Hospitals are primary transmission sites for CRE-based infections. Up to 75% of hospital admissions attributed to CRE were from long-term care facilities or transferred from another hospital. Suboptimal maintenance practices are the largest cause of CRE transmission. This includes the failure to adequately clean and disinfect medication cabinets, other surfaces in patient rooms, and portable medical equipment, such as X-ray and ultrasound machines that are used for both CRE and non-CRE patients.

Thus far, CRE have primarily been nosocomial infectious agents. Almost all CRE infections occur in people receiving significant medical care in hospitals, long-term acute care facilities, or nursing homes. Independent risk factors for CRE infection include use of beta-lactam antibiotics and the use of mechanical ventilation. Patients with diabetes have also been shown to be at an elevated risk for acquiring CRE infections. When compared to other hospitalized patients, those admitted from long-term acute care (LTAC) facilities have significantly higher incidence of colonization and infection rates. Another 2012 multicenter study found that over 30% of patients with recent exposure to LTAC were colonized or infected with CRE. A person susceptible to CRE transmission is more likely to be female, have a greater number of parenteral nutrition-days (meaning days by which the person received nutrition via the bloodstream), and to have had a significant number of days breathing through a ventilator.

Infections with carbapenem-resistant "Klebsiella pneumoniae" were associated with organ/stem cell transplantation, mechanical ventilation, exposure to antimicrobials, and overall longer length of stay in hospitals.

People most likely to acquire carbapenem-resistant bacteria are those already receiving medical attention. In a study carried out at Sheba medical center, there was a trend toward worse Charleson Comorbidity scores in patients who acquired CRKP during ICU stay. Those at highest risk are patients receiving an organ or stem cell implantation, use of mechanical ventilation, or have to have an extended stay in the hospital along with exposure to antimicrobials. In a study performed in Singapore, the acquisition of ertapenem-resistant Enterobacteriaceae to the acquisition of CRE. Exposure to antibiotics, especially fluoroquinolones, and previous hospitalization dramatically increased the risk of acquisition carbapenem-resistant bacteria. This study found that carbapenem-resistant acquisition has a significantly higher mortality rate and poorer clinical response compared to that of the ertapenem-resistance acquisition.

Bacteruria (also known as urinary tract infection) caused by CRKp and CSKp have similar risk factors. These include prior antibiotic use, admittance to an ICU, use of a permanent urinary catheter, and previous invasive procedures or operations. A retrospective study of patients with CRKp and CSKp infection asserted that the use of cephalosporins (a class of β-lactam antibiotics) used before invasive procedures was higher in patients with CRKp infection, suggesting that it is a risk factor.

In a three-year study, the prevalence of CRE was shown to be proportional to the lengths of stays of the patients in those hospitals. Policies regarding contact precaution for patients infected or colonized by Gram-negative pathogens were also observed in hospitals reporting decreases in CRE prevalence.

One case study showed that patients with a compromised immune response are especially susceptible to both CRE exposure and infection. In one study, an elderly patient with acute lymphoblastic leukemia being treated in a long-term care facility contracted a CRE infection. Her age and condition, combined with her environment and regulation by a catheter and mechanical ventilation, all contributed to a higher susceptibility. This highlights the importance of finding the source of the bacteria, as members of this class of patients are at continued risk for infection. Infection control and prevention of CRE should be the main focus in managing patients at high risk.

Another major risk factor is being in a country with unregulated antibiotic distribution. In countries where antibiotics are over-the counter and obtainable without a prescription, the incidence and prevalence of CRE infections were higher. One study from Japan found that 6.4% of healthy adults carried ESBL (mostly cefotaximase)-producing strains compared to 58.4% in Thailand, where antibiotics are available over the counter and without prescription. An Egyptian research group found that 63.3% of healthy adults were colonized.

In February 2015, the FDA reported about a transmission risk when people undergo a gastroenterology procedure called endoscopic retrograde cholangiopancreatography, where an endoscope enters the mouth, passes the stomach, and ends in the duodenum; if incompletely disinfected, the device can transmit CRE from one patient to another. The FDA's safety communication came a day after the UCLA Health System, Los Angeles, notified more than 100 patients that they may have been infected with CRE during endoscopies between October 2014 and January 2015. The FDA had issued its first notice about the devices in 2009.

The newborn`s exposure to the maternal vaginal bacterial flora which contains aerobic and anaerobic bacterial flora can lead to the development of anaerobic bacterial infection. These infections include cellulitis of the site of fetal monitoring (caused by "Bacterodes" spp.), bacteremia, aspiration pneumonia (caused by "Bacterodes" spp.), conjunctivitis (caused by clostridia,) omphalitis (caused by mixed flora), and infant botulism. Clostridial species may play a role in necrotizing enterocolitis. Management of these infection necessitates treating of the underlying condition(s) when present, and administration of proper antimicrobial therapy

The World Health Organization concluded that inappropriate use of antibiotics in animal husbandry is an underlying contributor to the emergence and spread of antibiotic-resistant germs, and that the use of antibiotics as growth promoters in animal feeds should be restricted. The World Organisation for Animal Health has added to the Terrestrial Animal Health Code a series of guidelines with recommendations to its members for the creation and harmonization of national antimicrobial resistance surveillance and monitoring programs, monitoring of the quantities of antibiotics used in animal husbandry, and recommendations to ensure the proper and prudent use of antibiotic substances. Another guideline is to implement methodologies that help to establish associated risk factors and assess the risk of antibiotic resistance.

Bacteria with resistance to antibiotics predate medical use of antibiotics by humans. However, widespread antibiotic use has made more bacteria resistant through the process of evolutionary pressure.

Reasons for the widespread use of antibiotics in human medicine include:

- increasing global availability over time since the 1950s

- uncontrolled sale in many low or middle income countries, where they can be obtained over the counter without a prescription, potentially resulting in antibiotics being used when not indicated. This may result in emergence of resistance in any remaining bacteria.

Other causes include:

- Antibiotic use in livestock feed at low doses for growth promotion is an accepted practice in many industrialized countries and is known to lead to increased levels of resistance.

- Releasing large quantities of antibiotics into the environment during pharmaceutical manufacturing through inadequate wastewater treatment increases the risk that antibiotic-resistant strains will develop and spread.

- It is uncertain whether antibacterials in soaps and other products contribute to antibiotic resistance, but antibacterial soaps are discouraged for other reasons.

CRE resistance depends upon a number of factors such as the health of the patient, whether the patient has recently undergone a transplant, risk of co-infection, and use of multiple antibiotics.

Carbapenem minimal inhibitory concentrations (MICs) results may be more predictive of clinical patient outcomes than the current categorical classification of the MICs being listed as susceptible, intermediate, or resistant. The study aimed to define an all-cause hospital mortality breakpoint for carbapenem MICs that were adjusted for risk factors. Another objective was to determine if a similar breakpoint existed for indirect outcomes, such as the time to death and length of stay after infection for survivors. Seventy-one patients were included, of which 52 patients survived and 19 patients died. Classification and regression tree analysis determined a split of organism MIC between 2 and 4 mg/liter and predicted differences in mortality (16.1% for 2 mg/liter versus 76.9% for 4 mg/liter). In logistic regression controlling for confounders, each imipenem MIC doubling dilution doubled the probability of death. This classification scheme correctly predicted 82.6% of cases. Patients were accordingly stratified to MICs of ≤2 mg/liter (58 patients) and ≥4 mg/liter (13 patients). Patients in the group with a MIC of ≥4 mg/liter tended to be more ill. Secondary outcomes were also similar between groups. Patients with organisms that had an MIC of ≥4 mg/liter had worse outcomes than those with isolates of an MIC of ≤2 mg/liter.

At New York Presbyterian Hospital, part of Columbia University Medical Center in New York, NY, a study was conducted on the significant rise in carbapenem resistance in "K. pneumoniae" from 1999 to 2007. Following a positive blood culture from a patient, overall mortality was 23% in 7 days, 42% in 30 days, and 60% by the end of hospitalization. The overall in-hospital mortality rate was 48%.

At Soroka Medical Center, an Israeli university teaching hospital, a study was done between October 2005 and October 2008 to determine the direct mortality rate associated with carbapenem-resistant "K. pneumoniae" bloodstream infections. The crude mortality rate for those with the resistant bacteremia was 71.9%, and the attributable mortality rate was determined to be 50% with a 95% confidence interval. The crude mortality rate for control subjects was 21.9%. As a result of the study, Soroka Medical Center started an intensive program designed to prevent the spread of carbapenem-resistant "K. pneumoniae."

A 2013 retrospective study at the Shaare Zedek Medical Center of patients with urinary tract infections (bacteriuria) caused by carbapenem-resistant "Klebsiella pneumoniae" (CRKp) showed no statistically significant difference in mortality rates from patients with bacteriuria caused by carbapenem-susceptible "K. pneumoniae" (CSKp). A 29% mortality rate was seen in patients with CRKp infection compared to a 25% mortality rate in patients with CSKp infections that produced extended-spectrum beta-lactamase (ESBL). Both mortality rates were considerably higher than that of patients with drug-susceptible urosepsis. Most patients in the study suffered from other illnesses, including dementia, immune compromise, renal failure, or diabetes mellitus. The main risk factor for death found by the study was being bedridden, which significantly increased the chance of death. This suggests that the deaths were due to reasons other than bacteriuria. Total length of hospitalization was somewhat longer in patients with CRKp infections (28 ± 33 days compared to 22 ± 28 days for patients with CSKp infection).

In a case-control study of 99 patients compared with 99 controls at Mount Sinai Hospital (Manhattan), a 1,171 bed tertiary care teaching hospital, 38% of patients in long-term care that were afflicted with CRE died from "K. pneumoniae" infection. Patients had risk factors including diabetes, HIV infection, heart disease, liver disease, renal insufficiency, one was a transplant recipient. 72% of patients who were released from the hospital with CRE were readmitted within 90 days.

A 2008 study at Mount Sinai identified outcomes associated with Carbapenem-resistant "Klebsiella pneumoniae" infections, in which patients in need of organ or stem cell transplants, mechanical ventilation, prolonged hospitalization, or prior treatment with carbapenems, had an increased probability of infection with Carbapenem-resistant "K. pneumoniae". A combination of antibiotics worked to treat infection and survival rates of infected patients increased when the focus of infection was removed.

CRE infections can set in about 12 days after liver transplantation, and 18% of those patients died a year after transplantation in a 2012 study.

Condition predisposing to anaerobic infections include: exposure of a sterile body location to a high inoculum of indigenous bacteria of mucous membrane flora origin, inadequate blood supply and tissue necrosis which lower the oxidation and reduction potential which support the growth of anaerobes. Conditions which can lower the blood supply and can predispose to anaerobic infection are: trauma, foreign body, malignancy, surgery, edema, shock, colitis and vascular disease. Other predisposing conditions include splenectomy, neutropenia, immunosuppression, hypogammaglobinemia, leukemia, collagen vascular disease and cytotoxic drugs and diabetes mellitus. A preexisting infection caused by aerobic or facultative organisms can alter the local tissue conditions and make them more favorable for the growth of anaerobes. Impairment in defense mechanisms due to anaerobic conditions can also favor anaerobic infection. These include production of leukotoxins (by "Fusobacterium" spp.), phagocytosis intracellular killing impairments (often caused by encapsulated anaerobes and by succinic acid ( produced by "Bacteroides" spp.), chemotaxis inhibition (by "Fusobacterium, Prevotella" and "Porphyromonas" spp.), and proteases degradation of serum proteins (by Bacteroides spp.) and production of leukotoxins (by "Fusobacterium" spp.).

The hallmarks of anaerobic infection include suppuration, establishment of an abscess, thrombophlebitis and gangrenous destruction of tissue with gas generation. Anaerobic bacteria are very commonly recovered in chronic infections, and are often found following the failure of therapy with antimicrobials that are ineffective against them, such as trimethoprim–sulfamethoxazole (co-trimoxazole), aminoglycosides, and the earlier quinolones.

Some infections are more likely to be caused by anaerobic bacteria, and they should be suspected in most instances. These infections include brain abscess, oral or dental infections, human or animal bites, aspiration pneumonia and lung abscesses, amnionitis, endometritis, septic abortions, tubo-ovarian abscess, peritonitis and abdominal abscesses following viscus perforation, abscesses in and around the oral and rectal areas, pus-forming necrotizing infections of soft tissue or muscle and postsurgical infections that emerge following procedures on the oral or gastrointestinal tract or female pelvic area. Some solid malignant tumors, ( colonic, uterine and bronchogenic, and head and neck necrotic tumors, are more likely to become secondarily infected with anaerobes. The lack of oxygen within the tumor that are proximal to the endogenous adjacent mucosal flora can predispose such infections.

Once the individual has VRE, it is important to ascertain which "strain".

While typical drug side effects reactions are mild to moderate; sometimes serious adverse effects occur.

As of 2016, the U.S. FDA recommended that "serious side effects associated with fluoroquinolone antibacterial drugs generally outweigh the benefits for patients with acute sinusitis, acute bronchitis, and uncomplicated urinary tract infections who have other treatment options. For patients with these conditions, fluoroquinolones should be reserved for those who do not have alternative treatment options."

Partly as a result of the efforts of Public Citizen, in 2008 the U.S. FDA ordered boxed warnings on all fluoroquinolones, advising consumers of an enhanced risk of tendon damage.

Prominent among these are side effects that became the subject of a black box warning by the U.S. FDA in 2016. The FDA wrote: "An FDA safety review has shown that fluoroquinolones when used systemically (i.e. tablets, capsules, and injectable) are associated with disabling and potentially permanent serious side effects that can occur together. These side effects can involve the tendons, muscles, joints, nerves, and central nervous system."

Quinolones are associated with a small risk of tendonitis and tendon rupture; a 2013 review found the incidence of tendon injury among those taking fluoroquinolones to be between 0.08 and 0.2%. The risk appears to be higher among people older than 60 and those also taking corticosteroids; there may also be higher risk among people who are male, have a pre-existing joint or tendon issue, have kidney disease, and are highly active. Some experts have advised avoidance of fluoroquinolones in athletes. If tendonitis occurs, it generally appears within one month, and the most common tendon that is injured appears to be the Achilles tendon. The cause is not well understood.

Nervous system effects include insomnia, restlessness, and rarely, seizure, convulsions, and psychosis. Other rare and serious adverse events have been observed with varying degrees of evidence for causation.

More generally, fluoroquinolones are tolerated, with typical drug side effects being mild to moderate. Common side effects include gastrointestinal effects such as nausea, vomiting, and diarrhea, as well as headache and insomnia. Postmarketing surveillance has revealed a variety of relatively rare but serious adverse effects that are associated with all members of the fluoroquinolone antibacterial class. Among these, tendon problems and exacerbation of the symptoms of the neurological disorder myasthenia gravis are the subject of "black box" warnings in the United States.

The overall rate of adverse events in patients treated with fluoroquinolones is roughly similar to that seen in patients treated with other antibiotic classes. A U.S. Centers for Disease Control and Prevention study found patients treated with fluoroquinolones experienced adverse events severe enough to lead to an emergency department visit more frequently than those treated with cephalosporins or macrolides, but less frequently than those treated with penicillins, clindamycin, sulfonamides, or vancomycin.

Fluoroquinolones prolong the heart's QT interval by blocking voltage-gated potassium channels. Prolongation of the QT interval can lead to torsades de pointes, a life-threatening arrhythmia, but in practice this appears relatively uncommon in part because the most widely prescribed fluoroquinolones (ciprofloxacin and levofloxacin) only minimally prolong the QT interval.

"Clostridium difficile" colitis may occur in connection with the use of any antibacterial drug, especially those with a broad spectrum of activity such as clindamycin, cephalosporins, and fluoroquinolones. Fluoroquinoline treatment is associated with risk that is similar to or less than that associated with broad spectrum cephalosporins. Fluoroquinoline administration may be associated with the acquisition and outgrowth of a particularly virulent "Clostridium" strain.

Events that may occur in acute overdose are rare, and include renal failure and seizure. Susceptible groups of patients, such as children and the elderly, are at greater risk of adverse reactions during therapeutic use.

In 2017 the FDA included the following important warning:

"The U.S. Food and Drug Administration (FDA) has required the drug labels and Medication Guides for all fluoroquinolone antibacterial drugs be updated to better describe the serious side effect of peripheral neuropathy. This serious nerve damage potentially caused by fluoroquinolones (see Table for a list) may occur soon after these drugs are taken and may be permanent.

The risk of peripheral neuropathy occurs only with fluoroquinolones that are taken by mouth or by injection. Approved fluoroquinolone drugs include levofloxacin (Levaquin), ciprofloxacin (Cipro), moxifloxacin (Avelox), norfloxacin (Noroxin), ofloxacin (Floxin), and gemifloxacin (Factive). The topical formulations of fluoroquinolones, applied to the ears or eyes, are not known to be associated with this risk.

If a patient develops symptoms of peripheral neuropathy, the fluoroquinolone should be stopped, and the patient should be switched to another, non-fluoroquinolone antibacterial drug, unless the benefit of continued treatment with a fluoroquinolone outweighs the risk. Peripheral neuropathy is a nerve disorder occurring in the arms or legs. Symptoms include pain, burning, tingling, numbness, weakness, or a change in sensation to light touch, pain or temperature, or the sense of body position. It can occur at any time during treatment with fluoroquinolones and can last for months to years after the drug is stopped or be permanent. Patients using fluoroquinolones who develop any symptoms of peripheral neuropathy should tell their health care professionals right away.

FDA will continue to evaluate the safety of drugs in the fluoroquinolone class and will communicate with the public again if additional information becomes available. "

In most countries, fluoroquinolones are approved for use in children only under narrowly-defined circumstances, owing in part to the observation of high rates of musculoskeletal adverse events in fluoroquinolone treated juvenile animals. In the UK, the prescribing indications for fluoroquinolones for children are severely restricted. Only inhalant anthrax and pseudomonal infections in cystic fibrosis infections are licensed indications in the UK due to ongoing safety concerns. In a study comparing the safety and efficacy of levofloxacin to that of azithromycin or ceftriaxone in 712 children with community-acquired pneumonia, serious adverse events were experienced by 6% of those treated with levofloxacin and 4% of those treated with comparator antibiotics. Most of these were considered by the treating physician to be unrelated or doubtfully related to the study drug. Two deaths were observed in the levofloxacin group, neither of which was thought to be treatment-related. Spontaneous reports to the U.S. FDA Adverse Effects Reporting System at the time of the 20 September 2011 U.S. FDA Pediatric Drugs Advisory Committee included musculoskeletal events (39, including 5 cases of tendon rupture) and central nervous system events (19, including 5 cases of seizures) as the most common spontaneous reports between April 2005 and March 2008. An estimated 130,000 pediatric prescriptions for levofloxacin were filled on behalf of 112,000 pediatric patients during that period.

Meta-analyses conclude that fluoroquinolones pose little or no additional risk to children compared to other antibiotic classes.

Fluoroquinolines use in children may be appropriate when the infection is caused by multidrug-resistant bacteria, or when alternative treatment options require parenteral administration and oral therapy is preferred.

There are several risk factors that increase the likelihood of developing bacteremia from any type of bacteria. These include:

- HIV infection

- Diabetes Mellitus

- Chronic hemodialysis

- Solid organ transplant

- Stem cell transplant

- Treatment with glucocorticoids

- Liver failure

Gram negative bacterial species are responsible for approximately 24% of all cases of healthcare-associated bacteremia and 45% of all cases of community-acquired bacteremia. In general, gram negative bacteria enter the bloodstream from infections in the respiratory tract, genitourinary tract, gastrointestinal tract, or hepatobiliary system. Gram-negative bacteremia occurs more frequently in elderly populations (65 years or older) and is associated with higher morbidity and mortality in this population.

"E.coli" is the most common cause of community-acquired bacteremia accounting for approximately 75% of cases. E.coli bacteremia is usually the result of a urinary tract infection. Other organisms that can cause community-acquired bacteremia include "pseudomonas aeruginosa", "klebsiella pneumoniae", and "proteus mirabilis". "Salmonella" infection, despite mainly only resulting in gastroenteritis in the developed world, is a common cause of bacteremia in Africa. It principally affects children who lack antibodies to Salmonella and HIV+ patients of all ages.

Among healthcare-associated cases of bacteremia, gram negative organisms are an important cause of bacteremia in the ICU. Catheters in the veins, arteries, or urinary tract can all create a way for gram negative bacteria to enter the bloodstream. Surgical procedures of the genitourinary tract, intestinal tract, or hepatobiliary tract can also lead to gram negative bacteremia. "Pseudomonas" and "enterobacter" species are the most important causes of gram negative bacteremia in the ICU.

Strains of hVISA and VISA do not have resistant genes found in "Enterococcus" and the proposed mechanisms of resistance include the sequential mutations resulting in a thicker cell wall and the synthesis of excess amounts of D-ala-D-ala residues. VRSA strain acquired the vancomycin resistance gene cluster "vanA" from VRE.

Six different types of vancomycin resistance are shown by enterococcus: Van-A, Van-B, Van-C, Van-D, Van-E and Van-G. The significance is that Van-A VRE is resistant to both vancomycin and teicoplanin, Van-B VRE is resistant to vancomycin but susceptible to teicoplanin, and Van-C is only partly resistant to vancomycin

The mechanism of resistance to vancomycin found in enterococcus involves the alteration of the peptidoglycan synthesis pathway. The D-alanyl-D-lactate variation results in the loss of one hydrogen-bonding interaction (four, as opposed to five for D-alanyl-D-alanine) being possible between vancomycin and the peptide. The D-alanyl-D-serine variation causes a six-fold loss of affinity between vancomycin and the peptide, likely due to steric hindrance.

For isolates with a Vancomycin MIC , an alternative to Vancomycin should be used. The approach is to treat with at least one agent to which VISA/VRSA is known to be susceptible by "in vitro" testing. The agents that are used include daptomycin, linezolid, telavancin, ceftaroline, quinupristin–dalfopristin. For people with MRSA bacteremia in the setting of vancomycin failure the IDSA recommends high-dose daptomycin, if the isolate is susceptible, in combination with another agent (e.g. gentamicin, rifampin, linezolid, TMP-SMX, or a beta-lactam antibiotic).

Common multidrug-resistant organisms are usually bacteria:

- Vancomycin-Resistant Enterococci (VRE)

- Methicillin-Resistant "Staphylococcus" "aureus" (MRSA)

- Extended-spectrum β-lactamase (ESBLs) producing Gram-negative bacteria

- "Klebsiella" "pneumoniae" carbapenemase (KPC) producing Gram-negatives

- Multidrug-Resistant gram negative rods (MDR GNR) MDRGN bacteria such as "Enterobacter species", "E.coli", "Klebsiella pneumoniae", "Acinetobacter baumannii", "Pseudomonas aeruginosa"

A group of gram-positive and gram-negative bacteria of particular recent importance have been dubbed as the ESKAPE group ("Enterococcus faecium", "Staphylococcus aureus", "Klebsiella pneumoniae", "Acinetobacter baumannii", "Pseudomonas aeruginosa" and Enterobacter species).

- Multi-drug-resistant tuberculosis

The Centers for Disease Control and Prevention (CDC) estimated roughly 1.7 million hospital-associated infections, from all types of bacteria combined, cause or contribute to 99,000 deaths each year. Other estimates indicate 10%, or 2 million, patients a year become infected, with the annual cost ranging from $4.5 billion to $11 billion. In the USA, the most frequent type of infection hospitalwide is urinary tract infection (36%), followed by surgical site infection (20%), and bloodstream infection and pneumonia (both 11%).

In Belgium the prevalence of nosocomial infections is about 6.2%. Annually about 125,500 patients become infected by a nosocomial infection, resulting in almost 3000 deaths. The extra costs for the health insurance are estimated to be approximately €400 million/year.

The prime example for MDR against antiparasitic drugs is malaria. "Plasmodium vivax" has become chloroquine and sulfadoxine-pyrimethamine resistant a few decades ago, and as of 2012 artemisinin-resistant Plasmodium falciparum has emerged in western Cambodia and western Thailand.

"Toxoplasma gondii" can also become resistant to artemisinin, as well as atovaquone and sulfadiazine, but is not usually MDR

Antihelminthic resistance is mainly reported in the veterinary literature, for example in connection with the practice of livestock drenching and has been recent focus of FDA regulation.

The Gonorrhea bacterium Neisseria gonorrhoeae has developed antibiotic resistance to many antibiotics.

The bacteria was first identified in 1879, although some Biblical scholars believe that references to the disease can be found as early as Parshat Metzora of the Old Testament.

In the 1940s effective treatment with penicillin became available, but by the 1970s resistant strains predominated. Resistance to penicillin has developed through two mechanisms: chromasomally mediated resistance (CMRNG) and penicillinase-mediated resistance (PPNG). CMRNG involves step wise mutation of penA, which codes for the penicillin-binding protein (PBP-2); mtr, which encodes an efflux pump that removes penicillin from the cell; and penB, which encodes the bacterial cell wall porins. PPNG involves the acquisition of a plasmid-borne beta-lactamase. "N. gonorrheoea" has a high affinity for horizontal gene transfer, and as a result, the existence of any strain resistant to a given drug could spread easily across strains.

Fluoroquinolones were a useful next-line treatment until resistance was achieved through efflux pumps and mutations to the gyrA gene, which encodes DNA gyrase. Third-generation cephalosporins have been used to treat gonorrhoea since 2007, but resistant strains have emerged. As of 2010, the recommended treatment is a single 250 mg intramuscular injection of ceftriaxone, sometimes in combination with azithromycin or doxycycline. However, certain strains of "N. gonorrhoeae" can be resistant to antibiotics usually that are normally used to treat it. These include: cefixime (an oral cephalosporin), ceftriaxone (an injectable cephalosporin), azithromycin, aminoglycosides, and tetracycline.

HCAP is a condition in patients who can come from the community, but have frequent contact with the healthcare environment. Historically, the etiology and prognosis of nursing home pneumonia appeared to differ from other types of community acquired pneumonia, with studies reporting a worse prognosis and higher incidence of multi drug resistant organisms as etiology agents. The definition criteria which has been used is the same as the one which has been previously used to identify bloodstream healthcare associated infections.

HCAP is no longer recognized as a clinically independent entity. This is due to increasing evidence from a growing number of studies that many patients defined as having HCAP are not at high risk for MDR pathogens. As a result, 2016 IDSA guidelines removed consideration of HCAP as a separate clinical entity.

Studies have found that men have a higher risk of getting XDR-TB than women. One study showed that the male to female ratio was more than threefold, with statistical relevance (P<0.05) Studies done on the effect of age and XDR-TB have revealed that individuals who are 65 and up are less likely to get XDR-TB. A study in Japan found that XDR-TB patients are more likely to be younger.

TB is one of the most common infections in people living with HIV/AIDS. In places where XDR-TB is most common, people living with HIV are at greater risk of becoming infected with XDR-TB, compared with people without HIV, because of their weakened immunity. If there are a lot of HIV-infected people in these places, then there will be a strong link between XDR-TB and HIV. Fortunately, in most of the places with high rates of HIV, XDR-TB is not yet widespread. For this reason, the majority of people with HIV who develop TB will have drug-susceptible or ordinary TB, and can be treated with standard first-line anti-TB drugs. For those with HIV infection, treatment with antiretroviral drugs will likely reduce the risk of becoming infected with XDR-TB, just as it does with ordinary TB.

A research study titled "TB Prevalence Survey and Evaluation of Access to TB Care in HIV-Infected and Uninfected TB Patients in Asembo and Gem, Western Kenya", says that HIV/AIDS is fueling large increases in TB incidence in Africa, and a large proportion of cases are not diagnosed.

Antibiotics can cause severe reactions and add significantly to the cost of care. In the United States, antibiotics and anti-infectives are the leading cause of adverse effect from drugs. In a study of 32 States in 2011, antibiotics and anti-infectives accounted for nearly 24 percent of ADEs that were present on admission, and 28 percent of those that occurred during a hospital stay.

Prescribing by an infectious disease specialist compared with prescribing by a non-infectious disease specialist decreases antibiotic consumption and reduces costs.

In some studies, the bacteria found in patients with HCAP were more similar to HAP than to CAP; compared to CAP, they could have higher rates of "Staphylococcus aureus" ("S. aureus") and "Pseudomonas aeruginosa", and less "Streptococcus pneumoniae" and "Haemophilus influenzae". In European and Asian studies, the etiology of HCAP was similar to that of CAP, and rates of multi drug resistant pathogens such as "Staphylococcus aureus" and "Pseudomonas aeruginosa" were not as high as seen in North American studies. It is well known that nursing home residents have high rates of colonization with MRSA. However, not all studies have found high rates of S. aureus and gram-negative bacteria. One factor responsible for these differences is the reliance on sputum samples and the strictness of the criteria to discriminate

between colonising or disease-causing bacteria. Moreover, sputum samples might be less frequently obtained in the elderly.Aspiration (both of microscopic drops and macroscopic amounts of nose and throat secretions) is thought to be the most important cause of HCAP. Dental plaque might also be a reservoir for bacteria in HCAP.

Bacteria have been the most commonly isolated pathogens, although viral and fungal pathogens are potentially found in immunocompromised hosts (patients on chronic immunosuppressed medications, solid organ and bone marrow transplant recipients). In general, the distribution of microbial pathogens varies among institutions, partly because of differences in patient population and local patterns of anti microbial resistance in hospitals and critical care units' Common bacterial pathogens include aerobic GNB, such as "Pseudomonas aeruginosa", "Acinetobacter baumanii", "Klebsiella pneumoniae", "Escherichia coli" as well as gram-positive organisms such as "Staphylococcus aureus". In patients with an early onset pneumonia (within 5 days of hospitalization), they are usually due to anti microbial-sensitive bacteria such as "Enterobacter" spp, "E. coli", "Klebsiella" spp, "Proteus" spp, "Serratia mare scans", community pathogens such as "Streptococcus pneumoniae, Haemophilus influenzae", and methicillin-sensitive "S. aureus" should also be considered.

Pneumonia that starts in the hospital tends to be more serious than other lung infections because: people in the hospital are often very sick and cannot fight off germs. The types of germs present Ina hospital are often more dangerous and more resistant to treatment than those outside in the community. Pneumonia occurs more often in people who are using a respirator. This machine helps them breathe. Hospital-acquired pneumonia can also be spread by health care workers, who can pass germs from their hands or clothes from one person to another. This is why hand-washing, wearing grows, and using other safety measures is so important in the hospital.

Though antibiotics are required to treat severe bacterial infections, misuse has contributed to a rise in bacterial resistance. The overuse of fluoroquinolone and other antibiotics fuels antibiotic resistance in bacteria, which can inhibit the treatment of antibiotic-resistant infections. Their excessive use in children with otitis media has given rise to a breed of bacteria resistant to antibiotics entirely.

Widespread use of fluoroquinolones as a first-line antibiotic has led to decreased antibiotic sensitivity, with negative implications for serious bacterial infections such as those associated with cystic fibrosis, where quinolones are among the few viable antibiotics.