|Year : 2013 | Volume
| Issue : 1 | Page : 3-6
A comparative analysis of isolation and antibiotic sensitivity pattern of Pseudomonas aeruginosa isolated from pus and urine with special reference to phenotypic and genotypic expression of extended spectrum beta lactamases (ESBLs)
PA Shiny1, S Rajendran2, Y Lakshmi Sarayu2
1 Department of Microbiology, Dr. Somervell Memorial CSI Medical College, Karakonam, India
2 Department of Microbiology, Rajah Muthiah Medical College, Annamalai University, Chidambaram, Cuddalore District, Tamil Nadu, India
|Date of Web Publication||3-Aug-2013|
P A Shiny
Department of Microbiology, Dr. Somervell Memorial CSI Medical College, Karakonam
Source of Support: None, Conflict of Interest: None
Pseudomonas aeruginosa (Ps. aeruginosa) is a classic opportunistic pathogen with innate resistance to many antibiotics and disinfectants. The aim of this study was to find the prevalence and the resistance pattern, phenotypic, and genotypic characterization of Ps. aeruginosa from different source of infection. The present study was carried out with a total of 1000 clinical samples including 500 pus samples and 500 urine samples, which were received from patients admitted in the various departments of Rajah Muthiah Medical College and Hospital, Annamalai University, Chidambaram. Of the 500 pus and 500 urine samples screened, the percentage positivity of Ps. aeruginosa was 12.8% (64) and 4% (20), respectively. Pseudomonas aeruginosa from different samples showed different sensitivity patterns to different antibiotics. In case of isolates from pus, all (100%) were sensitive to Imipenem, while resistance was maximum to Cefotaxime (93.75%). When Pseudomonas aeruginosa isolated from urine was tested for the same antibiotics, sensitivity was maximum (90%) to Tobramycin, while resistance was maximum (80%) to Cefotaxime and Aztreonam. ESBL positive Ps. aeruginosa isolated from pus and urine was 50% and 40%, respectively. The genotype characterization of 25 of these strains showed 6 with CTX-M and 12 with SHV genes.
Keywords: Antibiotic sensitivity, ESBL, Pseudomonas aeruginosa, pyogenic infections, urinary tract infection
|How to cite this article:|
Shiny P A, Rajendran S, Sarayu Y L. A comparative analysis of isolation and antibiotic sensitivity pattern of Pseudomonas aeruginosa isolated from pus and urine with special reference to phenotypic and genotypic expression of extended spectrum beta lactamases (ESBLs). J Acad Clin Microbiol 2013;15:3-6
|How to cite this URL:|
Shiny P A, Rajendran S, Sarayu Y L. A comparative analysis of isolation and antibiotic sensitivity pattern of Pseudomonas aeruginosa isolated from pus and urine with special reference to phenotypic and genotypic expression of extended spectrum beta lactamases (ESBLs). J Acad Clin Microbiol [serial online] 2013 [cited 2017 Oct 20];15:3-6. Available from: http://www.jacmjournal.org/text.asp?2013/15/1/3/116083
| Introduction|| |
Pseudomonas aeruginosa is a comm on bacterium that causes infection in man, animals, and plants. Ps. aeruginosa is an opportunistic pathogen that typically causes infections in burns and wounds and also infects hospitalized and immunosuppressed patients.  Ps. aeruginosa can also cause urinary tract infection (UTI) in patient with complex urinary tract abnormalities.  Ps. aeruginosa infestations are of three types- bacterial attachment and colonization, local infection and disseminated systemic disease. However, the disease process may stop at any stage. Nowadays, Ps. aeruginosa is developing multidrug resistance to all antibiotics that have been used for treatment by clinicians.
Hence, this study was conducted to correlate the prevalence rate, sex, age, socioeconomic and domicile status, antibiotic sensitivity, extended spectrum beta lactamase (ESBL), and genotypic characterization of Ps. aeruginosa causing pyogenic infection and UTI isolated from patients attending Rajah Muthiah Medical College and Hospital, Chidambaram, Cuddalore district, Tamil Nadu, India.
| Materials and Methods|| |
A total of 1000 clinical specimens including 500 pus and 500 urine samples were received from patients admitted in Rajah Muthiah Medical College and Hospital. Pus samples were collected from patients with pyogenic infections including ulcers, injury, wounds, and burns admitted in various departments including Medicine, Surgery, Paediatrics, and Orthopedics. The specimens collected were pus swabs, aspirates, and drained pus. Urine samples were collected from various departments including Medicine and Urology. These patients presented with various diseases such as UTI, pyelonephritis, cystitis and benign prostate hypertrophy. Specimen collected was early morning midstream urine.
The samples were collected in sterile containers and processed immediately. The Gram stained smear of the specimens were examined and culture for aerobic pathogens was done by standard procedures. 
The colonies of Ps. aeruginosa were presumptively identified by colony morphology, pigment production, characteristic musty or earthy odor. The identification was confirmed by motility and biochemical tests, which included fermentation of sugars, oxidation fermentation (O/F Test), indole production, nitrate reduction, oxidase, and catalase test.  Antimicrobial susceptibility testing was conducted with antibiotics Gentamicin (G), Amikacin (AK), Cefepime (Cpm), Cefotaxime (CE), Aztreonam (Ao), Meropenem (M 1 ) Imipenem (I), Tobramycin (TB), Ofloxacin (OF), Norfloxacin (Nx), and Ticarcillin (T 1 ) by Kirby-Bauer's disc diffusion method. 
| Results|| |
A total of 1000 samples including 500 from pyogenic infections and 500 from UTIs were collected and screened for the isolation of bacteria. Of the 500 pus and 500 urine samples screened, culture positivity was obtained in 410(82%) pus samples and 335(66.4%) urine samples, respectively. Isolation rate of Ps. aeruginosa was 12.8% in pus and 4% in urine [Figure 1], [Table 1].
|Figure 1: The prevalence of Ps. aeruginosa in pyogenic and urinary tract infection.|
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Sex wise distribution of Ps. aeruginosa showed 59.37% in males and 40.63% in females among pyogenic infection cases. Ps. aeruginosa isolated from urine showed higher percentage in males (80%) as against females (20%) [Table 2]. Among pyogenic infection cases males and females showed higher percentage positivity for Ps. aeruginosa in the age group of 61-75 years (28.12%).
|Table 2: Sex wise distribution of Ps. aeruginosa positive pyogenic infection and urinary tract infection|
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Of the 64 Ps. aeruginosa positive pyogenic infection cases 36 (56.25%) were coolies. Ps. aeruginosa positive UTI cases(20) were mainly coolies (30%) and drivers (30%).
80% of Ps. aeruginosa positive pyogenic infection cases were from rural areas, whereas Ps. aeruginosa positive UTI cases were almost equal in rural (40%), semi urban (30%), and urban areas (30%).
[Table 3] shows the results of susceptibility of the P. aeruginosa isolates to various antibiotics. All (100%) strains isolated from pus were sensitive to Imipenem, 93.75% strains were resistant to Cefotaxime, and 58% resistant to Ceftazidime.
|Table 3: Antibiogram pattern of Ps. aeruginosa isolated from pus and urine samples|
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Of the strains isolated from urine samples, majority (90%) were sensitive to Tobramycin, 80% to Gentamicin, Meropenem & Imipenem, while a maximum of 80% strains were resistant to Cefotaxime and Aztreonam and 60% to Cefepime [Table 3].
Multi drug resistance was seen in 47 (73.43%) of Ps. aeruginosa isolated from pus and 17 (26.57%) showed resistance to a single drug. Multi drug resistance was seen in 18 (90%) of those isolated from urine and 2 (10%) showed single drug resistance [Table 4].
|Table 4: Expression of antibiotic resistance pattern of Ps. aeruginosa isolated from different samples against 13 antibiotics|
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There were 40 (32 from pus and 8 from urine) strains of Pseudomonas aeruginosa that were resistant to 3rd generation cephalosporins and found to be positive by the double disc synergy test for ESBL detection [Table 5]. Genotype characterization of 25 of these strains showed 6 strains with CTX-M and 12 with SHV gene [Table 6].
|Table 6: Expression of ESBL Genes by Pseudomonas aeruginosa isolated from various sources|
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| Discussion|| |
Ps. aeruginosa is widely distributed in nature, existing usually as saprophyte but can give rise to pathological lesions and generalized infections in man.  Ps. aeruginosa is the most frequently isolated nonfermentative bacilli found in clinical specimens.
Ps. aeruginosa has one of the broad ranges of infectivity among all pathogenic microorganisms. The species can cause disease in plants, insects, fish, amphibians, reptiles, birds, and mammals.  Ps. aeruginosa causes UTI, respiratory tract infections, dermatitis (hot tub rash), soft tissue infections, bacteremia, bones and joint infection, central nervous system, and gastrointestinal infections in humans. A variety of systemic infections caused by Ps. aeruginosa particularly in patients hospitalized with cancer, cystic fibrosis, burns, and fatality rate in these patients is near 50%.  Ps. aeruginosa produces infection of wounds and burns giving rise to blue green pus. The organism can be acquired by invasive procedures like lumbar puncture, catheterization and instrumentation or from irrigating solutions. 
Ps. aeruginosa is notorious for its resistance to antibiotics and is therefore a particularly dangerous and dreaded pathogen. The bacterium is naturally resistant to many antibiotics due to the permeability barrier afforded by its gram negative outer membrane. Also, its tendency to colonize the surface in a biofilm form makes the cells impermeable to therapeutic concentration of the antibiotics. Moreover, Ps. aeruginosa maintains antibiotic resistance plasmid, both F factors and resistance transfer factor (RTF) and it is able to transfer the genes by means of the bacterial mechanism of horizontal gene transfer (HGT), mainly transduction and conjugation.  The emergence of antibiotic resistance is due to irrational use of antibiotics in treating human infections. 
The present study shows that in a total 500 cases of pyogenic infection, 12.8% were positive for Ps. aeruginosa as against 4% in 500 UTI cases. In this study Ps. aeruginosa isolates from urine were showing higher percentage in males (80%) as against 59.37% positivity in males from pyogenic infections.
Ps. aeruginosa isolated from pus and urine showed higher degree of drug resistance against Cefotaxime, since the clinicians were using Cefotaxime as routine antibiotic therapy against all Ps. aeruginosa infections. Although 80% of strains from urine were sensitive to Meropenem, only 63% of strains isolated from pus were sensitive. However, 100% of strains isolated from pus and 80% of strains from urine were sensitive to Imipenem. A higher percentage of ESBL Ps. aeruginosa was seen in pus.
The genotypic characterization showed the Ps. aeruginosa isolates expressed both the SHV and CTX-M and percentage positivity of SHV was higher than the percentage positivity of CTX-M in the 25 strains tested.
Thus the present study shows that the isolation and testing of Ps. aeruginosa for antibiotics is necessary for accurate reporting and to detect chromosomally mediated vertical transmission of drug resistance in Ps. aeruginosa.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]