Peptostreptococcus Infection Medication

Updated: Jul 06, 2017
  • Author: Itzhak Brook, MD, MSc; Chief Editor: Mark R Wallace, MD, FACP, FIDSA  more...
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Medication

Medication Summary

Clinical judgment, personal experience, safety, and expected level of patient compliance should direct the physician in the choice of antimicrobial agents. When choosing antimicrobials for the therapy of mixed infections, their aerobic and anaerobic antibacterial spectrum and their availability in oral or parenteral form should be considered. Some antimicrobials have a limited range of activity.

Aside from susceptibility patterns, other factors influencing the choice of antimicrobial therapy include the pharmacologic characteristics of the various drugs, their toxicity, their effect on the normal florae, and their bactericidal activity. Although identification of the infecting organisms and their antimicrobial susceptibility may be needed for selection of optimal therapy, the clinical setting and gram-stain preparation of the specimen may indicate the types of anaerobes present in the infection and may indicate the nature of the infectious process.

Although the duration of therapy for anaerobic infections is generally longer than for aerobic and facultative infections, the duration must be individualized depending on the patient's response to the therapy. In some cases, the patient may require a 6- to 8-week course. However, therapy may be shortened after proper surgical drainage. [29]

Because peptostreptococci are often mixed with other aerobic and anaerobic bacteria in the infectious process, broader antimicrobial coverage is often necessary. Furthermore, because of the difficulty in recovering other fastidious anaerobic organisms, they may not be recovered even when cultures are taken.

Antimicrobial agents with broader coverage against anaerobic bacteria, including peptostreptococci, include cefoxitin, clindamycin, carbapenem (eg, imipenem, meropenem, ertapenem, doripenem), tigecycline, the combination of a penicillin (eg, ticarcillin) with a beta-lactamase inhibitor (ie, clavulanate), and quinolones with anti-anaerobic activity (ie, moxifloxacin). [29]

An anti–gram-negative enteric agent is generally added to treat Enterobacteriaceae when treating intra-abdominal infections.

Metronidazole has excellent activity against gram-negative anaerobic bacteria and has no activity against aerobic and facultative bacteria. Gram-positive anaerobic bacteria including peptostreptococci, microaerophilic streptococci, Propionibacterium acnes, and Actinomyces species are often resistant; therefore; adding an antimicrobial that is effective against these organisms (eg, penicillin) is often necessary. [28, 29]

Penicillin is added to metronidazole to cover microaerophilic streptococci, peptostreptococci, Actinomyces species, and Arachnia species when treating intracranial and dental infections.

Penicillin is the antimicrobial of choice for bacteremia caused by non–beta-lactamase producers; however, if other organisms may be involved in another site, broader coverage is needed.

Clindamycin is effective against aerobic and anaerobic gram-positive cocci. However, resistance of the B fragilis group in some centers in the United States recently reached about 40%. This agent can therefore not be used as empiric therapy. Antibiotic-associated colitis due to Clostridium difficile, although associated with most antimicrobials, was first described following clindamycin therapy.

A macrolide or amoxicillin is added to metronidazole to treat S aureus and aerobic streptococci in upper respiratory tract infections. The macrolides have moderate-to-good in vitro activity against anaerobic bacteria other than B fragilis group strains and fusobacteria. Macrolides are active against pigmented Prevotella and Porphyromonas species and microaerophilic streptococci, gram-positive non–spore-forming anaerobic bacilli, and certain clostridial organisms. They are less effective against Fusobacterium and Peptostreptococcus species. [31]

Tigecycline has effective in vitro activity against both gram-positive and gram-negative anaerobes, as well as against gram-positive aerobic strains such as methicillin-resistant staphylococci, streptococci, and enterococci. Resistance of members of the B fragilis group varied from 3.3-7.2%. [26] Tigecycline was approved by the US Food and Drug Administration (FDA) for the treatment of complicated skin and skin-structure infections and complicated intra-abdominal infections.

The newer tetracycline analogs doxycycline and minocycline are more active than tetracycline. Because of the significant resistance to these drugs, they are useful only when susceptibility tests can be performed or in less severe infections in which a therapeutic trial is feasible. Doxycycline is effective against chlamydial and mycoplasmal infections and is added to most regimens when treating pelvic infections.

Trovafloxacin, moxifloxacin, and gatifloxacin yield low minimum inhibitory concentrations (MICs) against most groups of anaerobes. Moxifloxacin was approved by the FDA for the treatment of complicated skin and skin-structure infections and complicated intra-abdominal infections. However, up to 40% of Bacteroides species are resistant to moxifloxacin. [32] The use of the quinolones is restricted in growing children and pregnancy because of their possible adverse effects on the cartilage.

Oral therapy for peptostreptococci is often substituted for parenteral therapy. Oral agents include clindamycin, amoxicillin and clavulanate, and chloramphenicol.

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Antimicrobials

Class Summary

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.

Penicillin G (Pfizerpen)

Interferes with synthesis of cell-wall mucopeptide during active multiplication, resulting in bactericidal activity against susceptible microorganisms (beta-lactam).

Cefoxitin (Mefoxin)

Second-generation cephalosporin indicated for gram-positive cocci and gram-negative rod infections. Infections caused by cephalosporin- or penicillin-resistant gram-negative bacteria may respond.

Cefotetan (Cefotan)

Second-generation cephalosporin indicated for management of infections caused by susceptible gram-positive cocci and gram-negative rods.

Clindamycin (Cleocin)

Resistance of Bacteroides fragilis group against lincosamide has increased. However, these agents are effective against peptostreptococci. They are used for treatment of serious skin and soft tissue staphylococcal infections. Effective against aerobic and anaerobic streptococci (except enterococci). Inhibits bacterial growth, possibly by blocking dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest.

Amoxicillin and clavulanate (Augmentin)

Treat bacteria resistant to beta-lactam antibiotics.

Ticarcillin and clavulanate potassium (Timentin)

Inhibit biosynthesis of cell-wall mucopeptide and are effective during stage of active growth. Contains 4.7-5 mEq of Na+/g.

Chloramphenicol (Chloromycetin)

Binds to 50S bacterial-ribosomal subunits and inhibits bacterial growth by inhibiting protein synthesis. Effective against gram-negative and gram-positive bacteria.

Imipenem and cilastatin (Primaxin)

For treatment of multiorganism infections in which other agents do not have wide-spectrum coverage or are contraindicated because of potential for toxicity.

Meropenem (Merrem)

Bactericidal broad-spectrum carbapenem antibiotic that inhibits cell-wall synthesis. Effective against most gram-positive and gram-negative bacteria. Has slightly increased activity against gram-negatives and slightly decreased activity against staphylococci and streptococci compared with imipenem.

Ertapenem (Invanz)

Bactericidal activity results from inhibition of cell wall synthesis and is mediated through ertapenem binding to penicillin-binding proteins. Stable against hydrolysis by a variety of beta-lactamases, including penicillinases, cephalosporinases, and extended-spectrum beta-lactamases. Hydrolyzed by metallo-beta-lactamases.

Moxifloxacin (Avelox)

Inhibits the A subunits of DNA gyrase, resulting in inhibition of bacterial DNA replication and transcription.

Tigecycline (Tygacil)

A glycylcycline antibiotic that is structurally similar to tetracycline antibiotics. Inhibits bacterial protein translation by binding to 30S ribosomal subunit, and blocks entry of amino-acyl tRNA molecules in ribosome A site. Complicated intra-abdominal infections caused by C freundii, E cloacae, E coli, K oxytoca, K pneumoniae, E faecalis (vancomycin-susceptible isolates only), S aureus (methicillin-susceptible isolates only), S anginosus group (includes S anginosus, S intermedius, and S constellatus), B fragilis, B thetaiotaomicron, B uniformis, B vulgatus, C perfringens, and P micros.

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