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A wound results following disruption of the skin which can be intentional or accidental (1). Wound infections cause a burden of disease and morbidity for both the patient and the health services. To the patient it causes pain, discomfort, inconvenience, disability, financial drain, and even death due to complications such as septicemia. It causes financial strain on the health services due to the required high cost of hospitalization and management of the patients.

A number of factors contribute to wound infection; however microorganisms are the major cause with bacteria being the most prevalent (2). Early recognition of wound infection and appropriate management is important. Antibiotic therapy and surgical management are the cornerstone measures whereby antibiotics offer adjuvant treatment. Wound infection can be caused by single bacteria or multiple microorganisms. Surgical site infections are the second most common cause of nosocomial infections after urinary tract infections (3, 4). Most surgical site infections occur in ambulatory patients after discharge from the hospital and therefore beyond the hospital infection control surveillance programs (3). Prolonged pre- operative hospital stay and exposure to diagnostic procedures has been associated with increased rate of SSI. In clean surgical procedures, Staphylococcus aureus is the most common pathogen while Pseudomonas aeruginosa is the most common gram negative bacilli. A number of studies indicate an increase in antibiotic resistant microorganisms in surgical patients. Resistant bacteria causes severe infections that are expensive to diagnose and difficult to treat. The mechanism by which resistance develops is complex and can result in multi-drug resistant bacterial strains due to simultaneous development of resistance to several antibiotics. Determination of local bacterial sensitivity patterns to antibiotics is important in providing a guide for antibiotic selection.

There are factors that increase the risk of wound infection which include patient characteristics such as; age, obesity, malnutrition, endocrine and metabolic disorders, smoking, hypoxia, anaemia, malignancies and immunosuppressants (5). Other factors are the state of the wound which includes nonviable tissue in the wound, foreign bodies, tissue ischaemia, and formation of haematomas, long surgical procedures, and contamination during operation, poor surgical techniques, hypothermia and prolonged pre-operative stay at the hospital.

Wound infections can be prevented by restoring blood circulation as soon as possible, relieving pain, maintaining normal body temperature, avoiding tourniquets, performing surgical toilet and debridement of the wound as soon as possible, administration of antibiotic prophylaxis for deep wound and high risk infections (5). High risk wounds include contaminated wounds, penetrating wounds, abdominal trauma, compound fractures, wounds with devitalized tissue; high risk anatomical sites such as hands and feet. Antibiotic prophylaxis should be started two hours before the surgical procedures.

Establishment of the causative microorganism is important and treatment should be initiated based on the bacterial sensitivity patterns. Topical silver dressings have been used to treat infected wounds however; there is no evidence for their efficacy due to multiple microbial aetiologies (6). To achieve optimum antimicrobial therapy, the biofilm load should be reduced to enhance drug concentration at the wound site (7).

Bacterial wound infections are a common finding in open injuries. Severe and poorly managed infections can lead to gas gangrene and tetanus which may cause long-term disabilities (5, 7). Chronic infection can cause septicemia or bone infection which can lead to death. Sepsis associated encephalopathy increases morbidity and mortality especially in the ICU patients (8).

Problem Statement

Septic wounds are a common cause of morbidity. Despite improvement in the practice of medicine and attempts to provide aseptic conditions in the surgical wards, the incidences of wound infection are increasing. Management of wound infection remains a challenge in the surgical areas with the increasing resistance to antimicrobials (9). Antimicrobial resistance can lead to complications which depending on severity can cause disability or death and increased cost of hospitalization and management. In children, this impacts negatively on the quality of life at a tender age. The antibiotic sensitivity patterns have not been studied fully especially in the surgical pediatric patients at Kenyatta National Hospital. Inappropriate antimicrobial use is associated with increased resistance (10). It was therefore important to identify the causative organisms and determine the antimicrobial sensitivity patterns to help reduce infections and ensure appropriate use of antimicrobials.

Purpose of the study

Wound infection is a common problem in children, proper management with appropriate antibiotics is therefore important to reduce morbidity that may arise. This study aimed to determine the aetiology and antimicrobial sensitivity patterns of bacteria that cause wound infections in the surgical paediatric patients at KNH. Antibiotic misuse and overuse can lead to resistance which necessitated the need for the study.


1.4.1 Main objective

The main objective of this study was to identify the bacteria that cause wound sepsis and their sensitivity patterns in the paediatric surgical wards at the Kenyatta National Hospital.

2 Specific objectives

The specific objectives were:

  1. To determine the prevalence of wound infection in the paediatric surgical wards.
  • To identify the bacteria that cause wound infection.
  • To determine the antimicrobial sensitivity patterns of the isolated bacteria
  • To find out the antibiotics used in management of wounds in the paediatric surgical wards

Research Questions

The research sought to answer the following questions:

  1. What is the prevalence of wound infection in surgical paediatric patients?
  • What bacteria causes wound sepsis in the paediatric surgical wards?
  • What are the antibiotic sensitivity patterns of the isolated bacteria?
  • Which antibiotics are used in management of septic wounds in the paediatric surgical wards?


The findings of the study was to help in choosing appropriate antibiotics by considering the sensitivity patterns that were observed, hence appropriate management of the infected wounds. This would result in a cost effective therapy for the patient and reduced financial burden of hospitalization.


Wound infections are caused by a number of microorganisms which include bacteria, fungi and viruses. This study was only able to address sepsis caused by aerobic bacteria. The study

was not able to address the factors that contribute to resistance patterns that were observed. It was also not able to identify the specific types of BHS and NLF due to in availability of the specific reagents for identification.



This chapter analyses relevant studies that had been carried out in different parts of the world with reference to bacteria that cause wound sepsis, the sensitivity patterns and the antibiotics that are used in surgery.

Prevalence of wound infection

Worldwide, there is increasing prevalence of MRSA wound infections that affect the entire community; it is estimated at 60.1% while MSSA is at 30.2% (11, 12). A study done at a teaching hospital in Sudan found the prevalence of aerobic hospital acquired wound infection post surgery to be 25.23% (13). Other studies have found that before the introduction of routine use of antibiotic prophylaxis clean wound infection rates were 1-2%, for clean contaminated wounds 6-9%, contaminated wounds rates were 13-20% while for dirty wounds rates were 40% (14, 15, 16). With the introduction of antibiotic prophylaxis, the infection rates have greatly reduced. In Algeria, a study reported a decrease in HAI prevalence following introduction of antibiotic prophylaxis from 9.0% in 2001 to 4.0% in 2005 (17). In Nigeria, a cumulative incidence of 23.6 per 100 operations was reported (18). The incidences by wound classification ranged from 6.5% to 20.2% in clean wounds, 10.1% to 23.8% in clean-contaminated wounds, 13.3% to 51.9% in contaminated wounds and 44.1% to 83.3% in dirty wounds. In Tanzania, 19.4% of patients developed SSI post surgery (19). In Uganda the prevalence of SSI was found to be 10%, 9.4% of whom being in women who underwent caeserian section (20). In Ethiopia, the prevalence of SSI 21% based on clinical criteria and 38.7% based on bacteriological criteria in patients who had undergone abdominal surgery (21). A study done in Kenya found the prevalence of wound infection among women who had undergone caeserian section to be 19% (22).

No study has been done in the surgical paediatric patients, therefore, there is need to determine the rate of wound infection among the surgical paediatric patients at the Kenyatta National Hospital.

Type of bacteria that cause wound infections

It has been found that wound infections are caused mostly by Staphylococcus aureus, Methicillin resistant Staphylococcus aureus, Streptococcus pyogenes, Enterococci, Pseudomonas aeruginosa, Escherichia coli and Streptococcus epidermidis (23). Other studies have shown that the prevalence of Methicillin resistant Staphylococcus aureus which were initially  hospital  acquired  is  steadily  increasing  in  the  community  (24).The  common

bacteriological findings in chronic wounds are found on the skin as normal flora, in faeces, water and in the environment (7). Evidence suggests that chronic wounds result due to a combination of structural damage and establishment of a chronic biofilm infection which stimulates host immune response that cause further damage generating a vicious cycle. Aerobic bacteria are commonly encountered in surgical wound infections the prevalence was higher                          for:                  Staphylococcus          aureus,               Pseudomonas                 aeruginosa,                        Escherichia     coli, Streptococcus epidermidis and Enterococcus faecalis. Most of the Staphylococcus aureus are MRSA (23).

A study carried out in Algeria found the bacteria causing wound infection were: Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia and Enterobacter in decreasing frequency. Another study in Senegal reported Enterobacter cloacae, Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa (25). A report on HAI cumulative incidence in surgical patients showed the following distribution in decreasing frequency: Klebsiella pneumoniae, Escherichia. Coli, Pseudomonas aeruginosa, and Staphylococcus aureus (26). A study in Kenya gave a cumulative incidence of 19% SSI post Caeserian section delivery (22).A study carried out in Tanzania and Ethiopia found Staphylococcus aureus and Escherichia coli to be the major cause of SSI with others being, Klebsiella spp, Enterococcus spp, Pseudomonas spp and Enterobateriaciae (19, 21, 27).

In the Central Republic of Africa, a survey in the surgical orthopedic patients showed that the common organisms were Staphylococcus aureus and Proteus mirabilis (28). In Nigeria the prevalence of the bacteria that cause SSI in paediatric patients was found to be higher for Escherichia coli followed by Klebsiella spp, Pseudomonas spp, Staphylococcus spp, and proteus spp (18). A study done in Kenya at the Kenyatta National Hospital, orthopedic wards showed the prevalent bacteria in SSI are: Staphylococcus aureus, Enterobateriaceae, Streptococcus faecalis, Streptococcus pyogenes, and Pseudomonas spp (29). The pathology resulting from Staphylococcus aureus and Pseudomonas aeruginosa polymicrobial wound infections is of great importance due to their ubiquitous nature, increasing prevalence, growing resistance to antimicrobial agents, and ability to delay healing (46).

No study has been done in the paediatric surgical patients at the Kenyatta National Hospital, to identify the bacteria that cause both SSIs and chronic wound infections.

Antimicrobial susceptibility of bacteria causing wound infection

Most Pseudomonas aeruginosa isolates are sensitive to piperacillin, ceftazidime, and imipenem, a gradual emergence of resistance to β-lactams. A few isolates are resistant to

netilmicin, and there is decreased ciprofloxacin activity (23). Staphylococcus aureus is the most prevalent in surgical wound infections. MRSA forms 54.4% of Staphylococcus aureus isolates (23). Amoxicillin-clavulanate, cefazolin, and imipenem have shown in vitro activity against more than 60% of the MRSA isolates, and are considered resistant to all β-lactams, cephalosporins, β-lactam–β-lactamase inhibitor combinations, and carbapenems.

Enterococci, causes frequent surgical wound infections and almost all of the Enterococcus faecalis isolates are susceptible in vitro to glycopeptides and gentamicin. However, some are resistant to cefazolin and good in vitro sensitivity was shown by amoxicillin-clavulanate and imipenem.

Gram-positive anaerobes are sensitive to most drugs while gram-negative anaerobes are resistant to ampicillin and cefazolin. Streptococcus pyogenes was found to be resistant to macrolides (30). No resistance to macrolides was reported in Indonesia, Australia, Belgium, the Netherlands and United Kingdom. Streptococcus pyogenes showed resistance to all beta lactams except cefaclor.

In chronic wound infections, once a biofilm has been established, causes the bacteria to resist antibiotics and other antimicrobials like silver sulphadiazine even the host defence (7). The biofilm promotes higher mutation rates hence resistance to antibiotics. A study carried out at Kenyatta National Hospital showed Gentamicin was active against Escherichia coli, Pseudomonas, Klebsiella spp, Enterococci, Alcaligenes spp, Citrobacter freundi, Serratia spp and acinetobacter baumanii (29). Amoxicillin- clavulanic had significant activity against Enterobacteriaceae, Streptococcus pyogenes, Streptococcus faecalis except Klebsiella which showed activity of 44%. Piperacillin, ticarcillin and tarzobactam showed good activity against Pseudomonas spp, and Enterobacteriaceae; however Proteus spp, Escherichia coli and Klebsiella spp showed resistance. Ceftazidime had 80% activity against most organisms. Cefuroxime had moderate activity against Escherichia coli, Staphylococcus aureus, Enterobacter spp, Proteus spp and Klebsiella spp, while Streptococcus pyogenes and Citrobacter spp showed high sensitivity. Ceftriaxone showed activity against Enterobacteriacea but resistance was seen with Pseudomonas spp. Ciprofloxacin had good activity against Enterobacteriacea, moderate activity against Staphylococcus aureus and inactive against Streptococcus faecalis. A study done in Uganda, the prevalence of Staphylococcus aureus was 59.4% in the inpatient with an average antibiotic susceptibility of ampicillin and higher, chloramphenicol but low for ciprofloxacin and erythromycin (47). In a study carried out in Northeast Ethiopia, Escherichia coli showed high resistance to erythromycin and amoxicillin but high sensitivity to nitrofurantoin, norfloxacin, gentamicin,

and ciprofloxacin (49). In Khartoum, resistance was high for amoxicillin, cefuroxime, ceftriaxone, ciprofloxacin, amoxicillin clavulanate and ceftazidime (50). In a study on in vitro selection of resistance in Escherichia coli, frequencies for mutations for levofloxacin and ciprofloxacin were less than 10-11 at peak concentrations (51).

In a study on natural antibiotic susceptibility, Klebsiella spp were found to be sensitive to penicillins, cephalosporins, quinolone, trimethoprim and cotrimoxazole (52). An evaluation of antimicrobial susceptibility of Klebsiella spp found a sensitivity of 50-100% for ciprofloxacin (53). The infections can therefore be treated with ceftazidime, cefepime, ampicillin/sulbactam, levofloxacin and meropenem (54). A study on the trends in the susceptibility of Proteus mirabilis showed there is a steady increase to ciprofloxacin resistance (55). Proteus mirabilis causes different infections and imipenem has shown the highest activity followed by amikacin and cefoxitin (56, 57).

In a study on antimicrobial sensitivity of Pseudomonas aeruginosa, high resistance was observed with piperacillin, ticarcillin, ceftazime, imipenem, amikacin and cotrimoxazole 66.6%. Cefotaxime showed a susceptibility of 83.3% and an intermediate resistance was seen with ciprofloxacin (58). In another study, isolated pathogens were resistant to amikacin, ciprofloxacin and ceftriaxone (59).

CoNS are of low virulence but are increasingly recognized as clinically significant (62). The risk factors include foreign bodies such as indwelling devices and immunosuppressants. Resistance to semisynthetic penicillins has been observed in more than 80% of the cases. It is resistant to multiple antimicrobial agents used to treat Staphylococcus aureus. High resistance rate has been observed with penicillin G, erythromycin and oxacillin (63). Clindamycin, cotrimoxazole and ciprofloxacin have shown medium resistance whereas rifampicin, ceftizoxime and gentamicin have shown low resistance. Ampicillin is the drug of choice for monotherapy treatment of susceptible Enterococcus faecalis, combination therapy with a cell wall active agent provides more synergy (64). In a study, the isolated strains of Enterococcus were absolutely sensitive to vancomycin, teicoplanin and nitrofurantoin. Penicillins showed 96% sensitivity, ciprofloxacin 43% and tetracycline 28% (65).

Management of septic wounds with antibiotics

It has been noted that inappropriate use of antibiotics can lead to development of resistance to antibiotics (10). Inappropriate use includes; no indication, incorrect choice, incorrect application of drugs and divergence from institutional guidelines. Antibiotic prophylaxis has been shown to significantly reduce rate of wound infection (31, 32). A ground was laid for

antibiotic prophylaxis as early as 1960s (33, 34). However, a study done in the United Kingdom showed there was no benefit in using flucloxacillin prophylaxis in patients with open fracture (35). A systematic review done in New Jersey, found that short course of first generation prophylaxis administered as soon as possible after the injury provided adequate prevention against wound infections (36). A national advisory for prophylaxis recommends use of cefazolin, cefuroxime or vancomycin for knee, hip, cardiothoracic or vascular surgery prophylaxis while for the colon, aminoglycosides, macrolides or metronidazole should be considered (37).

Even though antibiotic use in clean wounds is not clearly indicated, infection rates of 40% post surgery have been reported (16). Selection of antibiotics should be based on the infecting organism, tissue penetration ability, low toxicity and absence of allergies. In a study carried out in Ireland, the antibiotics that are mostly used are combinations of penicillins and beta lactamase inhibitors and macrolides (38). The rate of using second generation cephalosporins use was 6% while third generation cephalosporins were 13%. In another study, cephalosporins use for antibiotic prophylaxis was at 67% (39).

A systematic review found that for MRSA eradication, linezolid performed better than vancomycin however amoxicillin clavulanic offered better prophylaxis against MRSA infections (40, 41). Klebsiella pneumonia responds well to polymixin combinations and aminoglycosides (42). A study carried out in Clayton, Australia; found that flucloxacillin continuous infusion offered good activity against wound infections with MSSA (43). Antimicrobial treatment of non-healing polymicrobial and/or clinically infected wounds should be targeted to cover most of the potentially synergistic aerobic or facultative and anaerobic microorganisms and not simply target specific common pathogens e.g. Staphylococcus aureus and Pseudomonas aeruginosa (44). The International working group on the diabetic foot recommends intravenous or oral use of empirical broad spectrum antibiotics in deep foot infections. The regimens that can be used include; ampicillin/ salbactum, ticacillin/clavulanate, amoxicillin/ clavulanate, clindamycin and a quinolone, a second or third generation cephalosporins with a quinolone or metronidazole with a quinolone” (45). A study carried out at Cardiff, Wales University found that antibiotic prescribing for wound infection was based on expert opinion and not scientific facts (9). The antibiotics that were commonly used included; flucloxacillin, co-amoxi-clav, cefaclor, cefalexin, erythromycin, trimethoprim, metronidazole and ciprofloxacin. Flucloxacillin, co- amoxiclav and metronidazole were mostly prescribed.

A study carried out at the Kenyatta National Hospital found that the antibiotics were mostly used for wound infections: flucloxacillin, gentamicin, ceftriaxone, cefuroxime, augmentin, amoxicillin, ciprofloxacin, ceftazidime, cloxacillin, antituberculous drugs, chloramphenicol and erythromycin (29).


Wound infections are caused mostly by Staphylococcus aureus, Streptococcus pyogenes, enterococci, Pseudomonas aeruginosa, Escherichia coli and Streptococcus epidermidis (23). The infection can be either by a single or multiple organisms. The antibiotic susceptibility patterns for each bacterium differ therefore for effective and appropriate management of bacterial wound infections it is important to identify the causative bacteria and its sensitivity patterns.


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