riginal Article
Etiology and Antimicrobial
Susceptibility Pattern of Bacterial Keratitis at a Tertiary Care Hospital
Fahd Kamal Akhtar, Zubair Saleem,
Muna Malik, Adeel Chaudhary, Ayesha Sajjad, Abdul Mudabbir Rehan
DOI 10.36351/pjo.v35i4.928 Pak J Ophthalmol 2019, Vol. 35, No. 4
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See end of article for authors affiliations …..……………………….. Correspondence to: Dr. Muna Malik Department of Pathology LGH, Lahore Email: mmkamboh@hotmail.com |
Purpose: To find out the etiology and antimicrobial susceptibility
pattern of bacterial keratitis at a tertiary care hospital in Lahore. Study Design: Descriptive cross sectional study. Place and Duration of Study: Postgraduate Medical Institute/Ameer ud Din
Medical College/Lahore General Hospital, Lahore, from 2015 – 2018. Material and Methods: Clinically suspected patients of bacterial keratitis were
selected from out patient department of Lahore General hospital and corneal
scrapings were collected before start of antimicrobial therapy. Patients who
were already on antimicrobial therapy and patients with suspected keratitis
caused by micro-organism other than bacteria were excluded from the study.
The corneal scrapings taken by the ophthalmologist were immediately
inoculated on different culture plates with the help of sterilized wire loop
in the operation theater. These plates were taken to the laboratory for
incubation and further microbiological processing. The scrapings from cornea
were also smeared on glass slides with the help of sterilized wire loop for
staining. The culture and staining were further processed for microbiological
analysis of bacterial etiology and antimicrobial susceptibility. Results: A total
of 65 corneal scrapings were done out of which 25 were positive for bacterial
growth. Seven cases were positive for Staphylococcus and Streptococcus
pneumoniae species each, 5 were Pseudomonas, 3 were Klebsiella, 2 were
Acinetobacotar & one was Nocardia. Gram
negative bacteria were relatively more sensitive to all groups of antibiotics
as compared to Gram positive bacteria. Conclusion: Staphylococcus
and Streptococcus pneumoniae species are the commonest cause of bacterial
keratitis in our setup. Key words: Bacterial keratitis, Pseudomonas,
culture, gram staining. |
Bacterial keratitis accounts for about 90%
of all reported infective keratitis cases1. Bacterial keratitis
causes can cause severe corneal infection and is one of the leading causes of visual
loss2. It usually progresses when the ocular defense has been
compromised either by trauma, contact lens or ocular surface diseases3.
Development of bacterial keratitis is speedy,
so need of the hour is to treat it as a medical emergencyand treatment should
be initiated promptly with empirical antibiotics4. However, if this
infection is left untreated it may end up in corneal perforation,
endophthalmitis and permanent visual loss5. The prompt diagnosis of
the causative organism can be done by performing culture. Cultures also provide
evidence about antibiotic sensitivity and information regarding prognosis of
the disease6.
Gram-positive cocci like Staphylococcus
species and Streptococcus pneumonia are the commonest bacterial pathogens
causing infective keratitis7. Among Gram-negative-bacteria,
Pseudomonas species is the most common cause, other Gram-negative bacteria are
Escherichia coli, Proteus species and Klebsiella pneumonia5,8.
When bacterial flora gain access in immune-compromised
eye due to trauma, eye surgery, usage of contact lens or any other eye
infections, it leads to corneal infection9. Different bacteria have
different virulence factors for adhesion and pathogenesis and they will help
them in causing keratitis. Lipopolysaccharides of Gram-negative bacteria play
an important role as a virulent agent in infectious keratitis10. The
proteases cleave collagen of the corneal stromal tissue and hence they cause
obliteration of cornea11. The strength of this inflammatory response
and the damage associated with it is variable depending on the pathogenic
microorganisms and the severity of infection they cause12.
For ophthalmologists bacterial
culture is crucial in determining the pathogens of keratitis, as clinical
appearance of infection sometimes appears to be unreliable. Thus, the purpose of
the study was to isolate bacterial etiology of infective keratitis and its
antimicrobial susceptibility pattern in Pakistan. This will facilitate
clinicians in our setup for diagnosis of infective keratitis and its treatment.
MATERIAL AND METHODS
This study was conducted in the
Ophthalmology Department of Lahore General hospital, Lahore from 2015 to 2018. Institutional
review board approved the study. The clinically suspected patients of Infective
keratitis were selected and corneal scrapings were collected before start of antimicrobial
therapy. Patients who were already on antimicrobial therapy and patients with
suspected keratitis caused by micro-organism other than bacteria were excluded
from the study. Corneal scrapings were collected from 65 patients by
ophthalmologist in operation theater of Eye department, Lahore General
Hospital, Lahore. The patient’s name, sex, age, date of collection, brief
clinical history including onset, history of trauma/ corneal foreign body,
duration and any other corneal problems were asked and recorded. Xylociane was instilled
in the eye to anesthetize the cornea. The necrotic tissue and loose mucus was
detached from the surface of the ulcer. The margins and base of the ulcer were
scraped by disposable scalpel blade no 15.
Corneal scrapings taken by the ophthalmologist
were immediately inoculated on Chocolate agar, Blood agar and MacConkay agar
culture plates with the help of sterilized wire loop in the operation theater. These
plates were taken to laboratory for incubation and further microbiological processing.
Chocolate Agar was used for isolation of
fastidious bacteria particularly H. influenza, Neisseria spp. and Moraxella
spp. The agar plates were incubated in carbon dioxide (CO2) enriched
atmosphere in candle jar at 37˚C for 24 hours. Blood Agar was used for isolation
of non-fastidious bacteria. The plates were incubated aerobically at 37˚C
for 24 hours. Any growth on culture agar plate was assessed visually. The
cultural characteristics of individual colonies like size, shape, surface,
color, consistency, elevation, pigment production, presence or absence of
hemolysis was noted on blood agar. Staphylococcus aureus and Streptococcus
pneumonia were the commonest bacteria. Macconkay Agar was used for isolation of
Gram-negative bacteria. The plates were incubated aerobically at 37˚C for
24 hours. Any growth on culture plate was assessed visually for, lactose
fermenters and non-fermenters. Most commonly isolated Gram-negative bacterium
was Pseudomonas spp. The identified bacteria were tested for their antimicrobial
susceptibility pattern according to Clinical and Laboratory standards institute
(CLSI).
After inoculating on the
culture agar plates, the scrapings from cornea were smeared on glass slides
with the help of sterilized wire loop. The smears were air-dried, stained with
Gram’s stain, Kinyoun stain and Giemsa stain. Grams staining was used to
identify Gram positive and Gram-negative bacteria. Giemsa was used to see the
inclusion bodies of Chlamydia trachomatis in infected epithelial cells.
Bacteria was stained dark blue bacilli or cocci. Inflammatory cells were differentiated
into mononuclear and polymorphs cells. Kinyoun staining was used for identification
of Nocardia spp. It appeared as weak acid fast branching filaments. They also
stained as Gram-positive branching filaments.
RESULTS
In our study, total 65
corneal scrapings were done. Out of these 65 samples only 25 were positive for bacterial
growth culture. Out of 25, 7 were positive for growth of Staphylococcus spp, 7 were
cases of Streptococcus pneumonia, 5
were Pseudomonas, 3 were Klebsiella, 2
were Acinetobacotar & one was Nocardia. were identified. Rest of
the results are shown in figure 1, 2, 3 and table 1.
Fig. 1: Frequency of bacteria isolated from corneal scrapings.
Table 1: Cumulative antimicrobial susceptibility data of Klebsiella spp,
Pseudomonas spp. and Acinetobacter spp. Isolated from patients of infective
keratitis.
|
Antibiotics |
% Age of Sensitivity |
||
|
Klebsiella
spp. N
= 3 |
Pseudomonas
spp. N
= 5 |
Acinetobacter Spp.
N = 2 |
|
|
Amoxicillin-clavulanicacid 30µg |
70% |
-- |
-- |
|
Ceftazidime 30 µg |
90% |
90% |
70% |
|
Cefotaxime 30 µg |
80% |
-- |
70% |
|
Ceftraiaxone 30 µg |
80% |
-- |
70% |
|
Cefepime 30 µg |
90% |
90% |
80% |
|
Cefaperazone-salbactam |
100% |
100% |
100% |
|
Sulphamethoxazole trimethoprim |
80% |
-- |
80% |
|
Gentamicin 10 µg |
100% |
90% |
100% |
|
Tobramycin µg |
100% |
100% |
100% |
|
Amikacin 30 µg |
100% |
100% |
100% |
|
Ciprofloxacin 30 µg |
90% |
80% |
90% |
|
Levofloxacin 30 |
90% |
90% |
90% |
|
Imepenem |
100% |
100% |
100% |
|
Meropenem |
100% |
100% |
100% |
|
Pipercillin- tazobactam |
100% |
100% |
100% |
|
Piperacillin |
-- |
90% |
100% |
|
Ampicillin- salbactam |
-- |
-- |
100% |
|
Doxycyclin |
90% |
90% |
100% |
Fig. 2: Antimicrobial susceptibility pattern of Satphlylococcus spp
isolated from corneal scrapings.
Fig. 3: Antimicrobial sensitivity of Streptococcus pneumoniae isolated
from corneal scrapings.
DISCUSSION
In our present study we found spectrum of bacterial microrganisms which
were isolated from the cultures of corneal scrapings at the microbiology
laboratory of a tertiary care hospital. In our study the most frequent bacteria
which were isolated from corneal scrapings were Staphylococcus aureus and
streptococcus spp., which is similar to the studies conducted in Sans
Francisco, which reported upto 45% of Staphylococcus
aureus in their study13. Moreover, many studies on infective
keratitis also reported Pseudomonas spp., Acinetobacter spp. and klebsiella
spp. as pathogens of microbial keratitis, which is similar to our results10.
Antimicrobial resistance has turned out to
be one of the chief community health extortions of the 21st century.
In a so-called “post-antibiotic” era it has become mandatory for clinicians to
be sensible in the use of antibiotics to treat infections. Nowadays a trend of
resistance against commonly given empirical antibiotics for treating keratitis has
been documented, which includes fluoroquinolones and fortified antibiotics,
often a combination of a cephalosporin or glycopeptide and aminoglycoside (e.g.
ceftazidime or vancomycin and tobramycin or gentamicin)14,15.
In our study we observed relatively less
resistance among gram negative bacteria against antimicrobial agents. Only 3rd
generation cephalosporins showed 30% of resistance. While other groups of
antimicrobial agents were upto 90% sensitive. It is good for prognosis of
infective keratitis treatment, which is also similar to the study conducted by Tiawan,
in which most of the Gram negative bacteria causing keratitis were sensitive to
antibiotics16. These antimicrobial therapeutic agents are
not only used to eradicate the causative bacteria but also used to prevent
irreversible destruction caused by enzymes and toxins of bacteria. However, the
resistance among Gram positive bacteria like Staphylococcus spp. and Sterptococcus
spp. against fluoroquinolones and aminoglycosides was 30%. It is similar to the
observation done in a Bangladeshi study on Antibiotic susceptibility pattern of bacteria isolated from corneal ulcer17. Streptococcus pneumoniae was relatively
more resistant as compared to Staphlococcus species. However, in contrast to
our study, a study conducted in Sydney reported no resistance in Streptococcus
pneumoniae isolated from corneal scrapings.18 Melbourne therapeutic
guidelines showed no role of Oral or intravenous antibiotics in the management of
uncomplicated bacterial keratitis19. However, it should be kept in mind
that susceptibility patterns change according to climate and geographical
region and can fluctuate from time to time20.
In our study we were
limited to further investigate the susceptibility pattern changes according to
the climate and geographical variation from time to time.
CONCLUSION
Staphylococcus and
Streptococcus pneumoniae species are the commonest cause of bacterial keratitis
in our setup.
CONFLICT OF INTEREST
None.
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Author’s
Affiliation
Fahd Kamal Akhtar
Senior Registrar,
Department of Ophthalmology, LGH, Lahore.
Zubair Saleem
Associate Professor of
Ophthalmology, PGMI/AMC/ LGH, Lahore
Muna Malik
Assistant Professor of
Pathology, PGMI/AMC/LGH, Lahore
Adeel Chaudhary
Senior registrar,
Department of Ophthalmology, LGH, Lahore
Ayesha Sajjad
Assistant Professor of
Pathology, Amna Inayat Medical College, Lahore
Author’s
Contribution
Fahd Kamal Akhtar
Data acquisition and analysis, manuscript writing
and final review.
Zubair Saleem
Data acquisition and analysis, manuscript writing
and final review.
Muna Malik
Data acquisition and analysis, manuscript writing
and final review.
Adeel Chaudhary
Data acquisition and analysis, manuscript writing
and final review.
Ayesha Sajjad
Data acquisition and analysis, manuscript writing
and final review.