New insights into the activity of third-generation cephalosporins against pneumonia-causing bacteria

Probing the interaction of cephalosporin antibiotic "cefoperazone" with lysozyme using spectroscopic and in silico methods: Effect of paracetamol on binding

The interaction of lysozyme with cefoperazone was studied by means of spectroscopic and computational approaches. The change in the UV-visible spectrum of lysozyme in presence of cefoperazone was an indication of the complex formation between them. Fluorescence spectroscopy suggested that there was a fair interaction between the protein and drug which was taken place via dynamic quenching mechanism and the binding ratio was approximately 1:1. The binding was energetically feasible and principally supported by the hydrophobic forces. CD spectroscopic studies have shown that cefoperazone induced the secondary structure of lysozyme by increasing the α-helical contents of the latter. In silico studies revealed that the large nonpolar cavity was the preferred binding site of cefoperazone within lysozyme and the interaction was taken place mainly through hydrophobic forces with small involvement of hydrogen bonding and electrostatic interactions which is in good agreement with the experimental analyses. Effect of paracetamol was also seen on the binding and it was found that paracetamol had a negative influence on the binding between cefoperazone and lysozyme.

Rationale for eliminating Staphylococcus breakpoints for β-lactam agents other than penicillin, oxacillin or cefoxitin, and ceftaroline

Due to the ongoing concern about the reliability of Staphylococcus breakpoints (interpretive criteria) for other β-lactam agents, the Clinical and Laboratory Standards Institute recently approved the elimination of all breakpoints for antistaphylococcal β-lactams except for penicillin, oxacillin or cefoxitin, and ceftaroline. Routine testing of penicillin and oxacillin or cefoxitin should be used to infer susceptibility for all β-lactams with approved clinical indications for staphylococcal infections. It is critical for laboratories to reject requests for susceptibility testing of other β-lactams against staphylococci and to indicate that susceptibility to these agents can be predicted from the penicillin and oxacillin or cefoxitin results. This article reviews β-lactam resistance mechanisms in staphylococci, current antimicrobial susceptibility testing and reporting recommendations for β-lactams and staphylococci, and microbiologic data and clinical data supporting the elimination of staphylococcal breakpoints for other β-lactam agents.

American Society of Anesthesiologists classification of physical status as a predictor of wound infection

BACKGROUND

Wound infection occurs when bacterial contamination overcomes the hosts' defences against bacterial growth. Wound categories are a measurement of wound contamination. The American Society of Anesthesiologists (ASA) classification of physical status may be an effective indirect measurement of the hosts' defence against infection. This study examines the association between the ASA score of physical status and wound infection.

METHODS

A retrospective review of a prospective study of antibiotic prophylaxis was carried out. Patients with a documented ASA score who received optimal prophylactic antibiotics were included. The anaesthetist scored the ASA classification of physical status in theatre. Other risk factors for wound infection were also documented. Patients were assessed up to 30 days postoperatively.

RESULTS

Of 1013 patients there were 483 with a documented ASA score. One hundred and one may not have received optimal prophylaxis, leaving a database of 382 patients. There were 36 wound infections (9.4%). Both the ASA classification of physical status (P = 0.002) and the wound categories (P = 0.034) significantly predicted wound infection. The duration of surgery, patient's age, acuteness of surgery and the organ system being operated on did not predict wound infection. On logistic regression analysis the ASA score was the strongest predictor of wound infection.

CONCLUSION

When effective prophylactic antibiotics were used the ASA classification of physical status was the most significant predictor of wound infection.

A comparison of the prophylactic efficacy of ceftriaxone and cefotaxime in abdominal surgery

BACKGROUND

Although ceftriaxone (R) and cefotaxime (C) are highly effective antibiotics, few studies have directly compared their prophylactic efficacy.

METHODS

In a prospective, randomized, double blind study of 1,013 patients undergoing abdominal surgery, the prophylactic use of ceftriaxone and cefotaxime were compared. Intravenous cephalosporin, 1 g, was given at induction of anesthesia, with intravenous metronidazole, 500 mg, also being given for colorectal surgery.

RESULTS

The difference in wound infection (R 8%, C 12%, P <0.05) was due to appendicectomies not receiving metronidazole, (R 6%, C 18%, P <0.03) and was no longer present when these cases were excluded from analysis (R 8%, C 10%). Of note chest and urinary tract infection (R 6%, C 11%, P <0.02) and "any" infection (R 20%, C 27%, P <0.05) were reduced with ceftriaxone.

CONCLUSIONS

Both antibiotics provide comparable wound prophylaxis as long as metronidazole is added for colorectal and appendiceal surgery. Ceftriaxone may be more versatile having the additional apparent benefits of reducing other postoperative infections, being less dependent on metronidazole as an adjunct and providing a more effective prophylactic cover against Staphylococcus aureus.

Cefotaxime and desacetylcefotaxime antimicrobial interactions. The clinical relevance of enhanced activity: a review

This presentation reviews 15 years of in vitro, pharmacokinetic, and clinical data concerning the active metabolite of cefotaxime sodium, desacetylcefotaxime. This principle metabolite maintains an antimicrobial activity and spectrum superior to so-called "second-generation" cephalosporins, plus it has an extended serum elimination half-life. Furthermore, it penetrates well into various important body compartments. The metabolite enhances cefotaxime potency by additive or synergistic antimicrobial interactions that can significantly reduce cefotaxime minimum inhibitory concentrations (MICs) among oxacillin-susceptible staphylococci, Streptococcus species including pneumococci resistant to penicillin, anaerobes, enteric bacilli, Pseudomonas aeruginosa, and when tested in human serum, some enterococci. The high activity of cefotaxime alone and the contributions of desacetylcefotaxime to the drug's total antimicrobial value must be considered in reestablishing correct dosing of this "third-generation" cephalosporin. Physicians should use cefotaxime susceptibility tests to direct appropriate, cost-effective dosing and the selection of co-drugs when needed. Moreover, empiric cefotaxime regimen doses should also be reduced for some infections at sites where expected pathogen MICs remain low (< or = 2 micrograms/ml).

Retrospective analysis of the clinical and economic outcomes of twice-daily dosing of cefotaxime in a Canadian tertiary care institution

A retrospective analysis of the clinical and economic outcome of a regimen of cefotaxime 1 g given every 12 h was conducted following the introduction of an institutional policy recommending this new dosing strategy. Patients were identified from a log order entry in the pharmacy, and the medical records were reviewed using a standardized data collection form. Explicit criteria were applied for the indications for antimicrobial therapy, presence of infection, and outcome parameters. A total of 60 patients with a mean (+/- SD) age of 56.2 (+/- 17.8) years and a mean (+/- SD) length of stay of 20.75 (+/- 18.1) days were identified. Of these, 48 (80%) were found to have a clinically or microbiologically documented infection, and of the 42 patients who could be assessed accordingly to the criteria chosen, 37 (88%) had a favorable clinical response; 21 patients (35%) received cefotaxime alone. The costs for administration of cefotaxime have decreased by approximately 30% since the introduction of this new dosing regimen.

Serotypes and resistance patterns of Streptococcus pneumoniae causing systemic disease in northern Norway

During the period 1985-1990, Streptococcus pneumoniae was isolated form 97 patients with systemic pneumococcal disease in Northern Norway. Systemic disease occurred most frequently in the age groups 0-4 years and > 60 years. An increasing incidence was observed, especially among children less than five years old. Serotypes covered by the 23-valent pneumococcal polysaccharide vaccine were found in 86 of 97 (88.7%) isolates. The vaccine did not cover 16.7% of the systemic isolates from children less than five years old. Reduced sensitivity to penicillin was found in one isolate (1.0%) which was resistant to ampicillin, doxycycline and chloramphenicol. The E-test and the Rosco agar diffusion test differed in sensitivity to penicillin, chloramphenicol, ciprofloxacin and erythromycin. Three serotype 12F strains showed unusual cross-resistance to chloramphenicol and erythromycin.

The antimicrobial activity of cefotaxime: comparative multinational hospital isolate surveys covering 15 years

The "third-generation" cephalosporins (3GC) have emerged as one of the most significant therapeutic entities in the last 15 years. These 3GC compounds (using cefotaxime as a model) have generally maintained their potency and spectrum of activity against important pathogens. However, the continuing popularity of this class associated with local, regional, or national-level use or abuse has led to efficacy reduction against some organism populations associated with selection of Class I cephalosporinase, stably derepressed mutants predominantly among Citrobacter and Enterobacter spp.; emergence of extended-spectrum beta-lactamase producing Enterobacteriaceae (usually Klebsiella spp.), as well as some isolates mimicking Class I-type resistance patterns; and lastly, altered PBP-mediated resistances among pneumococci, Haemophilus influenzae and pathogenic Neisseria spp. Some of these resistance patterns had been present prior to the clinical introduction of 3GCs and have only significantly threatened their use in the last 5 years. Prudent application of these 3GC drugs should be the goal for this decade as follows: 1) use as monotherapy at appropriate doses and frequencies only for organisms with low potential for mutational events; 2) use combination therapy routinely for organisms such as Citrobacter, Enterobacter, some indole-positive protease and Pseudomonas aeruginosa, to minimize emerging resistance clones; 3) use conservatively in high risk patients to minimize "super-colonization" by emerging problem bacteria (e.g. vancomycin-resistant enterococci, Xanthomonas maltophilia etc.); 4) use only those agents among 3GCs that have documented safety, broad clinical applications to all age groups, acceptable pharmacokinetic features and clear cost-saving potential; and 5) use in prophylaxis (surgical procedure, selective decontamination), should be focused toward single-dose or short-course regimens to reduce total hospital-wide exposure to broad-spectrum beta-lactam drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidemiologic typing of multiply drug-resistant Pseudomonas aeruginosa isolated from an outbreak in an intensive care unit

From June to August 1991, there was an outbreak of Pseudomonas aeruginosa infections in an intensive care unit in a general hospital in Sao Paulo, Brazil. We obtained 14 isolates from 14 patients, 11 from tracheal aspirate, and 3 from surgical wound exudates. These strains were typed by serotyping, pyocin typing, and pulsed-field electrophoresis (CHEF) of chromosomal DNA (chrDNA), and the different typing methods were analyzed. These three methods demonstrated seven identical strains. We also performed an extensive antibiogram (33 drugs) in all 14 isolates. The incidence of resistance to aminoglycosides, extended-spectrum beta-lactams, and quinolones was very high among the seven identical isolates; however, the antibiogram profile differed significantly among the isolates. Our results suggest that a unique strain caused several cross-transmitted infections during this period of time, and the emergence of antimicrobial resistance has been occurring before and after the establishment of the epidemic strain by selective drug use. The chrDNA fingerprinting proved to be versatile and precise for epidemiologic investigations of P. aeruginosa infections.

Pneumonia. Patient profiles, choice of empiric therapy, and the place of third-generation cephalosporins

Choosing appropriate antimicrobial therapy for patients with pneumonia requires knowledge of the etiologic agents seen in specific kinds of patients at specific times and places. For community-acquired pneumonia, there is an important difference in the agents seen in the normal and the compromised host. The normal host most often presents with viral, mycoplasmal, or pneumococcal pneumonia. The exact place of Chlamydia pneumoniae is still under study. A normal host who aspirates is at risk of anaerobic pneumonia. Normal hosts with influenza may acquire superinfection with Streptococcus pneumoniae, Haemophilus influenzae, or Staphylococcus aureus. Under specific epidemiologic conditions, community-acquired pneumonia may be due to Legionella species, Yersinia pestis, Francisella tularensis, Coxiella burnetii, Chlamydia psittaci, a mycotic agent, or tuberculosis. Patients with chronic bronchitis and emphysema are predisposed to H. influenzae, Moraxella catarrhalis, and S. pneumoniae infections. HIV-infected patients are likely to have Pneumocystis carinii pneumonia and pneumonia due to cytomegalovirus, S. pneumoniae, and H. influenzae. Patients with diabetes, nursing-home patients, hospitalized patients, immuno-compromised patients, and patients with recent antibiotic therapy are predisposed to pneumonia due to Gram-negative aerobic bacilli of enteric and environmental origin. Initial therapy should be directed at the likely organism or organisms based on hospital susceptibility surveillance. In the normal host with community-acquired pneumonia, the therapy will often be penicillin G or erythromycin. In the patient predisposed to Gram-negative pneumonia, a third-generation cephalosporin with or without an aminoglycoside is the usual choice.