Penicillinase-producing Staphylococci Research Articles

β-lactamase-mediated Resistance: A Biochemical, Epidemiological and Genetic Overview

Early after the introduction of the first (narrow spectrum) penicillins into clinical use, penicillinase-producing staphylococci replaced (worldwide) the previously susceptible microorganisms. Similarly, the extensive use of broad-spectrum, orally administered β- lactams (like ampicillin, amoxicillin or cefalexin) provided a favorable scenario for the selection of gram-negative microorganisms producing broad spectrum β-lactamases almost 45 years ago. These microorganisms could be controlled by the introduction of the so called "extended spectrum cephalosporins". However, overuse of these drugs resulted, after a few years, in the emergence of extended-spectrum β-lactamases (ESBLs) through point mutations in the existing broad-spectrum β-lactamases, such as TEM and SHV enzymes. Overuse of extended-spectrum β-lactams also gave rise to chromosomal mutations in regulatory genes which resulted in the overproduction of chromosomal AmpC genes, and, in other regions of the world, in the explosive emergence of other ESBL families, like the CTX-Ms. Carbapenems remained active on microorganisms harboring these extended-spectrum β-lactamases, while both carbapenems and fourth generation cephalosporins remained active towards those with derepressed (or the more recent plasmidic) AmpCs. However, microorganisms countered this assault by the emergence of the so called carbapenemases (both serine- and metallo- enzymes) which, in some cases, are actually capable of hydrolyzing almost all β-lactams including the carbapenems. Although all these enzyme families (some of them represented by hundreds of members) are for sure pre-dating the antibiotic era in environmental and clinically significant microorganisms, it was the misuse of these antibiotics that drove their evolution. This paper describes in detail each major class of β-lactamase including epidemiology, genetic, and biochemical evaluations.

β-lactamase-mediated Resistance: A Biochemical, Epidemiological and Genetic Overview

Early after the introduction of the first (narrow spectrum) penicillins into clinical use, penicillinase-producing staphylococci replaced (worldwide) the previously susceptible microorganisms. Similarly, the extensive use of broad-spectrum, orally administered β- lactams (like ampicillin, amoxicillin or cefalexin) provided a favorable scenario for the selection of gram-negative microorganisms producing broad spectrum β-lactamases almost 45 years ago. These microorganisms could be controlled by the introduction of the so called “extended spectrum cephalosporins”. However, overuse of these drugs resulted, after a few years, in the emergence of extended-spectrum β-lactamases (ESBLs) through point mutations in the existing broad-spectrum β-lactamases, such as TEM and SHV enzymes. Overuse of extended-spectrum β-lactams also gave rise to chromosomal mutations in regulatory genes which resulted in the overproduction of chromosomal AmpC genes, and, in other regions of the world, in the explosive emergence of other ESBL families, like the CTX-Ms. Carbapenems remained active on microorganisms harboring these extended-spectrum β-lactamases, while both carbapenems and fourth generation cephalosporins remained active towards those with derepressed (or the more recent plasmidic) AmpCs. However, microorganisms countered this assault by the emergence of the so called carbapenemases (both serine- and metallo- enzymes) which, in some cases, are actually capable of hydrolyzing almost all β-lactams including the carbapenems. Although all these enzyme families (some of them represented by hundreds of members) are for sure pre-dating the antibiotic era in environmental and clinically significant microorganisms, it was the misuse of these antibiotics that drove their evolution. This paper describes in detail each major class of β-lactamase including epidemiology, genetic, and biochemical evaluations.

β-lactamase-mediated Resistance: A Biochemical, Epidemiological and Genetic Overview

Early after the introduction of the first (narrow spectrum) penicillins into clinical use, penicillinase-producing staphylococci replaced (worldwide) the previously susceptible microorganisms. Similarly, the extensive use of broad-spectrum, orally administered β- lactams (like ampicillin, amoxicillin or cefalexin) provided a favorable scenario for the selection of gram-negative microorganisms producing broad spectrum β-lactamases almost 45 years ago. These microorganisms could be controlled by the introduction of the so called “extended spectrum cephalosporins”. However, overuse of these drugs resulted, after a few years, in the emergence of extended-spectrum β-lactamases (ESBLs) through point mutations in the existing broad-spectrum β-lactamases, such as TEM and SHV enzymes. Overuse of extended-spectrum β-lactams also gave rise to chromosomal mutations in regulatory genes which resulted in the overproduction of chromosomal AmpC genes, and, in other regions of the world, in the explosive emergence of other ESBL families, like the CTX-Ms. Carbapenems remained active on microorganisms harboring these extended-spectrum β-lactamases, while both carbapenems and fourth generation cephalosporins remained active towards those with derepressed (or the more recent plasmidic) AmpCs. However, microorganisms countered this assault by the emergence of the so called carbapenemases (both serine- and metallo- enzymes) which, in some cases, are actually capable of hydrolyzing almost all β-lactams including the carbapenems. Although all these enzyme families (some of them represented by hundreds of members) are for sure pre-dating the antibiotic era in environmental and clinically significant microorganisms, it was the misuse of these antibiotics that drove their evolution. This paper describes in detail each major class of β-lactamase including epidemiology, genetic, and biochemical evaluations.

Assessment of molecularly imprinted sol–gel materials for selective room temperature phosphorescence recognition of nafcillin

Sol–gel imprinted materials were prepared against nafcillin, a semisynthetic β-lactamic antibiotic employed in the treatment of serious infections caused by penicillinase-producing staphylococci. Two approaches were addressed for preparation of the imprinted materials and the controls: as conventional monoliths, which were ground and sieved to a desired particle size for rebinding analysis, and as films on supporting glass slides. The specific binding sites that are created during the imprinting process are analyzed via selective room temperature phosphorescence (RTP) (sol–gel films) measurements as well as via competitive room temperature phosphorescence ligand assay. Results demonstrated the importance of the physical configuration of the imprinted material for minimizing non-specific binding. The close similarities between the structures of different β-lactamic antibiotics made it possible to interpret the roles of the template structure on specific molecular recognition. In this article, we introduce the use of room temperature phosphorescence as selective transduction method for the template. The imprinted sol–gel films displayed enhanced specific binding characteristics respect to the monolithic sol–gel and can be envisaged for the use as recognition matrices for the screening and rapid selection of antibiotics from a combinatorial library or for the rapid control of nafcillin in biological samples (e.g. milk, serum, urine).

Cooperative evolution of mechanisms of β-lactam resistance

Cooperative evolution of mechanisms of β-lactam resistance

Resistance to glycopeptides in enterococci.

The development of resistance to glycopeptides (vancomycin and teicoplanin) is one of the best examples of the alternation between success and failure that spans the history of the antibiotic era. The introduction of penicillin G was revolutionary. However, the emergence in the 1950s of clinical isolates of Staphylococcus aureus that were resistant to penicillins and subsequently to erythromycin and tetracyclines stimulated the development of large-scale screening programs for new drugs. Under these circumstances, an American missionary, Reverend W. M. Bouw, provided Eli Lilly (Indianapolis) with a soil sample from Borneo [1]. The organism that produces vancomycin, Amycolatopsis orientalis, was isolated from this sample in 1954. Since vancomycin proved to be potent against grampositive bacteria, including penicillinase-producing staphylococci, it was licensed for human use in record time. However, the renal toxicity and ototoxicity associated with vancomycin therapy (due for the most part to impurities in the drug) together with the introduction of new penicillinase-resistant /-lactams led to a rapid decline in the use of vancomycin. In the 1980s, interest in vancomycin revived because of several factors. During this period, methicillin-resistant and multiresistant staphylococci, against which vancomycin is often the only active antibiotic, were emerging worldwide. At the same time, medical advances had resulted in the prolongation of life for increasingly fragile, immunocompromised patients who are exposed to opportunistic pathogens such as multiresistant gram-positive organisms. In addition, it was determined that pseudomembranous colitis could be treated with oral vancomycin, and a new glycopeptide, teicoplanin, was introduced in 1984 in certain European countries. The apparent absence of resistance to vancomycin in grampositive bacteria and a decrease in the toxicity associated with vancomycin therapy (purified formulations of the drug had become available) led to a notable increase in the prescription of this antibiotic. In the United States, a 20-fold increase in the consumption of vancomycin was observed over a 10-year period at a university hospital [2].

Penicillins

The penicillins are a large group of bicyclic ring compounds which contain a 4-membered beta-lactam ring (penams) fused to a 5-membered thiazolidine ring. Benzylpenicillin (penicillin G) was the first natural penicillin with potent activity against all Gram-positive pathogens, Gram-negative cocci and some spirochaetes and actinomycetes. For the last 50 years benzylpenicillin has been the mainstay of therapy for serious pneumococcal, streptococcal, meningococcal and gonococcal infections. However, the past decade has seen the emergence of resistance in certain parts of the world, initially among the gonococci, and more recently among the pneumococci and meningococci. Discovery of the 6-aminopenicillinamic acid nucleus has led to considerable manipulation of the basic ring structure, resulting initially in the synthesis of ampicillin, and subsequently the other aminopenicillins, analogues, esters and prodrugs. These drugs have the advantages of improved oral bioavailability and superior activity against Haemophilus influenzae, certain Gram-negative bacilli, salmonellae, enterococci and Listeria monocytogenes, making these agents popular in the treatment of upper and lower respiratory tract infections and urinary tract infections. The increasing spread of bacterial resistance, particularly among Enterobacteriaceae and H. influenzae, has curtailed the usefulness of these drugs in these clinical settings. To counteract this problem, a number of agents combining a penicillin and a beta-lactamase inhibitor (e.g. clavulanic acid, tazobactam and sulbactam) have been developed. These inhibitors have no intrinsic antibacterial activity, but combining them with a penicillin (e.g. amoxicillin/clavulanic acid) confers greater stability to beta-lactamases and hence a broader spectrum of activity. The emergence of penicillinase-producing staphylococci that rendered benzylpenicillin ineffective also stimulated the search for penicillinase-resistant penicillins--methicillin and nafcillin, followed by the acid-stable isoxazolyl penicillins. These agents are now the principle antistaphylococcal treatment. Methicillin-resistant coagulase-negative staphylococci are currently a major cause of hospital sepsis, and are resistant to these latter agents. Enteric Gram-negative bacilli have been the predominant cause of serious hospital infections during the last 30 years. Further manipulation of the penicillin structure has resulted in compounds with broader activity against Gram-negative bacilli, particularly Pseudomonas aeruginosa, while retaining activity against Gram-positive pathogens. The carboxypenicillins were the first step in this direction, but have been largely superseded by the ureidopenicillins. These agents have better activity against P. aeruginosa, and are still effective against Gram-negative and Gram-positive bacteria, including enterococci and anaerobic organisms.(ABSTRACT TRUNCATED AT 400 WORDS)

Oral mucosal soft tissue necrosis caused by superinfection: Report of three cases

Three patients in whom flap necrosis developed after oral surgeries and antibiotic therapies were studied microbiologically by routine aerobic and anaerobic methods. In all cases the bacteria Enterobacter cloacae, Klebsiella oxytoca, Escherichia coli, and coagulase-negative penicillinase-producing staphylococci were resistant to the antibiotics used. These bacteria are frequent microorganisms of superinfection and were not found after the necrotic tissues had repaired.

A Retrospective View of β-Lactamases

The discovery of a penicillinase (later shown be a beta-lactamase) 50 years ago in Oxford came from the thought that the resistance of many Gram-negative bacteria to Fleming's penicillinase might be due to their production of a penicillin-destroying enzyme. The emergence of penicillinase-producing staphylococci in the early 1950s, particularly in hospitals, raised the question whether the medical value of penicillin would decline. The introduction of new semi-synthetic penicillins and cephalosporins in the 1960s began to reveal many beta-lactamases distinguishable by their different substrate profiles. In this period it was established that genes encoding beta-lactamases from Gram-negative bacilli could be carried from one organism to another on plasmids and also that penicillin inhibited a transpeptidase involved in bacterial cell wall synthesis. During the last two decades a number of these enzymes have been purified and the genes encoding them have been cloned. Much has now been learned, with the aid of powerful modern techniques, about their structures, their active sites, their relationship to penicillin-sensitive proteins in bacteria and to their likely evolution. Further knowledge may contribute to a more rational approach to chemotherapy in this area. Experience suggests that a need for new substances will continue.

The Penicillins

The penicillin family of antibiotics is ever expanding and remains an important part of our antimicrobial armamentarium. These medications generally have bactericidal activity, excellent distribution throughout the body, low toxicity, and efficacy against infections due to susceptible organisms. The clinical introduction of aqueous penicillin G for treatment of streptococcal and staphylococcal infections was an important pharmacologic landmark. The emergence of penicillinase-producing staphylococci prompted the development of the penicillinase-resistant penicillins (methicillin, oxacillin, nafcillin, and others), in which the acyl side chain prevented disruption of the beta-lactamase ring. The aminopenicillins (ampicillin, amoxicillin, and others) were later developed because of the need for gram-negative antimicrobial activity. Their spectrum included Escherichia coli, Proteus mirabilis, Shigella, Salmonella, Listeria, and Haemophilus. The search for a penicillin with even further antimicrobial activity against the Enterobacteriaceae and Pseudomonas aeruginosa led to the development of the carboxypenicillins, ureidopenicillins, and piperazine penicillins. Recently, the combination of a beta-lactamase inhibitor (clavulanic acid or sulbactam) and an amino-penicillin or ticarcillin has resulted in further extension of their antibacterial spectra. The development of an ideal penicillin that is nonsensitizing, bioavailable, beta-lactamase-resistant, rapidly bactericidal, nontoxic, and inexpensive and that has high affinity to penicillin-binding proteins and no inoculum effect remains the goal.

Cephalosporins 1945-1986.

In 1945, after penicillin had been introduced into medicine, an antibiotic-producing species of Cephalosporium was isolated from a sewage outfall in Sardinia. Four years later in Oxford, this organism was found to produce several antibiotics, one of which was a penicillin with a new side-chain, penicillin N. During a chemical study in 1953, this penicillin was shown to be contaminated with a second substance, cephalosporin C, which contained a beta-lactam ring but was resistant to hydrolysis by a penicillinase (beta-lactamase). At that time, penicillinase-producing Staphylococci were causing a serious problem in hospitals. The isolation of the nucleus of cephalosporin C (7-ACA) enabled pharmaceutical manufacturers to produce many thousands of cephalosporins, some of which have been effective in the treatment of serious infections by a number of Gram-positive and Gram-negative bacteria. The cephalosporins, like the newer penicillins, have a very low toxicity and have greatly extended the range of chemotherapy. New, sensitive screening methods have revealed further families of clinically useful substances that contain a reactive beta-lactam ring. Genetic engineering has now begun to throw light on the nature of the enzymes that are involved in the biosynthesis of penicillins and cephalosporins, and x-ray crystallography may soon provide detailed 3-dimensional pictures of some of the bacterial enzymes with which the active beta-lactam ring reacts. Rational approaches to the production and design of new and potentially useful compounds may then be within sight.

Use of Antibiotics in Dental Practice

Penicillin G administered parenterally or penicillin V administered orally are currently the antibiotics of choice for treatment of dental infections of usual etiology. Infections caused by penicillinase-producing staphylococci or those involving gram-negative bacteria should be treated with a penicillinase-resistant penicillin or an ampicillin-like derivative, respectively. Erythromycin is a second-choice bacteriostatic antibiotic, becoming first choice for treating dental infections in patients allergic to penicillin. The cephalosporins, similar in action to ampicillin-like penicillin derivatives, may be used with caution in patients who have exhibited delayed-type allergic reactions to penicillin and when erythromycin cannot be used. Their lack of advantage over other agents, and their cost, precludes routine use for usual dental infections. Clindamycin administered orally or lincomycin administered parenterally are reserve antibiotics indicated for treatment of bone infections and/or anaerobic infections refractory to commonly used antibiotics. Tetracyclines are, at best, third-choice agents for usual dental infections. However, they are useful for cases of acute necrotizing ulcerative gingivitis requiring systemic antibiotic therapy when penicillin is precluded. Vancomycin and streptomycin are used prophylactically for prevention of infective endocarditis in patients with prosthetic heart valves. Nystatin remains a first-choice agent for treatment of oral candidal infections. Ketoconazole, an orally active systemic antifungal agent, may be used for monilial infections of the oral cavity refractory to nystatin. Chemotherapy of viral infections is difficult because of the timing of events of the disease process versus appearance of clinical symptoms and lack of effective agents with selective toxicity. Herpes infections of the oral cavity have been treated--with limited success--with idoxuridine. Acyclovir, a newer antiviral drug, offers little clinical benefit for herpes infections in usually healthy patients but may be of value for treating such infections in immunocompromised patients. All antimicrobial agents may cause adverse reactions of varying degrees of severity. Most orally administered antibiotics may cause gastrointestinal disturbances. Superinfections occur with broad-spectrum antibiotics and a severe form of superinfection, antibiotic-associated colitis, has occurred with almost all antibiotics. Allergic reactions of all degrees of severity can occur with most antibiotics. The penicillins, followed by the cephalosporins and tetracyclines, are most frequently implicated in these reactions.(ABSTRACT TRUNCATED AT 400 WORDS)

468 TREATMENT (Rx) OF GROUP A STREPTOCOCCAL (GAS) PHARYNGITIS. RESULTS OF A PROSPECTIVE, RANDOMIZED STUDY OF 4 ANTIBIOTICS

Penicillin V (P), benzathine/procaine penicillin (BP), cefadroxil (C), and erythromycin estolate (EE) were used for Rx of 198 children with GAS pharyngitis. Patients ranged in age from 2-15 years and all were symptomatic when Rx was started. Rx groups were similar with regard to age, sex, weight and duration of illness before Rx. All pts improved within 24 hours of initiation of Rx. At 5 days GAS were present in the throat cultures of 3 pts (2P, 1C); the serotypes of 2 organisms were identical to those isolated from pre-Rx cultures. Four days after Rx GAS were cultured from 3(6%) P-Rx'd pts, 1(2%) C pt, 1(2%) E pt, and 2(4%) BP pts. All were serotypically identical to the pre-Rx organisms. Two (21%) of these pts were symptomatic. GAS were isolated from 19 pts at 7-21 days after Rx; 12 of 19 had new serotypes and 11(91%) of these 12 were symptomatic. Excluding pts with new infections, the bacteriologic failure rates (relapse) during the 31-day study period were: 2%(EE), 6%(C), 12%(P) and 12%(BP). Eleven of 16(69%) children with relapse were asymptomatic at the time of recurrence. There were no significant differences in the rates of serologic conversion between symptomatic (82%) and asymptomatic (54%) children or between those with reinfection (77%) and those with relapse (63%). Antibiotic resistance of GAS, presence of penicillinase-producing staphylococci and lack of compliance were not related to relapse. These four antibiotics were equally effective in Rx of GAS pharyngitis.

Disposition of Nafcillin in Patients with Cirrhosis and Extrahepatic Biliary Obstruction

Nafcillin, a semisynthetic penicillin effective against penicillinase-producing staphylococci, is eliminated largely in man via the liver. This study assessed the effect of cirrhosis and extrahepatic biliary obstruction in man on the pharmacokinetics of nafcillin. The plasma clearance of nafcillin controls was 583 +/- 144.2 ml per min (mean +/- SD) and fell strikingly to 291 +/- 147.6 and 163 +/- 56.3 ml per min in patients with cirrhosis and extrahepatic obstruction, respectively (P less than 0.001). In the latter two groups nafcillin excreted in urine increased from about 30 to 50% of administered dose (P less than 0.02), suggesting that renal disease superimposed on hepatic disease would further decrease over-all nafcillin clearance. The depression of nafcillin clearance with hepatobiliary disease did not correlate with any conventional liver laboratory test. The initial volume of distribution of nafcillin (V1) was unaltered but at steady state (Vd()) there was a significant reduction in the distribution volume in the patients with liver disease. Accordingly, the impairment in drug elimination, as assessed by its clearance from plasma, was underestimated by the prolongation of the nafcillin elimination half-life (t1/2(beta)) which was 1.02 +/- 0.20 hr in controls, and 1.23 +/- 0.31 (P greater than 0.05) and 1.73 +/- 0.44 hr (P less than 0.03), respectively, in patients with cirrhosis and extrahepatic obstruction.

Cefuroxime - a new cephalosporin antibiotic.

Cefuroxime is a new broad spectrum cephalosporin antibiotic for administration by injection. It is stable to most beta-lactamases. It is active against gram-positive organisms, including penicillinase-producing staphylococci, and has wide activity against gram-negative bacilli including Enterobacter and many strains of indole-positive Proteus spp. The substance is also highly active against Haemophilus influenzae and Neisseria gonorrhoeae. Studies on human volunteers showed that it produced high, long-lasting blood levels with virtually complete recovery of unchanged antibiotic in the urine. No evidence of toxicity due to cefuroxime was found. Slight, short-lived pain followed intramuscular injection, and the compound was well tolerated intravenously.

Cephradine

Cephradine (Eskacef - SKF; Velosef - Squibb) is a new semi-synthetic cephalosporin for oral use. Like other cephalosporins it is active against both Gram-negative and Gram-positive pathogens, apparently including penicillinase-producing staphylococci (though this has been questioned1). It is advertised as having ‘new striking power’, but from the data provided its spectrum of activity closely resembles that of cephalexin (Ceporex - Glaxo; Keflex - Lilly),2 and the promotional literature on cephradine makes no direct comparison between the two drugs.

Cephalexin--a new oral antibiotic.

Summary The pharmacology, antimicrobial activity and clinical uses of cephalexin, a semi-synthetic derivative of cephalosporin C, are described. Cephalexin is active, when taken by mouth, against Gram-positive cocci, including penicillinase-producing staphylococci, and against many Gram-negative organisms including Gram-negative rods. There is a low incidence of side effects.

Treatment of Suspected Staphylococcal Infection

To the Editor:— A recent letter about the dangerous triangle warrants further comment ( 209 :561, 1969). Dr. Eckberg gives a concise and complete description of the progression of superficial facial infections to cavernous sinus thrombosis. However, several aspects of the treatment must be questioned. Despite antibiotic disk sensitivities, tetracycline is not an appropriate antibiotic for staphylococcal infections. Whenever a life-threatening staphylococcal infection is suspected (eg, cavernous sinus thrombosis) the patient should be treated with antibiotics effective against penicillinase-producing staphylococci. Methicillin and the cephalosporin derivatives and vancomycin are examples of such drugs. They may be used alone or in conjunction with penicillin, which is the most effective agent for nonpenicillinase-producing staphylococci. These drugs are not only bactericidal ( tetracycline is bacteriostatic), but also circumvent the problem of rapidly emerging drug resistance which contraindicates tetracycline in staphylococcal infections. Equally important, cortisone and irradiation provide no benefit in staphylococcal infections ( 183 :462, 1963) and

Factors involved in treatment failures following oral penicillin therapy of streptococcal pharyngitis

Among 331 children with group A streptococcal pharyngitis who were treated with a 10 day oral regimen of either sodium nafcillin or penicillin V potassium, there were 39 treatment failures. There was no correlation between the incidence of relapse and patient's age, sex, interval between onset of illness and onset of therapy, history of respiratory tract allergy, compliance in completing therapy, concomitant presence of penicillinase-producing staphylococci, or incidence of homologous streptococci in household contacts. There was, however, a significantly higher incidence of relapse in patients harboring M-typable strains, as compared with patients harboring nontypable strains; this was particularly evident for patients with types 3 and 12 streptococci. Among the relapse group, there was no difference in the bacteriologic outcome of those patients who received a second course of treatment as compared with the patients who were not re-treated.

Synergistic combinations of penicillins in the treatment of bacteriuria.

MOST bacteria that are highly resistant to benzylpenicillin produce penicillinases.1 2 3 4 Large numbers of bacterial cells of many strains, even some considered to be highly resistant to penicillins and cephalosporins, can be killed in the presence of moderate concentrations of these antibiotics, and the survivors proliferate only after most or all of the antibiotic has been destroyed by the enzymes.2 , 4 5 6 Except for a few unusual isolates,7 penicillinase-producing staphylococci owe their penicillin resistance completely to penicillinase (β-lactamase). There is considerable evidence that β-lactamases are also important for the resistance of many strains of gram-negative bacilli to penicillins4 5 6 , 8 and cephalosporins,5 , 6 but the precise . . .