Overview of bacterial infections

Contains introductory information of all bacterial infections affecting man

1. Overview of bacterial infections Dr. Abhijeet Mane Associate Professor Department of Microbiology BV(DTU)MC, Pune 16 March 2022 1

2. Introduction Overview of various bacteria infecting man Conventionally based on Gram stain Infections can be grouped in infections by Gram positive cocci Gram negative cocci Gram positive bacilli Gram negative bacilli Miscellaneous bacteria 16 March 2022 2

3. Hans Christian Gram 16 March 2022 3

4. Gram positive cocci (GPC) infections Micrococcaceae catalase positive, GPC in tetrads or clusters Tetrads – Micrococcus, nonpathogenic Clusters – Staphylococcus, pathogenic Streptococcace Catalase negative, GPC in pairs, chains Pairs – Enterococcus, Streptococcus pneumoniae (pathogenic) Short chains – Beta-hemolytic streptococci (pathogenic) Long chains – Viridans streptococci (commensals, occasionally pathogenic) 16 March 2022 4

5. 16 March 2022 5 GPC in clusters GPC in chains GPC in tetrads GPC in pairs

6. Streptococcus pneumoniae 16 March 2022 6

7. Staphylococcus species S.aureus is most virulent species, pathogenic to man Other staphylococci, CoNS, usually harmless commensals and less virulent But occasionally – prosthetic device associated and SSIs 16 March 2022 7

8. S.aureus Community and nosocomial infections Virulent factors – Toxins – hemolysins, exfoliative toxin, enterotoxin and TSST Extracellular enzymes – coagulase 16 March 2022 8

9. S.aureus (contd…) Clinical manifestations Skin and soft tissue – folliculitis, furuncle, cellulitis, etc. Musculoskeletal – osteomyelitis, septic arthritis, abscess Respiratory tract Bacteremia, sepsis UTI Toxin – Scalded skin syndrome, food poisoning, etc. Laboratory Diagnosis GPC in clusters Golden yellow pigment, beta hemolytic Coagulase positive MRSA – resistant to beta lactam antibiotics Treatment Cloxacillin Vancomycin 16 March 2022 9

10. 16 March 2022 10 Golden yellow pigment of S.aureus Beta hemolysis Cellulitis

11. Streptococcus species Catalase negative, GPC, in chains Based on hemolysis on Sheep Blood Agar Alpha hemolytic – viridans streptococci Beta hemolytic – S.pyogenes, S.agalactiae Gamma hemolytic - Enterococcus 16 March 2022 11

12. S.pyogenes Group A Virulence factors Cell wall antigen – M protein Toxins – streptococcal pyrogenic exotoxin (SPE) Various enzymes – streptokinase, streptodornase, etc. 16 March 2022 12

13. Clinical manifestations Suppurative - sore throat, scarlet fever, skin and soft tissue (impetigo, cellulitis, necrotizing fasciitis, etc.) Non suppurative – acute RF, post streptococcal GN Laboratory diagnosis GPC in chains, catalase negative S.pyogenes – pinpoint beta hemolytic colonies on SBA Treatment Primarily penicillin Erythromycin in penicillin allergy 16 March 2022 13

14. 16 March 2022 14 Rash of scarlet fever Necrotizing fasciitis

15. S.agalactiae Gr B – colonizes female genital tract Cl. Manifestations - Neonatal meningitis, sepsis Treatment - Penicillin Enterococcus Normal flora of human intestine Cl. Manifestations - UTI, bacteremia, endocarditis, intra abdominal infections LD – oval shaped GPC in pairs, NH colonies on SBA Treatment – Ampicillin +/- gentamicin, vancomycin 16 March 2022 15

16. Viridans streptococci Commensals of mouth Can cause – dental caries, subacute bacterial endocarditis, suppurative infections LD – GPC in long chains Alpha hemolytic colonies on SBA Treatment – penicillin, vancomycin Streptococcus pneumoniae Lobar pneumonia, otitis media in children and meningitis in all ages Cl. Manifestations – pneumonia, BSI, meningitis, otitis media, etc Treatment – penicillin G, Ceftriaxone LD – capsulated GPC Carrom coin, alpha hemolytic colonies on SBA 16 March 2022 16

17. 16 March 2022 17 Hemolysis on SBA Capsule demonstration

18. Gram negative cocci Neisseria meningitidis Capsulated GN diplococci, lens shaped Virulence factors – polysaccharide capsule, endotoxin Cl. Manifestations – pyogenic meningitis, septicemia LD – CSF, blood, NPS Treatment – 3 rd gen cephalosporins Neisseria gonorrhoeae STD – gonorrhea Virulence factors – pili, OMP Cl. Manifestations – mucopurulent cervicitis, urethritis, conjunctivitis LD – GN intracellular kidney shaped diplococci Culture- Thayer Martin medium, modified NYC medium Treatment – ceftriaxone DOC Both partners to be treated 16 March 2022 18

19. 16 March 2022 19 N.meningitidis N.gonorrheae

20. Gram positive bacilli Corynebacterium diphtheriae Diphtheria Virulence – diptheria toxin Cl. Manifestations – tough leathery greyish white pseudomembrane over tonsils LD – throat swab Albert staining – Chinese letter pattern Culture – Loeffler’s medium Toxin demonstration – Elek’s test Treatment – ADS, penicillin Vaccine available 16 March 2022 20

21. 16 March 2022 21 Pseudo membrane Elek’s test Chinese letter pattern

22. Bacillus anthracis Anthrax Zoonotic disease Cutaneous anthrax Pulmonary anthrax Intestinal anthrax LD – long chains of GPB, non bulging spores Treatment – Ciprofloxacin / Doxycycline - DOC 16 March 2022 22

23. Mycobacterium tuberculosis Transmission Pathogenesis Clinical forms – Pulmonary / Extra pulmonary LD – Ziehl Neelsen staining Culture Molecular Treatment Resistance Vaccine 16 March 2022 23

24. Miscellaneous Gram positive bacilli Actinomycetes Listeria Erysipelothrix rhusiopathiae Tropheryma whipplei 16 March 2022 24

25. Gram negative bacilli infections Enterobacteriaceae GNB, non fastidious, catalase positive, oxidase negative , etc Called coliforms Escherichia coli, Klebsiella, Proteus Shigella, Salmonella Lactose fermenters Non lactose fermenters 16 March 2022 25

26. Escherichia coli Urinary tract infections Diarrhea Abdominal infections, pneumonia, meningitis, wound and soft tissue infections LD – LF pink colonies on MacConkey agar Treatment – cephalosporins, quinolones, etc. Majority MDR – higher antibiotics 16 March 2022 26

27. 16 March 2022 27 LF – pink, NLF - pale

28. Klebsiella pneumoniae UTI Lobar pneumonia Meningitis Septicemia Abscesses and wound infections 16 March 2022 28

29. Shigella Bacillary dysentery Loose stools mixed with blood 4 species Transmission – faeco oral route LD – stool culture Enrichment medium – selenite F broth 16 March 2022 29

30. Salmonella Typhoidal salmonella Non typhoidal salmonella Enteric fever Fever, headache, chills, rashes, abdominal pain Pathogenesis – faeco oral route LD – blood culture , etc 16 March 2022 30

31. 16 March 2022 31 Blood culture bottles

32. Other Enterobacteriaceae Enterobacter Proteeae Serratia Yersinia 16 March 2022 32

33. Vibrio cholerae Cholera – acute diarrheal disease Pathogenesis – faeco oral route, cholera toxin LD – stool for hanging drop, stool culture Treatment – fluid replacement Halophilic vibrios – higher salt concentration 16 March 2022 33

34. Non fermenting Gram negative bacilli Do not ferment any carbohydrates Pseudomonas aeruginosa Causes infections in hospitalized patients Pathogenesis – due to resistance to multiple antibiotics and disinfectants , virulence factors Cl manifestations – HAIs , burn wound infections LD – GNB, oxidase positive Treatment – antipseudomonal antibiotics 16 March 2022 34

35. Acinetobacter spp Saprophytes Widespread HAIs Spectrum of infections same as Pseudomonas 16 March 2022 35

36. Burkholderia species Burkholderia cepacia Burkholderia pseudomallei 16 March 2022 36

37. Fastidious Gram negative bacilli Haemophilus species H.influenzae H.ducreyi HACEK group Bordetella pertussis Brucella species 16 March 2022 37

38. Miscellaneous Gram negative bacilli Campylobacter Helicobacter pylori Legionella Gardnerella vaginalis Streptobacillus moniliformis 16 March 2022 38

39. Anaerobic bacterial infections Clostridium species Clostridium perfringens Clostridium tetani Clostridium botulinum Clostridiodes difficile Non sporing anaerobes Bacteroides 16 March 2022 39

40. Miscellaneous bacterial infections Spirochetes – Treponema, Borrelia, Leptospira Treponema pallidum STD – Syphilis Stages – Primary, Secondary, Late Lab diagnosis 16 March 2022 40

41. Borrelia spp Relapsing fever, Lyme disease, etc. Leptospira L.interrogans – Leptospirosis zoonotic 16 March 2022 41

42. Rickettsia and Orientia Obligate intracellular parasites Not cultivable in artificial media 16 March 2022 42

43. Chlamydiae Obligate intracellular bacteria Chlamydia trachomatis – keratoconjunctivitis , infant pneumonia, LGV (STD) Chlamydophila psittaci – bird pathogen. Atypical pneumonia to humans Chlamydophila pneumoniae – atypical pneumonia Mycoplasma Lack cell wall Resistant to beta lactam antibiotics M.pneumoniae – Primary atypical pneumonia (community acquired) DOC - Macrolides 16 March 2022 43

44. Summary Gram positive cocci Gram negative cocci Gram positive bacilli Gram negative bacilli Miscellaneous bacteria 16 March 2022 44

45. References Essentials of Medical Microbiology - Apurba Sastry World wide web 16 March 2022 45

46. Thank you! 16 March 2022 46