In infection. Studies have indicated that positivity in

the present study the prevalence of stones with infection was 68(30.7%). Hamid
shafi et al has reported a Positive stone culture as 10(22.2%) . Sohshany HL et al has reported 47%
culture positivity in calculi and urine specimens.(15)Mariappan et al has
showed a  stone culture positivity of 35.2%
. We
also compared the culture positivity rate of infection stone with the urine
samples collected from the same patients and 49 samples (72.05%) showed culture
positivity in their respective midstream urine  specimens also. Urinary calculi can obstruct
the urine outflow pathway leading onto stasis of urine which in turn can lead
to attachment and multiplication of bacteria on to the epithelium leading to
infection. Studies have indicated that positivity in calculi culture and Mid
stream urine specimen can be  indicators
for urospesis indicating the importance of culturing both the specimens for
bacterial pathogens.(ref to be added). .(16). Studies have
found that Patients with positive urinary calculi  culture are more prone  for  postoperative sepsis. The
incidence of infection stones ranging from 2.7 % in Asian region to 42.9% in Subsharan
African region (9).Various studies have also reported high level of concordance
between the bacteria isolated from the stone and urine culture. (10,11,12). Studies
have indicated the association of various risk factors like age, sex, Diabetes,
Hypertension,previous history of renal stones and family history of renal
stones with positive stone culture(ref???) . In the present study significant
association between Stones with infection and Diabetes mellitus, Hypertension,
obesity , age and family history of renal stones were observed similar to a
study by Arias Vegaz R et al and A.triencheiri(13,14).  Among the gram negative isolates from
infected calculi good susceptibility was observed for Amikacin and
ofloxacin.Among the gram positive bacteria good susceptibility was observed for
amikacin and nitrofurantoin .we also observed the presence of drug resistant
bacteria like MRSA (11 isolates) and ESBL (25 isolates) among the urinary
stones with infection by phenotypic and genotypic methods.(Drug resistance
genes for ESBL like SHV and TEM identification  by Polymerase chain reaction )We
also observed the presence of drug resistant organism like ESBL, MRSA among
both the isolates obtained from the urine culture as well as from the calculi.
Such finding is alarming as the presence of such drug resistant organism can
lead on to treatment failure if not treated appropriately. Hence performing
culture of the urinary stone determining the antibiotic susceptibility pattern
along with the detection of drug resistance by phenotypic or genotypic methods
before initiating therapy will be of immense value for adequately treating the
infection. The information regarding the resistance pattern can help the
physicians in selecting an appropriate drug for therapy and the therapy can be
individualised taking into account the risk factors and chances of drug
resistance for better treatment outcomes and hospital infection control(17).Regularly
updated surveillance of local microbial prevalence and resistance patterns are
needed to guide the empiric therapy for UTIs.As
resistance is becoming more widespread, prudent use of antimicrobials is
imperative and, as asymptomatic bacteriuria is typically benign in the elderly,
antibiotics should not be prescribed without clinical signs of UTI. The use of
antibiotics as suppressive therapy or long-term prophylaxis may no longer be
defensible.Urinary tract infections (UTIs) are one of the
most common bacterial infection encountered in a health care setting(1).
Urolithiasis is also a commonly encountered condition among adults with a
prevalence of 3-5% and they may occur as an outcome of altered
metabolic conditions or concomitant urinary tract infection(2). Urolithiasis
can cause obstructive symptoms leading onto stasis of urine which in turn leads
on to adhesion and multiplication of bacteria to the uroepithelium leading onto
urinary tract infection. Urinary calculi that occur following urinary tract
infection are known as infection stone and those stones that are complicated as
a result of UTI are the metabolic stones . These metabolic stones trap bacteria
from co existent UTI (3,4). Urolithiasis associated with infection can result
in persistant bacterial infectionDue to extensive use of antibiotics the multidrug
resistant bacteria are being isolated from urinary tract infections and urinary
calculi cuture which are difficult to eradicate leading onto increased
mortality and morbidity and posing a serious threat. Identification of bacteria
in the calculi and therapy with appropriate antibiotic will also prevent
recurrence.(4)The present study aims to isolate the bacterial
agents from urinary calculi and from midstream urine specimen, to study the
antibiotic susceptibility pattern,to identify the drug resistant phenotypes
like MRSA and ESBL. The present study also aims at identifying the association
between various risk factors and positive stone culture.Urinary
calculi were thoroughly washed in sterile saline and crushed with aseptic
precautions. The crushed particles were inoculated into 5ml thioglycollate
broth and incubated at 37?c
for 18-24 hours. After incubation Subcultures were done onto Blood agar and
MacConkey agar. The growth of the bacterial isolates were identified as per
standard microbiological techniques.Phenotypic
Confirmatory testThe isolates that showed resistance for
ceftazidime and  cefotaxime were
confirmed to be ESBL producer by testing along with the combination of 10 mg
clavulanic acid and the isolates with a 5mm increase in zone of inhibition for
the combination ceftazidime / clavulanic acid (30µg/10µg) were confirmed as
ESBLs. MIC Reduction
test(Agar dilution method): The MIC of the isolates were tested for
various concentrations of 3rd generation cephalosporin  (cefotaxime 
and ceftazidime) from 0.5µg to 2048µg / ml of agar and the MIC
determined. Minimum inhibitory concentration (MIC) was the lowest concentration
at which no visible growth occurs.MIC reduction test was
performed by combining the third generation cephalosporin (cefotaxime and
ceftazidime) with 4ug/ml of clavulanic acid from 0.5ug to 2048ug / ml of agar
and the MIC was determined. More than or equal to three doubling dilution
reduction in the MIC of 3rd generation cephalosporins in the
presence of clavulanic acid indicates production of ESBL.