Francisco L. Sapico

Quantitative microbiology of pressure sores in different stages of healing

The quantitative microbiology of 25 pressure sores in different stages of healing was examined in 25 patients with spinal cord injury. When grossly necrotic tissue was present (stage 1), 5.8 isolates per patient with a density of 6.4 log10/g was recovered, with comparable findings for aerobes and anaerobes. In the absence of necrotic tissue but with the presence of undermining (stage 2), 1.5 aerobic and 0.2 anaerobic isolates were recovered per patient with a mean density of 2.7 and 0.1 log10/g of tissue for aerobic and anaerobic isolates, respectively. The lesions were almost sterile in patients with no necrotic tissue and no undermining (stage 3). Foul smell was always associated with the presence of anaerobes in deep tissue cultures, however, six patients with nonfoul-smelling lesions yielded anaerobes. A 75% quantitative concordance was seen between swab and biopsy culture results. The quantitative concordance between peripheral and central biopsy culture results was 63%, showing variability in results from different sampling areas. No relationship was observed between the density of microorganisms and the eventual outcome of the myocutaneous flap procedure.

Randomized controlled trial of topical hyperbaric oxygen for treatment of diabetic foot ulcers.

The effect of 2 wk of topical hyperbaric oxygen (THO) treatment on the healing of diabetic foot ulcers without associated gangrene was evaluated in a prospective, controlled, and randomized manner in 28 patients. There were 12 patients in the THO group (group 1) and 16 in the control group (group 2). Clinical management of the two patient groups was similar except for THO treatment in the group 1 patients. Clinical parameters, including age, sex, baseline fasting serum glucose levels, duration of diabetes mellitus, duration of foot ulcers, presence of peripheral neuropathy or arterial insufficiency, and evidence of osteomyelitis as determined by radiographs and/or radionuclide scans, were comparable in both groups of patients. No statistical differences (Students t test) were seen in the number of microorganisms isolated from curettage cultures of the base of the ulcer at days 0, 7, and 14 of the study between groups 1 and 2. In contrast to previous studies, there was a paucity of anaerobic microorganisms isolated from these foot ulcers without associated gangrenous changes. Ulcer areas were estimated by multiplying the maximum width by the maximum length in millimeters at days 0, 7, and 14. Analysis of variance and Students t test revealed progressive significant reductions in the ulcer areas in both groups when days 0, 7, and 14 were compared and in ulcer depths in both groups when days 0 and 14 were compared. However, such ulcer size changes did not differ statistically between the control and THO groups. A trend toward slower healing was observed in the From the THO group. Healing of diabetic foot ulcers was not accelerated by THO in this study.

Vertebral Osteomyelitis Due to Salmonellae: Report of Two Cases and Review

We describe two patients with salmonella vertebral osteomyelitis (SVO) and review 44 cases in the English-language literature. There was male predominance (distribution, 1.7:1), primarily lumbar involvement (72% of cases), and monomicrobial etiology. Fever (87% of cases) and back pain (92% of cases) were the dominant signs and symptoms, while diarrhea was present only in 16% of cases. Blood culture was positive in 48% of cases, and stool and urine cultures were positive in 36% and 23% of cases, respectively. The overall cure rate was 61%, and the relapse rate was 9%. Infected abdominal aortic aneurysms (IAAAs) were seen exclusively in the older age group (50 years of age or older), and all deaths occurred in these patients. The mean duration of antibiotic use for patients who were cured was 60 days. Although SVO is primarily treated medically, certain cases may require individualized surgical intervention. Patients with concomitant IAAAs may need resection with thorough debridement, extraanatomic bypass grafting, and prolonged antibiotic therapy.

Persistence of polymicrobial abscesses in the poorly controlled diabetic host

Polymicrobial infections are frequently found in soft tissue infections of the lower extremities in diabetic patients. The relative susceptibility to and persistence of soft tissue polymicrobial infections of diabetic and nondiabetic mice using bacteria commonly found in clinical foot infections were studied. Subcutaneous abscesses were induced in three groups of diabetic and nondiabetic mice using: (1) E. coli and enterococcus, (2) enterococcus and Bacteroides fragilis (B. fragilis), and (3) E. coli and B. fragilis. Abscesses were removed at 1 and 2 wk for total colony counts. At 1 wk, there was a significantly greater bacterial growth in the abscesses of the diabetic mice compared with the nondiabetic mice only in the group injected with enterococcus and B. fragilis. There were significantly higher colony counts in the diabetic compared with the nondiabetic mice in all three groups at 2 wk after injection of the bacteria. Two weeks after injection of inocula containing B. fragilis, both in combination with E. coli or enterococcus, all nondiabetic mice had eradicated B. fragilis from the abscesses, but significant numbers of B. fragilis persisted in the abscesses of the diabetic mice. In the diabetic mice, the presence of enterococci was more synergistic for growth of B. fragilis than was the presence of E. coli. These studies demonstrate that the bacteria of polymicrobial soft tissue infections persist for a longer period of time in the diabetic compared with the nondiabetic host. In addition, B. fragilis has increased pathogenicity in the diabetic compared with the nondiabetic host, particularly in the presence of enterococci.

LY146032, alone and in combination with gentamicin, for the treatment of enterococcal pyelonephritis in the rat model.

The in vivo and in vitro activity of LY146032 against Streptococcus faecalis GK was examined. The following MICs and MBCs in micrograms per milliliter were obtained: ampicillin, 0.8 and 1.5; vancomycin, 0.8 and 50; gentamicin, 12 and 25; and LY146032, 0.8 and 6. A time-kill-curve study involving approximately 10(6) organisms per ml showed a drop in the number of organisms of almost 2 log10 in the tube containing LY146032 (2 micrograms/ml) plus gentamicin (4 micrograms/ml) compared with bacterial numbers for the control at 4 h of incubation. However, regrowth was observed at 24 and 48 h, and no in vitro synergism was observed with the combination. A sample (1 ml) of overnight growth of this enterococcal strain at a concentration of 10(7) was then injected intravenously into 184 male Wistar rats weighing about 100 g each. After 12 days, 10 rats were sacrificed and the remaining ones were randomized into four treatment groups: (i) untreated control, (ii) LY146032 (3 mg) given subcutaneously, (iii) gentamicin (0.8 mg) given intramuscularly, and (iv) LY146032 plus gentamicin at the same dosages as when the drugs were used singly. The rats received antibiotics for 4 weeks twice daily, and approximately 10 rats in each group were sacrificed for quantitative kidney cultures at 1, 2, 4, and 6 weeks after the start of therapy. At the end of the 4- and 6-week periods, significantly better results were obtained with the combination of LY146032 plus gentamicin than with no treatment or treatment with single antibiotics.

Bacteremia in Diabetic Patients with Infected Lower Extremities

Eleven cases of bacteremia in diabetic patients with infected lower extremities at Rancho Los Amigos Hospital (RLAH) were observed over a 34-mo period. The yearly incidence was 0.6% of admissions to the Ortho-Diabetes service. Aerobic bacteria were recovered in six cases and anaerobic bacteria in five. Bacteroides fragilis was isolated four times, Staphylococcus aureus three times, and nonfragilis Bacteroides sp., Escherichia coli, group B streptococcus, and viridans streptococcus were each seen once. Ten of the 11 patients were febrile at the time of bacteremia. Clinical, laboratory, radiologic, and ultrasonographic parameters were comparable in patients with aerobic and anaerobic bacteremia, and between bacteremi patients and nonbacteremic controls. Fever, however, was significantly more frequent in bacteremic patients. Foul-smelling lesions were seen in two of the five patients with anaerobic bacteremia, and in none of the patients with aerobic bacteremia. Postoperative B. fragilis bacteremia was observed to be transient and resolved without definitive therapy in one patient. Appropriate antibiotic therapy in 10 patients together with surgical intervention in eight cases resulted in resolution of the infection in the remaining patients.

Methicillin-resistant Staphylococcus aureus bacteriuria

Methicillin-resistant Staphylococcus aureus (MRSA) bacteriuria was detected in 11 of 41 patients colonized or infected with MRSA. The patients with bacteriuria generally were older than 40 years of age, five were diabetic, seven had prior indwelling urethral catheters, two had undergone other urologic manipulations, and only one was clinically symptomatic. Eight patients received variable combinations of antibiotic therapy prior to the diagnosis of MRSA bacteriuria, and seven were still on antibiotic therapy at the time the bacteriuria was detected. Bacteriuria lasted four days to 14 weeks, and was eradicated promptly with cephalosporin therapy in five of six patients. Bacteriuria in the untreated patients cleared spontaneously in one month. A single MRSA serotype (83A) predominated. The MRSA isolates were resistant in vitro to most antibiotics except vancomycin. Resistant colonies were observed within cephalothin disc zones of inhibition at 30C (resistance was confirmed by microtube-dilution sensitivity testing). MRSA disc sensitivity testing for cephalothin may be unreliable when performed at 35C. (Am J Med Sci 281(2):101–109.)

In vitro susceptibility of methicillin-resistant and methicillin-susceptible Staphylococcus aureus strains to N-formimidoyl thienamycin.

A total of 82 clinical isolates of methicillin-resistant Staphylococcus aureus and 21 isolates of methicillin-susceptible S. aureus were studied for in vitro susceptibility to N-forminidoyl thienamycin at incubation temperatures of 30 and 35 degrees C. The disk diffusion test results were correlated with the macrobroth dilution test by means of the error rate-bounded method of analysis. Both methicillin-susceptible and (to a lesser degree) methicillin-resistant strains were generally susceptible to the antibiotic as judged from their minimum inhibitory concentrations. The discrepancy between in vitro results obtained at 30 and at 35 degrees C was not very remarkable. However, tolerance of N-formimidoyl thienamycin was observed in 37% of methicillin-resistant strains and 24% of methicillin-susceptible strains at an incubation temperature of 30 degrees C; at 35 degrees C, the values were 54% (methicillin-resistant strains) and 14% (methicillin-susceptible strains).

Temperature Effect on the Susceptibility of Methicillin-Resistant Staphylococcus aureus to Four Different Cephalosporins

Forty isolates of methicillin-resistant Staphylococcus aureus were tested for in vitro susceptibility to cephalothin, cefamandole, cefotaxime, and moxalactam, using the disk diffusion and microbroth dilution methods at incubation temperatures of 30 and 35°C. Resistance to all four antibiotics was more clearly evident at an incubation temperature of 30°C.

Experimental enterococcal endocarditis. II. Study of in vivo synergism of penicillin and streptomycin.

Intravenous doses of 100 mg of streptomycin and 100,000 units of penicillin G were given separately and in combination to a dog with chronic enterococcal bacteremia. Serial quantitative blood cultures in standard and hyperosmolar media and simultaneous serum antibiotic assays were performed. Streptomycin alone had no demonstrable effect on the level ol bacteremia. Penicillin alone reduced lower levels of pre-antibiotic bacteremia, followed by an early rise at four to five hours after injection. With higher pre-antibiotic bacteremia, this rise was detected as early as two hours after antibiotic injection. Penicillin plus streptomycin produced a more rapid and more pronounced depression which was sustained for longer than six hours. This in vivo killing effect lasted longer than detectable serum antibiotic concentrations. Following penicillin administration, persistently higher bacterial counts were obtained in the hyperosmolar medium than in the standard medium. This finding suggests the production of osmotically fragile forms of the organism after single doses of intravenous penicillin. This study corroborates previous in vitro observations of synergism of penicillin and streptomycin against enterococci.