Isolate listing and antibiotic sensitivity pattern of blood and urine culture isolates in Colombo North Teaching Hospital from January-July, 2017

As part of laboratory surveillance system in the department of Microbiology, CNTH, all significant blood culture isolates and urine culture isolates are entered to the WHO net soft wear and analyzed. Clinical Laboratory Standard Institute (CLSI) method for blood culture isolates and for urine cultures stokes comparative methodwas used. This is the summery of the isolates and sensitivity which will help the clinicians to optimize the selection of empiric antibiotic treatment.

Summary of the blood culture isolates

3736 Blood culture specimens were received and 359 were positive. The following table includes the organisms isolated and number of patients as same organism become positive in multiple blood cultures when more than one bottle is sent simultaneously or when there is a persistent bacteraemia or candidaemia.

Coagulase Negative Staphylococcus,Bacillus spp (aerobic spore bearers),Aerococcus spp, Micrococcus spp and the presence of mixed bacterial species (174) are generally considered as skin contaminants, however can be significant in certain cases and antibiotic susceptibilities were reported in such cases. Therefore, probable contamination was a significant finding and attention to aseptic technique in blood culture collection is needed. High number of candidaemia was notable.

Organism Number of isolates Number of patients
Coliform spp 97 84
Acinetobacter spp 6 5
Pseudomonas spp 5 5
Stenotrophomonas spp 1 1
Burkholderia cepacia 1 1
Staphylococcus aureus 26 24
Streptococcus viridans 2 2
Streptococcus, Group B 8 8
Streptococcus,  Group A 4 3
Enterococcus spp 9 9
Streptococcus pneumoniae 2 2
Streptococcus bovis 1 1
Streptococcus spp 1 1
Candida spp 22 15
Staphylococcus, coagulase negative 111 107
Bacillus spp(aerobic spore bearers) 12 12
Aerococcus spp 1 1
Corynebacterium spp (diphtheroids) 4 4
Micrococcus spp 11 11
Mixed bacterial species 35 31

Below tables show the sensitivity pattern of the blood culture isolates.

 

 

Antibiotic sensitivity of Staphylococcus aureus

Antibiotic name Number %Resistant %Intemediate %Sensitive
Penicillin G 23 91.3 0 8.7
Cefoxitin 26 65.4 0 34.6
Gentamicin 23 21.7 0 78.3
Ciprofloxacin 19 36.8 5.3 57.9
Trimethoprim/Sulfamethoxazole 21 23.8 0 76.2
Clindamycin 26 23.1 0 76.9
Erythromycin 22 77.3 0 22.7
Vancomycin 26 0 0 100
Teicoplanin 21 0 4.8 95.2
Chloramphenicol 5 0 0 100
Fusidic acid 12 16.7 0 83.3

Methicillin resistance was detected using the cefoxitin disk and percentage ofMRSA was 65.4%.Penicillin resistance was very high which a common finding in Sri Lanka. Resistance to erythromycin was 77.3% but resistance to other antibiotics were significantly low compared to methicillin resistance which indicate possible high rates of community acquired methicillin strains which needs further evaluation.

Antibiotic sensitivityStreptococcus Pneumoniaeisolates

Antibiotic name Number %Resistant %Intermediate %Sensitive
Oxacillin 2 100 0 0
Cefotaxime 1 0 0 100
Levofloxacin 2 0 0 100
Trimethoprim/Sulfamethoxazole 2 100 0 0
Clindamycin 2 0 100 0
Vancomycin 2 0 0 100
Teicoplanin 2 0 0 100

Out of the two isolates one was meningeal and one was a respiratory isolates. MIC for penicillin was in the resistant range for both isolates which shows the importance of including vancomycin in empiric regimes when meningitis by streptococcus pneumoniae is suspected as per the national antibiotic guidelines.

Antibiotic sensitivity ofEnterococcus spp

Antibiotic Number %Resistant %Intermediate %Sensitive
Penicillin G 9 55.6 0 44.4
Ampicillin 8 62.5 0 37.5
Clindamycin 3 66.7 0 33.3
Erythromycin 5 80 0 20
Linezolid 1 100 0 0
Vancomycin 8 12.5 0 87.5
Teicoplanin 6 16.7 0 83.3

Among the enterococcus isolates (9), penicillin and ampicillin resistance was high and (55.6 % for penicillin)there was a vancomycin Resistant Enterococcus spp(VRE) which was resistant to teicoplanin as well which is needs particular attention.

 

 

Antibiotic sensitivity of Streptococcus group A & B streptococci

Antibiotic Number %Resistant %Intermediate %Sensitive
Penicillin 12 0 0 100
Clindamycin 11 18.2 9.1 72.7
Erythromycin 12 33.3 25 41.7
Vancomycin 10 0 0 100

Resistance to erythromycin and clindamycin was not very significant among our group A and group B streptococci, but number of isolates are also not very high to predict a pattern.

Antibiotic sensitivity ofColiform spp

Antibiotic name Number %Resistant %Intermediate %Sensitive
ESBL 31
Ampicillin 62 90.3 3.2 6.5
Amoxicillin/Clavulanic acid 83 79.5 4.8 15.7
Cefuroxime 63 74.6 9.5 15.9
Cefotaxime 80 80 0 20
Ceftazidime 21 57.1 0 42.9
Gentamicin 75 40 1.3 58.7
Ampicillin/Sulbactam 9 77.8 22.2 0
Ciprofloxacin 72 65.3 5.6 29.2
Levofloxacin 54 61.1 1.9 37
Ticarcillin/Clavulanic acid 76 81.6 6.6 11.8
Piperacillin/Tazobactam 55 43.6 9.1 47.3
Cefepime 20 80 5 15
Imipenem 55 20 1.8 78.2
Meropenem 89 29.2 1.1 69.7
Amikacin 57 29.8 3.5 66.7
Cefoperazone/Sulbactam 59 32.2 15.3 52.5
Netilmicin 75 32 4 64
Trimethoprim/Sulfamethoxazole 36 58.3 0 41.7
Colistin 61 1.6 0 98.4
Chloramphenicol 23 17.4 17.4 65.2

The resistance to 3rd generation cephalosporins were very high (80% for cefotaxime) and there were 31 ESBLs out of 97 coliforms isolated.Fluroquinolon resistance was significantly high but aminoglycoside resistance was relatively low. Carbapenam resistance was also 29.8% which is notable.

 

 

 

Antibiotic sensitivity of Acinetobacter spp

Antibiotic name Number %Resistant %Intermediate %Sensitive
Cefoperazone/Sulbactam 5 60 20 20
Ticarcillin/Clavulanic acid 4 100 0 0
Piperacillin/Tazobactam 4 100 0 0
Ceftazidime 3 100 0 0
Cefotaxime 1 100 0 0
Cefepime 2 100 0 0
Imipenem 5 100 0 0
Meropenem 3 100 0 0
Amikacin 2 100 0 0
Gentamicin 4 100 0 0
Netilmicin 2 100 0 0
Ciprofloxacin 5 100 0 0
Levofloxacin 5 80 20 0
Colistin 6 0 0 100

Acinetobacter spp which is usually a nosocomial pathogen has very high resistance rates to almost all antibiotics tested other than colistin.

Antibiotic sensitivity of Pseudomonas spp

Antibiotic name Number %Resistant %Intermediate %Sensitive
Cefoperazone/Sulbactam 3 33.3 0 66.7
Ticarcillin/Clavulanic acid 5 100 0 0
Piperacillin/Tazobactam 3 0 33.3 66.7
Ceftazidime 3 33.3 33.3 33.3
Cefepime 1 0 0 100
Imipenem 5 0 0 100
Meropenem 5 0 0 100
Amikacin 2 100 0 0
Gentamicin 4 75 0 25
Netilmicin 5 80 0 20
Ciprofloxacin 5 40 0 60
Levofloxacin 2 0 0 100
Colistin 2 50 0 50

Summary of the urine culture isolates

7699 urine specimens were received and significant colony counts were isolated from 991 specimens. Colony counts were considered as significant when the counts are more than 10or 104-105CFU/ml for specimens other than supra pubic specimens for which even a single colony is taken as significant.

Organism Number of isolates Number of patients
Coliform 845 801
Pseudomonas sp. 24 22
Enterococcus sp. 35 35
Acinetobacter sp. 20 20
Staphylococcus aureus 6 6
Probable Group B Streptococcus 19 19
Staphylococcus, coagulase negative 14 14
Candida sp. 28 26

 

Antibiotic sensitivity of Coliform spp (845 isolates)

Antibiotic name Number %Resistant %Intermediate %Sensitive
ESBL 251
Ampicillin 665 85.6 0.2 14.3
Ciprofloxacin 801 61.4 1.1 37.5
Norfloxacin 792 60.6 0.5 38.9
Nalidixic acid 782 71.9 0.4 27.7
Nitrofurantoin 740 35.5 0.7 63.8
Cephalexin 20 50 0 50
Cefuroxime 678 53.8 0.3 45.9
Cefotaxime 771 51.5 0.1 48.4
Ceftazidime 162 57.4 1.2 41.4
Trimethoprim/Sulfamethoxazole 76 67.1 0 32.9
Amoxicillin/Clavulanic acid 805 56.8 1.4 41.9
Gentamicin 813 31 0.2 68.8
Netilmicin 799 21.5 1.4 77.1
Cefoperazone/Sulbactam 91 24.2 7.7 68.1
Ampicillin/Sulbactam 4 100 0 0
Ticarcillin/Clavulanic acid 550 67.6 0.4 32
Piperacillin/Tazobactam 183 27.9 0.5 71.6
Imipenem 100 32 6 62
Meropenem 430 24.4 0.5 75.1
Amikacin 137 19.7 0 80.3
Levofloxacin 326 82.5 2.5 15
Colistin 200 3.5 0 96.5

Resistance was high among the coliforms to cephalosporin and fluroquinolons and there were 251 extended spectrum betalactamase producing (ESBL) coliforms. Very high fluroquinolon resistance was notable.

Antibiotic sensitivity of Acinetobacter spp(20 isolates)

Antibiotic name Number %Resistant %Intermediate %Sensitive
Cefoperazone/Sulbactam 9 33.3 55.6 11.1
Ticarcillin/Clavulanic acid 14 100 0 0
Piperacillin/Tazobactam 11 90.9 9.1 0
Ceftazidime 8 100 0 0
Cefotaxime 11 100 0 0
Imipenem 8 100 0 0
Meropenem 20 100 0 0
Amikacin 7 57.1 14.3 28.6
Gentamicin 20 100 0 0
Netilmicin 20 100 0 0
Ciprofloxacin 20 100 0 0
Levofloxacin 18 100 0 0
Norfloxacin 10 100 0 0
Colistin 20 0 0 100

High number of acinetobacter spp were isolated but according to the history they were contaminants or represented catheter colonizers.

Urine Pseudomonas spp(24 isolates)

Antibiotic name Number %Resistant %Intermediate %Sensitive
Ciprofloxacin 23 60.9 0 39.1
Norfloxacin 22 54.5 0 45.5
Gentamicin 24 62.5 0 37.5
Ticarcillin/Clavulanic acid 16 50 0 50
Piperacillin/Tazobactam 16 0 0 100
Meropenem 22 18.2 0 81.8
Amikacin 8 12.5 0 87.5
Netilmicin 23 39.1 0 60.9
Levofloxacin 12 50 0 50
Cefoperazone/Sulbactam 4 0 0 100

Urine Enterococcus spp (35 isolates)

Antibiotic name Number %Resistant %Intermediate %Sensitive
Penicillin G 1 100 0 0
Ampicillin 35 62.9 0 37.1
Norfloxacin 34 70.6 5.9 23.5
Nitrofurantoin 33 51.5 0 48.5
Vancomycin 30 0 0 100

Ampicillin resistance was high among the urinary enterococcus isolates.