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Prakash H. Ravichandra et al. / JPBMS, 2012, 14 (05)
1 Journal of Pharmaceutical and Biomedical Sciences (JPBMS), Vol. 14, Issue 14
Available online at www.jpbms.info
JPBMS
JOURNAL OF PHARMACEUTICAL AND BIOMEDICAL SCIENCES
Antimicrobial susceptibility pattern of Pseudomonas aeruginosa strains isolated from
clinical sources.
H.RavichandraPrakash1. Rashmi Belodu2, Neena Karangate3, Suresh Sonth4, Anitha.M.R5, Vijayanath.V6
1 Associate Professor, Department of Microbiology, Basaveshwara Medical College and Hospital , Chitradurga – 577502, India.
2 Assistant Professor, Department of Microbiology, Basaveshwara Medical College and Hospital, Chitradurga – 577502, India.
3Professor and Head Department of Microbiology, Basaveshwara Medical College and Hospital Chitradurga – 577502, India.
4 Assistant professor, Department of Microbiology, S.N Medical College, Navanagar, Bagalkot – 587102 . India.
5 Assistant Professor, Department of Anatomy, VMKV Medical College and Hospital, Salem. Tamil Nadu, India.
6 Associate Professor, Department of Forensic Medicine & Toxicology, VMKV Medical College & Hospital, Salem. Tamil Nadu,
India.
Abstract: Objective: Currently antibiotic resistance in bacterial populations is one of the greatest challenges to theeffective management of infections. Constant bacteriological monitoring of pathogens in the hospital in general andspecialized units is necessary to provide accurate data on the prevalence and antibiotic resistance pattern of specific
pathogens. Pseudomonas aeruginosa is one of the most common gram-negative microorganisms identified in the clinical
specimens of hospital admitted patients. The present study was undertaken to assess antibiotic resistance in clinical
isolates of Pseudomonas aeruginosa in our hospital, and to obtain baseline information on the presence of this important
pathogen.
Methods & Results: A total of 486 Pseudomonas aeruginosa were isolated of which 340 (70.0%) were from indoor and
146 (30.0%) were from outdoor patients. Of the 486 isolates 292 (60.0%) were from males and 194 (40.0%) from females.
From the study population 223 (45.88%) patients were aged between 21-40 years, while 149 (30.65%) were below 20years. In present studies the resistance against ofloxacin and ciprofloxacin was observed between 70 – 98%. The
aminoglycoside group of antibiotics - amikacin - demonstrated maximum sensitivity against Pseudomonas species.
Conclusion: Therefore, use of amikacin should be restricted to severe nosocomial infections, in order to avoid rapid
emergence of resistant strains. Periodic susceptibility testing should be carried out over a period of two to three years, to
detect the resistance trends. Also, a rational strategy on the limited and prudent use of anti-Pseudomonal agents isurgently required.
Keywords: Pseudomonas aeruginosa, Antimicrobial resistance, Sensitivity, Disk diffusion technique, Reserve drugs.
Introduction:The Pseudomonads are a diverse bacterial group of
established and emergent pathogens[1-3]
. Members of thegenus are major agents of nosocomial and community
acquired infections, being widely distributed in the
hospital environment where they are particularly difficult
to eradicate. Pseudomonas aeruginosa, although not anobligate parasite, is the species amongst the
Pseudomonads most commonly associated with human
diseases. [3] It needs minimal nutritional requirements for
growth. It is a commensal in healthy people. This rate of
commensalism increases gradually with the increased
duration of hospital stay [4].
Pseudomonas aeruginosa is primarily an opportunistic
pathogen that causes infections in hospitalized patientsparticularly in burns patients where the skin host defenses
is destroyed, orthopedic related infection, respiratory
diseases, immunosuppressed and catheterized patients. It
may be the cause of the chronic debilitating pulmonary
infection, which is one major cause of death in-patients
with cystic fibrosis [5]. Generally it contributes substantially
to wound related morbidity and mortality worldwide[6]
.Pseudomonas aeruginosa is usually inherently resistant to
many antimicrobial agents, treatment of pseudomonal
infections is usually difficult, and mortality is usually high[7,8]. This intrinsic resistance is mainly a result of the
diffusion barrier of the bacterial outer membrane; amino-
acid substitution in the target molecules, such as Gyr Aand/or Par C, via point mutation in each genetic
determinant; and antimicrobial inactivating enzymes. In
most hospital environments, this inherent resistance is
further complicated by mutations mediated via
chromosomes and the acquisition of resistant genes from
plasmids and transposons [9].
Pseudomonas aeruginosa demonstrates resistance to
multiple antibiotics, thereby jeopardizing the selection of
appropriate treatment [10] and over a period of time, we
ISSN NO- 2230 – 7885
CODEN JPBSCTResearch article
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Prakash H. Ravichandra et al. / JPBMS, 2012, 14 (05)
2 Journal of Pharmaceutical and Biomedical Sciences (JPBMS), Vol. 14, Issue 14
observed an increase in number of Pseudomonas
aeruginosa among our laboratory isolates. So, we decided
to carry out a retrospective study to see infections causedby Pseudomonas aeruginosa and susceptibility pattern of
the organisms isolated from different clinical specimens at
our hospital.
Materials and Methods:The study was conducted in a tertiary care hospital fromJanuary 2010 to December 2010. The cases were from both
inpatient and outpatient departments.
Isolation, characterization and identification: The various clinical specimens included wound swab,
urine, pus, ear discharge, etc. were cultured. Pseudomonas
aeruginosa isolates were characterized and identified using
a combination of colonial morphology, Gram stain
characteristics, motility test, oxidative- fermentation test,
catalase, citrate and oxidase tests and pyocyanin
production.
Antibiotic susceptibility testing: The antibiotic susceptibility pattern of the Pseudomonas
aeruginosa isolates was determined using the disk
diffusion method according to the modified Kirby-Bauertechnique [11]. All the clinical isolates and a standard strain
Pseudomonas aeruginosa ATCC 27853 were tested for their
sensitivity against a panel of anti-pseudomomal
antimicrobials including: tobramycin (TOB), gatifloxacin
(GAT), ciprofloxacin (CIP), nalidixic acid (NA), ceftazidime
(CAZ), ceftriaxone (CTR), cefixime (CFX), doxycycline (DO),
gentamycin (GEN), amikacin (AK), ofloxacin (OF),
piperacillin-tazobactum (PIT), and azithromycin (AT) ofstandard strengths.
Results: A total of 486 Pseudomonas aeruginosa were isolated of
which 340 (70.0%) were from indoor and 146 (30.0%)
from outdoor patients. Of the 486 isolates 292 (60.0%)
were from males and 194 (40.0%) from females. From the
study population 223 (45.88%) patients were agedbetween 21-40 years, while 149 (30.65%) were below 20
years. ( Table 1 )
Table 1: Age distribution of cases Age (in years) Number of isolates Percentage
0 – 20 177 36.42
21 – 40 211 43.42
41 – 60 73 15.02
>60 25 5.14
TOTAL 486 100
Wound swab, urine, pus and ear discharge constituted
about 95.2% of the total samples. Of the 486 isolates of
Pseudomonas aeruginosa, 232 (47.7.0%) were isolated
from wound swab only, followed by pus 133 (27.4%),urine 59 (12.1%) and ear discharge 39 (8%). ( Table 2 )
Table 2: Isolation of Pseudomonas aeruginosa from different clinical
specimens
Specimen No of isolates Percentage
Wound swab 232 47.7
Pus 133 27.4
Urine 59 12.1
Ear discharge 39 8.0
Blood culture 5 1
Sputum 7 1.5
Others 11 2.3
Total 486 100
The Pseudomonas aeruginosa isolated from different
specimens varied in resistance rate to different
antimicrobials. The isolates with least amount of resistance
were to amikacin, piperacillin-tazobactum and
azithromicin. Greater resistance was shown to
ciprofloxacin, ofloxacin, gentamycin, cefixime and less
resistance was shown to tobramicin, ceftazidime,gatifloxacin, nalidixic acid and doxycycline. ( Table 3 ).
Table 3: Resistance rate of Pseudomonas aeruginosa isolated from different clinical samples SPECIMEN TOB GAT CIP NA CAZ CTR CFX DO GEN AK OF PIT AT
Wound swab 66.37 32.32 87.93 64.65 73.27 74.13 84.48 88.36 78.44 21.55 87.93 58.18 13.36
Pus 78.19 48.87 98.49 57.89 58.64 68.42 91.72 67.66 94.73 18.79 98.49 46.61 19.54
Urine 59.32 55.93 93.22 67.79 71.18 62.71 79.66 77.96 84.74 8.47 77.86 66.10 11.86
Ear discharge 92.30 23.07 74.35 84.61 100 48.71 87.17 56.41 76.92 15.38 87.17 38.46 23.07
Blood culture 80 40 80 80 80 100 100 60 60 20 80 40 20
Sputum 85.71 71.42 85.71 71.42 42.85 57.14 85.71 28.57 71.42 14.28 100 42.85 28.57
Others 81.81 36.36 90.90 63.63 45.45 72.72 72.72 45.45 90.90 09.09 90.90 27.27 09.09
Discussion: Pseudomonas aeruginosa emerged as an important
pathogen and responsible for the nosocomial infections
that is one of the important causes of morbidity and
mortality among hospital patients. More over Pseudomonas
aeruginosa infection is dependent on age and duration ofthe stay in hospital. The infection was more common in
young and middle age group then elderly people. Duration
of stay is directly proportional as infection was much
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Prakash H. Ravichandra et al. / JPBMS, 2012, 14 (05)
3 Journal of Pharmaceutical and Biomedical Sciences (JPBMS), Vol. 14, Issue 14
higher in indoor patients than the outdoor patients. This
might be due to the prolonged stay in hospital following an
operation resulting in colonization and subsequentinfection [12- 14].
In our study the resistance against ofloxacin and
ciprofloxacin was observed between 70 – 98%. The
quinolone resistant Pseudomonas aeruginosa showed the
presence of new outer membrane protein in the range of51-54 KDa. These proteins apparently actively transport
quinolone out of the cell [15]. The resistance pattern againstgentamycin tobramycin, ceftazidim, amikacin, doxycicline,
ceftriaxone was observed to be less as compared to other
drugs in this study. These finding are in good agreement
with the other similar studies [16]. The least resistance was
seen with amikacin, azithromycin, and
piperacillin/tazobactam. Among all the drugs amikacin
showed the highest sensitivity against Pseudomonasaeruginosa (Table 3), which is in corroboration with an
earlier report published from India[17]. Amikacin was
designed as a poor substrate for the enzymes that bring
about inactivation by phosphorylation, adenylation oracetylation, but some organisms have developed enzymes
that inactivate this agent as well.Amikacin seems to be a promising therapy for
Pseudomonal infection. Hence, its use should be restricted
to severe nosocomial infections, in order to avoid rapid
emergence of resistant strains 18. The problem of
increasing resistance to Pseudomonas aeruginosa haslimited the use of other classes of antibiotics like the
fluoroquinolones, tetracyclines, macrolides and
chloramphenico[19]. Blood and sputum accounted for 1%
and 1.44% respectively of the Pseudomonas aeruginosa,
this may be due to the low number of blood and sputumsamples sent during the study period. However
Pseudomonas aeruginosa is said to be responsible forpneumonia and septicaemia with attributable deaths
reaching 30% in immunocompromised patients [20-22].
In fact, the irrational and inappropriate use of antibiotics is
responsible for the development of resistance of
Pseudomonas species to antibiotic monotherapy. Hence,
there is a need to emphasize the rational use ofantimicrobials and strictly adhere to the concept of
“reserve drugs” to minimize the misuse of available
antimicrobials. In addition, regular antimicrobial
surveillance is essential for monitoring of the resistancepatterns. An effective national and state level antibiotic
policy and guidelines should be introduced to preserve theeffectiveness of antibiotics and for better patient
management.
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Therapeutics. 11th ed. Mc-Graw Hill: Medical Publishing
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Conflict of Interest: - None Source of funding: - Not declared
*Corresponding author: Dr. H.Ravichandra Prakash. MD.,
Associate Professor, Department of Microbiology
Basaveshwara Medical College and HospitalChitradurga – 577502 ,India.
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