

Neisseria meningitidis

• diplococci (coffee bean shape) fastidious capnophiles

• causes meningococcal meningitis

• transmission: respiratory droplets

• signs and symptoms: fever, severe headache, stiff neck, flu-like symptoms, inflammation, rash, purple fingers due to endotoxic shock, nausea, vomiting, dizziness

• diagnosis: rapid latex agglutination for capsular antigen, Gram stain and culture, PCR test, serotype B is most common in US

• treatment: antibiotics penicillin, cephalosporins

• prevented by vaccine

Bordetella pertussis

• rod to coccobacilli (mostly rod-like), contains capsules and tracheal cytotoxin (exotoxin)

• causes whooping cough (pertussis)

• transmission: respiratory droplets

• signs and symptoms: catarrhal stage - common cold (1-2 weeks); paroxysmal stage - violent coughing sieges, mucus accumulation, cyanosis (1-6 weeks); convalescence stage - symptoms improve (couple weeks to months); may cause seizures, brain damage

• diagnosis: nasopharyngeal swab onto Bordet Gengou agar, serology, PCR

• treatment: antibiotic erythromycin

• prevented by pertussis vaccine (does not last a lifetime)

Burkholderia cepacia

• motile, aerobic, rod, endotoxin

• causes respiratory infections in patients with cystic fibrosis or pneumonia

• transmission: hospital associated infection (HAI)

• signs and symptoms: coughing, fever

• diagnosis: Gram stain

• treatment: can be resistant to disinfectants/antibiotics due to biofilm in respiratory tract

Pseudomonas aeruginosa

• bacilli, grows in most places (needs few nutrients), polar flagella

• causes nosocomial infections (HAI), swimmer’s ear, UTI, burn/wound/respiratory infections, dermatitis, conjunctivitis

• transmission: opportunistic

• diagnosis: TSA - green pigment, fruity odor, MAC non-fermenter of glucose and lactose

• treatment: antibiotics

Legionella pneumophila

• coccobacilli

• causes Legionnaires disease (pneumonia)

• transmission: airborne (found in streams, warm water pipes, cooling tower), NOT person to person

• signs and symptoms: coughing, fever, muscle ache, headache in immunocompromised people

• diagnosis: buffered charcoal yeast extract agar, FA test (direct serology, PCR), DNA probes

• treatment: antibiotic erythromycin

Vibrio cholerae

• motile comma shaped bacilli, halophile, exotoxin

• causes cholera

• transmission: found in coastal water, fecal-oral route

• signs and symptoms: severe fluid loss from diarrhea, rice-water stools, “tenting” in pinched skin (dehydration), NO fever

• treatment: fluid & electrolyte replacement, antiobiotics

• prevention: adequate water treatment, properly cooked food, hygiene (keep open wounds clean)

Escherichia coli

• straight rods, facultative anaerobic, ferment glucose/carbs, motile (peritrichous flagella), enteric

• causes UTI, traveler’s diarrhea

  • O157:H7 - hemolytic uremic syndrome (kidney damage) due to exotoxin

• transmission: normal flora of GI tract

  • O157:H7 - fecal-oral route

• diagnosis: urine sample (UTI), MAC lactose fermenter, indole positive (catabolism of tryptophan)

  • O157:H7 - stool culture, inability to ferment sorbitol, DNA fingerprinting

• treatment: antibiotics, IV rehydration

Proteus mirabilis

• bacilli, extremely motile, enteric, peritrichous flagella, facultative anaerobe

• causes UTI, wound infection

• transmission: endogenous, normal flora of GI tract

• diagnosis: swarming on BAP & TSA, MAC nonlactose fermenter, urease positive

• treatment: antibiotics

Salmonella enterica

• bacilli, enteric

• causes gastroenteritis

• transmission: fecal-oral route (from poultry, reptiles, hedgehogs, fish, duckling)

• signs and symptoms: diarrhea, vomiting abdominal cramp, low grade fever

• diagnosis: stool culture

• treatment: self-limiting, rehydration

• prevention: don’t eat raw eggs or meat

Haemophilus influenzae

• coccobacilli to rod (pleomorphic), fastidious capnophile, found in upper respiratory tract

• causes *epiglottitis, *meningitis, bronchitis, conjunctivitis, otitis media

  • **caused by encapsulate type B

• transmission: respiratory droplets

• diagnosis: chocolate agar in CO2, X (heme) and V (NAD) factors needed for growth

• treatment: antibiotics

• prevention: vaccine

Campylobacter jejuni

• curved bacilli, one polar flagellum

• causes gastroenteritis

• transmission: fecal-oral route (raw milk, poultry, meats, apple cider)

• diagnosis: CAMPY agar, low O2, 42 C (slightly above body temp)

• treatment: antibiotics, rehydration

Helicobacter pylori

• contains enzyme urease (ammonia → urea), buffering effect allows it to grow in stomach

• causes stomach (peptic) ulcers

• transmission: ubiquitous, acquired by ingestion

• signs and symptoms: stomach bleeding, abdominal pain, dark stools

• diagnosis: gastric biopsy, indirect serology, urea breath test

• treatment: bismuth subsalicylate (pepto bismol), antibiotics, heavy metals

Chlamydia (trachomatis and pneumoniae)

• obligate intracellular

• causes STI, trachoma (eye disease leading to blindness), urethritis, atypical mild pneumonia in older adults

• transmission: STI - sexual, perinatal; Trachoma - poor sanitation, touching eyes/face

• signs and symptoms: STI - pain, watery urethral discharge, females often asymptomatic

• diagnosis: cell culture (costly, not preferable), immunofluorescence (direct serology), PCR test from urine sample

• treatment: antibiotic tetracycline

Treponema pallidum

• spirochete, axial filaments, sheath, cannot gram stain but closely related to gram negatives

• causes syphilis

• transmission: sexual, congenital (in the womb)

• signs and symptoms:

  • Primary stage - painless genital lesions/ulcer (chancre)

  • Secondary stage - rash (palms & soles), flu-like symptoms, systemic infection

  • Latent stage - lasts many years

  • Tertiary stage - weakened blood vessel walls (aneurysm), seizures, dementia, tissue damage (gumma) due to improper immune function

• diagnosis: darkfield microscopy (not preferred), blood test, indirect serology (RPR, FTA-ABS)

• treatment: antibiotic penicillin (only for primary and secondary stages)

Borrelia burgdorferi

• spirochete

• causes Lyme disease

• transmission: deer ticks, take 36-48 hrs to transmit disease (must get tick off ASAP)

• signs and symptoms: bulls eye rash, flu-like symptoms, meningitis, irregular heartbeat, Bell’s palsy (facial nerve), arthritis (late stage)

• diagnosis: serology

• treatment: antibiotic doxycycline

Bacteroides

• bacilli, obligate anaerobe, found in mouth and large intestine

• causes deep tissue infection

• transmission: endogenous (i.e. perforated bowels after vehicle accident)

• signs and symptoms: pus, pain, fever, bad odor

• diagnosis: reduced media (anaerobic jar), aspirate sample

• treatment: antibiotics, drain pus

Fusobacteria

• anaerobic bacilli, pointed ends (spindle shape), found in mouth

• causes dental diseases

• transmission: endogenous

• signs and symptoms: redness, swelling, pus, fever

• diagnosis: anaerobic jar

• treatment: drain pus, antibiotics