Letter to the
Editor
Professor Stefania Stefani
Increased biofilm-associated Carbapenem-resistant Acinetobacter-calcoaceticus-baumannii complex infections among the hospitalized patients in Kathmandu Model Hospital, Nepal
Shova
Bhandari1, Milan Kumar Upreti1, Khadga Bikram Angbuhang1,
Basudha Shrestha2, Upendra Thapa Shrestha3 *
1GoldenGate International College, Battisputali, Kathmandu Nepal
2Kathmandu Model Hospital, Kathmandu, Nepal
3Central Department of Microbiology, Tribhuvan University, Kirtipur,
Kathmandu, Nepal
*Corresponding author: Upendra Thapa
Shrestha, Assistant Professor, Central Department of Microbiology, Tribhuvan
University, Kirtipur, Kathmandu, Nepal, Email: upendrats@gmail.com / upendra.thapashrestha@cdmi.tu.edu.np
Dear Editor
Acinetobacter
calcoaceticus-baumannii complex (ACBC), a Gram-negative commensal bacterium,
often infects immunocompromised patients or patients with indwelling devices,
especially in the intensive care unit, and causes a wide range of hospital-acquired
infections, including respiratory tract infections, urinary tract infections,
bacteremia, sepsis, endocarditis, meningitis, skin and soft tissue infections,
burns, as well as central and nervous system infections. A. baumannii is an emerging pathogen with the ability to produce a biofilm
that is mostly associated with ventilator-associated pneumonia and catheter-related
infections [1]. The bacteria inside the biofilm are shielded by extracellular polymeric substances,
which act as a barrier to antibiotics, leading the bacteria to antibiotic-resistance.
Biofilm-forming bacteria show 1000-fold higher drug resistance than planktonic
cells, and the infections caused by such bacteria are chronic, prone to relapse,
and more difficult to treat. In addition, within biofilm, the bacterial cells
are in close proximity and have a high chance of horizontal gene transfer,
particularly via conjugation of antibiotic resistance genes, promoting their
survival and the spread of antibiotic resistance [2].
Biofilm-related
virulence factors involved in A.
bauamnnii infections are biofilm-associated protein (Bap), the extended-spectrum beta-lactamase family blaPER1 gene, and CsuA/BABCDE
pilus usher-chaperone assembly system [3]. To address the biofilm-associated
carbapenem-resistant A. baumannii infections among hospitalized patients, we
conducted a hospital-based cross-sectional study at a tertiary care hospital in
Kathmandu, Nepal. We primarily determined the rate of A. baumannii in different clinical
specimens, and then we evaluated the association between biofilm formation and carbapenem-resistant
ACBC isolates detecting biofilm-forming
genes Bap, csuE, and blaPER1.
This
study was conducted at Kathmandu Model Hospital, Kathmandu, Nepal, from
February 2020 to August 2020 among hospitalized patients of all age groups who
gave written consent to be enrolled in the study (IRC 003-2020). A total of 665 different clinical
samples, including pus, sputum, tracheal aspirates, blood, endotracheal tips, catheter
tips, wound samples, suction tips, and tissue were processed using standard microbiological
procedures to isolate and identify the potential bacterial pathogens. The
antibiotic susceptibility pattern of ACBC was determined by a modified
Kirby-Bauer disk diffusion method following CLSI guidelines. The screening for
biofilm formation was done by the microtitre plate method [4]. And the biofilm-related virulence factors were
detected by using specific primers; bap-F (5’-TGCTGACAGTGACGTAGAACCACA-3’),
bap-R (5’-TGCAACTAGTGGAATAGCAGCCCA-3’), csuE-F (5’-CATCTTCTATTTCGGTCCC-3’),
csuE-R (5’-CGGTCTGAGCATTGGTAA-3’),
and blaPER1-F (5’- GCAACTGCTGCAATACTCGG-3’), blaPER1-R (5’-ATGTGCGACCACAGTACCAG-3’) [3]. The correlation between biofilm formation
and carbapenem resistance was analyzed using the Chi-Square test (SPSS version
22).
Out of 665 clinical
samples, bacterial growth was observed in 281 (42.3%). Escherichia coli (28.8%)
was the most predominant pathogen, followed by Staphylococcus aureus
(20.3%), Klebseilla pneumoniae (16.4%), ACBC (11.4%), and Pseudomonas
aeruginosa (8.1%). A significantly higher incidence of ACBC infection was
observed among the male patients (26/32; 81.3%). Similarly, the highest
incidence of ACBC infection was reported in patients aged 20-50 which accounts
for 59.6%. The highest number of ACBC was isolated from pus samples (n = 12,
37.5%).
All ACBC isolates were resistant to amoxicillin,
cefotaxime, and ceftazidime, whereas 31 isolates were resistant to amikacin and
gentamycin. The majority of ACBC isolates (93.8%) were multidrug resistant. Most of
the isolates were susceptible to doxycycline (53.1%), followed by cotrimoxazole
(18.7%), levofloxacin (15.6%), and ofloxacin (15.6%). All isolates were susceptible to colistin and
polymyxin B. The higher rate of antimicrobial resistance in bacterial pathogens is due
to the irrational use of antibiotics, adherence to empirical therapy without
proper AST, extensive use of antibiotics in poultry, direct disposal of
antimicrobial waste in the environment, etc. The higher antibiotic
susceptibility of ACBC isolates towards doxycycline antibiotics was reported,
so it can be used to treat multidrug-resistant ACBC infections. Carbapenem
resistance in A. baumannii is mainly
caused by class B MBL and class D OXA type β-lactamase, which can hydrolyze
carbapenem antibiotics [5]. CR-AB infections have a high morbidity and death
rate in hospital settings due to their low level of antibiotic susceptibility
and subsequent failure of therapy.
A significant
association was observed between carbapenem resistance and biofilm formation (p-value
< 0.05), indicating the role of biofilm in carbapenem resistance. Out of 31 biofilm-positive isolates, 21 isolates were
positive for both Bap and csuE genes, and 18 isolates were
positive for the blaPER1
gene (Figure 1). The biofilm-related genes help in biofilm formation,
survival in hospital environments and medical devices, and disease pathogenesis
in hospital settings [2,3]. No biofilm-related genes were found in carbapenem-sensitive
ACBC isolates, and a significant association between carbapenem resistance and
biofilm-forming genes bap, csuE, and blaPER-1 was found. Further, the co-existence
of Bap, csuE, and blaPER1
among positive biofilm isolates was found to be 58%, which may have boosted
biofilm formation. The co-existence of Bap
and csuE was 9.8%, and no genes were
singly present, which also indicates the dependence of genes on biofilm
formation, such as csuE is critical
for initial attachment and bap for
biofilm maturation.
Figure 1: Detection of Biofilm-related genes among ACBC
isolates by conventional PCR. 1a: Screening of csuE gene (L1: Ladder, L2 &
L3: amplified products from ACBC isolates, L4: positive control, L5: no
template control and L6: Ladder); 1b: Screening of Bap gene (L1 & L2: amplified
products from ACBC isolates, L3: positive control and L5: no template control),
and 1c: Screening of blaPER1 gene (L1: positive
control, L2: no template control, L3
& L4: amplified products from ACBC isolates, and L5: ladder).
Conclusion
The increase
in biofilm formation significantly associated with carbapenem resistance adds a
big challenge to controlling CR ACBC infections. In addition, this capability
of ACBC contributed to antibiotic resistance as well as helped them in environmental
survival. Hence, proper sterilization of hospital equipment and the environment
should be of primary concern, and a strong policy to prescribe effective
antibiotics based on the antibiogram profile should be implemented.
Acknowledgements
We express our sincere
gratitude to laboratory staff members of GoldenGate International College (GGIC),
Kathmandu Model Hospital, and the team of CMDN for their support, in completing
this study. We are very much thankful to the participants and their legal guardians
for providing samples.
Data availability
The data used in this
study will be available from the corresponding author (Email: upendrats@gmail.com/upendra.thapashrestha@cdmi.tu.edu.np)
upon request.
Competing interests
The authors declare no competing
interests.
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Citation: Shova Bhandari, Milan
Kumar Upreti, Khadga Bikram Angbuhang, Basudha Shrestha, Upendra Thapa
Shrestha*. Increased biofilm-associated carbapenem-resistant
Acinetobacter calcoaceticus–baumannii complex infections among hospitalised
patients in Kathmandu Model Hospital, Nepal. Journal of Global
Antimicrobial Resistance, 2024; 39:1-2. ISSN 2213-7165.
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