Emerging of Multidrug Resistance Human Pathogens from Urinary Tract Infections

MATERIALS AND METHODS

A total of 10 midstream urine samples were collected from adult patients (aged 18-60 years) having community-acquired UTIs and who were referred to the Government Hospitals, Tamilnadu, India, during the period, March 2009. Each sample was inoculated on both blood agar (with 5% sheep blood) and MacConkey agar plates and incubated at 37°C for 24-48 h and a total 73 number of colonies was counted. Significant growth was identified biochemically and serologically in a systematic way according to standard methods (Vandepitte et al., 1996). Susceptibilities of the common isolated bacteria (E. coli, Enterococcus faecalis, Klebsiella pneumonia, Serratia marcescens, Pseudomonas aeruginosa, S. saprophyticus, Staphylococcus aureus and Proteus sp.) to certain antimicrobial agents causing UTI were examined.

Antimicrobial sensitivity testing of all isolates was performed on diagnostic sensitivity test plates by the Bauer et al. (1966), following the definition of the National Committee of Clinical Laboratory Standards (NCCLS, 1999). Bacterial inoculum were prepared by suspending the freshly-grown bacteria in 25 mL sterile nutrient broth. A sterile cotton swab was used to streak the surface of Mueller Hinton agar plates. Filter paper disks containing designated amounts of the antimicrobial drugs obtained from commercial supply firms (Himedia Labs, Mumbai, India) were used. The antimicrobial agents tested were Amoxicillin 10 μg, Cephalexin 30 μg, Gentamycin 10 μg, Nalidixic acid 30 μg, Ciprofloxacin 10 μg, Cotrimoxazole 10 μg and Trimethoprimsulfamethoxazole (SXT) 30 μg.

RESULTS AND DISCUSSION

A summary of the different microorganisms isolated during the study period was shown in Table 1. It is clear that E. coli was the predominant uropathogen (31.5%) causing UTI, followed by Staphylococcus aureus (20.5%), Klebsiella pneumonia (15.8%), Proteus sp. (7.4%) and Pseudomonas aeruginosa (7.5%). However, Enterococcus faecalis, Staphylococcus saprophyticus and Serratia marcescens were the least dominant uropathogen causing UTI strains. The findings of this study was compared favorably to Akortha and Ibadin (2008) who found that S. aureus strains were sensitive and highly resistant to naladixic acid (79.3%). Shittu and Mandara (1999) reported that S. aureus as 100% sensitive to gentamycin and cephalosporin. According to this result, major isolates in UTI were E. coli, followed by S. aureus, S. saprophyticus, Proteus sp. and E. faecalis. These observations were supported by several studies conducted previously. According to Goswami et al. (2001), E. coli is the most common organism (64.3%), followed by S.aureus (21.4%) and Klebsiella pneumoniae (14.3%).

The percentages of resistance of all isolates to the antimicrobial agents were: 83.3% to SXT, 80.6% to Nalidixic acid, 67.3% to Amoxycillin, 61% to Cotrimoxazole, 48.8% to Gentamycin, 46% to ciprofloxacin and 43% to cephalexin. The percentages of pathogens resistance varied between 83.3 and 43% to the antimicrobial agents, while in susceptible of the pathogens varied between 56.3 and 16.7% (Table 2). The present study evaluated the prevalence of micrograms implicated in UTI to ascertain their antimicrobial resistance patterns. In this study, the isolates demonstrating, extremely high percentage of MDR phenotype. A significant increase in resistance of pathogenic strains to SXT, Ampicillin and Cephalothin has been found worldwide (Hooton, 2003) but older agents like Gentamicin that still show high efficacy against UTI pathogens because of its multiple mechanisms of action seem to have enabled it to retain potent activity against pathogens.

Table 1:	Percentage of UTI isolate among the pathogens

Table 2:	Percentage of resistance to the antimicrobial agents among 73 UTIs isolates

The overall rate of resistance to SXT was significant and higher than those reported by Valdivieso et al. (1999) and Zhanel et al. (2000). For the past decades, SXT or trimethoprim alone has been used widely as an empirical therapy for urinary tract infections caused by E. coli. The results of this study indicate that a ciprofloxacin resistant phenotype without concurrent resistance to other antimicrobials was higher than previous reported studies (Sahm et al., 2001a). A decline in the activity of ciprofloxacin would be especially problematic in view of the ability of gram-negative bacilli to acquire resistance to all other classes of antimicrobials (Sahm et al., 2001b). Present study shows that resistance to ciprofloxacin continues to increase. If urgent measures would not be taken to arrest the situation, we may see the return of the era of the search for new drugs to fight bacterial infections.

In this study, we found multidrug resistance strains which are resistant to most of the antimicrobials agent tested. This reflected the fact that ampicillin, tetracycline and streptomycin were the most commonly prescribed antibiotics in the hospital even before the results of urine analyses and also the most easily available in the market without prescription and because they were also very cheap in terms of cost. The widespread use and more often the misuse of antimicrobial drugs has led to a general rise in the emergence of resistant bacteria. Higher resistant strains were reported in USA to ampicillin and cotrimoxazole (Sahm et al., 2001b). Where as few ciprofloxacin resistant strains were found in other countries (Diekema et al., 2004). This study also noticed ciprofloxacin-resistant E. coli from UTIs. Ciprofloxacin as an option for therapy to UTIs has been considered, since its multiple mechanisms of action seem to have enabled it to retain potent activity against E. coli. Ciprofloxacin has high level of activity against UTI isolates of E. coli compared with other commonly used agents, such as Ampicillin and SXT (Gupta et al., 1999).

Table 3 gives the multi drug resistance profile of various isolates to the routinely used antibiotics. Isolated UTI strains were tested for susceptibility against antibiotics, few of the antibiotics were sensitive but most of antibiotics showed resistant to the MDR strains. Among this E. coli, K. pneumoniae and P. aeruginosa were highly resistance to most of the antibiotics, whereas Staphylococcus sp. and Serratia marcescens exhibited sensitive to Cephalexin, Cotrimoxazole and Gentamycin. Moreover, most the UTI strains were highly resistance to nalidixic acid and SXT. Drug resistance is one of nature’s never ending process by which the organisms develop tolerance to new environmental condition. It may be due to a pre-existing factor in the organisms or result from the acquired factor(s).

Table 3:	Antimicrobial susceptibility pattern for MDR- UTI isolates
AMX = Amoxycillin; CF = Cephalexin; GM = Gentamycin; NA = Nalidixic acid; CIP = Ciprofloxacin; CO = Cotrimoxazole; SXT = Trimethoprimsulfamethoxazole; R = Resistant; S = Sensitive

Rella and Haas (1982) first reported that a nalidixic acid resistant P. aeruginosa of UTI showed resistance to β-lactam antibiotics. The finding of this study coincides with Shittu and Mandere (1999) that S. aureus strains were highly resistant to naladixic acid. All the isolates in this study showed resistance to at least 5 different antibiotics, indicating the presence of strong selective pressures from the antibiotics in the community. Brown et al. (2003) have reported that horizontal gene transfer is a factor in the occurrence of antibiotic resistance in clinical isolates and suggested that the high prevalence of resistance to a particular antibiotic does not always reflect antibiotic consumption as previously suggested by Nwanze et al. (2007).

According to Mandal et al. (2001), E. coli as the commonest cause of UTI and antibiotic resistance was high among the strains which emphasize the need for judicious use of antibiotics. Certain virulence factors like haemolysin production and presence of fimbriae in the E. coli may be associated with urovirulence. Moreover, these differences in sensitivity pattern of the isolates could be attributed to time difference between the two studies or environmental factors such as practices of self medication, the drug abuse and indiscriminate misuse of antibiotics among the general population which has favoured the emergence of resistance strains.

CONCLUSION

The susceptibility and resistance profile of all isolates in this study have shown that Trimethoprimsulfamethoxazole and Nalidixic acid possess the higher efficacy while Ciprofloxacin and Cephalexin possess lower efficacy. Despite this efficacy, there was a general increase in the resistance pattern of isolates to all the antibiotics used in this study. The present study confirms that bacterial resistance would be a greatest problem in the country but, still some bacteria are resistant to antibiotics especially, Cephalexin and Ciprofloxacin, frequently used drugs in many parts of the world.

ACKNOWLEDGMENT

The authors would like to acknowledge, The Head, Department of Marine and Coastal Studies, Madurai Kamaraj University. The author wishes to express high appreciation and gratitude to the Government Hospital, Tamilnadu, India, for their efforts in the preparation of this study.