A microbiological perspective about the common organism causing Endophthalmitis

1. BACTERIA CAUSING
ENDOPHTHALMITIS
A Microbiological perspective of Ocular Micro-organisms

2. BACTERIA
GRAM POSITIVE
BACTERIA
COCCI BACILLI
SPOREFORMING
NON
SPOREFORMING
GRAM NEGATIVE
BACTERIA
COCCI RODS
ACID-FAST
BACTERIA
CLASSIFICATION OF BACTERIA

3. ORGANISMS CAUSING ENDOPHTHALMITIS
Safneck J. R. Endophthalmitis: a review of recent trends. Saudi
Journal of Ophthalmology. 2012;26(2):181–189

4. CLASSIFICATION OF ENDOPHTHALMITIS
Kernt M, Kampik A. Endophthalmitis: pathogenesis, clinical presentation,
management, and perspectives. Clin Ophthalmol. 2010;4:121–35

5. GRAM POSITIVE

6. STAPHYLOCOCCUS

7. INTRODUCTION
 Staphyloccocci - derived from Greek “stapyle” (bunch of
grapes)
 Gram positive cocci arranged in clusters
 Non spore forming, non motile
 Catalase positive (breaks H2O2 into O2 & H2O)
 S. aureus: Coagulase positive, Hemolytic, Ferments
Mannitol.
 Plasmid mediated Antibiotic resistance in S. aureus

8. GROUPING
 1. Coagulase positive Staphylococci
 Staphylococcus aureus
 2. Coagulase negative Staphylococci
 Staphylococcus epidermidis
 Staphylococcus saprophyticus

9. STAPHYLOCOCCUS AUREUS
 Major human pathogen
 Habitat - part of normal flora in some humans (nose ,
sometimes skin esp hospital staff and patients, vagina of
5% females) and animals
 Source of organism - can be infected human host, carrier,
fomite or environment

10. STAPHYLOCOCCUS EPIDERMIDIS
 Skin commensal, Coagulase negative.
 Has predilection for plastic material
 Associated with infection of IV lines, prosthetic heart
valves, shunts
 Has variable antibiotic sensitivity pattern, highly resistant
 Treatment should be aided with drug sensitivity test.
 Hospital acquired

11. DISEASES
Due to direct
effect of organism
 Local lesions of skin
 Deep abscesses
 Systemic infections
Toxin mediated
effect
 Food poisoning
 toxic shock syndrome
 Scalded skin syndrome

12.  Protein A (binds to Fc
portion of Ig G at
complement binding
site)
 Teichoic acid
(adherence,
antibody formation)
 Microcapsule (11
serotypes)
 Peptidoglycan has
endotoxin-like
properties.
CELL WALL COMPONENTS &
ANTIGENS OF S.AUREUS

13. DIAGNOSIS
1. In all pus forming lesions
 Gram stain and culture of pus
2. In all systemic infections
 Blood culture
3. In infections of other tissues, Culture of relevant tissue
or exudate
4. Gram Stain: Gram positive cocci in clusters
5. Yellowish colonies , b-hemolytic on Blood agar
6.Catalase and coagulase positive
7. Mannitol fermenter

14. DIAGNOSIS (Continued)

15. ANTIBIOTIC SENSITIVITY PATTERN
 Very imp. In Pt. Management
 Mechanisms of antibiotic resistance
 1.B lactamase production - plasmid mediated
Has made S. aureus resistant to penicillin group of
antibiotics (90% of S. aureus (Gp A))
B lactamase stable penicillins (cloxacillin, oxacillin,
methicillin) used
 2. Alteration of penicillin binding proteins (Chromosomal
mediated)

16. MRSA
 Tested in lab using methicillin
 Referred to as methicillin resistant S. aureus (MRSA)
 Emerging problem in the world
 In Sri Lanka prevalence varies from 20- 40% in
hospitals
 Drug of choice - VANCOMYCIN
 In Japan emergence of VIRSA (vancomycin
intermediate resistant S. aureus)
 No effective antibiotics discovered -We might have to
discover

17. STAPHYLOCOCCAL ENDOPHTHALMITIS
 Presentation: Staph aureus is mostly acute, explosive in
onset, CONS is indolent and insidious in onset
 Mode of entry into eye: Most common organism in post
surgical endophthalmitis, enters the eye via surgical
wounds (SICS tunnel, corneal incisions)
 Clinical picture: Hypopyon in AC with dense vitritis.

18. FACTORS PREDISPOSING TO S. AUREUS
ENDOPHTHALMITIS
 At transcriptional level, namely, agr (accessory gene
regulator) and sar (staphylococcal accessory
regulator)
 Alpha toxin (tissue necrosis) and beta-toxin
contributed to the decrease in retinal function.
 Gamma-toxin and leukocidin, were highly toxic
when injected intravitreally, causing significant
retinal destruction and inflammation
Bacterial Endophthalmitis: Epidemiology, Therapeutics, and Bacterium-Host
Interactions. Michelle C. Callegan et al. Clin. Microbiol. Rev. January 2002 vol. 15
no. 1 111-124

19. PNEUMOCOCCUS

20. INTRODUCTION
 Gram positive encapsulated (polysaccharide)
flame/lancelate shaped diplococci
 Bile soluble , optochin sensitive
 Aerobes/ F. anaerobes
 Normal upper resp. tract flora
 Common cause of pneumonia & OM in children

21. IMPORTANT PROPERTIES
 Draughtsman colonies
 Normally alpha hemolysis, but Beta hemolysis under
anaerobic conditions due to pneumolysin O
 Inulin fermentation positive and sensitive to Optochin (5
µg)
 Capsular polysaccharide (90 types) (Vaccine most
common 23 types)

22. IMPORTANT PROPERTIES (Continued)
 M – protein : Non – virulent, strain specific.
 C substance – species specific, precipitated by abnormal
protein and present in acute infections, injury. Acute
phase reactant – CRP, is produced by hepatocytes.
 Quellung (Neufeld reaction) : Pneumococci + antisera
under Methylene Blue = Capsular swelling ( due to
increase in refractive index)

23. PATHOGENICITY
 Most common cause of bacterial
pneumonia
 Lobar pneumonia – adults (Strains
1-12), children (Strains 6,14,19,23)
 Bronchopneumonia – almost always
secondary infection (all serotypes)
 2nd commonest cause of meningitis
 Pharynx blood stream meninges
 Empyema, pericarditis,
conjunctivitis, endophthalmitis
etc.

24. LAB DIAGNOSIS
 Sample – CSF, Sputum, exudates
 Immediately transfer or keep at 37°C
 Direct microscopy or antigen detection by Latex
Agglutination Test or co-agglutination)
 Blood Agar culture at 37° incubator for 18 – 24 hours.
 Colonies – alpha hemolysis, Gram staining, Biochemical.
Rx (catalase, inulin fermentation, bile solubility, optochin)

25. India Ink Gram Stain
Quellung reaction

26. CULTURE

27. TREATMENT
 For penicillin sensitive strains, Penicillin is the drug of
choice, for milder cases Amoxicillin can be administered.
 For penicillin resistant strains, a third generation
cephalosporin is indicated.
 Vancomycin is reserved for life threatening illness with
highly resistant strains.

28. STREPTOCOCCUS ENDOPHTHALMITIS
 Presentation: Mostly Acute onset.
 Mode of entry: Most common route of entry for the micro-
organism is via the conjunctival bleb related
endophthalmitis, Intra vitreal injections
 Clinical picture: Infected white bleb, hypopyon, moderate
to dense vitritis.
Endophthalmitis Caused by Streptococcal Species: Clinical Settings, Microbiology,
Management, and Outcomes. Kuriyan AE et al. Am J Ophthalmol. 2014
Apr;157(4):774-780.e1

29. PROPIONIBACTERIUM ACNES

30. INTRODUCTION
 Propionibacterium species are members of the normal
microbiota of the skin, oral cavity, large intestine,
conjunctiva, and external ear canal.
 Their metabolic products include propionic acid, from
which the genus name derives.
 On Gram stain, they are highly pleomorphic, showing
curved, clubbed, or pointed ends; and occasionally
coccoid or spherical forms.
 Obligate anaerobes

31. DISEASE SPECTRUM
 Propionibacterium acnes, an opportunistic pathogen,
causes the disease acne vulgaris
 It causes acne by producing lipases that split free fatty
acids off from skin lipids. These fatty acids can produce
tissue inflammation.
 P acnes is frequently a cause of postsurgical wound
infections,

32. AIDES IN DIAGNOSIS
 Foul-smelling discharge (caused by short-chain fatty-acid
products of anaerobic metabolism)
 Infection in proximity to a mucosal surface (anaerobes are
part of the normal microbiota)
 Gas in tissues (production of CO2 and H2)
 Negative aerobic culture results

33. CULTURE
 Anaerobes grow most readily on complex media such as
trypticase soy agar base, Schaedler’s blood agar,
Brucella agar, brain–heart infusion agar, & highly
supplemented media (eg, with hemin, vitamin K1, blood).
 A selective complex medium containing kanamycin is used
in parallel.
 Kanamycin does not inhibit the growth of obligate
anaerobes; thus, it permits them to proliferate without
being overshadowed by rapidly growing facultative
anaerobes.
 Cultures are incubated at 35–37°C in an anaerobic
atmosphere containing CO2.

34. TREATMENT
 The most active drugs for treatment of anaerobic
infections are clindamycin and metronidazole.
Clindamycin is preferred for infections above the
diaphragm.
 Alternative drugs include cefoxitin, cefotetan, some of
the other newer cephalosporins, and piperacillin.
 The carbapenem antibiotics, ertapenem, imipenem,
meropenem, and doripenem, have good activity against
many anaerobes, and resistance is still uncommon.

35. TREATMENT (Continued)
 Tigecycline, has good in vitro activity against a variety of
anaerobe species, including the B fragilis group.
 Penicillin G remains the drug of choice for treatment of
anaerobic infections that do not involve β-lactamase–
producing Bacteroides and Prevotella species.

36. PROPIONIBACTERIUM ACNES
ENDOPHTHALMITIS
 Presentation: Chronic indolent, delayed presentation
 Mode of entry: Predilection for capsular bags, a localized
infection can become endophthalmitis post YAG
capsulotomy
 Clinical picture: White intracapsular plaque slowly
growing associated with low grade anterior segment
inflammation and vitritis.

37. BACILLUS CEREUS

38. INTRODUCTION
 The genus Bacillus includes large aerobic, gram-positive
rods occurring in chains.
 B cereus can grow in foods and cause food poisoning by
producing either an enterotoxin (diarrhea) or an emetic
toxin (vomiting).
 The emetic form is manifested by nausea, vomiting,
abdominal cramps, and is self-limiting.
 The diarrheal form is manifested by profuse diarrhea
with abdominal pain and cramps.

39. INFECTIVE SPECTRUM OF B cereus
 B cereus is an important cause of eye infections, such as
severe keratitis and endophthalmitis.
 Typically, the organisms are introduced into the eye by
foreign bodies associated with trauma but infections can
also occur after surgery.
 B cereus has also been associated with localized
infections, such as wound infections, and with systemic
infections, including endocarditis, the presence of a
medical device or intravenous drug use predisposes to
these infections

40. IDENTIFICATION & CULTURE
 The typical cells, measuring 1 x 3–4 μm,
have square ends and are arranged in long
chains; spores are located in the center of
the bacilli.
 Hemolysis is common with B cereus. Gelatin
is liquefied, and growth in gelatin stabs
resembles an inverted fir tree.
 When grown on blood agar plates, the
organisms produce nonhemolytic gray to
white, tenacious colonies with a rough
texture and a ground-glass appearance.
 Comma-shaped outgrowths (Medusa head,
“curled hair”) may project from the colony
 Gram stain shows large gram-positive rods.
B cereus exhibit motility by “swarming.”

41. TREATMENT
 Serious non–food borne infections should be treated with
vancomycin or clindamycin with or without an
aminoglycoside.
 Ciprofloxacin has been useful for the treatment of wound
infections.

42. BACILLUS CEREUS ENDOPHTHALMITIS
 Presentation: Acute explosive onset, post traumatic,
rapidly progressing
 Mode of entry: Most common risk factor is penetrating
ocular trauma
 Clinical picture: Sudden onset, rapidly progressing with
corneal ring abscess associated with systemic involvement
like fever, leukocytosis and malaise.

43. Bacillus cereus endophthalmitis. DB David et al. British Journal
of Ophthalmology 1994; 78:577-580

44. FACTORS PREDISPOSING TO B CEREUS
ENDOPHTHALMITIS
 B cereus pore forming toxin Hemolysin BL is a tripartite
toxin, with hemolytic, dermonecrotic, and emetic
activities
 B. cereus supernatants caused retinal tissue damage in an
in vitro retinal button toxicity assay.
 Cereolysin AB, Cereolysin O, or collagenase could be
involved in endophthalmitis pathogenesis.
Bacterial Endophthalmitis: Epidemiology, Therapeutics, and Bacterium-Host
Interactions. Michelle C. Callegan et al. Clin. Microbiol. Rev. January 2002 vol. 15
no. 1 111-124

45. GRAM NEGATIVE

46. PSEUDOMONAS

47. INTRODUCTION
 A large group of aerobic, non sporing gram negative
bacteria motile by polar flagella
 Widely distributed in soil and water
 Gram negative rods
 Aerobic, Motile, Produce water-soluble pigments
 It is pathogenic only when introduced into areas devoid of
normal defenses

48. MORPHOLOGY
 They are slender gram negative bacillus, 1.5 – 3
microbes x 0.5 microns
 Mono-flagellar
 Non capsulated but many strains have mucoid slime layer
 Isolates from Cystic fibrosis patients have abundance of
extracellular polysaccharides composed of alginate
polymers
 Escape the defence mechanisms by loose capsule in
which micro colonies of bacillus are enmeshed and
protected from host defences.

49. CULTURE
 Obligate aerobe, but grow
anaerobically if nitrate is available
 Growth occurs at wide range of
temperatures 6-42⁰C the optimum
being 37⁰C
 Growth on ordinary media
producing large opaque irregular
colonies with distinctive musty
mawkish or earthy smell.
 Iridescent patches with metallic
sheen are seen in cultures on
nutrient agar.
 Oxidase, Catalase & Arginine
positive
 Nonfermentative respiratory
metabolism. Glucose used
oxidatively.

50. RESISTANCE
 Killed at 55⁰C in on 1 hour. High resistance to chemical
agents
 Resistance to quaternary ammonium compounds
(eg.Chlorxylenol) Resistant to Hexchlorophenes
 Grows also in antiseptic bottles. Hence Dettol, cetrimide
can be used as selective medium
 Sensitive to acids silver salts, beta glutaraldehyde

51. PATHOGENESIS AND IMMUNITY
 P. aeruginosa can infect almost any external site or organ.
 P. aeruginosa is invasive and toxigenic. It attaches to and
colonizes the mucous membrane or skin, invade locally,
and produces systemic diseases and septicemia.
 P. aeruginosa is resistant to many antibiotics. It becomes
dominant when more susceptible bacteria of the normal
flora are suppressed.
 Individuals with cystic fibrosis are highly susceptible to
pseudomonas lung infections as well as those people who
are immunocompromised.

52. CLINICAL PRESENTATION
 Septicaemia
 Endocarditis
 Ecthyma gangrenous
 Infantile diarrhoea
 Shanghai fever
 Disabling eye infections

53. TOXINS & ENZYMES
 Toxic extracellular products in culture filtrates
 Exotoxin A and S
 Exotoxin A acts as NADase resembling Diphtheria toxin
 Proteases, elastases, hemolysins and enterotoxin
 Slime layer and Biofilms

54. TREATMENT
 Pseudomonas aeruginosa is frequently resistant to many
commonly used antibiotics. Although many strains are
susceptible to gentamicin, tobramycin, colistin, and
amikacin, resistant forms have developed.
 The combination of gentamicin and carbenicillin is
frequently used to treat severe Pseudomonas infections.
 Combined antibiotic therapy is generally required to avoid
resistance that develops rapidly when single drugs are
employed.

55. PSEUDOMONAS ENDOPHTHALMITIS
 Presentation: Acute onset, rapid progression
 Mode of entry: Post cataract surgery, corneal ulcer
 Clinical picture: severe congestion, chemosis, ring ulcer
infiltrate of cornea (characteristic of Pseudomonas),
severe inflammation of anterior chamber and vitritis.
Endophthalmitis caused by Pseudomonas aeruginosa. Eifrig CW et al.
Ophthalmology. 2003 Sep;110(9):1714-7

56. COLIFORM SPP
Proteus, Klebsiella & Escherichia coli

57. INTRODUCTION
 Enterobacteriaceae are a large, heterogeneous group of
gram-negative rods whose natural habitat is the intestinal
tract of humans and animals.
 The Enterobacteriaceae are facultative anaerobes or
aerobes, ferment a wide range of carbohydrates, possess
a complex antigenic structure, and produce a variety of
toxins and other virulence factors.
 In this section, we are going to deal with the three most
important coliform spp. Proteus, Klebsiella and E.coli
which cause Endophthalmitis.

58. PROTEUS
 Proteus species produce infections in humans only when
the bacteria leave the intestinal tract. They are found in
urinary tract infections and produce bacteremia,
pneumonia
 Proteus species produce urease, resulting in rapid
hydrolysis of urea with liberation of ammonia, hence the
urine becomes alkaline, promoting stone formation.
 The rapid motility of Proteus may contribute to its
invasion of the urinary tract.

59. PROTEUS (Characteristics)
 Proteus species move very actively by means of
peritrichous flagella, resulting in “swarming” on solid
media
 The members of this group deaminate phenylalanine, are
motile, grow on potassium cyanide medium (KCN), and
ferment xylose.
 Proteus species are urease positive & ferments lactose
very slowly or not at all.
 Endophthalmitis caused most commonly following
intraocular surgeries or following corneal ulcer.

60. KLEBSIELLA
 Klebsiella pneumoniae is present in the respiratory tract
and feces of about 5% of normal individuals.
 K pneumoniae can produce extensive hemorrhagic
necrotizing consolidation of the lung. It produces urinary
tract infection and bacteremia with focal lesions in
debilitated patients.
 Klebsiella species rank among the top 10 bacterial
pathogens responsible for hospital-acquired infections.

61. KLEBSIELLA (Characteristics)
 Klebsiella species exhibit mucoid growth, large
polysaccharide capsules, and lack of motility
 It gives positive test results for citrate, and ornithine
decarboxylase and produce gas from glucose.
 Klebsiella gives positive Voges-Proskauer reactions.
 One of the most common cause of endogenous
endophthalmitis.
 Occurs most commonly in patients with Liver abscess,
uncontrolled Diabetes. Diabetes is a risk factor which
helps bacteria avoid phagocytosis(K1 and K2 serotypes)
Bacterial Endophthalmitis: Epidemiology, Therapeutics, and Bacterium-Host
Interactions. Michelle C. Callegan et al. Clin. Microbiol. Rev. January 2002 vol. 15
no. 1 111-124

62. ESCHERICHIA COLI
 E coli are members of the normal intestinal microbiota.
 The enteric bacteria generally do not cause disease, and
in the intestine, they may even contribute to normal
function and nutrition
 When normal host defenses are inadequate, E coli may
reach the bloodstream and cause sepsis.
 Newborns may be highly susceptible to E coli sepsis
because they lack IgM antibodies. Sepsis may occur
secondary to urinary tract infection
 E coli is one of the leading causes of meningitis in infants.

63. ESCHERICHIA COLI (Characteristics)
 Typical colonial morphology with an iridescent “sheen” on
differential media such as EMB agar, and a positive spot
indole test result.
 More than 90% of E coli isolates are positive for β-
glucuronidase.
 E coli associated endophthalmitis occurs in patients with
septicemia and immuno-compromised status. Associated
risk factors include endocarditis, body abscesses.

64. ANTIGENIC STRUCTURE
(Of Enterobacteriaceae)
 Enterobacteriaceae have a complex
antigenic structure,
 O antigens are the most external part of
the cell wall lipopolysaccharide and
consist of repeating units of
polysaccharide.
 K antigens are external to O antigens on
some but not all Enterobacteriaceae. K
antigens may interfere with
agglutination by O antisera, and they
may be associated with virulence.
 H antigens are located on flagella and
are denatured or removed by heat or
alcohol.

65. TREATMENT
 The sulfonamides, ampicillin, cephalosporins,
fluoroquinolones, and aminoglycosides have marked
antibacterial effects against the enteric bacteria.
 Treatment of gram-negative bacteremia and impending
septic shock requires rapid institution of antimicrobial
therapy, restoration of fluid and electrolyte balance, and
treatment of disseminated intravascular coagulation.

66. RARE BACTERIAS INVOLVED IN
ENDOPHTHALMITIS

67. NOCARDIA
 Nocardia are gram-positive, weakly acid-fast, aerobic,
non-motile, branching filamentous bacteria
 Systemic nocardiosis commonly occurs in
immunosuppressed patients (post-transplant, medicated
with systemic steroids, malignancies, AIDS) by inhalation
 Endogenous nocardial endophthalmitis usually presents
as choroidal lesions and thickened overlying retina with
little or no vitreous inflammation.
 Exogenous endophthalmitis occurring after intra-ocular
surgery or penetrating trauma is commonly confined to
the anterior segment with characteristic yellowish-white
iris nodules, corneal endothelial deposits and a
hypopyon with involvement of wound.

68. NOCARDIA (Contd;)
 The mainstay of treatment of Nocardia endophthalmitis is
appropriate antibiotics.
 Co-trimoxazole remains a good first line of therapy till
the culture and susceptibility report are ready.
Additionally, this drug has shown fairly good intra-ocular
penetration
 Non-response may require the use of amikacin,
ciprofloxacin or newer antibiotics such as imipenem and
linezolid.
 Use of corticosteroids still controversial with views of
converting acute infection into a chronic smoudlering
infection.

69. NOCARDIA ENDOPHTHALMITIS

70. CORYNEBACTERIUM
 Corynebacterium is a genus of pleomorphic gram-
positive bacilli or coccobacilli that is ubiquitous in the
environment.
 Corynebacterium species associated with trauma,
cataract surgery, and endogenous sources, also been
identified in cases of scleral buckle associated
infections
 Mean duration of presentation is 7 months.
 Presents with severe anterior segment inflammation
with hypopyon.
 Prompt response to Vancomycin and Ceftazidime
Endophthalmitis Caused by Corynebacterium Species: Clinical Features,
Antibiotic Susceptibility, and Treatment Outcomes. AE Kuriyan et al.
Ophthalmology Retina 2016;-:1e6

71. NON TUBERCULOUS MYCOBACTERIUM
 NTM are aerobic, non-motile, non-spore forming, rapid
growing, acid fast bacilli which are widespread in
environment.
 The most common species isolated from patients with
endophthalmitis are Mycobacteria fortuitum and
Mycobacteria chelonae.
 Immunocompromised states & presence of an implant in
or around the have been reported as risk factors. The
presence of an implant may act as a scaffold for the
formation of biofilm by non-tuberculous
mycobacterium.
 Endophthalmitis manifests with low grade ocular
inflammation

72. NON TUBERCULOUS MYCOBACTERIUM
(Contd;)
 Ziehl Neelsen (ZN) staining or polymerase chain reaction
(PCR) help in early identification of these organisms
 Amikacin, clarithromycin, and/ or azithromycin have
been considered to be the best antibiotics
 Treatment with pars plana vitrectomy, removal of implant
(intraocular lens, glaucoma implant or scleral buckle),
serial intravitreal amikacin and systemic
azithromycin/clarithromycin (oral) is recommended.

73. BURKHOLDERIA CEPACIAE
 Burkholderia cepacia complex (Bcc) is a multispecies
complex of bacteria that commonly causes respiratory
infections in persons with cystic fibrosis
 Most common organism associated with contamination of
sterile pharmaceutical products like contaminated nasal
sprays, ultrasound gel, mouthwash and nebulisation
solution
 Presentation is acute with congestion, chemosis, anterior
chamber inflammation and moderate vitritis.
 BOX-PCR fingerprinting and Blood agar growth used to
identify the organism

74. (Contd;)
 Persistence of infections is very common with this
organism due to its intrinsic multidrug resistance nature.
 The organisms are started on combination antibiotics of
Piperacillin/Tazobactam topically and intra-vitreally and
considered for early vitrectomy.
Lalitha P, Das M, Purva PS, et al; Postoperative endophthalmitis due to Burkholderia
cepacia complex from contaminated anaesthetic eye drops British Journal of
Ophthalmology 19 June 2014