|Year : 2002 | Volume
| Issue : 2 | Page : 123-128
Complicated nosocomial UTI caused by nonfermenters
SK Meharwal, Neelam Taneja, SK Sharma, Meera Sharma
Departments of Medical Microbiology and Urology, Postgraduate Institute of Medical Education & Research, Chandigarh, India
Department of Medical Microbiology, PGIMER, Chandigarh- 160 012
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aerobic nonfermenting gram-negative bacilli (nonfermenters) usually considered as contaminants are emerging as important nosocomial pathogens. 110 such strains obtained from 4200 consecutive urinary tract specimens were characterized by a battery of biochemical tests. Antibiotic susceptibility was tested against gentamicin, amikacin, netilmicin, ceftazidime, piperacillin and ciprof oxacin. Significance was assigned by taking into account clinical details and isolation of the same organism in the repeat specimen. Pseudomonas spp. (45.5%) were the commonest followed by Acinetobacter spp. (39%), Alcaligenes spp. (8%) and Flavobacter spp. (3.63%). Two strains of Weeksella virosa, and one each of Xanthomonas rnaltophilia and CDCllg were also recovered. Pseudomonas aeruginosa and Acinetobacter baumanii were the most common significant isolates (62.9% and 25.9% respectively). Alcaligenes spp. was found to be etiologically significant in 5 out of 7 cases. In only 2 cases (4%) isolation of a Pseudomonas spp other than Paeruginosa was considered significant. Out of 4 strains of Flavobacter spp. only one could be confirmed as significant. Postoperative period (42.6%) followed by obstructive uropathy (32%) and surgery on urinary tract (8%) were commonest risk factors. All strains except a few showed high level of drug resistance.
Keywords: Urinary Tract Infection; Nosocomial; Nonfermenters
|How to cite this article:|
Meharwal S K, Taneja N, Sharma S K, Sharma M. Complicated nosocomial UTI caused by nonfermenters. Indian J Urol 2002;18:123-8
| Introduction|| |
Urinary tract infections are the second most common bacterial infections affecting humans throughout their lifetime. They are frequent cause of morbidity in outpatients as well as most frequent cause of nosocomial infection in many hospitals.  E.coli is the commonest urinary pathogen accounting for over 80% of community-acquired infection. Far less commonly Klebsiella spp, Proteus spp and Staphylococcus saprophyticus are responsible for community-acquired infection. The distribution of urinary pathogens in hospitalized patients is different, with E.coli accounting for about 50% of infections. Enterococcus, Klebsiella, Enterobacter, Citrobacter, Serratia, Pseudomonas aeruginosa, Providencia, and Staphylococcus epidermidis account for most of the rest. 
Aerobic nonfermenting gram-negative bacilli (nonfermenters) are a heterogeneous group of organisms that are either incapable of utilizing carbohydrates as a source of energy or degrade them via oxidative rather than fermentative pathway.  This group includes organisms from diverse genera like Pseudomonas, Acinetobacter, Alcaligenes, Flavobacter, Oligella, Flavimonas, Agrobacter Weeksiella, etc. A few of these have not been named and are designated by CDC numbers like CDC11g. These organisms are common inhabitants of soil and water. They also exist as harmless parasites on the mucus membranes of humans and animals. Though primarily regarded as contaminants or incidental organisms, they are becoming increasingly important as opportunistic pathogens in immunocompromised patients. They can also cause infection by gaining access to normally sterile body sites through trauma.  Though these organisms vary in their potential to cause infection and antibiotic susceptibility, there are common disease manifestations and risk factors. These organisms have been implicated in causing septicemia, meningitis, osteomyelitis, wound infections, pneumonias and urinary tract infections. Risk factors include immunosuppression, trauma, foreign body, broad-spectrum antibiotic use and infused body fluids like saline irrigations.  Pseudomonas aeruginosa i>is the predominant and most well known organism out of this heterogeneous group. This is partly due to its easy recognition in the laboratory as it produces pyocyanin, a blue-green pigment. Other organisms usually get ignored as contaminants because identification up to species level is cumbersome and laborious and not possible in a busy routine microbiology laboratory. Evaluation of significance of isolating these organisms is complicated by the fact that they are usually present in mixed culture and the clinicians are rather unfamiliar with their names. The present study was taken up to characterize these organisms from urinary tract specimens and evaluate their role as pathogens.
| Materials and Methods|| |
Four thousand and eight hundred urinary tract (UT) specimens were consecutively screened for the presence of nonfermenters over a three-month period from January 2000 to March 2000. Only those strains which were recovered in pure culture and significant numbers (>10 5 cfu/ ml) were included. 110 such nonfermenters were characterized by using a battery of tests which included gram stain, oxidase reaction, catalase test, motility, pigment production, gelatin liquefaction, growth on MacConkey's medium, hemolysis on blood agar, Hugh Leifson's O-F test with 1% glucose, lactose and xylose each, lysine and ornithine decarboxylase test, arginine dehydrolase test, urease production, citrate utilization, aesculin hydrolysis, growth at 4°C and 42°C, gelatin liquefaction, nitrate reduction and denitrification and H 2 S production in TSI. For seven strains, which were non-motile, oxidase and catalase positive and produced yellow coloured colonies (provisional Flavobacter group), further biochemicals were put to speciate them. These included Hugh Leifson's O-F with maltose (1%), sucrose (1%) and mannitol (1%), penicillin susceptibility (IOU) and polymyxin (300U) susceptibility. The criteria laid down by CDC Atlanta' were used to identify these organisms. The strains were tested for invitro susceptibility to gentamicin (10 ug), amikacin (100 ug), netilmicin (30 ug), ceftazidime (30 ug), piperacillin (100 ug) and ciprofloxacin (5 ug) by modified Stoke's method.  All media and antibiotic discs were from Himedia. A repeat sample was obtained in admitted patients. Following information was recorded for each patient: age, ward case, symptoms and risk factors for development of UTI. The strains were considered to be confirmed significance if patient was symptomatic with/without presence of pyuria and repeat specimen was positive for the same organism. The significance was assigned as probable but not confirmed if in such cases a repeat sample was negative or could not be obtained. The strains were considered as contaminant if patients were asymptomatic, there was no pyuria, the repeat samples negative and no risk factors for development of complicated UTI were present.
| Results|| |
110 strains of nonfermenters were obtained from 86 patients. 65 patients were hospitalized and 21 were attending the Outpatients Department at PGIMER, Chandigarh. 45 patients were males and 41 were females. Maximum number of patients belonged to the age groups 16-45 years [Table - 1]. Risk factors for development for complicated UTI were presented in 87.2% of cases. Postoperative period (42.6%) followed by obstructive uropathy (32%) and surgery on urinary tract (8%) were the commonest risk factors [Table - 2]. Pseudomonas spp. were the commonest (45.4%) followed by Acinetobacter spp. (39.0%), Alcaligenes spp. (8.1%) and Flavobacter spp. (3.63%). One strain (0.9%) of Weeksella virosa, Xanthomonas maltophilia and CDCllg were recovered [Table - 4]. Maximum resistance was observed for strains of Acinetobacter baumanii. However, all the strains of nonfermenting bacilli except PP fluorescence showed very high level of resistance as depicted in [Table - 3]. Piperacillin (41.8% resistance) and amikacin (47.2% resistance) were the most effective in vitro antibiotics. In 39.5% of cases strains could be confirmed as etiological significant. For 47.6% of cases significance was probable and only 12% of the strains were contaminants. P.aeruginosa was the most significant species (17 patients-62.9%). In only 29.6% (7 patients), Acinetobacter spp. could be confirmed as significant. Various Alcaligenes spp. were significant in 55.5% of cases (5 patients). Only in 2 cases (4%) isolation of Pseudomonas spp. other than Pseudomonas aeruginosa was considered significant. Out of 4 strains of Flavobacter spp. only one could be confirmed as significant. The two strains of Weeksella virosa were recovered from same patients and were considered significant [Table - 4].
| Discussion|| |
Urinary tract infections are found in all age groups. One percent of all neonates have bacteria in bladder urine.  The incidence is higher in male infants due to presence of congenital anomalies.  From adulthood to the age group of 65 years, the incidence of UTI is very high in women as compared to men. In older patients there is a progressive decrease in the female to male ratio due to development of obstructive uropathy from the prostatic enlargement. In the present study out of 7 male infants 5 had posterior urethral valves with hydronephrosis. In the sexually active age group (16-45 years) males and females were equally affected. This was due to the fact that most of the infections in this particular study were complicated; risk factors being present in 87.2% of patients. Postoperative period (42.6%), followed by obstructive uropathy (32%) and surgery on urinary tract (8%) were the commonest risk factors. The high incidence in postoperative period was most probably related to catheterization. Most of the patients were females (24 out of 37) undergoing caesarian section and gynecological surgeries. Many of these infections were due to Acinetobacter spp, and patients improved after removal of catheter. This suggests that Acinetobacter spp. cause a colonization of urinary bladder as also observed in a previous study.  In all the admitted patients infections were of nosocomial origin. Only 25% patients were from outpatient department (OPD) and most of these were attending urology OPD because of problems like stricture urethra, vesicoureteral reflux and chronic renal failure. Though nosocomial origin of these infections cannot be proved, it was highly likely.
Pseudomonas aeruginosa is an established pathogen of urinary tract.  It was the commonest isolate in the present study being etiologically significant in 62.9% of cases. Pseudomonas spp. like P. fluorescence and P. putida have been recovered from urine samples ,,, but significance has been confirmed for only a few of these. In the present study none of the strains of P. putida, P pickettii and P vesicularis could be confirmed as significant. One strain of P putrifaciens was repeatedly isolated from two male infants who had bilateral vesicoureteral reflux. Significance of X.maltophilia was questionable.
Acinetobacters are ubiquitous in environment and in hospitals.  They account for I to 3 percent of nosocomial infections, being second only to Paeruginosa in their recovery from clinical specimens.  Acinetobacters have been implicated in causation of a variety of illness including UTI.  Most of the infections are caused by A.baumanii. A.lwoffi is less virulent and its isolation most often indicates contamination rather than infection. In the study by Pederson et al  only 2 out of 24 strains of Acinetobacters appeared to be significant. In the current study 43 strains of Acinetobacter spp. were obtained. A.baumanni (31) were the commonest followed by A.lwoffi (7) and A.calcoaceticus (3). One strain each of A.hemolyticus and A. junii were recovered. Only 7 strains of A.baumanii and one strain of A.calcoaceticus could be confirmed as significant.
Alcaligenes fecalis has also been associated with causation of serious infections like pyelonephritis and has been isolated from asymptomatic renal calculi.  Contamination of irrigating fluids used in the genitourinary procedures has resulted in common source epidemics of UTI due to this organism.  In the present study, 9 strains were obtained. Only 5 of these could be etiologically confirmed as urinary tract pathogens. These include Alcaligenes xylosoxidans sub spp. xylosoxidans , A. fecalis (2) and A.xylosoxidans sub spp. piechaudii (1).
Reports in literature , indicate that saccharolytic Flavobacteria are frequently recovered from clinical specimens. In the present study 2 each of F.indologenes, Fodoratum, Weeksella virosa and one of CDClIg were obtained. The strains of W.virosa belonged to the same patient and were repeatedly isolated from a patient who underwent surgery on urinary tract for nephrolithiasis. The strain was multidrug resistant in contrast to reports in literature. , One of the Eindologenes was considered significant. This patient had stricture urethra. The two strains of Fodoratum were from males who had undergone surgery on gastrointestinal tract. None of these could be confirmed as significant as repeat samples were negative. A very high level of drug resistance was observed in general for all strains. This could be due to the fact that most of these infections were of nosocomial origin. Some patients especially those who had surgery on urinary tract, developed persistent infection and were treated with multiple antibiotics. Piperacillin and amikacin appeared to be the most effective antibiotics in vitro. From the present study it can be concluded that nonfermenters though regarded as contaminants are important agents causing complicated nosocomial infections. If recovered in pure culture, a repeat specimen should be taken to confirm their presence, and the strain should be identified up to the species level.
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[Table - 1], [Table - 2], [Table - 3], [Table - 4]
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