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Year : 2014 | Volume : 2 | Issue : 1 | Page : 5 - 7  


Original Articles
Urinary tract infection due to Staphylococcus saprophyticus in young women.

Syed Shafeequr Rahman1, R.C.Kanta2, Indu Kapur3

1Associate Professor,   2Professor,   3 Professor & HOD, Dept. of Microbiology, Malla Reddy Institute of Medical Sciences, Suraram Main Road, Quthbullapur, Hyderabad-500055

Abstract :         

Background: Staph. saprophyticus, hitherto; was considered solely as the laboratory contaminant & normal flora of the skin. Studies differ in their opinion about the incidence and age group distribution of this infection.

Objectives: To determine the prevalence of Staphylococcus saprophyticus (Staph. saprophyticus).

Methods: 200 urine specimens of women aged between 15-35 years, sexually active with symptoms of urinary tract infection, attending the hospital OPD, were analyzed.

Results: Out of 200 samples, 85 (42.5%) specimens were found positive for bacterial growth on culture. Staph. saprophyticus was isolated from the urine of two (1%) patients, indicating the low prevalence of this organism as a urinary tract pathogen in our area. Antibiogram of the organism showed susceptibility to commonly used antibiotics.

Conclusion: It is wise to subject urine samples to the identification of Staph. saprophyticus routinely for all isolates of coagulase negative Staphylococci to know the actual incidence of infection in the population.

Key words: Staphylococcus saprophyticus, urinary tract infection, young women.

Corresponding Author: Dr. Syed Shafeequr Rahman, Associate Professor, Dept. of Microbiology, Malla Reddy Institute Of Medical Sciences. Suraram Main Road, Quthbullapur, Hyderabad-500055.   Email id: rehmanshafeeq@hotmail.com

 

 

Introduction:

Staph. saprophyticus, hitherto; was considered solely as the laboratory contaminant & normal

flora of the skin. [1] Studies by Gillespie et al (1978), [2] Wallmark et al (1978), [3] and Latham et al (1983) [4] have revealed that Staph. saprophyticus was a frequent cause of acute urinary tract infection (UTI), particularly in young female patients. Reports from the studies by Choi et al (2006) [5] and Raz et al (2005) [6] reveal that complications of Staph. saprophyticus infections such as acute pyelonephritis, nephrolithiasis, septicemia and endocarditis have been documented but are all rare. Wider storm et al (2012) [7] have isolated Staph saprophyticus from human & animal G-I tract , meat & cheese products, vegetables and environmental sources. Wallmark et al (1978) [3] showed that Staph. saprophyticus is a frequent cause of UTI in young female, whereas Hovelius et al (1984) [8] reported that UTI due to Staph. saprophyticus is rarely seen in elderly males with obstructive disorders. The above contradictory observations place the Staph. saprophyticus as a worthy candidate for further study.

Materials & Methods:

The present study was conducted after obtaining the Institutional Ethical Committee Clearance.

Urine cultures:

200 urine specimens were obtained by clean void method from young women, who presented with symptoms of urinary tract infection between July 2012 and September 2013, at Malla Reddy Hospital, Hyderabad. All specimens were examined microscopically and by quantitative culture. [2] Primary plating media used was Blood Agar, Mac Conkey Agar, Nutrient Agar & Milk salt Agar. Urine was inoculated in all plates with a 0.01 ml calibrated loop. Inocula were then streaked for colony isolation. Culture plates were incubated aerobically at 370c for 24 hours. Staphylococcal isolates grown on Blood agar, Nutrient agar & Milk Salt agar plates were identified by colony morphology, gram stain, catalase and coagulase tests (slide and tube tests). Coagulase negative Staphylococci were identified by standard methods [9, 10, and 11] for species differentiation. Resistance to novobiocin was assessed by a zone diameter of less than 16mm, surrounding a 5µg novobiocin disk.

Streptococci, Coliform bacilli and other isolates were identified by methods described by J.G. Collee et al. [12] Antibiotic sensitivity test of the isolates was done by Kirby-Bauer disc diffusion technique as per the CLSI guidelines 2012, [13] using Penicillin G, Oxacillin, Gentamycin, Ciprofloxacin, Co-trimoxazole, Vancomycin, Tetracycline, Norfloxacin, Nitrofurantoin, standard discs obtained from Hi-Media.

Results:

Urine microscopy was done on an uncentrifuged specimen from 200 patients. In 55(27.5%) of the specimens, pyuria was observed, and 8(4%) showed hematuria (more than an occasional white blood cell or red blood cell per high power field). [14] Out of 85 (42.5%) specimens which showed bacterial growth on culture, 53 (26.5%) were found to have urinary tract infection with pyuria and colony counts of 104 CFU/ml and above (Table 1).

Aerobic bacterial isolates are shown in Table 1 and out of 85(42.5%) specimens, coagulase

negative Staphylococci were 27, which included Staph. saprophyticus (2), Staph. hemolyticus (5) and Staph. epidermidis (20).

Other pathogens isolated were Escherichia coli (31), Klebsiella sp (18), Proteus mirabilis (2),

Pseudomonas sp (4), coagulase positive Staphylococci (4), Beta hemolytic Streptococci (3)

Enterococci (1) and Corynebacterium sp (6).

Characteristic features of Staph. saprophyticus isolates:

Two strains of Staph. saprophyticus were isolated in our study. Both the isolates grew in pure cultures with colony counts of 104 and >105 CFU/ml respectively and were associated with pyuria. Colonies of both the isolates were non-hemolytic on blood agar. Biochemical tests showed them to be urease producers and fermenters of sucrose and trehalose. The two patients from whom these organisms were isolated were 19 yrs & 35 yrs of age; married and not pregnant.  

Antibiogram   of Staph. saprophyticus:

Both the isolates were found to be susceptible to commonly used antibiotics like Nitrofurantoin, Co-trimoxazole, Ciprofloxacin, Gentamycin and Tetracycline. As per the standard identification criteria, both the isolates were found resistant to Novobiocin.                                                                         

Discussion:

Pereira (1962) [15] and Mitchell (1964, 1968) [16, 17] established one variety of coagulase negative Staphylococcus as a primary pathogen of normal female urinary tract. This organism, subsequently named as Micrococcus sub group 3, is now renamed as Staph. saprophyticus biotype 3 (Buchanan and Gibbons 1974). [18] It has been shown by several workers to be a common cause of primary urinary infection in young women   (Mabeck 1969, [19] Kerr 1973, [20] Maskell 1974, [21] Meers 1974, [22] Sellin et al 1975, [23] Sheikh et al 2012[24]). Staph. saprophyticus differs from others coagulase negative Staphylococci, in being more virulent for the urinary tract of young women for reasons that are still obscure. Various studies demonstrating virulence properties like mouse virulence, [25] urease activity and adherence to urothelial cells [26] have shown that Staph. saprophyticus has got some undefined advantage over other coagulase negative Staphylococci in causing UTI.

Our study comprised of 200 young married women, with a mean age of 25.2% years. Staph.

saprophyticus was identified as an aetiological agent in the urine specimens of only 2(1%)

cases. Other 25 (12.5%) coagulase negative Staphylococci, identified in this group included

Staph. hemolyticus 5 (2.5%) and Staph. epiderimidis 20 (10%). The low incidence of urinary

infections caused by Staph. saprophyticus (1%) in our study, does not match with the data (7% to 42%) published by European and American investigators in a similar population. [14] This discrepancy probably reflects differences in the study population[27]. Some practitioners still regard Staph. saprophyticus as a contaminant & consequently the infections may not be correctly treated. This is probably because other coagulase negative Staphylococci are indeed common contaminants in urine. [1]  

Conclusions:

Based on the report of many workers, also ours, that it is wise to subject urine samples to the isolation & identification of Staph. saprophyticus routinely. For all isolates of coagulase negative Staphylococci it is worthwhile knowing the actual incidence of urinary tract infection due to Staph. saprophyticus in the population. Studies from South India (Asangi et al 2011, [27] Usha et al 2013[28]) indicate the low incidence of Staph. saprophyticus from clinical samples. Despite its low incidence, this organism needs to be under surveillance before it can emerge as a devastating pathogen.

A simple laboratory protocol for its identification should include test for novobiocin resistance, and absence of hemolysis on blood agar.

Table 1: Organisms isolated showing colony counts of =>104 cfu/ml in urine samples with pyuria

SL.

NO

ORGANISM

GROWTH   +VE        ISOLATES

   (85 PATIENTS)

NO.OF    ISOLATES     =>104 CFU/ml

(53 PATIENTS)

   

       %

1.

Escherichia coli

31

22

71.0

2.

Klebsiella sp.

18

10

55.6

3.

Proteus mirabilis

  2

  2

100.0

4.

Pseudomonas sp.

  4

  1

25.0

5.

Enterococci

  1

  1

100.0

6.

Beta hemolytic Streptococci

  3

  2

66.7

7.

Coagulase positive Staphylococci

  4

  3

75.0

8.

Staph. saprophyticus

  2

  2

100.0

9.

Other Coagulase negative Staph

25

  9

36

10.

Corynebacterium sp.

  6

  1

16.7

 

TABLE 2: Organisms isolated in young married women in relation to age.

 

SL.NO

ORGANISM

No.of Samples   showing Growth

           Growth of Organism

in < 25 years of age

in => 25 years of age

No.

%

No.

%

1.

Escherichia coli

31

24

77.4

7

22.6

2.

Klebsiella sp.

18

9

50.0

9

50.0

3.

Proteus mirabilis

2

1

50.0

1

50.0

4.

Pseudomonas sp.

4

1

25.0

3

75.0

5.

Enterococci

1

1

100.0

0

0.0

6.

Beta hemolytic Streptococci

3

2

66.7

1

33.3

7.

Coagulase positive Staphylococci

4

3

75.0

1

25.0

8.

Staph. saprophyticus

2

1

50.0

1

50.0

9.

Other Coagulase negative Staphylococci

25

14

56.0

6

24.0

10.

Corynebacterium sp.

6

4

66.7

2

33.3

 

 

 

 

                                              

TABLE 3: Antibiogram of Staph. saprophyticus

 

Antibiotic   name

Breakpoints

Number of

isolates

% R

% I

% S

Penicillin G

S >= 29 mm

2

100

0

0

Oxacillin

11 - 12 mm

2

50

0

50

Gentamicin

 

13 – 14 mm

2

0

0

100

Ciprofloxacin

16 – 20 mm

2

0

0

100

Co-trimoxazole

11 – 15 mm

2

0

0

100

Vancomycin

S >= 15 mm

2

0

0

100

Tetracycline

15 – 18 mm

2

0

0

100

Norfloxacin

13 – 16 mm

2

50

0

50

Nitrofurantoin

15 – 16 mm

2

0

0

100

R = Resistant,   I = Intermediate, S = Susceptible

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Acknowledgement: We thank Dr. Chandrakant Shirole, Dean, Malla Reddy Institute Of Medical Sciences, Dr. Bhadra Reddy, Dr Preeti Reddy, the Directors, Malla Reddy Institutions of Medical and Dental Sciences, Hyderabad for their encouragement and for allowing the work to be published.

Source of Support: Nil. Conflict of Interest: None.

 

 





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