|Year : 2015 | Volume
| Issue : 1 | Page : 26-30
Increasing antimicrobial resistance among uropathogens: Is fosfomycin the answer?
Asfia Sultan, Meher Rizvi, Fatima Khan, Hiba Sami, Indu Shukla, Haris M Khan
Department of Microbiology, Jawaharlal Nehru Medical College, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
|Date of Submission||20-Feb-2014|
|Date of Acceptance||10-Apr-2014|
|Date of Web Publication||6-Jan-2015|
Department of Microbiology, Jawaharlal Nehru Medical College, Aligarh Muslim University, Aligarh, Uttar Pradesh
| Abstract|| |
Introduction: Urinary tract infection (UTI) is one of the most common infectious diseases in clinical practice. The choice of antibiotics for the treatment of UTI is limited by the rising rates of antibiotic resistance. There is an urgent need to discover new effective treatment solutions. Fosfomycin may be an interesting alternative to the currently used treatments of UTIs.
Materials and Methods: The study was conducted over 6 months period (January to June 2013) in Department of Microbiology, JNMCH, AMU, Aligarh. A total of 1840 urine samples were submitted. Culture and sensitivity was done as per standard microbiological procedures. Methicillin-resistant Staphylococcus aureus (MRSA), high-level aminoglycoside resistance (HLAR), extended spectrum beta-lactamases (ESBL), AmpC and metallo-beta-lactamases (MBL) production was detected.
Results: Culture was positive in 504 (27.4%) cases. Gram-negative etiology was identified in 390 (73%) cases. ESBL production was detected in 154 (37.1%) while 82 (21.6%) were Amp C. No, MBL was detected. Among Gram-positive bacteria, 68 (51.5%) were MRSA, while 4 (13.3%) were vancomycin resistant enterococci (VRE). HLAR was seen in 53.3% of enterococci. Fosfomycin was effective in 100% of MRSA, VRE, ESBL, HLAR, and overall, susceptibility to fosfomycin in AmpC producers was extremely high (99%). Norfloxacin and cotrimoxazole were not proved effective as only three isolates were sensitive to norfloxacin, while all Gram-negative isolates were resistant to cotrimoxazole. Pseudomonas species showed 65% and 75% susceptibility to colistin and polymixin B, respectively.
Conclusion: Fosfomycin has emerged as a promising option, especially in cases involving multi-drug-resistant pathogens in which previous antibiotics have failed to cure the infection.
Keywords: Enterobacteriaceae , fosfomycin, muti-drug resistant, urinary tract infection
|How to cite this article:|
Sultan A, Rizvi M, Khan F, Sami H, Shukla I, Khan HM. Increasing antimicrobial resistance among uropathogens: Is fosfomycin the answer?. Urol Ann 2015;7:26-30
|How to cite this URL:|
Sultan A, Rizvi M, Khan F, Sami H, Shukla I, Khan HM. Increasing antimicrobial resistance among uropathogens: Is fosfomycin the answer?. Urol Ann [serial online] 2015 [cited 2020 May 30];7:26-30. Available from: http://www.urologyannals.com/text.asp?2015/7/1/26/148585
| Introduction|| |
Over 150 million episodes of urinary tract infections (UTIs) occurs annually in the world.  It accounts for a large proportion of antibiotic consumption and has a large socioeconomic impact and may contribute to bacterial resistance.  Clinicians often face problems in choosing appropriate antibiotic therapy for treating UTIs caused by multi-drug-resistant (MDR) bacteria.  The emergence of extended spectrum beta-lactamases (ESBL), AmpC production by Gram-negative bacteria and methicillin resistant Staphylococcus species further limits the choice of antimicrobials. 
Fosfomycin trometamol may be an interesting alternative to the currently used treatments of UTIs. It is a well-tolerated drug and has a broad spectrum of activity. The aim of this study was to assess the susceptibility profile of uropathogens against fosfomycin, norfloxacin, cotrimoxazole, polymyxin B and colistin apart from the other routine antibiotics.
| Materials and methods|| |
Sample collection and analysis
The study was conducted over a period of 6 months (January 2013 to June 2013) in the Department of Microbiology JNMCH, AMU, Aligarh. Total 1840 freshly voided midstream specimens of urine were submitted to the Clinical Microbiology Laboratory of JNMCH, Aligarh for processing. Semi quantitative urine culture using a calibrated loop was used to inoculate blood agar and MacConkey plates.  Following the recommendations of Kass  in distinguishing genuine infection from contamination, significant monomicrobial bacteriuria was defined as culture of a single bacterial species from the urine sample at a concentration of >10 5 cfu/ml. Inadequate urine samples (<10 ml urine), urine bag collected samples, specimens collected more than 2 h before submission, specimens submitted in leaking, or dirty unsterile containers and specimens revealing growth of more than two types of bacteria on culture were excluded from the study. The significant pathogens were identified by standard biochemical procedures. 
Antibiotic susceptibility testing
Antimicrobial susceptibility testing of all isolates was performed on Mueller Hinton agar by Kirby-Bauer disk diffusion method for fosfomycin (50 μg) and norfloxacin (5 μg). Along with these, the susceptibility to the following antimicrobial agents was also performed as per clinical laboratory standards institute guidelines.  All the disc were obtained from Hi-Media Laboratories, Mumbai, India.
Gram-negative isolates: Cotrimoxazole (1.25/23.75 μg), amikacin (30 μg), gentamicin (10 μg), ofloxacin (5 μg), ceftriaxone (30 μg), cefoperazone (CP) (75 μg), cefoperazone-sulbactam (CPS) (75 μg, 1:1), cefixime (5 μg) cefotaxime (30 μg), cefepime (30 μg) and ceftriaxone-salbactam (30/15 μg) as first line drugs. Pathogens resistant to these drugs were considered multi-drug-resistant and were tested against second line drugs: Piperacillin (100 μg), piperacillin-tazobactam (100:10 μg), tobramycin (10 μg), imipenem (10 μg), polymyxin B (300 μg) and colistin (10 μg).
Pseudomonas spp.: Piperacillin (100 μg), piperacillin-tazobactam (100:10 μg), tobramycin (10 μg), imipenem (10 μg), ticarcillin (75 μg), polymyxin B (300 μg), and colistin (10 μg).
Gram-positive isolates: Amikacin (30 μg), gentamicin (10 μg), levofloxacin (5 μg), sparfloxacin (5 μg), erythromycin (15 μg), vancomycin (30 μg), oxacillin (1 μg), tobramycin (10 μg), clindamycin (2 μg), and amoxicillin (30 μg).
Detection of extended spectrum and AmpC beta lactamase
Screening of possible ESBL production was done by using ceftriaxone (30 μg) and CP (75 μg). Isolates showing zone diameter less than 25 mm for ceftriaxone and less than 19 mm for CP were subsequently confirmed by disc potentiation test using CP and CPS combination.  Organism sensitive to cefoxitin and resistant to cefoperazone-salbactam and piperacillin-tazobactam combination were considered to be Amp C producers. 
Detection of metallo-beta-actamases
Imipenem resistant isolates were tested for metallo-beta-lactamases (MBL) production by modified Hodge test and Double Disc synergy test using EDTA. 
Screening for methicillin resistance in Staphylococcus species and high-level aminoglycoside resistance in enterococci
Test was performed on Muller Hilton agar with 4% NaCl using oxacillin 1 μg disc. Isolates showing a reduction in zone size <13 mm were considered resistant.
In case of enterococci, high-level aminoglycoside resistance (HLAR) was detected using high content gentamycin (120 μg) and streptomycin (300 μg).
| Results|| |
Of 1840 urine samples, 504 (27.4%) were culture positive. Majority were females (n = 1474) 76% and the female to male ratio was 4:1. Among the isolated strains, 390 (77%) were Gram-negative bacilli of which 372 (73.8%) belonged to Enterobacteriaceae family. In the Enterobacteriaceae group, the frequency of Escherichia coli and Klebsiella pneumoniae were 90% and 6%, respectively. Etiological profile is shown in [Table 1]. In addition, 4% of total isolates were nonenterobacteriaceae Gram-negative organisms, among which Pseudomonas aeruginosa (3.4%) predominated followed by Acinetobacter (0.4%).
The frequency of Gram-positive pathogens was 66 (13%) for Staphylococcus spp., 30 (6%) for Enterococcus spp., 16 (3%) for Streptococcus species and 2 (0.4%) for Corynebacterium species.
Antibiotic Susceptibility patterns of most frequent uropathogens to different antibiotics are shown in [Table 2] and [Table 3].
|Table 3: Sensitivity pattern of ESBL producing, non-ESBL and AmpC producing strains|
Click here to view
Among Gram-positive bacteria, the highest level of susceptibility was observed for vancomycin (96%) followed by nitrofurantoin (85.7%). Erythromycin and fluoroquinolones were effective in 58.9% and 44.6% of Gram-positive isolates, respectively. Staphylococcus species showed 96% susceptibility to both amikacin and gentamycin. Isolates of Corynebacterium spp., (n = 2) were resistant to oxacillin, nitrofurantoin, and levofloxacin.
All the Gram-negative bacteria were sensitive to imipenem. Amikacin showed good results being effective in 96.39% isolates while CPS and piperacillin-tazobactam were effective in 74% of isolates. 69% and 40% isolates were sensitive to gentamicin and ofloxacin, respectively. Pseudomonas species showed 65% and 75% susceptibility to colistin and polymixin B, respectively.
On further analyzing the MDR isolates, 154 (37.1%) were ESBL producers, 82 (21.6%) were Amp C. No, MBL was detected. Among Gram-positive bacteria, 68 (51.5%) were methicillin-resistant Staphylococcus aureus (MRSA) while 4 (13.3%) were vancomycin resistant enterococci (VRE). HLAR was seen in 53.3% of enterococci. Other two drugs norfloxacin and cotrimoxazole were not proved effective as only three isolates were sensitive to norfloxacin, while all Gram-negative isolates were resistant to cotrimoxazole. Fosfomycin was effective in 100% of MRSA, VRE, ESBL, HLAR, and overall, susceptibility to fosfomycin in AmpC producing isolates was extremely high (99%).
| Discussion|| |
This study was conducted to evaluate the potential of certain older antibiotics in the treatment of UTIs, especially against MDR pathogens. In our study, E. coli (65%) was the most common pathogen followed by S. aureus (11%). Okonko et al.  also reported similar findings in their study.
Prevalence of ESBL (37.1%) and AmpC (21.6%) production was consistent with that reported by Taneja et al.  Among Gram-positive bacteria a high percentage of MRSA (51.5%), VRE (13.3%) and HLAR (53.3%) was observed. All these findings are higher than our previous reports  which points to exonerable increase in drug resistance.
Compared to other antibiotics, aminoglycosides, carbepenems, glycopeptides and colistin showed good results, but all these are parenteral antibiotics. Limited options of oral antibiotics are available for the treatment of UTI. The current study demonstrated significant resistance to cotrimoxazole and norfloxacin, which concur with reports of previous studies. , The other two oral antibiotics, which were tested in this study were nitrofurantoin and fosfomycin, but nitrofurantoin showed decreased susceptibility against MDR bacteria. As high as 99% of the MDR isolates were sensitive to fosfomycin in our study.
Fosfomycin has emerged as a promising treatment option. It has rare adverse reactions which develop in 1-8% of all patients, with the most common ones being diarrhea, nausea, vomiting, skin rash, heartburn, vaginitis, headache, chills and asthenia.  Fosfomycin has a low molecular weight and a relatively long half-life (mean half-life-SD, 5.7-2.8 h) and therefore, penetrates various tissues with ease, achieving the minimum inhibitory concentrations needed to inhibit the growth of most pathogens.  Resistance rate is low and most frequently acquire by chromosomal mutations that do not spread easily.  Clinical studies have shown fosfomycin to be effective for the treatment of lower UTIs due to ESBL-producing members of the Enterobacteriaceae. , In our study, all the sensitive and ESBL producing strains showed 100% sensitivity to fosfomycin while 98.7% of AmpC producers were sensitive to this drug. It has previously been reported by other authors that fosfomycin has good in vitro activity against ESBL producing E. coli and K. Pneumoniae. , Fosfomycin has been reported to have high activity against the majority of Enterobacteriaceae, but not toward the Gram-positive bacteria.  However, in our study 100% of VRE isolates showed susceptibility to fosfomycin. This finding is in concordance with study of Shrestha et al.  who reported 98.7% of sensitivity among VRE isolates to fosfomycin.
In previous studies, around 10% of strains of P. aeruginosa, were resistant to fosfomycin.  Current studies on P. aeruginosa isolates demonstrated higher rates of resistance to fosfomycin in vitro.  However, our P. aeruginosa isolates showed 100% susceptibility to fosfomycin. This finding could be because most of P. aeruginosa isolates were sensitive strains. Polymyxin B and colistin also demonstrated good results against Pseudomonas spp.
Further studies are needed, but fosfomycin appears to have an excellent potential as a possible oral option for the treatment of MDR Gram-positive as well as Gram-negative pathogens. However, increased usage has been shown to correlate with increasing resistance among ESBL-producing strains. 
| Conclusion|| |
Fosfomycin is a bactericidal agent showing low level of resistance as compared to other antibiotics. Antimicrobial activity of fosfomycin, especially against MDR pathogens, makes it an effective and safe drug in the treatment of UTIs due to Gram-positive and Gram-negative bacteria, especially in cases involving MDR pathogens in which previous antibiotics have failed to cure the infection or when patients are intolerant to the antibiotics considered as first-line treatment agents.
| References|| |
Stamm WE, Norrby SR. Urinary tract infections: Disease panorama and challenges. J Infect Dis 2001;183 Suppl 1:S1-4.
Grude N, Tveten Y, Kristiansen BE. Urinary tract infections in Norway: Bacterial etiology and susceptibility. A retrospective study of clinical isolates. Clin Microbiol Infect 2001;7:543-7.
Falagas ME, Giannopoulou KP, Kokolakis GN, Rafailidis PI. Fosfomycin: Use beyond urinary tract and gastrointestinal infections. Clin Infect Dis 2008;46:1069-77.
Rizvi M, Khan F, Shukla I, Malik A, Shaheen. Rising prevalence of antimicrobial resistance in urinary tract infections during pregnancy: Necessity for exploring newer treatment options. J Lab Physicians 2011;3:98-103.
Beckford-Ball J. Management of suspected bacterial urinary tract infection. Nurs Times 2006;102:25-6.
Girou E, Rioux C, Brun-Buisson C, Lobel B, Infection Committee of the French Association of Urology. The postoperative bacteriuria score: A new way to predict nosocomial infection after prostate surgery. Infect Control Hosp Epidemiol 2006;27:847-54.
Collee JG, Fraser AG, Marmion BP, Simmons A. Tests for the identification of bacteria. In: Collee JG, Miles RS, Watt B, editors. Mackey and McCartney Practical Medical Microbiology. 14 th
ed. New Delhi: Elsevier; 2006. p. 131-49.
Lee K, Chong Y, Shin HB, Kim YA, Yong D, Yum JH. Modified Hodge and EDTA-disk synergy tests to screen metallo-beta-lactamase-producing strains of Pseudomonas
species. Clin Microbiol Infect 2001;7:88-91.
Rizvi M, Fatima N, Rashid M, Shukla I, Malik A, Usman A, et al
. Extended spectrum AmpC and metallo-beta-lactamases in Serratia
spp. in a disc approximation assay. J Infect Dev Ctries 2009;3:177-86.
Clinical and Laboratory Standards Institute 2003. Performance Standards for Antimicrobial Susceptibility Testing: Eighteenth Informational Supplement: Approved Standards M100-S18. Baltimore, USA: Clinical and Laboratory Standards Institute; 2008.
Okonko IO, Ijandipe LA, Ilusanya AO, Donbraye-Emmanuel OB, Ejembi J, Udeze AO, et al
. Incidence of UTI among pregnant women in Ibadan South-Western Nigeria. Afr J Biotechnol 2009;8:6649-57.
Taneja N, Rao P, Arora J, Dogra A. Occurrence of ESBL and Amp-C beta-lactamases and susceptibility to newer antimicrobial agents in complicated UTI. Indian J Med Res 2008;127:85-8.
Moyo SJ, Aboud S, Kasubi M, Maselle SY. Bacterial isolates and drug susceptibility patterns of urinary tract infection among pregnant women at Muhimbili National Hospital in Tanzania. Tanzan J Health Res 2010;12:236-40.
Gupta V, Rani H, Singla N, Kaistha N, Chander J. Determination of extended-spectrum â-lactamases and ampc production in uropathogenic isolates of Escherichia coli and susceptibility to fosfomycin. J Lab Physicians 2013;5:90-3.
Ruxer J, Mozdzan M, Siejka A, Loba J, Markuszewski L. Fosfomycin and nitrofurantoin in the treatment of recurrent urinary tract infections in type 2 diabetic women: A preliminary report. Diabetol Do?w i Klin 2006;6:277-282.
Kobayashi S, Kuzuyama T, Seto H. Characterization of the fomA and fomB gene products from Streptomyces
wedmorensis, which confer fosfomycin resistance on Escherichia coli
. Antimicrob Agents Chemother 2000;44:647-50.
Falagas ME, Kastoris AC, Kapaskelis AM, Karageorgopoulos DE. Fosfomycin for the treatment of multidrug-resistant, including extended-spectrum beta-lactamase producing, Enterobacteriaceae
infections: A systematic review. Lancet Infect Dis 2010;10:43-50.
Senol S, Tasbakan M, Pullukcu H, Sipahi OR, Sipahi H, Yamazhan T, et al
. Carbapenem versus fosfomycin tromethanol in the treatment of extended-spectrum beta-lactamase-producing Escherichia coli
-related complicated lower urinary tract infection. J Chemother 2010;22:355-7.
Maraki S, Samonis G, Rafailidis PI, Vouloumanou EK, Mavromanolakis E, Falagas ME. Susceptibility of urinary tract bacteria to fosfomycin. Antimicrob Agents Chemother 2009;53:4508-10.
Rubin RH, Beam TR Jr, Stamm WE. An approach to evaluating antibacterial agents in the treatment of urinary tract infection. Clin Infect Dis 1992;14 Suppl 2:S246-51.
Shrestha NK, Chua JD, Tuohy MJ, Wilson DA, Procop GW, Longworth DL, et al
. Antimicrobial susceptibility of vancomycin-resistant Enterococcus faecium
: Potential utility of fosfomycin. Scand J Infect Dis 2003;35:12-4.
Barry AL, Fuchs PC. In vitro
susceptibility testing procedures for fosfomycin tromethamine. Antimicrob Agents Chemother 1991;35:1235-8.
Lu CL, Liu CY, Huang YT, Liao CH, Teng LJ, Turnidge JD, et al
. Antimicrobial susceptibilities of commonly encountered bacterial isolates to fosfomycin determined by agar dilution and disk diffusion methods. Antimicrob Agents Chemother 2011;55:4295-301.
Oteo J, Bautista V, Lara N, Cuevas O, Arroyo M, Fernández S, et al
. Parallel increase in community use of fosfomycin and resistance to fosfomycin in extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli
. J Antimicrob Chemother 2010;65:2459-63.
[Table 1], [Table 2], [Table 3]