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Year : 2017  |  Volume : 4  |  Issue : 1  |  Page : 23-26

Citrobacter as a uropathogen, its prevalence and antibiotics susceptibility pattern

Department of Microbiology, Jawaharlal Nehru Medical College, Aligarh Muslim University, Aligarh, Uttar Pradesh, India

Date of Web Publication19-Dec-2016

Correspondence Address:
Hiba Sami
Department of Microbiology, SRMSIMS, Bareilly, Uttar Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2348-3334.196037

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Introduction: Urinary tract infection (UTI) continues to be the most common infection diagnosed in outpatients as well as in hospitalized patients. Citrobacter spp. is an emerging urinary pathogen. The present study assessed the prevalence and antibiotic sensitivity pattern of Citrobacter spp. in patients admitted to or attending outpatient departments with Complain of UTI in a tertiary care hospital.
Materials and Methods: A total of 36,250 urine samples were included in the study. UTI was confirmed in 7099 samples. Of these 246 (3.46%) had UTI due to Citrobacter spp. Identification was by conventional biochemical methods. Antimicrobial susceptibility testing was performed using Kirby-Bauer disc diffusion method as recommended by Clinical and Laboratory Standards Institute M2-A9. Multidrug-resistant (MDR) was defined as resistance to more than two groups of drugs. Extended spectrum beta-lactamase (ESBL), AmpC, and metallo beta-lactamase (MBL) were detected by phenotypic methods. Results: Females predominated in the study 193 (78.4%) with 53 (21.5%) males. Most of the isolates were in the age group 21-30 and 31-40. 49 (19.9%) patients were inpatients, and 197 (80.08%) were outpatients. Aminoglycosides had a better spectrum of antimicrobial sensitivity (70.2%) with 85.2% isolates sensitive to amikacin. Fluoroquinolones had a poor activity against Citrobacter (46% sensitive). Ureidopenicillins had poor efficacy (15.4%). Out of the 246 strains, 129 (52.4%) were MDR, 61 (24.7%) of which were ESBL producers and 65 (26.4%) were AmpC producers. Most of the ESBL producing strains were isolated from inpatients. No MBL were identified in this study. Conclusion: Citrobacter though not uncommon isolate is posing a problem due to its MDR character. Infection control practices should be observed strictly, and any type of unnecessary instrumentation should be avoided.

Keywords: AmpC, Citrobacter, multidrug-resistant, urinary tract infection

How to cite this article:
Sami H, Sultan A, Rizvi M, Khan F, Ahmad S, Shukla I, Khan HM. Citrobacter as a uropathogen, its prevalence and antibiotics susceptibility pattern. CHRISMED J Health Res 2017;4:23-6

How to cite this URL:
Sami H, Sultan A, Rizvi M, Khan F, Ahmad S, Shukla I, Khan HM. Citrobacter as a uropathogen, its prevalence and antibiotics susceptibility pattern. CHRISMED J Health Res [serial online] 2017 [cited 2023 Mar 28];4:23-6. Available from: https://www.cjhr.org/text.asp?2017/4/1/23/196037

  Introduction Top

Urinary tract infection (UTI) is the third most common infection experienced by humans after respiratory and gastrointestinal infections. UTIs are among the most common infections in both outpatients as well as hospitalized patients. [1]

The genus Citrobacter is a distinct group of aerobic, Gram-negative bacilli of the Enterobacteriaceae family, widely distributed in water, soil, food, and intestinal tract of man and animals. Bacteria belonging to genera Citrobacter are emerging pathogens causing gastroenteritis, neonatal meningitis, septicemia, brain abscess including UTIs. [2]

Citrobacter isolates are reported to be the third most common organisms causing UTI in hospitalized patients after  Escherichia More Details coli and Klebsiella species accounting for 9.4% of all isolates. [3] Recently, the isolation of this pathogen in hospital settings across the globe is increasing, and multidrug-resistant (MDR) strains are emerging. These strains present a challenge for clinicians and clinical microbiologists alike because of their increased propensity to cause not only nosocomial infections but community acquired infection also.

UTI caused by Citrobacter spp. was seen in 12% patients in 1961, and since then, its prevalence has been gradually increasing. [4] The aim of this study was to assess the prevalence and antibiotic sensitivity pattern of Citrobacter spp. in patients with UTIs in a tertiary care hospital.

  Materials and methods Top

The study was conducted over a period of 1 year and 6 months (January 2013 to June 2014) in the Department of Microbiology Jawaharlal Nehru Medical College Hospital (JNMCH), Aligarh Muslim University, Aligarh. A total of 36,250 freshly voided midstream specimens of urine were submitted to the Clinical Microbiology Laboratory of JNMCH, Aligarh for processing. Semiquantitative urine culture using a calibrated loop was used to inoculate blood agar and MacConkey plates. [5] Inadequate urine samples, urine bag collected samples, specimens collected more than 2 h before submission, specimens submitted in leaking or unsterile containers and specimens revealing the growth of more than two types of bacteria on culture were excluded from the study. The significant pathogens were identified by standard biochemical procedures. [6] Citrobacter spp. was identified by the conventional biochemical method.

Antimicrobial susceptibility testing was done for all the isolates using Kirby-Bauer disc diffusion method as recommended by Clinical and Laboratory Standards Institute (CLSI) M2-A9. [7] The antimicrobials tested for the Gram negative bacteria were: Amikacin (30 μg), gentamicin (10 μg), ofloxacin (5 μg), ciprofloxacin (5 μg), levofloxacin (5 μg), sparfloxacin (5 μg), ceftriaxone (30 μg),cefpodoxime (10 μg), cefoperazone (CP) (75 μg), cefoperazone-sulbactam (CPS) (75 μg, 1:1), cefixime (5 μg), cefotaxime (30 μg), cefepime (30 μg) and cefepime-tazobactum (30: 10 μg) and nitrofurantoin (300 μg) as first line drugs. Second line drugs used were: Piperacillin (100 μg), piperacillin-tazobactam (100:10 μg),tobramycin (10 μg), imipenem (10 μg) which were obtained from HiMedia, India. Multidrug resistant (MDR) was defined as resistance to more than two groups of drugs.

Detection of extended spectrum and AmpC beta-lactamase

Ceftriaxone and CP were used as screening agents whereas CP-sulbactam (CPS) was used for confirmation of extended spectrum beta-lactamase (ESBL). This combination is not routinely used to confirm the production of an ESBL, but we standardized this combination against amoxicillin-clavulanic acid. The latter combination was more sensitive than the former in identifying ESBL producers (unpublished data). The cutoff zone of CP for the screening of possible ESBL was kept at 22 mm, and that of ceftriaxone was as recommended by CLSI (<25 mm). Confirmation was done on the same day by noting the potentiation of the activity of CP in the presence of CPS. [8] Organism resistant to cefoxitin, CPS, and piperacillin-tazobactam combination in addition to other cephalosporins were considered to be AmpC producers (CLSI 2003). [9]

Detection of metallo beta-lactamases

Imipenem-resistant isolates were tested for metallo beta-lactamase (MBL) production by modified Hodge test and double disc synergy test using ethylenediaminetetraacetic acid. [10]

  Results Top

Out of 36,250 urine samples, 7099 (19.6%) were culture positive. Among the isolated strains, 5466 (77%) were Gram-negative bacilli of which 4033 (73.8%) belonged to Enterobacteriaceae family. The prevalence of E. coli was far higher than of the other members of family Enterobacteriaceae.

Staphylococcus species were the most prevalent of Gram-positive pathogens 781 (11%) followed by Enterococcus spp. 419 (5.9%), Streptococcus species 220 (3.1), and Corynebacterium species 28 (0.4%) as seen in [Table 1].
Table 1: Distribution of various urinary pathogens (N=7099)

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Among the 246 (3.46%) patients positive for Citrobacter spp., 193 were females (78.4%) and 53 males (21.5%). Citrobacter koseri was the most abundant 131 (53.2%) [Figure 1] followed by Citrobacter freundii 45 (18.2%) and Citrobacter amalonaticus 24 (9. 75%). Most of the Citrobacter spp. were isolated in the 20-30 and 30-40 year age group [Figure 2]. 49 (19.9%) patients were inpatients and 197 (80.08%) were outpatients. Among first-line drugs, aminoglycosides had best spectrum of antimicrobial sensitivity (70.2%) with 210 (85.2%) isolates sensitive to amikacin. Antibiotic sensitivity pattern is shown in [Figure 3]. Among oral drugs, nitrofurantoin 163 (66.2%) was the best antibiotic followed by flouroquinolones with 45.9% sensitivity. Among fluoroquinolones, levofloxacin 135 (54.8%) was the most efficacious followed by ciprofloxacin 139 (56.5%). Cefixime was not far behind at 111 (45%) sensitivity. On comparing the cephalosporin-inactivator combinations highest sensitivity was observed in CPS followed by cefepime-tazobactam while piperacillin-tazobactam was least effective with only 57 (23.1%) sensitivity. Out of the 246 strains 129 (52.4%) were found to be MDR of which 61 (24.7%) were ESBL producers and 65 (26.4%) were AmpC producers. Most effective antimicrobial agent against Citrobacter spp. was imipenem (100%). Surprisingly, most of the ESBL producing strains were isolated from inpatients. No MBL were identified in this study.
Figure 1: prevalence of different Citrobacterspecies in urine culture

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Figure 2: Pattern of Citrobacter species in relation to age

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Figure 3: Antimicrobial susceptibility pattern of Citrobacterspecies isolated from urine

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  Discussion Top

UTIs are one of the common infections and nearly 10% people experience UTI during their lifetime. [11],[12] Early diagnosis and timely and appropriate antimicrobial treatment are considered key factors for eliminating the pathogen, preventing urosepsis, and reducing the risk of renal scarring. In this study, E. coli (65%) was the most common pathogen followed by Staphylococcus aureus (11%). Okonko et al. [13] also reported similar findings in their study. The prevalence of Citrobacter as a uropathogen in our study was 3.46% which is much lower than reported by other researchers who reported 9.4% [14],[15] but comparable to that reported by Maripandi et al. who reported it to be 1.3%. [16] In this study, almost half the patients belonged to 21-30 years age group which may point to possible higher virulence in these strains.

Most effective antimicrobial agent against Citrobacter spp. was imipenem (100%) followed by amikacin. In other study, most effective drug was again imipenem (91.8%) followed by piperacillin-tazobactam (58.3% sensitive). [14] In this study among oral drugs, nitrofurantoin was the most effective antibiotic followed by flouroquinolones with 45.9% sensitivity. Among flouroquinolones levofloxacin was most efficacious followed by ciprofloxacin. Cefixime was not far behind with 45% sensitivity.

ESBL production was observed in 61 (24.7%) isolates. 65 (26.4%) were AmpC producers. No MBL were identified in this study. The rate of the ESBL production among the Citrobacter spp. in this study was comparable to that of other studies by Ali et al. [17] and Kanamori et al. [18] , which was 36.36% and 19.3%, respectively. However, it was lower than the findings of Rizvi et al. [8] (62%) and Uma et al. [19] who had reported 86.5% among the hospital isolates. Excessive antibiotic exposure (especially the extended-spectrum cephalosporins), extended hospital stay, recent surgery, admission to the Intensive Care Unit and instrumentation are possible risk factors for the selection of the ESBL producing strains. The rate of ESBL production was also much higher in the outdoor patients also which could have been because extended spectrum cephalosporins were being prescribed injudiciously to the outpatients. The high rate of ESBL producers in our facility necessitates the testing of several cephalosporins plus inhibitor combination. It is clear from this study that one cannot use a single combination as a representative, as the three combinations, we tested, gave extremely divergent results. CPS demonstrated best activity and piperacillin-tazobactam was least effective. Every center should tailor their drug policy according to the local resistance profile.

Carbapenems are important antibiotics for the treatment of health care-associated infections and have a special role in treating infection with AmpC producing organisms. The emergence and spread of resistance to carbapenems will limit the treatment options available for treating multidrug-resistant pathogens.

  Conclusion Top

Although uncommon UTI due to Citrobacter is not only increasing but is increasingly being associated with multidrug-resistance and ESBL production. The slow but steady emergence of Citrobacter spp. as an uropathogen, resistant to commonly available antibiotics is alarming. Proper surveillance in the antimicrobial sensitivity pattern of Citrobacter is necessary, and it should no longer be ignored as a commensal.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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Barton LL, Walentik C. Citrobacter diversus urinary tract infection. Am J Dis Child 1982;136:467-8.  Back to cited text no. 2
Valencia R, Arroyo LA, Conde M, Aldana JM, Torres MJ, Fernández-Cuenca F, et al. Nosocomial outbreak of infection with pan-drug-resistant Acinetobacter baumannii in a tertiary care university hospital. Infect Control Hosp Epidemiol 2009;30:257-63.  Back to cited text no. 3
Whitby JL, Muir GG. Bacteriological studies of urinary tract infection. Br J Urol 1961;33:130-4.  Back to cited text no. 4
Beckford-Ball J. Management of suspected bacterial urinary tract infection. Nurs Times 2006;102:25-6.  Back to cited text no. 5
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, India: Elsevier; 2006. p. 131-49.  Back to cited text no. 6
Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Susceptibility Testing. Fifteenth Informational Supplement. CLSI Document M100-S15. Wayne, PA: Clinical and Laboratory Standards Institute; 2005.  Back to cited text no. 7
Rizvi M, Fatima N, Rashid M, Shukla I, Malik A, Usman A, et al. Extended spectrum AmpC and metallo-beta-lactamases in Serratia and Citrobacter spp. in a disc approximation assay. J Infect Dev Ctries 2009;3:285-94.  Back to cited text no. 8
Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Susceptibility Testing: Twenty-first Informational Supplement M100-S21. Wayne, PA, USA: CLSI; 2011.  Back to cited text no. 9
Lee NY, Chang TC, Wu CJ, Chang CM, Lee HC, Chen PL, et al. Clinical manifestations, antimicrobial therapy, and prognostic factors of monomicrobial Acinetobacter baumannii complex bacteremia. J Infect 2010;61:219-27.  Back to cited text no. 10
Delanghe JR, Kouri TT, Huber AR, Hannemann-Pohl K, Guder WG, Lun A, et al. The role of automated urine particle flow cytometry in clinical practice. Clin Chim Acta 2000;301:1-18.  Back to cited text no. 11
Hoberman A, Wald ER. Urinary tract infections in young febrile children. Pediatr Infect Dis J 1997;16:11-7.  Back to cited text no. 12
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  [Figure 1], [Figure 2], [Figure 3]

  [Table 1]

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