urinary tract infection

Spectrum and Resistance pattern of bacteria causing Urinary Tract Infection

byPinky Varshney

MSc. Fourth semesterLucknow University.

Introduction A Urinary Tract Infection (UTI) is an infection that

affects part of urinary tract (kidney, ureters, bladder,

urethra)

It is most common among females than males.

MANIFESTATIONS Cystitis• when infection affects the lower urinary tract.• Symptoms are dysuria , blood in urine, discomfortin lower abdomen, pain in urination.

Pyelonephritis• When infection affects the upper urinary tract.• Symptoms are fever, back pain, nausea or vomiting.

Asymptomatic bacturiuria• Presence of bacteria in urine in absence of symptoms.

Causes of Urinary tract infection

Microorganisms mainly Escherichia coli are main cause of

infection.

The Urinary catheters also increase the risk of UTI

The patients suffering from diabetes, neurological and structural abnormalities are prone to the infection.

In females, sexual activity and pregnancy are the main cause of infection

Use of diaphragms is also associated with infection.

Etiological Factors

The infection is mainly caused by bacteria and are rarely caused by fungi and viruses.

90% of UTI are caused by commonly occurring intestinal bacteria Escherichia coli.

Others includeGram negative bacteria:- Klebseilla, Pseudomonas,

Enterobacter spp., Proteus spp. ,Citrobacter , Acinetobacter

Gram positive bacteria:- Staphylococcus sps., Enterococcous sps.

Objective Identification of different bacteria present in urine

samplesTo determine their resistance pattern by Kirby Baurer

method of disc diffusion

Materials and MethodsThe uncomplicated cases of Urinary Tract

Infection could be treated empirically but in complicated cases the urine cultures are recommended which includes the following steps:-

Sample collection Sample processingIdentification of culturesAntibiotic susceptibility testing

Sample Collection

Clean catched midstream urine was collected in a 20 ml screw

capped container.

Specimen was labelled and analyzed within 6 hours.

Sample Processing

Platinum wire calibrated loop was used to deliver 0.01 ml of urine.

The samples were plated on CLED (Cystine Lactose Electrolyte Deficient) agar

and Hi Chrome plates.

The inoculated plates were incubated at 37˚C for 18 - 24 hours.

Identification

The number of isolated bacterial colonies were multiplied by 100 for

estimation of bacterial load/ml of urine sample. Colony counts of 103

were considered to be significant.

Identification was done on the basis of Cultural characteristics.

The Biochemical tests and oxidase tests are used for identification of

gram negative bacteria

Catalase test and coagulase test are used for identification of gram

positive bacteria.

Arabinose and DNase plates are also used for identification.

On the basis of cultural characteristics on CLED and Hi chrome plates

E.coli Staphylococcous

Pink colonies on CLED Agar.

Purple colonies on hi chrome

White colonies on hi chrome

Pin point colonies On CLED plate

Small Green colonies on hi chrome

Enterococccous Psuedomonas

Non PinkColoniesOn CLED plate

Green ColoniesOn Hi Chrome

For identification of Gram negative bacteria

Triple sugar iron test

Citrate test

Urease test

Sulphur indole motility

Methyl red test

Oxidase test

For identification of gram positive bacteria

Coagulase testCatalase test

Arabinose plate for Enterococcous species

DNase plate for identification of Staphylococcous species

EnterococcousFaecium

Enterococcous faecallis Clear zone

indicates S.aureus

CoNs

The test was performed so as to recommend the suitable drug to the patients to cure infection which is possible only if the

resistance and sensitivity pattern of identified isolate towards drugs is known.

Kirby Bauer’s Disc diffusion method is the most suitable method.

Muller Hinton Agar was the medium used.

Inoculums in saline solution (0.85%) were prepared by picking

the colonies and turbidity was adjusted to 0.5 Mc Farland

Agar surface was inoculated by using a cotton swab dipped in suspension.

Leave for 5 – 10 minutes for drying

then the antibiotic disks were placed on surface of MHA

Antibiotic Susceptibility test

Gram NegativeBeta lactam inhibitor combinations

Aminoglycosides

Carbepenems

Floroquinolones

Tetracyclines

Cephalosporins

others

Enterobacteriaceae

Ampicillin sulbactam,Piperacillin tazobactam

Gentamycin,Amikacin,Nitilmycin,Tobramycin

Meropenem,Ertapenem,Doripenem,Imipenem

CiprofloxacinLevofloxacin,Norfloxacin

Tetracycline,Doxycycline

Cefepime,Ceftazidime,Cefotaxime,Cefoxitin

Aztreonam,Nitrofurantoin

Acinetobacter Ampicillin sulbactam,Piperacillin tazobactam,Cefoperazone sulbactam

Gentamycin,Amikacin,Tobramycin

Meropenem,Doripenem,Imipenem

Levofloxacin,Ciprofloxacin


Cefepime,Ceftazidime,Cefpirome

Pseudomonas Piperacillin tazobactam

Gentamycin,Tobramycin,AmikacinNitilmicin

Meropenem,Doripenem,Imipenem

CiprofloxacinLevofloxacin,Norfloxacin,Ofloxacin

Ceftazidime,Cefepime

Aztreonam

Gram Positive

Beta lactamase inhibitor combinations

Aminoglycosides

Floroquinones Tetracyclines others

Staphylococcous Cefoperazone sulbactam

Nitilmycin,Amikacin

Ciprofloxacin,Levofloxacin,Ofloxacin


Chloramphenicol,Linezolid,TeicoplaninVancomycinClindamycinErythromycin

Enterococcous High level Gentamycin

CiprofloxacinNorfloxacinLevofloxacin


PenicillinVancomycinTeicoplaninNitrofurantoinFosfomycinLinezolid

When the antibiotic disk were placed on agar surface

•Invert and incubate for 16-18 hours at 37˚C

•After incubation the inhibition zone diameters were measured

with scale and the results were interpreted by

recommendation of CLSI.(Clinical and Laboratory Standards

Institute)

Gram negatives producing Beta lacamases. Cases of Extended Spectrum Beta Lactamases (ESBL’s) were most common among

Klebseilla pnuemoniae, E.coli and Proteus mirabilis.

For detection of ESBL in K.pnuemoniae and E.coli any of these disks can be used (in micro grams)

Cefpodoxime(10) < 17mm Ceftazidime(30) < 22mm Aztreonam(30) < 27mm Cefototaxime(30) < 27mm Ceftriaxone(30) < 25mmThese zone diameters indicate ESBL producers.

For P.mirabilis drug tested were Ceftazidime (30) < 22mm Ceftazidime clavulanate (30/10) Cefotaxime (30) < 27mm Cefotaxime clavulanate(30/10) A 5mm increase in zone diameter for either antimicrobial agent when in combination versus the

zone diameter when tested alone indicates ESBL.

For Ampicillin β lactamases (AmpC) detection Cefoxitin disk were used. A zone diameter of < 18mm was considered to be positive.

For Methicillin Resistant Staphylococcous aureus(MRSA) and Coagulase Negative Staphylococcous(CoNs) detection cefoxitin disks were used. A zone of inhibition of <22mm were detected as MRSA and zone of inhibition of < 24mm were detected as CoNs.

For High Level Aminoglycoside Resistance (HLAR) Gentamycin and Streptomycin disks were used.

Results

Samples were collected from OPD (outside patient department), IPD

(in - patient department) and ICU (intensive care unit).

Total

500 urine samples

Positive

200 urine samples (40%)

Site wise distribution of isolates

Gender wise distribution of isolates

Commonest organism involved

Most common gram negative isolate

85%

10% 4%

n=133

E.coliPsuedomonasEnterobacter

Most Common gram positive isolate

79%

13% 7%

Commonest Gram positive isolate n=67

EnterococcousCoNsS.aureus

Percentage antimicrobial sensitivity of gram negative isolates

Name of

organism

ward No. of

isolates

NX NF FO* CTX G TET PIT ETP

E.coli OPD 69 21.7 69.5 75.3 1.24 47.8 28.9 66.6 69.5

IPD 30 13.3 66.6 83.3 10 40 30 43.3 53.3

ICU 7 14.2 57.1 85.7 14.2 14.2 14.2 28.5 28.5

Enterobacter OPD 4 50 50 Not

tested

25 0 25 25 Not

teste

d

IPD 1 0 0 Not

tested

0 100 100 0 Not

teste

d

Percentage antimicrobial sensitivity among gram positive isolates.

Name of

organism

ward No. of

isolates.

NX NF FO* G/HLG TET TEI LZ VA

Enterococco

us

OPD 34 11.7 82.3 94.1 47 29.4 85.2 91.1 82.3

IPD 14 14.2 64.2 92.8 21.4 42.8 64.2 92.8 50

ICU 5 20 60 60 60 40 100 100 60

CoNs OPD 8 12.5 100 Not tested 62.5 50 100 87.5 100

IPD 1 Not

tested

100 Not tested Not tested 100 100 100 100

ICU Not tested

Drug resistance in Gram negative isolates.

Drug resistance in Gram positive isolates.

Conclusion UTI is the most commonly caused infection with a high rate of

morbidity and financial loss.

The outside patients are more prone to infection.

The gram negative isolates are more common cause of infection than the gram positive isolates.

Escherichia coli is found to most common cause of infection.

There is need to formulate strategies to detect and prevent emergence of resistance for an effective treatment of infections which are caused by them.

urinary tract infection

Healthcare