Rates of hospital-acquired pneumonia (HAP), due to multidrug-resistant (MDR) pathogens have increased dramatically in hospitalized patients, especially in intensive care and transplant patients.Sources of pathogens for HAP include healthcare devices, the environment (air, water, equipment, and fomites), and commonly the transfer of microorganisms between the patient and staff or other patients.Mechanisms of antibiotic resistance for specific bacterial pathogens have provided new insight into the adaptability of these pathogens.Resistance to piperacillin, ceftazidime, cefepime, other oxyimino- beta-lactams, imipenem and meropenem, aminoglycosides, or fluoroquinolones is increasing in the United States.
In the United States, more than 50% of the intensive care unit (ICU) infections caused by S. aureus are with methicillin-resistant organisms. Methicilllin-resistant Staphylococcus aureus (MRSA) infection is caused by staphylococcus aureus bacteria — often called "staph." Decades ago, a strain of staph emerged in hospitals that was resistant to the broad-spectrum antibiotics including to all penicillins, including methicillin and other narrow-spectrum ß-lactamase-resistant penicillin antibiotics ;commonly used to treat it. Dubbed methicillin-resistant Staphylococcus aureus (MRSA), it was one of the first germs to outwit all but the most powerful drugs.
MRSA may also be known as oxacillin-resistant Staphylococcus aureus (ORSA) and multiple-resistant Staphylococcus aureus, while non-methicillin resistant strains of S. aureus are sometimes called methicillin-susceptible Staphylococcus aureus (MSSA) if an explicit distinction must be made.
Staph bacteria are not uncommon in health care settings. In fact, they account for a large number of hospital-related infections each year. Methicillin resistant Staphylococcus aureus (MRSA) is one of these types of bacteria which is now found among athletes, military recruits and others in the general population. What is particularly concerning to medical experts is that MRSA is resistant to many common antibiotics.
An MRSA infection causes skin and soft tissue lesions and, when left untreated, can invade deeper structures such as bone and muscle, or even the blood stream – and can be quite serious.“Fortunately, the MRSA bacteria acquired in the community is only resistant to a few, including penicillins and cephalosporins.”
Methicillin-resistant Staphylococcus aureus (MRSA) produces a penicillin-binding protein with reduced affinity for beta-lactam antibiotics that is encoded by the mecA gene, which is carried by one of a family of four mobile genetic elements. Strains with mecA are resistant to all commercially available beta-lactams and many other antistaphylococcal drugs, with considerable country-to-country variability.
Staph infections begin abruptly. Someone with MRSA may develop a large area of redness on the skin, swelling and pain. A pustule or abscess might develop, or boils and carbuncles (red, lumpy sores filled with pus). Some patients have pneumonia-like symptoms or, less frequently, symptoms of toxic shock.If left untreated or not treated aggressively, MRSA can progress to a deeper infection, involvement of the bloodstream, and to the spread of infection to other organs. A patient who is not responding to antibiotics will actually be getting worse after two or three days, experiencing more pain with spreading inflammation. Today, that form of staph, known as community-associated MRSA, or CA-MRSA, is responsible for many serious skin and soft tissue infections and for a serious form of pneumonia.
Doctors in New York have identified three households in which there was clinical, microbiological, and molecular evidence of heterosexual transmission of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA).
Until now, heterosexual transmission of CA-MRSA has not been documented, the Columbia University-based team notes in the current issue of the journal Clinical Infectious Diseases.
MRSA is most often found in the hospital setting and has typically affected very ill, elderly patients and those with poorly functioning immune systems. Infection can pose a serious problem because it is susceptible to few antibiotics.
While homosexual transmission of CA-MRSA has been documented among HIV-positive men, heterosexual transmission "poses a far greater risk of dissemination in the community," Dr. Franklin D. Lowy and colleagues point out.
According to their report, in the first household, a woman reported that she noticed "tiny pimples" in the groin area, which appeared 6 months earlier after she was sexually active with five different men, including her husband. Both her husband and another partner also had similar "pimples" in the groin. The woman's vaginal swab sample and husband's groin sample were both positive for CA-MRSA and the isolated bacteria were identical.
In household two, a woman who was sexually active with her husband sought treatment for a MRSA-positive buttock abscess. Two months later, her husband developed an extensive rash and boils that were tested positive for CA-MRSA. At the same time, the woman developed boils in her pubic area. The vaginal swab from the wife and groin swab from husband were both MRSA-positive.
In household three, a woman reported multiple episodes of MRSA-positive abscesses over 90 days and these episodes always followed visits from her boyfriend who was a member of a military unit that had been experiencing an outbreak of MRSA infection. A sample obtained from the woman was positive for MRSA, but a sample from the boyfriend was unavailable.
The vaginal and groin samples obtained from the sexual partners in these households were all USA 300, the predominant CA-MRSA type found in the United States, the authors note.
Lowy told Reuters Health: "I think the take-home message is that spread of CA-MRSA via heterosexual activity is an underappreciated means of transmission. It may account for the ability of these strains to become resident in communities where other risk factors are not present."
The good news is that there are more antibiotic choices for MRSA. Vancomycin, clindamycin and sulfa drugs are available and effective in treating most of these infections.
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