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ORIGINAL CONTRIBUTION |
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| Year : 2000 | Volume
: 54
| Issue : 9 | Page : 388-394 |
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Emerging antibiotic resistance among the uropathogens*
Shobha Ram, R Gupta, M Gaheer
Department of Microbiology, Dayanand Medical College & Hospital, Ludhiana, India
Correspondence Address:
Shobha Ram
Department of Microbiology, Dayanand Medical College & Hospital, Ludhiana
India
PMID: 11966063
How to cite this article:
Ram S, Gupta R, Gaheer M. Emerging antibiotic resistance among the uropathogens*. Indian J Med Sci 2000;54:388-94 |
The term urinary tract infections (UTI) denotes several distinct entities with the common feature of significant. pyuria and bacteriuria. [1] It is the most frequent cause of illness in humans after respiratory tract infections. It has been observed that Escherichia coli is the sole causative agent In more than 80% of uncomplicated UTI. [2] Like all other infections, outcome of the UTI is an interplay of the virulence factors of the pathogen and the predisposing host factors. The predisposing host factors include urinary obstruction, diabetes mellitus, pregnancy, congenital anomalies of urinary tract, and catheterization, VUR and instrumentation. [3] Virulence factors of the uropathogen include: adhesins, hemolysin, capsular polysacharride, neutrophil activation etc. [4],[5],[6] In addition antibiotic resistance among uropathogens also constitute a major deciding factor in the esablishment and eradication of the disease. Before seventies multiple drug resistance was practically nonexistent and was restricted to mutation of chromosomal genes. However during the last two decades bacterial drug rsistance mediated by extra chromosomal genetic elements (plasmids), which simultaneously carry gene for resistance to number of antibiotics has made the position miserable, specifically in gram negative bacteria. Since the plasmid mediated drug resistance can be transferred to related drug sensitive bacteria, [7] the multiple drug resistance is increasing at an alarming rate, especially under the selective antibiotic pressure in the hospital environment. In the present communication we are reporting about the changing sensitivity pattern and emerging antibiotic resistance among the uropathogens during the last two years.
| € Material and Methods | |  |
Sample Collection : Out of a total of 18876 mid stream urine samples, 8180 were received during the year 1997 and 10696 during the year 1998, from the clinically suspected patients of UTI, attending the inpatient and outpatient department of DMC & H, Ludhiana. Mid stream clean catch specimen of urine was collected in a sterile, screw capped, wide mouth battle. Before collecting the sample, male subjects were asked to clean the genital part with soap and water while female patients were told to do the genital toilet using soap and water and the vulva was washed and the labia was carefully separated prior to voiding the urine, in the sterile culture bottle. [8]
Microscopic Examination
Three ml. of well mixed urine sample was centrifuged at 3000 rpm for 10 min. The supernatant was discarded and the deposit was examined microscopically [9] under 40X objective for pus cell, RBCs, epithelial cells and any other abnormal findings.
Culture
Urine samples were processed within within an hour of collection. In case, if delay of, more than one hr was unavoidable the samples were refrigerated at 4 C. The bacterial counts in the urine samples were determined by semi-quantitative method using 4 mm internal diameter standard loop. (Medical Wire & Equipment Co. Ltd., England.) The samples were inoculated on MacConkey and blood agar plates. After overnight incubation at 37 o C culture plates yielding bacttrial counts of >10 5 CFU/ml were considered as significant while counts ranging between 10 4 to 10 5 CFU/ml were taken as doubtful significant and counts below 10 4 CFU/ml were taken as not significant. [10]
Identification & Antimicrobial Susceptibility of Isolatts
Uropwthogens were identified on the basis of Gram's reaction, colony morphology and standard biochemical tests. [11] The drug sensitivity was tested on Muller Hinton agar or blood agar (for α, β and non hemolytic streptococci) modified Kerby Bauer [12] disc diffusion method using standard strains, i.e. Oxford Staphylococcus aureus NCTC 6571, Escherichia coli NCTC 10662 (Sensitive to all drugs). The concentration of each antimicrobial agent (in ug) tested per disc was Ampicillin (10), Chloramphenicol (10), Tetracycline (10), Cotrimox azole (25), Kanamycin(30), Gen tamicin(30), Cephlaxin(10), Amikacin(10), Netelmicin(10), Ceftoxime(10), Ceftazidime(10), Nalidixic Acid (10), Norfloxacin (10), Nitrofurantoin(10) and Ciprofloxacin(10).
| € Results and Discussion | | |
A total of 18876 urine samples of patients suspected to be suffering from UTI including asymptomatic pregnant females, were processed, during the year 1997 & 1998. Out of these 4935 (37%) samples were found to yield significant/doubtful significant bacteriuria (10 2 to > 10 5 ) of a single pathogen. It has been documented [13] that the presence of more than 10 5 or more organisms per ml of a single species in a freshly collected mid stream urine samples among asymptomatic pregnant females without significant pyuria indicate an active urinary tract infection. On the contrary, in asymptomatic women with pyuria yielding counts ranging betwen 10 2 - 10 4 CFU/ml of E.coli, Klebsiella, Proteus or Staphylococcus saprophyticus indicate infection and should not be disregarded. [14] However, urine is an excellent medium for many pathogens common to the urinary tract and delay in processing of samples may yield misleading results, hence, in such patients, a repeat mid stream urine sample should be cultured to confirm the causative agent of UTI. E cold was associated with more than 40%, of the clinically suspected cases of UTI during 1997, while its incidence declined to 35% during 1998. The other uropathogens encountered during 1997 were S aureus, S albus. P aeruginosa, K pneumorniae, P mirabilis, Acinetobacter species, Enterobacter aerogenes, Streptococcus feacalis and Alpha hemolytic streptococci. Similar spectrum of uropathogens was noticed with sight variations during the year 1998 [Table 1]. However there was marked increase in the UTI cases due to Proteus species during 1998 and was specifically noticed among hospitalized patients, thereby suggesting hospital acquired infection. It was observed that number of female patients were significantly higher than the number of male patients during both the years of study. The male to female ratio was approximately 1:2 and this also corroborates the previous reports i.e. UTI is more prevalent in females. [15] The antimicrobial susceptibility pattern of different organisms encountered during the year 1997 & 1998 was analyzed so as to elucidate the changing drug sensitivity pattern and emergence of resistance in uropathogens. [Table 2]. As compared to 1997 it was noticed that in the year 1998, most of the gram negative isolates depicted enhanced susceptibility towards most of the antimicrobial agents which are usually administered orally as compared to their susceptibility pattern during the year 1997. This may be attributed to the fact that most of these common antibiotics were not prescribed to the patents by the clinicians due to high level of resistance observed among uropathogens in the previous years. As a result withdrawal of these antibiotics during the recent years has led to emergence of mutants with increased susceptibility to oral antibiotics.
On the other hand, majority of the Gram negative isolates exihibited decreased susceptibility towards aminoglycosides such as Amikacin and Netilmicin which are administered parenterally. This emerging resistance towards injectable antibiotics may be attributed to the indiscriminate use of these antibiotics by the general practioners. In addition most of the gram negative isolates were moderately sensitive to third generation cephalosporins viz ceftazidime and cefotoxime (49-59%). However there was no definite correlation of susceptibility pattern of these drugs during the year 1997 & 1998 [Figure 1]. These broad spectrum antibiotics are used indiscriminately in various types of infections caused by different types of microbes which probably lead to emergence of resistance towards these newer antibiotics within a short span. [2],[16] However E coli which is the commonest cause of UTI showed markedly increased susceptibility towards third generation cephalosporins i.e. 50 to 72% and 55 to 73% in the case of cefotoxime and ceftazidime respectively. Pseudomonas which is a leading causative agent of nosocomial UTI was found to be highly susceptible (93%) to netilmicin during 1998, while it was only 53% sensitive in 1997. This may be explained by the fact that very high resistance was observed during the last few years, which led to withdrawal of these antibiotics, even by the general practioner. This withdrawal has led to the emergence of drug sensitive strains.
In contrast to Gram negative uropathogens, Gram positive isolates were found highly resistant to most of the oral antibiotics (1760%) during the years 1997 and there was a definite increase in the susceptibility of Gram positive isolates towards these oral antibiotics during 1998. As expected, in contrast to gram negative isolates, third generation cephalosporins are less effective against gram positive organisms. Among the gram positive isolates Staphylococcus species were by far are the most comb mon cne [Table 1] and were found to be highly susceptible to aminoglycosides like amikacin and netilmicin during the year 1997. However during 1998 Staphylococci showed significantly increased resistance towards these antibiotics. On the contrary these antibiotics were least effective against Streptococcus faecalis and Alpha haemolytic streptococcoi) during the year 1997. However, susceptibility towards these antibiotics has increased to some extent during the year 1998.
The quinolones viz Nalidixic acid, norfloxacin and ciprofloxacin, which are most commonly used drugs against UTI were least effective against all the uropathogens encountered during the study period. This observation positively corroborates the previous reports.[17] It has been reported that since the mechanism of action of these quinolones is almost same, emergence of resistance against one will also decrease the activity of other quinolones.
To conclude, this study lays stress upon the fact that prior knowledge of the sensitivity pattern of the pathogen is very important before prescribing an antimicrobial agent for a meaningful therapy and to avoid fast emergence of resistant mutants. Further this will also slow down the march towards a stage where we may not have any alternative as far as treatment of infectious diseases in concerned. It is implied that the national antibiotic policy be formed and religiously implemented before we are thrown back to the pre antibiotic era.
| € Summary | | |
A total of 18876 urine samples from patients of clinically suspected UTI including asymptomatic pregnant females were analysed, during the year 1997 & 1998. Culture positivity rate was found to be 37%. The incidence of Proteus was on the rise during the year 1998 especially in hospitalized patients. The antibiotic sensitivity pattern of uropathogens was also analysed to check the emergence of drug resistance. This study has revealed that withdrawal of a particular antibiotic due to high level of resistance observed during previous years, has led to re-emergence of antibiotic sensitive mutants. Further indiscriminate use of newer antibiotics like amikacin and netilimicin is responsible for emergenec of resistant variant against these antibiotics and this lays stress upon the immediate need for national antibiotic policy.
| € References | | |
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[Table 1], [Table 2]
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| Mathai E, Thomas RJ, Chandy S, et al. | | PHARMACOEPIDEMIOLOGY AND DRUG SAFETY. 2004; 13 (9): 645-652 | | [Pubmed] | |
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