Modified prophylaxis for preventing deep sternal wound infection after cardiac surgery

In order to prevent deep sternal wound infection after cardiac surgery we decided at the Sahlgrenska University Hospital to revise our protocol for antibiotic prophylaxis by adding an application of local collagen-gentamicin between the sternum halves to our standard prophylaxis. In addition, we focused specifically on the wiring technique. This quite simple modification of the prophylaxis program has been successful. The infection rate during 2006 is the lowest rate we have recorded since we started measuring it in 1995. We conclude that with application of local collagen-gentamicin and modification of the sternal closure method we have been able to significantly decrease the incidence of wound infections after cardiac surgery.     

Microbiology of animal bite wound infections

The microbiology of animal bite wound infections in humans is often polymicrobial, with a broad mixture of aerobic and anaerobic microorganisms. Bacteria recovered from infected bite wounds are most often reflective of the oral flora of the biting animal, which can also be influenced by the microbiome of their ingested prey and other foods. Bacteria may also originate from the victim's own skin or the physical environment at the time of injury. Our review has focused on bite wound infections in humans from dogs, cats, and a variety of other animals such as monkeys, bears, pigs, ferrets, horses, sheep, Tasmanian devils, snakes, Komodo dragons, monitor lizards, iguanas, alligators/crocodiles, rats, guinea pigs, hamsters, prairie dogs, swans, and sharks. The medical literature in this area has been made up mostly of small case series or case reports. Very few studies have been systematic and are often limited to dog or cat bite injuries. Limitations of studies include a lack of established or inconsistent criteria for an infected wound and a failure to utilize optimal techniques in pathogen isolation, especially for anaerobic organisms. There is also a lack of an understanding of the pathogenic significance of all cultured organisms. Gathering information and conducting research in a more systematic and methodical fashion through an organized research network, including zoos, veterinary practices, and rural clinics and hospitals, are needed to better define the microbiology of animal bite wound infections in humans.     

Restriction fragment analysis of a Candida tropicalis outbreak of sternal wound infections.

An apparent single-source outbreak of Candida tropicalis sternal wound infections in eight patients was investigated by utilizing DNA restriction fragment analysis (RFA) with HindIII and BstNI. All eight outbreak isolates appeared to be identical and were easily differentiated from control isolates by DNA RFA. Compared with an arbitrarily selected reference outbreak isolate, greater than or equal to 95% of the bands in the restriction digests identified by a computerized image analysis system from each of the outbreak isolates were identical versus 13 to 53% of the bands in any of the nine control isolates. Outbreak strains were significantly more likely to match the reference outbreak isolate than were controls (P less than 0.0001). The RFA was greatly facilitated by the use of computerized image analysis and confirmed the epidemiologic link between a scrub nurse and the infected patients.     

Prevention of sternal wound infections with locally administered gentamicin

Despite modern surgical techniques and our knowledge of the pathogenesis of surgical site infections (SSIs) and the use of perioperative antibiotic prophylaxis, the incidence of SSIs has not decreased, but has remained at the same level. More effective preventive methods are thus needed and will likely become even more important in the future due to older and sicker patients, the population becoming increasingly obese, type II diabetes becoming more common, and the emergence of resistant bacteria. The use of local antimicrobial prophylaxis was studied. The study population comprised 557 patients who underwent elective CABG. The patients were randomized and patients in the study group received a 10 cm x 10 cm gentamicin-collagen implant. Postoperative SSI occurred in 11 of 272 patients (4.0%) in the study group and in 16 of 270 patients (5.9%) in the control group. This difference was not statistically significant (P=0.20). There were three cases of mediastinitis (1.1%) in the study group and five (1.9%) in the control group (P=0.47).     

Microbiology of secondary bacterial infection in scabies lesions.

Aerobic and anaerobic bacteria were grown from specimens obtained from 30 children with secondarily infected scabies lesions. Aerobic or facultative bacteria only were present in 14 (47%) patients, anaerobic bacteria only were present in 6 (20%) patients, and a mixed anaerobic-aerobic flora was present in 10 (33%) patients. Fifty isolates were recovered (1.7 per specimen); 27 were aerobic or facultative bacteria and 23 were strict anaerobes. The predominant aerobic and facultative bacteria were Staphylococcus aureus (nine isolates), group A streptococci (five isolates), and Pseudomonas aeruginosa (three isolates). The predominant anaerobes were Peptostreptococcus sp. (nine isolates) and pigmented Prevotella and Porphyromonas spp. (four isolates). Single bacterial isolates were recovered from nine (30%) patients; five of these were S. aureus. Sixteen organisms isolated from 12 (40%) patients produced the enzyme beta-lactamase. Organisms that resided in the mucous membranes close to or in contact with the lesions predominated in those infections. Enteric gram-negative rods were recovered in leg and trunk lesions. Group A streptococci and S. aureus predominated in finger and hand lesions. Bacteroides fragilis group and Clostridium sp. were isolated from leg lesions, and pigmented Prevotella sp. and Porphyromonas and Fusobacterium spp. were recovered from finger lesions. The polymicrobial etiology of secondarily infected scabies lesions in children and the association of bacterial flora with the anatomical sites of the lesions are demonstrated.     

Local collagen-gentamicin for prevention of sternal wound infections: the LOGIP trial

In cardiac surgery, sternal wound infection (SWI) continues to be one of the most serious postoperative complications. Coagulase-negative staphylococci (CoNS) have become the most common causative agents of SWI. However, many CoNS species are resistant to routine intravenous antibiotic prophylaxis. 2000 cardiac surgery patients were randomised to routine prophylaxis with intravenous isoxazolyl penicillin alone (control group) or to this prophylaxis combined with application of collagen-gentamicin (260 mg gentamicin) sponges within the sternotomy before wound closure. The primary end-point was any sternal wound infection within 2 months postoperatively. The incidence of any sternal wound infection was 4.3% in the treatment group and 9.0% in the control group (relative risk=0.47; 95% confidence interval 0.33 to 0.68; P<0.001). Local gentamicin reduced the incidence of SWI caused by all major clinically important microbiological agents, including CoNS. Routine use of the described prophylaxis in all adult cardiac surgery patients could be recommended.     

Surgical wound infection caused by Rahnella aquatilis.

Rahnella aquatilis is a water-residing gram-negative rod, a member of the family Enterobacteriaceae, isolated rarely from clinical specimens of immunocompromised patients. A case of a surgical wound infection caused by R. aquatilis in a patient who underwent a prosthetic surgical intervention is reported. The presence of inducible beta-lactamase was suggested by the disk induction test and the conventional agar dilution assay. Literature on R. aquatilis infections in humans is reviewed.     

Granulocyte function and Pseudomonas burn wound infection.

Granulocyte function in burn injury has been evaluated with an in vitro animal assay. Bactericidal activity, using this technique, was markedly depressed only when granulocytes from scald burned rats were challenged with each of three strains of Pseudomonas aeruginosa in the presence of autologous postburn serum or heat-inactivated serum. Preincubation of postburn and normal serum at 37 degrees C for 1 h resulted in normal phagocytosis. These studies validate an investigation of plasma and/or granulocyte replacement therapy in the burned patient.     

Microbiology of infection in mechanical circulatory support

The results of MCSS therapy for patients with severe heart failure are improving, and there are increasing numbers of implants as device therapy enters the era of permanent use (i.e., destination therapy). Device-related infection of implanted pumps and sepsis remain important risk factors for death, and once infections are established on biomaterial surfaces they usually persist despite prolonged antimicrobial therapy. This paper covers the topic of infection in mechanical circulatory support. Methods to prevent and manage infection are described. Recent information from the field of microbiology that is relevant to understanding device-related infection is reviewed, including the mechanisms for microbial adhesion to prosthetic surfaces, quorum sensing, and biofilm formation. Characteristics that are important to antimicrobial resistance of microbes dwelling in biofilms are described (e.g. responses to microenvironmental conditions that result in resistance to antibiotics). This information may lead to new therapies that further diminish rates of device infection, and allow complete eradication of infections when they occur.     

Characteristics of war wound infection

War wounds are the most complex type of non-targeted injuries due to uncontrolled tissue damage of varied and multifold localizations, exposing sterile body areas to contamination with a huge amount of bacteria. Wound contamination is caused by both the host microflora and exogenous agents from the environment (bullets, cloth fragments, dust, dirt, water) due to destruction of the host protective barriers. War wounds are the consequence of destructive effects of various types of projectiles, which result in massive tissue devitalization, hematomas, and compromised circulation with tissue ischemia or anoxia. This environment is highly favorable for proliferation of bacteria and their invasion in the surrounding tissue over a relatively short period of time. War wounds are associated with a high risk of local and systemic infection. The infection will develop unless a timely combined treatment is undertaken, including surgical intervention within 6 hours of wounding and antibiotic therapy administered immediately or at latest in 3 hours of wound infliction. Time is a crucial factor in this type of targeted combined treatment consisting of surgical debridement, appropriate empirical antimicrobial therapy, and specific antitetanic prophylaxis. Apart from exposure factors, there are a number of predisposing factors that favor the development of polymicrobial aerobic-anaerobic infection. These are shock, pain, blood loss, hypoxia, hematomas, type and amount of traumatized tissue, age, and comorbidity factors in the wounded. The determinants that define the spectrum of etiologic agents in contaminated war wounds are: wound type, body region involved, time interval between wounding and primary surgical treatment, climate factors, season, geographical area, hygienic conditions, and patient habits. The etiologic agents of infection include gram-positive aerobic cocci, i. e. Staphylococcus spp, Streptococcus spp and Enterococcus spp, which belong to the physiological flora of the human skin and mucosa; gram-negative facultative aerobic rods; members of the family Enterobacteriacea (Escherichia coil, Proteus mirabilis, Klebsiella pneumoniae, Enterobacter cloacae), which predominate in the physiological flora of the intestines, transitory flora of the skin and environment; gram-negative bacteria, i. e. Pseudomonas aeruginosa, Serratia marcescens, Acinetobacter calcoaceticus - A. baumanii complex; environmental bacteria associated with humid environment and dust; anaerobic gram-positive sporogeneous rods Clostridium spp, gram-negative asporogeneous rods Bacteroides spp and gram-positive anaerobic cocci; Peptostreptococcus spp and Peptococcus spp. The latter usually colonize the intestine, primarily the colon, and the skin, while clostridium spores are also found in the environment. Early empirical antibiotic therapy is used instead of standard antibiotic prophylaxis. Empirical antimicrobial therapy is administered to prevent the development of systemic infection, gas gangrene, necrotizing infection of soft tissue, intoxication and death. The choice of antibiotics is determined by the presumed infective agents and localization of the wound. It is used in all types of war wounds over 5-7-10 days. The characteristics of antibiotics used in war wounds are the following: broad spectrum of activity, ability to penetrate deep into the tissue, low toxicity, long half-life, easy storage and application, and cost effectiveness. The use of antibiotics is not a substitution for surgical treatment. The expected incidence of infection, according to literature data, is 35%-40%. If the time elapsed until surgical debridement exceeds 12 hours, or the administration of antibiotics exceeds 6 hours of wound infliction, primary infection of the war wound occurs (early infection) in more than 50% of cases. The keys for the prevention of infection are prompt and thorough surgical exploration of the wound, administration of antibiotics and antitetanic prophylaxis, awareness of the probable pathogens with respect to localization of the wound, and optimal choice of antibiotics and length of their administration.     

Coagulase-negative staphylococci isolated from sternal wound infections after cardiac surgery: attachment to and accumulation on sternal fixation stainless steel wires

Sternal wound infection (SWI) is a serious complication after cardiac surgery. Coagulase-negative staphylococci (CoNS) have been found to be the most common pathogen involved in this postoperative infection related to implanted foreign materials, i.e. sternal fixation wires made from stainless steel. In this study a rapid and simple assay was developed for studying attachment and accumulation of CoNS on stainless steel wires in vitro using [(3)H] thymidine. The method showed a potential to detect differences in the dynamics of the adherence patterns among various CoNS isolates. However, no differences in attachment and accumulation were found between isolates causing deep SWI after cardiac surgery and contaminant isolates. In addition, there were no differences in the distribution of the ica operon between the two groups, as determined by polymerase chain reaction (PCR). Nevertheless, the ability to produce biofilm was found to be present significantly more frequently among SWI isolates than among contaminants.     

A mathematical analysis of alternative sternal wound closures--an aid to reducing cardiac surgical mortality

Sternal dehiscence is an important complication of cardiac surgery. A simple mathematical analysis is described for determining the relative strength (S) of different types of sternal closure. This is based upon resolving the tensions within the segments of a sternal wire to derive a dehiscence force. The strength of the closure (S) is the ratio of the volume of sternum which the dehiscence force acts upon to the dehiscence force itself. The derived S values varied from 4.3 for a closure using 6 transverse wires to 11.4 for a closure using the Modified Technique. The analysis suggested that closures which redistribute the transverse force to act obliquely upon a greater volume of sternum, such as the Modified Technique, are less likely to fail.     

New sternal puncture needle.

The needles most commonly used for obtaining bone marrow aspirates from the sternum are the Salah and Klima needles. They were designed in the 1930s, and except for the introduction of different kinds of stops and guards there has been no change in their basic structure and design. These instruments are small, do not fit properly in the operator's hand, and the lack of a T-bar handle often makes them difficult to manoeuvre; their introduction into the sternum by twisting or rotary movement of the hand can be cumbersome. To overcome all of these disadvantages an instrument was designed which is larger, provides better grip, and offers improved maneuverability. The stilette of this aspiration needle has a domed handle which rests snugly in the operator's hand and affords operator comfort, while the specially shaped large T-bar handle at the proximal end of the needle provides adequate and firm grip and also ensures precise control during the sternal puncture procedure.     

Aeromonas primary wound infection of a diver in polluted waters.

Two separate species of Aeromonas, A. sobria (not listed as a species in Bergey's Manual of Determinative Bacteriology, 8th ed.) and A. hydrophila, were primary pathogens isolated from the leg wound of a diver conducting operations in polluted waters. This is the first recorded instance of a primary infection of soft tissue in a human caused by two species of Aeromonas, one of which was resistant to tetracycline. Because of the very rapid development of this wound infection, cytotoxicity of these organisms was examined in several biological systems. A. sobria was hemolytic for sheep erythrocytes, cytotoxic for Y-1 adrenal cells, and enterotoxic in rabbit ligated intestinal loops, whereas A. hydrophila was hemolytic and cytotoxic. Pertinent clinical, bacteriological, and environmental features of the case are presented.