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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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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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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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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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