Aerobic Gram-positive Cocci Research Articles

Aztreonam

Aztreonam, the first commercially available monobactam, has a wide range of activity against aerobic gram-negative bacilli. It can be administered two to three hours daily because its half-life is 1.6 to 2 hours. Excellent blood and tissue concentrations are attained. The MIC of aztreonam against most Enterobacteriaceae is less than or equal to 2 micrograms/ml and against P aeruginosa less than or equal to 16 micrograms g/ml. Aztreonam has been used in a wide array of infections of the urinary tract and respiratory tract, blood, intra-abdominal and gynecologic infections and infections of the skin, bones and joints. As empiric therapy, aztreonam is usually combined with another antimicrobial agent active against anaerobes and/or aerobic gram-positive cocci until culture results are available. One exception is empiric therapy for gram-negative urinary tract infections in which aztreonam can be used initially as monotherapy against susceptible gram-negative pathogens. In general, the efficacy of aztreonam is equal or superior to that of the aminoglycosides. Adverse reactions to aztreonam are unusual, and it as been shown to be a poor hapten, permitting its administration to patients with proven allergy to the penicillins and cephalosporins. Aztreonam is a useful addition to the available antibiotics for treatment of gram-negative infections.

The clinical development of mupirocin

Mupirocin is a novel antibiotic totally unrelated in chemical structure and mode of action to any other clinically useful class of antibiotics. It has greatest antibacterial activity against aerobic gram-positive cocci, namely, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, and other beta-hemolytic streptococci. Bactroban ointment is formulated as 2% mupirocin in polyethylene glycol ointment. No systemic absorption of mupirocin or its major metabolite, monic acid, has been detected in short courses of topical administration to healthy volunteers or to patients with epidermolysis bullosa after prolonged courses of therapy with Bactroban ointment. Randomized, multicenter, double-blind, vehicle-controlled clinical trials have shown that mupirocin is safe and effective for the treatment of impetigo.

Outpatient Management of Uncomplicated Lower-Extremity Infections in Diabetic Patients

Most diabetic foot infections are believed to be caused by both aerobic and anaerobic bacteria and to require hospitalization and parenteral antimicrobial therapy. We prospectively evaluated diabetic patients with non-limb-threatening lower-extremity infections not yet treated with antibiotics. The patients were randomized to outpatient treatment with oral clindamycin hydrochloride or cephalexin for 2 weeks and evaluated every 3 to 7 days. In 56 assessable patients, curettage yielded a mean of 2.1 microorganisms. Aerobic gram-positive cocci were isolated in 50 cases (89%), and were the sole pathogen in 21 (42%) of these. Aerobic gram-negative bacilli and anaerobes were isolated in 20 (36%) and 7 (13%) cases, respectively, and almost always in polymicrobial infections. Fifty-one infections (91%) were eradicated, 42 (75%) after 2 weeks of treatment; only 5 (9%) were initially treatment failures, and 3 (5%) were subsequently cured with further outpatient oral antibiotic treatment. After a mean follow-up of 15 months, no further treatment was required in 43 (84%) of the cured patients. Previously untreated lower-extremity infections in diabetic patients are usually caused by aerobic gram-positive cocci, and generally respond well to outpatient management with oral antibiotic therapy.

Aztreonam susceptibility testing: A retrospective analysis

Aztreonam is a structurally and immunologically unique beta-lactam antibiotic with activity exclusively against aerobic gram-negative micro-organisms. Between 1983 and 1988, its antimicrobiol spectrum was evaluated against more than 5,800 fresh clinical isolates at a 300-bed community teaching hospital. Only 1.1 percent of Enterobacteriaceae isolates were resistant to aztreonam over the five-year study period, an incidence similar to that observed with aminoglycoside antibiotics. Aztreonam was found to be more active than third-generation cephalosporins and comparable with mezlocillin against Enterobacter spp., Morganella, and Citrobacter freundii. Although aztreonam was somewhat less active against nonfermenting gram-negative bacilli, such as Pseudomonas and Acinetobacter, overall more than 90 percent of Pseudomonas aeruginosa isolates were susceptible. Ceftazidime was the most active beta-lactam tested against nonfermenters. Against aerobic gram-positive cocci, aztreonam possessed no clinically useful activity. No significant change in susceptibility to aztreonam was observed over the five-year study period for Enterobacteriaceae. For third-generation cephalosporins, however, a trend toward increased resistance was noted, particularly for Enterobacter spp. and C. freundii. A 50 percent increase in resistance to aztreonam was observed over the five-year study period for nonfermenters, particularly P. aeruginosa and Acinetobacter anitratus. Similar increases in resistance were seen with other beta-lactams and gentamicin. Based on its potent in vitro activity, aztreonam appears to be a useful agent and a desirable alternative to aminoglycoside antibiotics for the treatment of pure aerobic gram-negative bacillary infections, or as a component in combination therapy against mixed infections.

A comparison of oxoid signal with nonradiometric BACTEC NR-660 for detection of bacteremia

The Oxoid Signal (Oxoid U.S.A. Inc., Columbia, Maryland) system was compared with the nonradiometric BACTEC NR-660 (Johnston Laboratories, Towson, Maryland) system for detection of bacteria in 2714 blood cultures. The volume of blood collected into 20 ml blood-collection tubes containing sodium polyanetholsulfonate (SPS) (Becton Dickinson, Vacutainer Systems, Rutherford, New Jersey) ranged from 10 to 20 ml with an average of 15 ml. Subsequently, equal volumes of blood were inoculated into each system. A total of 250 organisms was isolated (9.6%), of which 149 (5.5%) were considered significant while 111 isolates from 98 cultures (3.6%) were contaminants. Of the significant isolates 32.9% were aerobic Gram-negative rods, 53.0% aerobic Gram-positive cocci, 5.4% anaerobes, 7.4% yeasts, and two isolates of Neisseria meningitidis. Ninety-five isolates were recovered in both systems, 29 by Bactec only and 25 by Signal only. Of the isolates recovered there were no significant differences in detection between the two systems with the exception of anaerobes (P < 0.005). The median detection times for many of the msot commonly isolated organisms— Enterobacteriaceae, streptococci, and Staphylococcus aureus—were very similar in both systems, ranging from 14 to 21 hours. With the remaining organisms recovered, the median times in hours for BACTEC and Signal, respectively, were 31 and 47 for Staphylococcus epidermidis, 48 and 60 for Bacteroides, 39 and 168 for yeast, and 16.5 and 168 for N. meningitidis. Oxoid Signal compares favorably with the BACTEC system. Its main advantages are: (1) it requires no instrumentation; (2) it is characterized by ease of detection; and (3) it uses a single-bottle system. The major disadvantages are: (1) it is perhaps unable to detect certain anaerobes; and (2) it requires terminal subculture at this time.

The contribution of Escherichia coli to microbial colonization resistance

The contribution of Escherichia coli to the microbial colonization resistance (CR) of the bowel was investigated in six healthy volunteers. Esch. coli was eliminated from faeces by the administration of a low dose (20 mg daily) of pefloxacin. This did not cause an increase in the faecal concentration of aerobic Gram-positive cocci or yeasts, nor did it facilitate colonization of the bowel by a pefloxacin-resistant challenge strain of Klebsiella pneumoniae. Therefore, Esch. coli does not appear to contribute to the microbial CR. After ten days of pefloxacin, clindamycin 300 mg was administered twice daily for 18 days. Clindamycin caused a significant increase in the faecal concentration of enterococci, yeasts and the K. pneumoniae challenge strain, indicating that the study design was suitable to demonstrate disturbance of microbial CR if it occurred.

Role of aerobic gram-negative rods, anaerobes, and fungi in wound infection after head and neck surgery: implications for antibiotic prophylaxis.

The prevention of wound infection after major contaminated head and neck surgery is a critical issue for the head and neck surgeon. The proper interpretation of cultures taken from wounds is uncertain. Multiple organisms are invariably isolated from this nonsterile site including indigenous aerobic and anaerobic flora, aerobic gram-negative rods, and fungi. We present evidence from controlled antibiotic trials that demonstrate the pathogenicity of oropharyngeal anaerobic flora. The presence of aerobic gram-negative rods and fungi generally represent colonization and antibiotic coverage need not routinely be directed at these organisms. On the other hand, the antibacterial spectrum of an agent used for head and neck would prophylaxis should include coverage for pathogenic oral flora, namely the gram-positive aerobic cocci (especially streptococci) and anaerobic bacteria.

Effects of the growth medium composition on menaquinone homolog formation in Micrococcus luteus.

The menaquinone composition of Micrococcus luteus strains grown in different media was examined. Cells of M. luteus IAM 1056 (type strain) grown in an ordinary complex medium contained MK-8 as the predominant menaquinone. On the other hand, this bacterium produced both MK-8 and MK-8(H2) as major quinones when grown in a chemically defined medium containing glutamate and pyruvate as carbon sources. Unlike the type strain, M. luteus strains IAM 12009 and IAM 12144 had MK-8 (H2) as the major menaquinone, independent of cell growth media. In all strains the total amount of dihydrogenated homologs relative to the total menaquinone content increased more or less in cells grown in the chemically defined medium. Carbon sources and Mgt + concentrations in the growth medium had minor effects on the menaquinone composition of the M. luteus strains. It is now recognized that the analysis of isoprenoid quinones involved in electron transport in the respiratory chain of bacteria provides invaluable criteria for their taxonomy (1, 2,11). Earlier work of Jeffries and associates (7,8) on the menaquinone composition of some aerobic gram-positive cocci was the first to demonstrate the value of respiratory quinones in microbial systematics. They reported that most strains of Micrococcus luteus contained dihydrogenated menaquinones with eight isoprene units (MK-8(H2)) as major isoprenoid quinones, while the strain now designated as the type strain of this species had MK-8 as the major type with significant proportions of MK-8(H2) and the next lower and higher homologs . Similar results were obtained by Yamada et al. (12). Later , Fujii et al. (3) found

In vivo postantibiotic effect in a thigh infection in neutropenic mice.

The postantibiotic effect (PAE) is the suppression of bacterial growth that persists after limited exposure of organisms to antimicrobial agents. We demonstrated and standardized the in vivo PAE in a thigh infection model in neutropenic mice. Inhibitors of protein and nucleic acid synthesis induced PAEs of 1.4-7.5 h against aerobic gram-negative bacilli, whereas beta-lactam antibiotics did not induce significant PAEs. Against aerobic gram-positive cocci, cell wall-active agents and inhibitors of protein and nucleic acid synthesis induced PAEs of 1.2-7.1 h, except for penicillins, which did not induce PAEs against streptococci. With few exceptions the in vivo PAE correlated well with the PAE reported in prior in vitro studies. Residual drug in thigh tissue did not cause the PAE. Theoretically, the presence of a PAE may allow antimicrobial agents to be given more intermittently without organism regrowth after drug levels fall below the minimal inhibitory concentration.

4-Quinolones in the treatment of infections of the central nervous system.

The literature concerning the penetration of new 4-quinolones into the cerebrospinal fluid (CSF) and brain tissue is reviewed as well as the few reports on clinical use of these antibiotics in the treatment of infections of the central nervous system (CNS). Pefloxacin has been found to penetrate well into the CSF of patients with normal or inflamed meninges as well as into brain tissue. Ciprofloxacin also penetrates into CSF, although not as well as pefloxacin. Two patients with meningitis due to Pseudomonas aeruginosa have been reported to have recovered after treatment with ciprofloxacin. Because of the spectrum limitations of quinolones, especially with regard to anaerobes and gram-positive aerobic cocci, these agents should not be considered for empiric use in CNS infections. They may, however, become alternatives in the rare cases of CNS infection caused by organisms resistant to other antibiotics.

Selective decontamination of the digestive tract and fungal infection in acute leukemia patients.

For prevention of infection we used an SD design including antibacterial (trimethoprim 480 mg/daily, sulfamerazine 720 mg/daily, and polymyxin 0.25 mg/daily) and antifungal (4-6 million IU nystatin/daily) components. We analyzed retrospectively 138 treatment periods in 108 patients. The intensified chemotherapy resulted in severe granulocytopenia below 0.1 x 10(9)/liter over 25.2 days. In 19 patients there was suspicion of major fungal infection; therefore they were given amphotericin B and 5-fluocytosine. Fourteen of them died; major fungal infections were documented in 5 cases. In 18% of all the deceased we found major fungal infections. There was a correlation between fungal infection, the late stages of the hematological malignancy, and the lesions on the oropharyngeal mucosa. However, in terms of the serological and culture findings no correlation appeared to exist between the group with and the group without fungal infection. The SD regime is meant to suppress the Candida cell concentration in the digestive tract but has no influence on Aspergillus in the respiratory tract.

Haemostasis during treatment with ciprofloxacin.

The effects of ciprofloxacin, a new quinolone derivative with high activity on gram-negative aerobic bacteria and gram-positive cocci, on haemostasis were investigated in 11 healthy volunteers. No influence on platelet function was detectable. In some cases a slight reduction in antithrombin III activity was observed at the end of the therapy. No other changes were evident in the plasma coagulation parameters.

Does the hygroscopic property of the laminaria tent imply a risk for ascending infection in legal abortions? A microbiological study.

In 53 women admitted for first-trimester abortion, the cervical canal was dilated with laminaria tents prior to vacuum aspiration. Before insertion of the tents, endocervical specimens were taken for microbiological investigations, including Chlamydia trachomatis, and both aerobic and anaerobic microorganisms. The laminaria tents, widened by their hygroscopic properties, were removed just before the vacuum aspiration and sent for cultivation of aerobic and anaerobic microorganisms. The Gram-positive aerobic cocci, Staph. epidermidis, Strept. faecalis and Strept. agalactiae as well as Escherichia coli and Klebsiella/Enterobacter were the most frequent microorganism among the aerobic isolates from the endocervices as well as from the laminaria tents. These microorganisms were identified on the tents in greater numbers than in the cervices. Staph. aureus was isolated from three laminaria tents, but only one of these 3 women was proved to be primarily colonized endocervically. Among the anaerobes, Bacteroidaceae followed by peptococci and peptostreptococci were the predominant genera found in the cervix as well as on the removed laminaria tents. These three groups of anaerobic microorganisms were found markedly less frequently on the laminaria tents than in the endocervix. On the other hand, Strept. intermedius, another anaerobe of possible enteric origin, was recovered from 9 laminaria tents but not in the cervices. Since no cases of clinically verified endometritis/salpingitis were registered in the present study it is concluded that the risk of a pelvic inflammatory disease (PID) due to the laminaria tent is negligible as long as the laminaria treatment does not exceed 24 hours.

Midecamycin acetate-susceptibility of clinical isolates from dental and oral surgical infections

To investigate the clinical and bacteriological usefulness of orally administered midecamycin acetate (MOM), the susceptibility of clinical isolates to MOM, Mb-12 (the main metabolite of MOM), josamycin (JM), ampicillin (ABPC) and cephalexin (CEX) was determined. The results are summarized as follows. Antibacterial activities of MOM against aerobic Gram-positive cocci, B. catarrhalis, and anaerobic bacteria were inferior to those of JM by 2-fold, but superior to those of CEX. Activities of MOM against S. aureus, Bacteroides spp., Fusobacterium spp., Veillonella spp. were superior to those of ABPC and CEX. Since serum and tissue concentrations of Mb-12 after 200 mg administration in humans have been reported to be 1-2 micrograms/ml, it can be presumed that the causative bacteria would be eradicated by a usual dosage of MOM used in the present study. From these considerations, it is speculated that MOM may be successfully used in the treatment of dental and oral surgical infections.

In vitro antibacterial activity of SK&amp;F 88070 against aerobic gram-positive and gram-negative cocci and Haemophilus influenzae

The inhibitory activity of SK&F 88070, a cephalosporin whose kinetic characteristics in animals suggest the possibility of once-daily doses, was determined against 345 clinical isolates, and results were compared with the activities of ceftizoxime, ceftriaxone, moxalactam, methicillin, and ampicillin. The spectrum of SK&F 88070 is similar to that of ceftizoxime.

Ceftazidime Review

The chemistry, in vitro activity, adverse effects, and clinical indications for the new third-generation cephalosporin, ceftazidime, are reviewed. Ceftazidime appears to have a unique place among the third-generation agents in the treatment of some infectious processes caused by Pseudomonas aeruginosa. It does not demonstrate superiority to other third-generation drugs against Enterobacteriaceae, aerobic gram-positive cocci, or anaerobes. It is eliminated renally and is similar to ceftizoxime, cefoperazone, and moxalactam in half-life. Ceftazidime shares the safety profile of most of the cephalosporins, and has not been shown to have an effect on prothrombin or produce the disulfuram reaction seen with moxalactam and cefoperazone. Specific indications for its use are discussed.

Role of imipenem/cilastatin in the treatment of soft tissue infections

Imipenem/cilastatin was given to 243 evaluable patients with moderately severe to severe soft tissue infections. Cultures prior to therapy yielded Staphylococcus aureus (108 isolates), group D and non-group D enterococci (49), group A streptococci (42), other aerobic gram-positive cocci (72), Pseudomonas aeruginosa (54), Escherichia coil (32), Proteus mirabilis (31), Enterobacter (21), Klebsiella (20), other aerobic gram-negative rods (58), Bacteroides fragilis group (16), and other anaerobes (65). Overall, 95 percent (230 of 243) of the patients treated had clinical cure (137 of 243) or improvement (93 of 243). Of the 506 strains of etiologic bacterial pathogens isolated from these patients and tested against imipenem, 498 (98 percent) were susceptible to the antibiotic. Many were resistant to both older and newer penicillins and cephalosporins. Serial cultures of infection sites revealed that 426 of 498 (86 percent) of pre-therapy bacterial isolates were eradicated by imipenem/cilastatin therapy. Eight of 498 etiologic pathogens (1.6 percent) acquired resistance to imipenem (seven P. aeruginosa and one enterococcus). Such resistance acquisition was associated with clinical failure in two patients. Imipenem/cilastatin appears to be a highly effective, relatively safe therapy of soft tissue infections caused by a wide variety of gram-positive and gram-negative aerobes and anaerobes, both polymicrobial and monomicrobial in nature. Imipenem/cilastatin should be considered particularly when infection by the more antibiotic-resistant of these bacteria is suspected or proved.

Intestinal Flora in the Second Week of Life in Hospitalized Preterm Infants Fed Stored Frozen Breast Milk or a Proprietary Formula

Twenty infants fed stored frozen breast milk or a proprietary formula only had both aerobic and anaerobic cultures performed at a chronologic age of 8 to 14 days. Nine out of 10 stools from the infants fed stored frozen breast milk contained Enterobacteriaceae and one stool was sterile. One contained a Pseudomonas species; one contained anaerobic gram-positive rods; one contained anaerobic gram-negative rods; and four contained anaerobic gram-positive cocci. No anaerobes were found in six stools. Six stools had aerobic gram-positive cocci, none of which was hemolytic. Nine out of 10 stools from infants fed a proprietary formula had Enterobacteriaceae. Six stools had anaerobic gram-positive rods, three had anaerobic gram-negative rods, and four had gram-positive cocci. Four stools had no anaerobic bacteria. All 10 stools had nonhemolytic aerobic gram-positive cocci. Enterobacteriaceae were predominant in the stools of the infants fed either stored frozen breast milk or a proprietary formula, and the colony counts of aerobic bacteria were similar in both groups. This pattern of intestinal flora in hospitalized preterm infants in the second week of life is very different from that of normal term infants and may contribute to their increased incidence of systemic and localized infections. The use of stored frozen breast milk for the purpose of suppressing coliform and other potentially pathogenic organisms may not be effective in hospitalized preterm infants who have been treated previously with broad-spectrum, parenteral antibiotics.

Progression of Group A Streptococcal Necrotizing Fasciitis During Moxalactam Therapy

To the Editor. —Third-generation cephalosporins have an expanded spectrum of activity against aerobic gram-negative bacilli. The decreased activity of these compounds against aerobic gram-positive cocci has received less emphasis. 1 The following case illustrates the rapid progression of group A streptococcal infection during moxalactam therapy. Report of a Case. —A pruritic infection in the inguinal area, which was clinically consistent with tinea cruris, developed in a 67-year-old man. Despite pruritus, no treatment was instituted. Ten days later, there was the dramatic onset of chills and fever with pain, erythema and induration in the skin parallel to the inguinal ligament and over the right greater trochanter. The patient was admitted to the hospital, blood cultures were obtained, and empiric therapy with moxalactam disodium was begun in a dosage of 2 g intravenously every eight hours. Sixteen hours later, the involved area had roughly doubled in size, and the moxalactam therapy was

Interaction of clindamycin and cefpimizole (U63196E) in vitro against aerobic gram-negative rods and aerobic gram-positive cocci.

The combination of clindamycin plus a new semisynthetic cephalosporin, U63196E for which the United States approved name is cefpimizole, was tested against 47 aerobic Gram-negative rods and 30 aerobic Gram-positive cocci. Synergy was seen with Klebsiella pneumoniae (3 of 19 isolates) and Escherichia coli (2 of 21 isolates). All isolates of Pseudomonas aeruginosa, Staphylococcus aureus, methicillin-resistant Staph. aureus, and enterococci demonstrated either indifference or antagonistic reactions to the drug combination.