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Biomedical subjects

A W Chow

Publications and source records attributed to A W Chow.

At least 73 records · Page 4Linked to original sources
PubMed1989

Determination by western blot (immunoblot) of seroconversions to toxic shock syndrome (TSS) toxin 1 and enterotoxin A, B, or C during infection with TSS- and non-TSS-associated Staphylococcus aureus.

Serum antibody responses to toxic shock syndrome (TSS) toxin 1 (TSST-1) and staphylococcal enterotoxins A, B, and C were determined by western blot (immunoblot) analysis of acute- and convalescent-phase paired sera from 18 TSS- and 31 non-TSS-associated Staphylococcus aureus infections. Compared with non-TSS cases, seroconversion to TSST-1 was significantly more frequent among both menstrual (5 of 8 versus 1 of 31; P less than 0.001) and nonmenstrual (3 of 10; P less than 0.05) patients. Seroconversion to staphylococcal enterotoxin A was also more frequent among both menstrual (2 of 8 versus 0 of 31; P less than 0.05) and nonmenstrual (2 of 9; P less than 0.05) TSS patients. In general, patients with TSS associated with TSST-1-positive S. aureus were more likely to seroconvert exclusively to TSST-1 (4 of 12 versus 0 of 6; P = 0.16), whereas those associated with TSST-1-negative S. aureus were more likely to seroconvert exclusively to enterotoxins (3 of 6 versus 0 of 11; P less than 0.05). Concurrent seroconversions to multiple exoproteins were more frequent among both menstrual (3 of 8; P less than 0.05) and nonmenstrual (2 of 9; P less than 0.05) TSS patients compared with persons without TSS (0 of 31). These data suggest but do not prove that enterotoxins (especially staphylococcal enterotoxin A) in addition to TSST-1 may be involved in both menstrual and nonmenstrual TSS. Furthermore, since exposure to multiple exoproteins is more likely to occur during TSS-associated than non-TSS-associated S. aureus infections, the possibility of additive or synergistic effects of these putative toxins in the pathogenesis of TSS should be further explored.

Acute Disease↗
PubMed1989

Colony immunoblot assay for the detection of staphylococcal toxic shock syndrome toxin 1 (TSST-1) with anti-TSST-1 F(ab')2 fragments.

Toxic shock syndrome toxin 1 (TSST-1), an exoprotein of Staphylococcus aureus, is strongly implicated in the pathogenesis of TSS. Detection of TSST-1, however, is often hindered in immunoassays because of the cosecretion of protein A, a genetic trait which appears to be coordinately expressed with other exoproteins in S. aureus. We developed a colony immunoblot assay for rapid screening of TSST-1-producing S. aureus using TSST-1-specific rabbit F(ab')2 fragments. The sensitivity and specificity of this method were compared with those of a quantitative noncompetitive enzyme-linked immunosorbent assay (ELISA) for 34 S. aureus isolates (17 TSS-associated and 17 non-TSS-associated isolates). Cosecreted protein A in culture supernatants was evaluated by a quantitative competitive ELISA. The results clearly indicated the superiority of F(ab')2 fragments in eliminating nonspecific reactivity of protein A in the colony immunoblot assay. The sensitivity of the immunoblot with TSST-1-specific F(ab')2 was similar to that with whole immunoglobulin G (94 versus 82%, respectively; P = 0.601, Fisher's exact test), but the specificity was markedly improved (94 versus 59%, respectively; P = 0.039). Among TSST-1-negative isolates (as determined by ELISA), strains which gave false-positive results in the immunoglobulin G immunoblot assay produced higher amounts of protein A than strains which gave true-negative results (P = 0.08, Mann-Whitney rank sum test, one tailed). Among strains positive for TSST-1, the level of TSST-1 detected in culture supernatants correlated inversely with the amount of protein A secreted (rs = -0.64; P less than 0.01, Spearman rank correlation). These findings validate the utility of a rapid screening method for the detection of TSST-1-producing S. aureus and support the concept of coordinate secretion of exoproteins in S. aureus.

Bacterial Toxins↗
PubMed1988

Synergistic interactions of ciprofloxacin and extended spectrum beta-lactams or aminoglycosides against Acinetobacter calcoaceticus ss. anitratus.

The susceptibility of 54 clinical isolates of Acinetobacter calcoaceticus ss. anitratus to 16 antimicrobial agents was determined in vitro with inoculum of 10(4) and 10(6) cfu by a standard agar dilution method. The most active agents were imipenem, SCH 34343, ciprofloxacin, difloxacin (A-56619), and A-56620. Only imipenem and Abbott quinolones (A-56619 and A-56620) remained active when tested with the heavier inoculum. Except for ticarcillin and ceftazidime, which showed only moderate activity, the extended-spectrum penicillins and cephalosporins, as well as aztreonam and aminoglycosides, were inactive against these highly resistant strains. Nine isolates were selected for combination studies of ciprofloxacin with seven beta-lactams and three aminoglycosides using a checkerboard agar dilution technique. Synergistic or additive interactions at clinically achievable concentrations were more common with amikacin (eight isolates), tobramycin (seven), ceftazidime (six), cefoperazone (six), and aztreonam (six), than with other agents, including mezlocillin (four), piperacillin (three), gentamicin (two), and cefsulodin (two). Antagonism was rare, only occurring with mezlocillin in a single strain. These data suggest that combinations of ciprofloxacin with these agents may be useful for some nosocomial multidrug resistant A. calcoaceticus ss. anitratus infections.

Acinetobacter↗
PubMed1988

Synergistic interactions of ciprofloxacin and extended-spectrum beta-lactams or aminoglycosides against multiply drug-resistant Pseudomonas maltophilia.

The susceptibility of 28 clinical isolates of Pseudomonas maltophilia to 16 antimicrobial agents was determined in vitro by a standard agar dilution method with inoculum sizes of 10(4) and 10(6) CFU. All isolates exhibited multiple drug resistance. Nine isolates were selected for studies of combinations of ciprofloxacin with seven antipseudomonal beta-lactams and three aminoglycosides by a checkerboard agar dilution technique. Synergistic or additive combinations of ciprofloxacin in clinically achievable concentrations were most frequent with mezlocillin (89%), followed by cefoperazone (67%), piperacillin (56%), cefsulodin (56%), and ceftazidime (33%), and were infrequent with aztreonam (11%), the aminoglycosides (0 to 14%), or imipenem (0%). Antagonism was not observed in any combination. These data suggest that combinations of ciprofloxacin with these agents may be useful for some nosocomial multiply drug-resistant P. maltophilia infections.

Aminoglycosides↗
PubMed1988

In vitro activities of daptomycin (LY146032) and paldimycin (U-70,138F) against anaerobic gram-positive bacteria.

The in vitro activities of daptomycin (LY146032), paldimycin (U-70,138F), vancomycin, and penicillin G against 344 clinical isolates of anaerobic gram-positive bacteria were determined by an agar dilution method in calcium-supplemented (50 micrograms/ml) Wilkins-Chalgren medium, using an inoculum of 10(5) CFU. Daptomycin demonstrated excellent activity against a broad range of anaerobic gram-positive cocci and bacilli, including Peptostreptococcus, Eubacterium, Bifidobacterium, Actinomyces, Propionibacterium, and Lactobacillus species and Clostridium difficile. Highly resistant strains (MIC, greater than or equal to 64 micrograms/ml) were encountered sporadically from different genera, but these accounted for only 3% of all isolates tested. Vancomycin showed similar activity but was less active against Lactobacillus species and Peptostreptococcus prevotii. Paldimycin was inactive against most genera of anaerobic gram-positive bacteria. Overall, penicillin G remained the most broadly active agent against these isolates.

Acetylcysteine↗
PubMed1988

Drug usage review of cefamandole at a teaching hospital.

A drug usage audit of cefamandole was conducted at a 900-bed teaching hospital. Health records of all in-patients receiving cefamandole during a three-month period (November 1, 1985 to January 31, 1986) were retrospectively reviewed. Treatment of lower respiratory tract infections accounted for 35 (44%) of the 79 treatment courses examined. Surgical antimicrobial prophylaxis for cardiovascular procedures involved 26 (33%) courses of therapy and 15 (19%) courses were associated with biliary tract procedures. The three remaining treatment courses (4%) included therapy for septicemia, orthopedic surgery prophylaxis, and a leg ulcer. Twenty-eight percent of all treatment courses were deemed to be appropriate. Thirty-two percent were considered controversial, and 40 percent inappropriate. The majority of the suboptimal use identified involved prescribing cefamandole for cardiovascular surgery prophylaxis. The role of cefamandole in the acute hospital setting is reviewed with reference to other available first, second and third-generation cephalosporins. General recommendations for its use are outlined.

Anti-Bacterial Agents↗
PubMed1988

Normal flora and mucosal immunity of the head and neck.

The study of the human resident flora has grown from Antony van Leeuwenhoek's simple descriptions some 300 years ago to the sophisticated investigations being done today. The acquisition of organisms and the subsequent course of either stable colonization or invasion of the host involve complex host-parasite interactions. From one perspective, clearly host factors are operative that appear to select against certain species while being permissive for others. From another perspective, microbial species that are successful at colonization must overcome certain host factors to maintain a selective advantage and flourish within a particular body habitat. It is intriguing that whereas host mucosal defenses are a significant influence contributing to selection of the resident flora, it is this established flora that provides the host with perhaps its most important local defense system. In the head and neck areas, many of these mucosal surfaces are contiguous and thus for the most part share a common resident flora. These organisms are rarely involved in infection unless some breach of the mucosal surface or some upset in the balance of the normal flora occurs. On these occasions, the host is susceptible to infection from both newly acquired organisms and those previously present, which may now become invasive. In any event, it is clear that improved knowledge of the normal flora of the head and neck is essential for understanding and for effective treatment of infectious processes in this area. It is hoped that a better appreciation of the important role of the normal flora in maintaining the host mucosal defenses will further focus our attention on its preservation.

Head↗
PubMed1988

The tender tooth. Dentoalveolar, pericoronal, and periodontal infections.

Dental caries and periodontal disease are the most common afflictions of the tooth. These infectious diseases cause considerable pain and discomfort and ultimately loss of the tooth. Apart from local effects, these infections may extend beyond natural barriers and result in complications that can vary in severity from the excruciating pain of acute pulpitis to life-threatening infections of the deep fascial spaces of the head and neck. In this article, the clinical and pathologic features of dental caries, pulpitis, periapical abscess, pericoronitis, and periodontal infections are discussed as well as prevention and treatment of infections involving the tooth, with emphasis on endocarditis prophylaxis.

Child↗
PubMed1988

Serologic responses to toxic shock syndrome (TSS) toxin-1 in menstrual and nonmenstrual TSS.

Toxic shock syndrome toxin-1 (TSST-1) is implicated as the major exotoxin associated with menstrual toxic shock syndrome. The role of TSST-1 in nonmenstrual TSS is less certain. We examined serum IgG responses to TSST-1 in 16 nonmenstrual (9 female, 7 male) and 14 menstrual TSS patients, and in 87 women and 66 men as age-matched healthy controls, using an enzyme-linked immunosorbent assay (ELISA). Relative ELISA titers were expressed as percent activity of a mid level serum standard tested concurrently. Based on 95% confidence estimates for predicting a negative titer (20.6 +/- 8.2%) using sera in which TSST-1 specific IgG was demonstrated to be absent by western blot, 24% of control women and 9% of control men lacked TSST-1 specific IgG in the random survey (p less than 0.05, Fisher's exact test). Relative titers in acute sera of menstrual TSS women (26.2 +/- 5.2%, mean +/- S.E.), but not nonmenstrual TSS women (71.8 +/- 18.6%), were significantly lower than those of control women (78.9 +/- 7.3%, p less than 0.01, Mann-Whitney test). Acute titers from male TSS patients (37.0 +/- 15.6%) were also significantly lower than those in control men (114.6 +/- 11.0% (p less than 0.05). Antibody titers from menstrual TSS women and TSS men remained low during convalescence. Nevertheless, seroconversion to TSST-1 was demonstrated by western blot in 7 of 10 patients in whom TSST-1 positive S. aureus was isolated, but in neither of two patients without toxigenic S. aureus.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Clinical and microbiologic risk evaluation for post-cesarean section endometritis by multivariate discriminant analysis: role of intraoperative mycoplasma, aerobes, and anaerobes.

The clinical and microbiologic risk factors for postpartum endometritis were studied prospectively in 77 patients undergoing cesarean section without antibiotic prophylaxis at Harbor-University of California at Los Angeles Medical Center. Intraoperative cultures were obtained from the amniotic fluid, lower uterine segment, and abdominal wound for isolation of genital mycoplasmas, aerobes, and anaerobes. Postsection endometritis developed in 21 (27%) patients and was significantly associated with presence of either high-virulence bacteria (predominantly, coliforms, streptococci, anaerobic cocci, and bacteroides) (35% to 60% versus 10% to 24%; p less than 0.05) or Ureaplasma urealyticum (15% to 42% versus 0% to 10%; p less than 0.05) at any site compared with afebrile women. Multivariate analysis identified primary cesarean section, younger maternal age, presence of ruptured membranes, and presence of Ureaplasma as significant risk factors independent of other confounding variables (p less than 0.01). It is suggested that genital mycoplasmas could play a primary role in some cases of postsection endometritis or that they are cofactors or markers for the presence of other high-virulence aerobic and anaerobic bacteria.

Anti-Bacterial Agents↗
PubMed1987

Interactions of ciprofloxacin with clindamycin, metronidazole, cefoxitin, cefotaxime, and mezlocillin against gram-positive and gram-negative anaerobic bacteria.

A total of 598 clinical isolates of anaerobic bacteria were tested against ciprofloxacin by the agar dilution technique with 10(5) CFU on Wilkins-Chalgren medium. Selected strains representative of the six major genera of anaerobes relatively resistant to the quinolones were tested for interactions with ciprofloxacin in combination with clindamycin, metronidazole, cefoxitin, cefotaxime, or mezlocillin by using a checkerboard agar dilution technique. Cefotaxime-ciprofloxacin and clindamycin-ciprofloxacin were the most effective combinations, with 16% of all isolates and 44% of the Bacteroides fragilis group isolates responding synergistically to the former combination and 9% of all isolates and 37% of Peptostreptococcus isolates responding synergistically to the latter. Occasional synergy was seen with all other antibiotic combinations except for metronidazole-ciprofloxacin. Likewise, synergism was seen with all groups of anaerobes except for Fusobacterium species. Antagonistic interactions were observed only with a Peptostreptococcus intermedius strain tested against clindamycin-ciprofloxacin. These data suggest that combinations of ciprofloxacin with these agents may be useful for certain resistant anaerobic infections.

Bacteria, Anaerobic↗
PubMed1987

Detection and quantitation of toxic shock syndrome toxin 1 in vitro and in vivo by noncompetitive enzyme-linked immunosorbent assay.

Toxic shock syndrome toxin 1 (TSST-1), an exotoxin produced by many Staphylococcus aureus strains, is implicated as the prime causal agent of toxic shock syndrome (TSS). A sensitive and specific noncompetitive enzyme-linked immunosorbent assay (ELISA) capable of detecting TSST-1 at concentrations from 0.5 to 16 ng/ml was developed. This assay did not detect other staphylococcal enterotoxins including A, B, C1, C2, C3, D, and E. Possible interactions with protein A were readily eliminated by pretreatment of test samples with 10% normal rabbit serum. The assay was adapted for rapid screening of TSST-1 production by S. aureus isolates in culture supernatants in vitro and for detection of TSST-1 in vaginal washings of TSS patients and healthy controls in vivo. All 35 S. aureus isolates confirmed to be TSST positive by Ouchterlony immunodiffusion and 59 of 60 isolates confirmed to be TSST-1 negative gave concordant results by ELISA. Interestingly, toxigenic S. aureus strains isolated from TSS patients quantitatively produced significantly more TSST-1 in vitro compared with toxigenic control strains (P less than 0.05, Mann-Whitney rank sum test). TSST-1 could be detected by ELISA in three of four vaginal washings collected within 3 days of hospitalization from three women with acute menstrual TSS, compared with 0 of 17 washings from nine TSS patients hospitalized longer than 3 days (P = 0.003, Fisher's exact test) and 1 of 15 washings from 14 healthy control women (P = 0.016). This noncompetitive ELISA should be particularly useful for rapid screening of TSST-1 production by S. aureus isolates, for the purification and biochemical characterization of TSST-1, and for human and animal studies of the pathogenesis of TSS.

Bacterial Toxins↗
PubMed1986

Vaginal colonization with Escherichia coli in healthy women. Determination of relative risks by quantitative culture and multivariate statistical analysis.

The rate of vaginal colonization with Escherichia coli in 495 healthy women was 12% in a prospective study with use of selective media and semiquantitative culture techniques. Computer-assisted multivariate analysis revealed that vaginal E. coli was significantly associated with the menstrual phase of the cycle, prior use of antibiotics, use of diaphragm or cervical cap for contraception, history of previous urinary tract infection, and coisolation of Staphylococcus aureus that was positive for the toxic shock syndrome toxin-1 (p less than 0.05, multiple stepwise logistic regression analysis). No significant association was observed with tampon use or brand, other contraceptive methods, sexual activity, genital symptoms, recent vaginal infection, or other personal habits. Quantitative cultures obtained sequentially throughout the menstrual cycle in 12 unselected women confirmed higher E. coli counts in menstrual or midcycle samples compared to paired premenstrual specimens (p less than 0.05, Wilcoxon paired rank sign test). These data emphasize the hormonal and other host determinants in vaginal colonization by E. coli and may explain the high rate of vaginal E. coli (64%), in addition to toxicogenic S. aureus, in acute toxic shock syndrome and the higher incidence of urinary tract infection in women with diaphragm or cervical cap for contraception compared to other contraceptive methods.

Adult↗
PubMed1986

Comparison of susceptibility of gentamicin-resistant and -susceptible "Acinetobacter anitratus" to 15 alternative antibiotics.

Fifty-four clinical isolates of "Acinetobacter anitratus" separated cleanly into gentamicin-susceptible (16 strains) and gentamicin-resistant (38 strains) subpopulations. When tested with a 10(4)-CFU inoculum, gentamicin resistance was associated with a greater than fourfold increase in the MICs of norfloxacin, ciprofloxacin, A-56620, tobramycin, and amikacin for 50% of the strains. Antimicrobial agents with MICs for 90% of gentamicin-resistant strains in the susceptible range were ciprofloxacin, A-56619, A-56620, imipenem, SCH-34343, ceftazidime, aztreonam, carbenicillin, ticarcillin, and piperacillin. These agents may be useful alternative drugs for treating infections caused by aminoglycoside-susceptible and -resistant "A. anitratus."

Acinetobacter↗