Bacterial clearance of biologic grafts used in hernia repair: an experimental study.

BACKGROUND: Biologic grafts used in ventral hernia repair are derived from various sources and undergo different post-tissue-harvesting processing, handling, and sterilization techniques. It is unclear how these various characteristics impact graft response in the setting of contamination. We evaluated four materials in an infected hernia repair animal model using fluorescence imaging and quantitative culture studies. METHODS: One hundred seven rats underwent creation of a chronic hernia. They were then repaired with one synthetic polyester control material (n = 12) and four different biologic grafts (n = 24 per material). Biologic grafts evaluated included Surgisis (porcine small intestinal submucosa), Permacol (crosslinked porcine dermis), Xenmatrix (noncrosslinked porcine dermis), and Strattice (noncrosslinked porcine dermis). Half of the repairs in each group were inoculated with Staphylococcus aureus at 10(4) CFU/ml and survived for 30 days without systemic antibiotics. Animals then underwent fluorescence imaging and quantitative bacterial studies. RESULTS: All clean repairs remained sterile. Rates of bacterial clearance were as follows: polyester synthetic 0%, Surgisis 58%, Permacol 67%, Xenmatrix 75%, and Strattice 92% (P=0.003). Quantitative bacterial counts had a similar trend in bacterial clearance: polyester synthetic 1×10(6) CFU/g, Surgisis 4.3×10(5) CFU/g, Permacol 1.7×10(3) CFU/g, Xenmatrix 46 CFU/g, and Strattice 31 CFU/g (P=0.001). Fluorescence imaging was unable to detect low bacterial fluorescence counts observed on bacterial studies. CONCLUSION: Biologic grafts, in comparison to synthetic material, are able to clear a Staphylococcus aureus contamination; however, they are able to do so at different rates. Bacterial clearance correlated to the level of residual bacterial burden observed in our study. Post-tissue-harvesting processing, handling, and sterilization techniques may contribute to this observed difference in ability to clear bacteria.

Characterization of penicillin intermediate serotypes of Streptococcus pneumoniae carried by human immunodeficiency virus-infected adults and healthy children in Uganda.

There are little data on the genetic relatedness between antibiotic-resistant pneumococcal isolates colonizing the Ugandan population. Penicillin-intermediate pneumococci of serogroups or serotypes rarely or not previously reported as being penicillin nonsusceptible were selected out of 166 isolates representing 26 capsular serogroups or serotypes isolated from Ugandan children in 1995 and human immunodeficiency virus (HIV) infected Ugandan adults in 2004-2005. Pairs of penicillin-intermediate pneumococci of the same serogroup or serotype present in both patient populations were characterized further by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Seven such pairs of isolates were found and included serogroups 7, 11, 15B/C, and 16 as well as serotypes 13, 21, and 35B. PFGE of these seven pairs showed no clonality between serogroups or serotypes, and clonality only within serogroup 11 and serotype 13. MLST of the 14 individual isolates revealed 13 different sequence types (STs), 11 of which had not previously been recorded. Comparisons with all known STs revealed that most of these strains were related only to strains of the same serotype in other countries, with these related strains frequently also being penicillin intermediate. These findings suggest that penicillin nonsusceptibility in Uganda is likely due to the introduction of antibiotic-resistant pneumococcal clones into Uganda rather than development of resistance within the country.

Alterations of penicillin-binding proteins 1A, 2X, and 2B in Streptococcus pneumoniae isolates for which amoxicillin MICs are higher than penicillin MICs.

Penicillin-binding proteins (PBPs) of 15 selected penicillin- and amoxicillin-resistant Streptococcus pneumoniae isolates (MICs of 2 to 8 and 8 to 16 microg/ml, respectively) were studied. In addition to typical changes in PBPs 1A and 2X, these strains had 10 unique changes in PBP 2B, including a (618)A-G substitution, which may be the key alteration associated with amoxicillin resistance.

Macrolide resistance phenotypes in Streptococcus pneumoniae in Santiago, Chile.

The mechanism of resistance was investigated in 39 macrolide-resistant clinical isolates of Streptococcus pneumoniae isolated from January 1997 to July 1999 in Santiago, Chile. Our results showed that 22 (56.5%) were macrolide-resistant, clindamycin-susceptible isolates (M phenotype) and 17 (43.5%) were macrolide and clindamycin resistant (MLS(B) phenotype). mefE gene was detected in all M phenotype, while ermB gene was detected in all MLS(B)-phenotype strains. Serotype 14 was the most frequent serotype among M-phenotype strains, and serotypes 19 and 23F were the most frequent serotypes in MLS(B) strains. These results demonstrate that both phenotypes of macrolide-resistant S. pneumoniae are found in Santiago, Chile, with the M phenotype predominating.

Clinically significant concentrations of local anesthetics inhibit Staphylococcus aureus in vitro.

This study explores which concentrations of local anesthetics might be expected to inhibit the growth of Staphylococcus aureus. Serial dilutions were made of 0.5% and 0.75% bupivacaine, 2% and 5% lidocaine, 2% and 3% chloroprocaine, and 0.2% and 1% ropivacaine. To each concentration of local anesthetic solution, Mueller Hinton broth medium and Staphylococcus aureus were added. The resulting solutions were incubated and then observed for growth 24 and 48 h later. The minimum concentrations of the local anesthetics that could inhibit growth of Staphylococcus aureus were 0.25% bupivacaine, 1.25% lidocaine and 0.75% chloroprocaine. The inhibitory concentration of ropivacaine could not be determined because the more concentrated solutions precipitated in the Mueller Hinton broth. Local anesthetics may help protect against epidural abscess formation if they are used in sufficiently high concentrations. This effect may help explain the very low reported incidence of epidural abscess.

Pneumococcal conjugate vaccine serotypes of Streptococcus pneumoniae isolates and the antimicrobial susceptibility of such isolates in children with otitis media.

The ability of the recently licensed 7-valent pneumococcal conjugate vaccine to cover isolates that cause otitis media, especially drug-resistant ones, was assessed using 500 recently obtained US isolates. Of these isolates, 418 (84%) belonged to vaccine-related serogroups, whereas 82 (16%) belonged to non-vaccine-related serogroups. Serotype 3 accounted for 48 (59%) of the non-vaccine-related serogroups. In addition, 93% of the isolates from patients < or =3 years of age belonged to serotypes that were included in or related to the heptavalent vaccine, compared with 49% of the isolates from older patients (P=.001). Most of the isolates (98%-100%) that were resistant to the antimicrobial agents tested were covered by the heptavalent vaccine, including 95.1% of the isolates from patients <2 years of age. The 7-valent pneumococcal conjugate vaccine could therefore potentially provide protection against all but 1 (type 3) of the common otitis media-associated pneumococcal serogroups identified in this study as well as against 98% of antibiotic-resistant isolates.

High prevalence of carriage of antibiotic-resistant Streptococcus pneumoniae in children in Kampala Uganda.

There are few data on antibiotic-resistant Streptococcus pneumoniae in Uganda. A total of 191 healthy children in Kampala, Uganda were screened for nasopharyngeal carriage of S. pneumoniae; 118 (62%) of the children were carriers. Antimicrobial susceptibility and serotype of 115 strains was determined. Ninety-six (83.5%) of the isolates were of intermediate resistance to penicillin and 19 (16.5%) were susceptible. All strains were susceptible to cefotaxime. The rates of resistance to other drugs were trimethoprim-sulphamethoxazole (83.5%), tetracycline (28.7%) and chloramphenicol (10.4%). All strains were susceptible to rifampicin, erythromycin and clindamycin. Serogroups 6, 9, 14, 19 and 23 accounted for 80% of the isolates. These data show that the rate of carriage of antibiotic-resistant pneumococci by children is high in Kampala, Uganda.

Susceptibilities of Haemophilus influenzae and Moraxella catarrhalis to ABT-773 compared to their susceptibilities to 11 other agents.

The activity of the ketolide ABT-773 against Haemophilus and Moraxella was compared to those of 11 other agents. Against 210 Haemophilus influenzae strains (39.0% beta-lactamase positive), microbroth dilution tests showed that azithromycin and ABT-773 had the lowest MICs (0.5 to 4.0 and 1.0 to 8.0 microg/ml, respectively), followed by clarithromycin and roxithromycin (4.0 to >32.0 microg/ml). Of the beta-lactams, ceftriaxone had the lowest MICs (32.0 microg/ml). Against 50 Moraxella catarrhalis strains, all of the compounds except amoxicillin and cefprozil were active. Time-kill studies against 10 H. influenzae strains showed that ABT-773, at two times the MIC, was bactericidal against 9 of 10 strains, with 99% killing of all strains at the MIC after 24 h; at 12 h, ABT-773 gave 90% killing of all strains at two times the MIC. At 3 and 6 h, killing by ABT-773 was slower, with 99.9% killing of four strains at two times the MIC after 6 h. Similar results were found for azithromycin, with slightly slower killing by erythromycin, clarithromycin, and roxithromycin, especially at earlier times. beta-Lactams were bactericidal against 8 to 10 strains at two times the MIC after 24 h, with slower killing at earlier time periods. Most compounds gave good killing of five M. catarrhalis strains, with beta-lactams killing more rapidly than other drugs. ABT-773 and azithromycin gave the longest postantibiotic effects (PAEs) of the ketolide-macrolide-azalide group tested (4.4 to >8.0 h), followed by clarithromycin, erythromycin, and roxithromycin. beta-Lactam PAEs were similar and shorter than those of the ketolide-macrolide-azalide group for all strains tested.

Prevalence and mechanisms of macrolide resistance in Streptococcus pyogenes in Santiago, Chile.

Thirty-two macrolide-resistant Streptococcus pyogenes isolates were found among 594 clinical isolates collected from 1990 to 1998 in Santiago, Chile, for an overall prevalence of 7.2%. Among the 32 resistant isolates, 28 (87.5%) presented the M phenotype and 4 (12. 5%) presented the MLS(B) phenotype. Serotyping and pulsed-field gel electrophoresis analysis showed genetic diversity among the resistant isolates.

Evaluation of Etest for susceptibility testing of Mycobacterium tuberculosis.

The Etest method for susceptibility testing of Mycobacterium tuberculosis was compared to the agar proportion method using four first-line agents and two fluoroquinolones. Catergorical agreement between the methods was 100% for rifampin, ethambutol, streptomycin, and ofloxacin and 98% for isoniazid. Results were obtained in 6 to 10 days by Etest. The Etest method is suitable for testing the agents evaluated against M. tuberculosis.

Determination of drug susceptibility and DNA fingerprint patterns of clinical isolates of Mycobacterium tuberculosis from Kampala, Uganda.

OBJECTIVE: To ascertain the rate of initial drug resistance and transmission patterns of Mycobacterium tuberculosis in Kampala, Uganda. SETTING: National Tuberculosis (TB) Treatment Centre, Mulago Hospital, Kampala, Uganda and Case Western Reserve University, Cleveland, Ohio, USA and McClellan Memorial Veterans Hospital, Little Rock, Arkansas, USA. METHODS: Using a radiometric BACTEC 460 TB system, susceptibility of 215 M. tuberculosis isolates from previously untreated patients from Kampala, Uganda (age range, 17-48 years, mean, 28 years; 56% males and 69% human immunodeficiency virus (HIV)-seropositive) was determined for isoniazid, rifampin, streptomycin and ethambutol. Isolates from 73 patients, selected on the basis of geographical location, were tested for strain diversity or relatedness using the IS6110 DNA fingerprinting technique. RESULTS: Resistance rates were as follows: isoniazid, 7.9% streptomycin, 6.1% rifampin, 1.4% and ethambutol 0.9%. Twelve per cent of the strains were resistant to at least one of the first line drugs tested and 4.7% were multiply resistant. There were no significant differences in resistance rates between patients with and without HIV infection. Using the number and size of DNA fragments containing IS6110, only three clusters of isolates with identical RFLP patterns were found out of the 73 isolates tested (8.2%). Each cluster contained two isolates. Three (4.1%) isolates had less than seven copies of IS6110. CONCLUSION: This study shows that in Uganda initial drug resistance rates to anti-tuberculosis agents are low and similar to other sub-Saharan African countries and that multiple strains of M. tuberculosis have been transmitted within the community.

PIP: This study was undertaken to determine the rate of initial drug resistance and transmission patterns of Mycobacterium tuberculosis (TB) in Kampala, Uganda. Using a radiometric BACTEC 460 TB system, 215 M. tuberculosis isolates from previously untreated patients (aged 17-48 years, mean age = 28 years; 56% males and 69% HIV-seropositive) were analyzed for susceptibility to isoniazid, rifampin, streptomycin, and ethambutol. Isolates from 73 patients were examined for strain diversity or relatedness using the insertional sequence 6110 (IS6110) DNA fingerprinting technique. The study revealed the following drug resistance rates: isoniazid, 7.9%; streptomycin, 6.1%; rifampin, 1.4%; and ethambutol, 0.9%. Resistance to at least one of the first line drugs tested were developed by 12% of the strains, while 4.7% showed multiple resistance. However, no significant differences in resistance rates were found between patients with and without HIV infection. Using the number and size of DNA fragments containing IS6110, only three clusters of isolates with identical patterns were found out of the 73 isolates tested (8.2%). Each cluster contained two isolates, and three isolates had less than 7 copies of IS6110. These findings suggest that initial drug resistance to anti-tuberculosis agents in this region is low and similar to other countries in sub-Saharan Africa and that multiple strains of M. tuberculosis have been transmitted within the community.

Activities and postantibiotic effects of gemifloxacin compared to those of 11 other agents against Haemophilus influenzae and Moraxella catarrhalis.

The activity of gemifloxacin against Haemophilus influenzae and Moraxella catarrhalis was compared to those of 11 other agents. All quinolones were very active (MICs,

Postantibiotic effects of grepafloxacin compared to those of five other agents against 12 gram-positive and -negative bacteria.

The postantibiotic effect (PAE) (10x the MIC) and the postantibiotic sub-MIC effects (0.125, 0.25, and 0.5x the MIC) were determined for six compounds against 12 strains. Measurable PAEs ranged between 0 and 1.8 h for grepafloxacin, 0 and 2.2 h for ciprofloxacin, 0 and 3. 1 h for levofloxacin, 0 and 2.2 h for sparfloxacin, 0 and 2.4 h for amoxicillin-clavulanate and 0 and 4.8 h for clarithromycin. Reexposure to subinhibitory concentrations increased the PAEs against some strains.

Prevalence of mefE, erm and tet(M) genes in Streptococcus pneumoniae strains from Central Italy.

One hundred and seventy-three Streptococcus pneumoniae strains isolated from surveillance studies conducted in daycare centres were studied. The mefE, erm and tet(M) genes were detected in 16.2, 45.1 and 47.4% of isolates respectively. Agreement between PCR results and antibiotic susceptibility patterns was 100%. Macrolide resistance was due to the presence of erm in 73.6% of strains and to the presence of mefE in the remaining 26.4%. All tetracycline resistant strains carried the tet(M) gene. erm was associated with tet(M) in 98.7% of strains, whereas no isolate carrying mefE carried tet(M). A significant association was found between mefE and serogroup 6 (P < 0.0005) and between erm and tet(M) and serogroup 19 (P < 0.00001).

Susceptibilities of Streptococcus pneumoniae and Haemophilus influenzae to 10 oral antimicrobial agents based on pharmacodynamic parameters: 1997 U.S. Surveillance study.

The susceptibilities of Streptococcus pneumoniae (1,476 strains) and untypeable Haemophilus influenzae (1,676 strains) to various oral beta-lactam, macrolide-azalide, and fluoroquinolone antimicrobial agents were determined by broth microdilution. Organisms were isolated from specimens obtained from outpatients in six geographic regions of the United States. MIC data were interpreted according to pharmacodynamically derived breakpoints applicable to the oral agents tested. Among H. influenzae strains, 41.6% were beta-lactamase positive. Virtually all H. influenzae strains were susceptible to amoxicillin-clavulanate (98%), cefixime (100%), and ciprofloxacin (100%), while 78% were susceptible to cefuroxime, 57% were susceptible to amoxicillin, 14% were susceptible to cefprozil, 9% were susceptible to loracarbef, 2% were susceptible to cefaclor, and 0% were susceptible to azithromycin and clarithromycin. Among S. pneumoniae isolates, 49.6% were penicillin susceptible, 17.9% were intermediate, and 32.5% were penicillin resistant, with penicillin MICs for 50 and 90% of the isolates tested of 0.12 and 4 microg/ml, respectively. Overall, 94% of S. pneumoniae isolates were susceptible to amoxicillin and amoxicillin-clavulanate, 69% were susceptible to azithromycin and clarithromycin, 63% were susceptible to cefprozil and cefuroxime, 52% were susceptible to cefixime, 22% were susceptible to cefaclor, and 11% were susceptible to loracarbef. Although ciprofloxacin has marginal activity against S. pneumoniae, no high-level fluoroquinolone-resistant strains were found. Significant cross-resistance was found between penicillin and macrolides-azalides among S. pneumoniae isolates, with 5% of the penicillin-susceptible strains being macrolide-azalide resistant, compared with 37% of the intermediate isolates and 66% of the resistant isolates. Resistance was highest in S. pneumoniae isolates from patients younger than 10 years of age, middle ear and paranasal sinus specimens, and the southern half of the United States. With the continuing rise in resistance, judicious use of oral antimicrobial agents is necessary in all age groups.

Resistance patterns of Streptococcus pneumoniae from children in central Italy.

Nasopharyngeal swabs were collected from children aged 3-5 years in central Italy who were attending day-care centres or hospital outpatient clinics. One hundred and twenty-one strains of Streptococcus pneumoniae isolated were tested for susceptibility to penicillin, cefotaxime, erythromycin, clindamycin, tetracycline, chloramphenicol and cotrimoxazole. A high prevalence of penicillin-resistant (14%), erythromycin-resistant (60%) and multiply resistant strains (53%) were found. An unusual finding was that 49 of the 64 (76.6%) multiply resistant strains were penicillin-susceptible, 28 serogroup 6 strains also being resistant to the other antibiotics tested. Such strains have not previously been reported from Italy but have the same features as strains recently found in child carriers in the eastern Mediterranean area.

Activity of HMR 3647 compared to those of five agents against Haemophilus influenzae and moraxella catarrhalis by MIC determination and time-kill assay.

The microdilution MICs of HMR 3647, erythromycin A, azithromycin, clarithromycin, roxithromycin, and pristinamycin against 50/90% of 249 Haemophilus influenzae and 50 Moraxella catarrhalis isolates were 2/4, 0.06/0.125; 8/16, 0.25/0.25; 2/4, 0.06/0.125; 16/16, 0.25/0.25; 32/>32, 1/2; and 2/4, 0.5/0.5 microg/ml. Azithromycin was bactericidal against all 10 H. influenzae and 3 of 5 M. catarrhalis isolates and HMR 3647, erythromycin A, clarithromycin, roxithromycin, and pristinamycin were bacteriostatic, against all 15 strains after 24 h at the MIC.

Synergistic activity of trovafloxacin with other agents against gram-positive and -negative organisms.

The synergistic activity of trovafloxacin with other agents against 55 Gram-positive and -negative bacteria was determined by checkerboard titration. Synergistic fractional inhibitory concentration (FIC) indices (< or = 0.5) were seen in two methicillin-susceptible and one methicillin-resistant Staphyloccocus aureus with teicoplanin, one of each of the latter two with vancomycin; one methicillin-resistant coagulase-negative Staphylococcus with rifampin and one with fusidic acid; five Stenotrophomonas maltophilia with cefoperazone; three Pseudomonas aeruginosa with ticarcillin/clavulanate, four with aztreonam, two with ceftazidime, one with tobramycin, one with cefoperazone, and one with ceftriaxone; one pneumococcus with ceftriaxone; one Enterococcus faecalis with ceftriaxone, and one with vancomycin; two Bacteroides fragilis with metronidazole, two with clindamycin, and one with cefoxitin; and one Clostridium perfringens with metronidazole and one with clindamycin. All other FIC indices were additive/indifferent (0.51-2.0), and no antagonistic FIC indices (> 4.0) were observed.

Determination of penicillin MICs for Streptococcus pneumoniae by using a two- or three-disk diffusion procedure.

The potential for the use of the disk diffusion method to accurately predict penicillin MICs for Streptococcus pneumoniae was investigated with penicillin (6 microg), methicillin (5 microg), and oxacillin (1 microg) disks. A total of 183 S. pneumoniae isolates were tested by three MIC procedures (agar dilution, microdilution, and E-test). Regression analyses of the geometric mean of the three MIC results against (i) the sum of the zone diameters for methicillin, penicillin, and oxacillin disks; (ii) the sum of the zone diameters for methicillin and penicillin disks; and (iii) each of the three individual zone diameters were performed. Calculated MICs were determined from each of these regression analyses and compared to the mean reference MICs. A high level of correlation was obtained with both the two- and the three-disk procedures (r = 0.97), with essential agreement rates (+/-1 doubling dilution) between MICs calculated by the three-disk procedure and the two-disk procedure and the mean reference MICs of 98.4 and 98.9%, respectively. No major or very major errors were obtained with the two- or three-disk procedures. The accuracy of the disks used individually was lower (r = 0.84 to 0.93). However, oxacillin and methicillin disk testing remain excellent for screening strains, with all penicillin-susceptible strains having zones of >21 and >22 mm, respectively. The combination disk procedure, which involves the use of three disks (methicillin, oxacillin, and penicillin) or two disks (methicillin and penicillin) for testing S. pneumoniae, can provide accurate penicillin MICs and qualitative category results that are comparable to results obtained by the E-test, agar, and microdilution MIC methods.

Resistance patterns of streptococcus pneumoniae from carriers attending day-care centers in southwestern Greece.

The resistance to beta-lactam and non-beta-lactam antibiotics of 133 nasopharyngeal isolates of Streptococcus pneumoniae recovered from December 1995 to February 1996 from children attending seven day-care centers in southwestern Greece was studied. Reduced susceptibility to one or more anti-microbial agents was found in 70 isolates (53%), as follows: penicillin, 17% intermediate, 12% resistant; cefotaxime, 10.5% intermediate, 1.5% resistant; trimethoprim-sulfamethoxazole, 8% intermediate, 35% resistant; chloramphenicol, 27% resistant; tetracycline, 29% resistant; and erythromycin/clindamycin, 19% resistant. Eighty-seven percent of penicillin-intermediate or -resistant strains belonged to serogroups/serotypes 19, 21, and 23. Fifty-six percent of the antibiotic-resistant pneumococci were multiply resistant, including serogroup 6 strains that were penicillin-susceptible but resistant to all non-beta-lactam drugs tested, as well as serogroup 23 strains resistant to penicillin, chloramphenicol, tetracycline, and trimethoprim-sulfamethoxazole. The high incidence of antibiotic-resistant pneumococci and the divergent and unique resistance patterns found in this study underline the need for global surveillance of S. pneumoniae to document the evolution and spread of resistant strains and to guide therapy.