Classification of Pathogenic Bacteria Flashcards
Eschericha coli (enterohaemorrhgic E. coli)
gram neg bacilli lactose fermenting coliform commensal of GI tract most common cause of UTIs also causes neonatal meningitis and some strains cause diarrhoea
E. coli 0157
causes bloody darrohea and haemolytic-ureamic syndrome
Pseudomonas species
gram neg oxidase positive rods
water and soil organism
can contaminate medical equipment
hospital acquired cause of sepsis - pneumonia, UTI
respiratory infection in cystic fibrosis
sensitive to a limited range of antibiotics
Prevotella
gram neg bacillus oral flora anaerobe
previously called bactericides
involved in dental infections and aspiration pneumonia
usually penicillin and metronidazole sensitive
Porphyromas
gram neg bacillus miscellaneous anaerobe
found in mouth and else where
Haemophilus influenzae
gram neg fastidious cocco-bacilli
capsulated strains type b (Hib) cause childhood meningitis and epiglottitis (vaccine available)
non-capsulate strains cause exacerbations of CAOD, sinusitis and otitis media
does not cause influenza!
Helicobacter pylori
gram neg curved bacilli
microaerophilic
strongly urease positive
causes gastritis and peptic ulceration
Klebsiella spp.
gram neg coliform bacilli
lactose fermenting
causes UTI, HAIs and occasionally pneumonia
may become resistant to antibiotics
Salmonella enterica
gram neg lactose non-fermenting
self-lifting enterocolitis (w/ or w/o bloody diarrhoea)
2nd most common cause of bacterial diarrhoea in UK
Salmonella typhi
gram neg lactose non-fermenting cause of typhoid fever fever and constipation in early stages risk during foreign travel vaccine available
Shigella species
gram neg coliform
lactose non-fermenting rods
4 species, only 1 endemic in UK (shigella sonnei)
causes dysentery (blood & pus in stool)
low infective dose - easily spread, outbreaks common in nurseries
Proteus species
gram neg coliform
lactose non-fermenting
causes UTIs - often associated w/ renal calculi (as urease it produces makes urine alkaline)
Bacteriodes fragillis group
gram neg bacilli anaerobes
part of normal colonic flora
often present in mixed intra-abdominal infection s
resistant to penicillin, sensitive to metronidazole
Coxiella burnetti
gram neg obligate intracellular causes Q fever - usually no symptoms but can have febrile symptoms for up to 2 weeks can cause pregnant woman to miscarry spread to humans by infected animals highly resistant to environmental stress
Eschericha coli (enterotoxogenic E. coli)
gram neg bacilli
lactose fermenting coliform
commonest cause of traveller’s diarrhoea
Neisseria gonorrhoeae
gram neg diplococcus
causes gonorrhoeae (pelvic inflammatory disease in woman, urethritis in men)
must be cultured quickly or dies
in females ensure endocervical swab is taken to avoid missing pathogen
Moraxella catarrhalis
gram neg coccus
respiratory pathogen
causes exacerbations of chronic bronchitis
causes otitis media in children
more common in people w/ underlying lung pathology
80% strains contain beta-lactamase
Vibrio cholerae
gram neg curved bacilli
causes severe diarrhoea in form of cholera
ingested in water contaminated by faeces
Neisseria meningitis
gram neg diplococcus
cause of mengiococcal septicaemia and meningitis
meningitis has high mortality and should be treated w/ IV penicillin on presumption of diagnosis
Vaccines - Men A, C, Y, W-135 conjugate & 4 component Men B
Campylobacter jejuni
gram neg curved bacilli microaerophilic source: domestic animals faecal-oral route foul smelling then bloody diarrhoea commonest cause of gastro-enteritis in UK
Enterococcus faecalis
gram positive gut commensal
can cause UTI
vancomicin resistant enterococci (VRE) increase problem in hospitals
Staphylococcus saprophyticus
gram positive coagulase negative
cause of UTI in woman of child bearing age
Staphylococcus agalactiae
gram positive
group B beta-haemolytic on blood agar
causes neonatal sepsis (meningitis/bacteraemia)
genital tract carriage common (25% in woman)
Staphylococcus epidermis
gram positive coagulase negative
ubiquitous on skin
may cause infection of catheters, prostheses, ventricle-peritoneal shunts
Streptococcus pyogenes
gram positive
group A beta-haemolytic on blood agar
cause of sore throats, cellulitis, impetigo
post-streptococcal sequelae: acute rheumatic fever, acute glomerulonephritis
can also cause necrotising fasciitis
treat w/ penicillin
Staphylococcus aureus
gram positive, coagulase positive
normal flora of skin & nose
major pathogen especially of skin - boils, cellulitis, impetigo, endocarditis, osetomyelitis, toxin-mediated food poising, toxic shock syndrome
MRSA have altered penicillin binding proteins - resistant to all penicillins & cephalosporus
Viridians streptococci
gram positive
alpha-haemolytic on blood agar
normal oral flora
common cause of endocarditis following dental treatment
Clostridium tetani
gram positive bacilli
spore forming anaerobe
cause of tetanus (uncontrolled muscle spasms) due to toxin causing loss of inhibition of NMJ
antigenic ally modified toxoid used for immunisation
Streptococcus pneumoniae (pneumococci)
gram positive diplococci
aplha-haemolytic on blood agar
normal flora of upper respiratory tract
commonest cause of bacterial lobar pneumonia
major cause of meningitis in children/elderly
vaccine available
Listeria monocytogenes
gram positive rod
found in animal and veg products
causes meningitis in neonates and elderly
bacteraemia in pregnancy
Clostridium difficle
gram positive bacilli
spore forming anaerobe
can be carried asymptomatically in gut of healthy people
cause of antibiotic associated diarrhoea
Causes psuedomembranous colitis
detect antigen and toxin in stool sample by ELISA
Clostridium perfringes
gram positive bacilli
spore forming anaerobe
found in soil and normal commensal in human and animal
toxogenic strains cause food poisoning
infects serious wounds can cause gas gangrene
Clostridium botulinum
gram positive bacilli spore forming anaerobe cause of botulism following ingestion of contaminated food most potent neurotoxin known to man rare in UK source of botox - inhibits Ach
Bacillus cereus
gram positive aerobic rod
beta-haemoltic
found in soil and food
common source of food poisoning from fried rice
Bacillus anthracis
gram positive rod
causes anthrax
Treponema pallidum
spirochaete
causes syphilis
does not culture on media
diagnosis uses serology and nucleic acid amplification tests (NAAT)
management: antibiotics, contact screening, antenatal screening
Borrella burgdofen
spirochaete
causes Lyme disease
organism transmitted from rodent to man by lodes tick
presents w/ skin rash (erythema chronic migrans) & arthritis
organism difficult to grow, serology used
Leptospira interrogans
spirochaete
causes leptospirosis (Weil’s disease) - febrile illness, systemic upset, renal and liver failure, aseptic meningitis, 10% mortality
infects animals and concentrates in kidneys
spread via urine/other body fluids
sewage workers and people who do water sports at risk
Chlamydia trachomatis
miscellaneous obligate intracellular
ophthalmic and genital tract infecton - urethritis, cervicitis, PID, lyphogranuloma venereum, neonatal conjunctivitis & trachoma, pneumonia in neonates and immunocompromised
culture laborious, infection diagnosed by detecting chlamydia antigen by EIA or chlamydia DNA by amplification test (e.g. PCR)
Mycoplasm hominis
miscellaneous
may be involved w/ pelvic inflammatory disease and post-pleural fever
special media must be used
testing not widely available
Mycoplasm pneumoniae
miscellaneous
important cause of atypical pneumonia
appears in 4 year cycles
diagnosis usually serological, through appearance of antibody, may be considerably delayed, by detection of specific IgM or rising CFT titre
Chlamydia psittaci
miscellaneous obligate intracellular cause of psittacosis and ornithosis contracted by contact w/ birds present as pneumonia puts pregnant woman at risk of abortion, they should stay away from sheep during lambing diagnosis involves serology
Chlamydia pneumoniae
miscellaneous obligate intracellular
most recent recognised species
culture difficult, serology for antibody best option
tests not widely available right now
Mycobacterium leprae
alkali and alcohol fast bacilli
causes leprosy - attacks PNS
cannot be cultured
mainly in india, nepal, brazil, parts of africa
Mycobacterium tuberculosis
alkali and alcohol fast bacilli
causes tuberculosis
due to specific straining/culture methods - have to request tests for suspected cases
multi-drug resistant TB is big problem in parts of the world
immunisation possible w/ live attenuated BCG strain
