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Incidence  of  Surgical  Site  Infections  and Microbial Pattern at Kilimanjaro Christian Medical Centre

Kitembo SK.K2,32,3MD(UDSM),ChuguluSG.G1,21,2MD,MD,MMed,FCS(ECSA).

1-Kilimanjaro Christian Medical Centre

2-Kilimanjaro Christian Medical College

3-Muhimbili National Hospital

Correspondence to: Dr. Kitembo S.K P.O Box 31159, Dar es Salaam, Tanzania.




Surgical site infection (SSI) remains a major cause of morbidity and death. We conducted a study to determine the incidence of surgical site infections and microbial pattern at Kilimanjaro Christian Medical Centre.


Patients and Methods

A prospective hospital based study was conducted at KCMC general surgical wards from November, 2010 to March, 2011. A total of 263 newly operated inpatients were enrolled but 27 patients among the group were lost on follow up visits and were therefore excluded from the study. So, only 236 patients completed the study’s one month follow up.


Two hundred and thirty six patients were followed up for the development of surgical site calinfectsiteionnfect.Eighteen.18 patients developed features of surgical site inffection.. Four patients had culture negative results.. One patientt who developed SSI due to an infected implant died.. Superficial SSIs constituted (61.1%) while deep SSI constituted (27.8%) and organ/space (11..1%).. The overall SSI rate was 7.6%. Clean,, clean contaminated,, contaminated and dirty wounds had infection rates of 3.5%, 8.7%, 25..4% and 29..4% respectively.. There were 15 bacterial isolates and multidrug resistance was also observed in a number of bacterial isolates.


The incidence of infection in our centre is low and the pattern of microbes causing surgical site infection at the centre has remained the same over time.


Surgical site infection (SSI) is an infection that develops within 30 days after an operation or within one year if an implant was placed, and the infection appears to be related to the surgery (14). It remains a major cause of morbidity and death among the operated patients(1). Post-operative SSIs are the most common healthcare-associated infection in surgical patients, occurring in up to 5 percent of surgical patients(2,14). In the United States, between 500,000 and 750,000 SSIs occur annually(3,16). Patients who develop a SSI require significantly more medical care. If an SSI occurs, a patient is 60 percent more likely to spend time in the ICU after surgery than is an uninfected surgical patient, and the development of a SSI increases the hospital length of stay by a median of two weeks (12,17). The risk of SSIs continues after discharge. SSIs develop in almost 2 percent of patients after discharge from the hospital and these patients are two to five times as likely to be readmitted to the hospital (12,16,17). The high morbidity associated with SSIs prolongs the hospital stay. This not only increases the medical care cost but also the mortality(10).


Clinical presentation of SSI varies from a spontaneous wound discharge within 7-10 days of an operation to a life-threatening postoperative complication. Most surgical site infections are caused by incision contamination by microorganisms from the patient’s own body during surgery. Infection caused by micro-organisms from an outside source following surgery is less common. Most of surgical site infections are preventable. Surgical site infections are the most common post operative complication, which can adversely affect the life of the patient. The morbidity associated with this not only increases the cost of care but also carries a significant mortality(6, 7). In the United States of America (USA) approximately one million patients develop SSI each year; increasing duration and cost of hospital stay (8).


The magnitude of SSI varies considerably in different parts of the world. The rate of surgical of site infection in USA has been reported to be 2.6 percent, while a report from Tanzania shows this figure to be 19.4 percent (5,7). Surveillance of SSI and providing feedback to the surgical team has been shown to reduce the incidence of surgical site infection and the cost incurred due to it (4). SSIs are classified as being either incisional or organ/space. Incisional SSIs are divided into those involving only skin and subcutaneous tissue (superficial incisional SSI), and those involving deeper soft tissues of the incision (deep incisional SSI)(11).


Patients and methods

Patient characteristics, wound properties and culture data were collected from patients’ files and culture reports. Diagnosis of SSI was made according to the National nosocomial infection surveillance (NNIS. Surgical wounds were classified according to the Centre for Disease Control (CDC) classification (11). Patients’ wounds were inspected from day one post operative until the day of discharge from the hospital and later were followed up for four weeks at the outpatient clinic. Some surgeons open surgical wounds from day three post operative. However, in this study, it was made the standard to open surgical wound from day one post operatively in order to identifye tify thosese with early signs of SSIs.. They were told not to change the wound dressings in tthe peripheral health facilities until they were seen at tthe surgical clinic. Those patients who did not show for the follow up visits were excluded from the study. The data of up visits were excluded from the study. The data of each each patient were filled into a data sheet. For patients patient were filled into a data sheet. For patients who who showed signs of SSIs, wound swabs were done, showed signs of SSIs, wound swabs were taken, put in put in Stuart’s transport medium and sent to the Stuart’s transport medium and sent to the laboratory laboratory for culture and antibiotic sensitivity. The for culture and antibiotic sensitivity. The duration of duration of culture was three days. Microscopy was culture was three days. Microscopy was conducted done for positive cultures. The hospital laboratory had for positive cultures. The hospital laboratory had no no techniques for culturing anaerobic and fastidious techniquesorganisms. Datafor culturinganalysis wasanaerobicconductedandusingfastidiousSPSS organismsver16.0.Statistic.Dataanalysissignificancewasconductedwastestedusing SPSSChi-versquare16.test0.StatisticalandtheP- significancevaluewassetwasat<0tested.05. using

Chisquare test and the P- value was set at <0.05.


ResultsAtotalof263 patients were enrolled in the study but 27 patients who are equivalent to 10.3% of the total Apatientstotalof enrolled263patientswerewerelost enrolledonfollowin upthevisitsstudyandbut 27werepatientsremovedwhofromare theequivalentstudy.Ofto the10.3%remainingofthe total236


patients, enrolled134(56.8%)werewerelost malesonfollowand up102visits(43.2%)and were females. 153 patients were elective patients were removed from the study. Of the remaining 236 whereas 83 were emergencies.

patients, 134(56.8%) were males and 102 (43.2%) The majority of the operations performed were were females. 153 patients were elective patients laparotomy (96 cases), thyroidectomy (35 cases), whereas 83 were emergencies.

head surgery (28 cases) and others constituted the The majority of the operations performed were minority. (Table 1)


laparotomy (96 cases), thyroidectomy (35 cases) and head surgery (28 cases)(Table 1).

Click to view table 1


Of the enrolled patients the majority had(60.2%)clean had wounds clean wounds while only a minority had dirty wounds(Table2)

Click to view table 2


Out of 236 patients, 18 patients developed signs of SSIs, giving an incidence of 7.6%. Wound swabs for culture and sensitivity were taken. 4 patients out of 18 patients had negative cultures, the remainders were culture positive. The majority of SSI were superficial SSIs (61.1%) followed by deep (27.8%) and organ/space (11.1%) SSIs. The rate of infection in elective surgeries was 5.9% and in emergency surgeries was 10.8 % (Table 3).



The majority of the patients who showed signs of SSIs were under the age of 13 years.

Click to view table 3


The majority of infections were seen in laparotomy procedures (Table 4).


Click to view table 4


The overall SSI rate was 7.6%. The infection rates for different classes of wounds were clean wound, 3.5%, clean contaminated wounds, 8.7%, contaminated wounds, 25.4% and dirty wounds, 29.4%. The difference observed in the infection rates in different classes of wounds was statistically significant, pvalue of 0.000 on Chi square test (Table 5).


Click to view table 5


One patient who developed SSIs showed a mixed infection of Staphylococcus aureus and Klebsiella spp. Gentamicin was found to be very potent against Klebsiella spp, E. coli, Proteus spp, Coliforms and pseudomonas spp. Ceftriaxone and metronidazole were the commonest used prophylactic drugs following abdominal surgeries, and chloramphenical and benzyl penicillin were used as prophylaxis following head surgeries. A number of bacterial isolates responded favourably to all the tested antibiotics. 28.6% of staphylococcus aureus isolates (2 isolates) were sensitive to all the tested drugs. Multidrug resistance was also observed in a number of bacterial isolates. Proteus spp exhibited resistance to metronidazole and ampiclox. Of the three Klebsiella spp isolates, two showed resistance to both cloxacillin and cotrimoxazole, and one showed resistance to cloxacillin, erythromycin and tetracycline. Pseudomonas spp was resistant to metronidazole. There was no growth of staphylococcal aureus which was found to be methicillin resistant.




The overall SSI rate observed in this study is still higher compared to those seen in the developed countries, in Italy, an overall SSI rate 5.9% and in USA, 2.6%(1, 7). The high standards of health care in the developed countries still remain as the only explanation to this difference in the rates of infection observed. The overall infection rate in this study was 7.6% and in the different classes of wounds;-clean wounds, clean contaminated wound, contaminated and dirty wounds were 3.5%, 8.7%, 25.4% and 29.4% respectively. In a similar study by Ericksen et al, 2003 at KCMC, the overall infection rate was 19.4% and the rates of infection by wound classes were;-clean wounds, 15.6%, clean contaminated wounds, 17.7%, contaminated wounds, 37% and dirty wounds 50%. The difference observed may be due to increased standards of health care (asepsis in surgery, the use of antibiotic prophylaxis, surgical technique, appropriate wound care, etc) provided by surgical team at our centre. The differences in rates of SSIs observed in different classes of wounds in this study are statistically significant with a P-value of <0.05. The rate of infection in elective surgeries was 5.9% and in emergency surgeries was 10.8 %. Poor health conditions and poor preparation of the patients might have contributed to the higher rate of surgical site infection in emergency cases. The infection rate in clean cases in this study is lower than that observed at Muhimbili National Hospital(18). This suggests that the standard of care for surgical wounds at our centre may be higher than that at Muhimbili National Hospital in 2000. This comparison to Muhimbili National hospital was done because it is a national centre in the same country as our centre. Among the cases which showed signs of SSI, the majority of the cases were those which underwent laparotomy, 13 cases (72.2%) and this is different from an observation made by Lilani et al, 2005, where cases which underwent thoracotomies were leading in infection (44.4%). Most of the wounds after laparotomy are clean contaminated to dirty wounds and carry a high risk of infection. Negative cultures are not uncommon as it has been observed in this study and in other studies (4,13). Fastidiousness of the microbes (atypical microorganisms like mycoplasma, Norcadia, legionella,’small colony variant’ Staphylococcus aureus, atypical mycobacteria, etc.), poor microbial yields in the fluids at surgical sites and culture techniques could attribute to this. One patient who developed surgical site infection died. She had an infected VP shunt. This is an important example of the mortality associated with infected implants. Implants are associated with an increased risk of surgical site infection if antibiotic prophylaxis is not used and asepsis in surgery not absolute. Staphylococcus aureus has remained to be the commonest bacterial isolate in this study and in the majority of SSIs in other studies, as it is found in abundance on the skin unlike other microbes(4,13,15). The finding on drug resistance in our study has also been shown in other studies (4). 28.6% ( 2/7) of staphylococcus aureus isolates were sensitive to all the tested drugs; conversely, 54.5% of staphylococcus aureus isolates were sensitive to all the tested drugs (4).The decrease in staphylococcus aureus sensitivity to drugs may suggest evolution of resistant strains. The multidrug resistance observed may also suggest an increase in inappropriate prescription and use of antibiotics. In conclusion, it has been observed that there is an improvement in the quality of care of patients evidenced by the lower infection rates when compared to those observed at the same centre in an earlier study (4). However, the pattern of microbes causing SSIs has not changed much over time.



  1. Tissue specimens in addition to swabs from surgical sites should be advised to reduce the rate of negative culture.

  2. Culture duration should be extended from the normal 72 hours to five days to try and accom-modate for the growth of many atypical micro-organism (atypical mycobacteria, ureaplasma, Norcadia, ‘small colony variant’ staphylococcus aureus, etc.

  3. For bacteria strains which show resistance to the standard antibiotics, further studies (microbiology) should be done to find appropriate drugs for their eradication.

  4. There is a need for improvement of the hospital laboratory so that it is able to culture fastidious and anaerobic organisms.



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  9. Haley RW, Schaberg DR, Crossley KB, et al. Extra charges and prolongation of stay attributable to nosocomial infections: a prospective interhospital comparison. Am J Med 1981; 70:51-8

  10. Henry Rhee, MD and Bonnie Harris, CIC. Reducing Surgical Site Infections. January 3, 2008.

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  14. Mangram AJ, Horan TC, Pearson ML, et al, the Hospital Infection Control Practices Advisory Committee. Guideline for the prevention of surgical site infection, 1999. Infect Control Hosp Epidemiol. 1999; 20:247-280.

  15. Onche et al. Microbiology of post-operative wound infection in implant surgery. Nigerian Journal of Surgical Research, 2004; 6(1 – 2): 37 – 40.

  16. Perencevich EN, Sands KE, Cosgrove SE, et al. Health and economic impact of surgical site infections diagnosed after hospital discharge. Emerg Infect Dis. February 2003;9(2):196-203.

  17. Whitehouse JD, Friedman D, Kirkland KB, et al. The impact of surgical site infections following orthopedic surgery at a community hospital and a university hospital: adverse quality of life, excess length of stay, and extra cost. Infect Control Hosp Epidemiol. 2002; 23(4): 183-189.

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