Bacteriology cont d. Dr. Hamed Al-Zoubi

Transcription

1 Bacteriology cont d Dr. Hamed Al-Zoubi

2 Listeria g+ve rods Neisseria -ve Haemophilus influenzae -ve Bordetella -ve

3 Listeria monocytogenes: Differential characteristics: Gram positive, non-spore forming, motile, facultative anaerobic, β-hemolytic, bacilli. Optimal growth temperature is 30 C to 37 C However, it can grow in a wide range of 0.0 C to 45 C Tumbling motility if grown at C Growth on blood agar > β-haemolysis enhanced by staph

4 L. monocytogenes Virulence factor: 1. Hemolysin (listeriolysin O) 2. Phospholipase C 3. internalin 4. Catalase

5 L. Monocytogenes / entry and spread

6 Clinically L. monocytogenes is an important human pathogen It s widley distributed in environment (soil, water, vegetation, sewage, animals and food chain e.g colesalaw, soft cheese and milk) MOT Asymptomatic carrier in ~ 5% (intestine & birth canal) People at more risk of getting the infection: 1. Pregnant women 2. Neonates 3.Elderly and immunocompromised patients 4.Those > 50 years and alcoholics

7 Clinically 1. Non-pregnancy associated: mild flu or GI distress Bacteremia, CNS infection: meningitis, encephalitis, brain abscess Infective endocarditis sepsis In immunosuppressed and older adults, and patient receiving chemotherapy cause invasive listeriosis (systemic infection). 2. Pregnancy associated: Spontaneous abortion (2nd/3rd trimester) or stillbirth. Neonatal sepsis

8 Diagnosis Samples: 1. blood 2. CSF 3. Amniotic fluid, placenta 4. Urine Tests: 1. Gram stain: Gram-positive rods or coccobacilli. 2. Grow well in blood agar and Chocolate agar (1-2 days). Colonies are surrounded by narrow zone of β- hemolysis enhanced by S. aureus motility

9 direct Gram Stain on CSF (seen in ~ 30% of cases)

10 Treatment and prevention Treatment: Ampicillin and Gentamicin for synergism. Duration of treatment in CNS infection is 3 weeks Alternatives: e.g in Penicillin allergic patients: 1. Vancomicin, 2. Trimethoprim+sulfamethoxazole (septrin)

11 Gram negative bacteria Neisseria N. Gonorrhea N. Menigitides) Haemophilus Bordetella

12 Neisseria Gonorrhoeae Caused by Neisseria gonorrhoeae (gonococcus) : Gram negative diplococcic (kidney beans), oxidase positive non-capsulated Sensitive to dehydration and cool conditions Infects humans only but Not part of the normal flora (infection can be asymptomatic)

13 Gonorrhoeae

14 Gonorrhoeae Virulence factors: Pili and IgA protease Endotoxin (LOS) and outer membrane protein (OMP) Gonococccci infect mucosal surface such as urethra and vagina, cervix, rectum, pharynx and conjunctiva

15 Gonorrhoeae Clinically Transmitted sexually amongst adults and can be transmitted to newborns during birth 95% of men are symptomatic and 40% of women are symptomatic. I.P 2-5 days Urogenital infections:...

16 Gonorrhoeae Babies born to infected women may suffer ophthalmia neonatorum: A severe purulent eye discharge with peri-orbital oedema occurs within a few days of birth. If untreated, ophthalmia leads rapidly to blindness. It may be prevented in areas of high prevalence by the instillation of 1% aqueous silver nitrate in the eyes of newborn babies. Alternatively, topical erythromycin can be used; this has the advantage of being active against chlamydia and less toxic

17 Gonorrhoeae

18 N. meningitis Shares many structural and virulence characteristics with N. gonorrhea but it is encapsulated Major cause of meningitis, other systems infections.. Many serotypes Can be part of normal flora

19 Neisseria Diagnosis: Exudates, swabs, CSF... NEISSERIA is intolerant of drying and temperature changes; it readily undergoes autolysis. Where there is likely to be any delay, transport media must be used to carry the material on swabs. 1. Gram stain: gram negative intracellular (within neutrophils) organism

20 Gonorrhoeae 2. Culture: Thayer-Martin medium or chocolate agar. The combination of oxidase-positive colonies and Gramnegative diplococci provides a presumptive diagnosis.

21 Neisseria Treatment : N. Gonorrhea :Cefixime+Azithromycin orally N. Meningitis: 3 rd G cephalosporins Prevention: Meningitis: Vaccine Gonorrhea : No vaccine / non-capsulated + antigenic variability Sexually transmitted Rapid diagnosis Use of effective antibiotics Tracing, examination and treatment of contacts Neonates: erythromycin or silver nitrates

22 H. influenzae Part of normal respiratory flora: 2-4%, 80%? Gram negative small bacilli (old culture) or coccobacilli (young culture) Requires factors X and V Catalase and Oxidase positive

23 H. influenzae

24 H. influenzae Virulence factors: Polysaccharides capsule (in 10%): inhibits phagocytosis and complement activation six capsular types, designated a-f, which can be identified by a polymerase chain reaction (PCR) method The most important is type b, a polymer of ribosyl ribitol phosphate.

25 H. influenzae Fimbriae: which assist attachment to epithelial cells Immunoglobulin (Ig) A proteases, which are also involved in colonization Outer membrane proteins and lipopolysaccharide, which may contribute to invasion at several stages

26 H. influenzae Clinically: Respiratory route Common age: 5m-5years (capsulated) / elderly (mainly noncapsulated) invasive infections and non-invasive infections invasive: meningitis, epiglottitis, pneumonia and septic arthritis. Commonly caused by encapsulated types mainly serotype b

27 Diagnosis History and Examination pus, sputum or aspirates from joints, middle ears or sinuses, CSF can provide a rapid presumptive identification. Blood for culture in invasive conditions and in epiglottitis Blood cultures are usually positive in epiglottitis. throat swabs in patients with suspected acute epiglottitis should not be carried out, as attempts to obtain the sample may precipitate complete airway obstruction

28 H. Influenzae / diagnosis The viability of H. influenzae in clinical specimens declines with time, immediate transfer 1. Antigen detection The detection of type b polysaccharide antigen in body fluids or pus is useful, particularly in patients who received antibiotics before specimens were obtained. A rapid latex agglutination test with rabbit antibody to type b polysach. Capsular antigen is used most commonly. Cross reactivity with pneumococcus and E.coli

29 H. Influenzae / diagnosis 2. Plate on chocolate agar - Gram stain Catalase oxidase tests Antibiotic sensitivity Capsular serotyping

30 H. Influenzae / treatment Untreated invasive infection: Mortality rate of 90% Among cephalosporins, compounds such as cefuroxime, cefotaxime and ceftriaxone are highly active. Ceftriaxone (or a related cephalosporin such as cefotaxime) is the antibiotic of first choice for the treatment of meningitis and acute epiglottitis. > It is bactericidal for H. influenzae, achieves good concentrations in the meninges and cerebral tissues, and is highly effective.

31 H. Influenzae / prevention Conjugate vaccines for type b : polysaccharide capsule is covalently coupled to proteins such as a non-toxic variant of diphtheria toxin or Neisseria meningitidis outer membrane protein 3 doses separated by a month 2,3,4 months age and a booster at 12 months of age Immunization of infants significantly reduces pharyngeal carriage of Hib, but has no effect on the carriage of other capsular types or non-capsulate strains.

32 Bordetella Bordetella organisms are small, gram-negative bacilli/ coccobacilli capsulated, non-motile strict aerobes. The most important human pathogen in this genus is B. pertussis, the organism which causes whooping cough. A man pathogen. spread via the respiratory route and the organism is noninvasive.

33 Bordetella Virulence Adhesion by filamentous hemagglutinin, and the pertussis toxin Tracheal toxin: cytotoxin caues paralysis of the resp. cilia Clinically: whooping cough? Diagnosis: Charcol cephalexin medium Serology, PCR Treatment: azithromycin Prevention: DTaP (HBsAg and IPV added nowdays)

34 The End